HomeMy WebLinkAbout20063341.tiff NOTICE OF
FINAL READING OF ORDINANCE 2006-7
Pursuant to the Weld County Home Rule Charter, Ordinance Number 2006-7 was introduced on
first reading on September 11, 2006, and a public hearing and second reading was held on
October 2, 2006, and continued to October 9, 2006, then to October 23, 2006. A public hearing
and final reading was completed on November 13, 2006, with no change being made to the text
of said Ordinance, and on motion duly made and seconded, was adopted. Effective date of said
Ordinance is listed below.
Any backup material, exhibits or information previously submitted to the Board of County
Commissioners concerning this matter may be examined in the office of the Clerk to the Board of
County Commissioners, located in the Weld County Centennial Center, 915 10th Street, Third
Floor, Greeley, Colorado, between the hours of 8:00 a.m. and 5:00 p.m., Monday thru Friday, or
may be accessed through the Weld County Web Page (www.co.weld.co.us). E-Mail messages
sent to an individual Commissioner may not be included in the case file. To ensure inclusion of
your E-Mail correspondence into the case file, please send a copy to
egesick@co.weld.co.us.
ORDINANCE NO. 2006-7
ORDINANCE TITLE: IN THE MATTER OF REPEALING AND REENACTING, WITH
AMENDMENTS, CHAPTER 8 PUBLIC WORKS, OF THE WELD COUNTY CODE
EFFECTIVE DATE: November 27, 2006
BOARD OF COUNTY COMMISSIONERS
WELD COUNTY, COLORADO
DATED: November 17, 2006
PUBLISHED: November 22, 2006 in the Fort Lupton Press
O r D aob4
2006-3341
NOTICEOF PROOF OF PUBLICATION
FINAL READING OF
ORDINANCE FORT LUPTON
N OF
Pursuant to the Weld County STATE OF COLORADO
Home Rule Charter, Ordinance
Number 2006-7 was introduced on COUNTY OF WELD SS.
first reading on September 11,
2006, and a public hearing and
second reading was held on
October 2,2006,and continued to
October 9, 2006, then to October
23, 2006. A public hearing and I, Karen Lambert, do solemnly swear that I
final reading was completed on
November 13,2006, with no am the Publisher of the Fort Lupton Press;
change being made to the text of said Ordinance, and on motion that the same is a weekly newspaper printed
duly made and seconded, was
adopted. Effective date of said and published in the County of Weld, State
Ordinance is listed below. of Colorado, and has a general circulation
Any backup material, exhibits or
information previously submitted therein; that said newspaper has been
to the Board of County
Commissioners concerning this published continuously and uninterruptedly
matter may be examined in the
office of the Clerk to the Board of in said county of Weld for a period of more
County Commissioners,located in
the Weld County Centennial than fifty-two consecutive weeks prior to the
Center. 915 le 10th Street,ob Third firstpublication of the annexed legal notice
Floor,Greeley,Colorado,between g
the . Monday n o 8:00 a.m, and 5:an
be thru Friday or may or advertisement; that said newspaper has
be accessed through theWeld
County Web Page been admitted to the United States mails as
o.weld.co.us). E-Mail
messag
es sent to an individual second-class matter under the provisions of
Commissioner
in themay
filt be
e. To the act of March 3, 1879, or any
ensure inclusion of your E-Mall correspondence Into the case amendments thereof, and that said
file, please send a copy to
egesick@co.weld.co.us. newspaper is a weekly newspaper duly
ORDINANCE NO.2006-7 qualified for publishing legal notices and
ORDINANCE TITLE: IN THE advertisements within the meaning of the
MATTER OF REPEALING WITH REENACTING, laws of the State of Colorado. That the
AMENDMENTS, CHAPTER 8
PUBLIC WORKS, OF THE WELD annexed legal notice or advertisement was
COUNTY CODE published in the regular and entire issue of
200E`TIVE°ATE:November 27, every number of said weekly newspaper for
BOARD OF COUNTY the period of 1 consecutive insertion(s); and
CO
WELD COUONTY,COLORADO that the first publication of said notice w as
DATED:November 17,2006 in the issue of newspaper, dated 22nd day
PUBLISHED: Novrt Luptonember 22, 2006 of November, 2006, and the last on the 22nd
in ss
day of November, 2006.
PuPu lis scn a sworn a ore me, this the
17th day of November, 2006.
Q -9 RY ,0
• .C-4)C'- F.tary •ue ic.
Nom. POSOt
'QC/44 0Fat.:
/SSION EX4,
CASE NO.401951 key 35402
NOTICE OF
SECOND READING OF ORDINANCE
Pursuant to the Weld County Home Rule Charter, Ordinance Number 2006-7 was introduced on
first reading on September 11, 2006, and a public hearing and second reading was held on
October 9, 2006, and continued to October 23, 2006, with changes being made as listed below.
A public hearing and third reading is scheduled to be held in the Chambers of the Board, First Floor
Hearing Room, 915 10th Street, Greeley, Colorado 80631 on November 13, 2006. All persons in
any manner interested in the next reading of said Ordinance are requested to attend and may be
heard.
Please contact the Clerk to the Board's Office at phone (970) 336-7215, Extension 4225, or fax
(970)352-0242, prior to the day of the hearing if, as a result of a disability, you require reasonable
accommodations in order to participate in this hearing.
Any backup material, exhibits or information previously submitted to the Board of County
Commissioners concerning this matter may be examined in the office of the Clerk to the Board of
County Commissioners, located in the Weld County Centennial Center, 915 10th Street, Third
Floor, Greeley, Colorado, between the hours of 8:00 a.m. and 5:00 p.m., Monday thru Friday, or
may be accessed through the Weld County Web Page (www.co.weld.co.us). E-Mail messages
sent to an individual Commissioner may not be included in the case file. To ensure inclusion of
your E-Mail correspondence into the case file, please send a copy to
egesick@co.weld.co.us.
ORDINANCE NO. 2006-7
ORDINANCE TITLE: IN THE MATTER OF REPEALING AND REENACTING, WITH
AMENDMENTS, CHAPTER 8 PUBLIC WORKS, OF THE WELD COUNTY CODE
DATE OF NEXT READING: November 13, 2006, at 9:00 a.m.
BOARD OF COUNTY COMMISSIONERS
WELD COUNTY, COLORADO
DATED: September 27, 2006
PUBLISHED: November 1, 2006, in the Fort Lupton Press
* * * * * * * * * * * * * *
CHANGES MADE TO CODE ORDINANCE #2006-7 ON SECOND READING
Amend Section 8-11-30.A to read as follows:
16. Add the following to Section 4.3.1 Channelization.
"It shall be the policy of Weld County to review proposed channel designs on a case-by-
case basis. Proposed modifications to natural channels shall be approved only if the
proposed work causes no injury to water rights and is not in violation of State or Federal
law."
17. Add the following to Section 4.5 Detention and Retention Storage:
"The Policy of Weld County shall be to require regional and/or on-site detention for all future
developments. Temporary or interim detention/ retention may be required if the
downstream regional facilities have not yet been constructed per the applicable Master
Plan. Stormwater retention facilities are normally not allowed in Weld County, but will be
considered for special circumstances. It is Weld County policy to require detention of runoff
from the 100-year storm falling on the developed site and release of the detained water at
the rate of the runoff of the 5-year storm falling on the undeveloped site. Detention
releases based on soil types are not approved for Weld County. Proposed developments
must provide for safe conveyance of off-site flows through the proposed development site.
Off-site flows may be routed through or around the proposed detention facilities. Positive
drainage must be provided. Weld County will not approve any detention or retention pond
that does not drain in less than 72 hours,or causes injury to water rights, or is in violation
of State or Federal law."
Amend Section 8-11-40.C to read as follows:
10. Amend Section 3.3.4 Retention Facilities to read:
"When a retention basin is proposed as a temporary solution to an evolving drainage
problem, Weld County recommends that it be sized to capture, as a minimum, the runoff
equal to 1.5 times the 24-hour, 100-year storm plus 1-foot freeboard. The facility also has
to be situated and designed so that when it overlaps, no human-occupied or critical
structures (e.g., electrical vaults)will be flooded, and no catastrophic failure at the facility
(e.g., loss of dam embankment)will occur. It is also recommended that retention facilities
be as shallow as feasible to encourage infiltration and other losses of the captured urban
runoff. When a trickle outflow can be accepted downstream, one shall be provided and
sized in accordance with the locally approved release rates,preferably capable of emptying
the full volume in 10 to 14 days. Weld County will not approve any detention or retention
pond that does not drain in less than 72 hours, or causes injury to water rights, or is in
violation of State or Federal law."
Amend Section 8-11-50.F to read as follows:
18. Amend the first paragraph of Section 5.3 Outlet Protection to read:
"To protect adjacent downstream properties from erosion due to concentrated flows, a
stable outlet or channel is necessary. If there is no stable outlet, one may have to be
constructed. In lieu of constructing a temporary or permanent outlet to the storm
drainageway system, temporary total retention of the runoff may be considered on a case-
by-case basis upon acceptance from Weld County. Weld County will not approve any
detention or retention pond that does not drain in less than 72 hours, or causes injury to
water rights,or is in violation of State or Federal law."
19. No change
20. Amend the second paragraph of Section 9.0 Maintenance to read:
"The Professional Engineer preparing the permanent erosion and sediment
control plan shall submit a schedule of planned inspection and instructions
for operations and maintenance for all installed permanent erosion and
sediment control measures. The plan shall include identification and
specifications (size, materials, etcetera) of parts and equipment potentially
needing repair or replacement over the life of the installed measures. A
copy of the inspection schedule and instructions for operations and
maintenance shall be provided to the applicable Homeowners'Association
or Business Park management (or equivalent). Weld County will not
approve any detention or retention pond that does not drain in less than 72
hours, or causes injury to water rights, or is in violation of State or Federal
law."
NOTICE OF of runoff from the 100?year storm PROOF OF PUBLICATION
SECOND READING OF falling on the developed site and
ORDINANCE release of the detained water at FORT LUPTON
the rate of the runoff of the 5 ?
Pursuant to the Weld County year storm falling on the STATE OF COLORADO
Home Rule Charter, Ordinance undeveloped site. Detention
Number 2006-7 was introduced on releases based on soil types are
mast reading on September 11, not approved for Weld County. COUNTY OF WELD SS.
'16, and a public hearing and Proposed developments must
;ond reading was held on provide for safe conveyance of off-
ctober 9,2006,and continued to site flows through the proposed
October 23, 2006, with changes development site. Off-site flows
being made as listed below. A may be routed through or around Karen Lambert do solemnly swear that I
public hearing and third reading is the proposed detention facilities. I, r
scheduled to be held in the Positive drainage must be am the Publisher of the Fort Lupton Press;
Chambers of the Board,First Floor provided. Weld County will not
Hearing Room, 915 10th Street, approve any detention or retention that the same is a weekly newspaper printed
Greeley, Colorado 80631 on pond that does not drain in less
anyNov 13,2006.Ad persons the next
thwater rights,, novd injury tn to and published in the County of Weld, State
any manner, l in the next water rights, or is in violation of
reading of said Ordinance are State o Sectallaw." of Colorado, and has a general circulation
requested to attend and may be Amend Section 8-„-40.C to
heard. read as follows:
10. Amend Section 3.3.4 therein; that said newspaper has been
Please contact the Clerk to the RetentionFacilitentionead: continuously and uninterruptedly
Board's Office at phone(970)336- "When a retention basin is published p y
7215, ion 4225.or fax(970) proposed as a temporary solution in said county of Weld for a period of more
352 0242,0242,prior to the day of the to an evolving drainage problem,
hearing if, as a result of a Weld County that than fifty-two consecutive weeks prior to the
disability,ccom you n reasonable to be sized to capture,uff as a y'
accommodations in ia order to minimum, the- runoff equal-yea to 1.5 firstpublication of the annexed legal notice
participate in this hearing. times the 24-hour, rd. The storm g
plus 1-foot freeboard, The facility that said newspaper has
Any backup material, exhibits or also has to be situated and or advertisement;
information previously submitted designed so that when it overtops, n
to the Board of County no human-o,.cupied or critics, been admitted to the United otates mails as
Commissioners concerning this structures (e.g., electrical vaults) second-class matter under the provisions of
matter may be examined in the will be flooded, and no office of the Clerk to the Board of catastrophic failure at the facility the act of March 3, 1879, or any
Commissioners,located in (e.g., loss of dam embankment)
the Weld County Centennial will occur.It is also recommended amendments thereof, and that said
Center, 915 10th Street, Third that retention facilities be as
Floor,Greeley,Colorado,between shallow as feasible to encourage newspaper is a weekly newspaper duly
the hours of 8:00 am. and 5:00 infiltration and other losses of the
be Monday thr Friday, or may captured ow runoff. When a qualified for publishing legal notices and
be accessed through the Weld trickle outflow can be accepted
County Web Page downstream, one shall be
(www.co.weld.co.us). E-Mail provided and sized in accordance advertisements within the meaning of the
messages sent to an individual with the locally approved release laws of the State of Colorado. That the
Commissioner may not be rates, preferably capable of
included in the case file. To emptying the full volume in 10 to legal notice or advertisement was
ensure inclusion of your E-Mail 14 days. Weld County will not annexed g
correspondence into the case approve any detention or retention published in the regular and entire issue of
file, please send a copy to pond that does not drain in less
ygesick@co.weld.co.us. than 72 hours,or causes injury to
water rights,or is in violation of every number of said weekly newspaper for
DINANCE NO.2006-7 State FSec 8- the period of 1 consecutive insertion(s)•, and
Amend Section ."11-SO.F to ,
ORDINANCE TITLE: IN THE read as follows:
MATTER OF REPEALING AND 18. Amend the first paragraph of that the first publication of said notice w as
AMENDMENTS, CHAPTER read:
REENACTING, WITH
ITH Section 5.3 Outlet Protection to in the issue of newspaper, dated 1st day of
PUBLIC WORKS,OF THE WELD "To protect adjacent downstream 2006, and the last on the 1st day
COUNTY CODE properties from erosion due toNovember,
concentrated flows,a stable outlet of 2006.
DATE OF NEXT READING: or channel is necessary.If there isNovember,
November 13,2006,at 9:00 a.m. no stable outlet, one may have to
be constructed. In lieu of
BOARD OF COUNTY constructing a temporary or
COMMISSIONERS permanent outlet to the storm
WELD COUNTY,COLORADO drainageway system, temporary
total retention
retention of the runoff may be
DATED:October 27,2006 considered on a case-by-case
basis upon acceptance from Weld
PUBLISHED: November 1, 2006, County. Weld County will not
in the Fort Lupton Press approve any detention or retention
pond that does not drain in less
CHANGES MADE TO CODE than 72 hours,or causes injury to
ORDINANCE# ON water rights, or is in violation of
SECOND READING State or Federal law."
19.No change
Amend Section 8-11-30.A to 20. Amend the second paragraph
read as follows: of Section 9.0 Maintenance to
16. Add the following to Section read:
4.3.1 be Channelization: "The Professional Engineer
shall to the policy of Weld preparing the permanent pt erosion
County to igs nposea and sediment ol plan shall
r-
channel designs on a submit a schedule of planned 2
fby-cons u Proposed inspection and instructions for
modifications to natural channels operations and maintenance for all ,.. tcC
shall be approved only if the installed permanent erosion and Publisshef SubscrI a and sworn before me, this the
proposed work causes no injury to sediment control measures. The
water rights and is not in violation plan shall include identification 27th day of October, 2006.
of State or Federal law." and specifications(size,materials,
17. Add the following to Section etcetera) of parts and equipment „_.-..
4.5 Detention and Retention potentially needing repair or
Storage: replacement over the life of the '
"The Policy of Weld County shall installed measures.A copy of the 7/.'6
be to require regional and/or on? inspection schedule and /LT
site detention for all future instructions for operations and ( /,�)/' // j/j/���''
developments. Temporary or maintenance shall be provided to ` /0 rt l� .C1/ `O f C_
,r+gterim detention/retention may be the applicable Homeowners' ( N y'g riubilc. /
wired if the downstream Association or Business Park , , 'l
gional facilities have not yet management(or equivalent).Welb-•
oven constructed per the County will not approve any_"_,
applicable Master Plan. detention or retention pond that `., ',
Stormwater retention facilities are does not drain in less than 72
normally not allowed in Weld hours, or causes injury to water
County, but will be considered for rights,or is in violation of State or _
special circumstances. It is Weld Federal law."
County policy to require detention CASE NO.401951 key 34567
WELD COUNTY
CODE ORDINANCE 2006-7
IN THE MATTER OF REPEALING AND REENACTING, WITH AMENDMENTS, CHAPTER 8
PUBLIC WORKS, OF THE WELD COUNTY CODE
BE IT ORDAINED BY THE BOARD OF COUNTY COMMISSIONERS OF THE COUNTY OF
WELD, STATE OF COLORADO:
WHEREAS, the Board of County Commissioners of the County of Weld, State of Colorado,
pursuant to Colorado statute and the Weld County Home Rule Charter, is vested with the authority
of administering the affairs of Weld County, Colorado, and
WHEREAS, the Board of County Commissioners, on December 28, 2000, adopted Weld County
Code Ordinance 2000-1, enacting a comprehensive Code for the County of Weld, including the
codification of all previously adopted ordinances of a general and permanent nature enacted on
or before said date of adoption, and
WHEREAS, the Weld County Code is in need of revision and clarification with regard to
procedures, terms, and requirements therein.
NOW, THEREFORE, BE IT ORDAINED by the Board of County Commissioners of the County of
Weld, State of Colorado, that certain existing Chapters of the Weld County Code be, and hereby
are, repealed and re-enacted, with amendments, and the various Chapters are revised to add the
following to read as follows.
CHAPTER 8
PUBLIC WORKS
ARTICLE XI
Weld County Storm Drainage Criteria
Division 1
General Provisions
Section 8-11-10. Purpose and authority.
This Weld County Storm Drainage Criteria is adopted in order to provide minimum
standards to preserve and protect the public health, safety, and general welfare in the
unincorporated lands of Weld County, pursuant to authority granted by Part 4 of Article 15 of Title
30, and Article 35 of Title 30, C.R.S.
Section 8-11-20. Adoption of storm drainage standards - short title.
The Denver,Colorado,Urban Drainage and Flood Control District's"Urban Storm Drainage
Criteria Manual," consisting of Volume 1 (June 2001), Volume 2 (June 2001), and Volume 3, Best
Management Practices(September 1999), is hereby adopted by reference, with the amendments
which are set forth herein. The provisions of this Article XI shall be known as the "Weld County
Storm Drainage Criteria." All facilities for storm drainage on properties located within the
unincorporated lands of Weld County,whether public or private,shall be designed and constructed
in accordance with such criteria, unless required otherwise by an applicable master drainage plan
approved by Weld County. A copy of the "Urban Storm Drainage Criteria Manual" shall be kept
on file in the office of the Weld County Clerk to the Board of County Commissioners for inspection
during regular business hours. It may be downloaded by visiting the Urban Drainage and Flood
Control District web site at www.udfcd.org,or ordered by contacting the Urban Drainage and Flood
Control District at 303-455-6277.
Section 8-11-30. Weld County Addendum to the Text of the Urban Storm Drainage Criteria-
Volume 1
A. Chapter 1 - Drainage Policy
1. Amend Section 1.4 Planning to read:
"Storm drainage is a part of the total urban environmental system.
Therefore, storm drainage planning and design must be compatible with
comprehensive regional plans. A master plan for storm drainage should be
developed and maintained in an up-to-date fashion at all times for each
urbanizing drainage watershed in the Denver regionwatersheds in Weld
County. The planning for drainage facilities should be coordinated with
planning for open space and transportation. By coordinating these efforts,
new opportunities may be identified that can assist in the solution of
drainage problems. Natural drainageways should be used for storm runoff
waterways wherever feasible. Major consideration must be given to the
floodplains and open space requirements of the area (White 1945).
Planning and design of stormwater drainage systems should not be based
on the premise that problems can be transferred from one location to
another. Stormwater runoff can be stored in detention aiiJ ictciitivrr
reservoirs. Such storage can reduce the drainage conveyance capacity
required immediately downstream. Acquisition of open space having a
relationship to drainageways will provide areas where storm runoff can
spread out and be stored for slower delivery downstream."
2. Amend Section 1.5 Technical Issues to read:
"Storm drainage planning and design should follow the criteria developed
and presented in this Urban Storm Drainage Criteria Manual (Manual).
Every urban area has two separate and distinct drainage systems, whether
or not they are actually planned and designed. One is the initial system,and
the other is the major system. To provide for orderly urban growth, reduce
costs to future generations and avoid loss of life and major property
damage, both systems must be planned, properly engineered and
maintained. The determination of runoff magnitude should be by the
Rational Formula, the Colorado Urban Hydrograph Procedure (CUHP),
HEC-1, HEC-HMS, or statistical analyses based on an adequate record of
actual measured flood occurrences as set forth in the RUNOFF chapter of
this Manual. Use of streets for urban drainage should fully recognize that
the primary use of streets is for traffic. Streets should not be used as
floodways for initial storm runoff. Urban drainage design should have as an
objective reduction of street repair and maintenance costs to the public.
Irrigation ditches should not be used as outfall points for initial or major
drainage systems, unless such use is shown to be without unreasonable
hazard, as substantiated by thorough hydraulic engineering analysis, and
written approval of the ditch owner(s) is obtained. In addition, irrigation
ditches cannot be relied on for mitigating upstream runoff. Proper design
and construction of stormwater detention and ,ctc,.livrr basins are
necessary to minimize future maintenance and operating costs and to avoid
public nuisances and health hazards. This is particularly important, given
the many detention and retention facilities in..IC Der ivci my kJ'Weld County.
The various governmental agencies within the Denver region have Weld
County has adopted and needs to maintain theirits floodplain management
programs. Floodplain management must encompass comprehensive
criteria designed to encourage,where necessary,the adoption of permanent
measures which will lessen the exposure of life, property and facilities to
flood losses, improve the long-range land management and use of flood-
prone areas, and inhibit, to the maximum extent feasible, unplanned and
economically unjustifiable future development in such areas."
3. Amend Section 1.6 Flood Insurance to read:
"Flood insurance is an integral part of the strategy to manage flood losses.
Thy Der Tye. iygio i should tiicouragy cu itlfluci pa.ticipativir Weld County
continues to participate in the National Flood Insurance Program, set forth
in the National Flood Insurance Act(NFIA) of 1968, as amended."
4. Add the following to Section 2.1 Drainage is a Regional Phenomenon That
Does Not Respect the Boundaries Between Government Jurisdictions or
Between Properties: "Weld County may from time to time enter into
Agreements with adjacent counties to cooperate on regional planning. The
Policy of Weld County shall be to pursue a jurisdictionally unified drainage
effort to assure an integrated drainage system, and to cooperate with other
regional and local planning agencies on drainage matters."
5. Amend Section 3.1.2 Rainfall-Runoff Relationships to read:
"A program should be maintained to collect and analyze rainfall-runoff
relationships in urban areas of tlic Dc11 c icykarWeld County."
6. Amend Section 3.1.4 Library to read:
"The DIst,4AWeld County should acquire and actively maintain a library,
which should be available for use by all governmental agencies, practicing
planners, and engineers. The public should be encouraged to use the
library as part of thy astrict'sWeld County's educational and outreach
programs."
7. Amend Section 3.1.5 Runoff Magnitudes to read:
"Where practical, the magnitude of computed and measured runoff peaks
should be tabulated for Denver regionWeld County streams and gulches so
that comparisons may be readily made between watersheds and erroneous
values may be more easily identified."
8. Amend Section 3.2 Floodplain Data to read:
"The program to delineate flood hazard areas along all waterways in the
region should be maintained. This program should make full use of such
sources as the District's Flood I lazard Area Delineation studies, the FEMA
Flood Insurance Studies, data from the Natural Resources Conservation
Service, the USGS, and floodplain studies by private consulting engineers.
This information should be regularly reviewed and updated to reflect
changes due to urbanization, changed channel conditions, and the
occurrence of extraordinary hydrologic events."
9. Amend Section 3.2.2 Data Inventory to read:
"The information collected should be stored in a Vo.,t.al Dist. t
J,.,os;toryWeld County Department of Public Works file available to all
planners, developers, and engineers."
10. Amend the first sentence of Section 3.2.4 Priority for Data Acquisition to
read:
"The Dist,kAWeld County will establish priorities for acquisition of data
because it is recognized that not all of the data can be collected at one
time."
11. Amend Section 3.3.1 Master Plan to read:
"Drainage design does not lend itself to a piece-meal approach; therefore,
master plans for drainage should be prepared on a priority basis. Such
plans already cover most of the developed major drainageways in the
DistrictWeld County. Additional plans will be developed for areas yet
unplanned. In addition, existing master plans will be updated as needed to
reflect changed conditions that take place over time."
12. Amend Section 4.1 Total Urban System to read:
"Storm drainage is a part of the total urban environmental system.
Therefore, storm drainage planning and design should be compatible with
comprehensive regional plans. Master plans for storm drainage have been
developed and maintained in an up-to-date fashion for most of tl
wok,ol.oJs the Doi.vo. ,o9;.,.Weld County. An effort to complete the
coverage of drainage master plans for yet unplanned areas of the
DistrietWeld County should be continued until full coverage is achieved."
13. Amend Section 4.1.2 Master Plan to read:
"Cash.rut.icipaftya.idcow.tyIIItha Dome,reg;e,.srespoi.0;bl fur last..
planning for urban storm drainage facilities within its boundaries and
environs. The District can help to coordinate efforts. Cooperation betwccn
governmental agencies is needed to solve drainage problems and joint city,
county and District efforts are encouraged. Carrying forward master
planning is best accomplished on a priority-phased basis so that tl ie most
demanding problems, such as areas of rapid urbanization, -nay I,..
addressed at an curly datc:Early work includes the planning of major
drainageways from the point of outfall, proceeding in an upstream direction.
The major drainageways are generally well defined and often dictate the
design of the initial drainage system, including storm sewers, detention
facilities, and water quality systems. Th0 Dishit.tWeld County has
established a suitable format for master plan reports and drawings so that
a uniform planning approach and coordination of efforts can more easily be
made. Master planning should be done in enough detail and with adequate
thoroughness to provide a ready drainage development guide for the future
in a particular watershed. Generalized concepts based on rule-of-thumb
hydrological analyses should not be used as master plans; a more rigorous
analysis is necessary. The Policy of Weld County shall be to enforce and
implement adopted Master Drainage Plans. These Master Drainage Plans
may be amended from time to time in the future."
14. Amend Section 4.1.3, paragraph#2, Planning Process Ingredients to read:
"2. Initial Drainage System Planning. All local and regional planning
must take into consideration the initial drainage system to transport
the runoff from storms expected to occur once every 2 to 10 years.
The planner of an initial system must strive to minimize future
drainage complaints."
15. Amend the second paragraph of Section 4.1.6 Water Quality to read:
"Sanitary sewerage systems that overflow or bypass untreated sewage into
surface streams should not be permitted in H is Deg ivy, 1cyk,.rWeld County.
Existing systems that discharge sewage should be adjusted by their owners
to eliminate this problem."
16. Add the following to Section 4.5 Detention and Retention Storage:
"The Policy of Weld County shall be to require regional and/or on-site
detention for all future developments. Temporary or interim detention/
retention may be required if the downstream regional facilities have not yet
been constructed per the applicable Master Plan. Stormwater retention
facilities are normally not allowed in Weld County, but will be considered for
special circumstances. It is Weld County policy to require detention of
runoff from the 100-year storm falling on the developed site and release of
the detained water at the rate of the runoff of the 5-year storm falling on the
undeveloped site. Detention releases based on soil types are not approved
for Weld County. Proposed developments must provide for safe
conveyance of off-site flows through the proposed development site. Off-
site flows may be routed through or around the proposed detention facilities.
Positive drainage must be provided."
17. Amend Section 4.5.4 Reliance on Non-Flood-Control Reservoirs to read:
"Privately owned non-flood-control reservoirs cannot be used for flood
mitigation purposes in master planning because their perpetuity cannot be
reasonably guaranteed. Publicly owned water storage reservoirs(city,state,
water district, irrigation cot npany,etc.)should be assumed to be full for flood
tllar rr r;ng purposes 0,,d, tl f� �, '. ly tl ie deka,.tik,,, otoragc
spillway crest can be utilized in regard to the determination of downstream
Ruud peak fl.,ws.Jurisdictional dams are classified by the State Engineer as
either low, moderate, or high hazard structures depending on conditions
downstream. Dams are classified as high hazard structures when, in the
event of failure, there is a potential loss of life. Dams presently rated as low
or moderate hazard structures may be changed to high hazard rating if
development occurs within the potential path of flooding due to a dam
breach. In this case, the reservoir owners would be liable for the cost of
upgrading the structure to meet the higher hazard classification.
The Policy of the Weld County shall be to:
1. Restrict upstream development to areas outside of the jurisdictional
dam water surface elevation created by a 100-year storm plus
freeboard.
2. Restrict downstream development to areas outside of the
jurisdictional dam 100-year floodplain. The jurisdictional dam
100-year floodplain is defined as either:
a. The 100-year floodplain downstream of the emergency
spillway assuming the dam is full to the elevation of the
emergency spillway at the beginning of the 100-year storm
and the 100-year storm is routed through the dam and out
the emergency spillway,
OR
b. The path that the basin's 100-year floodplain would form
through the downstream development if the dam were
removed by the owner."
18. Amend Section 4.5.5 Reliance on Embankments to read:
"The detention of floodwaters behind embankments created by railroads,
highways or roadways resulting from hydraulically undersized culverts or
bridges should not be utilized by the drainage engineer for flood peak
mitigation when determining the downstream flood peaks for channel
capacity purposes unless such detention has been covered by a binding
agreement approved by tl Dl0t.;.,tWeld County."
19. Amend Section 5.1 Design Criteria to read:
"Storm drainage planning and design should adhere to the criteria
developed and presented in this Manual maintained by the DistrictWeld
County."
20. Amend Section 5.1.1 Design Criteria to read:
"The design criteria presented herein represent current good engineering
practice, and their use in the Do.o'er'eyiu.Meld County is recommended.
The criteria are not intended to be an ironclad set of rules that the planner
and designer must follow; they are intended to establish guidelines,
standards and methods for sound planning and design. The Weld County
Department of Public Works may grant variances from the design criteria of
this Manual by acceptance of the Final Drainage Report in which the
variance request is well documented."
21. Delete the second paragraph of Section 5.2.1 Design Storm Return Periods:
"There are many developed areas within the Denver urban region that do
not fully conform to the drainage standards projected in this Manual. The
multituJ0 of Ni viper 1s aaay.,;atcd with tl cu a. a3 histvn4,ully provid.,J tl l.,
emphasis required to proceed with development of this Manual. It is
tca.vyn;zed that upyiaduiyti moo Jcvcloped ar..ao tv dui ti to all of tl,..
policies, criteria, and standards contained in this Manual will be difficult, if
not impractical, to obtain, short of complete redevelopment or renewal.
I lowever, flood-proofing techniques can be applied to tl iese areas."
22. Amend Section 5.2.2 Initial Storm Provisions to read:
"The initial storm drainage system, capable of safely handling 2-to 10-year
floods depending on local criteria, is necessary to reduce the frequency of
street flooding and maintenance costs, to provide protection against
regularly recurring damage from storm runoff, to help create an orderly
urban system,and to provide convenience to urban residents. Normally,the
initial drainage system cannot economically carry major runoffs, though the
major drainage system can provide for the initial runoff. A well-planned
major drainage system will reduce or eliminate the need for storm sewer
systems (Jones 1967). Storm sewer systems consisting of underground
pipes are a part of initial storm drainage systems."
23. Amend Section 5.4.1 Use of Streets to read:
"Streets are significant and important in urban drainage, and full use should
be made of streets for storm runoff up to reasonable limits, recognizing that
the primary purpose of streets is for traffic. Reasonable limits of the use of
streets for transportation of storm runoff should be governed by reasonable
design criteria as summarized in Table DP-1 and in the Streets/Inlets/Storm
Sewers chapter of this Manual. Urban drainage design should have as
objectives reduction of street repair, maintenance costs, nuisance to the
public, and disruption of traffic flow.
When maximum allowed encroachment is present, the storm sewer system
design based on the initial storm should commence. Development of a
major drainage system that can often drain the initial runoff from the streets
is encouraged, thus making the point at which the storm sewer system
should commence further downstream. Initial and major drainage planning
should go hand-in-hand.
While it is the intent of this policy to have major storm runoff removed from
public streets at frequent and regular intervals and routed into major
drainageways, it is recognized that water will often tend to follow streets and
roadways and that streets and roadways often may be aligned so they will
provide a specific runoff conveyance function. Planning and design
objectives for the major drainage system with regard to public streets should
be based upon following the limiting criteria summarized in Table DP-2 and
in the Streets/Inlets/Storm Sewers chapter of this Manual.
The allowable flow across a street should be within the criteria presented in
Table DP-3 and in the Streets/Inlets/Storm Sewers chapter of this Manual.
An arterial street crossing will generally require that a storm sewer system
be commenced, unless the topography is such that day-lighted inlet culverts
or other suitable means can transport the initial storm runoff under the
arterial street or water can be routed to a major drainage facility. Bubblers
(inverted siphons which convey flows beneath roadways) are not
encouraged in tho Deriver regiunWeld County because of possible plugging
with sediment and difficulty in maintaining them. Collector streets should
have cross pans only at infrequent locations as specified by the governing
agency and in accordance with good traffic engineering practices. The local
street criteria for overtopping also apply to any private access road that
serves commercial areas or more than one residence, for emergency
access and safety reasons."
24. Add the following to Section 5.5 Irrigation Ditches: "It is the policy of Weld
County to prohibit the discharge of stormwater runoff from developed areas
into irrigation ditches and facilities, except as required by water rights or
where such discharges are in conformance with approved Master Drainage
plans. Further, wherever new development will alter patterns of drainage
into irrigation ditches by increasing flow rates or volumes, or will change the
historic concentration points of runoff, the County shall require each new
development to obtain written consent of the appropriate ditch company
before approving the drainage design and development."
25. Amend Section 5.5.1 Use of Ditches to read:
"The irrigation ditches coursing through urban areas are laid out on flat
slopes and with limited carrying capacity. Based on experience and
hydraulic calculations, irrigation ditches cannot, as a general rule, be used
as an outfall point for the initial storm drainage system because of physical
limitations. Exceptions to the rule can occur when the capacity of the
irrigation ditch is adequate to carry the normal ditch flow plus the initial storm
runoff with adequate freeboard to avoid creating a hazard to those below the
ditch. Written approval must be obtained from the ditch owner stating that
the owner understands the physical and legal (i.e., liability) consequences
of accepting said runoff. If there is a question about the use of irrigation
ditches as outfalls for initial storm runoff, there is no question about their
unsuitability as an outfall for the major storm runoff. Without major
reworking of irrigation ditches to provide major carrying capacity without
undue hazard to those downstream or below the ditch, the ditches are
almost always totally inadequate for such a use and should not be used as
an outfall. Moreover, because ditches are normally privately owned, one
cannot assume the perpetual existence or function of a ditch. Land
planners and engineers with a proposed development downhill from a ditch
should shall plan for pre-ditch drainage conditions as well as continued ditch
seepage. For new development, it shall be the policy of Weld County to
prohibit undetained discharges to roadside ditches located in the County
right-of-way. In the event a proposed development wishes to design
stormwater discharge to a County right-of-way,the developer,at the request
of the County, shall have the requirement to design and construct drainage
improvements to the right-of-way at the developers' own expense. Such
improvements shall include, but not be limited to: detention ponds, armored
channels, culverts, and other drainage facilities. Cost-sharing of such
needed improvements may be borne by adjacent developments, such cost
sharing to be negotiated by the developer. Weld County may require written
agreements and construction bonding of such offsite drainage
improvements."
26. Amend Section 5.5.3 Conformance With Master Plan to read:
"Use of irrigation ditches for collection and transport of either initial or major
storm runoff should be prohibited unless specifically provided in a ast.;ct's
master planthe Weld County master plans,or approved byth0 ast.i,-tWeld
County and the ditch owner."
27. Amend Section 5.6 Detention and Retention Facilities Maintenance to read:
"The significant cost of handling stormwater runoff, coupled with the social
benefits to be derived from proper storm drainage facilities, points towards
the use of detention and retention basins for storage of stormwater runoff
in th0 Dcnve. •ey;v;Weld County. Maintenance provisions must be
arranged. Maintenance of detention or retention facilities includes the
removal of debris, excessive vegetation from the embankment, and
sediment. Without maintenance, a detention/retention facility will become
an unsightly social liability and eventually become ineffective."
28. Amend Section 6.1 Purpose to read:
"Va.ot,s govonnwental agci!GIcs wt1, , the li,nvu iegien sl... lJ 6 a; tLe
fluodplain n'al taveiine&it pioguams. Floodplain management includes
comprehensive criteria designed to encourage, where necessary, the
adoption of permanent state or local measures which will lessen exposure
of property and facilities to flood losses, improve long-range land
management and use of flood-prone areas, and inhibit, to the maximum
extent feasible, unplanned future development in such areas."
29. Amend first sentence of Section 6.2 Goals to read:
"There are two goals in regard to floodplain management: • To reduce the
vulnerability of Denver regionWeld County residents to the danger and
damage of floods."
30. Amend Section 6.3.2 New Development to add the following: "The Policy of
Weld County shall be to outsource engineering review of all CLOMR and
LOMR submittals received with a development application. The developers
shall reimburse the Weld County Department of Public Works for all
outsourced engineering review costs. Upon FEMA approval of a CLOMR
or LOMR, payment of all outsourced engineering review costs is due and
payable to Weld County. Developers are welcome to contract directly with
our outsourced consultant(s)for the preparation of CLOMR's and LOMR's,
if they so desire."
31. Amend Section 7.1 Adoption of Drainage Master Plans to read:
"This Manual and master plans should be adopted and used by all
governmental agencies operating within the DistrictWeld County."
32. Amend Section 7.3 Amendments to read:
"Problems in urban drainage administration encountered by any
governmental agencyanyone should be reviewed by the DistrictWeld County
to determine if equity or public interests indicate a need for drainage policy,
practice, or procedural amendments. The DistrictWeld County should
continually review the needs of the Denver regioncommunity in regard to
urban runoff criteria and should recommend changes as necessary to this
Manual."
33. Add Section 7.5 Drainage Improvements to read:
"Weld County Master Drainage Plans set forth improvements required for
existing and future growth areas. There are areas of Weld County for which
no Master Drainage plans yet exist. Weld County may require a Master
Drainage study in support of proposed development. The policy of Weld
County regarding the design and construction of improvements within the
Master Drainage Plan areas shall be as set forth below, subject to Weld
County budget and appropriation approvals.
1. Weld County shall identify needed design and construction of
improvements as set forth in adopted Master Drainage Plans for
existing and future growth areas.
2. The drainage systems for future development and redevelopment
shall be designed and constructed by the developer(s).
3. The developers shall be responsible for design and construction of
temporary or interim storm drainage systems required due to the
lack of adequate storm drainage facilities downstream of new
development.
4. The developers may be responsible for design and construction of
permanent storm drainage systems required due to the lack of
adequate storm drainage facilities downstream of new
development."
B. Chapter 3 - Planning
1. Amend first paragraph of Section 7.1 Initial Drainage to read:
"Planning and design for urban storm runoff must be considered from the
viewpoint of the regularly expected storm occurrence, which includes the
initial storm and the major storm. The initial(minor)storm has been defined
fi tl a,ea served by tl Dist.k.tby Weld County to have a return frequency
ranging from once in 2 years to once in 10 years of once in tem (10)years
(the 10-year storm)for all uses. The major storm has been defined to have
a return period of 100 years. The objective of major storm runoff planning
and design is to reduce the potential for major damage and loss of life. The
initial drainage system is necessary to reduce inconvenience, frequently
recurring damages, and high street maintenance and to help create an
orderly urban system with significant sociological benefits."
2. Amend second paragraph of Section 9.1 Storm Sewers to read:
"The initial drainage system, including storm sewers, is that portion of the
total drainage system that often receives the most attention from engineers.
It is what the average citizen considers to be the urban drainage system.
It is what directly contributes to the orderly growth of a community by
handling the storm runoff expected to occur once every two to t6.1 not a ten
(10) years (the 10-year storm)for all uses."
3. Amend Section 9.4 System Sizing to read:
"The suggested design return periods to be used by local jurisdictions in the
Delve, reg;on fur stor,',sewer design for all la,idus..0; 2 t. 10-yea.J The
design return period to be used for storm sewer design in Weld County is
the 10-year storm for all land uses. Storm sewers passing flow under
County roads shall have a minimum design capacity for the 10-year storm
and a minimum diameter of 15 inches or equivalent open area. System
sizing design shall adhere to Weld County street inundation criteria of six(6)
inches for the minor storm, and 18 inches for the major storm event. This
is a departure from the policy of recommending different return periods for
different land uses. Experience has shown that it is not practical to vary
storm sewer design by land use because a single system often serves
multiple land uses. Instead, greater attention is necessary to ensure that
the major system is adequate to protect the public and property within all
areas, regardless of land use."
C. Chapter 4 - Rainfall
1. Add the following to Section 1.0 Rainfall: "For proposed Weld County
development drainage design,the Rainfall Depth-Duration-Frequency maps
presented in the USDCM may be utilized only for those areas of Weld
County shown on the Figures in that manual(Figures RA-1 through RA-12).
Drainage designs proposed for locations outside of the areas of Weld
County covered by Figures RA-1 through RA-12 should utilize the
depth-duration-frequency information provided in the
Precipitation-Frequency Atlas of the Western United States, Volume II -
Colorado published by the National Oceanic and Atmospheric Admi nistration
(NOAA). The NOAA Atlas may be accessed at:
http://www.nws.noaa.gov/oh/hdsc/noaaatlas2.htm. Where development is
proposed in larger watersheds,design hydrology should utilize longer storm
durations appropriate for the size of the entire watershed. See Tables RA-1
and RA-3 in the USDCM for storm duration and area adjustments."
D. Chapter 5 - Runoff
1. Add the following to Section 3.3.1 Rainfall: "See Tables RA-1 and RA-2
within the USDCM Rainfall Chapter for 1-hour and 2-hour rainfall area
adjustments and distributions. For locations outside of Weld County,
covered by USDCM Figures RA-1 through RA-12, utilize the
depth-duration-frequency information provided in the
Precipitation-Frequency Atlas of the Western United States, Volume II."
2. Amend Section 5.1 Published Hydrologic Information to read:
"Th.. D;st,;,tWeld County has prepared hydrologic studies for the majority
of the major drainageways within DistrictWeld County boundaries. These
studies contain information regarding peak flow and runoff volume from the
2-year through 100-year storm events for numerous design points within the
watershed. They also contain information regarding watershed and sub-
watershed boundaries, soil types, percentage imperviousness, and rainfall.
The studies are available at the District libraryWeld County Department of
Public Works. When published flow values are available from the
DistrictWeld County for any waterway of interest, these values should be
used for design unless there are compelling reasons to modify the published
values."
E. Chapter 6 - Streets/Inlets/Storm Sewers
1. Amend Section 1.3 Components of Urban Stormwater Collection and
Conveyance Systems to read:
"Urban stormwater collection and conveyance systems within th0 Dist,;.A
Weld County are comprised of three primary components: (1)street gutters
and roadside swales, (2) stormwater inlets, and (3) storm sewers (and
appurtenances like manholes,junctions, etc.). Street gutters and roadside
swales collect runoff from the street (and adjacent areas) and convey the
runoff to a stormwater inlet while maintaining the street's level-of-service."
2. Amend first two paragraphs of Section 2.2 Design Considerations to read:
"Certain design considerations must be taken into account in order to meet
street drainage objectives. The primary design objective is to keep the
spread (encroachment) of stormwater on the street below an acceptable
value for a given return period of flooding. As mentioned previously, when
stormwater collects on the street and flows down the gutter,the top width(or
spread) of the water widens as more stormwater is collected. If left
unchecked, the spread of water would eventually hinder traffic flow and
possibly become hazardous (i.e., reduced skid resistance, hydroplaning,
splash, etc.). Based on these considerations, the DistrictWeld County has
established encroachment (spread) standards for the minor storm event.
These standards %Pun- given in the POLICY &apt., and aicrepeated „t
Table ST-2 fur i unveu ,.,.,are provided in Chapter 3, Planning, Section 9.4
of the Weld County Storm Drainage Criteria.
Standards for the major storm and street cross flows are also required. The
major storm needs to be assessed to determine the potential for flooding
and public safety. Cross flows also need to be regulated for traffic flow and
public safety reasons. The Di0t,i.,tWeld County has established street
inundation standards during the major storm event and allowable cross-
street flow standards. These standards vdt., ,y V.,n i,, the POLICY..Lapty,
and a,e repeated i„ TaLI� ST 3 and Table ST-4 f�, b.,, ,u..,u,,..,�re
provided in Chapter 3, Planning, Section 9.4 of the Weld County Storm
Drainage Criteria. Allowable flow depth is measured vertically from the
gutter flowline at the curb face."
3. Amend second paragraph Section 2.3.1.3 Allowable Gutter Hydraulic
Capacity Weld County to read:
"There are two sets of reduction factors developed for Denver metropolitan
areas (Guo 2000b)and they shall also be utilized for Weld County. One is
for the minor event, and another is for the major event. Figure ST-2 shows
that the reduction factor remains unity (1.0) for a street slope <1.5%, and
then decreases as the street slope increases."
4. Add the following to Section 3.1 Inlet Functions, Types and Appropriate
Applications: "The standard inlets permitted for use in Weld County streets
are:
INLET TYPE PERMITTED USE
Curb Opening Inlet Type R All street types with 6" vertical curb
Grated Inlet Type C All streets with a roadside ditch or swale
Grated Inlet Type 13 Alleys or private drives with a valley
gutter
Combination Inlet Type 13 All street types with 6" vertical curb
5. Add the following to Section 3.3.6 Inlet Clogging: "To account for effects
which decrease the capacity of the various types of inlets, such as debris
plugging, pavement overlaying, and variations in design assumptions, the
theoretical capacity calculated for the inlets is to be reduced by the factors
presented below for the standard inlets permitted for use in Weld County.
WELD COUNTY
ALLOWABLE INLET CAPACITY
CONDITION INLET TYPE PERCENT OF
THEORETICAL
CAPACITY ALLOWED
Sump or CDOT Type R
Continuous Grade
5' length 88
10' length 92
15' length 95
Continuous Grade Combination Type 13 66
Sump Grated Type C 50
Grated Type 13 50
Sump Combination Type 13 65
6. Amend the first paragraph of Section 3.4.2 Design Considerations to read:
"The primary design consideration for the location and spacing of inlets on
continuous grades is the spread limitation. This was addressed in Section
2.2. Table ST-2 list paven,e,rt-ei au-ad flirt,ft stand&Jo for minor sty, ea
the Donne, lot opofitan area."
7. Amend the third paragraph Section 4.2 Design Process, Considerations,
and Constraints to read:
"Once a final layout is chosen, storm sewers are sized using hydrologic
techniques (to determine peak flows) and hydraulic analysis (to determine
pipe capacities). This is accomplished by designing the upstream pipes first
and moving downstream. Pipes sizes smaller than 15 inches are not
ii,no,iJod furJtuu,ir,ovvcr0The minimum size storm sewer pipe within
a Public Right-of-Way or Public Drainage Easement shall be 15 inches in
diameter or equivalent open area. Refer to the"Weld County Development
Standards and Specifications Governing the Construction of Public
Improvements", latest edition, for allowable storm sewer pipe materials.
Pipes generally increase in size moving downstream since the drainage
area is increasing. It is not good design practice to decrease the pipe size
moving downstream, even if a steeper slope is encountered that will provide
sufficient capacity with a smaller pipe. The potential for clogging is always
a concern."
8. Add the following to Section 4.4.1 Flow Equations and Storm Sewer Sizing:
"The Manning's roughness coefficient"n" for all storm sewer pipe capacity
Weld County calculations shall be 0.013 regardless of pipe material (ie.
Concrete, PVC, or HDPE) with the exception of corrugated metal pipes
which shall have a coefficient of 0.025."
9. Add the following to Section 4.5 Hydraulic and Energy Grade Line
Calculations: "The hydraulic grade line and energy grade line shall be
calculated for each storm sewer system and included in the Final Drainage
Report. Each storm sewer system shall be profiled on 1:he Final
Construction Drawings and shall include the design flow hydraulic grade line
(HGL). The energy grade line (EGL)for the design flow shall be at least 6
inches below the final finished elevation of the manhole rims and inlet
flowlines."
F. Chapter 7 - Major Drainage
1. Add the following to the first Paragraph of Section 3.2.3.2 Side Slopes: "For
constructed or natural channels with sideslopes steeper than 2:1,
appropriate construction setbacks from the channel edge may be required
to allow potential future channel meandering. Access for maintenance may
require easement."
2. Amend Section 3.2.7 Summary of Preliminary Design Guidance to add the
following note to Table MD-2: "Grass lined open channels conveying < 50
cfs may reduce the minimum 1.0 foot freeboard requirement to the
freeboard required to conveying 1.33 times the 100-year design flow. The
reduced freeboard may only occur if a 1.0-foot minimum freeboard is not
physically or reasonably possible and a variance request is submitted."
3. Delete the first paragraph of Section 3.2.8 Maintenance Eligibility and
replace with the following:
"The requirei..ei,ts bel.,w must be satisfied as of June 2001 f.,. CI .najv.
Jl ail.aye t Lc cI y Lle for District ...ai..t Sol ICU..A,. Note that tl..,
ost.;ct's "Ma,,danance Cligibility Gu;&l,n.,s" may cl,..nyc with time. TL.,
1.6, is J&.c'AkJ-tvivvk up tlIc latcat full ,,.a.,.tc,,ance eligibility c ;Li;a at
the District's Web site (www.UDrCD.org). Maintenance Eligibility
Guidelines as of June 2001 are also provided on the Cdversion of this
Manual.Weld County will only maintain eligible major drainage ways by
special agreement. The requirements below must be satisfied as of
(adoption date)for a major drainage channel to be eligible for Weld County
maintenance. Note that the Weld County "Maintenance Eligibility
Guidelines" may change with time."
4. Amend the first sentence of Section 3.2.8.3 Grass-Lined Channel Design to
read:
"The design for a grass-lined channel must meet the following criteria to be
eligible for DistrictWeld County maintenance:"
5. Amend Section 3.3.4 Maintenance to read:
"A maintenance acce33 rind with a ,,,;,,;.,.um passage w;dll. ..f 12 fcct-bl.all
i.e p.vvidcJ-alvny tl.o cntno lci.ytl. of all ..rajor d.an.aycwaya. TI.e-IwaI
government may require the load to be surfaced with 6 inches of Class 2
roadbase or a 5-inch-thick concrete slab.Weld County and the design
engineer shall work together to provide access to all major drainageways as
determined appropriate at the time of preliminary and final design. Weld
County encourages volunteers to assist Weld County in performing routine
maintenance of all the drainage ways within the County through an Adoption
program and will assist these groups in a variety of ways."
6. Amend the fourth paragraph of Section 3.5 Choice of Channel Lining to
read:
"Manufactured channel linings such as gabions,interlocked concrete blocks,
synthetic linings,etcetera,are not recommended for new developments, but
will be considered by Weld County on a case-by-case basis. As with
concrete- and riprap-lined channels, all of these types are best considered
for helping to solve existing urban flooding problems where right-of-way is
very limited. Manufactured channel linings should be used with caution,and
each type of channel lining must be scrutinized for its merits, applicability,
ability to meet other community needs, long term integrity,and maintenance
needs and costs."
7. Add the following to Section 4.1.5 Trickle and Low-Flow Channels: "Under
drain pipes shall not be used in lieu of trickle channels within Weld County
but will be considered by Weld County on a case-by-case basis."
8. Amend the first paragraph of Section 4.1.7 Water Surface Profile to read:
"Water surface profiles should be computed for all channels,typically fo. tl...
10-fear and 100 yea. cvc..taconveying > 50 cfs within Weld County.
Computation of the water surface profile should include standard backwater
methods, taking into consideration all losses due to changes in velocity,
drops,bridge openings,and other obstructions. Computations should begin
at a known point and extend in an upstream direction for subcritical flow. It
is for this reason that the channel should be designed from a downstream
direction to an upstream direction. It is necessary to show the energy
gradient on all preliminary drawings to help ensure against errors. Whether
or not the energy grade line is shown on the final drawings is an option of
the reviewing agency, although the District encourages this."
9. Add the following as the third paragraph of Section 4.1.7 Water Surface
Profile: "Hydraulic grade lines shall be shown on the Final Construction
Drawing profiles of open channels conveying > 50 cfs within Weld County.
It is not necessary to show energy grade lines on Final Construction
Drawing profiles, but it is encouraged. The energy grade line for the design
flow shall be at, or below, the final finished top of channel bank elevation.
Hydraulic grade lines on Final Construction Drawings are encouraged and
will ease assessment and review of compliance with street inundation
criteria."
10. Amend Section 4.1.8 Maintenance to read:
"Grass-lined channels must be designed with maintainability in mind. See
Section 3.2.8 for the District's Maintenance Eligibility Guidelines,which also
provide guidance for elements of design that permit good maintenance of
these installations. A stable maintenance access road with a minimum
passage width of 12 feet shall be provided along the entire length of all
n.ajurii.ail.aycvvaya. TI.c lan.al yanv.,..lima It may ..,yu;,... tl.c lanai to L.,
surfaced with 6 inches of Class 2 roadbase or a 5-inch-thick concrete
sfabWeld County and the design engineer shall work together to provide
access to all major drainageways as determined appropriate at the time of
preliminary and final design."
11. Amend the fifth paragraph of Section 4.2.2 Design Procedure to read:
"Water surface profiles mustshall be computed, typically fe, the 10- al RI
100-year eventsfor all open channels conveying > 50 cfs within Weld
County. Computation of the water surface profile should utilize standard
backwater methods, taking into consideration all losses due to changes in
velocity, drops, bridge openings, and other obstructions. Computations
begin at a known point and extend in an upstream direction for subcritical
flow. It is for this reason that the channel should be designed from a
downstream direction to an upstream direction. It is necessary to show the
energy gradient on all preliminary drawings to help prevent errors. Whether
or not the energy gradient line is shown on the final drawings is the option
of the reviewing agency but is encouraged by the District."
12. Add the following to the last paragraph of Section 4.2.2 Design Procedure:
"Hydraulic grade lines shall be shown on the final drawing profiles of open
channels conveying >50 cfs within the Weld County. Energy grade lines on
final drawing profiles are encouraged. Hydraulic grade lines on Final
Construction Drawings are encouraged to ease assessment and review of
compliance with street inundation criteria."
13. Amend second paragraph of Section 4.2.3 Life Expectancy and
Maintenance to read:
"A maintenance access road with a minimum passage width of 12 feet shall
tnpiuvk lcJ-ak,ng the e,dtre-I0nyth of all major diainageways. The local
government may require the road to be surfaced with 6 inches of Class 2
,uaJbase ut a VU,tlitato alaL.Weld County and the design
engineer shall work together to provide access to all major drainageways as
determined appropriate at the time of preliminary and final design.
14. Amend the second paragraph of Section 4.3 Concrete-Lined Channels to
read:
"Concrete-lined channels can be used for conveyance of both subcritical
and supercritical flows. In general, however, other types of channels such
as grass-lined channels or channels with wetland bottoms are preferred for
subcritical flows. The use of a concrete-lined channel for subcritical flows
should not be used except in unusual circumstances where a narrow right-
of-way exists. Vegetated channels are normally preferable in the D0nve,
regionWeld County because available thalweg slopes are generally steep
enough.
15. Amend the fourth paragraph of Section 4.3 Concrete-Lined Channels to
read:
"In th0 D.tt,ret ,ogkut(Weld County, all channels carrying supercritical flow
shall be lined with continuously reinforced concrete linings, both
longitudinally and laterally. There shall be no diminution of wetted area
cross sections at bridges or culverts. Adequate freeboard shall be provided
to have a suitable safety margin. Bridges or other structures crossing the
channel must be anchored satisfactorily to withstand the full dynamic load
that might be imposed upon the structure in the event of major trash
plugging."
16. Amend Section 4.3.6 Maintenance to read:
"Concrete channels require periodic maintenance including debris and
sediment removal, patching, joint repair, and other such activities. Their
condition should be periodically monitored, especially to assure that flows
cannot infiltrate beneath the concrete lining. A ,trait tsa a..ccsa vat}
with a ttti,tit!!Um pasaaga of 12 feet shall be pruvideJ 06 1,9 tI iGt
ILttytl, ..,f all majui Jlaulageways. The lu,,al yUV6 ttttmO1tt may require the
lucid to Lc aut laced with C n,cl too of Claaa 2 ,vaJLaao or a 5-n td Al
Ito alaLWeld County and the design engineer shall work together to
provide access to all major drainageways as determined appropriate at the
time of preliminary and final design."
17. Amend Section 4.4.1.3 Wire-Enclosed Rock (Gabions) to read:
"Wire-enclosed rock, or gabions, refers to rocks that are bound together in
a wire basket so that they act as a single unit. The durability of wire-
enclosed rock is generally limited by the life of the galvanized binding wire
that has been found to vary considerably under conditions along waterways.
Water carrying sand or gravel will reduce the service life of the wire
dramatically. Water that rolls or otherwise moves cobbles and large stones
breaks the wire with a hammer-and-anvil action,considerably shortening the
life of the wire. The wire has been found to be susceptible to corrosion by
various chemical agents and is particularly affected by high-sulfate soils.
Wire-enclosed rock installations have been found to attract vandalism, and
flat mattress surfaces seem to be particularly susceptible to having wires cut
and stones removed. For these reasons, thy a0t,i tWeld County
discourages the use of wire-enclosed rock. If the designer chooses to utilize
gabions, they should be placed above the low-flow channel or 2-year water
surface elevation. All flat mattresses must be filled with topsoil and then
covered with a 6-inch layer of topsoil."
18. Amend Section 4.4.7 Maintenance to read:
"A maintenance access road with a minimum passage width of 12 feet shall
by piuv;dokl aluiiy tlrc cntlro Icnytl of all rnajur deaniageWaya. TI chief
government may require the road to be surfaced with 6 inches of Class 2
roadbase or a 5-inch-thick conciete slabWeld County and the design
engineer shall work together to provide access to all major drainageways as
determined appropriate at the time of preliminary and final design.
Requirements for District maintenance eligibility are reviewed in Section
3.2.8 of this chapter. Of particular concern is long-term loss of riprap,
particularly due to the public moving the rock(for smaller sizes). Grout can
deteriorate with time, and this should be monitored, as well. Improper grout
installation creates long-term maintenance problems."
19. Amend Section 4.5 Bioengineered Channels to read:
"Bioengineered channels(see Photographs MD-10 and MD-11)emphasize
the use of vegetative components in combination with structural measures
to stabilize and protect stream banks from erosion. Thu,D;st,k.tWeld County
advocates the integration of bioengineering techniques into drainage
planning, design, and construction when the use of such channels is
consistent with ti ry Dist,k.t'0Weld County's policies concerning flow carrying
capacity,stability,maintenance,and enhancement of the urban environment
and wildlife habitat. The following discussion on bioengineered channels
interfaces closely with Section 4.2, Wetland Bottom Channels, and Section
4.6, Natural Channels; designers are encouraged to read Sections 4.2, 4.5
and 4.6, concurrently. In addition, because bioengineered channels require
some structural assistance to maintain stability in urban settings, the
designer is referred to guidance on drop structures in the HYDRAULIC
STRUCTURES chapter."
20. Amend Section 4.5.3 Bioengineering Resources to read:
"The purpose of this section is to provide the designer with an overview of
bioengineering and basic guidelines for the use of bioengineered channels
on major drainage projects within thy Dish ibtWeld County. There are many
sources of information on bioengineering that the designer should consult
for additional information when planning and designing a bioengineered
channel (Watson, Biedenharn, and Scott 1999; USFISRWG 1998; Riley
1998; and Biedenharn, Elliot, and Watson 1997)."
21. Amend the first two paragraphs of Section 4.5.4 Characteristics of
Bioengineered Channels to read:
"The following characteristics are generally associated with bioengineered
channels:
1. Their design must address the hydrologic changes associated with
urbanization (increased peak discharges, increased runoff volume,
increased base flow, and increased bank-full frequency). These
changes typically necessitate the use of grade control structures. In
the absence of grade control structures, especially in the semi-arid
climate of tho Doi, ei a,0eWeld County, purely bioengineered
channels will normally be subject to bed and bank erosion, channel
instability, and degradation.
2. In addition to grade controls, most bioengineered channels may
require some structural methods to assist the vegetation with
maintaining channel stability. Examples include buried riprap on
toes and outer channel banks(see Figures MD-16, MD-17 and MD-
18)."
22. Add the following to the last paragraph of Section 4.5.4 Characteristics of
Bioengineered Channels: "Weld County is open to review and accept
alternate bioengineering methods that provide protection to toe of bank
slopes (i.e. jacks and lunkers, etcetera)."
23. Amend the first paragraph of Section 4.5.5 Advantages of Bioengineered
Channels to read:
"Public reaction to bioengineered channels is generally favorable, not only
in Inch upuftai.D01 i„c,northern Colorado, but also regionally and nationally.
In contrast to major drainageway stabilization projects that focus on
structural measures, such as concrete-lined or riprap-lined channels,
bioengineered channels:"
24. Amend subparagraph 6 of Section 4.5.5 Advantages of Bioengineered
Channels to read:
"6. Create a living system that rear/will strengthen over time."
25. Add the following to Section 4.5.5 Advantages of Bioengineered Channels:
"8. Are less costly to maintain."
26. Amend the first paragraph of Section 4.5.6 Technical Constraints to read:
"The following constraints aremay be associated with bioengineered
channels:
1. There is only limited experience to rely on for successful design of
urban channels. The majority of the experience with bioengineering
techniques relates to channels in nonurban settings.
2. The semi-arid conditions that characterize BenverWeld County can
be at odds with the need for an adequate water supply for
maintaining the vegetation. Careful species selection that reflects
the site's soils and water availability characteristics is essential.
3. A basic design criterion within thy Dishk.'tWeld County is to
demonstrate channel stability during the major(100-year)storm,due
to public safety and property protection concerns within urban areas.
There is little evidence (locally, regionally, or nationally) as to
whether purely bioengineered channels can withstand 100-year(or
lesser)flood forces.
No Change to remainder of paragraph.
27. Amend the second paragraph of Section 4.5.6 Technical Constraints to
delete the sixth bulleted item: "Large trees can threaten the integrity of
M,ut,tu,al pnutcvtui by IvOt niJaaivn, by tu.Nliny al Jan.uyn.y El 1‘...
NiutoasEui I Wv K0, by tuppin ig and di1ctli,'y flow ito au adjavc.it u.3N'vtct,lit}
t,a.1k, vi bricavinyvvids-nrtii[Lai kinold° Juc to dcvv'iipuoituir."
28. Amend the second paragraph of Section 4.5.6 Technical Constraints to
amend the last bulleted item to read:
"Many of these problems may be avoided through selection of the
appropriate type and species of vegetation. Such selections and expert
advice must be obtained from qualified individuals in revegetation and
bioengineering. Invasion by other species is quite likely over the years the
icc'cJ U tai ii id ;a III u1,otativ,c"
29. Amend the first two paragraphs of Section 4.6 Natural Channels to read:
"Natural waterways in the Denver regionWeld County are sometimes in the
form of steep-banked gulches,which have eroding banks and bottoms. On
the other hand, many natural waterways exist in urbanized and to-
beurbanized areas, which have mild slopes, are reasonably stable, and are
not currently degrading. If the channel will be used to carry storm runoff
from an urbanized area, it can be assumed that the changes in the runoff
regime will increase channel erosion and instability. Careful hydraulic
analysis is needed to address this projected erosion. In most cases,
stabilization of the channel will be required. Stabilization using
bioengineering techniques, described in Section 4.5 of this chapter, has the
advantage of preserving and even enhancing the natural character and
functions of the channel. Some structural stabilization measures will also
be required in combination with the bioengineered stabilization measures.
In tho D0Y,Ve, a1oeWeld County, most natural waterways will need drops
and/or erosion cutoff check structures to maintain a mild channel slope and
to control channel erosion. Typically, these grade control structures are
spaced to limit channel degradation to what is expected to be the final stable
longitudinal slope after full urbanization of the tributary watershed. In the
Denver area, this slope, depending on watershed size and channel soils,
has been observed to range from 0.2 to 0.6%, with the South Platte River
itself approaching a slope of 0.1%. Whenever feasible, natural channels
should be kept in as near a natural condition as possible by limiting
modifications to those necessary to protect against the destabilizing
hydrologic forces caused by urbanization."
30. Amend the fifth paragraph of Section 4.6 Natural Channels to read:
"The following design criteria are recommended when evaluating natural
channels:
1. The channel and overbank floodplain should have adequate capacity
for the 100-year flood.
2. A water surface profile should be defined in order to identify the 100-
year floodplain, to control earthwork, and to build structures in a
manner consistent with the Distict's and 11/4,1/4.06/Veld County's
floodplain regulations and ordinances."
No change to remainder of section.
Section 8-11-40. Weld County Addendum to the Text of the Urban Storm Drainage Criteria-
Volume 2
A. Chapter 8 - Hydraulic Structures.
1. Add the following to Section 4.1.2 Bridge Opening Freeboard: "The bridge
low chord elevation shall be a minimum of 1-foot above the 100-year water
course energy grade line."
B. Chapter 9 - Culverts
1. Amend the third paragraph of Section 1.1.2 Headwater to read:
'TI ie headwater elevation for the design discharge should be consistent with
HiCf,ccLvarJa;ud- 4ortvppniyu; tciisn;H;crOLICYul;opts; oftl,isMarival
(Tables DP1 through DP-3). TI redcaigi;ershouldwaiify that tl;cnata;Jilt;
Jividao arc I nyl;a. ti tar i tl is dc.wuy;H mad Wok] slc.vativi to. I. flat tc;i air r,
U,0,,,090 d,O1Ja.o a;c AO'I ill.daftnt..Jvn. uL,xIsL,I It and uulv..;to of ivuld L�
itn atcJ and desiy;wJ fur tI is Icaot JiorGptw;r1-1—f H rcCnistn ry flvvv Jiof;iLutivi r
The maximum culvert headwater to diameter ratios are:
STORM FREQUENCY HEADWATER TO DIAMETER
10-Year HW/D < 1.0
100-Year HW/D < 1.5
The minimum culvert capacities are:
STREET MINIMUM CAPACITY
CLASSIFICATION (RECURRENCE INTERVAL)
Local 10-Year
Collector 10-Year
Arterial 10-Year
When the flow in a roadside ditch exceeds the capacity of the culvert and
overtops the cross street,the flow over the street crown shall not exceed the
minor storm and major storm depth limits presented in Chapter 3, Planning,
Section 9.4 of the Weld County Storm Drainage Criteria manual. Weld
County may require additional culvert capacity in order to prevent flooding
of adjacent properties."
2. Add the following to Section 2.1.1 Energy and Hydraulic Grade Lines: "The
hydraulic grade line and energy grade line shall be determined for each
culvert system and included in the Final Drainage Report. Each culvert
system shall be profiled on the Final Construction Drawings and shall
include the design flow hydraulic grade line."
3. Amend Section 3.5.3 Culvert Diameter to read: "It is the policy of Weld
County to require a minimum culvert diameter of 15 inches. Weld County
may require additional culvert capacity in order to prevent flooding of
adjacent properties. After the invert elevations have been assumed and
using the design computation forms(e.g., Figure CU-8),the capacity charts
(e.g., Figure CU-7),and the nomographs,the diameter of pipe that will meet
the headwater requirements should be determined. Since small diameter
pipes are often plugged by sediment and debris, it is recommended that
pipe smaller than 18 inches not be used for any drainage where this Manual
applies. Since the pipe roughness influences the culvert diameter, both
w.n ete-ai emu. uyat�J ,,iota' N;Nc al b.Levi3O;Jered in desiw , if l,otlr
will satisfy the h.adwat0, reyu,reme,'ta. Refer to the"Weld County Design
and Construction Standards and Specifications", latest edition,for allowable
culvert pipe materials. The Manning's roughness coefficient "n" for all
culvert pipe sizing calculations shall be 0.013 regardless of pipe material
(Concrete, PVC, or HDPE) with the exception of corrugated metal pipes
which shall have a coefficient of 0.025."
4. Add the following to the last paragraph of Section 4.1 Projecting Inlets: "At
a minimum, a culvert entrance and outlet shall include a flared end section.
Erosion protection (riprap, etcetera) may be required."
5. Amend the fifth paragraph of Section 8.0 Trash/Safety Racks to read:
"Thy Dist,i,AWeld County strongly recommends against the installation of
trash racks at culvert outlets, because debris or a person carried into the
culvert will impinge against the rack, thus leading to pressurized conditions
within the culvert,virtually destroying its flow capacity and creating a greater
hazard to the public or a person trapped in the culvert than not having one."
6. Amend Section 8.1 Collapsible Gratings to read:
"The Disl,; .tWeld County does not recommend the use of collapsible
gratings. On larger culverts where a collapsible grating is deemed
necessary by a local jurisdiction or an engineer, such gratings must be
carefully designed from the structural standpoint so that collapse is achieved
with a hydrostatic load of perhaps one-half of the maximum backwater head
allowable. Collapse of the trash rack should be such that it clears the
waterway opening adequately to permit the inlet to function properly without
itself contributing to potential plugging of the culvert."
C. Chapter 10 - Storage
1. Add the following subparagraph to the sixth paragraph of Section 2.0
Application Of Different Types Of Storage: "6. Above ground parking lot
detention ponds may be utilized when land area for a grassed lined
detention pond is not available. To prevent damage to and floatation of
automobiles,parking lot detention ponds shall not exceed 12 inches in depth
at any point. Parking lot detention ponds shall have signage to inform the
general public about the potential for flooding. The 100-year water surface
elevation of a parking lot detention pond shall not encroach into a public
street."
2. Amend Section 3.1.2 Use of Regional (i.e., Hydrograph Routing) Detention
Sizing Procedure to read:
"For tributary catchments larger than 90 acres in size, tl,c DiatrhiWeld
County recommends or may require the use of hydrograph flood routing
procedures(i.e., using CUHP-generated hydrographs and reservoir routing
calculations, see Section 3.4). In addition, if there are upstream detention
facilities in the watershed,hydrograph routing methods should be employed.
If off-site tributary areas contribute runoff to an on-site detention facility, the
total tributary area, assuming fully developed off-site land uses, must be
included in the sizing of the on-site storage volumes in order to account for
the total runoff volume in the watershed. Sizing of detention storage
volumes shall utilize outflow hydrographs that have been properly calculated
to account for variable head discharge rates."
3. Add the following to Section 3.1.3 Water Quality Capture Volume in Sizing
Detention Storage: "Within Weld County, the water quality capture volume
shall be considered a portion of the total 100-year detention pond volume."
4. Amend first paragraph of Section 3.2.1 Maximum Allowable Unit Release
Rates for On-Site Facilities to read:
"The maximum allowable unit release rates per acre for on-site detention
facilities for a number of design return periods are listed in Table SO-1.
These rates apply unless other rates are recommended in a District-
appr'.n }Weld County-approved master plan."
5. Amend Section 3.2.2 Empirical Equations for the Sizing of On-Site Detention
Storage Volumes to read:
"Urbonas and Glidden (1983), as part of the District's ongoing hydrologic
research, conducted studies that evaluated peak storm runoff flows along
major drainageways. The following set of empirical equations provided
preliminary estimates of on-site detention facility sizing for areas within the
DistrictWeld County. They are not intended for use when off-site inflows are
present or when multi-stage controls are to be used(e.g., 10-and 100-year
peak control) at the storage facility. In addition, these equations are not
intended to replace detailed hydrologic and flood routing analysis, or even
the analysis using the Rational Formula-based FAA method for the sizing
of detention storage volumes. The District does not promote the use of
these empirical equations. It does not object, however, to their use by local
governments who have adopted them or want to adopt them as minimum
requirements for the sizing of on-site detention for small catchments within
their jurisdiction. if thy Dishi,,tWhere Weld County has a master drainage
plan that contains specific guidance for detention storage or sizing of on-site
detention facilities, those guidelines should be followed instead. The
empirical equations are as follows:..."
Remainder of Section - No Change.
6. Amend Section 3.2.4 Multi-Level Control to read:
"The DistrictWeld County recommends that no more than two levels of
controls, in addition to the WQCV controls, be used for on-site detention
facilities. These levels should be the 100-year storm, in combination with
tl,e 5-ur the 10-year storm. More levels of control may appear to provide
increased protection, but the added complexity of design and the
questionable accuracy of the extended precision for such requirements
rarely justify their use. Design Example 6.1 shows calculations of allowable
release rate and storage requirement using empirical equations."
7. Add the following to Section 3.3 Design Storms for Sizing Storage Volumes:
"The 10-year and 100-year storms shall be the design storms for all water
quality and detention pond designs, respectively, within Weld County."
8. Amend Section 3.3.2 Drainage and Flood Control to read:
"Sizing of storage facilities and outlet works for flood control purposes is
generally based on whether the facility is on-site or regional. For an
individual development site, local municipalities will often dictate the on-site
detention design storms that need to be addressed by the new
development. On a watershed level,full system master planning studies are
needed to identify the appropriate release rates for various design storms.
Thus, whenever a Dhstri,,t app,ov .Weld-County approved master plan
recommends detention sites and release rates or on-site detention/retention
storage and release rates, those rates should be used in final design of
detention/retention facilities. Other considerations that have to be taken into
account include downstream system stability, the stream's capacity to
convey discharges from the detention/retention facility in combination with
the downstream runoff contributions to the drainage system, potential for
flood damages to downstream properties, and other factors that may be
specific to each situation at hand."
9. Add the following to Section 3.3.3 Spillway Sizing: "Each detention pond
shall contain an emergency spillway capable of conveying the peak
100-year storm discharge draining into the detention pond. The invert of the
emergency spillway shall be set equal to or above the 100-year water
surface elevation. The depth of flow out the emergency spillway shall be<6
inches and the spillway shall have effective erosion protection."
10. Amend Section 3.3.4 Retention Facilities to read:
"When a retention basin is proposed as a temporary solution to an evolving
drainage problem, tic Di0t. .tWeld County recommends that it be sized to
capture, as a minimum, the runoff equal to 1.5 times the 24-hour, 100-year
storm plus 1-foot freeboard. The facility also has to be situated and
designed so that when it overtops, no human-occupied or critical structures
(e.g., electrical vaults) will be flooded, and no catastrophic failure at the
facility(e.g., loss of dam embankment)will occur. It is also recommended
that retention facilities be as shallow as feasible to encourage infiltration and
other losses of the captured urban runoff. When a trickle outflow can be
accepted downstream, one shall be provided and sized in accordance with
the locally approved release rates, preferably capable of emptying the full
volume in 10 to 14 days."
11. Amend subparagraph #2 of Section 3.4 Reservoir Routing of Storm
Hydrographs for Sizing of Storage Volumes to read:
"2. Determine Hydrology: Determine the inflow hydrograph to the
storage basin and the allowable peak discharge from the basin for
the design storm events. The hydrograph may be available in
published district outfall system planning or a major diainagcway
master plan reportWeld County Master Drainage Plans or Updates.
The allowable peak discharge is limited by the local criteria or by the
requirements spelled out in a District-approvedWeld County-
approved master plan."
12. Amend subparagraph #3 of Section 3.4.1 Initial Sizing to read:
" The outflow rate Qo (cfs) calculated as:
Lin - Qw (so-io)
n
in which Qpo is the peak outflow rate. The allowable peak outflow rate is
determined from a DistrictWeld County master plan, local ordinance, or
other considerations described in Section 3.3.2."
13. Amend Section 3.4.2 Initial Shaping to read:
"The initial shaping of the storage basin provides a starting point for defining
the stage-storage relationship. The stage-storage relationship will be
refined during preliminary and final design phases of the project. The initial
shaping is easiest when regular geometry(such as a triangle or rectangle)
is used for approximation. The detention volume needed for any specific
design storm is combined with site constraints (e.g., size or depth
limitations, number of control stages, etc.) and the simplified formulas
describing the basin geometry in order to develop an initial depth, length,
and width for the basin. Design spreadsheets can be used to assist in
preliminary shaping of the storage facility. The Dist,ktWeld County does
not encourage the use of storage facilities with uniform, geometric
properties. To the contrary,tl,c Dist ktWeld County encourages designers
to collaborate with landscape architects to develop storage facilities that are
attractive visually, fit into the fabric of the landscape, and enhance the
overall character of an area. However, using regular geometry can
approximate initial shaping of a non-uniformly shaped facility."
14. Amend Section 4.0 Final Design Considerations to read:
"Final design of a storage facility should recognize the kinds of
considerations described in this section. It is beyond the scope of this
Manual to provide detailed dam design guidance. There are many excellent
references in this regard such as Design of Small Dams (U.S. Bureau of
Reclamation 1987). The Dist,iL.tWeld County urges all designers to review
and adhere to the guidance in such references because the failure of even
small embankments can have serious consequences for the public. General
guidelines for the final design phase of detention or retention facilities
follows."
15. Amend Section 4.3 Geometry of Storage Facilities to read:
"The geometry of a storage facility depends on specific site conditions such
as adjoining land uses, topography, geology, preserving/creating wildlife
habitat, volume requirements, etc. Several key features should be
incorporated in all storage facilities located within the Dist,ibtWeld County
(see Figure SO-6). These include(a)4:1 or flatter side slopes of all banks,
(b)low-flow or trickle-flow channel unless a permanent pool takes its place,
(c) forebay, (d) pond bottom sloped at least 1 percent to drain toward the
low-flow or trickle-flow channel or the outlet, and (e)emergency spillway or
fun tfn.atv,, of the awl.,,k,,,ent to plovci catastupl1k, failure vvl,c,r
overtoppedwith erosion protection designed to safely convey the 100-year
overtopping flows."
16. Amend subparagraph #2 of Section 4.4 Embankments and Cut Slopes to
read:
"2. Freeboard—The elevation of the top of the embankment shall be a
minimum of 1 foot above the water surface elevation when the
ei nergency spillway is conveying the maximum design or emergency
ilowl00-year water surface elevation in the detention pond. When
relevant, all SEO dam safety criteria must be carefully considered
when determining the freeboard capacity of an impoundment."
17. Add the following two subparagraphs to Section 4.4 Embankments and Cut
Slopes:
"5. Emergency Spillway Downstream Protection-In order to protect the
emergency spillway from catastrophic erosion failure, buried riprap
shall be placed from the emergency spillway downhill to the
embankment toe of slope and covered with 6 inches of topsoil. The
riprap shall be sized at the time of final engineering design.
Grouting of the riprap may be required.
6. Concrete Cutoff Wall - A concrete cutoff wall, 8 inches thick, 3 foot
deep, extending 5 feet into the embankment beyond the emergency
spillway opening, is encouraged on all private detention ponds and
required on all publicly-owned regional detention ponds. A concrete
cutoff wall will permanently define the emergency spillway opening.
The emergency spillway elevation shall be tied back into the top of
embankment using a maximum slope of 4:1."
18. Add the following to Section 4.7 Outlet Works: "The outlet pipe of regional
detention ponds shall contain a minimum of two (2) concrete cutoff walls
embedded a minimum of 18 inches into undisturbed earthen soil. The cutoff
walls shall be a minimum of 8 inches thick. The outlet pipe bedding
material shall consist of native earthen soil and not granular bedding
material to at least the first downstream manhole or daylight point."
19. Add the following to Section 4.8 Trash Racks: "For safety reasons, trash
rack angles are to be 3 horizontal to 1 vertical (3:1) or flatter per Urban
Drainage research (Nelson & Kroeger, 2005)."
20. Add the following subparagraph to Section 4.10 Operation and
Maintenance: "15. An operations maintenance manual for each water
quality pond, detention pond, and outlet structure
facility shall be developed and provided to the Weld
County Department of Public Works and the
development Homeowners'Association at the time of
final submittal."
21. Add the following to Section 4.11 Access: "Drivable access applies only to
Regional Detention facilities within Weld County. Each regional detention
pond will be considered on a case-by-case basis at the time of final design."
22. Add the following as the third paragraph of Section 5.0 Criteria For District
Maintenance Eligibility: "Regional Master Planned detention ponds,
designed and constructed by or on behalf of Weld County, shall be owned
and maintained by County as specified in the applicable Development
Agreement(s). All other detention ponds shall be considered privately
owned and privately maintained."
D. Chapter 11 - Flood Proofing
1. Amend the second paragraph of Section 1.2.1 Classification of Flood
Proofing to read:
"In H.°D01 ama ..I\AI upulltal ran.aW eld County,flood-proofing efforts should
focus on permanent measures due to the rapid response of most of the
Front Range stream systems. Contingent measures are more effective
when combined with an early flood warning system or in areas not
immediately adjacent to a stream channel."
2. Amend Section 4.1.1 Determine Flood Hazards to read:
"Information about flooding in the area is available from H District au nJ lu..at
officialsWeld County officials or directly from FEMA at:
http://www.msc.fema.gov/hardcopy.shtml. Local officials, design
professionals,and contractors can use this information,along with the flood
hazard information developed by FEMA and other agencies and
organizations, to provide advice about retrofitting options."
3. Amend the first paragraph of Section 4.1.3 Contact Local Officials to read:
"The District and IocalWeld County officials have copies of the FIS and
FIRM published for the community by FEMA. District or communityWeld
County officials can determine whether a building is in the regulatory
floodplain and, if so, the FPE at the location of the building."
E. Chapter 12 - Revegetation
1. Amend Section 1.0 Introduction to read:
"This chapter provides information on methods and plant materials needed
for revegetation of drainage facilities within the Urba, Drainage a..J FMB
Conti el District (astri..t)Weld County. Establishment of a robust cover of
vegetation is critical to the proper functioning of drainage structures such as
grass-lined channels, detention basins, retention ponds, and wetlands.
Vegetation serves multiple purposes, including stabilization of structures to
prevent excessive erosion and removal of pollutants in stormwater. The
semi-arid nature of the climate, prevalence of introduced weeds,and variety
of soil types encountered in the ash ketWeld County virtually mandate
prompt implementation of a revegetation plan to achieve revegetation
success."
2. Add the following to the last paragraph of Section 2.0 Scope of This Chapter
and Relation to Other Relevant Documents: "See revisions to RV tables
included in this chapter for Weld County-specific seed mix
recommendations."
3. Add the following as a bulleted item of Section 3.2 Site Preparation: "•
Before revegetation work is started, an inventory of vegetation should be
taken. If noxious weeds, as listed in Weld County Code, Chapter 15, exist
on-site, appropriate steps need to be taken before, during, and after work
is completed, to control their spread. Contact the Weld County Department
of Public Works Weed Division Supervisor at 970-304-6496 for additional
information if needed."
4. Add the following as a bulleted item of Section 3.3 Seeding and Planting:
• Seed mixtures should be coated with Mycorrhiza at the rate of 2
pounds per acre at the time of seeding. If mulching with straw, be
sure the straw is seed free and weed free."
5. Amend the second and third bulleted items of Section 3.4 Maintenance to
read:
• Access to and grazing on recently revegetated areas should be
limited with temporary fencing and signage while plants are
becoming established (�iurI!rally the fi.0t y..a,for 1 to 2 years at
least).
• Weed infestations should be managed using appropriate physical or
chemical, col LI.,Ivyi.,af methods as soon as possible. (Set tl.e otl to]
t}v..Ul eta icfci ci iwi] fv, Jctails v'rvvcc.J-i i'or,aycn ici itvF,tivi tor)"
6. Add the following as the last bulleted item of 3.4 Maintenance:
• The project owner/developer, not Weld County, will be responsible
for site maintenance until vegetative establishment."
7. Amend the first paragraph of Section 4.2 Soil Amendments to read:
"Native topsoil should be stripped and saved for revegetation. If this is not
appropriate due to poor soil quality or for some other reason, then subsoil
can be made conducive for plant growth through the use of amendments.
Since soil pH is typically suitable within tl c DIat.ketWeld County,
amendments are usually needed for increasing organic matter content or
providing nutrients in the form of fertilizers. Consideration should be given
to importing topsoil, from the vicinity, instead of amending poor quality
subsoil, as this may be less expensive."
8. Amend the third paragraph of Section 4.2 Soil Amendments to read:
"Detailed information on the types and amounts of soil amendments and
fertilizers needed is beyond the scope of this document and can be found
in the documents previously referenced. However, information is provided
on the use of humate soil conditioner and biosol fertilizer. Both of these
materials are relatively new and show promise as soil conditioners and
sources of slow-release fertilizers for revegetation work in tl is Diat1 ktWeld
County."
9. Amend the second paragraph of Section 4.3 Recommended Seed Mixes to
read:
"Recommended seed mixes for the bottom (wet soils) and side slopes of
drainage facilities within tl aot1;.tWeld County are included in Tables RV-
1 and RV-2. Mixes for different soil conditions in upland areas are provided
in Tables RV-3 to RV-6. The seeding rates in these mixes are
recommended minimum rates that should be used for drill seeding. These
rates should be doubled for broadcast seeding and increased by 50% if a
Brillion drill or hydro-seeding is used."
10. Add the following as the fourth paragraph of Section 4.3 Recommended
Seed Mixes: "The inclusion of wild flowers in the seed mix is optional in
Weld County. Areas seeded along Weld County roads may be spot sprayed
by the county to control the spread of noxious weeds. This spraying may
affect some wild flower species. Do not plant trees or shrubs in the County
right-of-way."
11. Amend Table RV-1 as follows:
Table RV-1—Recommended Seed Mix for High Water Table Conditions'
Growth Growth Lbs
Common Name(Variety) Scientific Name Season Form Seeds/Lb PLS/Acre
Redtop- Agrostis alba Warm Sod 5,000,000 0.1
Switchgrass(Pathfinder) Panicum wrgatum Warm Sod/bunch 389.000 2.2
Western wheatgrass(Aruba) Pascopymm smithii Cool Sod 110.000 7.9
Inland saltgrass D/stichlis spicafa Warm Sod 520,000 1.0
Wooly sedge Carex lanuginose Cool Sod 400,000 0.1
Baltic rush Juncus balticus Cool Sod 109,300.000 0.1
Prairie cordgrass Spartina pectinate Coll Sod 110.000 1.0
12.4
Wildflowers
Nudall's sunflower Helianthus nuttallii --- --- 250.000 0.10
Wild bergamot Monarda fistulosa --- -- 1,450.000 0.12
Yarrow Achilles millefolium --- ... 2.770.000 0.06
Blue vervain Verbena hostels --- --- 0.12
0.40
'For areas of facilities located near or on the bottom or where wet soil conditions occur. Planting of
potted nursery stock wetland plants 2-foot on-center is recommended for sites with wetland hydrology.
Nonnative.
a. Delete the row containing Redtop (Agrostis alba).
b. Delete the row containing Nuttall's sunflower(Holianthus nuttallii).
12. Amend Table RV-2 as follows:
Table RV-2—Recommended Seed Mix for Transition Areas'
Growth Growth Lbs
Common Name(Variety) Scientific Name Season Form Seeds/Lb PLS/Acre
Sheep fescue(Durar) Festuca ovina Cool Bunch 680,000 1.3
Western wheatgrass Pascopynim smithii Cool Sod 110.000 7.9
(Arriba)
Alkali sacaton Spolobolus amides Warm Bunch 1,758.000 0.5
Slender wheatgrass Elymus trachycaulus Cool Bunch 159,000 5.5
Canadian bluegrass Pon compress° Cool Sod 2,500.000 0.3
(Ruebens)'x
Switch grass(Pathfinder) Panicum wrgatum Warm Sod/bunch 389.000 13
16.8
Wildflowers
Blanket flower G8/IW/dia anstata -- --- 132.000 0.25
Prairie coneflower Ratibida cotumnaris -- --- 1.230.000 0.20
Purple prairie clover Petalostemum purpurea --- --- 210.000 0.20
Gayfeather Liatris punctata --- --- 138.000 0.06
Flax Linum lewuii -- -- 293,000 0.20
Penstemon Penstemon sbictus -- -- 592.000 0.20
Yarrow Achilles millefo#um -- -.. 2,770,000 0.03
1.14
'For side slopes or between wet and dry areas.
2 Substitute 1.7 lbs PLS/acre of inland salt grass(Distichks spicata)in salty soils.
'Nonnative.
a. Delete the row containing Canadian bluegrass (Ruebens) (Poa
compressa).
b. Delete the row containing Flax* (Linum lewisii).
13. Amend Table RV-3 as follows:
Table RV-3--Rocami tended Seed Mx for Alkali Soils
Growth Growth Lbs
Common Name(Variety) Scientific Name Season Form Seeds/Lb PLS/Acre
Alkali sacaton Sporobolr s aitNdes Cool Bunch 1/50.000 0.5
Streambank wheatgrass Agropyron Moan= Cool Sod 156,000 5.6
(Sodar)
Inland salt grass Distichlis sbicta Warm Sod 520,000 1.7
Western wheatgrass(Arriba) Pascopymm smithri Cool Sod 110,000 7.9
Blue grama(Hachita) Chondrosum gracile Warm Sod 825,000 4.0
Bufalograss Buchloe dactyloides Warm Sod 56.000 2.0
211
Wildflowers
Blanket flower Gaillardia anstata -- --- 132,000 0.25
Prairie coneflower Ratibida columnans --- --- 1,230,000 0.20
Purple prairie clover Petalostemum purptrea -- -- 210.000 0.20
Gayfeather Liatns punctata --- ..- 138,000 0.06
Blue Flax Linum lew'sii --- -.. 293.000 0.20
Rocky Mountain penstemon Penstemon stnctus .-. --- 592.000 0.20
Yarrow Achilles mdlefolium --- --- 2.770.000 0.03
1.14
a. Delete the row containing Blue Flax (Linum lewisii).
14. Amend Table RV-4 as follows:
Table RV-4—Raeornm.nd.d Se•d Mk for Loamy Sells
Growth Growth Lbs
Common Name(Variety) Scientific Name Season Form Seeds/Lb PLS/Acre
Sheep fescue(Durar) Festuce ovine Cool Bunch 680,000 0.6
Canby bluegrass Poe canbyi Cool Bunch 926,000 0.5
Thickspike wheatgrass Elymus Ianceolatus Cool Sod 154.000 51
(Critana)
Western wheatgrass Pascopyrum small! Cool Sod 110,000 7.9
(Arriba)
Blue grama(Hahita) Chondrosum gracile Warm Sod/bunch 825,000 1.1
Switchgrass(Pathfinder) Panicum virgatum Warm Sod/bunch 389.000 1.0
Sideoats grama(Butte) Boutslou curtipendula Warm Sod 191,000 2.0
18.8
Wildflowers
Blanket flower Gaillardia ahstata --- — 132,000 0.25
Prairie coneflower Ratibida columnaris ..- -- 1.230,000 0.20
Purple prairie clover Petalostemum purpurea -- --- 210,000 0.20
Gayfeather Liatnspunctata ..- -- 138,000 0.06
Flax Linum lewisii --- --- 293,000 0.20
Penstemon Penstemon sbictus --- -.. 592,000 0.20
Yarrow Achilles milletokum --- --- 2,770.000 0.03
1.14
a. Delete the row containing Canby bluegrass (Poa canbyi).
b. Delete the row containing Flax (Linum lewisii).
15. Amend Table RV-5 as follows:
Table RV-5—Recommended Said Mix for Sandy Solis
Growth Growth Lbs
Common Name(Variety) Scientific Name Season Form Seeds/Lb PLS/Acre
Blue grama(Hachita) Chondrosum gracile Warm Sod/bunch 825,000 21
Little bluestem(Camper) Schizachynum Warm Bunch 260,000 3.0
scoparium
Prairie sandreed Calamovifa longifolia Warm Sod 274.000 3.0
Sand dropseed Sporobolus cryptandrus Warm Bunch 5,298,000 0.3
Sideoats grama(Vaughn) Bouteloua curtipendula Warm Sod/bunch 191.000 5.6
Western wheatgrass Pascopyrum smnhii Cool Sod 110.000 8.0
(Arriba)
22.0
Wildflowers
Blanket flower Gaillardia anstata --- .-- 132.000 0.25
Prairie coneflower Ralibida columnifera --. --- 1.230.000 0.20
Purple prairie clover Petalostemum purprrea --- -- 210.000 0.20
Gayfeather Liams punctata -- --- 138.000 0.06
Flax Linum lewisii --- -- 293.000 0.20
Penstemon Penstemon status -- --- 592.000 0.20
Yarrow Achilles millefohum --- -- 2.770.000 0.03
1.14
a. Change 2.1 to 0.3 in Table RV-5.
b. Change 0.3 to 2.1 in Table RV-5.
c. Delete the row containing Flax (Linum lewisii).
16. Amend Table RV-7 as follows:
Table RV-7—Wildflower Mix(to be seeded with grass seed mix)'
Common Name(Variety) Scientific Name Flower Color Seeds/Lb Lbs PLS/Acre
Scarlet globemallow Sphaeralcea coccinea Red/orange 500,000 0.6
Blue flax Linum Iewisii Blue 293.000 0-6
Purple prairie clover Petabstemumpurpureunr Red-purple 210.000 0.7
White prairie clover Petebsterrum candidum White 354.000 0.6
California poppy Eschscholtzia californica Orange 293,000 0.3
Blanket flower Gaillardia adstata Yellowlred 132.000 1.0
Prairie aster Aster tanacetifdlus Violet 496.000 0.3
Blackeyed Susan Rudbeckia hirta Yellow 1.710.000 0.3
Purple coneflower Echinacee purpurea Purple 117.000 0.9
Yarrow Achilleanillefokum White 2,770,000 0.1
Gayfeather baths punters Roselpurple 138.000 0.6
Total 6.0
'This is a general mix for the District that stresses native perennials that do well in a range of soil types in
sunny locations.
a. Delete the row containing Blue Flax(Linum lewisii).
b. Delete the row containing California poppy (Eschscholtzia
californica).
c. Delete the row containing Blackeyed Susan (Rudbeckia hirta).
17. Amend Table RV-8 as follows:
Table RV I Recommended Shrubs and Tres'
Planting
Common Name Scientific Name Height(fl} Sun/Shade Zone Notes
Shrubs
Saskatoon Amelanchier alnifolra 3-15 Sun Upland Good for wildlife
serviceberry
Lead plant Amorpha lrutcosa 3-- 8 Sun Upland Drought tolerant
Rubber Chrysothamnus 2 3 Sun Upland Drought tolerant
rabbitbrush nauseosus
Wild plum Prunus Americana 5-20 Sun/shade Transition Forms thickets
Chokecherrry Prunus virginiana 5 -20 Sun/shade Transition Forms thickets
Smooth sumac Rhus glabra 4 -7 Sun/shade Upland Good for wildlife
Oakbrush sumac Rhus trilobata 2-6 Sun/shade Upland Drought tolerant
Wax currant Ribes cereum 3-5 Sun/shade Transition Good for wildlife
Redosier dogwood Comus stolomlera 3 9 Shade Wetland Drought tolerant
Sandbar willow Sahx exrgua 6- 10 Sun Transition Requires more
or wetland water
Snowberry Symphoricarpos 2 5 Sun/shade Transition Prefers moist area
oreophdus
Spanish bayonet Yucca glauca 1 --2 Sun Upland Drought tolerant
Woods rose Rosa woodsy 2 -3 _ Sun Upland Establishes quickly
Silver buffaloberry Shepherdia argentea 6- 13 Sun Upland Drought tolerant
Trees
Narrow leaf Populus angustilolia 10--30 Sun Transition Requires more
cottonwood or wetland water
Plains cottonwood Popcdus de/to/des 50 Sun Transition Requires more
water
Rocky Mountain Junrperus 5-- 15 Sun Upland Drought tolerant
juniper scapularum
Colorado blue Picea pungens 60-- 100 Sun Transition Requires more
spruce _ water
Ponderosa pine Pinus ponderosa 75-100 Sun Upland Drought tolerant
Peach leaf willow Sakx amygdaloides 15-30 Sun Welland Requires more
water
'Trees and shrubs should not be planted in the bottoms of drainage channels or where they could
impede flow and decrease channel capacity It is recommended that containerized stock(e g 2-gallon.
5-gallon)be used for trees and shrubs.
a. Delete..the row containing Rubber rabbitbrush (Chrysothamnus
nauseosus).
b. Delete the row containing Spanish bayonet (Yucca glauca).
18. Amend Table RV-9 as follows:
Table RV-tl—Recommended Plants lot Constructed Wetlands and Retention Pond Shelf'
Depth of Water(ft) Common Name Scientific Name Notes
0- 1.5 Soft stem bulrush Sarpus valldus • Planted plants should
Hard stem bulrush Scitpus acutus extend above water
Arrowhead Sagittane latdolia • Plants will invade
Alkali bulrush Saranmaritimus deeper water with time
Smart weed Polygonum persicaria
0.25-0.5 Three-square Schpus amencanus • Planted plants should
Spike rush Eleochans palustru extend above water
0-0.25 Rice cut grass Leersia otyzoides • Species will adjust to
Nebraska sedge Carex nebrascensis moisture conditions
with lime
Soft rush Juncus effuses
Baltic rush Juncus balticus
Toney's rush Juncus torreyl
Foxtail barley Hordeum jubatum
Height above water
0-1 Milkweed Asclepias incamata
0-3 Switchgrass Pandum virgatum • Best to plant near
Prairie cordgrass Spartina pectinate water where soil is wet
Beebalm Monarda flstulosa • Colorful wildflower
'It is recommended that containerized stock be used for wetland plantings. It is not recommended that
cattails be planted since they will invade naturally.
a. Delete the row containing Smart weed (Polygonum persicaria).
b. Delete the row containing Foxtail barley(Hordeum jubatum).
19. Add the following to Section 4.4 Trees, Shrubs and Wetland Plantings:
"GRASS SEEDING RECOMMENDATIONS FOR WELD COUNTY
GENERAL INFORMATION
1. If a species is listed as "15% to 30%" in mixture, please use a
percentage within the given parameters to arrive at the amount used
in the seed mix.
2. The numbers listed in the "Seeding Rate - Dryland" column is to be
used for most dryland sites in this area. The amounts listed in
"Seeding Rate- Irrigated"are to be used for those areas that will be
irrigated, or sites that are highly erodible.
3. A seed mix is complete when a combination of the species chosen
totals 100%.
4. The recommended varieties column lists the preferred varieties that
are known to do well in this area. If this column is blank, refer to a
local seed dealer for recommendations on varieties.
TO OBTAIN DESIRED SEED MIX
1. Refer to the appropriate range site, defined in the local soil survey.
2. Chose the species within each range site. Names in bold italics
represent the preferred species for each site.
3. If the range of percentage in the mix column lists "up to 45%" then
chose an amount of the species to use in the mix that correlates
within this range.
4. Take the percentage of each species used in the mix and multiple
by the seeding rate.
a. Example:
1) Site is a dryland site.
2) Sand bluestem at 8.0 pounds of PLS/Acre its used at
25% in the seed mix.
3) Take 25% x 8.0 = 2.0 pounds of Sand bluestem to
use in the mix per acre.
4) Multiple the 2.0 pounds by the number of acres to get
the total amount of pounds of the species to use for
the mix.
b. NOTE: The seeding rates are listed in Pounds of Pure Live
Seed (PLS) per acre, and not in bulk pounds.
Refer to the following tables for grass seeding recommendations.
Table RV-10 GRASS SEEDING TABLES BASED ON RANGE SITES
Species indicated in bold italics indicates the preferred species
RANGE SITE: Deed Sands, Choppy Sands, Sandy Bottomland, Sandy Meadow, Sandy
Foothills, Sandy Divide
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX
DRYLAND IRRIGATE
D
Sand Bluestem Elida, Woodward, Garden 20 to 35 8.0 16.0
Yellow Indiangrass Llano, Holt, Cheyenne, Oto 10 to 30 5.0 10.0
Switchgrass Grenville, Nebraska 28, 10 to 30 2.5 4.5
Blackwell, Pathfinder
-
Prairie sandreed Goshen 10 to 30 3.5 6.5
Sideoats grama Vaughn, Butte, Niner, up to 15 4.5 9.0
El Reno, Haskell
Little Bluestem Pastura, Cimmarron up to 10 3.5 7.0
Blue grama Hachital, Lovington up to 10 1.5 3.0
Western wheatgrass Arriba, Barton, Rosana up to 10 8.0 16.0
Needleandthread up to 15 7.5 15.0
Thickspike Critana up to 10 5.5 11.0
wheatgrass
Indian ricegrass Paloma up to 10 6.0 12.5
RANGE SITE: Sandy Plains
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX DRYLAND IRRIGATE
D
Sand Bluestem Elida, Woodward, Garden 15 to 30 8.0 16.0
Prairie sandreed Goshen 10 to 25 3.5 6.5
Switchgrass Grenville, Nebraska 28, 10 to 30 2.5 4.5
Blackwell, Pathfinder
Sideoats grama Vaughn, Butte, Niner, 5 to 20 4.5 9.0
El Reno, Haskell
Yellow Indiangrass Llano, Holt, Cheyenne, Oto 5 to 20 5.0 10.0
Western wheatgrass Arriba, Barton, Rosana up to 20 8.0 16.0
Blue grama Hachital, Lovington up to 15 1.5 3.0
Little bluestem Pastura, Cimmarron up to 10 3.5 7.0
Needleandthread up to 15 7.5 15.0
Thickspike Critana up to 10 5.5 11.0
wheatgrass
Indian ricegrass Paloma up to 10 6.0 12.5
RANGE SITE: Loamy Plains Clayey Plains, Loamy Slopes
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX
DRYLAND IRRIGATE
D
Western wheatgrass Arriba, Barton, Rosana 20 to 45 8.0 16.0
Sideoats grama Vaughn, Butte, Niner, 20 to 40 4.5 9.0
El Reno, Haskell
Blue grama Hachital, Lovington 10 to 25 1.5 3.0
Green Needlegrass up to 30 5.0 10.0
Needleandthread up to 15 7.5 15.0
Switchgrass Grenville, Nebraska 28, up to 20 2.5 4.5
Blackwell, Pathfinder
Big bluestem Kaw up to 10 5.5 11.0
Little bluestem Pastura, Cimmarron up to 10 3.5 7.0
Buffalograss Texoka, Sharps Improved up to 10 Bur: 8.0 Bur: 16.5
Floret: 3.0 Floret: 6.0
Yellow Indiangrass Llano, Holt, Cheyenne, Oto up to 10 5.0 10.0
RANGE SITE: Gravel Breaks, Loess Breaks, Sandstone Breaks
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX DRYLAND IRRIGATE
D
Sideoats grama Vaughn, Butte, Niner, 20 to 45 4.5 9.0
El Reno, Haskell
Little bluestem Pastura, Cimmarron 10 to 35 3.5 7.0
Western wheatgrass Arriba, Barton, Rosana 10 to 20 8.0 16.0
Blue grama Hachital, Lovington 5 to 15 1.5 3.0
Switchgrass Grenville, Nebraska 28, up to 20 2.5 4.5
Blackwell, Pathfinder
Prairie sandreed Goshen up to 20 3.5 6.5
Yellow Indiangrass Llano, Holt, Cheyenne, Oto up to 20 5.0 10.0
Big bluestem Kaw up to 20 5.5 11.0
Needleandthread up to 15 7.5 15.0
Indian ricegrass Paloma up to 10 6.0 12.5
RANGE SITE: Shaly Plains, Alkaline Plains, Salt Flat, Salt Meadow, Saline Overflow
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX
DRYLAND IRRIGATE
D
Western wheatgrass Arriba, Barton, Rosana 30 to 45 8.0 16.0
Sideoats grama Vaughn, Butte, Niner, 20 to 40 4.5 9.0
El Reno, Haskell
Alkali sacaton Salado 10 to 35 1.0 1.5
Switchgrass Grenville, Nebraska 28, up to 20 2.5 4.5
Blackwell, Pathfinder
Blue grama Hachital, Lovington up to 15 1.5 3.0
Yellow Indiangrass Llano, Holt, Cheyenne, Oto up to 10 5.0 10.0
Big bluestem Kaw up to 10 5.5 11.0
RANGE SITE: Overflow
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX
DRYLAND IRRIGATE
D
Western wheatgrass Arriba, Barton, Rosana 30 to 45 8.0 16.0
Green Needlegrass Vaughn, Butte, Niner, 10 to 30 5.0 10.0
El Reno, Haskell
Switchgrass Grenville, Nebraska 28, 10 to 20 2.5 4.5
Blackwell, Pathfinder
Big bluestem Kaw 5 to 20 5.5 11.0
Yellow Indiangrass Llano, Holt, Cheyenne, Oto 5 to 20 5.0 10.0
Blue grama Hachital, Lovington up to 10 1.5 3.0
RANGE SITE: Wet Meadow
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX
DRYLAND IRRIGATE
D
Switchgrass Grenville, Nebraska 28, 15 to 30 2.5 4.5
Blackwell, Pathfinder
Yellow Indiangrass Llano, Holt, Cheyenne, Oto 15 to 30 5.0 10.0
Big bluestem Kaw 15 to 30 5.5 11.0
Prairie Cordgrass 15 to 30
Little Bluestem Pastura, Cimmarron up to 10 3.5 7.0
Western wheatgrass Arriba, Barton, Rosana 10 to 20 8.0 16.0
Slender wheatgrass San Luis up to 10 5.5 11.0
RANGE SITE: North of Highway 14
COMMON NAME RECOMMENDED % IN SEEDING RATE
VARIETIES MIX
DRYLAND IRRIGATE
D
Western wheatgrass Arriba, Barton, Rosana 30 8.0 16.0
Blue grama Hachital, Lovington 30 1.5 3.0
Sideoats grama Vaughn, Butte, Niner, 30 4.5 9.0
El Reno, Haskell
Buffalograss Texoka, Sharps Improved 10 Bur: 8.0 Bur: 16.5
Floret: 3.0 Floret: 6.0
20. Add the following as the last two bulleted items of Section 4.5 Mulching:
"• At least 70 percent (%) of the mulch by weight shall be ten (10)
inches or more in length.
• The appropriate use of fabric blankets under trees and shrubs is
suggested."
21. Amend Section 5.0 Post-Construction Monitoring to read:
"Monitoring is necessary to check the status of revegetation work and to
implement any follow-up measures needed, such as mowing,weed control,
watering, overseeding, etc. This is especially important for establishing
native species since it may take scv,.., ycai°three to five years for
vegetation to become adequately established. Sites should be observed
several times during their first two to three growing seasons and at least
aneetwice a year thereafter. The guidelines in Section 3.4 should be
followed.
Design Examples - Weld County does not have specific values to use for
the C1, C2, and C3 coefficients within the "Detention Volume by Modified
FAA Method" spreadsheet. Please use the Urban Drainage and Flood
Control District (Denver area) values."
Section 8-11-50. Weld County Addendum to the Text of the Urban Storm Drainage Criteria-
Volume 3
A. Chapter 2 - New Development Planning
1. Amend Section 1.2 Four-Step Process, portion titled "Step 3", second
paragraph to read:
"Constructed Grass, Riprap, or Concrete-Lined Channel. This method of
channel stabilization has been in practice for some time; it is described in
Volume 2 of the Manual. The water quality benefit associated with these
channels is the reduction of severe bed and bank erosion that can occur in
the absence of a stabilized channel. On the other hand, the hardlined low
flow channels that are often used do not offer much in the way of water
quality enhancement or wetland habitat. The Urban Drai1raga and RIAU
Control D;0l,ktWeld County does not recommend the use of riprap or
concrete lined flood conveyance channels, but does recommend the use of
low-flow channels lined with soil-riprap."
2. Add the following to the last paragraph of Section 1.3 Other BMPs: "Weld
County will consider and allow use of new, innovative BMP technologies
upon review of the proposed BMP(s) on a case by case basis."
3. Amend second paragraph of Section 1.5.4 Guidance for Selecting and
locating WQCV Facilities to read:
"Laying out WQCV facilities within a development site and watershed
requires thought and planning. Often, this decision-making occurs during
a master planning process undertaken by twal JU.;OJk1/4.l;U,IS 0,,J tlm.
DistrictWeld County. Outfall system plans and other reports may depict a
recommended approach for implementing WQCV on a watershed basis.
Such reports may call for a few large regional WQCV facilities, smaller sub-
regional facilities, or alternatively an on-site approach. It is always a good
idea to find out if a master planning study has been completed that
addresses water quality and to attempt to follow the plan's
recommendations."
4. Add the following to the last paragraph of Section 1.5.5 Incorporating
WQCV into Stormwater Quantity Detention Basins: "Weld County requires
that the 100-year detention volume be provided for a given site and allows
the WQCV to be incorporated within the 100-year volume."
B. Chapter 3 - Structural BMP'S
1. Amend third paragraph of Section 6.4 Design Considerations to read:
"Perforated outlet and trash rack configurations are illustrated in the
TYPICAL STRUCTURAL BMP DETAINS AND SPECIFICATIONS chapter.
Figure EDB-3 equates the WQCV that needs to be emptied over 40 hours,
to the total required area of perforations per row for the standard
configurations shown in that section. The chart is based on the rows being
equally spaced vertically at 4-inch centers. This total area of perforations
per row is then used to determine the number of uniformly sized holes per
row (see detail in the TYPICAL STRUCTURAL BMP DETAINS AND
SPECIFICATIONS chapter). One or more perforated columns on a
perforated orifice plate integrated into the front of the outlet can be used;
however, the fewer the number of columns, the better, maximizing the size
of the orifice. Using least number of columns and the largest possible
orifice, reduces clogging possibilities. Other types of outlets may also be
used, provided they control the release of the WQCV in a manner consistent
with the drain time requirements and are approvedaccepted in advance by
the DistrictWeld County."
2. Add the following to Section 9.0 Retention Pond (RP) - Sedimentation
Facility: "Retention facilities are normally not allowed in Weld County, but
will be considered by Weld County for special circumstances. Retention
facilities shall be sized to contain a volume equal to twice the 100-year
storm runoff volume plus one foot of freeboard. Water within a retention
facility shall be mechanically removed and disposed of off-site by the
property owner within 48 hours after a storm event."
C. Chapter 4 - Typical Structural BMP Details
1. Amend Table 1 as follows:
Table 1—Typical Notes For EDB,RP and CWB Outlet Structures
1. The details shown herein are conceptual design in nature. Preparation of final design plans that
address details of structural adequacy.excavation.foundation preparation,concrete work,
reinforcing steel.backfll.metalwork,and appurtenances, including preparation of technical
specifications.are the responsibility of the design engineer in charge of the project.
2. Alternate designs to the typical outlet structures shown herein may he considered:however,
alternate designs must address the hydraulic and trash handling functionalfeatures and insert ter
the structures shown in this Manual.
3. WingwaNs shown herein are designed to have the structure to be backfdled to be flush with the
side slopes of the basin. The use of this geometry is recommended and permits the structure to
blend into the landscape most aesthetically.Other geometries may be considered,however they
need to be developed with ful consideration of public safety.aesthetics.maintainabiity.aid
function. The superiority of these design should be demonstrated te be equal to or better than the
design concepts shown in this Manual.
4. Permanent Water Surface refers to the water surface of the micro-pool for Extended Detention
Basins and the permanent pool for Constructed Wetland Basins and Retention Ponds.
5. Perforated orifice plate shown herein is used to provide the specified the drain timed the WQCV.
To reduce clogging potential,t is recommended that the largest possible circular opening be
selected to minimize the number of columns. The intent is to have an outlet that empties the
WQCV in the time specified(e.g., 12-.24-or 40-hours),and being within-3%to 5%of Ns time is
considered acceptable. See Figure 4 for orifice design information.
6. Vertical Trash Rack option is preferred;however,an Adverse-Slope Trash Rack is also
acceptable.Both help to shed the accumulated trash as the water level after the storm recedes.
The used a Continuous-Slope Trash Rack for WQCV outlets is not recommended.See Figure 6
for trash rack design information.
7. Drainage or flood control detention above the WQCV may be sized for any storm event specified
by loci st rn,water criteria and not only to the 2-or 10-year events shown herein.
8. Underdrains along the perimeter of the permanent pool.inducing a shutoff valve,are
recommended for Constructed Wetland Basins and a Retention Ponds to help dewater the pool for
rehabiitative maintenance.
9. When the outlet designs differ from those shown herein:
a) Provide needed orifices that are distributed over the vertical height of the WQCV.with the invert
of the lowest orifice located at Z-6".or more above the bottom of the micro-pool and above the
bdlorn of Retention Ponds and Constructed Wetland Basins.
b) Provide full hydraulic calculations demonstrating that the outlet will provide the minimum
required drain time of the Water Quality Capture Volume for the BMP type being used.
c) Outlet openings(orifices)shall be protected by trash racks having a minimum net open area
specified in Fig 7. All opening dimensions shall be less than any dimension of outlet openings.
d) Trash racks shall be manufactured from stainless steel or aluminum aloy structurally designed
to not fail under a full hydrostatic bad on the upstream side and assuming zero backwater
depth on the downstream side.
Urban Drainage and Typical Outlet Structure General Notes
Flood Control District for Extended Detention Basin,
Drainage Criteria Manual(V.3) Retention Pond and Constructed Wetland Basin Outlets
a. "8. Underdrains alortgaccessible from the perimeter of the
permanent pool,including a shutoff valve,are recommended
for Constructed Wetland Basins and a Retention Ponds to
help dewater the pool for rehabilitative maintenance."
2. Delete, in its entirety, Figure 1 - Typical WQCV Outlet Structure Profile,
Including 100-year Detention.
Nets: Sae 2- through 100-year overflow
trot reeks with the Sd of figure 7.
Overtopping
9� yy Protection
ErCergr Rf eeds wf Outlet Ier
of Trot Rock
1 DO-YR or Larger Flood Water Surface s
_WOCY Water Surfoe w. Fitted Grade
Hem (Sei gun 4 - ►,�
Permanent Wet.
Surfeit _ �aa� a_� I 100-YR Orifice
1 (Sei Flh Ru S) �w■1 :. Cmtrd Outlet
flat Pea _ 120% of 100-YR Capacity
` Vndereom lywrM
litre-Pod (Gptonal)
iron BOK (tut let Lint Ion
Owtonna
Merit did Emergency Protection
Spillway
100-YR or Larger Flood Wets Surface
MOCV Water SSICOe T ��
Orifice Plat ' as
Hi (See Figure 4 i.
r an 1 Perm
anent Water 34 10—YR OttePe
■ Central outlet
Treeh R•- ■� — — - --
re I ■� I Ootlet Plpe — 120ft of 10—YR Capacity
y-r - .-• .-• _ _ nderdmin Around
Micro—Pool (Optional)
Overtopping Spillway Option
Urban Drainage and Figure 1
Flood Control Ohrlrlet Typleal W0CV Outlet Stnrture Profiles
Menage CAterfe Manuel (V.3) Including 100—Ye. Detention
M WISNI inns
Figure 1—Typical WOCV Outlet Structure Profile,Including 100-year Detention.
3. Amend Figure 2 as follows:
Nett Size 2— through 100—yer awfew
trash rooke with the aid of figure 7. OvertoPPM
Emergney Splway Protection
100—YR or Larger flood Detntfen ter r.u9r Floodu
Owrtlow with Trash Rock
2— to 10—YR Detention
Overflew with Trash Rack
100—YR t Lrg lit od 'lSl-tir Surface `
2=to 10—YR Water S1gp—i- — Finished Grade
SW/ Water Surface __ r
a
Knaa11 Surmanent rfacea Water I Central OutletOuutlletYR o
reel ,.k - —
WO , auttr Poe - UM of 1t10-Yw comity
P.'..•-:.Orifice Plot
(Sae Figure 4
2- to 10-YR Orifice
Ilnerbalf� u Control Outlet
MIcro-Pool (Oplbtid)
Drop Box Outlet Option
100-YR or Larger O topping
Pr
Flood Spflwoy Protection
2- to 10-YR Detention Outlet with Trash Rock
100-YR or Larger Flood Water axiom
_
2-19 -YR 10 IME Burg 1,- - Th.,
WptCLLML1aw9_ _;
lkeser Permanent Water1CV
.� 2- to 10-YR otfk:e
Surface Z : Cntrol Outlet
roe
Dune Pt - 1Z o _ - Capacity
Orifice Hot* 0 �/all�t�n
(Sea Rime 4) pattern
(Optfad)
Overtopping Spillway Option
Urban Drainage and Figura 2
Flood Control District
Tlplad MOCV flutist Structure Prelim
Drainage Criteria Manual (V3) Including 2- to 10-Yea and 100-Yer Detention
.-WAS eraar
Figure 2—Typical WOCV Outlet Structure Profile.Including 2-to 10-year and 100-year Detention.
a. Delete the Overtopping Spillway Option from Figure 2.
b. Change "Outlet Pipe = 120% of 100-YR Capacity" within the Drop
Box Outlet Option to"Outlet Pipe= 100%of 100-YR Capacity"within
the Drop Box Outlet Option.
4. Amend Figure 2-a as follows:
Not Sin 2- through 1o0-yer avreow
trash rooks with to aid of Faure 7. soy O.rtopp
ing
100-`R or Lager Flood Detention E;gt ayN p�y'r"�' Piot.atian
Overflow with Trot Rock
2- to 10-YR Detention
Overflow with Trot Rock
100-YR or Lugar Flood Water Surf non
2=to tilt tar Sumac.—s .�1� Finished Grade
1tVCV Water Surface 7] 44
al
Nxga� iceg Water 11 1 CO0-YR Orifice
ontrol Outlet
s rash ck - —
�r See •um 6 �• ' Ott Pipe - 1202 of 100-Ye Ceoodty
-
Orifice Plate
(See Flpee 4)
2- to 10-YR Orifice
p�rry�g Control Outlet
Nicrron Poole Iptknd'
Drao Box Cutlet Option
I1:0-YR or Larger Overtopping
Flood Spillway Pretanttan
2- to 10-YR Detention GlattGlattwith Trot Rack
100-YR ea Laser deed Water Sumo.. )�
2- to lank 5Wt�Swf_gg-rt
WVCV Altar Suitea - 4-P Gr4Hagry Defaces Control Ott
o t attar 1 ASP 10-YR critic.Trek:
Qat Pipe = 12016 a 10- spacer
• Iflca Plata
(Sae Figure 4) Undadrain gArrand
Mlero-Pool (0ptlond)
Overtopping Spillway Option
Urban Drainage and Flours 2-a
Flood Control District Alternate
Drainage Criteria Manual (V.3) Typical WOCV Outlet Structure Prongs
„`seas,twin" Including 2- to 1D-War and 100-Year Detention
Figure 2-a--Typical WOCV Outlet Structure Profile,Including 2-to 10-year and 100-year Detention.
a. Delete the Overtopping Spillway Option.
b. Change "Outlet Pipe = 120% of 100-YR Capacity" within the
Drop Box Outlet Option to "Outlet Pipe = 100% of 100-YR
Capacity" within the Drop Box Outlet Option".
D. Chapter 5 - Maintenance Recommendations
1. Add the following introductory paragraph prior to Section 1 Grass Buffer:
"Weld County will require that all submittals include an Operations and
Maintenance manual for all water quality and detention pond facilities. The
operations and maintenance manuals shall also be distributed to the
applicable Homeowners' Association and/or business park association (or
equivalent). The operations manuals will include instructions on safe and
correct operations, repair, and maintenance of all installed equipment and
facilities and recommended inspection schedules."
E. Chapter 6 - Industrial and Commercial Best Management Practices
1. Add the following introductory paragraph under Section 1.0 Introduction:
"Weld County will require that all submittals include an Operations and
Maintenance manual for all industrial and commercial water quality and
detention pond facilities. The operations and maintenance manuals shall
also be distributed to the applicable business park association (or
equivalent). The operations manuals will include instructions on safe and
correct procedures for the operation, repair,and maintenance of all installed
equipment and facilities. The manuals shall provide recommended
inspection schedules."
2. Amend Section 5.0 Structural Controls, Table IC-1 as follows:
Table IC-1-supgaswd Structural Controls
Control Sources Applicability
Grass Buffer Parking Areas Applicable to Industrial and
Commercial Operations
Grass Swale Parking Areas Applicable to Industrial and
Commercial Operations
Modular Block Parsons Parking Areas Applicable to Industrial and
Pavement Commercial Operations
Pavement Micro-Detention Parking Areas Applicable to Industrial and
Commercial Operations
Landscape Micro-Detention Parking Areas Applicable to Industrial and
Commercial Operations
Extended Detention Basin Parking Areas Applicable to Industrial and
Commercial Operations
Constructed Wetlands Parking Areas Applicable to Industrial and
Commercial Operations
Retention Pond All Sources Associated with Industrial or
commercial operations with storage of
large quantities of toxic pollutants.
Constructed Wetlands Parking Areas Applicable to Industrial and
Channel Commercial operations
Spill Containment and Liquid Storage,Washing. Applicability to all Industrial and
Control(Containment Manufacture,Outside Storage, Commercial operations
Diking.Curbing.Installation Waste Management,Fueling
of spill and overflow Areas.Loading and Unloading
protection)
Covering of Storage/ Fueling Areas.Loading and Applicability to all Industrial and
Handling Facilities Unloading,Liquid Storage, Commercial operations
Material Storage,Outside
Manufacturing.Waste
Management
a. Delete"Retention Pond"and replace with "Spill Containment Area."
F. Chapter 8 - Construction Best Management Practices
1. Amend the second paragraph of Section 1.1 General to read:
"An Erosion and Sediment Control Plan must be developed and submitted
to ti ickbal jui;oJ;ction to ul,ta;r, a adonstructi„r yr 0;tc y,aJit,y pen ,;tWeld
County to obtain a grading permit or a building permit. Site planning and
drainage planning should, whenever possible, occur concurrently with site
grading and erosion control planning. When site grading precedes final
development, an erosion and sediment control plan for site grading must be
submitted. This plan may have to be modified at the time a final site
development plan is prepared. This modified plan must be submitted for
review and approval prior to final development."
2. Amend Section 1.3 Erosion and Sediment Control Plan to read:
"An Erosion and Sediment Control Plan consisting of a written narrative
report and a site plan map must be submitted to the appropriate louaf
governmentWeld County for review and approvalacceptance. Figures C-1
and C-1A provide standard symbols that can be used on such plans. An
example plan is given in APPENDIX B. The written narrative report can be
a subsection within the drainage report. The erosion and sediment control
plan must include specific inspection and repair/maintenance requirements.
3. Amend paragraph #16 of Section 1.3.1 Narrative Report to read:
"16. The following note - "This Erosion and Sediment Control Plan has
been placed in the( 'sort name of local juriOJiulio,r)Weld County file
for this project. The plan appears to fulfill the Urban D.a,,'aye alit}
flood Co,Maul Di0trict,tcul...ivalWeld County criteria Al pi tl,L,%,,,te,
for erosion control and requirements of ("sot ',awe of IOuaf
jurisdiction). I understand that additional erosion control measures
may be needed if unforeseen erosion problems occur or if the
submitted plan does not function as intended. The requirements of
this plan shall run with the land and be the obligation of the land
owner until such time as the plan is properly completed, modified or
voided."
4. Amend paragraph 3.m of Section 1.3.2 Site Plan to read:
"m. The following note: "This Erosion and Sediment Control Plan has
been placed in the(ii.sort..an,e of locaFjurisJiulio.r)Weld County file
for this project and appears to fulfill applicable erosion control
criteria. I understand that additional erosion control measures may
be required of the owner and his or her agents due to unforeseen
erosion problems or if the submitted plan does not function as
intended. The requirements of this plan shall run with the land and
be the obligation of the land owner until such time as the plan is
properly completed, modified or voided."
5. Replace the current text of Section 1.3.3 Approval of Erosion and Sediment
Control Plan with the following:"A,,C,esu,and3eJiment Control Plan must
Uc approved pi,ur-lu iOOUanw of Oil C)v..Ilot Grading o. Site Mato,tLan ,.
Per,nit by the city or county. The f,.a1 C,0J,0l, a,id Sediment Control Plait
r..ust be uo..afotc..t witl. a D,a;naye Rur,ort consiJ.,.0 -tbe ,t..l,l., to tl�..
a F,F,.VVllty jU.IJJ14 Rill. A1.,1.,, al .,f tl,e E1 0iun anal S4J1nlcl.t C 1,.t.ul 1 la.r
does not imply acceptance or approval of Drainage Plans, Utility Plans,
Gt.eet or Road Ma,,s, Dcsigr.ofi2utah 0, a.,y ot1, , oJNuut-,f-situ
Jcvelupn.cnt."An Erosion and Sediment Control Plan must be accepted
prior to issuance of a grading permit or a building permit. The final Erosion
and Sediment Control Plan must be consistent with the Drainage Report.
Approval of the Erosion and Sediment Control Plan does not imply
acceptance or approval of Drainage Plans, Utility Plans, Street or Road
Plans, or any other aspect of site development."
6. Amend Section 1.3.4 Exemptions and Variances to read:
"A provision for exemptions and variances may be provided by a city or
Leant/Weld County. These are generally processed according to the
applicable subdivision regulations and reviewed on a case-by-case basis."
7. Amend paragraph 1.b of Section 1.3.4 Exemptions and Variances to read:
"b. Grading or an excavation below finished grade for basements,
footings, retaining walls, or other structures ui r plots/Jvr rod R1 R3
of less than five(5)acies in sizewhere the disturbed area will be less
than one (1) acre in size unless required otherwise."
8. Amend paragraph 1.d of Section 1.3.4 Exemptions and Variances to read:
"d. Land-disturbing activities involving less than five (5) acresone (1)
acre of disturbed area. Individual lots involving less than fire (5)
able$Une (1) acre of disturbed area in a larger subdivision project
shall not be considered separate development projects, but rather
as a part of the subdivision development as a whole. It will be the
responsibility of the homeowner or homebuilder to conform to all
requirements of the fu,,ally app roviUlocally-accepted Erosion and
Sediment Control Plan for the subdivision. As part of any Building
Permit for which a specific erosion control plan is not required, the
following statement must be included: "We have reviewed the
Erosion and Sediment Control Plan for (subdivision name) and
agree to conform to all requirements contained therein and all
erosion control requirements of the(insert name of local jurisdiction).
We further agree to construct and maintain all erosion and sediment
control measures required on the individual lot(s) subject to this
Building Permit and/or in accordance with the provisions of the
Erosion Control section of the Manual of the Urban Drainage and
Flood Control District."
9. Amend paragraph 1.h of Section 1.3.4 Exemptions and Variances to read:
"h. Where the owner certifies in writing to it, .al jai Weld County
and thy juiradrk.liu.Weld County agrees, in writing, that the
planned work and the final structures or topographical changes will
not result in or contribute to soil erosion or sedimentation and will not
interfere with any existing drainage course in such a manner as to
cause damage to any adjacent property or result in the deposition of
debris or sediment on any public way, will not present any hazard to
any persons or property,and will have no detrimental influence upon
the public welfare or upon the total development of the watershed."
10. Amend paragraph 2 of Section 1.3.4 Exemptions and Variances to read:
"2. Variances - Cities and counties may consider waiving or modifying
a,.y uf tl ;Lila v1 delrarto k...,l iCApp,upriate or too rt..,t,hat;in,
for site conditions by granting a variance. Variances may be granted
at the time of plan submission or request for plan revision.
Va,iank,cs must be request0d act.,ortJa,n,e with the suLdivOk,,r
rcyulat,u,is and ,gust darra-The Weld County Engineer may grant
variances from the criteria of the Construction Best Management
Practices chapter by his/her acceptance of the Final Drainage
Report in which the variance request is well documented."
11. Amend the fourth bulleted item under Section 2.2 Summary of Criteria to
read:
• Revegetation. A viable vegetative cover should be established
within one year on all disturbed areas and soil stockpiles not
otherwise permanently stabilized. Vegetation is not considered
established until a ground cover is achieved which, in the opinion of
the city a, cow.ty of jurisJicl o1MWeld County, is sufficiently mature
to control soil erosion and can survive severe weather conditions.
(Section 3.3)."
12. Amend the 22nd bulleted item under Section 2.2 Summary of Criteria to
read:
• Disposition of Temporary Measures. All temporary erosion and
sediment control measures shall be removed within 30 days after
final stabilization is achieved, or after the temporary measures are
no longer needed,whichever occurs earliest,or as authorized by the
city or county of local jurisdictionWeld County. (Section 8)."
13. Amend the second paragraph of Section 2.4.2 Stormwater Quality Plans to
read:
"Whore local ,ogulations have not been developed, sStormwater quality
plans should be developed consistent with the guidelines in the
STORMWATER QUALITY MANAGEMENT and BMP PLANNING FOR
NEW DEVELOPMENT AND REDEVELOPMENT chapters of Volume 3 of
the Manual."
14. Amend the second paragraph of Section 3.3.2 Temporary Revegetation to
read:
"To provide temporary vegetative cover on disturbed areas which will not be
paved,built upon,or fully landscaped within 12 months but will be completed
within 24 months, plant an annual grass appropriate for the time of planting
and mulch the planted areas. The annual grasses generally suitable for the
1% ver. ,ot,e1ofta. cooaWeld County are listed in Table C-2. These are to
be considered only as a general recommendation whenever specific design
guidance for a particular site is not available."
15. Amend the second paragraph of Section 4.1 Vehicle Tracking to read:
"For sites greater than two (2) acres, a stabilized vehicle tracking control
must be constructed(see Figure C-8).Whenever deemed necessary by the
t•ay jai Weld County, wash racks shall be installed to
remove mud and dirt from the vehicle and its tires before it enters onto
public roads (see Figure C-8A)."
16. Amend the first paragraph of Section 4.3.3 Sediment Basins to read:
"Areas draining more than 1 acre must be routed through a sediment basin
similar to one shown in Figures C-15, C-15A, and C-16. Sediment basins in
tho Do,,ror eyki,Weld County shall be designed to a minimum 1,800 cubic
feet of volume per tributary acre and shall be cleaned out prior to becoming
half full."
17. Amend the last paragraph of item #2 under Section 5.1 Working Within or
Crossing a Waterway to read:
"A permit is required for placement of fill in a waterway under Section 404
of the Clean Water Act. The U.S. Army Corps of Engineers has issued
nationwide general permit Number 14 for Minor Road Crossing Fills. This
is defined as placement of less than 200 cubic yards of fill material below
the plane of ordinary high water. The local office of the Corps should be
contacted about the requirements for obtaining a 404 permit. The city v.
Lou.Ay of juli0Jktiv..Weld County should also be consulted and can provide
assistance. A further discussion on the need for 404 permits is included in
Section 2.1, MAJOR DRAINAGE, of the Manual."
18. Amend the first paragraph of Section 5.3 Outlet Protection to read:
"To protect adjacent downstream properties from erosion due to
concentrated flows, a stable outlet or channel is necessary. If there is no
stable outlet, one may have to be constructed. In lieu of constructing a
temporary or permanent outlet to the storm drainageway system,temporary
total retention of the runoff fi L...a 24-I,our, 100-ycar ster......ay be provided.
Writtc.. app.oval by-thc local city a. county .Host Lc vLtai..ed f ta}
rctee IL.. of atv....watc.may be considered on a case-by-case basis upon
acceptance from Weld County."
19. Amend Section 8.0 Disposition of Temporary Measures to read:
"All temporary erosion and sediment control measures shall be removed and
disposed within 30 days after final site stabilization is achieved, or after the
temporary measures are no longer needed,whichever occurs earliest,or as
authorized by thy a,ity or county of local j1J.i0Ji II (Weld County and
applicable coordinating agencies (CDOT, CDPHE). For example, a site
containing only one building will have temporary erosion control measures
removed after building construction is complete and final landscaping is in
place. Temporary erosion control measures may be removed from a
commercial construction site or residential subdivision only after streets are
paved and all areas have achieved final stabilization. Trapped sediment and
disturbed soil areas resulting from the disposal of temporary measures must
be returned to final plan grades and permanently stabilized to prevent
further soil erosion. The Profcos;oi.al Cnyh.ccr-preparn.g tl.e c.vakvi rat Ill
sediment control plan shall submit, as part of the narrative report, a
Lt.Julc of.ha...� �I J.d�a foe t.....porary cont.vl .en uaue Tie 3chedul.
1.‘..,u1,1 La a.v..aiatent with key bol.slroc.tio.. pl eases such as st.ect Na„i..y,
filled atabiliation of disturbed a,caa, u. i..atallativ..of structural sty,...watce
Lunt,ola. The Professional Engineer preparing the construction phase
erosion and sediment control plan shall obtain the approval of Weld County
before removal of any temporary measures."
20. Amend the second paragraph of Section 9.0 Maintenance to read:
"The P.ofcsaienal C..g;..ee. preparing the crvsio..and aeJi...ent control plait
shall submit, as part of the narrative report, a schedule of planned
maintenance activities for temporary and permanent erosion and sediment
control measures. The schedule should be consistent with the level of
..ea ,,tcnance required for tl.e bo.It.uI II easures plvpvat,d i.e tic pia,r.The
Professional Engineer preparing the permanent erosion and sediment
control plan shall submit a schedule of planned inspection and instructions
for operations and maintenance for all installed permanent erosion and
sediment control measures. The plan shall include identification and
specifications (size, materials, etcetera) of parts and equipment potentially
needing repair or replacement over the life of the installed measures. A
copy of the inspection schedule and instructions for operations and
maintenance shall be provided to the applicable Homeowners' Association
or Business Park management(or equivalent)."
21. Add Section 10.0 Erosion and Sediment Control Warranty to read: "Prior to
acceptance and approval of all installed permanent erosion and sediment
control measures,Weld County will require that the owner shall warrant the
measures shown on the approved erosion and sediment control plan are
properly constructed, installed, and are free from defective materials and/or
defective workmanship."
Section 8-11-60. Enforcement responsibility.
It shall be the duty of the Weld County Department of Public Works to interpret and enforce
the provisions of the Weld County Storm Drainage Criteria using the following guidelines:
A. In the interpretation and application, the provisions of the Weld County Storm
Drainage Criteria shall be held as the minimum requirements for promotion of the
health, safety, and general welfare of the community.
B. The Weld County Storm Drainage Criteria is not intended to interfere with,
abrogate, or annul any other regulation, statute, or other provision of law.
C. Where any provision of the Weld County Storm Drainage Criteria imposes
restrictions different from those imposed by any other provisions of the Weld County
Storm Drainage Criteria, or any other regulation or provision of law, that provision
which is more restrictive or imposes higher standards shall govern.
D. The Weld County Storm Drainage Criteria is not intended to abrogate any
easement, covenant, or any other private agreement or restriction, provided that
where the provisions of the Weld County Storm Drainage Criteria are more
restrictive or impose higher standards or requirements than such easement,
covenant, or other private agreement or restriction, the provisions of these
regulations shall govern.
Division 2
Drainage Planning Submittal Requirements
Section 8-11-100. Review process.
All new developments and subdivisions within the jurisdiction of the Weld County Storm
Drainage Criteria shall submit drainage reports, construction drawings, and existing condition and
as-built information in accordance with the requirements of this Article.
Section 8-11-110. Sketch Plan Drainage Report.
The purpose of the Sketch Plan Drainage Report, submitted at the Sketch Plan Review
stage of the Planning Review process, is to identify and define conceptual solutions to storm
drainage problems which may occur on-site and off-site as a result of the proposed development.
In addition, those problems that exist on-site prior to development must be addressed during the
conceptual phase. For proposed projects that will have rural levels of development, the
Department of Public Works will review the site, surroundings, and proposed improvements and
advise the applicant as to what additional information, and/or engineering design may be required
for Change of Zone and Final Plat approvals.
A. All reports shall be typed on 8.5-inch by 11-inch paper and bound. Drawings
measuring 24 inches by 36 inches may be included,as needed. The drawings shall
be bound within the report or included within a pocket attached inside the back
cover of the report. The report needs to stand-alone, therefore, all important
reference material and supporting documents and calculations should be copied
and included within the report appendix. The report shall include a cover letter
presenting the conceptual design for review and shall be prepared or supervised by
an engineer licensed in Colorado. Only original documents sealed in ink will be
accepted. The sealed report shall contain a certification sheet as follows:
1. "I hereby certify that this report for the conceptual drainage design of(Name
of Development) was prepared by me (or under my direct supervision) in
accordance with the provisions of the Weld County storm drainage criteria
for the owners thereof."
Registered Professional Engineer
State of Colorado No.
(Affix Seal)
B. Sketch Plan Drainage Report Contents. Sketch Plan Drainage Reports shall be
prepared in accordance with the following outline and contain the applicable
information listed:
1. General Location and Description.
a. Location.
1) Township, Range, Section, Quarter Section.
2) Local streets within, and adjacent to, the development.
3) Major open channels, lakes, streams, irrigation and other
water resource facilities within and adjacent to the proposed
development.
4) Names of surrounding developments including jurisdictions
(municipalities).
b. Description of Property
1) Area in acres.
2) Ground cover.
3) Major open channels and ownership.
4) General project description.
5) Irrigation facilities and ownership information.
6) Groundwater characteristics (where applicable).
2. Drainage Basins and Sub-Basins.
a. Major Basin Description.
1) Reference to applicable Weld County or adjacent county
Master Drainage Plan(s).
2) Major basin drainage characteristics.
3) Identification of all irrigation facilities within 200 feet of the
property boundary.
4) Identification of all FEMA-defined 100-year floodplains and
floodways affecting the property.
b. Sub-Basin Description.
1) Historic drainage patterns on the subject property and
adjacent properties.
2) Off-site drainage flow patterns and impacts on the subject
property.
3. Drainage Facility Design.
a. General Proposed Concept.
1) Proposed concept and typical drainage patterns.
2) Compliance with off-site runoff considerations and
constraints.
3) Anticipated and proposed drainage patterns.
4) Identify all requests for variance from Weld County Storm
Drainage Criteria.
b. Specific Details.
1) Describe design storms and source of design storm depth
information (NOAANational Oceanic and Atmospheric
Administration Atlas, Urban Drainage and Flood Control
District maps, etcetera).
2) Drainage problems encountered and proposed solutions at
specific locations.
3) Maintenance access and aspects of the proposed design.
C. Sketch Plan Drainage Report Drawing Contents.
1. A General Location (vicinity) Map shall be provided at a scale of 1" =2000'
or larger in sufficient detail to identify upstream off-site drainage areas
flowing into the proposed development and general drainage patterns.
2. A Drainage Plan of the proposed development shall be provided at a scale
from 1" = 100'or 1" = 200'on a 24"x 36"drawing. The plan shall show the
following information:
a. Existing contours at 2-foot maximum intervals, contours should
extend at least 200 feet from all project boundaries, or further if
necessary, to show upstream and downstream drainage
relationships impacting the proposed development.
b. Property lines, existing and proposed lot lines, and existing and
proposed easements.
c. Streets with names.
d. Existing drainage facilities, pipes, structures, irrigation facilities, and
sizes.
e. Overall drainage area boundary and sub-area boundaries.
f. Proposed flow directions using arrows.
g. Conceptual location of storm sewers, swales, open channels,
culverts, detention ponds, and other appurtenances.
h. Identification of outfall locations and receiving waters.
Location of all defined 100-year floodplains affecting the property.
j. Any other items so noted within the Drainage Report.
Section 8-11-120. Change of Zone Drainage Report.
The purpose of the Change of Zone Drainage Report is to identify and define preliminary
solutions to problems which may occur on-site and off-site as a result of the proposed
development. In addition, those problems that exist on-site prior to development must be
addressed during the preliminary phase.
A. All reports shall be typed on 8.5-inch by 11-inch paper and bound. Drawings
measuring 24 inches by 36 inches shall be included,as needed. The drawings shall
be bound within the report or included within a pocket attached inside the back
cover of the report. The Change of Zone Drainage Report needs to stand-alone,
therefore, all important reference material should be copied and included within the
report appendix. The report shall include a cover letter presenting the preliminary
design for review and shall be prepared or supervised by an engineer licensed in
Colorado. Only original documents sealed in ink will be accepted. The sealed report
shall contain a certification sheet as follows:
1. "I hereby certify that this report for the preliminary drainage design of(Name
of Development) was prepared by me (or under my direct supervision) in
accordance with the provisions of the Weld County storm drainage criteria
for the owners thereof."
Registered Professional Engineer
State of Colorado No.
(Affix Seal)
B. Change of Zone Drainage Report Contents. The Change of Zone Drainage Report
shall be in accordance with the following outline and contain the applicable
information listed:
1. General Location and Description.
a. Location.
1) Township, Range, Section, Quarter Section.
2) Local streets within, and adjacent to, the development.
3) Major open channels, lakes, streams, irrigation and other
water resource facilities within,and adjacent to,the proposed
development.
4) Names of surrounding developments including jurisdiction
(municipalities).
b. Description of Property.
1) Area in acres.
2) Ground cover.
3) Major open channels and ownership.
4) General project description.
5) Existing irrigation facilities and utilities and ownership
information.
6) Groundwater characteristics (where applicable).
2. Drainage Basins and Sub-Basins.
a. Major Basin Description.
1) Reference to Weld County Master Drainage Plan(s) where
applicable.
2) Major basin drainage characteristics.
3) Identification of all irrigation facilities and utilities within
200 feet of the property boundary.
b. Sub-Basin Description.
1) Historic drainage patterns on the subject property.
2) Off-site drainage flow patterns and impacts on the subject
development.
3. Drainage Design Criteria.
a. Regulations: Discussion of the optional criteria selected or the
deviation from the Weld County Storm Drainage Criteria, if any.
b. Development Criteria Reference and Constraints.
1) Discussion of previous drainage studies(i.e., project master
plans) for the subject property that influence, or are
influenced by, the proposed drainage design and how the
studies and plans will affect drainage design for the site.
2) Discussion of site constraints such as slopes, streets,
utilities, existing structures, and the proposed development
or site plan impacts on the proposed drainage plan.
c. Hydrological Criteria.
1) Identify design rainfall (source of design storm depth
information NOAANational Oceanic and Atmospheric
Administration Atlas, Urban Drainage and Flood Control
District maps, etcetera).
2) Identify design storm recurrence intervals.
3) Identify runoff calculation method(s) and any computer
models.
4) Identify detention discharge and storage calculation
method(s)and computer models.
5) Discussion and justification of other criteria or calculation
methods used that are not presented in, or referenced by,
the Weld County Storm Drainage Criteria.
d. Hydraulic Criteria.
1) Identify capacity references and any computer models.
2) Identify detention outlet type.
3) Identify check/drop structure criteria used.
4) Discussion of other drainage facility design criteria used that
are presented in the Weld County Storm Drainage Criteria.
4. Drainage Facility Design.
a. General Concept.
1) Discussion of concept and typical drainage patterns for
historical conditions.
2) Discussion of compliance with off-site runoff considerations
and constraints.
3) Discussion of the content of all tables, charts, figures, or
drawings presented in the report.
4) Discussion of anticipated and proposed drainage patterns.
b. Specific Details.
1) Discussion of compliance with drainage criteria(street, inlet,
and pipe capacities, etcetera).
2) Discussion of drainage problems encountered and solutions
at specific design points.
3) Discussion of detention storage and outlet design.
4) Discussion of maintenance access and aspects of the
design.
5) Provide copies of Draft Colorado Department of Public
Health and Environment or State Engineer's permit
applications (where applicable).
5. Conclusions.
a. Compliance with the Weld County Storm Drainage Criteria.
b. Drainage Concept.
1) Effectiveness of drainage design to control damage from
storm runoff.
2) Influence of proposed development on any applicable Weld
County Master Drainage Plan recommendations.
3) Identification and written approval of affected irrigation
company or other property owner(s). Weld County may
require that the applicant provide evidence that off-site
impacted jurisdictions have been notified of the proposed
drainage plans and potential impacts.
6. References.
a. Reference all criteria and technical information used.
7. Appendices.
a. Hydrology Computations.
1) Land use assumptions regarding adjacent properties.
2) Initial and major storm runoff computations at specific design
points.
3) Historic and fully developed runoff computations at specific
design points.
4) Computer model input and output.
b. Hydraulic Computations.
1) Culvert sizing.
2) Storm sewer sizing.
3) Street capacity evaluation.
4) Storm inlet sizing.
5) Swale sizing.
6) Open channel sizing.
7) Check dam and/or drop structure sizing.
8) Detention pond area/volume capacity and outlet sizing.
9) Changes to Calculation Methods - If applicant/design
engineer modifies any portion of the Urban Drainage and
Flood Control District spreadsheets used for hydrologic or
hydraulic calculations, the applicant/design engineer shall
identify all changes to calculation assumptions or computer
programs as to type of change and specific factors that were
modified.
10) Computer model input and output.
C. Change of Zone Drainage Report Drawing Contents.
1. A General Location (vicinity) Map shall be provided at a scale of 1" = 2000'
or larger in sufficient detail to identify upstream off-site drainage areas
flowing into the development, downstream areas receiving site flows, and
general drainage patterns in the project area.
2. A Drainage Plan of the proposed development shall be provided at a scale
from 1" = 100' or 1" = 200' on a 24"x 36" drawing. The plan shall show the
following information:
a. Existing contours at 2-foot maximum intervals, contours should
extend at least 200 feet from all project boundaries or further if
necessary to show upstream and downstream drainage relationships
impacting the development.
b. Property lines, lot lines, utility crossings, and easements.
c. Streets with names.
d. Existing drainage facilities, pipes, structures, irrigation facilities, and
sizes.
e. Overall drainage area boundary and sub-area boundaries.
f. Proposed contours and flow directions indicated with arrows.
g. Location of proposed storm sewers, swales, open channels,
culverts, cross-pans, and other appurtenances.
h. Proposed outfall point(s) for runoff from the development area and
facilities to convey flows to the final outfall point without damage to
downstream properties.
Location and elevations of all defined 100-year floodplains and
floodways affecting the property.
j. Location and types of proposed permanent erosion control features.
Section 8-11-130. Final Drainage Plan Report.
The purpose of the Final Drainage Report is to update the preliminary design concepts,and
to present the design details for the drainage facilities discussed in the Change of Zone Drainage
Report. Also, any change to the preliminary concept shall be presented. The Final Drainage
Report shall identify all approved requests for variance from Weld County Storm Drainage Criteria.
A. All Final Reports shall be typed on 8.5-inch by 11-inch paper and bound. Drawings
measuring 24 inches by 36 inches shall be included. The Final Drawings shall be
bound within the report or included within a pocket attached inside the back cover
of the report. The Final Report needs to stand-alone, therefore, all calculations,
computer outputs, plans, supporting documents and important reference material
should be copied and included within the report appendix. The report shall include
a cover letter presenting the final design for review and shall be prepared or
supervised by an engineer licensed in Colorado. Only original documents sealed
in ink will be accepted. The sealed report shall contain a certification sheet as
follows:
1. "I hereby certify that this report for the final drainage design of (Name of
Development) was prepared by me (or under my direct supervision) in
accordance with the provisions of the Weld County storm drainage criteria
for the owners thereof."
Registered Professional Engineer
State of Colorado No.
(Affix Seal)
B. Final Drainage Plan Report Contents. The Final Drainage Report shall be prepared
in accordance with the outline shown above under Change of Zone Drainage
Report. In addition to including all of the items required for the report and plans
submitted with the Change of Zone described above under Change of Zone
Drainage Report and Drawings, the Final Drainage Report and Drawings should
include:
1. Proposed location and sizing of all storm sewers, swales, open channels,
culverts, cross-pans, and other appurtenances, including cross-sections of
swales and open channels.
2. Routing and accumulation of flows at various critical points for the minor
storm runoff.
3. Routing and accumulation of flows at various critical points for the major
storm runoff.
4. Detention storage facilities and outlet works, including proposed 100-year
water surface elevations.
5. Location of all existing and proposed utilities.
6. Routing of off-site drainage flows through the development.
7. Minimum lowest opening elevations of residential and commercial buildings
above the 100-year water surface in streets, open channels, ditches,
swales, or other drainage facilities, as illustrated by the preliminary grading
plans.
8. Proposed on-site private and public drainage easements.
9. Proposed off-site private and public drainage easements.
10. Elevations of manhole and inlet inverts in relation to project datum.
11. Proposed water surface elevations for street encroachments for the minor
and major storm.
12. Critical hydraulic structure dimensions.
13. Orifice plate sizes.
14. Detention pond volumes.
15. All other critical hydraulic elevations.
16. Operations and Maintenance instructions for the proposed stormwater
drainage facilities.
17. Construction-Phase Erosion and Sediment control calculations.
18. Permanent Erosion and Sediment control calculations.
C. The Final Drainage Report design hydraulic calculations shall be provided for each
of the proposed elements of the final drainage design.
Section 8-11-140. Construction Drawings and Specifications.
A. Where drainage improvements are to be constructed in accordance with the
accepted Final Drainage Report, the signed and sealed construction plans(on 24"
x 36"mylar)and specifications shall be submitted in conformance with the Final Plat
for review and acceptance prior to construction. The sealed plans and
specifications for the drainage improvements shall include all drainage components
designed within the Final Drainage Report.
B. The information required for the drawings and specifications shall be in accordance
with sound engineering principles, the Weld County Storm Drainage Criteria, and
the Weld County requirements for development and subdivision design.
Construction documents shall include geometric, dimensional, structural,
foundation, bedding, hydraulic, landscaping, erosion control, and other details as
needed to construct the storm drainage facilities. The accepted Final Drainage Plan
shall be included as part of the construction documents for all facilities affected by
the drainage plan. Submittal of digital format final plans and as-built drawings may
also be required by the Weld County Department of Public Works. Weld County
requires a minimum of three sets of paper construction plans for use by Weld
County inspectors.
C. Where erosion control and sediment control improvements are to be constructed
in accordance with the accepted Final Drainage Report, the erosion control and
sediment control construction plans(on 24"x 36"mylar)and specifications shall be
submitted in conformance with the Final Plat for review and acceptance prior to
construction. The plans and specifications for the erosion control and sediment
control improvements shall include all erosion control and sediment control
components designed within the Final Drainage Report.
D. Both construction-phase and post-construction (permanent) erosion control and
sediment control construction drawings shall be submitted. The construction-phase
erosion control and sediment control construction drawings shall be submitted
separately from post-construction(permanent)erosion control and sediment control
drawings. The construction-phase and post-construction phase erosion control and
sediment control construction drawings shall be the basis of compliance evaluations
by Weld County inspectors.
Section 8-11-150. As-built drawings.
A. Recording of Drawings.
1. The project record drawings shall be submitted to, and accepted by, Weld
County. Drawings will be submitted in appropriate digital form when
requested by the County.
2. Each drawing shall be labeled "DRAWINGS OF RECORD" in neat large
printed letters.
3. Construction information shall be recorded concurrently with construction
progress by the contractor.
4. Project Record Drawings shall be marked legibly and with an indelible pen.
5. Project Record Drawings shall record actual construction and contain, but
are not limited to, the following:
a. Field dimensions, elevations, and details.
b. Field changes which are made by minor deviations to the design
drawings.
c. Details, which are not on the original Construction Drawings.
d. Elevations of manhole and inlet inverts in relation to project datum.
e. Critical hydraulic structure dimensions.
f. Orifice plate sizes.
g. Detention pond volumes.
h. All other critical hydraulic elevations.
g. Floodplain and floodway delineations and Base Flood Elevations
(BFEs)where applicable.
h. Dimensions of erosion control installations.
6. Payment of permit fees must precede final acceptance.
B. Submission.
1. The project record drawings shall be submitted to, and accepted by, the
Weld County inspectors with a transmittal letter containing the following:
a. Date.
b. Project Title.
c. Design Engineer's name, address, and telephone number.
d. Title and number of each Record Document.
e. The signature of the Design Engineer and their Professional
Engineering stamp.
2. The initial acceptance of the storm drainage improvements will not be made
until all Weld County installation requirements are satisfied and the Project
Record Drawings are received and accepted by Weld County.
3. Acceptance of storm drainage improvements will not be made until all on-
site drainage easements have been recorded. Acceptance of storm
drainage improvements will not be made until all off-site drainage easement
agreements have been signed and notarized.
4. The final drawings of the storm drainage improvements will not be made
until the Project Record Drawings are received and accepted by Weld
County.
5. Weld County requires that the Project Record Drawings first be submitted
in blueline form for preliminary acceptance before final mylars are
submitted. Submittal of digital format final plans and digital format as-built
drawings may also be required by the Weld County Department of Public
Works.
BE IT FURTHER ORDAINED by the Board that the Clerk to the Board be, and hereby is,
directed to arrange for Colorado Code Publishing to supplement the Weld County Code with the
amendments contained herein, to coincide with chapters, articles, divisions, sections, and
sub sections as they currently exist within said Code;and to resolve any inconsistencies regarding
capitalization,grammar,and numbering or placement of chapters, articles,divisions,sections,and
sub-sections in said Code.
BE IT FURTHER ORDAINED by the Board if any section,subsection,paragraph,sentence,
clause, or phrase of this Ordinance is for any reason held or decided to be unconstitutional, such
decision shall not affect the validity of the remaining portions hereof. The Board of County
Commissioners hereby declares that it would have enacted this Ordinance in each and every
section, subsection, paragraph, sentence, clause, and phrase thereof irrespective of the fact that
any one or more sections, subsections, paragraphs, sentences, clauses, or phrases might be
declared to be unconstitutional or invalid.
NOTICE
PURSUANT to the Weld County Home Rule Charter, Ordinance Number 2006-7 published
above, was introduced and, on motion duly made and seconded, approved upon first reading on
September 11, 2006. A public hearing and second reading is scheduled to be held in the
Chambers of the Board, First Floor Hearing Room, 915 10th Street, Greeley, Colorado 80631, on
October 2, 2006. All persons in any manner interested in the reading of said Ordinance are
requested to attend and may be heard.
Please contact the Clerk to the Board's office at phone (970) 336-7215, Extension 4225,
or fax (970) 352-0242, prior to the day of the hearing if, as the result of a disability, you require
reasonable accommodations in order to participate in this hearing.
Any backup material, exhibits or information previously submitted to the Board of County
Commissioners concerning this matter may be examined in the office of the Clerk to the Board of
County Commissioners, located in the Weld County Centennial Center, Third Floor, 915 10th
Street, Greeley, Colorado, between the hours of 8:00 a.m. and 5:00 p.m., Monday thru Friday, or
may be accessed through the Weld County Web Page (www.co.weld.co.us). E-Mail messages
sent to an individual Commissioner may not be included in the case file. To ensure inclusion of
your E-Mail correspondence into the case file, please send a copy to
egesick@co.weld.co.us.
SECOND READING: October 2, 2006, at 9:00 a.m.
THIRD READING: October 23, 2006, at 9:00 a.m.
BOARD OF COUNTY COMMISSIONERS
WELD COUNTY, COLORADO
DATED: September 15, 2006
PUBLISHED: September 20, 2006, in the Fort Lupton Press
PROOF OF PUBLICATION
FORT LUPTON
STATE OF COLORADO
COUNTY OF WELD SS.
I, Karen Lambert, do solemnly swear that I
am the Publisher of the Fort Lupton Press;
that the same is a weekly newspaper printed
and published in the County of Weld, State
of Colorado, and has a general circulation
therein; that said newspaper has been
published continuously and uninterruptedly
in said county of Adams for a period of more
than fifty-two consecutive weeks prior to the
first publication of the annexed legal notice
or advertisement; that said newspaper has
been admitted to the United States mails as
second-class matter under the provisions of
the act of March 3, 1879, or any
amendments thereof, and that said
newspaper is a weekly newspaper duly
qualified for publishing legal notices and
advertisements within the meaning of the
laws of the State of Colorado. That the
annexed legal notice or advertisement was
published in the regular and entire issue of
every number of said weekly newspaper for
the period of 1 consecutive insertion(s); and
that the first publication of said notice was in
the issue of newspaper, dated 20th day of
September, 2006, and the last on the 20th
day of September, 2006.
Publisher. Subscribed andtworn before me, this the
18th day of September, 2006.
,10
\ No ary ublic.
CASE NO.401951 key 32742
orm planning gn d the criteria CODE ORDINANC COUNTY008-7 detveoped andepresented .and
hiseUrban Stolrm Dr follow ge Criteria /
Manual(Manual). Every urban area has two separate and distinct
IN THE MATTER OF REPEALING AND REENACTING, WIN drainage systems, t whether not m,they are actually planned and
designed. One is the initial system, and the other is the major
AMENDMENTS,CHAPTER 8 PUBLIC WORKS,OF THE WELD COUNTY system. To provide for orderly urban growth,reduce costs to future
CODE. - generations and avoid loss of life and major property damage,both
systems must be planned, properly engineered and maintained.
BE PT ORDAINED BY THE BOARD OF COUNTY COMMISSIONERS OF The determination of runoff magnitude should be by the Rational
THE COUNTY OF WELD,STATE OF COLORADO: Formula, the Colorado Urban Hydrograph Procedure (CUHP),
HEC-1, HEC-HMS, or statistical analyses based on an adequate
of the County of Weld, record of actual measured flood occurrences as set forth in the
WHEREAS, the Board of County Commissioners
State of Colorado,pursuant to Colorado statute and the Weld County Home RUNOFF chapter of this Manual. Use of streets for urban drainage
Rule Charter,is vested with the authority of administering the affairs of Weld should fully recognize that the primary use of streets is for traffic.
County,Colorado,and Streets should not be used as floodways for initial storm runoff.
Urban drainage design should have as an objective reduction of
WHEREAS the Boyd of County Commissioners,on December 28 2000 street repair and maintenance costs to he.publlc. Irrigation ditches
20061 enacting a comprehensive should not be used as outfali points for initial or major drainage
adopted Weld County Cede Ordinance
systems, unless such use is shown to be without unreasonable
Code for the County of Weld, including the codification of all previously
adopted ordinances of a general and permanent nature enacted on or before hazard, as substantiated by thorough hydraulic engineering
said date of adoption and - analysis, and written approval of the ditch owner(s) is obtained.
• In addition, irrigation ditches cannot be relied on for mitigating
WHEREAS,the Weld County Code b h need of rgvisIon and clarification with upstream runoff. Proper design and construction of stormwater
regard to procedures,terms,and requirements therein. detention ....J ...t.-6.... basins are necessary to minimize future
maintenance and operating costs and to avoid public nuisances
NOW, THEREFORE, BE IT ORDAINED by the Board of County and health hazards. This is particularly important,given the many
Commissioners of the County of Weld,State of Colorado,that certain existing
detention and retention facilities in ti.,.'�...... ...s:,,�rWeld County.
Chapters of the Weld County Code be,and hereby we, repealed and r► .
enacted, hoarier f amendments,antrtlb various Chapters are revised to add the, Weld County has adopted and needs o maintain tleMts oodplain
m
management programs. Floodplain management must encompass
CHAPTER 8 comprehensive criteria designed to encourage, where necessary,
PUBLIC WORKS the adoption of permanent measures which will lessen the exposure
of fife,property and facilities to flood ossds,improve the long-range
ARTICLE XI land management and use of flood-prone areas,and Inhibit,to the
ARTIC
Weld County Storm Drainage Criteria maximum extent feasible,unplanned and economically unjustifiable
future development In such areas'
DMsion 1 3. Amend Section 1.6 Flood Insurance to read:
General Provisoes
Section 8-11-f0. Repose and auhorlty. 'Flood Insurance is an integral part of the strategy to manage
flood losses.
Weld County continues to participate In the National
This Weld County StemDrainage Criteria is adopted it order to provide
minimum standards le preserve and rated the public health,safety,and Act food Insurance Program,set forth in the National Flood Insurance
general welfare in the lands of Weld County, o (NFIA)of 1988,as amended.'
authority granted by Part'4 of Article 15 of Tile 30,and Article 35 of 11%30, 4. Add the following o Section 2.1 Drainage is a Regional Phenomenon
C.R.S. That Does Not Respect the Boundaries Between Government
Section 8-11-20. Adoption of storm titl to ctione or Between Properties: "Weld County may from time
drainage standards-short e.
to time enter into Agreements with adjacent counties to cooperate
on regional planning. The Policy of Weld County shall be to pursue
The Denver; Colors'. Urban anal, and i Flood lum District's a l y unified drainage effort to assure an integrated
"Urban Some Drainage 1), Manual," 3, Best of Volume 1 (June drainage system, and to cooperate with other regional and local
2001)(Sept Volume 2(June 200 and Volbme f, Best he am Practiamendments
planning agencies on drainage matters.'
(September 19Bg is hereby adopted by reference,with the amendments
which are set forth heat The provisions of this Article XI Shall be known as 5. Amend Section 3.1.2 Rainfall-Runoff Relationships to read:
the'Weld County Storm Drainage Criteria.'Ai faditles for storm drainage on .
properties located within the unincorporated lards of Weld County,whether •A program should be maintained to collect and analyze rainfall-runoff
pubfic or criteria, ss private,r quired.dtieel an applicable master drainagep an relationships in urban areas of the D,....e.,eyM.Weld County.'
approved by Weld County. A copy of the'Urban Storm Drainage Criteria
Manual:shall be kept on fie in the dice of the Weld County Clerk to the Board
of County Commissioners for Inspection during regular business hours. It Amend Section 3.1.4 Library to read:
may be downloaded by visiting the Urban Drainage and Flood Control District "The_gyyoNNeld County should acquire and actively maintain
web site at www.udfcd.org,or ordered by contactingthe Urban Drainage annd. a library, which should be available for use by all governmental
Flood Control District at 3(13455-8277. - agencies,practicing planners,and engineers. The public should be
to the Text of the Urban Storm encouraged to use the library as part of C.,DvbLt'sWeld County's
Section 8-11-30. Weld County Addendum
educational and outreach programs.'
Drainage Criteria-Volume 1
A.Chapter 1-Drainage Policy 7. Amend Section 3.1.5 Runoff Magnitudes to read:
sured runoff
1. Amend Section 1.4 Planning to read: peaks
e"Wherehin ld be tabmagnitudeulated of mr cugteednWeld Cnd ounty streams
and gulches so that comparisons may be readily made between
"Sono drainage is a part of the total urban environmental system.
Therefore,storm drainage planning and design must be compatible watersheds and erroneous values may be more easily identified.'
with should comprehensive regional plans.Amaster plan for storm drainage B. Amend Section 3.2.Floodplain Data to read:
be developed and maintained in an up-to-date fashion at
all times for each urbanizing drainage-watershed--in-ihis-Darrver
regienwatersheds in Weld County. The planning for drainage in
program to delineate flood hazard areas along all waterways
in the region should be maintained. This program should make fun
tras facilities should be coordinated with planning for open space and use of such sources a.,ih., . I I—.J A.....D.,i.,sefen
be denrtatid coordinating stin these tn,new opportunities ms. steadier,the FEMA Flood Insurance Studies,data from the Natural
identified tthat can assist in the solution usedfrof drainage problems. Resources Conservation Service,the USGS,and should
be n studies
Naturalerev dreingble. should j a or stormust runoff nt to the by private consulting engineers.This information should regularly
wherever tensible. Major imns must be given o the reviewed and updated to reflect changes due to urbanization,
floodpPlanning
and and open space requirementsdrainage
of e tsystems ares(Whltd 1945). changed channel conditions, and the occurrence of extraordinary
based g design of stormw problems
drainage red not be hydrologic events."
on the premise that problems can be transferred from one
location to another. Stormwater runoff can be stored in detention 9. Amend Section 3.2.2 Data Inventory to read:
yeti-robnlien-reservoirs. Such storage can reduce the drainage
conveyance capacity required immediately downstream.Acquisition
of open space having a relationship to dtakaasweys wit provide The yWed collected should be stored in a Eena available
to
areas where stem runoff can spread out and be stored for slower alldelivery planners,developers,and engineers."
2. Amend Section 1.5 Technical Issues to read: 10. Amend the first sentence of Section 3.2.4 Priority for Data
Acquisition to read: I
.-
"The-BistrietWeid County will establish priorities for acquisition of
date because it is recognized that not all of the data can be collected
at ale tine' __.
.•
The Policy of the Weld County shall be to: "Y-
•
11. Amend Section 3.3.1 Master Plan to read:
'Drainage 1. Restrict upstream development to areas outside of the
age design does not lend itself to a piece-meal approach; jurisdictional dam water surface elevation created by a 100-year
therefore, master plans for drainage should be prepared on a storm plus freeboard.
priority basis. Such plans already cover most of the developed
major drat ays Int..DI.h..tWeld County.Additional plans will 2. Restrict downstream development to areas outside of the
be developed for areas yet unplanned. In addition,existing master jurisdictional dam 100-year floodplain. The jurisdictional dam
plans will updated as needed to-reflect changed conditions that 100-year floodplain is defined as either:
take place over time.'
12. Amend Section 4.1 Total Urban System a. The 100-year floodplain downstream of the emergency
ys to read: spillway assuming the dam is full to the elevation of the
• emergency spillway at the beginning of the 100-year storm
"Storm drainage is a part of the total urban environmental system. and the 100-year storm is routed through the dam and out the
Therefore,storm Maim planning and design should be compatible emergency spillway,
with comprehensive regional plans. Master plans for storm drainage
have been developed and maintained in an up-to-date fashion for OR
t set A the ....te,..h,J, I.,II,.. D,.,,.., ,.a„„Weld County An
effort to complete the coverage of drainage master plans for yet b. The path that the basin's 100-year floodplain would form
unplanned areas of tire-BisrietWeld County should be continued through the downstream development if the dam were
until full coverage is achieved."
removed by the owner?
18. Amend Section 4.5.5.Reliance on Embankments to read:
13. Amend Section 4.1.2 Master Plan to read:
'Ce.,l"..ane.,p..kir .nJ ew..y ^•tit„D..,.w„ ,,.a:.•,I.•ww.,�tM 'The detention of floodwaters behind embankments created
f..• •••a.A.• 4..,.,.,.t' R., ,.,b..,, ,.b.,..,S...;,,..e„ Cr
by railroads, highways or roadways resulting from hydraulically
beu,ula,:w�nd o,,..,N,s. The Oiatiict can help t..ceo,d;,ele cgo,W. undersized culverts or bridges should not be utilized by the
N. r •.the,b..a....., ,r,,......,,,.iM.l drainage engineer for flood peak mitigation when determining the
downstream flood peaks for channel capacity purposes unless such
• detention has been covered by a binding agreement approved by
tl—ffrab;,.tWeId County" .
dete-Early work includes the planning of major drain apewsys 19. Amend Section 5.1 Design Criteria to read:
from the point of()offal!,proceeding in an upstream direction.The
major drainageways are generally well defined and often dictate 'Storm drainage planning and design should adhere to the criteria
the design of the initial drainer system, including storm sewers, • developed and presented in this Manual maintained by the
detention facilities, and water quality systems. The D;.,t.k.Weld eistrietWeld County.°
County has established a suitable format for master plan reports
and drawings so that a uniform planning approach and coordination 20, Amend Section 5.1.1 Design Criteria to read:
of efforts can more easily be made. Master planning should be done
in enough detail and with adequate thoroughness to provide a ready "The design criteria presented herein represent current good
drainage devjopnrent guide for the future in a particular watershed engineering practice,and their use in ti...D...,...,,..s....Weld County
Generalized concepts based on Se-of--thumb hydrological analyses is recommended.The criteria are not intended to be an ironclad set
should not be used as master plans; a more rigorous analysis is of rules that the planner and designer must follow;they are intended
necessary. The Policy of Weld County shall be to enforce and to establish guidelines,standards and methods for sound planning
implement adopted Master Drainage Plans. These Master Drainage and design. The Weld County Department of Public Works may
Plans may be amended from time to time In the future." bygrant varia l from the design t i cwhria ofe v Manual a acceptance
14. Amend Sedron4.1.3, d tie Final Drainage Report in which the variance request is well
bread: •
paragraph#2,Planning Process Ingredients documented'
'2. Initial Drainage Planning. 21. Delete the second paragraph of Section 5.2.1 Design Storm
System All local and regqiolonnaall Return Periods:
planning must take into consideration the initial drainage
system to transport the runoff from storms expected to occur
once every 2-tei8 years.The planner of an initial system must
strive to minimize future drainage complaints.° - '
15. Amend the second ..nn.I.LAe.kell, pn,..J.d II..e.,,,.L........q..;,..J t........1-..11,
rid: paragraph of Section 4.1.6 Water Duality to J....VIVY,UJA, —An.,
It 'Ily ,I.,.d,...li„t;.. .1..,,�, o„J
.,
'Sanitary sewerage systems that overflow or bypass untreated .�.k,v„.,•t.., ,. ,...ol. Ile..�.e;,
sewage into surface streams should not be permitted in the-Bawer
tegienWeld County Existing systems that discharge sewage should _
be adjusted by their owners to eliminate this problem? Amend Section 5.2.2 Initial Storrs Provisions to read:
18. Add the following to Section 4.5 Detention and Retention 'The initial storm drainage system,capable of safely handling 2—te
Storage: 10-year floods dep.,.J;,,y en I.,u.l,..t..,lu, is necessary to reduce
'The Policy of Weld County shall be to require regional and/or the frequency of street flooding and maintenance costs,to provide
on-site detention for all future developments. Temporary protection against regulariy recurring damage prom storm runoff,to
or interim help create an orderly urban system, and to rage s convenience
detention/ iotanot yet may kw required it the downstream regionalaster to urban residents. Normally, the initial drainage system cannot
facilities have not been conies are per the applicable Master economically carry major runoffs,though the major drainage system
Plan. tornmater retention facilities areal clrwy not allowed in Weld can provide for the initial runoff. A well-planned major drainage
County,but will be considered for special circumstances. It is Weld system will reduce or eliminate the need for storm sewer systems
• County policy to require detention of runoff from the 100-year storm
falling on the developed site and release of the detained water at the (Jones areap 1967). Storm sewer systems consisting of underground
thepipes a part of initial storm drainage systems.
rate Detention the runoff of5-year d onstorm ps falling on the Weld
unty releases based m ts types provide v not approved for 23. Amend Section 5.4.1 Use of Streets to read:
County Proposed developments must development
for safe co. Off-site
conveyance
of s a flews through the homed development site. Off�o, eehs are significant and tsimportant for
in urban drainage, and full
Sows may si veoa through on r around the proposed detention use should rec bei made f primary
for urro runoff f ue s reasonable
rtraffic.
facilities. Positive drainage must be provided.' •limits,a noble limits that the o st pus f streets is for traffic.
17. Amend Section 4.5.4 Reliance on Non-Flood-Control Reservoirs Reasonable rabs of the use of streets forle transportation gn of storm
to read: runoff should Tee DP-1
governed by reasonable design criteria rs
summarized in Table DP-1 and in the Streets/Inlets/Storm s Sewers
°hlxt., owned uai Bald GaA.A io Llrs 4e,Met ha wed for
chapter of this Manual. Urban drainage design should have as
toed a robjectives reduction of street repair,maintenance costs,nuisance to
poi fro—.4 in ue.d.,pl..,,,l,g beu,u-•d w ,A,pcWty the public,and disruption of traffic flow.
When maximum allowed encroachment is present, the storm
sewer system design based on the initial storm should commence.
Development of a major drainage system that can often drain
Juriin-r ictional dams are classified the State Engineer as either the initial which ct from stormthe sewer streers y encouraged, thus commence making the
low, moderate, or high hazard structures depending at the system should further
g on condkion, dwnstream. Initial and major drainage planning should go hand-
downstream. Dams are classified as high hazard structures when,
in-hand.
in the event of failure,there Is a potential s of life. Dams presently loss
rated as low or moderate hazard structures may be changed to high While it is the intent of this policy to have major storm runoff removed
hazard rating if development occurs within the potential path of from public streets at frequent and regular intervals and routed into
would due to a dam cosach. In this pig,to reservoir owners major dtreets ways, it is recognized that water will often tend to
would be liable for the cost of upgrading the structure to meet the follow streets and roadways and that streets and roadways often
higher hazard classification. be aligned so they will provide a specific runoff conveyance
function. Planni and design objectives for the major damage
sYthe limiting�tospubic
nMaed in Table DP-2 in streets should be based theStreets/
Irysy/Sbrm Sewers chapter of this Manual.
C.\i
The allowable flow acme street Mount be within the creaoa
presented in Table OP-3 and in the'Streets/lnlets/Storm Sewers 30. Amend Section 6.3.2 New Development to add the following:
chapter of this Manuel. "The Policy of Weld County shall be to outsource engineering review
An arterial street crossing will generally require that a storm sewer of all CLOMR and LOMR submittals received with a development
system be commenced, unless the topography is such that day- application. The developers shall reimburse the Weld County
lighted inlet culverts or other suitable means can transport We___ Department of Public Works for all outsourced engineering review
costs. Upon FEMA approval of a CLOMR or LOMR, payment of
stormronoaunder Bubblers u er Onv rt d siph can hichuted y major all outsourced engineering review costs is due and payable to
drainage facility. envertad siphons which convey e flows Weld County. Developers are welcome to contract directly with
beneath because
roadways)are not eplug in the imDe nt ,dglewWety our outsourced consultant(s)for the preparation of CLOMRs and
County because of possible plugging with sediment and difficulty onl LOMR's,if they so desire'
in maintaining them. Collector streets should have cross pans only
at infrequent ordan locations as specified by g governing agency end's 31. Amend Section 7.1 Adoption of Drainage Master Plans to read:
accordance with good traffic engineering practices. The lord street
criteria for overtopping also apply to any private access rood that "This Manual and master plans should be adopted and used by all
serves commercial areas or more than one residence,for emergency governmental agencies operating within B...D,.b JWeld County"
access and safety reasons' -
24. Add the t following to Section 5.5 Irrigation Ditches:It is the policy
32. Amend Section 7.3 Amendments to read:
of Weld County to prohibit the discharge of stormwater runoff from "Problems in urban drainage administration encountered by
developed areas into Irrigation rhee ditches hdi and facilities,renc except asanyone should be reviewed by the
raquked by water rights or where such discharges are in conformance newEistrietWeld County to determine if equity or public interests Indicate
web.approved Master Drainage plans. Further, wherever I�i a need for drainage policy, practice, or procedural amendments.
development will after patterns of drainage,Into irrigation ditches Th. D;.l,;.tWeld County should continually review the needs.of
by Increasing flow rates or volumes, or vnll change the historic the Benverregiencommunity in regard to urban runoff criteria and
concent points of runoff,the County shall to obtain written consent ofree pgpuriroep iate each new should recommend changes as necessary to this Manual."
company before approving thedrainage design and development."ditch
33. Add Section 7.5 Drainage Improvements to read:
25. Amend Section 5.5.1 Used Ditches to read:
'Weld County Master Drainage Plans set forth improvements
"Tha irrigation ditches coursing through urban areas are laid out on -required for existing and future growth areas. There are areas of
fiat dopes and with limited carrying capacity. Based on experience Weld County for which no Masten:M*14 a plans yet exist. Weld
and hydraulic calculations, irrigation ditches cannot, as a general County may require a Master Drainage study in support of proposed
rule, be used as an outfall point for the initial storm drainage development. The policy of Weld County regarding the design and
slalom because of physical limitations. Exceptions to the rule can construction of improvements within the Master Drainage Plan
occur when the capacity of ton ditch is adequate to carry areas shall be as set forth below, subject to Weld County budget
rrngeand appropriation approvals.
the normal ditch flow plus the initial to those runoff with the
. -
W Written
approval to must a hazard to below the ditch. 1. Weld County shall identify needed design and construction of
Written be obtainedefrom the ditch owe stating improvements as set forth in adopted Master Drainage Plans for
that ower f understands the physical liand legal (i.e.,e n liability) existing and future growth areas.
the use
consequences of acceptingsaid runoff.for there Is a question where
the of irrigation hir as outfalls initial storm there 2. The drainage systems for future development and redevelopment
is storm question about their unsuitability wokg as an outfallfor the major provide .shall be designed and constructed by the developer(s).
m runoff. Without major reworking of izardttonse downstream w
or l carrying t capacity ditches are
alwdays
y those qu 3. The developers shall be responsible for design and construction
for below the ditch,the ou ld not trealmostused as
as ans totally inadequate of temporary or interim storm drainage systems required due to
because such a use and should be ely own an net one ca cannot
assume
the lack of adequate storm drainage facilities downstream of new.
theperpetual
tudasxistence or normallyon
a ditch. Land plannersuand development.
the engineers e with
pla with a proposed inageconditions development downhill from a ditch altered 4. The developers may be responsible for design and construction
shall plan for pre-ditch Fordrainage a , t as well as ycontinuedW of permanent storm drainage systems required due to the
ditch seepage. For new development,s shall beds the policy of Weld lack of adequate storm drainage facilities downstream of new
County to prohibit unit-tamed dischargese to roadside ditches locateddevelopment"
in the Count'right-of-way way. In the event a ounty rig development the
wishes to tlesrgn request of discharge to a Count'right-of-way.Ha B.Chapter 3-Planning
developer,at the request of the County,shall have the .ef.waentt
toy
design0h devnel construct op nren exxppeBnse Such improvements rigtall 1. Amend first paragraph of Section 7.1 Initial Drainage to read:
include,but not be limited to:detention ponds,armored channels, "Planning and design for urban storm runoff must be considered
improvements v and other drainage be borne by adjacent Cost-sharing of such sded from the viewpoint of the regularly expected storm occurrence,which
may be by developments, such includes the Initial storm and the major storm. The initial(minor)
cost sharing to be negotiated and the developer. Weld County may storm has been defined M K........o........1 b,8...Dia AAby Weld
require written agreements construction bonding of such offsite County to have a return frequency
drainage improvements' N...,,, 10,.re..of once in tern(10)years(the 10-year storm)for all
26. Amend Section 5.5.3 Conformance With Master Plan to read: uses. The major storm has been defined to have a return period of
100 years. The objective of major storm runoff planning and dmqn
is to reduce the potential for major damage and loss of life.The Inffial
'Use of irrigation ormrunoff ditches for be prohibited ron and transport of either Initial or drainage system is necessary to reduce Inconvenience,frequently
major storm should unless r plans,caly provided recurring damages,and high street maintenance and to help create
in..te-Bl R...-..A...,,u.the Weld County master or approved an orderly urban system with significant sociological benefits."
by ilia-Btetric4Wek1 County and the ditch owner."
2. Amend second paragraph of Section 9.1 Storm Sewers to read:
27. Amend Section 5.6 Detention and Retention Facilities
Maintenance to read: 'The initial drainage system,including storm sewers,is that portion
of the total drainage system that often receives the most attention
'The significant costrof handling stormwater runoff,coupled with the from engineers. It is what the average citizen considers to be the
social benefits to be derived from proper storm drainage facilities, urban drainage system. It is what directly contributes to the orderly
points towards the use of detention and retention basins for storage growth of a community by handling the storm runoff expected to
of stormwater runoff in tit.D,.r.er,s;.,,(Weld County. Maintenance occur once every 4....b b..,.....0 ten(10)years(the 10-year sto m)
provisions must be arranged. Maintenance of detention or retention for all uses."
facilities includes the removal of debris, excessive vegetation
from the embankment, and sediment. Without maintenance, a 3. Amend Section 9.4 System 3ltng to read:
detentioNretention facility will'become an unsightly social liability
and eventually become ineffective."
28. Amend Section 6.1 Purpose to read: +0 a The design return period to be used for storm sewer design
in Weld County is the 10-year skim for all land uses. Storm sewers
"Vm;eus ge..r.ae,.,.td sae„c;c. ,,ti,;,. tl,. D..i,... ,,t,L.,,. .IA,.Ad passing flow under County roads shall have a minimum design
Floodplain management capacity for the 10-year storm and a minimum diameter of 15 inches
includes comprehensive criteria designed to encourage. where or equivalent open area. System sizing design shall adhere to Weld
necessary, the adoption of permanent state or local measures County street inundation criteria of six(6)Inches for the minor storm,
which will lessen exposure of property and facilities to flood losses, and 18 Inches for the major storm event. This is a departure from
improve long-range land management and use of flood-prone the policy of recommending different return periods for different land
areas,and inhibit,to the maximum extent feasible,unplanned future .
development in such areas."
29. Amend first sentence of Section 6.2 Goals to read:
"There are two goals in regard to floodplain management: • To
reduce the vulnerability of Benver-regiertWeld County residents to
. the danger and damage of floods'
4,9 uses. Experience has shown that it is not practical to varystorm INLET TYPE PERMITTED USE
sewer design by land use because a single system often serves
multiple land uses. Instead,greater attention is necessary to ensure Curb Opening Inlet Type R All street types with 6"vertical curb
that the major system is adequate to protect the public and property
within all areas,regardless of land use."
Grated Inlet Type C All streets with a roadside ditch or swale
C.Chapter 4-Rainfall
1. Add the following to Section 1.0 Rainfall:"For proposed Weld County Grated Inlet Type 13 Alleys or private drives with a valley gutter
developmentdrainagedesign,the Rainfall Depth-Duration-Frequency
maps presented in the USDCM may be utilized only for those areas Combination Inlet Type 13 All street types with 6"vertical curb
of Weld County shown on the Figures in that manual(Figures RA-1
through RA-12). Drainage designs proposed for locations outside
of the areas of Weld County covered by Figures RA-1 through 5. Add the following to Section 3.3.6 Inlet Clogging: "To account for
RA-12 should utilize the depth-duration-frequency information effects which decrease the capacity of the various types of inlets,
provided in the Precipitation-Frequency Atlas of the Western United such as debris plugging, pavement overlaying, and variations in
States, Volume II - Colorado published by the National Oceanic design assumptions,the theoretical capacity calculated for the inlets
and Atmospheric Administration (NOAA). The NOAA Atlas may is to be reduced by the factors presented below for the standard
be accessed at: http://www.nws.noaa.gov/oh/hdsdnoaaatlas2. inlets permitted for use in Weld County.
him. Where development is proposed in larger watersheds,design ,
hydrology should utilize longer storm durations appropriate for the WEI D COUNTY
size of the entire watershed. See Tables RA-1.and RA-3 in the ALLOWABLE INLET CAPACITY
USDCM for storm duration and area adjustments."
PERCENT OF
D.Chapter 51 Runoff INLET TYPE THEORETICAL
1. Add the following to Section 3.3.1 Rainfall:"See Tables RA-1 and CAPACITY ALLOWED
RA-2 within the USDCM Rainfall Chapter for 1-hour and 2-hour ' Continuous CDOT Type R
rainfall area adjustments and distributions. For locations outside Sump orGoe
of Weld County,covered by USDCM Figures RA-1 through RA-12,
utilize the depth-duration-frequency information provided in the 5'length 88
Precipitation-Frequency Atlas of the Western United States,Volume
IC 10'length - 92
2. Amend Section 5.1 Published Hydrologic Information to read: 15'length 95
The D',A;..tWeld County has prepared hydrologic studies for the Continuous Grade- Combination Type 13 66
ma o.t —ef-hro-major drainageways within BiseietWeld County
boundaries. These studies contain information regarding peak 50
flow and runoff volume from the 2-year through 100-year storm Sump Grated Type C 50
events for numerous design points within the watershed. They Grated Type 13
also contain information regarding watershed and sub-watershed Sump Combination Type 13 65
boundaries,soil types,percentage imperviousness,and rainfall.The
studies are available at the BiabiektibroryWeld County Department
of Public Works. When published flow values are available from
the BiseietWeld County for any waterway of interest,these values 6. Amend the first paragraph of Section 3.4.2 Design Considerations to
should be used for design unless there are compelling reasons to read: .
modify the published values." • "The primary design consideration for the location and spacing
E.Chapter 6-Streets/Inlets/Storm Sewers of inlets on continuous grades is the spread limitation. This was
- addressed in Section 2.2.Tebk,CT 2 k..6 pe.en,..,t a t..,.,....1......n!
1.Amend Section 1.3 Components of Urban Stormwater Collection
and Conveyance Systems to read:
7..Amend brtpe third paragraph Section 4.2 Design Process,
"Urban stormwater collection and conveyance systems within the . Considerations,and Constraints to read:
District Weld County are comprised of three primary components: "Once afnal layout ischoean,storm sewers are sized using hydrologic
st(t)street gutters( and roadside sces like(2)atnv manholes,junctions,inlets,and .). techniques (to determine peak flows) and hydraulic analysiiss to
orm gutters(and adside swat es f hstreet etc.). determine pipe capacities). This is accomplished by designingad the
Street gutters and coney runoff collect rurwRfmwat a nl (and upstream pipes first and moving downstream. P1.45 oiresssaller
maintain areas)h o convey the v to a stormweter inlet while The minimum
maintaining the street's level-of-service'
size storm sewer pipe within a Public Right-of-Way or Public
2. Amend first two paragraphs of Section 2.2 Design Considerations to Drainage Easement shall be 15 inches in diameter or equivalent
read: open area. Refer to the"Weld County Development Standards and
Specifications Governing the Construction of public Improvements",
'Certain design considerations must be taken into account in order latest edition, for allowable storm sewer pipe materials. Pipes
to meet street drainage objectives. The primary design objective generally increase in size moving downstream since the drainage
is to keep the spread(encroachment)of stormwater on the street area is increasing. It is not good design practice to decrease the pipe
below an acceptable value for a given return period of flooding. As size moving downstream,even if a steeper slope is encountered that
mentioned previously,when stormwater collects on the street and will provide sufficient capacity with a smaller pipe. The potential for
flows down the gutter,the top width(or spread)of the water widens dogging is always a concern.'
as more stormwater is collected. If left unchecked,the spread dr •
water would eventually hinder traffic flow and possibly become 8. Add the following to Section 4.4.1 Flow Equations and Storm Sewer
hazardous (i.e., reduced skid resistance, hydroplaning, splash, Sizing:"The Manning's roughness coefficient"n"for all storm sewer
etc.). Based on these considerations,the-Dist ietWeld County has pipe capacity Weld County calculations shall be 0.013 regardless
established encroachment(spread)standards for the minor storm of pipe material(ie.Concrete,PVC,or HDPE)with the exception of
event. These standards corrugated metal pipes which shall have a coefficient of 0.025."
re provided in Chapter 3,
Planning,Section 9.4 of the Weld County Storm Drainage Criteria. 9. Add the following to Section 4.5 Hydraulic and Energy Grade Line
Calculations:The hydraulic grade line and energy grade line shall
Standards for the major storm and street cross flows are also be calculated for each storm sewer system and included in the
required. The majjotial for pr storm needs to lic beassessed to determine the Final Drainage Report. Each storm sewer system shall be profiled
le
n
regulated for traffic flow an and d publicsafety reasons.Cross flows also need Weld flow hydraulic gra be on the Final Construction
e line Dre(HGL).he eennerrgylgradeinclliine(EG the L)for
County has established street inundation standards during the the design flow shall be at least 6 inches below the final finished
major storm event and allowable cross-street flow standards. These elevation of the manhole rims and inlet flowlines."
standards
' re provided in Chapter F. Chapter 7-Major Drainage
3.Planning,Section 9.4 of the Weld County Storm Drainage Criteria.
Allowable lbw depth is measured vertically from the gutter flowline 1. Add the following to the first Paragraph of Section 3.2.3.2 Side
at the curb face' Slopes:"For constructed or natural channels with sideslopes steeper
than 2:1,appropriate construction setbacks from the channel edge
3. Amend second parag raph Section 2,3.1.3Allowable Gutter Hydraulic may be required to allow potential future channel meandering.
Capacity Weld County to read: Access for maintenance may require easement."
"There are two sets of reduction factors developed for Denver 2. Amend Section 3.2.7 Summary of Preliminary Design Guidance to
metropolitan areas(Guo 2000b)and they shall also be utilized for add the following note to Table MD-2:"Grass lined open channels
Weld County. One is for the minor event, and another is for the conveying < 50 cfs may reduce the minimum 1.0 foot freeboard
major event. Figure ST-2 shows that the reduction factor remains requirement to the freeboard required to conveying 1.33 times the
unity(1.0)for a street slope<1.5%,andthen decreases as the street 100-year design flow. The reduced freeboard may only occur if a
slope increases? 1.0-foot minimum freeboard is not physically or reasonably possible
and a variance request is submitted."
4. Add the following to Section 3:1 Inlet Functions, Types and
Appropriate Applications:"The standard inlets permitted for use in
Weld County streets are:
3. Delete the first paragraph of Section 3.2.8 Maintenance Eligibility 11. Amehd the fifth paragraph of Section 4.2.2 Design Procedure to
and replace with the following: read:
"Water surface profiles muslshall be computed, tyPcatir fe, II...
• 10 end 100-yeerevenlsfor all open channels conveying>50 cfs
Nt,L El—t L. D.S:J. •MJ,.Ln......... Clylbgily C.:.1.1...../ may within Weld County.Computation of the water surface profile should
cl.,...e., ..Ilh tn... Th.....,.J.r L.d1.ect.d b L,ekrop the!Jest full utilize standard backwater methods, taking into consideration all
.....4.t....... IIa:bJar ...te.:., ..t L. D:.1.I.f.. W L a:L ( losses due to changes in velocity,drops,bridge openings,and other
UDI-CD.ag). Maii.tana,¢e Cl' ibliy Guidelines as of Juts 2001 obstructions. Computations begin at a known point and extend in
.Weld Courtly will an upstream direction for subcritical flow. It is for this reason that
only maintain eligible major drainage ways by special agreyfurel the channel should be designed from a downstream direction to an
The requirements below must be satisfied as of(adoption date)fel s upstream direction. It is necessary to show the energy gradient on
major drainage channel to be eligible for Weld County maintenance. all preliminary drawings to help prevent errors. Whither or not the
Note that the Weld County'Maintenance Eligibility Guidelinedrmey energy gradient line Is shown on the final drawings is the-option of
. _ chancre with time." -., the reviewing agency but is encouraged by the District.'
4. Amend the first sentence of Section 3.2.8.3 Grass-Lined CV 12. Add the following to the last paragraph of Section 4.2.2 Design
Design to read: Procedure: Hydraulic grade lines shall be shown on the final
drawing profiles of open channels conveying > 50 cfs within the
'The design for a ggrassalned channel must meet the following criteria Weld County.H Energy ydraulic grade lines on final drawing profiles are
• to be eligible for 13ishietWeld County maintenance'" encouragare encouraged to ease assessment and ade lines on rre al Construction
compliance with
5. AmendSection 3.3.4 Maintenance to read: street inundation criteria.'
13. Amend second paragraph of Section 4.2.3 Life Expectancy and
Maintenance to read:
The local e,ev .,n,tnt n,ey reyJlle the goad to tte auA .':b 6
.Weld . .
County and the design engineer,shall work together to provide el—II L.r,.....d..J.k,,,1 U.....L,..L..s6,.f..11,...4...J.,.,..,;a,...az..
access to all major drainageways as determined appropriate at
the time of preliminary and finat design. Weld County encourages k,,.h..of Cl..,,2....JL..... ... .. 5 6,.1.th:.k.,......,.L eleL.Weld
volunteers to assist Weld County in performing routine maintenance County and the design engineer shall work together to provide
of all the drainage ways within the County through an'Adoption , access to all major drainageways as determined appropriate at the
program and will assist these groups in a vanety of ways.' time of preliminary and final design.
6. Amend the fourth paragraph of Section 3.5 Choice of Channel Lining 14. Amend the second paragraph of Section 4.3 Concrete-tined
to read: i Channels to read:
so•••
"Manufactured channel linings such as gabions, interlocked "Concrete-lined channels can be used for conveyance of both
concrete blocks,synthetic linings, etcetera, are not recommended subcritical and supercritical flows. In general, however, other
for new developments,but will be considered by Weld County on a types of channels such as grass-lined channels or channels with
case-by-case basis. As with concrete-and riprap-lined channels,all wetland bottoms are preferred for subcritical flows. The use of a
of these types are best considered for helping to solve existing urban concrete-lined channel for subcritical flows should not be used
flooding problems where right-of-way is very limited. Manufactured ,4.,,,..Wi P,t,jr,4,u!lugual, prpymsta(1ceg.,,when.A„gefrgw.right-of-way
channel linings should be used with caution,and each type of channel
lining must be scrutinized for its merits,applicability,ability to meet exists. Vegetated channels are normally preferable in tlx9enver
other community needs,long term integrity,and maintenance needs reglanWeld County because available thalweg slopes are generally
and costs." steep enough.
Amend the
7. Add the following to Section 4.1.5 Trickle and Low-Flow Channels: 15.Channels to read:unh paragraph of Sector 4.3 Concrete-Lined
"Under drain pipes shall not be used in lieu of trickle channels
within Weld County but will be considered by Weld County on a "In th.,D.,.....,...4,..„(Weld County,all channels carrying supercritical
case-by-case basis." • flow shall be lined with continuously reinforced concrete linugs both
of Section 4.1.7 Water Surface Profile to longitudinally and laterally. There shall be no diminution of wetted
8. Amend the first
paragraph area cross sections at bridges or culverts. Adequate freeboard
read: shall be provided to have a suitable safety margin. Bridges or other
structures crossing the channel must be anchored satisfactorily to
"Water surface profiles should be computed for all channels; withstand the full dynamic load that might be imposed upon the
nveying > 50 cfs structure in the event of major trash plugging."
within Weld County. Computation of the water surface profile should
include standard backwater methods, taking into consideration 16. Amend Section 4.3.6 Maintenance to read:
all losses due to changes in velocity,drops, bridge openings,and
other obstructions. Computations should begin at a known point
and extend in an upstream direction for subcritical flow. It is for "Concrete channels require periodic maintenance including debris
this reason Thal the channel should be designed from a downstream and sediment removal,patchin
g,g,jorepair,and other
red, especiuch vities.
a an upstream directiondrawings
It is to pry show ag the Their condition should be periodically monitored, especially to
energy r gradient on all the preliminary dra de line t help n the
assure that flows cannot infiltrate beneath the concrete lining. A
errors. Whether or not the energy grade is shown on UDi final t.,.,...,,,,,,,,,,,,,,,,,,,,J..;t1.../...;..............u..
drawings is an option of the reviewing agency,although the District I,,.II b.. .. r..M.e..t,Jll,.,f 12 f..,,i
,. N,,,.IJ..J,.L.,a th.,..,.c...LII,,, .,i.II,,...�.,,J,,.6.,.ao..oz..
encourages this." Th..I.c.J ge.em...........or req.:—Ih. re.J tw Lc s,.rk.a,J-.J2t 0
9. Add the following as the third paragraph'of Section 4.1.7 Water eld
County and the design engineer shall work together to provide
Surface Profile:"Hydraulic grade lines shall be shown on the Final access to all major drainageways as determined appropriate at the
Construction Drawing profiles of open channels conveying>50 cfs time of preliminary and final design."
within Weld County. It is not necessary to show energy grade lines
on Final Construction Drawing profiles, but it Is encouraged. The 17. Amend Section 4.4,1.3 Wire-Enclosed Rock(Gabions)to read:
energy grade line for the design flow shall be at,or below,the final
finished top of channel bank elevation.Hydraulic grade lines on Final "Wire-enclosed rock, or gabions, refers to rocks that are bound
• Construction Drawings are encouraged and will ease assessment together in a wire basket so that they act as a single unit. The
and review of compliance with street inundation criteria." durability of wire-enclosed rock is generally limited by the life of the
10. Amend Section 4.1.8 Maintenance to read: • galvanized binding wire that has been found to vary considerably
under conditions along waterways. Water carrying sand or gravel
'Grass-lined channels must be designed with maintainability in will reduce the service life of the wire dramatically. Water that
mid. See Section 3.2.8 for the Districts Maintenance E ibility rolls or otherwise moves cobbles and large stones breaks the
Guidelines, which also provide guidance for elements of n wire with a hammer-and-anvil action, considerably shortening
the life of the wire. The wire has been found to be susceptible to
that permit good maintenance of these installations. A-stable corrosion by various chemical agents and is particularly affected
by high-sulfate soils. Wire-enclosed rock installations have been
found to attract vandalism,and flat mattress surfaces seem to be
Tho L,cel gorerin..e.t nay iequ:wa the road to be sudwatl MarWeld • particularly susceptible to having wires cut and stones removed.
County and the design engineer shall work together to provide For these reasons, e.. D:.t.;.tWeld County discourages the use
of wire-enclosed rock. If the designer chooses to utilize gabions,
access to all major drainageways as determined appropriate at the they should be placed above the low-flow channel or 2-year water
time of preliminary and final design.' surface elevation. All flat mattresses must be filled with topsoil and
then covered with a 6-inch layer of topsoil."
42
18. Amend Section 4.4.7 Maintenance to read:
No Change to remainder of paragraph.
shall be piwider]r-1.,:,g Ito u,E,c.Lnyth of all i,4,d;a;,,aua:.r,,J. 27. Amend the second paragraph of Section 4.5.6 Technical
Constraints to delete the sixth bulleted item:'Ixrge4reeaeenlhreeten
h.J.... ,.1 CI...., 2 ,....Jb...,.. .., .. 5;...I.ll.:..k ..,.......L. .AA.Weld et,.;..t..y,;tr of.L..cL.,,.l r ttr..Lr.,.et...es...,L.,b.ppl.y a.
County and the design da y;n
engineer shall work together to provide - g tt.,p,•t,.rr:,, e, ttrppr:g and e,.mGre&.,;,,lo en
access to all major drainageways as determined appropriate at uU1JL.,,A,.,.,,,,t,..kJt,....k,,,,byte,,.;,y.,,,Jt;,...,J.a„lae....t.Jo,.
the time of preliminary and final design. Requirements for District *decomposition,"
maintenance eligibility are reviewed in Section 3.2.8 of this chapter.
Of particular concern is long-term loss of riprap,particularly due to 28. Amend the second paragraph of Section 4.5.6.Technical
the public moving the rock(for smaller sizes). Grout can deteriorate Constraints to amend the last bulleted item to read:
with time, and this should be monitored, as well. Improper grout
installation creates long-term maintenance problems.° "Many of these problems may be avoided mrough selection of
the appropriate type and species of vegetation. Such seleWons
19. Amend Section 4.5 Bioengineered Channels to read: and expert advice must be obtained from qualified Indivduals in
rovegetation and bioengineering.
"Bioengineered channels (see Photographs MD-10 and MD-11) del)•. ,11,, ,,,,,•,H,eb:,.osi,.,,,,,,,d J.o.....1:.,L,.,r,,.,,:E..,�^
emphasize the use of vegetative components in combination with
structural measures to stabilize and protect stream banks from 29. Amend the first two paragraphs of Section 4.6 Natural Channels
erosion. Th.. D:..b;.AWeld County advocates the integration of to read:
bioengineering techniques into drainage planning, design, and
construction when the use of such channels is consistent with the 'Natural waterways in tlle--Bsnva, re..,aWekl County are
Dieale''sWeld County's policies concerning flow carrying capacity, sometimes in the form ofsteep-banked gulches,which have eroding
stability,maintenance,and enhancement of the urban environment banks and bosoms. On Me other hand, many natural waterwayysa
and widlife habitat. The following discussion on bioengineered exgt in urbanized antl to-beurbanized areas which have mild
channels interfaces closely with Section 4.2, Wetland Bottom slopes.are reasonably stable,and are not currently degrading H
Channels, and Section 4.6, Natural Channels; designers are the channel will be used tu carry storm runoff from an urbanized
encouraged to read.Sections 4.2, 4.5 and 4.6, concurrently. In area,it can be assumed that the changes in the runoff regime w81
addition,because bioengineered channels require some structural nscrease channel erosion and instabil Careful hydraulic analysis
9 is needed to address this project erosion. In most cases,
assistance to maintain stability in urban settings, the designer
stabilization of the channel will be required. Stabilization using
is referred to guidance on drop structures in t HYDRAULIC ^gi^ techn" P
STRUCTURES chapter.' an goes.descrtbad in Section 4.5 of this chapter,
•
has sie advantage W preserving and even enhancing the natural
20. Amend Section 4.5.3 Bioengineering Resources to read: m a surer andalso be reof the channel. Some ith the al stabilization
measures cats also re required in cembinatlon cash the bioengineered
"The purpose of this section is to provide the designerwithan overview stabilization measures.
of bioengineering and basic guidelines for the use of bloengineered
In
channels on major drainage projects within 8,..D:.A;,AWeld County. drops Weld County,most natural waterways will need
There are many sources of information on bioengineering that the the^rseen bcr erosion cutoff check structures to maintain a mild
designer should consult for additional information when planning n ��sti and to control channel erosion. T ically, these
and designing a bioengineered channel(Watson.Biedenham,and grade hat is aspaced to limit channel degradation to
Scott 1999;USFISRWG 1998;Riley 1998;and Biedenham, Elliot, whaturbanizationexpect d totributaryafinal stable longitudinal slope after full
and Watson 1997)." watershed. In the Denver area, this
ob slope,
k,range from 0 2 to 0 6%with the South Platte R size and channel soils, tiveriself
21. Amend the first two paragraphs of Section 4.5.4 Characteristics approach) a sl
of Bioengineered Channels to read: en
should be ke pt inns near a natural condition a.1%. Whenever slp natural channel
"The following characteristics aregenerally associated with modifications to those necessary to protectpossible sy limiting
bioengineere channels: hydrologic forces caused by urbanization."
against the destabilizing
1. Their design must address the hydrologic changes associated 30.re Amend the fifth paragraph of Section 4.6 Natural Channels to
with urbanization (increased peak discharges, increased runoff
volume,Increased base flow,and increased bank-full frequency). 'The following design d
These changes typically necessitate the use of grade control natural charm ' criteria are recommended when evaluating
structures. In the absence of grade control structures,especially
els:
in the semi-arid climate of e,.,D,.n.,,. .......Weld County,purely
tuioen sneered channels will normally be subject to bed and bank 1. The channel and overbank flood plain should have
erosion,channel instability,and deradation capacity for the 100-yearflood. W adequate
2. A water surface profile should be defined in order to identify the
2. In addition to grade controls,mesl-bioengineered channels may 100-year floodplain,to control earthwork,and to build tit res
require some structural methods to assist the vegetation'with Good wooer consistent with Me-Bisti 'p 4 L.,,elWeld Countys
maintaining channel stability. Examples include buned riprap on floodplain regulations and ordinances.'
toes and outer channel banks,(see Figures MD-16,MD-17 and No change to remainder of section.
22. Add the following to the last paragraph of Section 4.5.4 Section 8-11-40. Weld County Addendum to the Text of the Urban Storm
Characteristics of Bioengineered Channels:'Weld County is open Drainage Criteria-Volume 2
to review and accept alternate bioengineering methods that provide
protection to toe of bank slopes(i.e.Jacks and lunkers,etcetera)." A.Chapter 8-Hydraulic Structures.
23. Amend the first paragraph of Section 4.5.5 Advantages of 1. Add the following to Section 4.1.2 Bridge Opening Freeboard:The
Bioengineered Channels to read: bridge low chord elevation shall be a minimum of 1-
100-year water course energy grade line.' foet above the
"Public reaction to bioengineered channels is generally favorable,
not only im,,.A,,,.—lit...,D..,,....northern Colorado,but also regionally B.Chapter 9-Culverts
and nationally. In contrast to major drainageway stabilization
projects that focus on structural measures,such as concrete-lined
1. Amend the third paragraph of Section 1.1.2 Headwater read:
or riprap-lined channels,bioengineered channels:"
24. Amend subparagraph 6 of Section 4.5.5 Advantages of
Bioengineered Channels to read: ...a,.;.t..,,t is, IL, E....L...,,J .a .,. R..rs.i,y ;ti.:. i.. e...
POLICY thank. of this Memel(Tablas DPI through DP 3). Pe
"6. Create a living system that maywill strengthen over time" tl,..: ,q, .I...,.hi ...ring tl,ol II...,eL.rJ,..d d;.;d..a ere heher than
e,e ek..'ynl aJ...A.cJe,al:,.n.. h,flat t..r.sin,J.,,;,,,.w..d..:d..e
25. Add the following to Section 4.5.5 Advantages of Bioengineered
Channels:"8. Are less costly to maintain." 6.4O ed for the Last disiupt:oa of the ci at.y fa..d;st,;butiun.The
maximum culvert headwater to diameter ratios are:
26. Amend the first paragraph of Section 4.5.6 Technical Constraints
to read: STORM FREQUENCY HEADWATER TO DIAMETER
`The following constraints eremay be associated with bioengineered
channels: 10-Year HW/D<1.0
1. There is only limited experience to rely on for successful
design of urban channels. The majority of the experience with 100-Year HW/D<1.5
bioengineering techniques relates to channels in nonurban
settings. The minimum culvert capacities are:
2. The semi-arid conditions that characterize DenverWeld County
can be at odds with the need for an adequate water supply for
maintaining the vegetation. Careful species selection that reflects STREET MINIMUM CAPACITY
the site's soils and water availability characteristics is essential. CLASSIFICATION
3. A basic design criterion within the D;.e.ctWeld County is to (RECURRENCE INTERVAL)
demonstrate channel stability during the major(100-year)storm, Local . 10-Year
due to public safety and property protection concerns within urban .
areas. There is little evidence (locally, regionally,or nationally) Collector 10-Year
as to whether purely bioengineered channels can withstand 100-
year(or lesser)flood forces. Arterial 10-Year
V
When the flow in a roadside ditch exceeds the capacity of the culvert
and overtops the cross street,the low over the street crown shall not exceed the minor storm and major storm depth limits presented in 5. Amend Section 3.2.2 Empirical Equations for the Sizing of On-Site
Chapter 3,Planning,Section 9.4 of the Weld County Storm Drainage Detention Storage Volumes to read:
Criteria manual.Weld County may require additional culvert capacity
in order to prevent flooding of adjacent properties." "Urbonas and Glidden (1983), as part of the District's ongoing
hydrologic research, conducted studies that evaluated peak
2. Add the following to Section 2.1.1 Energy and Hydraulic Grade Lines' storm runoff flows along major drainageways. The following set
"The hydraulic grade line and energy grade line shall be determined of empirical equations provided preliminary estimates of on-site
for each culvert system and included in the Final Drainage Report. detention facility sizing for areas within B...Mal'...JWeld County.They
Each culvert system shall be profiled on the Final Construction are not intended for use when off-site inflows are present or when
Drawings and shall include the design flow hydraulic grade line." multi-stage controls are to be used (e.g., 10-and 100-year peak
control)at the storage facility. In addition,these equations are not
3. Amend Section 3.5.3 Culvert Diameter to read:"It is the policy of intended to replace detailed hydrdogic and flood routing analysis,
Weld County to require a minimum culvert diameter of 15 inches. or even the analysis using the Rational Formula-based FAA method
Weld County may require additional culvert capacity in order to for the sizing of detention storage volumes. The District does not
prevent flooding of adjacent properties. After the invert elevations promote the use of these empirical equations. It does not object,
have been assumed and using the design computation forms however,to their use by local governments who have adopted them
(e.g., Figure CU-8), the capacity charts (e.g., Figure CU-7), and or want to adopt them as minimum requirements for the sizing of
the noniographs,the diameter of pipe that will meet the headwater on-site detention for small catchments within their jurisdiction. *the
requirements should be determined. Since small diameter pipes eiss sWhere Weld County has a master drainage plan that contains
are often plugged by sediment and debris,it is recommended that specific guidance for detention storage or sizing of on-site detention
pipe smaller than 18 inches not be used for any drainage where facilities,those guidelines should be followed instead. The empirical
this Manual applies. equations are as follows:..'
Remainder of Section-No Change.
Refer to the"Wet County Design and Construction Standards and
Specifications", latest edition, for allowable culvert pipe materials. 6. Amend Section 3.2.4 Multi-Level Control to read:
The Manning's roughness coefficient"n"for all culvert pipe sizing
calculations shall be 0.013 regardless of pipe material (Concrete, "The-DistrieiWeld County recommends that no more than two levels
PVC,or HOPE)with the exception of corrugated metal pipes which of controls, in addition to the WQCV controls, be used for on-site
shall have a coefficient of 0.025." detention facilities. These levels should be the 100-year storm,
in combination with the 5 a-the 10-year storm. More levels of
4. Add the following to the last paragraph of Section 4.1 Projecting control may appear to provide increased protection,but the added
Inlets: "At a minimum,a culvert entrance and outlet shall include complexity of design and the questionable accuracy of the extended
a flared end section. Erosion protection(rtprap,etcetera)may be precision for such requirements rarely justify their use. Design
required." Example 6.1 shows calculations of allowable release rate and
storage requirement using empirical equations:
5. Amend the fifth paragraph of Section 8.0 Trash/Safety Racks to
read: 7. Add the following to Section 3.3 Design Storms for Sizing Storage
Volumes: "The 10-year and 100-year storms shall be the den
The D:..t.:,,tWekt County strongly recommends against the storms for all water quality and detention pond designs,respectively,
installation of trash racks at culvert outlets, because debris or within Weld County."
a person carried into the culvert will impinge against the rack,
thus leading to pressurized conditions within the culvert, virtually 8.Amend Section 3.3.2 Drainage and Flood Control to read:
destroying Its flow capacity and creating a greater hazard to the
public or a person trapped in the culvert than not having one." "Sizing of storage facilities and outlet works for flood control purposes
is generally based on whether the facility is on-site or regional. For
6. Amend Section 8.1 Collapsible Gratings to read: an individual development site,local municipalities will often dictate
the on-site detention design storms that need to be addressed by
"Th.,Diabi tWeld County does not recommend the use of collapsible the new development. On a watershed level, full system master
gratings. On larger culverts where a collapsible grating is deemed planning studies are needed to identify the appropriate release rates
necessary by a local jurisdiction or an engineer, such gratings for various design storms.Thus,whenever aDi.A.,eterp.e.edNSld-
must be carefully designed from the structural standpoint so that County approved master plan recommends detention sites and
collapse Is achieved with a hydrostatic load of perhaps one-half release rates or on-site detention/retention storage and release
of the maximum backwater head allowable. Collapse of the trash rates, those rates should be used in final design of detention/
rack should be such that it dears the waterway opening adequately retention facilities. Other considerations that have to be taken
to permit the inlet to function properly without itself contributing to Into account include downstream system stability, the stream's
potential plugging of the culvert." capacity to convey discharges from the detention/retention facility in
combination with the downstream runoff contributions to the drainage
C.Chapter 10-Storage system,potential for flood damages to downstream properties,end
other factors that may be specific to each situation at hand."
1.Add the following subparagraph to the sixth paragraph of Section
2.0 Application Of Different Types Of Storage:"6. Above ground 9. Add the following to Section 3.3.3 Spillway Sizing:'Each detention
parking lot detention ponds may be utilized when land area for a pond shall contain an emergency spillway capable of conveying the
grassed lined detention pond is not available. To prevent damage to peak 100-year storm discharge draining into the detention pond.
and floatation of automobiles,parking lot detention ponds shall not The invert of the emergency spillway shall be set equal to or above
exceed 12 inches in depth at any point. Parking lot detention ponds the 100-year water surface elevation. The depth of flow out the
shall have signage to inform the general public about the potential emergency spillway shall be<6 inches and the spillway shall have
for flooding. The 100-year water surface elevation of a parking lot effective erosion protection."
detention pond shall not encroach into a public street."
10. Amend Section 3.3.4 Retention Facilities to read:
2. Amend Section 3.1.2 Use of Regional (i.e., Hydrograph Routing)
Detention Sizing Procedure to read:
"When a retention basin is proposed as a temporary solution to an
evolving drainage problem, L. I iAkAWeld County recommends
"For tributary catchments larger than 90 acres in size,MaDistietWeld that it be sized to capture,as a minimum,the runoff equal to 1.5
County recommends or may require the use of hydrograph flood times the 24-hour,100-year storm plus 1-foot freeboard. The facility
routing procedures(i.e., using CUHP-generated hydrographs and also has to be situated and designed so that when it overtops,no
reservoir routing calculations,see Section 3.4). In addition,if there human-occupied or critical structures (e.g., electrical vaults) will
are upstream detention facilities in the watershed, hydrograph be flooded,and no catastrophic failure at the facility(ag.,loss of
routing methods should be employed. dam embankment)will occur. It is also recommended that retention
facilities be as shallow as feasible to encourage Infiltration and
If off-site tributary areas contribute runoff to an on-site detention other losses of the captured urban runoff. When a trickle outflow
facility,the total tnbutary area,assuming fully developed off-site land can be accepted downstream,one shall be provided and sized in
uses,must be included in the sizing of the on-site storage volumes in accordance with the locally approved release rates, preferably
order to account for the total runoff volume In the watershed.rs Sizing capable of emptying the full volume in 10 to 14 days?
of detention hs that
have ee properly o calculated tolumes o accoufl lnttffor variiable outflow yheaddscharge 11. Amend subparagraph #2 of Section 3.4 Reservoir Routing of
Storm Hydrographs for Sizing of Storage Volumes to read:
rates." "2.Determine Hydrology: Determine the inflow hydrograph to
the storage basin and the allowable peak discharge from the
3. Add the following to Section 3.1.3 Water Quality Capture Volume basin for the design storm events. The hydrograph may be
in Sizing Detention Storage:"Within Weld County the water quality available in published.1.8...,te„iLll„rut—,pl".n.....a,,. ...mr.n
capture volume shall be considered a portion of the total 100-year a=:,•‘-w—..r .,. S1,.. pl.... ,.,,....tWeld County Master Drainage
detention pond volume." Plans or Updates. The allowable peak discharge is limited by
the local criteria or by the requirements spelled out in a District"
4. Amend first paragraph of Section 3.2.1 Maximum Allowable Unit epprovedWeld County-approved master plan.
Release Rates for On-Site Facilities to read:
12. Amend subparagraph#3 of Section 3.4.1 Initial-Sizing to read:
"The maximum allowable unit release rates per acre for on-site
detention facilities for a number of design return periods are listed in "The outflow rate Qo(cis)calculated es:
Table SO-1.These rates apply unless other rates are recommended
in a Eliabld-epprovedWeld County-approved master plan."
2)Sand bluestem at 8.0 pounds of PLS/Acre is used at 25%in'.
the seed mix.
3)Take 25%x 8.0=2.0 pounds of Sand bluestem to use in the "Perforated outlet and trash rack configurations are illustrated in the
mix per acre. TYPICAL STRUCTURAL BMP DETAINS AND SPECIFICATIONS
4)Multiple the 2.0 pounds by the number of acres to get the chapter.Figure EDB-3 equates the WQCV that needs to be emptied
total amount of pounds of the species to use for the mix. over 40 hours, to the total required area of perforations per row
for the standard configurations shown in that section. The chart is
b. NOTE: The seeding rates are listed in Pounds of Pure Live based on the rows being equally spaced vertically at 4-inch centers.
Seed(PLS)per acre,and not in bulk pounds. This total area of perforations per row is then used to determine
the number of uniformly sized holes per row (see detail in the
Refer to the following tables for grass seeding recommendations. TYPICAL STRUCTURAL BMP DETAINS AND SPECIFICATIONS
chapter). One or more perforated columns on a perforated orifice
Table RV-10 GRASS SEEDING TABLES BASED ON RANGE SITES plate integrated Into the front of the outlet can be used; however,
Species indicated in bold italics indicates the preferred species the fewer the number of columns,the better,maximizing the size of
the orifice. Using least number of columns and the largest possible
RANGE SITE:Deed Sands, Choppy Sands, Sandy Bottomland, Sandy orifice, reduces clogging possibilities. Other types of outlets may
Meadow,Sandy Foothills,Sandy Divide also be used, provided they control the release of the WQCV
in a manner consistent with the drain time requirements and are
RANGE SITF:Shaaly Plains,Alkaline Plains,Salt Flat, Salt Meadow, Saline ePProvedaccepted in advance by ihe-BiskietWeld County."
O
verflow
2.Add the following to Section 9.0 Retention Pond(RP)-Sedimentation
•TABLE AVAILABLE IN CLERK TO THE BOARDS OFFICE• Facility:"Retention facilities are normally not allowed in Weld County,
20. Add the following as the last two bulleted items of Section 4.5 but will be considered by Weld County for Mulching: _ special circumstances.
Retention facilities shall be sized to contain a volume equal to
'• At least 70 percent(%).
the mulch by weight shall be ten(10) twice the 100-year storm runoff volume plus one foot of free
inches or more fn leng�. Water within a retention facility shall be mechanically removed d an andd• The appropriate use of fabric blankets under trees and shrubs is disposed of off-site by the property owner within 48 hours after a
suggested.' storm event
21. Amend Section 5.0 Post-Construction Monitoring to read: C.Chapter 4-Typical Structural BMP Details
'Monitoring Is necessary to check the status of revegetation work 1. Amend Table 1 as follows:
and to implement any fellow-up measures needed,such as mowing, [TABLE AVAILABLE IN THE CLERK TO THE BOARD'S OFFICE FOR
weed control,watering,overseeding,etc.This is especially important REVIE
for establishing native species since it may take ree
o five years for vegetation o become adequately established. a. "8. Underdrains elengaccessible from the perimeter of the
should be observed several times during their first two to three permanent pool, including a shutoff valve, are recommended
growing seasons and at least eneetwice a year thereafter. The
guidelines In Section 3.4 should be followed. for Constructed Wetland Basins and a Retention Ponds to help
dewater the pool for rehabilitative maintenance."
Design Examples-Weld County does not have specific values to I 2. Delete, in its entirety, Figure 1 -Typical WQCV Outlet Structure
use for the Cl,C2,and C3 coefficients within the'Detention Volume Profile,Includl 100- r Detention.
by Modified FM Method' spreadsheet. Please use the Urban rig Y�
Drainage and Flood Control District(Denver area)values." - [TABLE AVAILABLE IN THE CLERK TO THE BOARD'S OFFICE FOR
ISection 8-11-50. Weld County Addendum to the Text of the Urban Storm REVIEW]
Drainage Criteria-Volume 3 3. Amend Figure 2 as follows:
A.Chapter 2-New Development Planning (TABLE AVAILABLE IN THE CLERK TO THE BOARD'S OFFICE FOR
1. Amend Section 1.2 Four-Step Process, portion titled 'Step 3' REVIEW]
second paragraph to read:
a. Delete the Overtopping Spillway Option from Figure 2.
'Constructed Grass, Riprap, or Concrete-Lined Channel. This b. Change'Outlet Pipe=120%of 100-YR Capacity'within the Drop
method of channel stabilization has been in practice for some time; Box Outlet Option to'Outlet Pipe= 100%of 100-YR Capacity'
it is described in Volume 2 of the Manual. The water quality benefit within the Drop Box Outlet Option.
associated with these channels is the reduction of severe bed and
bank erosion that can occur in the absence of a stabilized channel 4. Amend Figure 2-a as follows:
On the other hand,the hardlined low flow channels that are often
used do not offer much in the way of water quality enhancement or [TABLE AVAILABLE IN THE CLERK TO THE BOARD'S OFFICE FOR
wetland habitat.Thatirban-Brainegeend-Reed-Gentrel-BlealetWeld REVIEW]
County does not recommend the use of riprap or concrete lined flood
conveyance channels, but does recommend the use of low-flow a. Delete the Overto i channels lined with soil-riprap.' pp rig Spillway Option.
2. Add the following to the last paragraph of Section 1.3 Other BMPs: b. Change"Outlet Pipe=120%of 100-YR Capacity"within the Drop
'Weld County will consider and allow use of new, innovative BMP Box Outlet Drop
Box Outlet'Outlet Pipe= 100%of 100-YR Capacity"
technologies upon review of the proposed BMP(s)on a case by case within the Drop Outlet Option".
basis.'
D.Chapter 5-Maintenance Recommendations
3. Amend second paragraph of Section 1.5.4 Guidance for Selecting 1. Add the Tdk�wirg introductory paragraph prior to Section 1 Grass
and locating WQCV Facilities to read: Buffer: "Weld County will require that all submittals include an
Operations and Maintenance manual for all water quality and
'Laying out WQCV facilities within a development site and watershed detention pond facilities. The operations and maintenance manuals
shall also be distributed to the applicable Homeowners'Association
requires thought and planning. Often,this decision-making occurs
during a master planning process undertaken by beelynri,dieeene manuals ur business llinclude association ios (orequivalent).aan The operations
Weld County. Outrall system plans and other reports
will instructions all installed ns on safe and correct operations,
may depict a recommended approach for implementing WQCV on repair,and maintenance of all equipment and facilities and
a watershed basis. Such reports may call for a few large regional recommended inspection schedules."
WQ Me apV proach.
facilities, smaller sub-regional facilities, or alternatively an E.Chapter 6-Industrial and Commercial Best Management Practices
pproach. It is always a good idea to find out if a master
planning study has been completed that addresses water quality
and to attempt to follow the plan's recommendations.' 1. Add -the following introducory:pangnph under Section 1.0
4. Add Mefollowing to the last paragraph of Section 1.5.5 Incorporating Introduction: 'Weld County will require that all submittals Include
WQCV into Sormwater Quantity Detention Basins: "Weld County an Operations era Maintenance manual for all The
requires that the 100-year detention volume be provided for a given commercial water tunny and detention pond e The
site and allows the WQCV to be incorporated within the 100-year applicable and maintenance manuals shall also beequivalent).
.dTistributed to the
volume." applicable lud park association s ( ea corrtc procedures re operationsfor
• manuals willinclude instructions on safe and correct nt
B.Chapter 3--Structural BMP'S
the operation, repair, and maintenance of all installed equipment
and facilities. The manuals shall provide recommended inspection
1. Amend third paragraph of Section 6.4 Design Considerations to schedules'
' read: •
2. Amend Section 5.0 Structural Controls,Table IC-1 as follows:
[TABLE AVAILABLE IN THE CLERK TO THE BOARD'S OFFICE FOR
REVIEW)
a. Delete 'Retention Pond' and replace with 'Spill Containment
Area.'
0
F. Chapter 8-Construction Best Management Practices 9. Amend paragraph 1.h of Section 1.3.4 Exemptions and Variances to
read:
1. Amend the second paragraph of Section 1.1 General to read:
'h.Where the owner certifies in writing tokxeyaisdkliettWeld County
"An Erosion and Sediment Control Plan must be developed and and the-Ieeeya+adielienWeld County agrees,in writing,that the
submitted to N.,,I...I j..l.Jl.fi..,t. .M.i.. ....•.d•..G,.., .. .;ti planned work and the Rnafstmctures or topographical changes
grading-pemnlWeld County to obtain a grading permit or a building will not result in or contribute to soil erosion or sedimentation
permit. Site planning and drainage planning should, whenever and will not interfere with any existing drainage course in such
possible, occur concurrently with site grading and erosion control a manner as to cause damage to any adjacent property or result
planning.When site grading precedes final development,an erosion in the deposition of debris or sediment on any public way,will not
and sediment contra plan for site grading must be submitted.This Ipresent any hazard to any persons or property,and will have no
plan may have to be mod
dfe at the time a final site development detrimental influence upon the public welfare or upon the total
plan Is prepared.This modified plan must be submitted for review development of the watershed."
and approval prior C to final development? -
2. Amend Section 1.3 Erosion and Sediment Control Plan to read: 10. Amend paragraph 2 of Section 1.3.4 Exemptions and Variances
to read:
"An Erosion and Sediment Control Plan consisting of a written narrativer "2.Variances-
I .... and a site plan map must be submitted to ti-n_, repAeM en, of tit., c. .X..1• an. JJL..,ed -..r•v�v:.t.. •.• hat
`Weld County for review and rsnprovelaccapsnce.
Figures C-1 and C-1A provide standard symbols that can be used on .
•
such plans.An example plan is given in APPENDIX B. The written t,,,,, V.•;......,...d L.....r....,l.N{.,o,... ,...•...nab
narrative report can be a subsection within the drainage report. The
erosion and sediment control plan must include specific inspection the s..bJ:.:..k.n rcg.L.Guns .,,4 .,•,..t J.f.....The Weld County
and repair/maintenance requirements. Engineer may grant variances from the criteria of the Construction
P eq Best Management Practices chapter by his/her acceptance of
3. Amend paragraph#16 of Section 1.3.1 Narrative Report to read: the Final DrainageReport in which the variance request is well
documen •
'16. The following note-"This Erosion and Sediment Control Plan ti. Amend the fourth bulleted item under Section 2.2 Summary of
has been placed in the fir,—.t........of L...I j.•L.J:..M.,�r�Well Criteria to read:
County file for this project.The plan appears to fulfill IMbrMan
eld County )isvehestion. A viable vegetative cover should be established
criteria end- .14.,,erirfo.erosion control that
additional
o at within one year on all disturbed areas and soil stockpiles not
(;••...t........A asur•;.J;.ti.i�. I understand mat nerosion otherwise permanently stabilized. Vegetation is not considered
erosion control measures may be needed if unforeseen erosion established until a ground cover is achieved which,in the opinion
problems occur q if the submitted of ts plan does not function as of II... .�y ,., •ay.A j..;.J,.ti.4 Weld County, is sufficlenty
intended. The requirements land this plan shall run with the land mature to control soil erosion and can survive severe weather
and be the obligation of , i owner oidl ' time as the conditions.(Section 3.3)."
plan is properly completed,modified or voided"
4. Amend paragraph 3.m of Section 1.3.2 Site Plan to read: 12. Amend the 22nd bulleted item under Section2.2 Summary of
Criteria to read:
"m. The following note:"This Erosion and Sediment Control Plan ". Die lion of Temnorary Measnmq.M temporary erosion and
— - ----- - - sediment control measures shall be removed within 30 days after
has been placed in the ..art„a.,,e d Ie,.ol j.,;.J;.t:.l Wald final stabilization is achieved,or after the temporary measures
County file for thispart
and appears to rfulfill applicable are no longer needed,whichever occurs earliest,or as authorized
project PPeb N,. .;1, err...,,y .f I—I jt..;.J;.tM meld County. (Section
erosion control y I understand that owner
additional erosion �•
control to measures unforeseen be required ofstir and his or miher
agents due not Intended.
requirements e if the submitted 13. Amend the second paragraph of Section 2.4.2 Stormwater Quality
plan does function as The of rah
plan shall run with the land and bethe obligation of the land Plans to read:
owner until such time as the plan is properly completed,
modified or voided." 'Wliadyoplocal iasii6tioos ham i•ut be..,. &Moped, aStormwater
5. Replace the current lPlan
text of hSectionllo 1.3.3 Approval of Erosion and qualthe STORMWATER QUALITY Mlans should be ANAGEMENTand BMP PLANNING
consistent with the guidelines in
Sediment Contra Planwim mefolbwing:'A.,C e.:,.n e,•J C.J;..•.,A FOR NEW DEVELOPMENT AND REDEVELOPMENT chapters of
emdine-rede-Bisliffeerfree-Pennir-by-the-isin o. .,..,, t, Ti Volume 3 of the Manual.'
14. Amend the second paragraph of Section 3.3.2 Temporary
Revegetation to read:
"To provide temporary vegetative cover on disturbed areas which will
site-develeement°An Erosion and iment Control Plan must be not be paved,built upon,or fully landscaped within 12 months gut will
accepted prior to issuance of a grading permit or a building permit. be completed within 24 months,plant an annual grass appropriate
The final Erosion and•Sediment Control Plan must be consistent for the time of planting and mulch the planted areas.The annual
with the Drainage Report. Approval of the Erosion and Sediment grasses generally suitable for the Don..... trer.Gt... .•J4Weld
Control Plan does not imply acceptance or approval of Drainage County are listed in Table C-2.These are to be considered only as
Plans,Utility Plans,Street or Road Plans,or any other aspect of site a general recommendation whenever specific design guidance for a
development." particular site is not available."
6. Amend Section 1.3.4 Exemptions and Variances to read: 15. Amend the second paragraph of Section 4.1 Vehicle Tracking to
read:
'A provision for exemptions and variances may be provided by-eeiy "For sites greater than two(2)acres, a stabilized vehicle tracking
to tth eayWckd County.bdi These are generally nd processed according control must be constructed (see Figure C-8).Whenever deemed
to the applicable subdivision regulations and reviewed on a case- necessary by the city u, county of juriadZi,ortWeld County, wash
by-case bass racks shall be installed to remove mud and dirt from the vehicle and
7. Amend paragraph 1.b of Section 1.3.4 Exemptions and Variances to its tires before it enters onto public roads(see Figure C-8A)."
read:
16. Amend the first paragraph of Section 4.3.3 Sediment Basins to
'b.Grading or an excavation below finished grade for basements, read:
fats ,retainingwalls,or other structures en elele->!errodi24— "Areas draining more than 1 acre must be routed through a
ere required
disturbed area will sediment basin similar to one shown in Figures C-15,C-15A,and
be less than one(1)acre in size unless required otherwise." C-16.Sediment basins in N,.. D.,,.., .. ' meld County shall be
8. Amend rah 1.d of Section 1.3.4 Exemptions and Variances to - designed to a minimum 1,800 cubic feet of volume per tributary acre
read:
�� p D and shall be cleaned out prior to becoming half full."
17. Amend the last paragraph of item#2 under Section 5.1 Working
"d.Land-disturbing activities involving less than five(5)—u - eennne((1) Within or Crossing a Waterway to read:
acre of disturbed area.Individual lots involving less than Bve{6?'
eeresone(1)acre of disturbed area M a larger subdivision project
shall not be considered separate development projects,but rather °A permit is required for placement of fill in a waterway under Section
as a part of the subdivision development as a whole.It will be the 404 of the Clean Water Act. The U.S.Army Corps of Engineers
respe sibitity of the homeowner or homebuilder to conform to ail has issued nationwide general permit Number 14 for Minor Road
requirements of the beellyapprevedlocaly-accepted Erosion Crossing Fills. This is defined as placement'of less than 200 cubic
and Sediment Control Plan for the subdivision.As part of any yards of fill material below the plane of ordinary high water. The
Building Permit for which a specific erosion control plan is not local office of the Corps should be contacted about the requirements
required,the following statement must be Included: 'We have for obtaining a 404 permit. Th, ey er,a.ny of j.ri.—Ect.o•Weld
reviewed the Erosion and Sediment Control Plan for(subdivision County should also be consulted and can provide assistance. A
name) and agree to conform to a6 requirements contained further discussion on the need for 404 permits is included in Section
therein and all erosion control requirements of the(insert name of 2.1,MAJOR DRAINAGE,of the Manual?
local jurisdiction).We further agree to construct and maintain all 18 Amend the first paragraph of Section 5.3 Outlet Protection to
erosion and sanera control measures required on the individual
kA(s)tau to this Building Permit and/or in accordance with . read: ,r.,
aFgns fynesn.Cororol sera of the Manual of the
and Reed d*lvolab le
"To protect adjacent downstream properties from erosion due. /O
to.concentrated flows, a stable outlet or channel is necessary. If The purpose of the Sketch Plan Drainage Report, submitted at the
there is no stable outlet, one may have to be constructed. In lieu Sketch Plan Review stage of the Planning Review process,is to identify and
of constructing a temporary or permanent outlet to the storm define conceptual solutions to storm drainage problems which may occur
drainageway s stem, temporary total retention of the runoff horn on-site and off-site as a result of the proposed development. In addition,
by iha k,cel o wui+ ',oat be obb;innd for total rclu,Gan of those problems that exist on-site prior to development must be addressed
aMnnnoMmray be considered on a case-by-case basis upon during the conceptual phase. For proposed projects that will have rural
y levels of development,the Department of Public orks will review the site,
acceptance from Weld County." surroundings, and proposed improvements and advise the applicant as to
19. Amend Section 8.0 Disposition of Temporary Measures to read: what additional information,and/or engineering design may be required for
POe P rY Change of Zone and Final Plat approvals.
"All temporary erosion and sediment control measures shall be A.All reports shall be typed on 8.5-inch by 11-inch paper and bound.
removed and disposed within 30 days after final site stabilization is Drawings measuring 24 inches by 36 inches may be included, as
achieved,or after the temporary measures are no longer needed, needed. The drawings shall be bound within the report or included
whichever occurs earliest,or as authorized by ti A..:tr er,.e,...11 of within a pocket attached inside the back cover of the report. The report
beeynriadlelienWeld County and applicable coordinating agencies needs to stand-alone,therefore, all important reference material and
(COOT,CDPHE). For example,a site containing only one building supporting documents and calculations should be copied and included
will have temporary erosion control measures removed after building within the report appendix. The report shaH include a cover letter
construction is complete and final landscaping is in place.Temporary presenting the conceptual design for review and shall be prepared
erosion control measures may be removed from a commercial- or supervised by an engineer licensed in Colorado. Only anginal
construction site or residential subdivision only after streets are paved documents sealed in ink will be accepted. The sealed"report shall
and all areas have achieved final stabilization. Trapped sediment contain a certification sheet as follows:
and disturbed soil areas resulting from the disposal of temporary
measures must be returned to final plan grades and permanently 1. "I hereby certify that this report for the conceptual drainage design
stabilized to prevent further soil erosion._The-The Engineer of(Name of Development)was prepared by me(or under my direct
M-r..„s tl..........:........J.,,.J:.....,a......t,.I,M„.,l„M.,.6...@,...,Y..i! supervision)in accordance with the provisions of the Weld County
storm drainage criteria for the owners thereof.' ,
.The Registered Professional Engineer
Professional Engineer preparing the construction phase erosion
and sediment control plan shall obtain the approval of Weld County State of Colorado No.
before removal of any temporary measures?
(Affix Seal)20. Amend the second paragraph of Section 9.0 Maintenance to •
read: B.Sketch Plan Drainage Report Contents.Sketch Plan Drainage Reports
shall be prepared in accordance with the following outline and contain
the applicable information listed:
.i, j,Arynt,W ,.,.61IHO4WL. L., ,��.nd � u LR 1. General Location and Description. -
e....o:..A...l ..Iq tlw A,.,.l .,f ...-:..L......... ....r..L..J fi., tl... ..,..,t„A a. Location.
y .o,............J. .. .....-JOr,.,A.tL ..,r.The Professional Engineer preparing
the permanent erosion and sediment control plan shall submit a 1)Township;Range,Section,Quarter Section.
schedule of planned inspection and instructions for operations and
maintenance for all Installed pennanenterosion and sediment control 2)Local streets within,and adjacent to,the development.
measures. The plan shall include identification and specifications
(size,materials,etcetera)of parts and equipment potentially needing 3)Major open channels, lakes, streams, irrigation and other
repair or replacement over the life of the installed measures. A water resource facilities within and adjacent to the proposed
copy of the inspection schedule and instructions for operations development.
and maintenance shall be provided to the applicable Homeowners'
Association or Business Park management(or equivalent)." 4)Names of surrounding developments including jurisdictions
. (municipalities).
21. Add Section 10.0 Erosion and Sediment Control Warranty to read: I
'Prior to acceptance and approval of all installed permanent erosion b. Description of Property
:\C and sediment control measures,Weld County will require that the
owner shall warrant the measures shown on the approved erosion 1)Area in acres.
and sediment control plan are properly constructed, installed,and
are free from defective materials and/or defective workmanship: 2)Ground cover.
Section 8-11-60. Enforcement responsibility. ' 3)Major open channels and ownership.
ft shell be the duty of the Weld County Department of Public Works to 4)general project description.
Criteria using the and enforce the provisions of the Weld County Storm Drainage .
following guidelines: 5) Irrigation facilities and ownership information.
A.In the interpretation and application,the provisions of the Weld County 6)Groundwater characteristics(where applicable).
Storm Drainage Criteria shall be held as the minimum requirements for
promotion of the health,safety,and general welfare of the community. 2. Drainage Bain and Sub-Basins.
B.The Weld County Storm Drainage Criteria is not intended to interfere a. Major Basin Description.
with,abrogate,or annul any other regulation,statute,or other provision -
of law. 1)Referent's to applicable Weld County or adjacent county
Master Drainage Plan(s). ,
C.Where any
provision of the Weld County Storm Drainage Criteria I
Imposes restrictions different from those imposed by any other 2)Major basin brainage characteristics.
provisions of the Weld County Storm Drainage Criteria,or any other
regulation or provision of law,that provision which is more restrictive or 3)Identification d1'all irrigation facilities within 200 feet of the
imposes higher standards shall govem. property boundary.
D.The Weld County Storm Drainage Criteria is not intended to abrogate 4)Identification of all FEMA-defined 100-year floodplains and
any easement,covenant,or any other private agreement or restriction, floodways affecting the property.
provided that where the provisions of the Weld County Storm Drainage
Criteria are more restrictive or impose higher standards or requirements b. Sub-Basin Description.` '
than such easement,covenant,or other private agreement or restriction,
the provisions of these regulations shall govem. 1)Historic drainage patterns on the subject property and adjacent
Division 2
Drainage Planning Submittal Requirements properties.
Section 8-11-100. Review process. 2)Off-site drainage flow pattems and impacts on the subject
Progeny.
All new developments and subdivisions within the jurisdiction of the Weld 3. Drainage Facility Design.
County Storm Drainage Criteria shall submit drainage reports,construction
drawings,and existing condition and as-built information in accordance with a. General Proposed Concept.
the requirements of this Article.
Section 8-11-110. Sketch Plan Drainage Report. 1)Proposed concept and typical drainage patterns.
2)Compliance with off-site runoff considerations and
, constraints.
3)Anticipatedand proposed drainage patterns.
4)Identify all requests for variance from Weld County Storm
Drainage Criteria.
b. Specific Details. water resource facilities within,and adjacent to,the proposed /
1)Describe design storms and source of design storm depth development.
information (Pl9AANational Oceanic and Atmospheric 4)Names of surrounding developments including jurisdiction
Administration Atlas, Urban Drainage and Flood Control (municipalities)
District maps,etcetera).
b. Desaiptlorr of Properly.
2)Drainage problems encountered and proposed solutions at
specific locations. 1)Area in acres.
3)Maintenance access and aspects of the proposed design. 2)Ground cover.
C.Sketch Plan Drainage Report Drawing Contents. 3)Major open channels and ownership.
1. A General Location (vicinity)Map shall be provided at a scale of 4)General project description.
1"=2000'or larger in sufficient detail to identify upstream off-site
drainage areas flowing into the proposed development and general 5)Existing irrigation facilities and utilities and ownership
drainage patterns. information.
2. A Drainage Plan of the proposed development shall be provided at 6)Groundwater characteristics(where applicable).
a scale from 1"=100'or 1"=200'on a 24'x 36"drawing. The plan
shall show the following information: 2. Drainage Basins and Sub-Basins.
a. Existing contours at 2-foot maximum intervals,contours should a. Major Basin Description.
extend at least 200 feet from all project boundaries,or further
if necessary, to show upstream and downstream drainage '1)Reference to Weld County Master Drainage Plan(s)where
relationships impacting the proposed development.
applicable.
b. Properly lines,existing and proposed lot lines,and existing and 2)Major basin drainage characteristics.
proposed easements.
c. Streets with names. 3)Identification of all irrigation facilities and utilities within 200 feet
of the property boundary.
d. Existing drainage facilities, pipes,structures, irrigation facilities, b. Sub-Basin Description.
and sizes.
1)Historic drainage patterns on the subject property.-
e. Overall drainage area boundary and sub-area boundaries.
f. Proposed flow directions using arrows 2)Off-site drainage flow patterns and impacts on the subject
development.
g. Conceptual location of storm sewers, swales, open channels, 3. Drainage Design Criteria.
culverts,detention ponds,and other appurtenances.
h. Identification of outfall locations and receiving waters. a. Regulations: Discussion of the optional criteria selected or the
deviation from the Weld County Storm Drainage Criteria,if any.
i. Location of all defined 100-year floodplains affecting the b. Development Criteria Reference and Constraints.
property.
Any other items so noted within the Drainage Report. 1)Discussion of previous drainage studies(i.e.,project master
j. 9 poplans)for the subject property that influence,or are influenced
Section 8-11-120. Change of Zone Drainage Report. lans willll%flea drainage design�for the sn and rtew the studies and
The purpose of the Change of Zone Drainage Report is to identify and -- 2)Discussion of site constraints such as slopes,streets,utilities,
define preliminary solutions to problems•which may occur on-site and off-site existing structures,and the proposed development or site plan
as a result of the proposed development. In addition,those problems that impacts on the proposed drainage plan.
exist on-site prior to development must be addressed during the preliminary
phase. c. Hydrological Criteria.
A.All reports shall be typed on 8.5-inch by 11-inch paper and bound.
Drawings measuring_24 inches by 36 inches shall be included, as i)NOAANatonaydesign rOcfallic At o phenc Ad inistatiortnias,
needed. The drawings shall be bound within the report or included UGMNaai na a and Flood and Control District
c t maps,eera
within a pocket attached inside the back cover of the report. The Urban Drainage and District maps,etcetera).
Change of Zone Drainage Report needs to stand-alone,therefore,all 2)Identify design storm recurrence intervals.
important reference material should be copied and included within the
report appendix. The report shall include a cover letter presenting the 3)Identify runoff calculation method(s) and any computer
preliminary design for review and shall be prepared or supervised by an models.
engineer licensed in Colorado.Only original documents sealed in ink
will be accepted. The sealed report shall contain a certification sheet 4) Identify detention discharge and storage calculation method(s)
as follows: and computer models.
1. 1 hereby certify that this report for the preliminary drainage design 5)Discussion and justification of other criteria or calculation
of(Name of Development)was prepared by me(or under my direct methods used that are not presented in,or referenced by,the
supervision)in accordance with the provisions of the Weld County Weld County Storm Drainage Criteria.
storm drainage criteria for the owners thereof."
d. Hydraulic Criteria.
Registered Professional Engineer
1)Identify capacity references and any computer models.
State of Colorado No. • 2)Identify detention outlet type.
(Affix Seal)
3)Identify check/drop structure criteria used.
B.Change of Zone Drainage Report Contents. The Change of Zone 4)Discussion of other drainage facility design criteria used that
' Drainage Report shall be in accordance with the following outline and are presented in the Weld County Storm Drainage Criteria.
contain the applicable information listed:
1. General Location and Description. 4. Drainage Facility Design.
a. Location. a. General Concept.
1)Township,Range,Section,Quarter Section. • 1)Discussion of concept and typical drainage patterns for
historical conditions.
2)Local streets within,and adjacent to,the development. 2)Discussion of compliance with off-site runoff considerations
3)Major open channels, lakes, streams, irrigation and other and constraints.
_. 3)Discussion of the content of all tables, charts, figures, or
drawings presented in the report.
4)Discussion of anticipated and proposed drainage pattems.
b. Sped&Deals.
1)Discussion of correlate with drainage criteria(street,inlet, b. Property lines,lot lines,utility crossings,and easements.
and pipe capacities,etcetera).
c. Streets with names.
2)Discussion of drainage problems encountered and solutions at d. Existing drainage facilities, pipes, g
specific design moots' and sis structures, irrigation facilities,
3)Dtscusaion ofdetention storage and outlet design. e. Overall drainage area boundary and sub-area boundaries.
4)Discussion of maintenance access and aspects of the design. f. Proposed contours and flow directions indicated with arrows.
5)Provide copies of Draft Colorado Department of Public Heath
and Environment or State Engineer's permiticatlons g. Location of proposed storm sewers, swales, open channels,
(where applicable) culverts,cross-pans,and other appurtenances.
5.Conclusions. h. Proposed outran point(s)for runoff from the development area
and facilities to conveydownstream
flows toe the final oudall point without
a. Compliance with the Weld County Storm Drainage Criteria. damage to downs tv properties.
b. Drainage Concept. iLocation and elevations f all defined 100-year floodplains and
property.
100-year fioodplains and Lays affecting
1)Effectiveness of drainage design to control damage from storm
runoff. j. Location and types of proposed permanent erosion control
features.
2)Influence of proposed development on any applicable Weld
County Master Drainage Plan recommendations. Section 8-11-130. Final Drainage Plan Report.
3)Identification and written approval of affected Irrigation company The purpose of the Final Drainage Report is to update the preliminary
or other property owner(s). Weld County may require that the design concepts,and to present the design details for the drainage facilities
applicant provide evidence that off-site impacted jurisdictions discussed in the Change of Zone Drainage Report. Also, any change to
have been notified of the proposed drainage plans and the preliminary concept shall be presented. The Final Drainage Report shall
potential impacts. identify all approved requests for variance from Weld County Storm Drainage
Criteria.
8.References.
A.All Final Reports shall be typed on 8.5-inch by 11-inch paper and
a. Reference all criteria and technical information used. bound. Drawings measuring 24 inches by 36 inches shall be included.
The Final Drawings shall be bound within the report or included within
7.Appendices. - a pocket attached inside the back cover of the report. The Final Report
needs to stand-alone, therefore, aft calculations, computer outputs,
a. Hydrology Computations. plans,supporting documents and important reference material should
be copied and included within the report appendix. The report shall
1)Land use assumptions regarding adjacent properties. include a cover letter presenting the final design for review and toll
be prepared or supervised by an engineer licensed in Colorado. Only
2)Initial and major storm runoff computations at specific design original documents sealed In ink will be accep
ted. The sealed report
points. shall contain a certification sheet as follows:
3)Historic and fully developed runoff computations at specific 1. 'I Eby that thle
report sprepared
r for the final(or design al
design points. (Hems d )was prehe pr is me(or under d direct
superviri n)le accordance with e provisions of the Weld
4)Computer model input and output sternrn drainage criteria�the owners thereof."
County
• b. Hydraulic Computations.
Registered Professional Engineer
1)Culvert sizing.
State of Colorado No.
2)Storm sewer sizing.
3)Street capacity evaluation. O
B.Final Drainage Plan Repot Contents. The Final Drainage Report
4)Storm inlet sizing. shall be prepared in accordance with the outline shown above under
Change =Drainage ge Report. In addition to Including alt of the
5)Swale sizing. Items required for the report and plans submitted with the Change of
Zone desalted above fader Change of Zone Drainage Report and
6)Open channel sizing. Drawings,the Feral Drainage Report and Drawin
gs should include:
7)Check dam and/or drop structure sizing. 1. Proposed location and sizing of all atom Sewers swales, ooppean
8)Detention pond area/volume capacity and outlet sizing. channels,culverts,cross-pens,and other appurtenances,including
cross-sections of swabs and open channels.
9)Changes to Calculation Methods-If app4icant/design engineer 2. Routing and accumulation of flows at various critical in
modifies any portion of the Urban Drainage and Flood minor storm runoff. points for the
Control Distnct spreadsheets used for hydrologic or hydraulic
calculations, the applicant/design engineer shall identify all 3. Routing and accumulation of flows at various critical
changes to calculation assumptions or computer programs as major storm nedf. points for the
to type of change end specific factors that were modified.
10) Computer model input and output. 4. Detention storage 100-year water a�.��and [works, including proposed
C.Change of Zone Drainage Report Drawing Contents. 5. Location of all adsti and
n9 proposed utilities.
1. A General Location (vicinity)Map shall be provided at a scale of 6. Routing of off-site drainage flows
1"=2000'or larger in sufficient detail to identify upstream off-site
through the development.
drainage areas flowing into the development, downstream areas 7. Minimum lowest
receiving site flows, and general drainage patterns in the project . buildings opening�eyear waterns of surface residential streets,d commercial
open
above the swales,or ot gefacilities,in a oiled
area channels,thprditches, other drainage
2. A Drainage Plan of the proposed development shall be provided at
by the preliminary grading plans. ^age as illustrated
a scale from 1"=100'or 1".=200'on a 24"x 36'drawing. The plan 8. Proposed on-site private and public
shall show the following information: drainage easements.
a. Existing contours at 2-foot maximum intervals,contours should 9. Proposed off-site private and public drainage easements.
extend at least 200 feet from all project boundaries or further 10. Elevations of manhole and inlet inverts in relation to
if necessary to show upstream and downstream drainage datum. project
relationships impacting the development.
11. Proposed water surface elevations for street encroachments for
the minor and major storm.
12. Critical hydraulic structure dimensions.
13. Orifice plate saes.
tv4. Detention pond volumes.
V. AN oho critical hydraulic elevations.
Operations and Maintenance instructions for the proposed
stomhwata d pinata faalities.
r/,
/J
17. Construction-PhaseConstruction-Phase Erasion and Sediment control calculations.
18. Permanent Erosion and Sediment control calculations.
6. Payment of permit fees must precede final acceptance.
C.The Final au Report desied hydraulic the final shall be
provided for each of the proposed memLS of the drainage B.Submission.
design.
Section a-11-140. 1. The project record drawings shall be submitted to,and accepted by,
Construction Drawings and Specifications, the Weld County inspectors with a transmittal letter containing the
following: .
A.We Fithe nal drainage i provemens are to be constructed in accordance with
Drainage Report,the signed and sealed construction a. Date.
plans (on 24'x 36' )and specifications shall be submitted in conformance with the Fins Plat for review and acceptance prior to b. Project Title.
improvements. sealed plans and specifications for the drainage -
iFive)Drainage lxaade all drainage components designed within c. Design Engineer's name,address,and telephone number.
Report.
d. Title and number of each Record Document.
B.The information required for the drawings and specifications shall be in accordance with sound engineering ndples the Weld County e. Engine
ering tam the Design Engineer and their Professional
development
Drainage Criteria, and the WW County requirements fo !3 9 P
de elopude t and subdivision design. Construction documents shay
geometric, dimensional, structural, foundation, bedding, 2. The initial acceptance Weld County
the storm drainage improvements aces will s not
hydraulic, landscaping,erosion control, and other details as needed be made until ro all Weld Record
installation requirements iedan are ptedfiby
tto t stone drainage facilities. The accepted Final Drainage and the Project Record Drawings are received and accepted by
facilities included as part of the construction doc umens f Weld County.
cns aria affected
tedtby the drainage plan. Submittal of digital format final
may also be required by the Weld Co 3. e of e drainage improvements col not be made until
rtment of Pubic Wonaios. Weld County requires a minimum of three all f to-siteraiaae improvements e have beenb a Aceeotesite
sets of paper cure6ucson plans for use by Weld County inspectors, dr storm dawn a me swill not made until tallo off-site
drainage easement agreements have been signed and notarized.
C.WWhere ererosion ed M coned and sediment control improvements are to be
accordance with the accepted Final Drainage Report, 4. The final drawings j of the storm Drawings
ere received
will noted
the erosion sediment control construction made WelduntilCounty.the Project Record Drawings are received and accepted
36'mylar)end sPecifmalors shall be submitted in conformance with .by
the Final Mat for review and acceptance prior to construction. The
plans and specifications for the erosion control and sediment control 5. Weld County requires that the Project Record Drawings be
improvements shat include all erosion control and sediment control submitted in blueline form for m tai of igit acceptance final n final
components designed within the Final Drainage Report. mylars are submitted. Submittal of digital requi plans Weld
D.Both digital format as-built drawings may also be required by the Weld
post.pomstrudyn (permanent) County Department of Public Works.
erosion and construction drawings shall be
ersntted, The mace erosionBE IT FURTHER ORDAINED by the Board that the Clerk to the Board
sudrawings shat be submitted separately p sediment fr be, and hereby is, directed to arrange with for amendments
Code Publishing to
control ccostruction
drawIngS (permanent) erosion control and sediment control csupoincide
the Weld County Code, the a ecndnsn and contained t herein,as
control and sediment l�and Post-construction phase erosion to they currently
with exist s within said
articles,divisions,sections, sub sections as
construction drawings shall be the basis d curtentty said Code; and to resolve any inconsistencies
compliance evaluations by Weld Coady inspectors.
Section 811-150. ASbuil drawings. pant' capitalization,grammar,and numbering or placement of shapers,.
curet d8 as,dNistons,sections,and sub-sections in said Code.
A,Recording of Drawings. _ BEAT FURTHER ORDAINED by the Board If subsection,
section, subse ,
1. The project record drawings be to,and accepted by, paragraph,sentence,clause,or phrase of this Ordinance is for any reason Mid
Weld County. Drawings g beshall submitted esubmitted appropriate and
form - of decided to be unconstitutional,such decision shall not affect the validity of
when requested by the County. the remaining portions hereof. TheBoard ofCounty Commissioners hereby
declares that it would have enacted this Ordinance in each and every section,
subsection,paragraph,sentence,clause,and phrase thereof. of
2. Each drawing shall be labeled'DRAWINGS OF RECORD'in neat
large printed letters. the fact that sentences,
any one or more sections,subsections,paragraphs,sentenc ,
clauses,or phrases might be declared to be unconstitutional or invalid.
3. Construction information shall be recorded concurrently with
construction progress by the contractor. N O T I C E
4. Project Record Drawings shall be marked legibly and with an PURSUANT to the Weld County Home Rule Charter,Ordinance Number
indelible pen. 2006-7 published above, was introduced and, on motion duly made and
seconded, approved upon first reading on September 11, 2006. A public 5. Project Record Drawings shall record actual construction and
hearing and second reading is scheduled to be held in the Chambers the
contain,but are not limited to,the following:
Board,First Floor Hearing Room,915 10th Street,Greeley,Colorado 80631,
a. Field dimensions,elevations,and details. on October 2,2006. All persons in any manner interested in the reading of
said Ordinance are requested to attend and may be heard.
b. Field changes which are made by minor deviations to the design Please contact the Clerk to the Board's office at phone(970)336-7215,
drawings. Extension 4225,or fax(970)352-0242,prior to the day of the hearing If,as
the result of a disability,you require reasonable accommodations in order to
participate in this hearing.c. Details,which are not on the original Construction Drawings.
Any backup material,exhibits or information previously submitted to the
d. Elevations of manhole and inlet inverts in relation to project Board of County Commissioners concerning this matter may be examined
datum. in the office of the Clerk to the Board of County Commissioners,located in
the Weld County Centennial Center,Third Floor,915 10th Street,Greeley,
e. Critical hydraulic structure dimensions. Colorado, between the hours of 8:00 a.m.and 5:00 p.m.,Monday thru Friday,
or may be accessed through the Weld County Web Page (www.co.weld.
f. Orifice plate sizes. cogs). E-Mail messages sent to an individual Commissioner may not be
included in the case file. To ensure inclusion of your E-Mail correspondence
g. Detention pond volumes. into the case file,please send a copy to egesick@co.weld.co.us.
h. All other critical hydraulic elevations. SECOND READING:October 2,2006,at 9:00 a.m.
THIRD READING:October 23,2006,at 9:00 a.m.
g. Floodplain and floodway delineations and Base Flood Elevations BOARD OF COUNTY COMMISSIONERS(BFEs)where applicable. WELD COUNTY,COLORADO
h. Dimensions of erosion control installations. DATED:September 15,2006
PUBLISHED:September 20,2006,in the Fort Lupton Press
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