HomeMy WebLinkAbout20151832.tiff EXHIBIT
3 Cep 0242/Stu
WELD COUNTY catias eetrzy,
CODE ORDINANCE 2015 - 11
IN THE MATTER OF REPEALING AND REENACTING , WITH AMENDMENTS , CHAPTER 8
PUBLIC WORKS AND CHAPTER 23 ZONING , 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and hereby are , repealed and re-enacted , with amendments , and the various Chapters are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 read as follows .
CHAPTER 8
PUBLIC WORKS
Delete Article XI from Chapter 8 , in its entirety .
CHAPTER 23
ZONING
Amend Section 23- 1 -90 . Definitions .
For the purposes of this Chapter, certain terms or words used herein shall be interpreted
as defined in this Section . The following specific words and phrases , when appearing in this
Chapter in uppercase letters , shall have the meanings stated in this Section :
ACCESSORY BUILDING or USE to NONURBAN SCALE DEVELOPMENT — No change .
Add NON - URBANIZING : An area greater than a IA mile from municipal boundaries , as amended .
Add URBANIZING : An area within 1/4 mile from municipal boundaries , as amended .
Remainder of Section — No change .
Chapter 23 Article XII will be added in its entirety.
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e
ARTICLE XII
Storm Drainage Criteria
Division 1
General Provisions
Section 23-12 -10 . Intent.
A . The intent of the Weld County Storm Drainage Criteria is to provide minimum standards
to preserve and protect the public health , safety and general welfare in the
unincorporated lands of the County , pursuant to authority granted by Part 4 of Article 15
of Title 30 , and Article 35 of Title 30 , C . R . S .
B . Adequate drainage is necessary to preserve and promote the health , safety , general
welfare , and economic well being of the County . Drainage is a regional issue involving
multiple governmental jurisdictions and affecting all property parcels . This makes it
especially critical for drainage systems and programs to address both public and private
needs . The County should be directly involved to provide coordination and master
planning for area-wide drainage facilities .
C . Drainage plans should adhere to generally accepted engineering principles and
practices and should conform to applicable laws and regulations .
D . Application of these policies is supported by technical drainage criteria and data . When
designed and implemented in a comprehensive manner, drainage facilities can be
provided in a manner that will avoid water- related damage to infrastructure , maintain or
improve water quality , and enhance the health , safety , and general welfare of the
County .
Section 23- 12 -20 . Adoption of Storm Drainage Standards .
A . The Urban Drainage and Flood Control District' s " Urban Storm Drainage Criteria
Manual , " ( UDFCD Manual ) consisting of Volume 1 , Volume 2 , and Volume 3 , as currently
published or hereafter amended , is hereby adopted by reference , with the amendments
and additions which are set forth herein . All references to " District" or "The District"
within the UDFCD Manual shall be replaced with "Weld County" . The provisions of this
Article shall be known as the "Weld County Storm Drainage Criteria . " All facilities for
storm water management on properties located within the unincorporated lands of the
County , whether public or private , shall be designed and constructed in accordance with
such criteria , unless a master drainage plan specific to the area of the site has been
approved by the County . The Weld County Storm Drainage Criteria shall be available
on the Weld County Planning Department ' s Website .
B . The criteria and procedures contained in this Article XII are intended to supplement the
UDFCD Manual in ways specific to Weld County . In the case of a conflict between the
UDFCD Manual and the supplemental criteria and procedures in this Article XII , such
supplemental criteria and procedures shall take precedence over the UDFCD Manual .
Section 23 - 12 -30 . Drainage Policy .
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A . 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 .
B . For new development , the Policy of Weld County is to prohibit un -detained discharges to
roadside ditches located in the County right-of-way unless granted by a variance .
C . Except as set forth below , 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 for that location . Stormwater retention facilities are normally
not allowed in Weld County , but will be considered for special circumstances .
D . The Policy of Weld County is to require detention of runoff from the 1 - hour, 100-year,
storm falling on the developed site and release of the detained water at the historic
runoff rate of the 1 - hour , 5-year storm falling on the undeveloped site for URBANIZING
areas and the historic runoff rate of the 1 - hour, 10-year storm falling on the undeveloped
site for NON - URBANIZING areas . Historic is defined as an undeveloped site with a
2 . 0 % imperviousness If the urbanizing jurisdiction has adopted a different historic
runoff rate than that stated in this subsection then the urbanizing jurisdiction runoff rate
shall apply .
E . Weld County will not accept any detention or retention pond that does not drain in less
than 72 hours , causes injury to water rights , or is in violation of state or federal law .
Upon evaluation , improvements may be necessary to downstream capacity .
F . Exceptions .
1 . No stormwater detention will be required for sites that meet any of the following
conditions however, - water quality capture requirements must still be met .
Requirements of the Municipal Separate Storm Sewer System ( MS4 ) areas remain
applicable .
a . Use by Right or Accessory Use in the A (Agricultural ) Zone District .
b . Zoning Permits in the A (Agricultural ) Zone District .
c . A second dwelling permit in the A (Agricultural ) Zone District .
d . Towers including , but not limited to , cell , wind , and telecommunication towers .
e . Pipelines or transmission lines .
f. Gravel pits if the stormwater drains into the gravel pit .
g . Residential developments where all the following conditions exist :
1 . Nine ( 9 ) lots or fewer.
2 . The average lot size is equal to , or greater than , three ( 3 ) acres per lot .
3 . Downstream roadway criteria are not exceeded .
4 . The total post-development imperviousness for the rural residential
development does not exceed ten percent ( 10% ) , assuming that all internal
roads and driveways are paved , or will eventually be paved .
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h . Development of sites where the change of use does not increase the
imperviousness of the site .
i . URBANIZING areas where the total project stormwater runoff of less than , or
equal to , 5 cubic feet per second ( cfs ) for the 1 - hour , 100-year, storm event .
j . NON - URBANIZING areas where the total project stormwater runoff of less than ,
or equal to , 10 cfs for the 1 - hour , 100-year, storm event .
k . Parcels with total area less than , or equal to , a 1 . 0 gross acre .
I . Individual parcel with an unobstructed flow path and no other parcel ( s ) between
the Federal Emergency Management Administration ( FEMA) regulatory
floodplain channel and the project .
m . A parcel greater than 1 gross acre and less than , or equal to , 5 gross acres in
size is allowed a onetime exception for a 1 , 000 sq ft building or equivalent
imperviousness .
n . A parcel greater than 5 gross acres in size is allowed a onetime exception for a
2 , 000 sq ft building or equivalent imperviousness .
o . Approved by a variance .
Separate Storm Sewer System ( MS4)
areas remain applicable:-
b . Zoning Permits in the A (Agricultural) Zone District .
c . A second dwelling permit in (Agric It oral ) one Di +, ±
. ' � v • • v r . v vr .
, and telecommunication towers .
e . Pipelines or transmission lines .
f. Gravel pits if the stormwater drains into the gravel pit .
g-: -Approved by a variance .
Section 23- 12 -40 . Rainfall .
The designer shall use the most appropriate and best available data for the project area in
determining the rainfall quantities .
Section 23 - 12 -50 . Runoff.
A . The Rational Method should not be used to determine runoff for basins larger than 160
acres . In areas located in the southwest portion of Weld County and where areas are
larger than 160 acres that have drainage characteristics similar to an urban area , the
Colorado Urban Hydrograph Procedure ( CUHP ) is an acceptable model for determining
runoff amounts . The CUHP model can be used for basins from 0 to 3 , 000 acres . The
parameter adjustments provided in the runoff chapter of the UDFCD Manual (Volume 1 )
should be used when dealing with basins that are larger than 160 acres .
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B . The CUHP model is not applicable in non - urban areas , including those areas in Weld
County that are outside of the Denver Metropolitan area . The U . S . Army Corps of
Engineers ( USACE ) HEC - HMS model is more applicable for mixed suburban -agricultural
areas . The HEC- HMS model can be used on watersheds and drainage basins larger than
160 acres provided the modeling follows the parameters in the HEC - HMS User' s Manual ,
the HEC- HMS Technical Reference Manual , and the HEC- HMS Application ' s Guide .
C . Weld County in its discretion may accept other methodologies as deemed appropriate by
the design engineer.
Section 23- 12 -60 . Street Drainage .
A . Design Depth Criteria .
1 . The primary design objective is to keep the encroachment of stormwater on the street
or road below an acceptable limit for a given flood return period . When stormwater
collects on a street and flows down a gutter or swale , the stormwater encroaches into
the roadway . If left unchecked , the encroachment will hinder traffic flow and may
become hazardous . The maximum encroachment depth is outlined in the table below:
Road Encroachment
Minor Major
Road Design Max
Classification Max Encroachment Design Storm
Storm Encroachment
over crown
Local 10 yr May spread to crown 100 yr 18 "
Collector 25 yr Leave one lane open 100 yr 12"
Arterial 50 yr No encroachment in lanes 100 yr 0"
B . Inlets .
1 . The design guidelines provided in the streets/inlets/storm sewers chapter of the
UDFCD Manual (Volume 1 ) should be used when designing stormwater inlets . The
standard inlets permitted for use in Weld County streets are shown in the following
table :
Inlet type permitted ( CDOT Types )
Curb opening inlet Type R All street types with 6 inch vertical curb
Grated inlet Type C All streets with a roadside ditch or swale
Grated inlet Type 13 Alley or private drives with a valley gutter
Combination inlet Type 13 All street types with 6 inch vertical curb
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2 . In order to account for factors which decrease the capacity of the inlets such as
debris plugging , pavement overlaying , and variations in design assumptions the
theoretical capacity calculated for inlets is to be reduced by the factors presented in
the following table for standard inlets in Weld County .
Percent of
Condition Inlet Type Theoretical Capacity
Allowed
Sump or continuous grade CDOT Type R
5 ft length 88
10 ft length 92
15 ft length 95
Continuous grade Combination Type 13 66
Sump Grated Type C 50
Grated Type 13 50
Combination Type 13 65
C . Pipes .
1 . The design guidelines provided in the streets/inlets/storm sewers chapter of the
UDFCD Manual (Volume 1 ) should be used when designing stormwater pipes .
2 . The Department of Public Works should be contacted to determine which types of
storm sewer pipes are permissible for use in public rights-of-way or public drainage
easements .
Section 23- 12 -70 . Major Drainage .
A . Design Flows .
1 . The major drainage system must be able to convey the fully developed flow from a
watershed for the 1 -hour, 100-year event without significant damage to the system .
B . Open Channel Design Principles .
1 . Grass- lined open channels conveying less than 50 cfs may reduce the minimum
1 . 0-foot freeboard requirement to the freeboard required to convey 1 . 33 times the
24-hour, 100-year design flow . The reduced freeboard may only occur if a 1 . 0-foot
minimum freeboard is not physically possible and a variance request is submitted .
2 . Maximum side slopes may be as steep as 3H : 1 V . However, the design engineer
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should address how the channels will be maintained since it may not be safe to mow
on slopes that are greater than 4H : 1 V.
Section 23-12 -80 . Culverts .
A . Sizing .
1 . The Department of Public Works should be contacted to determine which types of
storm sewer pipes are permissible for use in public rights-of-way or public drainage
easements .
2 . Culverts must be designed to the following maximum headwater to depth HW/D
requirements .
Design Storm HW/D
10 Yr 1 . 0
100Yr 1 . 5
B . Materials .
Culverts that are to be installed in a public right-of-way that is routinely burned must be
made of either concrete or metal . Plastic pipes will not be allowed in public rights-of-way
that are subject to weed burning .
Section 23- 12 -90 . Storage .
A . Detention Criteria .
1 . Detention ponds shall be sized to store the stormwater runoff generated by the
1 - hour, 100-year storm falling on the developed site and release of the detained
water at the historic runoff rate of the 1 - hour, 5-year storm falling on the undeveloped
site for URBANIZING areas and the historic runoff rate of the 1 - hour, 10-year storm
falling on the undeveloped site for NON - URBANIZING areas . Historic is defined as
an undeveloped site with a 2 . 0 % imperviousness .
2 . The detention pond must include volume for the water quality capture volume . Water
quality capture volume may be included as a portion of the total 100-year detention
pond volume .
3 . Off-site flows can be routed as follows :
•
a . Over the spillway ; or
b . Routed around the site .
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4 . The elevation of the top of the detention pond embankment , except at the spillway ,
must be a minimum of 1 -foot above the 100-year water surface elevation in the
detention pond .
5 . There should be no more than two levels of controls , in addition to the water quality
capture volume controls , for detention ponds . Outlet works should be sized and
structurally designed to release at no more than the 1 - hour, 5-year historic release
rate in URBANIZING and 1 - hour, 10-year historic release rate in
NON - URBANIZING without structural or hydraulic failure . Historic is defined as an
undeveloped site with a 2 . 0% imperviousness . The outlet pipe must contain a
minimum of two concrete cutoff walls embedded a minimum of 18 inches into
undisturbed earthen soil . The cutoff walls must be a minimum of 8 inches thick .
The outlet pipe bedding material must consist of native earthen soil , not granular
bedding material , to at least the first downstream manhole or daylight point .
6 . 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 must be equal to , or above , the 100-year water surface
elevation . The depth of flow out of the emergency spillway shall be less than 6
inches . The spillway must have effective erosion 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 must be sized at the time of final engineering
design . Grouting of the riprap may be required .
7 . In order to prevent damage to publicly-owned infrastructure ( roads , roadside
ditches ) , a concrete cutoff wall 8 inches thick , 3 feet deep , and extending a
minimum of 5 feet into the embankment on each side of the emergency spillway
opening , is required on all privately-maintained detention ponds and required on all
regional detention ponds . The concrete cutoff wall permanently defines the
emergency spillway opening . The emergency spillway elevation must be tied
back into the top of the embankment using a maximum slope of 4 : 1 .
8 . The design of the detention facility must provide evidence that the pond will drain in
less than 72 hours . A detention pond that does not drain in less than 72 hours , can
cause injury to water rights , or is in violation of State or Federal law will not be
accepted .
B . Retention Criteria .
1 . Retention facilities are not allowed in Weld County without the issuance of a
variance .
2 . Retention facilities must be designed to contain 1 . 5 times the volume of the runoff
generated by the 24-hour, 100-year storm , plus 1 foot of freeboard .
3 . The design of the retention facility must include an emergency spillway and must
show that a spill will not adversely impact downstream properties or residences .
The spillway must be designed in accordance with the detention pond spillway
requirements .
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4 . The design of the retention facility must provide evidence that the pond will drain
through the bottom ( sides slopes cannot be used in calculation ) in less than 72
hours . A retention pond that does not drain in less than 72 hours , can cause injury
to water rights , or is in violation of state or federal law will not be accepted .
C . Erosion Protection Design Criteria .
Erosion protection for storage facilities needs to be designed to ensure that the
sediment does not leave the site or impact downstream properties . It may be necessary
to install straw bales , riprap , erosion control logs , erosion control blankets , etc . on the
storage facility side slopes to ensure that erosion does not occur until the reseeded
vegetation is established . The Best Management Practices outlined in the UDFCD
Manual (Volume 3 ) should be used .
Section 23- 12 - 100 . Revegetation .
A . Weld County utilizes the information provided in the Revegetation Chapter of the
UDFCD Manual (Volume 2 ) , and the Best Management Practices Chapter of the
UDFCD Manual (Volume 3 ) . Weld County has seed mixes that are applicable to areas
of the County that are highly recommended . These seed mixes can be found under the
Weld County Public Works Website , Weed Management Section . If noxious weeds , as
listed in Weld County Code Chapter 15 , exist on -site , the appropriate steps need to be
taken before , during , and after work is completed to control their spread .
B . Seeding and Planting .
In addition to the site preparation guidelines outlined in the revegetation chapter of the
UDFCD Manual (Volume 2 ) , if mulching with straw, the straw must be free of seeds and
weeds .
Section 23 -12 -110 . Stormwater Quality.
A . A water quality feature is intended to improve water quality from the impacts of site
development . A water quality feature can be an existing low spot on the property that
currently collects water or an excavated area . The size required is based upon site
imperviousness . This depression is intended to allow stormwater runoff from the site to
collect and settle out any contaminants prior to flowing offsite to neighboring properties
or downstream waterways .
B . An accepted methodology for a water quality feature design can be found in the UDFCD
Manual , Volume 3 , Best Management Practices .
Section 23- 12 - 120 . Best Management Practices .
Weld County uses the Best Management Practices that are outlined in the UDFCD Manual
(Volume 3) Best Management Practices .
Section 23- 12 - 130 . Maintenance.
A . Culverts located outside County- maintained road rights-of-way are not maintained by
Weld County . The owners of those culverts are responsible for their maintenance .
Culverts that are part of a subdivision drainage plan are maintained by the respective
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homeowner' s association . Those culverts should be maintained and cleaned out
annually , per the drainage report maintenance plan , or on an as-needed basis to ensure
proper drainage of the subdivision .
B . To assist drainage pond owners with maintenance , an operations and maintenance
manual for detention facilities and associated infrastructure must be developed and
included with the final drainage report .
C . The property owner/developer, not Weld County , is responsible for site maintenance
and revegetation .
D . 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 . Access must be provided to the drainage facilities for long term maintenance .
Section 23 - 12 - 140 . Enforcement.
The enforcement of this Article shall be in accordance with Article X of this Chapter.
Section 23 - 12 -150 . Stormwater Drainage Criteria Variances .
The following variance procedures are intended to allow additional exceptions to the code
explicitly listed in section 23 - 12-30 provided certain requirements are met. Subsection A
below is intended to be a lower cost option which allows anyone to apply for a variance with
or without stamped engineering documentation. Subsection B below is intended to be used
when more detailed analysis and engineering support is required.
A . An applicant may request a variance for their site when conditions do not meet the
drainage exemptions described previously and impacts to the site and offsite properties
are insignificant. Requests will be reviewed by the Planning Director or his/her designee .
No variance will be considered if it may jeopardize the public health, safety, welfare and
public and private property . In order to be granted, the variance request must :
1 . Demonstrate that granting of the variance will still adequately protect public
health, safety, and general welfare .
2 . Demonstrate there are no adverse impacts, from stormwater runoff, to the public
rights of way and/or offsite properties as a result of the project.
Any engineer' s supporting documentation or analysis has to be signed and stamped by a
licensed PE in the state of Colorado .
If the applicant ' s variance request is denied for not satisfying the above criteria and in
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the sole discretion of the planning director or his or her designee , the applicant has the
option to follow the variance request in subsection B below or appeal the denial to the
Board of Adjustment .
B . The applicant ' s engineer may request a variance . The variance request shall be stamped
and signed by a professional civil engineer licensed to practice in the State of Colorado .
Requests will be reviewed by the Planning Director or his/her designee . In order to be
granted, the variance request must :
1 . Describe the design criteria of the Weld County Code of which a variance is being
requested .
2 . Describe the proposed alternative with engineering rationale which supports the
intent of the Weld County Code .
3 . Meet the design intent of the Weld County Code .
4 . Demonstrate that granting of the variance will still adequately protect public
health, safety, and general welfare .
5 . Demonstrate there are no adverse impacts, from stormwater runoff, to the public
rights of way and/or offsite properties as a result of the project.
An applicant can appeal to the Board of Adjustments the Director of Planning Services
decision regarding the variance per Article VI of this chapter.
C . Variance requests, if accepted, are not precedent setting and are based upon specific site
constraints .
, and signed by a professional -o+v41
engineer licensed to practice in the
Planning Director or his/her designee . In order to be granted , the variance request
must :
howlth of eneral welfare .
2 . Meet the design intent of the- Weld County Code .
3 . Describe i
requested .
/1 . Describe why it is not possible to meet the Weld County Code .
5 . Describe the proposed alternative with engineering rationale which supports the
intent of the Weld County Code .
67- State that no negative drainage impacts are caused
of the project .
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B--- An applicant may be allowed to request a variance for their site when conditions do not
properties may jeopardize the
public health , safety , and welfare of the public .
C . An applicant can appeal , to the Board of Adjustments , the Director of Planning
' Article VI of th-is chapter.
site constraints .-
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
subsections 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 subsections 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 .
PAGE 12
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BEFORE THE WELD COUNTY. COLORADO. PLANNING COMMISSION
RESOLUTION OF RECOMMENDATION TO THE BOARD OF COUNTY COMMISSIONERS
Moved by Bruce Johnson. that the following resolution be introduced for passage by the Weld County
Planning Commission Be it resolved by the Weld County Planning Commission that the application for
be recommended favorably to the Board of County Commissioners
Motion seconded by Benjamin Hansford .
VOTE
For Passage Against Passage Absent
Benjamin Hansford
Bruce Johnson
Bruce Sparrow
Jason Maxey
Jordan Jemiola
Joyce Smock
Michael Wailes
Nick Berryman
Terry Cross
The Chair declared the resolution passed and ordered that a certified copy be forwarded with the file of this
case to the Board of County Commissioner's for further proceedings.
CERTIFICATION OF COPY
I , Kristine Ranslem, Recording Secretary for the Weld County Planning Commission . do hereby certify that the
above and foregoing resolution is a true copy of the resolution of the Planning Commission of Weld County ,
Colorado, adopted on June 2, 2015_
Dated the 2nd of June. 2015.
Digitally signed by Kristine Ranslem
"61-esant 'eattlit. ilet, Date: 2015.06.05 11 :40: 12 -06'00'
Kristine Ranslem
Secretary
2015- 1832
beD 070 /54 /
Delete Article XI from Chapter 8, in its entirety.
Section 23- 1 -90
NON-URBANIZING: An area greater than a '/ mile from municipal boundaries, as amended.
URBANIZING: An area within '/4 mile from municipal boundaries, as amended.
Chapter 23 Article XII will be added in its entirety:
ARTICLE XII
Storm Drainage Criteria
Division 1
General Provisions
Section 23- 12- 10. Intent
A. The intent of the Weld County Storm Drainage Criteria is to provide minimum standards to preserve and
protect the public health, safety and general welfare in the unincorporated lands of the County, pursuant
to authority granted by Part 4 of Article 15 of Title 30, and Article 35 of Title 30, C.R.S.
B. Adequate drainage is necessary to preserve and promote the health, safety, general welfare, and economic
well being of the County. Drainage is a regional issue involving multiple governmental jurisdictions and
affecting all property parcels. This makes it especially critical for drainage systems and programs to
address both public and private needs. The County should be directly involved to provide coordination
and master planning for area-wide drainage facilities.
C. Drainage plans should adhere to generally accepted engineering principles and practices and should
conform to applicable laws and regulations.
D. Application of these policies is supported by technical drainage criteria and data. When designed and
implemented in a comprehensive manner, drainage facilities can be provided in a manner that will avoid
water-related damage to infrastructure, maintain or improve water quality, and enhance the health, safety,
and general welfare of the County.
Section 23- 12-20. Adoption of Storm Drainage Standards
A. The Urban Drainage and Flood Control District's "Urban Storni Drainage Criteria Manual," (UDFCD
Manual) consisting of Volume 1 , Volume 2, and Volume 3, as currently published or hereafter amended,
is hereby adopted by reference, with the amendments and additions which are set forth herein. All
references to "District" or "The District" within the UDFCD Manual shall be replaced with "Weld
County". The provisions of this Article shall be known as the "Weld County Storm Drainage Criteria."
All facilities for storm water management on properties located within the unincorporated lands of the
County, whether public or private, shall be designed and constructed in accordance with such criteria,
unless a master drainage plan specific to the area of the site has been approved by the County. The Weld
County Storm Drainage Criteria shall be available on the Weld County Planning Department's Website.
B. The criteria and procedures contained in this Article XII are intended to supplement the UDFCD Manual
in ways specific to Weld County. In the case of a conflict between the UDFCD Manual and the
supplemental criteria and procedures in this Article XII, such supplemental criteria and procedures shall
take precedence over the UDFCD Manual.
Section 23-12-30. Drainage Policy
A. 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.
B. For new development, the Policy of Weld County is to prohibit un-detained discharges to roadside
ditches located in the County right-of-way unless granted by a variance.
C. Except as set forth below, 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 for that location.
Stormwater retention facilities are normally not allowed in Weld County, but will be considered for
special circumstances.
D. The Policy of Weld County is to require detention of runoff from the 1 -hour, 100-year, storm falling on
the developed site and release of the detained water at the historic runoff rate of the 1 -hour, 5-year storm
falling on the undeveloped site for URBANIZING areas and the historic runoff rate of the 1 -hour, 10-
year storm falling on the undeveloped site for NON-URBANIZING areas. Historic is defined as an
undeveloped site with a 2.0% imperviousness.
E. Weld County will not accept any detention or retention pond that does not drain in less than 72 hours,
causes injury to water rights, or is in violation of state or federal law. Upon evaluation, improvements
may be necessary to downstream capacity.
F. Exceptions
1 . No stormwater detention will be required for sites that meet any of the following conditions;
however, water quality capture requirements must still be met. Requirements of the Municipal
Separate Storm Sewer System (MS4) areas remain applicable.
a. Residential developments where all the following conditions exist:
1 . Nine (9) lots or fewer.
2. The average lot size is equal to or greater than three (3) acres per lot.
3. Downstream roadway criteria are not exceeded.
4. The total post-development imperviousness for the rural residential development
does not exceed ten percent ( 10%), assuming that all internal roads and
driveways are paved, or will eventually be paved.
b. Development of sites where the change of use does not increase the imperviousness of
the site
c. URBANIZING areas where the total project stormwater runoff of less than or equal to 5
cubic feet per second (cfs) for the 1 -hour, 100-year, storm event.
d. NON-URBANIZING areas where the total project stormwater runoff of less than or
equal to 10 cfs for the 1 -hour, 100-year, storm event.
e. Parcels with total area less than or equal to a 1 .0 gross acre.
f. Individual parcel with an unobstructed flow path and no other parcel(s) between the
Federal Emergency Management Administration (FEMA) regulatory floodplain channel
and the project.
g. A parcel greater than 1 gross acre and less than or equal to 5 gross acres in size is allowed
a onetime exception for a 1000 sq ft building or equivalent imperviousness.
h. A parcel greater than 5 gross acres in size is allowed a onetime exception for a 2000 sq ft
building or equivalent imperviousness.
i. Approved by a variance.
2. No stormwater detention or water quality capture shall be required in the following situations.
Requirements of the Municipal Separate Storm Sewer System (MS4) areas remain applicable.
a. Use by Right or Accessory Use in the (A) Agricultural Zone district.
b. Zoning Permits in the (A) Agricultural Zone district.
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c. A second dwelling permit in the in the (A) Agricultural Zone district.
d. Towers including but not limited to cell, wind, and telecommunication towers.
e. Pipelines or transmission lines.
f. Gravel pits if the stormwater drains into the gravel pit.
g. Approved by a variance.
Section 23-12-40. Rainfall
The designer shall use the most appropriate and best available data for the project area in determining the
rainfall quantities.
Section 23-12-50. Runoff
A. The Rational Method should not be used to determine runoff for basins larger than 160 acres. In areas
located in the southwest portion of Weld County and where areas are larger than 160 acres that have
drainage characteristics similar to an urban area, the Colorado Urban Hydrograph Procedure (CUHP) is an
acceptable model for determining runoff amounts. The CUHP model can be used for basins from 0 to 3,000
acres. The parameter adjustments provided in the runoff chapter of the UDFCD Manual (Volume 1 ) should
be used when dealing with basins that are larger than 160 acres.
B. The CUHP model is not applicable in non-urban areas, including those areas in Weld County that are
outside of the Denver Metropolitan area. The U.S. Army Corps of Engineers (USACE) HEC-HMS model
is more applicable for mixed suburban-agricultural areas. The HEC-HMS model can be used on watersheds
and drainage basins larger than 160 acres provided the modeling follows the parameters in the HEC- HMS
User's Manual, the HEC-HMS Technical Reference Manual, and the HEC-HMS Application's Guide.
C. Weld County in its discretion may accept other methodologies as deemed appropriate by the design
engineer.
Section 23-12-60. Street Drainage
A. Design Depth Criteria
1 . The primary design objective is to keep the encroachment of stormwater on the street or road
below an acceptable limit for a given flood return period. When stormwater collects on a street
and flows down a gutter or swale, the stormwater encroaches into the roadway. If left unchecked,
the encroachment will hinder traffic flow and may become hazardous. The maximum
encroachment depth is outlined in the table below:
Road Encroachment
Minor Major
issification ncroachment
Storm lax Encroachment torm
er crown
Local 10 yr May spread to crown 100 yr 18"
Collector 25 yr Leave one lane open 100 yr 12"
Arterial 50 yr No encroachment in lanes 100 yr 0"
B. Inlets
1 . The design guidelines provided in the streets/inlets/storm sewers chapter of the UDFCD Manual
(Volume 1 ) should be used when designing stormwater inlets. The standard inlets permitted for
use in Weld County streets are shown in the following table:
Inlet type permitted (CDOT Types)
_y - - -
Curb opening inlet Type R All street types with 6 inch vertical curb
Grated inlet Type C All streets with a roadside ditch or swale
Grated inlet Type 13 Alley or private drives with a valley gutter
Combination inlet Type 13 All street types with 6 inch vertical curb
2. In order to account for factors which decrease the capacity of the inlets—such as debris plugging,
pavement overlaying, and variations in design assumptions—the theoretical capacity calculated
for inlets is to be reduced by the factors presented in the following table for standard inlets in
Weld County.
Condition Inlet Type Percent of Theoretical
Capacity
Sump or continuous grade CDOT Type R
5 ft length 88
10 ft length 92
15 ft length 95
Continuous grade Combination Type 13 66
Sump Grated Type C 50
Grated Type 13 50
Combination Type 13 65
C. Pipes
I . The design guidelines provided in the streets/inlets/storm sewers chapter of the UDFCD Manual
(Volume 1 ) should be used when designing stormwater pipes.
2. The Department of Public Works should be contacted to determine which types of storm sewer
pipes are permissible for use in public right-of-ways or public drainage easements.
Section 23- 12-70. Major Drainage
A. Design Flows
I . The major drainage system must be able to convey the fully developed flow from a watershed for
the I -hour, 100-year event without significant damage to the system.
B. Open Channel Design Principles
I . Grass-lined open channels conveying less than 50 cfs may reduce the minimum 1 .0 foot freeboard
requirement to the freeboard required to convey 1 .33 times the 24-hour, 100-year design flow. The
reduced freeboard may only occur if a 1 .0-ft minimum freeboard is not physically possible and a
variance request is submitted.
2. Maximum side slopes may be as steep as 3H: I V. However, the design engineer should address
how the channels will be maintained since it may not be safe to mow on slopes that are greater
than 4H: I V.
Section 23-12-80. Culverts
A. Sizing
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1 . The Department of Public Works should be contacted to determine which types of storm sewer
pipes are permissible for use in public right-of-ways or public drainage easements.
2. Culverts must be designed to the following maximum headwater to depth HW/D requirements
Design Storm H W/D
10 y I .0
100 Yr 1 .5
B. Materials
Culverts that are to be installed in a public right-of-way that is routinely burned must be made of either
concrete or metal. Plastic pipes will not be allowed in public right-of-ways that are subject to weed
burning.
Section 23-12-90. Storage
A. Detention Criteria
1 . Detention ponds shall be sized to store the stormwater runoff generated by the 1 -hour, 100-year
storm falling on the developed site and release of the detained water at the historic runoff rate of
the 1 -hour, 5-year storm falling on the undeveloped site for URBANIZING areas and the historic
runoff rate of the I -hour, 10-year storm falling on the undeveloped site for NON-URBANIZING
areas. Historic is defined as an undeveloped site with a 2.0% imperviousness.
2. The detention pond must include volume for the water quality capture volume. Water quality
capture volume may be i nc I uded as a portion of the total 100-year detention pond volume.
3. Off-site flows can be routed as follows:
a. Through the detention pond outlet; or
b. Over the spillway; or
c. Routed around the site.
4. The elevation of the top of the detention pond embankment, except at the spillway, must be a
minimum of I -foot above the 100-year water surface elevation in the detention pond.
5. There should be no more than two levels of controls, in addition to the water quality capture
volume controls, for detention ponds. Outlet works should be sized and structurally designed to
release at not more than the 1 -hour, 5-year historic release rate in URBANIZING and 1 -hour, 10-
year historic release rate in NON-URBANIZING without structural or hydraulic failure. Historic is
defined as an undeveloped site with a 2.0% imperviousness. The outlet pipe must contain a
minimum of two concrete cutoff walls embedded a minimum of 18 inches into undisturbed earthen
soil. The cutoff walls must be a minimum of 8 inches thick. The outlet pipe bedding material must
consist of native earthen soil, not granular bedding material, to at least the first downstream
manhole or daylight point.
6. 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 must be
equal to or above the 100-year water surface elevation. The depth of flow out of the emergency
spillway shall be less than 6 inches. The spillway must have effective erosion 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 must be sized at the time of final engineering design. Grouting of the riprap
may be required.
7. In order to prevent damage to publicly-owned infrastructure (roads, roadside ditches), a concrete
cutoff wall 8 inches thick , 3 feet deep, and extending a minimum of 5 feet into the embankment
on each side of the emergency spillway opening, is required on all privately-maintained detention
ponds and required on all regional detention ponds. The concrete cutoff wall permanently defines
the emergency spillway opening. The emergency spillway elevation must be tied back into the top
of the embankment using a maximum slope of 4: 1 .
8. The design of the detention facility must provide evidence that the pond will drain in less than 72
hours. A detention pond that does not drain in less than 72 hours, can cause injury to water rights,
or is in violation of State or Federal law will not be accepted.
B. Retention Criteria
1 . Retention facilities are not allowed in Weld County without the issuance of a variance.
2. Retention facilities must be designed to contain 1 .5 times the volume of the runoff generated by
the 24-hour, 100-year storm plus 1 foot of freeboard.
3. The design of the retention facility must include an emergency spillway and must show that a spill
will not adversely impact downstream properties or residences. The spillway must be designed in
accordance with the detention pond spillway requirements.
4. The design of the retention facility must provide evidence that the pond will drain through the
bottom (sides slopes cannot be used in calculation) in less than 72 hours. A retention pond that
does not drain in less than 72 hours, can cause injury to water rights, or is in violation of state or
federal law will not be accepted.
C. Erosion Protection Design Criteria
Erosion protection for storage facilities needs to be designed to ensure that the sediment does
not leave the site or impact downstream properties. It may be necessary to install straw bales,
riprap, erosion control logs, erosion control blankets, etc. on the storage facility side slopes to
ensure that erosion does not occur until the reseeded vegetation is established. The Best
Management Practices outlined in the UDFCD Manual (Volume 3) should be used.
Section 23- 12-100. Revegetation
A. Weld County utilizes the information provided in the Revegetation Chapter of the UDFCD Manual
(Volume 2), and the Best Management Practices Chapter of the UDFCD Manual (Volume 3). Weld
County has seed mixes that are applicable to areas of the County that are highly recommended. These
seed mixes can be found under the Weld County Public Works Website, Weed Management Section. If
noxious weeds, as listed in Weld County Code Chapter 15, exist on-site, the appropriate steps need to be
taken before, during, and after work is completed to control their spread.
B. Seeding and Planting
In addition to the site preparation guidelines outlined in the revegetation chapter of the UDFCD Manual
(Volume 2). If mulching with straw, the straw must be free of seeds and weeds.
Section 23-12-110. Stormwater Quality
A. A water quality feature is intended to improve water quality from the impacts of site development. A
water quality feature can be an existing low spot on the property that currently collects water or an
excavated area. The size required is based upon site imperviousness. This depression is intended to allow
stormwater runoff from the site to collect and settle out any contaminants prior to flowing offsite to
neighboring properties or downstream waterways.
B. An accepted methodology for a water quality feature design can be found in the UDFCD Manual,
Volume 3, Best Management Practices.
Section 23- 12- 120. Best Management Practices
-
Weld County uses the Best Management Practices that are outlined in the UDFCD Manual (Volume 3)
Best Management Practices.
Section 23- 12- 130. Maintenance
A. Culverts located outside County-maintained road right-of-ways are not maintained by Weld County. The
owners of those culverts are responsible for their maintenance. Culverts that are part of a subdivision
drainage plan are maintained by the respective homeowner's association. Those culverts should be
maintained and cleaned out annually, per the drainage report maintenance plan, or on an as-needed basis to
ensure proper drainage of the subdivision.
B. To assist drainage pond owners with maintenance, an operations and maintenance manual for detention
facilities and associated infrastructure must be developed and included with the final drainage report.
C. The property owner/developer, not Weld County, is responsible for site maintenance and revegetation.
D. 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. Access must be provided to the drainage facilities for long term maintenance
Section 23-12-140. Enforcement
The enforcement of this Article shall be in accordance with Article X of this Chapter.
Section 23-12-150. Stormwater Drainage Criteria Variances
A. The variance request shall be prepared, stamped, and signed by a professional civil engineer licensed to
practice in the State of Colorado. Requests will be reviewed by the Planning Director or his/her designee.
In order to be granted, the variance request must:
1 . Demonstrate that granting of the variance will still adequately protect public health, safety, and
general welfare.
2. Meet the design intent of the Weld County Code.
3. Describe the design criteria of the Weld County Code of which a variance is being requested.
4. Describe why it is not possible to meet the Weld County Code.
5. Describe the proposed alternative with engineering rationale which supports the intent of the
Weld County Code.
6. State that no negative drainage impacts are caused to offsite properties as a result of the project.
B. An applicant may be allowed to request a variance for their site when conditions do not meet the
drainage exemptions described previously and impacts to the site and offsite properties are insignificant.
No variance will be considered if it may jeopardize the public health, safety, and welfare of the public.
C. An applicant can appeal to the Board of Adjustments the Director of Planning Services decision
regarding the variance per Article VI of this chapter.
D. Variance requests, if accepted, are not precedent setting and are based upon specific site constraints.
Motion : Forward Case USR15-0022 to the Board of County Commissioners along with the amended
Conditions of Approval and Development Standards with the Planning Commission's recommendation of
approval , Moved by Benjamin Hansford. Seconded by Michael Wailes.
Vote: Motion carried by unanimous roll call vote (summary: Yes = 8) .
Yes: Benjamin Hansford . Bruce Johnson . Bruce Sparrow. Jordan Jemiola . Joyce Smock. Michael Wailes,
Nick Berryman . Terry Cross.
CASE NUMBER: ORDINANCE 2015- 11
PRESENTED BY: WAYNE HOWARD
REQUEST: IN THE MATTER OF REPEALING AND REENACTING, WITH AMENDMENTS,
CHAPTER 8 PUBLIC WORKS AND CHAPTER 23 ZONING , OF THE WELD
COUNTY CODE.
Tom Parko. Planning Director. stated that this proposed change goes back about 18 months from
discussion with the Board of County Commissioners. There is a variety of development in Weld County
including urban development and rural development. He added that for years we were applying the
urban drainage standard throughout the County and we didn 't feel that was fair for projects located in
rural areas. So staff has met with several engineers who work in Weld County and we have come up with
these changes. He added that the goal was to be less restrictive and be more flexible.
Wayne Howard , Engineering , reiterated that the overall goal was to lessen the requirements. Mr. Howard
showed the Planning Commission the three ( 3) large manuals that provide tools nationwide and staff is
looking to adopt these manuals and add to it to make it specific to Weld County. Mr. Howard said that the
drainage criteria is located in Chapter 8 and they are proposing to delete that entire Article XI in Chapter 8
and rewrite it into Chapter 23.
Mr. Howard provided an outline of the proposed code changes related to drainage including the addition
of exceptions and variances to drainage. Because there was a major shift. staff tried to be consistent
within Chapter 23.
The Chair asked if there was anyone in the audience who wished to speak for or against this application .
No one wished to speak.
Motion : Forward Ordinance 2015-11 to the Board of County Commissioners along with the Planning
Commission's recommendation of approval , Moved by Bruce Johnson , Seconded by Benjamin
Hansford .
Vote: Motion carried by unanimous roll call vote (summary: Yes = 8) .
Yes: Benjamin Hansford . Bruce Johnson , Bruce Sparrow. Jordan Jemiola, Joyce Smock, Michael Wailes,
Nick Berryman , Terry Cross.
The Chair asked the public if there were other items of business that they would like to discuss. No one
wished to speak.
The Chair asked the Planning Commission members if there was any new business to discuss. No one
wished to speak .
Meeting adjourned at 7 : 05 pm .
Respectfully submitted .
Kristine Ranslem
Secretary
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