HomeMy WebLinkAbout970319.tiffRESOLUTION
RE: APPROVE CACHE LA POUDRE RIVER FLOOD PLAIN INFORMATION STUDY
PLAN OF WORK AMONG COLORADO WATER CONSERVATION BOARD, U. S.
ARMY CORPS OF ENGINEERS, AND CITY OF GREELEY AND AUTHORIZE CHAIR
TO SIGN
WHEREAS, the Board of County Commissioners of Weld County, 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 has been presented with the Cache La Poudre River Flood Plain
Information Study Plan of Work among the County of Weld, State of Colorado, by and through
the Board of County Commissioners of Weld County, the Colorado Water Conservation Board,
U. S. Army Corps of Engineers, and City of Greeley, with terms and conditions being as stated
in said plan, and
WHEREAS, after review, the Board deems it advisable to approve said plan, a copy of
which is attached hereto and incorporated herein by reference.
NOW, THEREFORE, BE IT RESOLVED by the Board of County Commissioners of
Weld County, Colorado, that the Cache La Poudre River Flood Plain Information Study Plan of
Work among the County of Weld, State of Colorado, by and through the Board of County
Commissioners of Weld County, the Colorado Water Conservation Board, U. S. Army Corps of
Engineers, and City of Greeley be, and hereby is, approved.
BE IT FURTHER RESOLVED by the Board that the Chair be, and hereby is, authorized
to sign said plan.
The above and foregoing Resolution was, on motion duly made and seconded, adopted
by the following vote on the 19th day of February, A.D., 1997.
eputy Clerk to the Boar
AP" •V ra AS Tt oRM:
BOARD OF COUNTY COMMISSIONERS
WELDOUNTY, COLORADO
G ore1 r
Baxter, Chair
ete
Constance L. Harbert Pr• em
Dale2K. Hall
/
Th
Barbara J. KirkmeyeF
ty Attorn
/w, Fl; CA
W. H. ebster
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EG0036
RECEIVED
N O V 0 4 1996
Colorado Water
Conservation Board
CACHE LA POUDRE RIVER
CITY OF GREELEY AND
WELD COUNTY, COLORADO
FLOOD PLAIN INFORMATION STUDY
PLAN OF WORK
Prepared by the
Colorado Water Conservation Board
Denver, Colorado
in cooperation with the
U.S. Army Corps of Engineers
City of Greeley, Colorado
Weld County, Colorado
September 1996
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CONTENTS
Page
INTRODUCTION 1
NEED FOR STUDY 1
LIMITS OF STUDY AREA 1
LOCATION MAP 1 of 2
STUDY AREA MAP 2 of 2
TYPE AND INTENSITY OF INVESTIGATIONS 2
CONTENTS OF FINAL REPORT 3
COORDINATION AND RESPONSIBILITIES 4
SCHEDULING 4
FUNDING 5
PRINCIPAL WORK ITEMS 5
STUDY FOLLOW UP 6
ACTIVITY SCHEDULE AND COST ESTIMATES 7
SIGNATURES 9
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INTRODUCTION
This Plan of Work for a floodplain information study of the Cache La Poudre River in Weld
County, Colorado, was prepared by representatives of the Colorado Water Conservation Board,
Weld County, City of Greeley, and U.S. Army Corps of Engineers, Omaha District.
The area to be studied includes the Cache La Poudre River floodplain commencing at its
confluence with the South Platte River thence extending upstream to a point one mile downstream
of Highway 257. The total length of the study area is 18.5 miles. The purpose of this Plan of
Work is to describe the need, define the intended uses of the study findings, type and intensity
of investigations, interagency coordination, study responsibilities, scheduling and funding
arrangements.
In Colorado, the Corps of Engineers and several other federal agencies, Colorado Water
Conservation Board, and private consulting firms under contract to local entities are engaged in
floodplain management studies. As coordinator for all flood -related studies in the state, the
Colorado Water Conservation Board establishes priorities and schedules for these studies on a
priority basis. The Colorado Water Conservation Board and the Corps of Engineers perform
these studies under a joint coordination agreement for floodplain hazard analyses.
The Corps of Engineers carries out floodplain management studies under its technical services
program in accordance with the authority of Section 206 of Public Law 86-645, as amended, and
in compliance with Executive Order 11988, Floodplain Management, effective May 24, 1977.
NEED FOR STUDY
Development is occurring within Unincorporated Weld County and portions of the City of
Greeley in certain floodplain areas. The only floodplain information currently available is an out-
of-date map prepared by the Federal Emergency Management Agency. The available floodplain
information does not present the new hydrology and mapping for existing basin conditions;
therefore, much of the information is unsuitable for guiding the development and preventing
structures which may be considered to be built in the 1990's floodplain. In addition, following
discussions with local residents, reviewing the historic information, and inspecting of the
floodplain conditions, indications are that existing floodplain mapping does not adequately define
the floodplain hazard areas within the Unincorporated Weld County and City of Greeley.
LIMITS OF STUDY AREA
The area to be studied includes the Cache La Poudre River floodplain for a selected stream reach.
The selected stream reach for the Cache La Poudre River commences at its confluence with South
Platte River thence extends upstream to Highway 257 near Windsor, Colorado. The distance for
the floodplain analysis is 18.5 miles. The Cache La Poudre River selected study reach is divided
into three project reaches which are denoted as:
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Reach I - Commences at the river confluence with South Platte River thence
upstream to Ash Avenue which is a distance of 4.6 miles.
Reach II - Commences at Ash Avenue thence upstream to 25th Avenue which is a
distance of 4.0 miles.
Reach III - Commences at 25th Avenue thence upstream to a point one mile
downstream of Highway 257 which is a distance of 9.9 miles.
TYPE AND INTENSITY OF INVESTIGATION
The technical studies to be performed by the Corps in cooperation with its non-federal sponsors
will include the following tasks:
RESEARCH THE RECORDS: Data such as flood history, photos, land use, and other pertinent
information will be collected for use in the study. An assessment will be made of the existing
natural and beneficial values served by the floodplain in the study area.
HYDROLOGIC ANALYSIS: Flood hazard information for the 10-, 50-, 100-, and 500 -year
frequency floods will be developed using existing 1988 published values which are in compliance
with the provisions of the CWCB "Rules and Regulations of the Designation of Floodplains"
dated December 11, 1987.
MAPS AND SURVEYS: Using the topographic maps prepared by the City of Greeley and Weld
County, the Corps will delineate the floodplain information for the 100- and 500 -year frequency
floods and will present these delineations on the sponsor's mapping at a scale of 1 in. = 200 ft.
Data for the approximately 70 cross sections will be obtained from field surveys and
photogrammetric methods. Engineering surveys will also be conducted to obtain dimensions of
bridges and culverts in the floodplain. Field surveys will be coordinated with the vertical and
horizontal datum established by the U.S. Geological Survey and the mapping will meet the
"National Map Accuracy Standards"
HYDRAULIC ANALYSIS: The magnitude, elevation, and location of flooding for the
designated frequency floods will be developed using the 1988 hydrologic values for the hydraulic
analyses using standard Corps techniques and procedure, and the U.S. Army Corps of Engineer's,
HEC-RAS computer program or Corps may use their standard HEC-II version for computing
water surface profiles for Reaches I and III. For Reach II, the Corps will incorporate the City's
existing HEC-II model which was developed by a consultant. The Corps will re -format the model
so a continuous running model will exist for the entire selected stream reach which is the river
reach from the South Platte River upstream to Highway 257.
FLOODWAY ANALYSIS: The Corps will upon completion of the hydraulic modeling of the
channel and floodplain shall perform a floodway analysis in compliance with the County and City
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criteria which is acceptable to FEMA, also.
FLOODPLAIN DELINEATIONS AND MITIGATION MEASURES: Following completion of
the hydrologic and hydraulic investigations, the Corps in cooperation with Weld County, City of
Greeley, Colorado Water Conservation Board, and landowners will address flooding conditions
and evaluate the flood hazard and make recommendations for further study analyses that will
reduce flood risks to life and property. The determined flood hazards will be presented on a
map, supported by technical analysis, and published in a final report.
CONTENTS OF THE FINAL REPORT
A preliminary draft of the report which shows the study findings will be prepared by the Corps
of Engineers and submitted for review to the officials of City of Greeley, Weld County and the
Colorado Water Conservation Board. The contents, organization and format of the report shall
meet Corps, State and Federal Emergency Management Agency (FEMA) guidelines to the extent
possible. After reviews are made and comments reconciled, the final report will be prepared and
published by the Corps. The final report will include the following:
I. An introduction describing the needs for the study and authorities for conducting
the study.
II. A description of the study area including natural and beneficial values served by
the floodplain.
III. A discussion of historic flooding, including excerpts from available newspaper
articles.
IV. A narrative presenting the findings of the hydrologic and hydraulic investigations.
V. A narrative with floodplain regulation information, flood insurance information,
and recommendations for floodplain management.
VII. A technical section with the following:
A. Maps with flood outlines for the 100- and 500 -year frequency flood, on a
scale of 1 in. = 400 ft. These boundaries will be consistent with flood
profiles of item B.
B. Exhibits of flood profiles and representative cross sections for the selected
flood frequencies.
C. Tabulation of discharge -elevation -frequency -velocity data for the 10-, 50-,
100- and 500 -year floods.
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Narrative on investigations, analyses, and technical data. The size of the
reports will be 11 in. x 8.5 in. with appropriate 11 in. x 17 in. foldout
sheets for the floodplain maps and engineering drawings.
E. A working mylar map on a scale of 1 in. = 200 ft. with two foot contours
showing cross sections, stationing, and flood outlines for the 100- and 500 -
year floodplain.
F. HEC-RAS or HEC 11 Input and summary output diskettes for the final
computer runs.
COORDINATION AND RESPONSIBILITIES
The Colorado Water Conservation Board is primarily responsible for coordination of the study
and providing information to other state, regional, and federal agencies including the Mitigation
Division, Federal Emergency Management Agency, the U.S. Army Corps of Engineers, and
Architectural & Engineering firms.
The Weld County and the City of Greeley are responsible for obtaining permission and assisting
with carrying our field surveys with assistance from the Colorado Water Conservation Board,
providing public information coverage, and using the study findings in its local floodplain
management program. The Colorado Water Conservation Board, City of Greeley and Weld
County representatives are responsible for the distribution and interpretation of the floodplain
management study reports and providing continuing information and educational services
following completion of the studies.
The City of Greeley under contract to a consultant has prepared a floodplain information study
for Reach II which findings shall incorporated into this project.
The Corps is responsible for conducting the technical studies and preparing the floodplain
information report which can be published in house using xerox methods. The Corps will assist
the Colorado Water Conservation Board, City of Greeley, and Weld County in distributing the
final reports and in the interpretations of flood hazard data needed in the preparation and
implementation of a floodplain management practices.
SCHEDULING
Scheduling of the major study activities will be presented to the sponsors by the Corps. There
are several elements involved in each activity and work will be done concurrently between
activities. It is expected that the duration of the study will not exceed 12 months, and that the
final report should be completed by December, 1997.
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FUNDING
Total estimated cost for the study is $130,000. The cost will be shared by the local sponsors and
the Corps of Engineers. The estimated cost share for the local sponsors is $91,000. It is
understood that these funds will be contributed to the project through a mapping and survey work
under contract to private contractors and services provided (in-house) by the City of Greeley.
The Corps of Engineer's share of the study cost is $39,000 which will be performed in-house in
the form of engineering services. Funding is provided under the Floodplain Management
Assistance Program through the Corps regular agency appropriations.
Costs estimates based on the noted principal work items are as follows:
Work Items
Field Surveys and Mapping
Assess Floodplain Values
Technical Studies and
Report Preparation
Other Personnel Services:
(Administration, Public information,
Ingress & Egress Rights, Historic
Flooding Data, and Future Development
Data)
Travel
Local
Sponsors
64,000
0
24,000
3,000 (1)
Corps
0
1,000
33,000
3,000
0 2,000
Total Cost
(1)
91,000 39,000
In -kind (non -cash) resources provided by the appropriated County planning Offices and
Municipal Departments.
PRINCIPAL WORK ITEMS
Collectively the Colorado Water Conservation Board, City of Greeley, and Weld County will:
1. Provide all needed base maps and cross sections. The maps will be in accordance
with state and national mapping standards.
2. Secure all necessary rights of ingress and egress for engineering field surveys and
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floodplain management studies.
3. The City will prepare the final 100- year floodplain maps at a scale 1 "=400' using
the delineation as drafted by the Corps and after approval by the sponsors.
4. Disseminate study information to the public and provide facilities for public meetings.
In addition to the above, the Colorado Water Conservation Board will coordinate all of the study
activities between the sponsoring organizations.
The Corps of Engineers will:
1. Conduct engineers field reviews for hydrologic and hydraulic analyses.
2. Assess the existing natural and beneficial floodplain values.
3. Evaluate the existing floodplain and assign "n" values for each channel. The "n"
values will be concurred with by the Colorado Water Conservation Board before
other technical studies are started.
4. Conduct flood hazard technical studies. Hydrologic and hydraulic data will be
developed for flood profiles and state -discharge tables. Floodplains for the present
condition 100- and 500 -year frequency floods will be outlined on the base maps.
5. Water surface profiles for the hydraulic analysis will be computed using the U.S.
Army Corps of Engineers HEC-RAS or HEC II computer program.
6. Present the final drafted 100- year floodplain information on 1"=200' mapping for
publishing by the sponsors.
7. Prepare and distribute review drafts of the report.
8. Prepare and print copies of the final report.
9. Participate in interpretation and public information activities.
STUDY FOLLOW-UP
The Corps of Engineers, in cooperation with the Colorado Water Conservation Board, will
provide follow-up assistance to City of Greeley and Weld County as the last phase of the study.
Follow-up assistance includes interpretation of study findings and the incorporation of the
technical data into community floodplain management programs. The Corps of Engineers follow-
up will be primarily as technical advisor and will not include land surveys, legal interpretations,
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nor enforcement of regulations. The scheduling of assistance to interpret the study findings will
be coordinated through the Colorado Water Conservation Board. Assistance is expected to be
completed in FY 98 following the distribution of the final report.
COST ESTIMATES FOR PRINCIPAL WORK ITEMS BY
SURVEYS AND MAPPING
FY -95 FY -96 FY -97
City of Greeley
- Aerial Photography $ 3,375
- Photo positives 1,875
- Develop planimetric files 31,500
- (City Areas)
- Develop vertical/horizontal
files 7,000
Photo positives(additional) 750
Vertical/Horizontal files, 1,500
(additional)
Additional Personnel
Svcs. (in -kind) 1,000
Sub total $47,000
Weld County
- Develop Vertical and Horizontal $14,000
(county areas)
- Cross sectional set-ups 2,000
- Additional personnel Svcs, 1,000
(in -kind)
Sub total 17,000
Colorado Water Conservation Board
- Additional Vertical/Horizontal Control 1,000
- Additional set-up 1,000
- Additional Personnel Svcs (In -Kind) 1,000
Sub total 3,000
TECHNICAL ENGINEERING SERVICES
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• City of Greeley by consultant $24,000
• Corps of Engineers
- Technical Studies
- Travel
Sub total
$37,000
2,000
$24,000 39,000
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Title.tdo att
It is mutually agreed that this Plan of Work will be in effect only to the extent that appropriated
funds are available to all of the parties.
COLO t_: DO WATER CONS RVATION BOARD
Date 70/7-t/FLi
WELD COUNTY 9
By Vi- .€ / "�� xrp
Chair, Weld County
Title Board of Commissioners
Date 02/19/97
CITY OF GREELEY
By
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OFFICE OF THE CITY MANAGER
April 23, 1996
WELD COUNTY COMMISSIONERS
915 TENTH AVENUE
GREELEY COLORADO 80631
1000 10TH STREET, GREELEY, COLORADO 80631 (303) 350-9770\
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SUBJECT: CACHE LA POUDRE RIVER - NEW FLOODPLAIN INFORMATION STUDY
BACKGROUND
The possibility of a new Floodplain Information Study on the Cache
LaPoudre River from its confluence with the South Platte River
upstream to the Larimer/Weld county line near Windsor has been
discussed by the City of Greeley Public Works Department, the Weld
County Public Works Department, the Colorado Water Conservation
Board, and the Corps of Engineers since the fall of 1995.
The proposed new Floodplain Information Study is a much needed
revision of the existing floodplain maps which are currently being
used for the administration of floodplain related issues near the
river. The existing maps being used for floodplain administration
are entitled "Floodplain Information Report, Cache LaPoudre River,
Colorado, Volume II, Greeley, Weld County, Colorado, dated October
1975". The existing study was based on surveys and mapping from
1968 data. This ground data is outdated and does not reflect the
current ground conditions. The hydrology for the existing study is
based on 1970 data and does not account for the information and
data from the 1983 and 1995 flood events.
A new hydrologic study was completed for the Cache LaPoudre River
in 1988. This study was completed by the Army Corps of Engineers
and has been adopted by the State of Colorado and affected
communities. This 1988 study shows significantly different flood
flows than the previous flood study.
UPDATED INFORMATION
In addition to providing new floodplain information for floodplain
administration purposes, the proposed new topographic mapping and
floodplain information will be extremely valuable for the unified
effort to preserve open space along the Cache LaPoudre and plan,
design, and construct the Poudre Trail system.
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Weld County Commissioners
April 23, 1996
Page Three
Weld County is being requested to contribute funds for the
following:
* Develop vert. & horz. files (post -April 1995) $14,000
* Cross sectional data (110 sections) 2.000
Subtotal $16,000
REOUEST
The City of Greeley, the Colorado Water Conservation Board, and the
Corps of Engineers are requesting Weld County's participation in
this worthwhile project in the amount of $16,000.
PAUL GRATTET
City Manager
clw
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�\ it
TO: Weld County Board of County Gommissigners..
f 1 FROM: Bruce T. Barker, Weld County Attorney
DATE: February 11, 1997
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RE: Cache La Poudre River Flood Plain Information Study
COLORADO
On May 6, 1996, the Board of County Commissioners had a work session to discuss Weld
County's financial participation in the Cache La Poudre River Flood Plain Information Study.
Participants in this study include the Colorado Water Conservation Board, U.S. Army Corp of
Engineers, the City of Greeley, and Weld County. The question at the work session was whether
Weld County would pay for some of the costs associated with the study. Specifically, those
costs would include $16,000 for engineering of maps within the unincorporated areas along the
study route (the confluence area of the Cache La Poudre and the South Platte Rivers west to
Colorado State Highway 257). There would also be an "in -kind" donation of Public Works staff
time of about $1,000. Although there had been some reluctance to do so earlier, the Board of
County Commissioners agreed to pay the $16,000 in cash and $1,000 in -kind costs.
Drew Scheltinga, Weld County Engineer, asked the Colorado Water Conservation Board to
prepare an agreement for the various entities to better understand what there relative payment of
costs would be. All of the mapping work has already been completed by the City of Greeley and
now Weld County needs to pay its portion of the bill ($16,000). The approximately $1,000
worth of time has already been spent by Weld County toward the project.
Drew and I recommend that the Board approve the Flood Plain Information Study Plan of Work
and authorize the Chair's signature, which will then authorize the payment of the $16,000 to the
City of Greeley.
BTB/db:Memo/BOCC/Floodpl
OCC/Floodpl
pc:
Don Warden
Drew Scheltinga
7
Br . Barker
Weld County Attorney
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