HomeMy WebLinkAboutDrainage Reports - 04/22/1992$TEWARr&AssOCIATE$
Consulting Engineers and Surveyors
March 30, 1992 Fora! ApproVed Report
DatefAwa
Mr. Glen Schlueter
Storm Drainage Utility
City of Fort Collins
P.O. Box 580
Fort Collins, Colorado 80522
Dear Glen:
This is regarding the storm drainage for the proposed Seven Lakes M.O.B.
which will be located on the Southwest Building Envelope of Seven 'Lakes P.U.D.
Phase II Subdivision. The site is at the Northeast corner of East Prospect
Road and Prospect Park Way and is in the Spring Creek Drainage Basin.
The site is a building pad that has had all the proposed adjacent
improvements completed. This proposal includes a 3526 square foot building
and twelve additional parking spaces that were not included in the original
P.U.D. The original Building Envelope of 14,500 square feet was used for
the amount of impervious surface that was contributing runoff in the P.U.D.
This proposal has 8,406 square feet of impervious surface. The original
drainage report used the runoff coefficient for the zoning classification
of I.P. — Planned Industrial — as C=0.85. Therefore, this reduction of
impervious surface of 6,094 square feet on this site does not affect or change
the original drainage calculations. The subbasins shown are also the same
as the original report.
Because of the close proximity of Spring Creek and the Cache'la Poudre
River, there was no requirement of onsite storm water detention. ,The site
drains Northerly and Easterly across the existing parking lots to'existing
curb inlets. From the existing inlets, the storm water flows in storm sewers
to the main drainage swale located along the Northerly line of the P.U.D.
There is a blanket drainage easement on all of the P.U.D. except the building
envelopes.
The site presently has a moderate ground cover that will protect against
both wind and water erosion. Only that portion of the site that is under
construction will have the ground cover removed. Because there are existing
parking areas on the East side of the site for construction personnel, the
ground cover on the Western half of the site will not be disturbed until
the contractor is ready for final grading. A building construction limit
is shown on the plan to help protect the Western half of the site: The
foundation will be the first improvement that is constructed which will also
deter wind erosion.
James H. Stewart
and Associates, Inc.
214 N. Howes Street
P.O. Box 429
Ft. Collins, CO 80522
303/482-9331
Mr. Glen Schlueter
March 30, 1992
Page 2
All of the construction traffic will leave the site through the parking
lot rather than directly onto the adjacent streets. The contractor will
be required to clean off any mud or silt that could be carried to the parking
areas. After construction is completed, all of the area not hard surfaced
will be either seeded or sodded.
The 100—year flood elevation for this site is 4900.1, and the Fort
Collins regulatory flood protection.elevation is 4901.6 feet. The proposed
finished floor elevation is 4902.5 feet which is 0.9 feet over the required
minimum heights..
The original FEMA Map Panel for this site has been revised by the Letter
of Map Revision (IA—RA—RS [102A]) effective date of October 30, 1989. A
copy of that letter is included with this report.
If you have any questions regarding the drainage on this site, please
cal1.
Sincerely,
Richard A. Rutherford, E. & L. S.
President
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Federal Emergency Management Agency
Washington, D.C. 20472
CERTIFIED MAIL
RETURN RECEIPT REQUESTED
The Honorable Bob Winokur
Mayor, City of Fort Collins
P.O. Box 580
Fort Collins, Colorado 80522-0580
Dear Mayor Winokur:
IN REPLY REFER TO:
IA—RA—RS (102A)
Community: City. of Fort
Collins, Colorado
Map Panel Number:
FBFM 080102 0004
Effective Date: OCT 3 0 1989
This is in response to a letter dated October 9, 1989, from Mr. Robert W.
Smith, Stormwater Utility Manager, City of Fort Collins, regarding the
effective Flood Insurance Study report, Flood Insurance Rate Map (FIRM), and
Flood Boundary and Floodway Map (FBFM) for the City. of Fort Collins,
Colorado. Mr. Smith requested that we continue processing his original
request, dated April 13, 1989, for a floodway revision along Spring Creek,
which would show the effects of a channelization and relocation project from
Spring Creek's confluence with the Cache La Poudre River to East Prospect
Road. Mr. Smith made this request in lieu of his September 13, 1989, request
that the physical map revision (PMR) for Spring Creek be delayed in order to
incorporate the revisions generated by the ongoing restudy of the Cache La
Poudre River.
In our August 18, 1989, letter to you, we stated that we would revise FIRM
and FBFM Panels 0004 to incorporate the Spring Creek Project. However, we
have re—evaluated this request and, in order to expedite this revision, will
process it as a Letter of Map Revision (LOMR) instead of a PMR. Also,
because this revision invo ves on y a c ange to t e efTective—floodway, with
no changes to the base (100—year) flood elevations (BFEs), we will only
revise the FBFM.
In support of his request, Mr. Smith submitted a report entitled "Spring
Creek Rechannelization, 'As —Built' Condition," dated August 1984, prepared by
Parsons & Associates, Consulting Engineers (PACE), with his April 13 letter.
With a letter dated April 5, 1989, Mr. Mark E. Casey, President, NC
Properties, Inc., Spring Creek project developer, submitted a Maintenance
Agreement between the City of Fort Collins and the Seven Lakes Business Park
Association, Inc., dated August 15,.1985, and relevant sections of the City
of Fort Collins code regarding maintenance of stormwater facilities. These
data were submitted in response to our letter to The Honorable Gerry Horak,
former Mayor, City of Fort Collins,'dated January 7, 1985.
With an August 2, 1989, transmittal, Mr. James R. Ford of PACE submitted, in
response to a telephone call on. July 26, 1989, from our Technical Evaluation
Contractor, a set of drainage report drawings entitled "Spring Creek
Channelization Project from East Prospect Street to the Cache La Poudre
River," dated October 1984.
2-
We have completed our review of the submitted data with regard to the data
used to produce the effective FBFM and have revised the FBFM to modify the
floodway boundary delineations of a flood having a 1-percent probability of
being equaled or exceeded in any given year (base flood) along Spring Creek
from its new confluence with the Cache La Poudre River to East,Prospect Road.
The modifications are shown on the enclosed annotated copies of FBFM Panel
0004, Flood Profile Panels DIP through 06P for Spring Creek, and the Floodway
Data Table for Spring Creek. This LOMR hereby revises this panel of the
effective FBFM dated July 16, 1979.
Please note that this channelization and relocation project has moved Spring
Creek's confluence with the Cache La Poudre River to a point approximately
2,300 feet upstream of its historical confluence. As a result of the
relocation, Spring Creek's channel has been shortened. Flood Profile Panels
01P through 06P and the Floodway Data Table for Spring Creek have been
revised to reflect this change in distance. Profile Panel 01P has also been
changed to reflect the new channel alignment of Spring Creek. Because the
confluence has been moved upstream, the apparent increase in BFEs resulting
from backwater from the Cache La Poudre River on the Spring Creek Flood
Profile is due only to the new location of the Spring Creek channel. Please
note that this project does not increase the BFEs.
The determination stated in this LOMR is based on data used to prepare the
effective FBFM. A detailed analysis for the Cache La Poudre River is being
prepared. When the new analysis is incorporated and the revised FIRM and
FBFM become effective, the new FIRM and FBFM will supersede this LOMR; if
appropriate, the new FIRM and FBFM will reflect the modifications made by
this LOMR.
These modifications have been made pursuant to Section 206 of the Flood
Disaster Protection Act of 1973 (P.L. 93-234) and are in accordance with the
National Flood Insurance Act of 1968, as amended (Title XIII of the Housing
and Urban Development Act of 1968, P.L. 90-448), 42 U.S.C. 4001-4128, and 44
CFR, Part 65. As required by the legislation, a community must adopt and
enforce floodplain management measures to ensure continued eligibility to
participate in the National Flood Insurance Program (NFIP). Therefore, your
community must enforce these regulations using, at a minimum, the base (100-
year) flood elevations, zone designations, and floodways in the Special Flood
Hazard Areas shown on the FIRM and FBFM for your community, including the
previously described modifications.
This response to your request is based on minimum floodplain management
criteria established under the NFIP. Your community is responsible for
approving all proposed floodplain developments, including this request, and
for ensuring that necessary permits required by Federal or State law have
been received. With knowledge of local conditions and in the interest of
safety, State and community officials may set higher standards for
construction, or may limit development in floodplain areas. If the State of
Colorado or the City of Fort Collins has adopted more restrictive or
comprehensive floodplain management criteria, these criteria take precedence
over the minimum NFIP requirements.
3
The basis of this LOMR is a channel -modification project. NFIP regulations,
as cited in Section 60.3(b)(7), require that communities assure that the
flood -carrying capacity within the 'altered or relocated portion of any
watercourse is maintained. This provision is incorporated into your
community's existing floodplain management regulations. Consequently, the
ultimate responsibility for maintenance of the channel modification rests
with your community.
The community number and suffix code listed above will be used for all flood
insurance policies and renewals issued for your community on and after the
effective date listed above.
The modifications described herein are effective as of the date of this
letter. However, a review of the modifications and any requests for changes
should be made within 30 days. Any request for reconsideration must be based
on scientific or technical data.
This LOMR will not be printed and distributed to primary map users such as
local insurance agents and mortgage lenders; therefore, the community will.
serve as a repository for these new data. We encourage you to disseminate
the information reflected by this LOMR widely throughout the community in
order that interested persons such as property owners, insurance agents, and
mortgage lenders may benefit from this information. We also encourage you to
consider preparing an article for publication in the community's local
newspaper that would describe the changes that have been made and the
assistance the community will provide in serving as a clearinghouse for these
data and interpreting NFIP maps.
If you have any questions regarding the modifications described herein,
please call the Chief, Natural and Technological Hazards Division, Federal
Emergency Management Agency, in Denver, Colorado, at (303) 235-4830, or
Mr. Alan Johnson of my staff in Washington, D.C., at (202) 646-3403.
Sincerely,
Jo n Matticks
Ch of Risk Studies Division
Fe al Insurance Administration
Enclosures
cc:MRobert W. Smith
Stormwater Utility Manager
Mr. Mark E. Casey
President, NC Properties, Inc.
Mr. James R. Ford
PACE
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