HomeMy WebLinkAboutLot Certifications - 04/19/2006 (14)ny
PV1ENGINEERS
April 17, 2006
1435 WEST 29' STREET
LOVELAND, CO 80538
(970) 461-2661
Fax (970) 461-2665
WWW. DMWCIVILEN13INEERS.COM
S RECEIVED
City of Fort Collins
Stormwater Utility APR 1 9 2006
700 Wood Street
Fort Collins, Colorado 80521
Re: Stormwater Calculations and Design Considerations for
Snyder_ Residence- roe
Lot_4, Emerson Acres r0,00 5
Fort Collins, Colorado B 06007q �,�sn►
Dear Staff:
DMW Civil Engineers is pleased to submit this drainage study for Lot 4, Emerson Acres,
for your review. This report complies with technical criteria set forth in the City of Fort
Collins' Storm Drainage Design Criteria and Construction Standards manual and the
Urban Storm Drainaoe Criteria Manual, Volume 3, by the Urban Drainage and Flood
Control District.
We acknowledge that the City of Fort Collin's review of this study is only for general
conformance with submittal requirements, current design criteria and standard engineering
principles and practices.
This study documents the results of a simple analysis of drainage and flood conditions for
the proposed Snyder residence on Lot 4, Emerson Acres Subdivision. The site is located
in the southwest quarter of Section 18, Township 6 North, Range 68 West of the 6th
Principal Meridian in the City of Fort Collins, Colorado. The site is situated on the
northeast corner of Lemay Avenue and Carpenter Street.
Site topographic mapping was taken from the Town of Fort Collins topographic mapping
with a two (2) foot contour interval. The site is platted for a private residence and is
vegetated with native grasses.
The site is within the Stanton Creek tributary of the Fossil Creek Basin of the City of Fort
Collins Master Drainage Plan. Stanton Creek flows from south to north along the
property's east boundary. A tributary of Stanton Creek flows from west to east along the
property's north boundary. The floodplain for Stanton Creek was updated in October,
2003, with the City's current rainfall criteria. This floodplain exceeds the limits delineated
on the subdivision plat for Emerson Acres. The floodplain for the aforementioned tributary
was not updated at that time. There are no known previous drainage studies or project
master plans which influence the site other than the City of Fort Collins Master Drainage
Plan and a study done for Lot 3, Emerson Acres Subdivision by Parsons and Associates
in January of 1998.
Y
Data from the EPA-SWMM analysis for the Fossil Creek Master Drainage Study was used
to estimate peak stormwater runoff in Stanton Creek and the aforementioned tributary
adjacent to the site. A major 100-year design storm has been used to evaluate the
floodplain.
The computer program °Flowmaster" has been used to analyze the channel sections for
the tributary along the property's northern boundary. A simple Manning's based flow
calculator was used to determine flow depth and top width of the 100-year flood. Sections
from the previous study were used and evaluated and, for stations 0+00 through 1+50,
they were determined to be representative of the existing channel. For stations 2+00
through 3+00, new sections were determined from the topogrophy based upon channel
improvements that have been made since the previous study. All sections and their
analyses are contained in the appendix of this report.
There is no on -site detention for this development. First, due to the site's close proximity
to Stanton Creek, the on -site peak flow will greatly precede the peak in either the Stanton
Creek channel or the tributary channel. Second, the development of the site will have little
effect on the imperviousness of the overall basin. The proposed house is 9,924 square
feet, and the lot is 162,959 square feet.
Temporary sediment / erosion control consisting of silt fencing and slope protection will
surround areas of the proposed construction and seeding / mulching will be utilized on
disturbed areas. Stormwater quality for the site will be provided by minimizing directly
connected impervious areas. Roof stormwater collection directs flow to landscaped areas
to provide longer travel time so as to encourage the removal of suspended solids before
runoff leaves the site.
The proposed development is consistent with the City of Fort Collins Master Drainage
Plan. Because of the low density of the proposed development, the existing drainage
characteristics of the site have been maintained as much as possible.
If you should have any questions or comments as you review this report, please feel free
to contact me at your convenience.
Sincerely,
DMW CIVIL ENGINEERS, INC.
STORMWATER
nP�O REO�� , „ RECEIVED
- `la APR 1 9 2006
33885 1
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Jade P. Miller, P.E. (CO #33885)
Project Engineer
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LIMITS OF 100---YEAR
LOT 3
FLOODPLAIN FOR
TRIBUTARY PER ATTACHE6,,
g942
ANALYSIS USING
\
CURRENT DATA AVAILABLE
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(Q100 = 464 CFS).
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LIMITS OF 100-YEAR FLOODPLAIN
F PER CITY FLOOD RISK MAP -
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FOR STANTON CREEK
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NOTES:
1. THERE WILL BE NO FILL MATERIAL PLACED WITHIN THE
FLOODWAY/FLOODPLAIN OR EROSION BUFFER ZONE.
2. THERE WILL BE NO IRRIGATED VEGETATION WITHIN THE EROSION
BUFFER ZONE. ALL REGULATIONS REGARDING EROSION BUFFER ZONES
ARE TO BE COMPLIED WITH.
3. FOR TEMPORARY CONSTRUCTION OF UTILITY SERVICES ACROSS THE
FLOODWAY/FLOODPLAIN OR EROSION BUFFER ZONE, A FLOODPLAIN USE
PERMIT IS REQUIRED. CONSTRUCTION SHALL BE CARRIED OUT SO AS TO
MINIMIZE ANY DISTURBANCE TO THE CHANNEL BED AND BANKS
4: FLOODWAY SHALL BE STAKED PRIOR TO START OF CONSTRUCTION.
5. TOP OF FOUNDATION ELEVATION BASED UPON MINIMUM GRADING FOR
POSITIVE DRAINAGE ADJACENT TO FOUNDATION. SUBSURFACE WATER
TABLE MAY EXIST AND NECESSITATE ADJUSTMENT OF BUILDING ELEVATION.
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
1- 800- 922-1987
OR 1- 303- 232-1991 DEN ERO
CALL 2 BUSINESS DAYS IN ADVANCE
BEFORE YOU DIG, GRADE, OR EXCAVATE
FOR THE MARKING OF UNDERGROUND
MEMBER UTILITIES.
60 0 60 120 180 Feet
( IN FEET )
1 inch = 60 ft.
LEGEND:
EXISTING STORM SEWER
EXISTING STORM SEWER WITH INLET
�- PROPOSED STORM SEWER OR CULVERT
PROPOSED STORM SEWER WITH INLET
5020 EXISTING CONTOUR
20 PROPOSED CONTOUR
— FLOODPLAIN LIMITS
EROSION BUFFER LINE
BASE FLOOD ELEVATION
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