HomeMy WebLinkAboutDrainage Reports - 01/24/2016❑QUALITY
`X ENGINEERING
WWW.QUALITY-ENGINEERING.COM
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January 25, 2016 -2, ( �'; 0$ 245,1 'l3 i S O'E 2.l
Mr. Shane Boyle & Mr. Dan Mogen
City of Fort Collins Engineering Department
281 N College Avenue
Fort Collins, Colorado 80524
RE: Drainage Memo,— 625 Smith Street
625 Smith Street, Fort Collins (Larimer County), Colorado 80525
QE Project No. 6278-01
Mr. Boyle & Mr. Mogen:
The purpose of this letter is to address drainage impacts to the existing 0.22-acre property located at 625
Smith Street due to the proposed building and garage. The site is situated in Lot 6, Block 166, City of
Fort Collins, County of Larimer, State of Colorado. Specifically, the property is located midway
between East Myrtle Street nd Laurel Street and bound by Smith Street to the east an a common alley
access -way to the west. Thi subject property is surrounded by residential properties t6 the north, south,
across the alley to west, as well as across Smith Street to the east. (See Vicinity Map)
The existing property currently consists of a house, shed, and mature landscaping. The existing site has a
local high -point splitting lot flows to the east and west. Approximately 3/4 of the existing site drains to
the east, toward Smith Street. The remaining drainage, located west of the local high -point, flows west
to the common alley, historically. The existing structures and site features shall be completely
demolished for the proposed house and garage construction.
The proposed improvements include a single family home with basement comprising of approximately
1,900 sf footprint, along with porch and deck areas. A +/- 600 sf garage with attached car -port is also
proposed to sit at the west end of the lot, adjacent to the common alley. The site percent impervious
went from 6.0% (existing) to 45.4% (proposed). Drainage swales are proposed along the north and south
edges of the property to help mitigate developed runoff and keep consistency with historical flow
patterns. No on -site detention is proposed for this development. Water quality shall be achieved
through said proposed drainage swales with natural flowlines.
The developed flows from the east basin shall sheet flow into proposed drainage swale flowlines where
runoff will continue to be conveyed east. The proposed drainage swales along the north and south
property lines shall extend from the Smith Street ROW west all the way to the existing alley. Developed
flows from the north side of the property shall sheet flow into the northern swale and be discharged at
the east end of the property, as they do historically. Developed flows from the south side of the property
QUALITY ENGINEERING, LLC (970) 416-7891 2637 MIDPOINT DRIVE, SUITE E FORT COLLINS, COLORADO
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shall sheet flow into the southern swale and be discharged at the east end of the property, as they do
historically.
Drainage calculations are provided for this project due to the increase of impervious area on the exiting
subject lot and to verify that increased flows will not adversely impact adjacent properties.
The City of Fort Collins Stormwater manual amending the Urban Storm Drainage and Flood Control
District (USDFCD) has been used for drainage design guidance.
Please see the attached hydrologic basin parameters, 2-year and 100-year existing & developed flow rates.
In summary, the grading and drainage design for the proposed home and garage at 625 Smith Street
complies with the requirements of Urban Storm Drainage and Flood Control District as well as the City
of Fort Collins' Storm Drainage Criteria. The proposed changes have nearly negligible effects on the
historic drainage system of the lot. Please see the attached grading plan and drainage plan. If you have
any questions or require additional information, please call at (970) 416-7891.
Sincerely,
QUALITY ENGINEERING, LLC
A,L WOE
Mark Morrison, EI
Project Manager
Attachments —
Reviewed by,
Cody Geisendorfer, PE, CEM
Principal 1 ngineer
Appendix A
-Vicinity Map
-Existing and Proposed composite `C' values
-Existing and Proposed flows (cfs)
-Grading/Drainage Plan
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SECTION A -A
NTS
EXISTING GROUND
PROPOSED GA RAGE
SECTION B-B
NTS
�1"
) L
)PERTY UNE (TYP)
SECTION C-C
NTS
TOF"4664.32'
POSED HOUSE
W
DRAINAGE LEGEND
8
BASIN NAME
BS PERCENT
IMPERVIOUS
AREA IMP
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AREA (ACRES)
D1
DESIGN POINT
BASIN BOUNDARY
PROPOSED FLOW
DIRECTION
A A
DRAINAGE SECTION
BASIN
AREA(ACRES)
COMPOSITEC
%IMPERVIOUS
lODYR FLOW(CFS)
81
0.04
LOD
96.7
0139
2028
O56
34
L00
E2
003
0.19
0
004
E2
0.19
0.26
6.9
0.32
NOTE: DROP BOTTOM OF FOUNDATION (2'-4" MAX)
TO MAINTAIN FROST DEPTH AT FG SHOWN
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ElU6TING GROIlO PROPOSED GROUND ���
R
PEMR RAN
CHECKED BY:
GG
DESIGNED W:
MHM
DRAWN W.
MHM
20'
GM' JANUAR(.
2016
SG E :
110
SCALE: 1" = 10'
PROJECT NO.: 5276-001
C1.0