HomeMy WebLinkAboutDrainage Reports - 01/19/2010NORTHERN
N. = ENGINEERING
ADDRESS: PHONE:970.221.4158 WEBSITE:
200 S. College Ave. Suite 100 www.riorthernertonee6ng.com
Fort Collins, CO 80524 FAX: 970.221.4159
Drainage Letter Report
Date: August 19, 2009
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Project: 317 Wood Street
Lot 5 & Lot 6, Block 303, Capitol Hill Addition
Fort Collins, Colorado
Attn: Mr. Wes Lamarque
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
Dear Wes:
Project No. 110-043
This letter serves to address the stormwater impacts of the above referenced single-family
residential home project. Lot 5 currently contains a lone residential dwelling structure as well as
a detached garage accessed from the alley. Lot 6 currently contains two sheds and minor
concrete flatwork. The proposed redevelopment will create two (2) free-standing single-family
residential homes fronting Wood Street with detached garages accessed from the rear alley; one
each on Lot 5 and the other on Lot 6. (See attached Grading Plan for further details)
Table 1 below summarizes the pre- and post -construction impervious areas. Detention is not
required since the total increased impervious area is less than 5,000SF.
Table 1 - Impervious Areas
LOT 5
LOT 6
Surface
Existing
Proposed
Change
Existing
Proposed
Change
Rooftop
house
1,105 SF
1,524 SF
419 SF
0 SF
1,411 SF
1,411 SF
garage/shed
536 SF
704 SF
168 SF
316 SF
812 SF
496 SF
Porch/Patio
505 SF
269 SF
-236 SF
0 SF
256 SF
256 SF
Conc. Walk
612 SF
76 SF
-536 SF
127 SF
75 SF
-52 SF
Conc. Driveway
387 SF
480 SF
93 SFJ
0 SF
508 SF
508 SF
Totalsi
3,145 SF
3,053 SF
-92 SFJ
443 SF
3,062 sF
2,619 sF
TOTAL INCREASED IMPERVIOUS AREA (LOTS 5 & 6) = 2,527 SF
Although stormwater quantity detention is not required, stormwater quality mitigation will be
addressed by both temporary and permanent Best Management Practices (BMPs). During
construction, the Builder will follow the appropriate and applicable City of Fort Collins standards
for erosion and sediment control. Post construction water quality and erosion control will be
achieved by a fully established and stabilized site. All areas disturbed during construction will
receive permanent hardscape, landscape, or building structure.
Page 1 of 2
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NE I NORTHERN
ENGINEERING
Another element addressing the quality of stormwater runoff is the minimization of directly
connected impervious areas. A large vegetated buffer strip exists within the public tree lawn;
measuring approximately 17-ft along Wood Street. Additionally, roof drainage will be collected
in residential gutter and downspout systems, and discharged on the landscaped surface. This
will encourage infiltration, pollutant settling, and cleansing of runoff before it reaches the
receiving waters in the adjacent curb and gutter.
The grading plan closely matches existing elevations and drainage patterns, thus ensuring
adjacent properties are not adversely impacted. Detention is proven to be unnecessary.
Stormwater quality has been considered, and will be addressed in a sufficient manner.
Therefore, it is my professional opinion that the two single-family homes proposed at 317 Wood
Street (Lot 5 and Lot 6, Block 303, Capitol Hill Addition) satisfy applicable stormwater criteria.
Please do not hesitate to contact me if you have questions or require additional information.
Since -'
Nicholas W. Haws, PE, LEED AP
Project Manager
CC: Aaron Everitt - Jamestown Builders
Page 2 of 2
GRADING PLAN
FOR
LEGAL DESCRIPTION: LOT 5 & LOT 6, BLOCK 303, CAPITOL HILL ADDITION,
FORT COLLINS, COLORADO
FG=19.89 I FG=19.13 (
I /
/ LOT 6 ^/ /
/
20 0 20 Feet
( IN FEET )
1 inch = 20 ft.
EVERITT COMPANIES
CAPITOL HILL ADDITION
No.
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By
DATE
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ENGINEERING
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PROJECT Y: 110-043 BG: M DR M BY: AGR DATE: 811009