HomeMy WebLinkAboutGrading Plans - 12/12/2017INORTHERN
ENGINEERING
Drainage Memo — 128 North Bryan Avenue
Date: December 4, 2017
Project: 128 North Bryan Avenue
Fort Collins, CO
Attn: Stormwater Staff
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
Stormwater Staff:
Lot 11, Blk 2, Babbitt
B1706642
Permit released 12/12/2017 DM
Project No. 110-071
This letter serves to document the proposed drainage impacts of a home addition proposed at 128
North Bryan Avenue in Fort Collins, Colorado.
Proiect Overview
The project proposes to construct an addition to an existing 1-story home with detached garage
located on the property.
Existin� Site
The existing site functions as a"B" Lot, with drainage from the lot draining from the home out to
the side lot lines, which then convey the drainage to both the front and back of the lot. Existing
grades in the front yard range between 0.4%-2%, and grades in the back of the home vary between
0.5% and 3%. In addition to the existing home, the existing lot consists of detached garage,
detached shed, concrete patio, concrete walkway around the southside of the home, gravel
landscaping bed surrounding two mature trees, and a gravel driveway. The remainder of the site is
Kentucky Bluegrass lawn, with small landscaping beds and mature trees.
The total existing impervious area for the lot is 3,812 sf.
Proposed Site
The proposed site will continue to function as a`B' Lot, with drainage from the new residence being
directed to the side lot lines, and then to both the front and back of the lot via existing "swales"
along the lot line. Existing grades outside of our improvements will remain unchanged, including
along the front of the property where no improvements are proposed. The proposed addition is
behind the existing home in the area currently occupied by the concrete patio, detached garage, and
rear lawn. The detached shed will be replaced with a larger out-building.
The total proposed impervious area for the lot is 4,680 sf. This is an increase of 868 sf. The
increase in runoff as a result of these improvements will be negligible, and no adverse impacts to
adjacent properties are anticipated.
FORT COLLINS:301 North Howes Street, Suite 100, 80521 � 970.221.4158
GREELEY: 820 8�h Street, 80631 � 970.395.9880 � WEB: www.northernengineering.com
INORTHERN
ENGINEERING
Detention
Since the impervious area increases less than 1000 sf, no detention is required for the site.
Water Qualitv
Water Quality for the site is being provided by releasing concentrated flows from the roof into
landscaped areas that allow stormwater runoff to infiltrate surrounding soils. Stormwater that is
unable to infiltrate is slowly passed through vegetated areas, further removing stormwater
contaminates before stormwater leaves the property.
An exhibit has been provided to illustrate the existing and proposed impervious areas. Please feel
free to contact us if you have any questions.
Sincerely,
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�SS��NAL ��G\
Frederick S. Wegert, PE
Project Engineer
FORT COLLINS:301 North Howes Street, Suite 100, 80521 � 970.221.4158
GREELEY: 820 8`h Street, 80631 � 970.395.9880 � WEB: www.northernengineering.com
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