HomeMy WebLinkAboutGrading Plans - 05/06/2016Lot 1& E 36 ft of Lot 2, Blk 4, Scott Sherwood Add
B1602175
Accepted & permit released 5/6/2016 DM
� I NORTH ERN
ENGINEERING
Drainage Memo
Date: May 5, 2016
Project: 1401 West Mountain Avenue
Fort Collins, CO
Attn: Dan Mogen
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
Stormwater Staff:
Project No. 850-013
This letter serves to document the proposed drainage impacts of a new home proposed at 1401
West Mountain Avenue in Fort Collins, Colorado.
Proiect Overview
The project proposes to completely remove an the existing 1-story building that previously housed
the Oakwood School located on the property and construct a new home as well as a carriage house
that will be accessed from the alley on the south side of the property.
Existing Site
The existing site was primarily a flat lot, with drainage from the lot draining from the building out to
the West Mountain Avenue in the north, South McKinley Avenue in the east, and the alley in the
south. Existing grades in the front yard range between 0.5%-2%, existing grades on the eastern
yard range from 1.5%- 2.5%, and existing grades in the rear of the building vary between 0.5%-
1%. In addition to the existing building, the lot consists of an existing asphalt driveway on the
western side of the building, three concrete walkways and a large asphalt parking lot on the south
side of the building connected to the alley. 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 10,792 sf.
Proposed Site
The proposed site remains relatively flat, but features improved drainage away from the structure.
Drainage from the south yard, as well as the western and southern portions of roof runoff of the new
residence is being directed via "swale" through the south yard to a new concrete sidewalk chase to
South McKinley Avenue. Grades along the north and east of the house have been increased from
existing and drain to West Mountain Avenue and South McKinley Avenue. Existing grades outside of
our improvements will remain unchanged. A new carriage house is proposed at the alley that will
have a small concrete apron at the entrance and drain to the alley in the south.
301 N. Howes Street, Suite 100, Fort Collins, CO 80521 � 970.221.4158 � www.northernengineering.com
The total proposed impervious area for the lot is 8208 sf. This is a decrease of 2584 sf. No
adverse impacts to adjacent properties is anticipated.
Detention
Since there is no increase of impervious area, 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 surround 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,
. �
�r
Benjamin Ruch
Project Engineer
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Senior Engineer
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