HomeMy WebLinkAboutDrainage Reports - 07/26/2016NORTHERN
ENGINEER I NG
Drainage Memo
Date: July 22 , 2016
Project: 231 N. Loomis Ave .
Fort Collins, CO
Attn: Stormwater Staff
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
Stormwater Staff:
Project No. 1061-001
This letter serves to document the proposed drainage impacts of a new home proposed at 231
North Loomis Avenue in Fort Collins, Colorado.
Project Overview
The property was composed of an existing single-family residence, garage , associated sidewalk and
a parking area. The project will include the demolition of the existing house and associated
sidewalks . The garage in proposed to remain as constructed. A single-family home is proposed to
be constructed in approximately the same location with a proposed sidewalk connecting to Loomis
and another proposed sidewalk connecting to the garage .
Existing Site
The existing project site is bordered by Loomis Avenue to the east , a public alley to the west , and
single-family residences to the north and south. The existing site functioned as an 'A ' Lot, with
drainage from the western lot line draining across the site and discharging into Loomis Avenue.
Existing grades within the lot range from 1 %-4%, with a steep section along the street frontage . In
addition to the existing house and garage, the lot consists of a gravel parking area and two concrete
walks. The remainder of the site was landscape prior to the demolition of the existing house.
The total existing imperv ious area for the lot is 2 ,720 sf .
Proposed Site
The proposed site will continue to function as an 'A' Lot, with drainage from the new residence
being directed to the side lot lines via proposed swales, and then to the front of the lot via existing
"swales" along the lot line. Existing grades outside of our improvements will remain unchanged ,
including the area along the west side of the property where no improvements are proposed . No
modifications to the ex isting garage are proposed. In add ition to the new single-family home , a
sidewalk to the street and garage are being proposed .
301 N. Howes Street, Suite 100, Fort Collins, CO 80521 I 970.221.4158 www. northernengi neeri ng.com
The total proposed impervious area for the lot is 3,263 sf. This is an increase of 543 sf. The
increase in runoff as a result of this will be negligible, and no adverse impacts to adjacent properties
is anticipated.
Detention
Since the impervious area increases less than 1000 sf, no detention is required for the site.
Water Quality
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,
Cody Snowdon
Project Engineer
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
____ ,.._ __
EXISTING
EXISTING ALLEY
.. ... '
EX.CINDER
BLOCK
GARAGE
I
I
__ J_ ____ _
NORTH LOOMIS AVENUE
NORTHERN
ENGINEERING
PHONE, 970.221.4158
www .northernengineering.can
ROOFTOP
CONCRETE
ASPHALT
GRAVEL
LANDSCAPE
TOTALS
SURFACE
AREA(SF)
2,081
529
0
276
6,790
9,676
% IMPERV. IMPERV.
AREA(SF)
100% 2,081
100% 529
100% 0
40% 110
0% 0
TOTAL= 2,720
231 NORTH LOOMIS STREET
FO RT COLLINS
COLORADO
I
:H
----P.-1---
..
PROPOSED
EXISTING ALLEY
EX.CINDER
BLOCK
GARAGE
I
I __ J_ ____ _
NORTH LOOMIS AVENUE
SURFACE %IMPERV. IMPERV.
AREA(SF) AREA(SF)
ROOFTOP 2,325 100% 2,325
CONCRETE 538 100% 538
ASPHALT 400 100% 400
GRAVEL 0 40% 0
LANDSCAPE 6 ,413 0% 0
TOTALS 9,676 TOTAL= 3 ,263
DESCRIPTION
EXISTING VS. PROPOSED
IMPERVIOUS AREA
SCAI.E
1": 30'
DRAWING DRAWN BY
F. wegert
t..o, ... TE...-----t..,,,.--oJ""'Ec"""r --S K-C 1
JUNE 14, 2016 1061-002