HomeMy WebLinkAboutGrading Plans - 02/23/2023Grading/Stormwater Plan Accepted
(Buitding Permit Released) HIGHLAND
Accepted by: sagenbroad _ _ . � , _ �_ �� r�.-5
Date: 02/23/2023
Memorandum
T0:
FROM:
DATE:
PROJ ECT:
HDS 106 NO
SU BJ ECT:
Fort Collins Utilities - Engineering
Barry Schram — Lamar Construction
Jason Claeys, P.E.
10/24/22
323 S. Loomis Avenue
22-1062-00
Drainage Summary
This memo has been prepared to describe the existing conditions at 323 S. Loomis Ave and the
drainage impacts of the proposed changes in impervious area. Below is a vicinity map showing
the general location of the property:
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The property is approximately 9,500 sq ft (50' wide by 190' deep, 0.22 acres) and is located in
Old Town Fort Collins and along the west side of S. Loomis Ave, north of W. Magnolia St. Single-
family residences are adjacent to the north and south and a public alley along the west. The
existing single-family residence is located toward the east side of the lot with a carport located
in the west side of the lot. The house, carport, and all existing sidewalks are proposed to be
removed and replaced with a new house and detached garage.
Highland Development Services, Inc.
6355 Fairgrounds Avenue, Suite 100 � Windsor, CO 80550 � 970.674.7550
_ �
323 S. Loomis Ave
10/24/22
Page 2 of 2
The lot is located within the City defined flood fringe/floodplain, outside of a defined floodway.
Based on an overlay of the floodplain limits, it is estimated that the base flood elevation (BFE)
adjacent to the building is approximately 5009.8 ft. (We are working with the City to confirm the
BFE.) The regulatory flood protection elevation (RFPE) is 18" above the BFE, placing the RFPE at
5011.3 ft. The proposed top of foundation elevation is 5011.56 ft, 0.26 ft above the estimated
RFPE. All building mechanical equipment and openings are above the RFPE and no basement is
proposed.
Based on a topographic site survey, it appears that a small portion of the site drains west to the
alley with the remaining site draining east to S. Loomis Ave. Overall, the existing property seems
to be relatively flat with poor drainage around the existing buildings.
The proposed improvements will redirect drainage away from the proposed building and the
adjacent properties and towards S. Loomis Ave. There will be adequate drainage away from the
proposed buildings of at least 5% for the first 5 to 10 feet away. Runoff will be conveyed mainly
by sheet flow across the site to a 12" concrete drain pan along the north side of the site directing
runoff east to S. Loomis Ave. The difference in total impervious areas between the existing and
proposed improvements is shown below:
Total Roof Walk Total
Description Area Area Area Impervious
(sqft) (sqft) (sqft) Area (sqft)
Existing 9,492 1,664 712 2,377
Proposed 9,492 3,608 470 4,078
Difference 0 1,943 -242 1,701
There is a total of 1,701 sq ft of impervious area added with the proposed improvements. The
majority of the proposed impervious area drains across lawn and landscape areas prior to being
collected in the concrete drain pan and directed to S. Loomis Ave. Majority of the improvements
are considered disconnected impervious area, reducing impact to stormwater runoff quality.
Please do not hesitate to call (970.674.7550) or email (Iclaeys@hi�hland-ds.com) if there are any
additional questions.
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