HomeMy WebLinkAboutARROWHEAD COTTAGES - MJA/FDP - FDP160004 - REPORTS - STORMWATER-RELATED DOCUMENTS301 N. Howes Street, Suite 100, Fort Collins, CO 80521 970.221.4158 www.northernengineering.com
LID Conformance Report
Date: June 3, 2016
Project: Arrowhead Cottages Project No. 374-018
Fort Collins, CO
Attn: Stormwater Staff
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
Stormwater Staff:
This letter serves to document conformance of the above referenced project with City of Fort Collins Low
Impact Development (LID) requirements. In particular, the project is meeting Section 3.1 of the Fort Collins
Stormwater Amendments to the Urban Drainage and Flood Control District Criteria Manual, including Section
3.1 (a)(1) requiring that no less than 50% of any newly added impervious area be treated using one or more
LID techniques and Section 3.1(a)(2) requiring that no less than 25% of all new paving use a permeable
pavement technology that is considered an LID technique.
Section 3.1(a)(1)
The project as a whole is proposing 0.491 acres of new on-site impervious area. This results in a minimum
required LID treatment area of 0.245 acres.
The project is treating 0.060 acres of on-site impervious area by pavers (directly or indirectly). 0.042 acres
of permeable pavers will receive 0.018 acres of adjacent impermeable runoff.
The project is treating 0.086 acres of on-site impervious areas using a Rain Garden. Roof drains will be
collected by an underground storm sewer system and direct runoff from these areas to a rain garden located
immediately west of the garage. This rain garden will be adequately sized to treat stormwater during a minor
event. During larger events, the rain garden will overtop into the existing nearby detention facility.
The project is treating 0.103 acres of on-site impervious area using a Bio-swale with Soft Bottom. The
primary source of impervious area is the south half of Building 2, which will directly drain into the Bio-swale
Low Impact Design feature. The bio-swale will have a designed section that will treat stormwater during
minor events. An underdrain will collect the treated stormwater and discharge into the Centre Avenue Right-
of-Way. Larger events will overtop directly into the adjacent Centre Avenue Right-of-Way.
The total on-site project area treated by LID techniques is 0.249 acres, which is 50.7% of the total new
impervious area.
Section 3.1(a)(2)
The project as a whole is proposing 0.163 acres of new impervious paving. This results in a minimum
required permeable paving area of 0.041 acres. The project has evaluated various areas for pavers to
provide LID treatment to multiple areas of the Site. The total area of permeable pavers provided by the
project is 0.042 acres, which is 25.8% of the total new paving.
Arrowhead Cottages
LID Report
An exhibit has been provided to illustrate the topics outlined, and calculations supporting the LID techniques.
Please feel free to contact me if you have any questions.
Sincerely,
Danny Weber, PE
Project Engineer
ATTACHMENTS:
Low Impact Development (LID) Treatment Exhibit
UD
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8" SS
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8" W 8" W
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CONTROL
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CENTRE AVENUE
WORTHINGTON
CIRCLE
STUCCO BUILDING
FFE=~5048.1
EXISTING
APARTMENT BUILDING
FFE=~5049.0
NEW MERCER DITCH
PROPOSED
BIO-SWALE
PROPOSED
BIO-SWALE
IMPERVIOUS AREA
TREATED BY BIO-SWALE BLDG 2
BLDG 1
PROPOSED
RAIN GARDEN
GARAGE
IMPERVIOUS AREA
TREATED BY RAIN GARDEN
IMPERVIOUS AREA
TREATED BY RAIN GARDEN
PROPOSED
PERMEABLE PAVERS
RUN-ON AREA FOR
PERMEABLE PAVERS
Dr
Fl i c k e
Cant er bur y
Rai nt r ee
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Mi r r o r ma r e Ci r Gi l gal ad
Wa y
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Worthington
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Centre
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Dr
Haven Dr
Suddering
Spring Creek
Heatheridge Ct
Woodcrest Ct
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Waters Edge
Winterberry
Way
d Rd
Trail
Wind
Weathertop Ln
Meadowlark
Dr
Davidson
Winchester Dr
Powderhorn Dr
Stagecoach
Ave
Snowberry
Rd
Park Ct W Stuart St
Chetwood
Dr Dr
PROJECT
LOCATION DRAKE ROAD
SHIELDS STREET
LOW IMPACT DEVELOPMENT (LID) TREATMENT EXHIBIT
LID-1
FORT COLLINS, CO
ARROWHEAD COTTAGES
E NGINEER ING
N O R T H E RN
06.03.16
D:\PROJECTS\374-018\DRAINAGE\REPORTS\LID REPORT\374-018_LID.DWG
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
EXISTING STORM SEWER
PROPOSED STORM SEWER
PERMEABLE PAVERS
RUN-ON AREA FOR
PERMEABLE PAVERS
IMPERMEABLE AREA
TREATED BY LID
( IN FEET )
0
1 INCH = 40 FEET
40 40
50% On-Site Treatment by LID Requirement
New On-Site Impervious Area 0.491 Ac.
Paver Area 0.042 Ac.
Traditional Pavement Area 0.120 Ac.
Other Impervious Surfaces (Roofs, Concrete Walks, etc.) 0.329 Ac.
Required Minimum Impervious Area to be Treated 0.245 Ac.
Paver LID Treatment
Paver area 0.042 Ac.
Run-on area for Paver 0.018 Ac.
Impervious Area Treated by LID Pavers 0.060 Ac.
Rain Garden Treatment
Impervious Area Treated by Rain Garden 0.086 Ac.
Bio Swale with Soft Bottom Treatment
Impervious Area Treated by Bio Swale 0.103 Ac.
Total On-Site Impervious Area Treated 0.249 Ac.
Percent of On-Site Impervious Area Treated 50.7 %
25% Permeable Pavement Requirement
New Pavement Area 0.163 Ac.
Required Minimum Area of Permeable Pavement 0.041 Ac.
Total Permeable Pavement Area 0.042 Ac.
Actual % of Permeable Pavement Provided 25.8 %