HomeMy WebLinkAboutARROWHEAD COTTAGES - MJA/FDP - FDP160004 - REPORTS - STORMWATER-RELATED DOCUMENTS (3)caa emdxcs s x
PWMVArM
_ / t
A
0
Ol]f.t6
(NORTHERN
ENGINEERING
IEoeNo:
vwa®maaw
—.�
EAEIYp fbllM
— —. — —
EnE�E.osrcaiawea
woea®amM Mv¢�
reertixev�veu
{BlEI6EP/.YHIE
.E'Eib1F..E.16,�
�1 IMHEf�
1 Mtll• tlRlT
50% On -Site Treatment by UD Requirement
New On -Site Impervious Area
0.495
1 Ac.
Paver Area
Traditional Pa eme r
.11
Ac.
Other Impervious Su aces Roo s, Concrete Walks, etc.
0.336
Ac.
Require Minimum Impervious Area to be Treated
0.247
Paver LID Treatment
Paver area
0.041
Ac.
Run-on area for P r
0,016
Ac.
Im ervious Area TreateJ by LID Pavers
0,058
Ac.
Rain Garden Treatment
Impervious Area Treated y Rain Garden
Q.086
Ac.
Bio Swale with So Bottom Treatment
Impervious Area Treate b 0io Swa a
0.104
Ac.
Total On -Site Im ervious Area Treated
0.247
Ac.
Percent o On.Site Impervious Area Treated
50.0
%
25% Permeable Pavement Requirement
New Pv m n r a
.15
Required Minimum Area o Permeable Pavement
1 Ac..
To al Perm all P m n r
A.
Actual %of Permeable Pavement Provided
2 .1
1 %
ARROWHEAD COTTAGES
FORT COLLINS, CO
NORTHERN
ENGINEERING
Arrowhead Cottages
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
LID Report
NORTHERN
ENGINEERING
LID Conformance Report
Date: March 25, 2016
Project: Arrowhead Cottages
Fort Collins. CO
Attn: Stormwater Staff
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
Stormwater Staff:
Project No. 374-020
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 0.495 acres of new on -site impervious area. This results in a minimum
required LID treatment area of 0.247 acres.
The project is treating 0.058 acres of on -site impervious area by pavers (directly or indirectly). 0.041 acres
of permeable pavers will receive 0.016 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 0.098 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 0.247 acres, which is 50.0% of the total new
impervious area.
Section 3.1(a)(2)
The project as a whole is proposing 0.159 acres of new impervious paving. This results in a minimum
required permeable paving area of 0.040 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 0.041 acres, which is 26.1% of the total new paving.
301 N. Howes Street, Suite 100, Fort Collins, CO 80521 1 970.221.4158 I www.northernengineering.com