HomeMy WebLinkAboutDrainage Reports - 02/18/2014nr�
NORTHERN
ENGINEERING
Drainage Letter Report
Date: January 27, 2014
ADDRESS: PHONE:970.221.4158 WEBSITE:
200 S. College Ave. Suite 10 www.northernengineering.com
Fort Collins, CO80524 FAX: 970.221.4159
Project: Miramont Health Office Building
Fort Collins, Colorado
Attn: Mr. Wes Lamarque
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
Dear Wes:
Project No. 895-002
City of Pt. CollinstyrovlWPlans
Approved By
Date
This letter serves to address the stormwater impacts of the above referenced project. The site currently
consists of rooftop, concrete walks and patio, asphalt parking areas, some turf, trees, and other vegetation.
The southeastern portion of the site presently drains to an area inlet located in the center of the east main
drive aisle. The northwestern portion of the site presently drains to the center of the northern main drive
aisle and travels off -site to an inlet within the neighboring property. This area inlet releases into the City's
storm sewer system within West Drake Road and Redwing Road. Historic drainage patterns will generally
be preserved. The total impervious area within the property boundary of the existing site is approximately
36,158 square -feet.
The proposed redevelopment will refurbish the existing parking lot and drive aisle. The existing building is
proposed to stay, but go through a complete remodel and a small addition in the rear of the building.
Concrete pedestrian connections will be added to both West Drake Road and Redwing Road. The total
impervious area within the property boundary of the proposed redevelopment is roughly 34,038 square -
feet.
To enhance the site and provide some water quality, a section of parking area is proposed to be permeable
pavers. This section will achieve water quality to half of the parking stalls within the southern parking
area. The paver section is 224 square feet in size and will provide water quality for 504 square feet of
parking area, avoiding the pavers to get overloaded and being a maintenance issue in the future. The
pavers will include and underdrain and discharge directly into, the existing storm sewer system.
The total impervious area proposed with this project will be decreased by approximately 2,120 square -feet
(36,158 - 34,038). A detailed breakdown of the existing and proposed impervious areas is attached to
this letter. Since the proposed redevelopment actually results in a lower impervious area than the historic
condition, on -site detention is not required. To incorporate some water quality within the site, a rain
garden is being proposed within the ne median.
Please do not hesitate to contact me if you have questions or require additional information.
Sincerely,
qai(A4��
Bud Curtiss
Project Manager
ody N. Snowdon
Project Engineer
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(NORTHERN
ENGINEERING
Miramont Health Office Building
COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
CHARACTER OF SURFACE:
Streets, Parking Lots, Roofs, Alleys, and Drives:
Asphalt .................................................................................................
Corlorete...............................................................................................
Gravel..................................................................................................
Roofs..................................................................................................
Pavers..................................................................................................
Lawns and Landscaping
Sandy Soil............................................................................................
Clayey Soil............................................................................................
Runoff
Coefficient
Percentage
Impervious
Project Miramont Health Office Building
Calculations By: C. Snowdon
Date: January 27, 2014
"Soil Classification of site is Sandy Loam"
2-year q - 1.00 io-year t, - 1.00 100-year cr - 1.25
0.95
100%
0.95
90%
0.50
40%
0.95
90%
0.40
22%
0.15
0%
0.25
0%
R"If Coetficienb are taken fmn Ne city of fan Wim Stalin
Draiaage Desk
n Create and CUmVutlion
5lamards, table
3-3, % Impavious taken fro, UDFCD USDCM. Volume I.
Basin ID
Bann ��
(s.f.)
Basin ��
(ac)
Area of
Asphalt
(ce)
Area of
Concrete
(ac)
Area of
Roofs
Lac)
Area of
Pavers
(ac)
Area of
Lawrre and
Landscaping
Lac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Impervious
Area
(sq h)
Composite
% limperv.
Exisli1
44,311
1.02
0.56
0.12
0.15
0.00
0.19
0.80
0.80
1.00
N 15B
79%
Pro etl
44.371
1.02
0.46
0.17
0.16
0.01
0.23
0.76
0.76
6.96
34.213
74%
Page 1 of 1 D:IRojaUs1a95-00210me aWydmbgyl995-0 2knoa us CaksdulGVafws
Miramont Health
Office Building
Erosion Control Cost Estimate
Project Number: 895-002
Location:
Fort Collins, CO
Date: January 24, 2014
Total Acres:
0.88
Estimated
Unit
Total
EROSION CONTROL MEASURE
Units
Quantity
Price
Price
Inlet Protection
each
1
$100.00
$100.00
Silt Fencing
L.F.
331
$1.50
$496.50
Dandy Sack
each
5
$150.00
$750.00
Rock Socks
each
2
$125.00
$250.00
Vehicle Tracking Control Pads
each
1
$300.00
$300.00
Concrete Washout Area
each
1
$200.00
$200.00
Vegetate Landscaped Areas
acre
0.23
$1,000.00
$226.88
TOTAL =
$2, 323.38
AMOUNT OF SECURITY = 1.5
x
$2,323.38
= TOTAL =
$3,485.07
-OR-
COST TO VEGETATE: TOTAL ACRES
x ($1000/acre) x 1.5
= TOTAL =
$1,314.26
(WHICHEVER IS GREATER)
REQUIRED AMOUNT OF SECURITY =
$3, 485.07
NOTE: Total Acres' represents total disturbed area.
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