HomeMy WebLinkAboutDrainage Reports - 10/09/20010
SEAR BROWN
June 13, 2001
Basil Harridan
Fort Collins Storm Water Utility
700 Wood Street
Fort Collins, CO 80521
RE: Drainage Letter Report for the Lenz Building
Dear Basil,
AR,.-,ITECTURE 5285 McWhinney Blvd., Suite 190
ENGINEERING Loveland, CO 80538
PLANNING 970.461.2800 phone
970.461.2801 fax
www.seatbrown.com
This Drainage Letter Report is for Lenz Building addition that is attached to the west side of the building
at the northeast corner of Remington Street and Oak Street. The site is now an existing gravel parking lot
approximately 35 feet by 100 feet (.08 acres) see the drainage exhibit with the utility plans. There are
existing buildings to the east, north and west of the proposed building. The buildings to the east and north
take their roof drainage away from the proposed building. The building to the west has its roof drains on
the east side adjacent to the proposed buiding.
The roof drains for both the existing building to the west and the proposed building will discharge to. a
2'sidewalk culvert that will take the storm drainage directly to the gutter. The depth of the water in the
sidewalk culvert is 0.18 feet during the 100 year event (see attached calculations). The existing sidewalk
and existing driveway cut will be demolished and new sidewalk installed and follow its historic drainage
pattern.
No detention is anticipated. The Old Town Master Plan, Volume 2 Appendix C, D, E and F Draft Report
dated Feb 16, 2001 shows that Basin 402 (approximately 24 acres) anticipates the percent impervious to be
90%. This site is considered to be 100%.impervious, but due to the small size of the project, this would not
affect the 90% assumption that was made to determine the flows in the Master Plan.
No erosion control is anticipated because the building will take up the entire site. Normal site construction
codes should keep mud tracking under control.
The proposed site will ' rove the water quality for the area. ,Instead of a gravel parking lot with erosion
and oil concern roor WIN only catch airborne ust and leaves.
In conclusion, the site will not su crease runoff above the historic rate anticipated in the Old
Town Master plan and the w i3d%p� ! proved by replacing the parking area with roof area.
�NfO� Oyl
Yours S' ely,
31;
Allen-Mor ey, P.E.
roject Manager
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Lenz Building Sidewalk Culvert Calc.
Worksheet for Rectangular Channel
Project Description
Project File
c:\haestad\fmw\lenzbuil.fm2
Worksheet
Lenz Sidewalk Culvert
Flow Element
Rectangular Channel
Method
Manning's Formula
Solve For
Channel Depth
Input Data
Mannings Coefficient
0.013
Channel Slope
0.020000 ft/ft
Bottom Width
2.00 ft
Discharge
1.60 cfs
Results
Depth
0.18
ft
Flow Area
0.35
ftz
Wetted Perimeter
2.35
ft
Top Width
2.00
ft
Critical Depth
0.27
ft
Critical Slope
0.005239 ft/ft
Velocity
4.55
ft/s .,
Velocity Head
0.32
ft
Specific Energy
0.50
ft
Froude Number
1.91
Flow is supercritical.
09/06/01 FlowMaster v5.13
11:10:21 AM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1
Lenz Sidewalk Culvert
Cross Section for Rectangular Channel
Project Description
Project File
c:\haestad\fmw\lenzbuil.fm2
Worksheet
Lenz Sidewalk Culvert
Flow Element
Rectangular Channel
Method
Manning's Formula
Solve For
Channel Depth
Section Data
Mannings Coefficient
0.013
Channel Slope
0.020000 ft/ft
Depth
0.18 ft
Bottom Width
2.00 ft
Discharge
1.60 cfs
2.00 ft
', 0.18 ft
1N
V
H 1
NTS
09/06/01 FlowMaster v5.13
11:10:57 AM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1