HomeMy WebLinkAboutMAGNUM MOTORS OF LOVELAND (5900 S. COLLEGE AVE.) - PDP/FDP - FDP130016 - REPORTS - DRAINAGE REPORTDrainage Letter
Date: June 12, 2013
Project: 5900 S. College Avenue | Lot 1, Kelmar Strip Project No. 379-035
Fort Collins, Colorado
Attn: Mr. Wes Lamarque
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
Dear Wes:
This Drainage Letter accompanies a PDP/FDP submittal for Lot 1, Kelmar Strip, which is located at
5900 S. College Avenue, Fort Collins, Colorado. The Conceptual Review Staff Comments from June
13, 2011 indicate the former C-Store/fuel use had been vacant for more than twelve months, at
that time. The building/site is still vacant and needs to be brought into compliance with City
regulations. Therefore, treatment of developed stormwater runoff from Lots 1, 2 and 3, Kelmar Strip
is required. We propose to accomplish the foregoing by modifying the existing water quantity outlet
structure to include Water Quality Capture Volume (WQCV).
The proposed site improvements are limited to modifying the existing signage and lighting as well as
improving existing landscaping. The existing site grades will not be modified, nor are changes to the
existing utilities (i.e., domestic water, sanitary sewer and storm drain) being proposed.
The existing detention pond is located in the south part of Lot 2, Kelmar Strip. It's as-constructed
condition was documented in Drainage Certification for Lot 2, Kelmar Strip (Dated: November 9,
2004 | Loonan & Assoc. Inc.). The contour elevation and area information contained in the
aforementioned letter was used as the basis for determining the depth of the WQCV proposed
herein. The existing outlet structure dimensions were field verified by Northern Engineering Services
on April 24, 2013. The existing structure is a concrete box with inside dimensions of approximately
2.75 feet by 5.25 feet. A metal orifice plate, with a circular opening, is bolted to the outside of the
box, and was sized to release ±5.27 cfs during the 100-year storm event.
The WQCV volume and plate calculations (see attached) are based on a tributary area of 3.21
acres. We understand this area to be similar to that which was used to design the existing detention
pond. This area includes: Lot 1 (1.24 ac), Lot 2 (1.27 acre) and Lot 3 (0.61 acre). The
imperviousness of this area was estimated to be ±80 percent. Given the forgoing inputs, a WQCV
of 0.10 ac-ft (4461 cu.ft.) is required. This volume will be provided in the bottom of the existing
detention pond and included in the complete 100-year quantity volume. The water quantity volume
will continue release at a maximum rate of ±5.27 cfs, during the 100-year storm event, through a
rectangular weir. The proposed outlet structure modifications are shown on Exhibit 1 (see
attached).
Please do not hesitate to contact me if you have questions or require additional information.
Sincerely,
Herman H. Feissner, PE
enc.
5900 S. College Avenue
379-035
Stage - Storage Calculation
Project Number: 379-035
Fort Collins, Colorado
H. Feissner Date: 5/1/2013
Project Number:
Project Location:
Calculations By: H. Feissner Date: 5/1/2013
Pond No.: Existing Pond
Calculations By:
Design Point Existing Pond
Required Volume Water Surface Elevation (WSE)
Existing Pond
WQCV
4461 ft3 4982.73 ft.
Design Point
Design Storm
Require Volume= 4461 ft3 4982.73 ft.
Design Storm 100-yr
ft3 N/A ft.
Require Volume=
Required Volume= N/A ft3 N/A ft.
Contour
Elevation1
Contour
Area1 Depth
Incremental
Volume - Avg. End
Cumulative Volume
Avg. End
Incremental Volume
- Conic
Cummulative
Volume Conic (X-
Elevation1 Area1
Area
Avg. End - Conic
values)
ft3 ft ft. ft3 ft ft3 ft ft3 ft ft3 ft
4,980.94 0 0.00 0 0 0 0
4,982.00 3051 1.06 1617 1617 1078 1078
4,983.00 6465 1.00 4758 6375 4652 5730
4,984.00 7565 1.00 7015 13390 7008 12738
4,985.00 8986 1.00 8276 21666 8265 21004
4,986.00 15606 1.00 12296 33962 12145 33148
Note 1 - The contour elevation and contour area information shown herein is from Drainage Certification for Lot 2, Kelmar Strip
(Dated: November 9, 2004 | Loonan & Assoc. Inc.)
4,987.00
4,986.00
4,985.00
4,986.00
4,985.00
4,984.00
Contour Elevation
4,983.00
Contour Elevation
4,983.00
Contour Elevation
4,982.00
Sheet 1 of 4
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia
Ia = 80 %
B) Tributary Area's Imperviousness Ratio (i = Ia / 100 ) i = 0.80
C) Contributing Watershed Area Area = 3.12 ac
D) For Watersheds Outside of the Denver Region, Depth of Average d6 = in
Runoff Producing Storm
E) Design Concept
(Select EURV when also designing for flood control)
F) Design Volume (1.2 WQCV) Based on 40-hour Drain Time VDESIGN
= 0.102 ac-ft
(VDESIGN = (1.0 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12 * Area * 1.2)
G) For Watersheds Outside of the Denver Region, VDESIGN OTHER
= ac-ft
Water Quality Capture Volume (WQCV) Design Volume
(VWQCV OTHER = (d
6*(VDESIGN
/0.43))
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VDESIGN USER
= ac-ft
(Only if a different WQCV Design Volume is desired)
I) Predominant Watershed NRCS Soil Group
J) Excess Urban Runoff Volume (EURV) Design Volume
For HSG A: EURVA = (0.1878i - 0.0104)*Area EURV = ac-f t
For HSG B: EURVB = (0.1178i - 0.0042)*Area
For HSG C/D: EURVC/D = (0.1043i - 0.0031)*Area
Design Procedure Form: Extended Detention Basin (EDB)
5900 S. College Avenue
Northern Engineering
April 30, 2013
Fort Collins, Colorado | Existing Detention Pond
H. Feissner
Choose One
Excess Urban Runoff Volume (EURV)
Choose One
A
B
C / D
Water Quality Capture Volume (WQCV)
2. Basin Shape: Length to Width Ratio L : W = 4.0 : 1
(A basin length to width ratio of at least 2:1 will improve TSS reduction.)
3. Basin Side Slopes
A) Basin Maximum Side Slopes Z = 4.00 ft / ft
(Horizontal distance per unit vertical, 4:1 or flatter preferred)
4. Inlet
A) Describe means of providing energy dissipation at concentrated
inflow locations:
379-035_UD-BMP_v3.02, EDB 4/30/2013, 11:02 AM
Sheet 2 of 4
Designer:
Company:
Date:
Project:
Location:
5. Forebay
A) Minimum Forebay Volume VFMIN
= 0.002 ac-ft
(VFMIN = 2% of the WQCV)
B) Actual Forebay Volume VF
= ac-ft
C) Forebay Depth DF
= in
(DF = 18 inch maximum)
D) Forebay Discharge
i) Undetained 100-year Peak Discharge Q100
= cfs
ii) Forebay Discharge Design Flow QF
= cfs
(QF = 0.02 * Q
100)
E) Forebay Discharge Design
F) Discharge Pipe Size (minimum 8-inches) Calculated DP = in
G) Rectangular Notch Width Calculated WN
= in
PROVIDE A CONSISTENT LONGITUDINAL
6. Trickle Channel SLOPE FROM FOREBAY TO MICROPOOL
WITH NO MEANDERING. RIPRAP AND
A) Type of Trickle Channel SOIL RIPRAP LINED CHANNELS ARE
NOT RECOMMENDED.
MINIMUM DEPTH OF 1.5 FEET
F) Slope of Trickle Channel S = 0.0100 ft / ft
5900 S. College Avenue
April 30, 2013
Northern Engineering
Design Procedure Form: Extended Detention Basin (EDB)
(flow too small for berm w/ pipe)
Fort Collins, Colorado | Existing Detention Pond
H. Feissner
Choose One
Wall with Rect. Notch
Berm With Pipe
Choose One
Concrete
Soft Bottom
Wall with V-Notch Weir
7. Micropool and Outlet Structure
A) Depth of Micropool (2.5-feet minimum) DM
= ft
B) Surface Area of Micropool (10 ft
2
minimum) A
M = sq ft
C) Outlet Type
D) Depth of Design Volume (EURV or 1.2 WQCV) Based on the Design H = 1.79 feet
Concept Chosen Under 1.E.
E) Volume to Drain Over Prescribed Time WQCV = 0.0854 ac-ft
F) Drain Time TD
= 40 hours
Sheet 3 of 4
Designer:
Company:
Date:
Project:
Location:
8. Initial Surcharge Volume
A) Depth of Initial Surcharge Volume DIS
= in
(Minimum recommended depth is 4 inches)
B) Minimum Initial Surcharge Volume VIS = cu ft
(Minimum volume of 0.3% of the WQCV)
C) Initial Surcharge Provided Above Micropool Vs= cu ft
9. Trash Rack
A) Type of Water Quality Orifice Used
B) Water Quality Screen Open Area: At = 38.5*(e
-0.095D
)*Aot
At = 39 square inches
C) For 2", or Smaller, Circular Opening (See Fact Sheet T-12):
i) Width of Water Quality Screen and Concrete Opening (Wopening) W
opening = inches
ii) Height of Water Quality Screen (HTR) H
TR = inches
iii) Type of Screen, Describe if "Other"
D) For 2" High Rectangular Opening:
i) Width of Rectangular Opening (Worifice) W = inches
Design Procedure Form: Extended Detention Basin (EDB)
April 30, 2013
5900 S. College Avenue
Fort Collins, Colorado | Existing Detention Pond
Northern Engineering
H. Feissner
Choose One
Circular (up to 2" diameter)
Rectangular (2" high)
Choose One
S.S. Well Screen with 60% Open Area*
Other (Describe):
i) Width of Rectangular Opening (Worifice) W = inches
ii) Width of Water Quality Screen Opening (Wopening) W
opening = ft
iii) Height of Water Quality Screen (HTR) H
TR = ft
iv) Type of Screen, Describe if "Other"
v) Cross-bar Spacing inches
vi) Minimum Bearing Bar Size
Choose One
Aluminum Amico-Klemp SR Series (or equal)
Other (Describe):
379-035_UD-BMP_v3.02, EDB 4/30/2013, 11:02 AM
Sheet 4 of 4
Designer:
Company:
Date:
Project:
Location:
10. Overflow Embankment
A) Describe embankment protection for 100-year and greater overtopping:
B) Slope of Overflow Embankment ZE
= ft / ft
(Horizontal distance per unit vertical, 4:1 or flatter preferred)
11. Vegetation
12. Access
A) Describe Sediment Removal Procedures
Notes:
5900 S. College Avenue
Fort Collins, Colorado | Existing Detention Pond
Design Procedure Form: Extended Detention Basin (EDB)
April 30, 2013
Northern Engineering
H. Feissner
Choose One
Irrigated
Not Irrigated
379-035_UD-BMP_v3.02, EDB 4/30/2013, 11:02 AM
Weir Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2012 by Autodesk, Inc. Tuesday, Apr 30 2013
100-year Weir Sizing | Design Flow=5.27 cfs
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 0.55
Total Depth (ft) = 2.06
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 5.27
Highlighted
Depth (ft) = 2.02
Q (cfs) = 5.270
Area (sqft) = 1.11
Velocity (ft/s) = 4.73
Top Width (ft) = 0.55
0 .25 .5 .75 1 1.25
Depth (ft) 100-year Weir Sizing | Design Flow=5.27 cfs Depth (ft)
-1.00 -1.00
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
Weir W.S. Length (ft)
(Min TD for WQCV= 40 hours; Max T
D for EURV= 72 hours)
G) Recommended Maximum Outlet Area per Row, (Ao) A
o = 0.25 square inches
H) Orifice Dimensions:
i) Circular Orifice Diameter or Dorifice
= 1 / 2 inches
ii) Width of 2" High Rectangular Orifice Worifice
= inches
I) Number of Columns nc
= 1 number
J) Actual Design Outlet Area per Row (Ao) A
o = 0.20 square inches
K) Number of Rows (nr) nr
= 5 number
L) Total Outlet Area (Aot) A
ot = 1.1 square inches
M) Depth of WQCV (HWQCV) H
WQCV = feet
(Estimate using actual stage-area-volume relationship and VWQCV)
N) Ensure Minimum 40 Hour Drain Time for WQCV TD WQCV
= hours
Choose One
Orifice Plate
Other (Describe):
379-035_UD-BMP_v3.02, EDB 4/30/2013, 11:02 AM
4,981.00
4,980.00
0 5000 10000 15000 20000 25000 30000 35000
Cummulative Volume, cu. ft.
5/1/201310:43 AM D:\Projects\379-035\Drainage\Detention\379-035__Detention Pond\Stage_Storage