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Home My WebLink AboutMAGNUM MOTORS OF LOVELAND (5900 S. COLLEGE AVE.) - PDP/FDP - FDP130016 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTDrainage Letter Date: May 1, 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