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Home My WebLink AboutBUCKINGHAM PLACE, 2ND FILING - PDP/FDP - FDP120019 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTApex EEEEnnnnggggiiiinnnneeeeeeeerrrriiiinnnngggg 908 Laporte Avenue ■ Fort Collins, Colorado 80521 ■ 970.219.2834 November 9, 2012 Mr. Glen Schleuter Stormwater Department City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80521 RE: Preliminary Drainage Letter for Buckingham Place, Second Filing APEX Project #45-104 Dear Glen, We have prepared this initial preliminary drainage letter for Buckingham Place, Second Filing for your review and approval. The existing property is an undeveloped 12,529 square-foot lot on the east side of Third Street approximately 200 lf north of Lincoln Avenue. It is in the Dry Creek Master Drainage This project proposes to develop to single family residential lots on the property. The following is a summary of the impacts to the drainage systems on and off the site. In addition, supporting calculations and a drainage exhibit have been attached. Runoff The existing site (Basin EX) drains to the east and has 0.02 cfs and 0.78 cfs of runoff leaving the site in the 2-year and 100-year storms, respectively. In the developed condition, approximately 0.17 acres drains to the west and 0.12 acres drains to the east. The area draining to the west is defined as Basin A and will have 0.13 cfs and 0.87 cfs of runoff leaving the site in the 2-year and 100-year storms, respectively. The area draining to the east is defined as Basin B and will have 0.02 cfs and 0.41 cfs of runoff leaving the site in the 2-year and 100-year storms, respectively. Detention Storage The entire site is estimated to be approximately 50% to 60% impervious when built out. The Dry Creek Master Drainage plan estimated this area at 90% impervious. Due to the reduction in the planned imperviousness, the size of the site, and the difficulty in providing detention we are not proposing any detention storage with this project. Water Quality The small site, location of the Coy Ditch, and proximity to adjacent storm sewer make it very difficult to provide typical water quality. The residential site will have an area of non paved surfaces at the front and rear of the lot. These areas will intercept the stormwater runoff that comes from the roof, driveway, and patio areas and provide some water quality via “disconnected impervious areas”. This is the extent of water quality that we are proposing. Erosion Control Erosion and Sediment Control devices will be implemented on the site as needed. It is anticipated that onsite runoff will be contained by straw wattles surrounding the site. Inlet protection will be placed adjacent to the inlet south of this site on 3rd Street. Summary Due to the size of this small site, the proposed development of the site will have minimal impact to the stormwater r. The runoff from the site is less than what was originally planned for in the Master Drainage Plan, therefore no on site detention or downstream improvements are included with this project. I appreciate your time and consideration in reviewing this submittal. Please contact me at 970- 217-7420 or seliason@bluesky-engineer.com if you have any questions. Sincerely, Samuel M. Eliason, P.E. APEX Engineering Attachments: • Calculation of Peak Runoffs (EX 2-yr, EX 100-yr, A 2-yr, A-100 yr, B 2-yr, B 100-yr) • Drainage Exhibit Project Title: Catchment ID: I. Catchment Hydrologic Data Catchment ID = EX Area = 0.29 Acres Percent Imperviousness = 2.00 % NRCS Soil Type = B A, B, C, or D II. Rainfall Information I (inch/hr) = C1 * P1 /(C2 + Td)^C3 Design Storm Return Period, Tr = 2 years (input return period for design storm) C1 = 28.50 (input the value of C1) C2= 10.00 (input the value of C2) C3= 0.786 (input the value of C3) P1= 0.82 inches (input one-hr precipitation--see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = 0.03 Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.) 5-yr. Runoff Coefficient, C-5 = 0.08 Overide 5-yr. Runoff Coefficient, C = (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration NRCS Land Heavy Tillage/ Short Nearly Grassed Type Meadow Field Pasture/ Bare Swales/ Lawns Ground Waterways Conveyance 2.5 5 7 10 15 Calculations: Reach Slope Length 5-yr NRCS Flow Flow ID S L Runoff Convey- Velocity Time Coeff ance V Tf ft/ft ft C-5 fps minutes input input output input output output Overland 0.0100 120 0.08 0.10 20.14 1 2 3 4 5 Sum 120 Computed Tc = 20.14 Regional Tc = 10.67 IV. Peak Runoff Prediction using Regional Tc Rainfall Intensity at Tc, I = 1.61 inch/hr Rainfall Intensity at Tc, I = 2.16 inch/hr Peak Flowrate, Qp = 0.01 cfs Peak Flowrate, Qp = 0.02 cfs CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Buckingham Place, Second Filing Basin EX, Existing 2-year Discharge Peak Runoff Prediction using Computed Tc Paved Areas & (Sheet Flow) 20 Shallow Paved Swales 3rd Street - UD Rational Basin Existing 2yr Existing.xls, Tc and PeakQ 11/9/2012, 3:02 PM Project Title: Catchment ID: I. Catchment Hydrologic Data Catchment ID = EX Area = 0.29 Acres Percent Imperviousness = 2.00 % NRCS Soil Type = B A, B, C, or D II. Rainfall Information I (inch/hr) = C1 * P1 /(C2 + Td)^C3 Design Storm Return Period, Tr = 100 years (input return period for design storm) C1 = 28.50 (input the value of C1) C2= 10.00 (input the value of C2) C3= 0.793 (input the value of C3) P1= 2.91 inches (input one-hr precipitation--see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = 0.36 Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.) 5-yr. Runoff Coefficient, C-5 = 0.08 Overide 5-yr. Runoff Coefficient, C = (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration NRCS Land Heavy Tillage/ Short Nearly Grassed Type Meadow Field Pasture/ Bare Swales/ Lawns Ground Waterways Conveyance 2.5 5 7 10 15 Calculations: Reach Slope Length 5-yr NRCS Flow Flow ID S L Runoff Convey- Velocity Time Coeff ance V Tf ft/ft ft C-5 fps minutes input input output input output output Overland 0.0100 120 0.08 0.10 20.14 1 2 3 4 5 Sum 120 Computed Tc = 20.14 Regional Tc = 10.67 IV. Peak Runoff Prediction using Regional Tc Rainfall Intensity at Tc, I = 5.57 inch/hr Rainfall Intensity at Tc, I = 7.51 inch/hr Peak Flowrate, Qp = 0.58 cfs Peak Flowrate, Qp = 0.78 cfs CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Buckingham Place, Second Filing Basin EX, Existing 100-year Discharge Peak Runoff Prediction using Computed Tc Paved Areas & (Sheet Flow) 20 Shallow Paved Swales 3rd Street - UD Rational Basin Existing 100yr Existing.xls, Tc and PeakQ 11/9/2012, 3:01 PM Project Title: Catchment ID: I. Catchment Hydrologic Data Catchment ID = A Area = 0.12 Acres Percent Imperviousness = 75.00 % NRCS Soil Type = B A, B, C, or D II. Rainfall Information I (inch/hr) = C1 * P1 /(C2 + Td)^C3 Design Storm Return Period, Tr = 2 years (input return period for design storm) C1 = 28.50 (input the value of C1) C2= 10.00 (input the value of C2) C3= 0.786 (input the value of C3) P1= 0.82 inches (input one-hr precipitation--see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = 0.51 Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.) 5-yr. Runoff Coefficient, C-5 = 0.54 Overide 5-yr. Runoff Coefficient, C = (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration NRCS Land Heavy Tillage/ Short Nearly Grassed Type Meadow Field Pasture/ Bare Swales/ Lawns Ground Waterways Conveyance 2.5 5 7 10 15 Calculations: Reach Slope Length 5-yr NRCS Flow Flow ID S L Runoff Convey- Velocity Time Coeff ance V Tf ft/ft ft C-5 fps minutes input input output input output output Overland 0.0100 83 0.54 0.15 9.22 1 0.0050 114 20.00 1.41 1.34 2 3 4 5 Sum 197 Computed Tc = 10.56 Regional Tc = 11.09 IV. Peak Runoff Prediction using Regional Tc Rainfall Intensity at Tc, I = 2.17 inch/hr Rainfall Intensity at Tc, I = 2.13 inch/hr Peak Flowrate, Qp = 0.13 cfs Peak Flowrate, Qp = 0.13 cfs CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Buckingham Place, Second Filing Basin A, 2-year Discharge for Offsite Design Peak Runoff Prediction using Computed Tc Paved Areas & (Sheet Flow) 20 Shallow Paved Swales 3rd Street - UD Rational Basin A 2yr STORM A.xls, Tc and PeakQ 11/9/2012, 3:13 PM Project Title: Catchment ID: I. Catchment Hydrologic Data Catchment ID = A Area = 0.17 Acres Percent Imperviousness = 75.00 % NRCS Soil Type = B A, B, C, or D II. Rainfall Information I (inch/hr) = C1 * P1 /(C2 + Td)^C3 Design Storm Return Period, Tr = 100 years (input return period for design storm) C1 = 28.50 (input the value of C1) C2= 10.00 (input the value of C2) C3= 0.786 (input the value of C3) P1= 2.91 inches (input one-hr precipitation--see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = 0.66 Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.) 5-yr. Runoff Coefficient, C-5 = 0.54 Overide 5-yr. Runoff Coefficient, C = (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration NRCS Land Heavy Tillage/ Short Nearly Grassed Type Meadow Field Pasture/ Bare Swales/ Lawns Ground Waterways Conveyance 2.5 5 7 10 15 Calculations: Reach Slope Length 5-yr NRCS Flow Flow ID S L Runoff Convey- Velocity Time Coeff ance V Tf ft/ft ft C-5 fps minutes input input output input output output Overland 0.0100 83 0.54 0.15 9.22 1 0.0050 114 20.00 1.41 1.34 2 3 4 5 Sum 197 Computed Tc = 10.56 Regional Tc = 11.09 IV. Peak Runoff Prediction using Regional Tc Rainfall Intensity at Tc, I = 7.70 inch/hr Rainfall Intensity at Tc, I = 7.55 inch/hr Peak Flowrate, Qp = 0.87 cfs Peak Flowrate, Qp = 0.85 cfs CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Buckingham Place, Second Filing Basin A, 100-year Runoff Peak Runoff Prediction using Computed Tc Paved Areas & (Sheet Flow) 20 Shallow Paved Swales 3rd Street - UD Rational Basin A 100yr STORM A.xls, Tc and PeakQ 11/9/2012, 3:00 PM Project Title: Catchment ID: I. Catchment Hydrologic Data Catchment ID = B Area = 0.12 Acres Percent Imperviousness = 11.00 % NRCS Soil Type = B A, B, C, or D II. Rainfall Information I (inch/hr) = C1 * P1 /(C2 + Td)^C3 Design Storm Return Period, Tr = 2 years (input return period for design storm) C1 = 28.50 (input the value of C1) C2= 10.00 (input the value of C2) C3= 0.786 (input the value of C3) P1= 0.82 inches (input one-hr precipitation--see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = 0.06 Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.) 5-yr. Runoff Coefficient, C-5 = 0.14 Overide 5-yr. Runoff Coefficient, C = (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration NRCS Land Heavy Tillage/ Short Nearly Grassed Type Meadow Field Pasture/ Bare Swales/ Lawns Ground Waterways Conveyance 2.5 5 7 10 15 Calculations: Reach Slope Length 5-yr NRCS Flow Flow ID S L Runoff Convey- Velocity Time Coeff ance V Tf ft/ft ft C-5 fps minutes input input output input output output Overland 0.0500 50 0.14 0.12 7.18 1 2 3 4 5 Sum 50 Computed Tc = 7.18 Regional Tc = 10.28 IV. Peak Runoff Prediction using Regional Tc Rainfall Intensity at Tc, I = 2.50 inch/hr Rainfall Intensity at Tc, I = 2.19 inch/hr Peak Flowrate, Qp = 0.02 cfs Peak Flowrate, Qp = 0.01 cfs CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Buckingham Place, Second Filing Basin B, 2-year Discharge for Offsite Design Peak Runoff Prediction using Computed Tc Paved Areas & (Sheet Flow) 20 Shallow Paved Swales 3rd Street - UD Rational Basin B 2yr STORM B.xls, Tc and PeakQ 11/9/2012, 3:02 PM Project Title: Catchment ID: I. Catchment Hydrologic Data Catchment ID = B Area = 0.12 Acres Percent Imperviousness = 11.00 % NRCS Soil Type = B A, B, C, or D II. Rainfall Information I (inch/hr) = C1 * P1 /(C2 + Td)^C3 Design Storm Return Period, Tr = 100 years (input return period for design storm) C1 = 28.50 (input the value of C1) C2= 10.00 (input the value of C2) C3= 0.793 (input the value of C3) P1= 2.91 inches (input one-hr precipitation--see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = 0.41 Overide Runoff Coefficient, C = (enter an overide C value if desired, or leave blank to accept calculated C.) 5-yr. Runoff Coefficient, C-5 = 0.14 Overide 5-yr. Runoff Coefficient, C = (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration NRCS Land Heavy Tillage/ Short Nearly Grassed Type Meadow Field Pasture/ Bare Swales/ Lawns Ground Waterways Conveyance 2.5 5 7 10 15 Calculations: Reach Slope Length 5-yr NRCS Flow Flow ID S L Runoff Convey- Velocity Time Coeff ance V Tf ft/ft ft C-5 fps minutes input input output input output output Overland 0.0500 50 0.14 0.12 7.18 1 2 3 4 5 Sum 50 Computed Tc = 7.18 Regional Tc = 10.28 IV. Peak Runoff Prediction using Regional Tc Rainfall Intensity at Tc, I = 8.70 inch/hr Rainfall Intensity at Tc, I = 7.63 inch/hr Peak Flowrate, Qp = 0.41 cfs Peak Flowrate, Qp = 0.36 cfs CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Buckingham Place, Second Filing Basin B, 100-year Discharge for Swale B and Offsite Design Peak Runoff Prediction using Computed Tc Paved Areas & (Sheet Flow) 20 Shallow Paved Swales 3rd Street - UD Rational Basin B 100yr STORM B.xls, Tc and PeakQ 11/9/2012, 3:01 PM 10' SCALE: 1" = 10' 0 10' NO. DATE BY REVISION 1 2 3 4 5 6 DESIGNED: DRAWN: CHECKED: PROJECT NO.: DATE: PRELIMINARY NOT FOR CONSTRUCTION SHEET: OF 11/9/2012 45-104 FORT COLLINS, COLORADO BUCKINGHAM PLACE, SECOND FILING C9 7 APPROV. 908 Laporte Avenue Fort Collins, CO 80521 (970) 219-2834 'PIKPGGTKPI GRADING, DRAINAGE AND EROSION CONTROL PLAN C5 B.G. B.G. D.D. NOTES: