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Home My WebLink AboutSPRING CREEK MANOR AT SPRINGMEADOWS PUD - AMENDED FINAL - 1-94 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1 EFFECTIVENESS CALCULATIONS. ---------------------------------------------------------------------- PROJECT: SPRING CREEK HEALTH CARE CENTER STANDARD FORM B COMPLETED BY: DiC DATE: 12/30/93 Erosion Control C-Factor P-Factor Method ---------------------------------------------------------- Value Value Comment BARE SOIL 1.00 1.00 SOD GRASS 0.01 1.00 ROADS/WALKS 0.01 -1.00 SILT FENCE 1.00 0.50 ------------------- --- . MAJORS PS SUB AREA BASIN (A) BASIN (Ac) A 82.5 0.10 ------------------------------------- CALCULATIONS ------------------------------------------- GRASS AREA = 0.070 AC WALKS = 0.007 AC BARE SOIL = 0.023 AC -WHILE FOUNDATION & SLAB ARE CONSTRUCTED WTD C-FACTOR = [(0.07)(0.01)+(0.007)(0.01 +(0.023)(1.0)]/O.10 = 0.24 WTD P—FACTOR = 0.50 EFF = [1—(0.24)(0.50)]x100 = 88.0% EFF > PS OK ----------------------- DI/SF-B:1989 RAINFALL PERFORMANCE STANDARD EVALUATION --------------------------------------------------------------------- PROJECT: SPRING CREEK HEALTH CARE CENTER STANDARD FORM A COMPLETED BY: TMC DATE: 12/30/93 -------------------------------------------------------------------- DEVELOPED ERODIBILITY Asb Lsb I Ssb lLb ! Sb PS SUBBASIN ' ZONE + (ac) ` (ft) I W (feet) I - W I ( ) --------- ----------- -------I------- ----------�- ----I A Mod. 0.10 100 f 5.0 1 100 , 5.0 i 82.5 •--------------------------------------------------------------------I )I/SF-A:1989 APPENDIX C EROSION CONTROL CALCULATIONS No Text (2) Determine 100 Year Storm Event Runoff Q = gCIA Equation 3.2.1 where: Cf = Frequency Adjustment Factor C = Runoff Coefficient I = Rainfall Intensity (Inches/Hour) A = Drainage Area (Acres) determine rainfall intensity: I = 6.9 inches/hour Ft. Collins Rainfall Intensity Duration Curve determine proposed flow: Q = CfCIA = (1.25)(0.61)(6.9)(4.976) = 26.2 CFS 0 Proposed Runoff (1) Determine Time Of Concentration: Tc=1.87(1.1 -CQf)D1/2 51/3 Composite Runoff Coefficient Land Use Area SF Building 54,146 Pavement/Concrete 55,950 "Lawn 106,659 216,755 4.976 AC Equation 3.1.7 Table 3-3 25.0% 25.8% 49.2% 100.0% Composite Coefficients "Lawn - Assume Heavy Soils And Average Slope Site Conditions: D = Length of basin S = Average basin slope C = Runoff Coefficient Cf = Frequency adjustment factor C = 0.61 Cf = 1.25 S = 2.4% D = 500' Tc = 1.87[1.1-(0.61)!(1.25)1(500):!L-2 (2.4)1 / 3 = 10.5 Minutes H. C 0.95 0.95 0.25 Table 3-4 0.61 (2) Determine 100 Year Storm Event Runoff Q = CfCIA Equation 3.2.1 where: q = Frequency Adjustment Factor C = Runoff Coefficient I = Rainfall Intensity (Inches/Hour) A = Drainage Area (Acres) determine rainfall intensity: I = 6.9 inches/hour Ft. Collins Rainfall Intensity Duration Curve determine existing flow: Q = gCIA = (1.25)(0.59)(6.9)(4.976) = 25.3 CFS 7 HYDROLOGIC COMPUTATIONS Use Rational Method for evaluation. Existing Runoff (1) Determine Time Of Concentration: Tc=1.87(1. 1 - C Qf)_D1 /2 51/3 Composite Runoff Coefficient Land Use Area SF Building 52,516 Pavement/Concrete 53,195 *Lawn 111,044 216,755 4.976 AC Equation 3.1.7 Table 3-3 24.2% 24.5% 51.2% 100.0% Composite Coefficients *Lawn - Assume Heavy Soils And Average Slope Site Conditions: D = Length of basin S = Average basin slope C = Runoff Coefficient Cf = Frequency adjustment factor C = 0.59 Cf = 1.25 S = 2.4% D = 500' Tc = 1.87[1.1-(0.59)(1.25)1(500)1 /2 (2.4)1 / 3 = 11.3 Minutes 31 C 0.95 0.95 0.25 Table 3-4 0.59 APPENDIX B HYDROLOGY CALCULATIONS DRAINAGE BASIN A 1000 SF ADDITION PHYSICAL THERAPI & OFFICE SPACE INSTALL SIDEWALK STUART STREET LEGEND ® EXISTING BUILDING PROPOSED BUILDING a PROPOSED SIDEWALK ® DRAINAGE BASIN EVALUATED mc* DRAINAGE FLOW DIRECTION 630 SF ADDITION DINING ROOM 800 SF ADDITION OFFICE SPACE w Z) z Q Q w J DRAINAGE & EROSION CONTROL PLAN SPRING CREEK HEALTH CARE CENTER FT. COLLINS, COLORADO DATE: 12/27/93 SCALE: T Total Engineering Service, Inc... NNNNMNNNNFNNNNNNNN PROJ. NO: 93-168 1 = 100, E S 3310 STATE STREET EvAIIs. (aos739 )01 R o &*20-5DRAWN BY: T.M.C. SHEET 1 2u CHECKED BY: T.M.C. OF 1 APPENDIX A DRAINAGE & EROSION CONTROL PLAN 4T E S Total Engineering Service, Inc. 3310 State Street . Evans, CO 80620 • (303) 339-5215 Mr. Loren Bley December 30, 1993 Page Four Please contact me if you have any questions concerning this report. Sincerely, TOTAL ENGINEERING SERVICE, INC. 7e; Tom Cope, P.E. President enc. 93-168 Total Engineering Service, Inc. 3310 State Street e Evans, CO 80620 • (303) 339-5215 Mr. Loren Bley December 30, 1993 Page Three We have evaluated the erosion impact in accordance to the City of Ft. Collins Drainage Manual. See Appendix C. The addition in the north- west corner was evaluated and determined to require a performance standard of 82.5%. This addition will be built in a sodded grass area. Therefore, the only erosion anticipated is in the area of the foundation. The installation of a silt fence up gradient and adjacent to the sidewalk is recommended and shown on the Erosion Control Plan. An effectiveness of 88.0% is achieved with the installation of the silt fence. Therefore, the erosion control meets the standards set by the City of Fort Collins. The other additions are not anticipated to have any significant impact to erosion due to their locations and how they will be constructed. Wind erosion is not anticipated to impact the site. The site is located in the moderate erodibility zone and meets the two hundred foot (200') maximum barrier spacing in the direction of the prevailing winds as required in the Drainage Manual. STI The Fort Collins Drainage Manual was used in the evaluation of the additions to this site. The criteria recommended in the Drainage Manual has been met. The additions were determined to: a) have a minimal impact to the 100 year storm event runoff; b) not alter the existing drainage flow pattern; c) the erosion anticipated from this site is minimal and can be controlled to meet the City of Fort Collins erosion criteria. We have found the additions to have no significant drainage or erosion impact to the site or to the City of Fort Collins. Therefore, we request the City of Fort Collins staff to view the additions favorable and recommend approval. u 4T4�3310 Total Engineering Service, Inc. E State Street . Evans, CO 80620 • (303) 339-5215 Mr. Loren Bley December 30, 1993 Page Two The proposed construction will consist of 1000 square feet of building located near the north-west corner of the building. This addition will be used for a Physical Therapy Room and additional office space. Along the eastern portion of the building an addition of 800 square feet will be added as a dining room and an existing roof- top patio will be converted into an office area. 100 Year Storm Event Impact The additional 1000 square feet of building added to the north-west part of the existing building is the only addition described above, that will have an impact on the 100 year storm runoff and potential erosion control. The other two additions are being constructed on materials containing similar imperviousness. Therefore, these additions will not impact the 100 year storm runoff. The 100 year storm event runoff was calculated for both the existing site and the site with the proposed additions. See Appendix B. The 100 year now is anticipated to increase by approximately three percent (3%) from 25.3 cubic feet per second (cfs) to 26.2 cfs. Drainage Pattern The additions do not alter the existing drainage flow patterns. The existing runoff sheet flows to swells created in the grass areas as well as in the paved areas. The additions are not being constructed in a manner to alter these patterns. Erosion Control Plan Construction will occur shortly after the City approves the plans. The anticipated construction starting date is in February, 1994. The additions are anticipated to have the foundation and slabs completed prior to April. Therefore, the erosion impact is anticipated to be minimal. T Total Engineering Service, Inc. E S 3310 State Street . Evans, CO 80620 • (303) 339-5215 December 30, 1993 Mr. Loren Bley Bley Associates Architects 2020 Clubhouse Drive Greeley, CO 80634 Re: Spring Creek Health Care Center, Ft. Collins, Colorado Dear Loren: This drainage and erosion control plan has been submitted to meet the criteria requested by Glenn Schlueter, City of Fort Collins Storm Water Utility Engineer. This criteria was discussed with Mr. Schlueter with members of your office as well as verified by telephone on December 22, 1993 by myself. The following items are evaluated in this report based on the information requested by the City: * Evaluate the 100 year storm event impact due to the addition. * Evaluate changes to the drainage pattern due to the addition. * Evaluate the need and recommend erosion control. Site Description The site is located on the north-west corner of Lemay Avenue and Stuart Street in Fort Collins. Positive drainage is to the north toward Spring Creek which passes along the north boundary of the property. See Drainage and Erosion Control Plan, Appendix A. The site consist of an existing health care center on 4.976 acres. The existing site contains approximately 52,500 square feet of building, 53,200 square feet of parking and sidewalks, the remainder being open space.