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HomeMy WebLinkAboutGenerations Investments Stormwater Calculations ASPEN ENGINEERS Stormwater Management Calculations for GENERATIONS INVESTMENTS 317 SW 5th Ave Meridian, Idaho Prepared for Jeff Hon Hon Contractors 16790 Rose Drive Nampa, Idaho (208)465-7797 Prepared by Lance Warnick P.E., Principal Engineer& Jordan Crain, Engineering Intern Aspen Engineers, Chartered OA Et, *VA, /to 10077 26 2Oi b iteOF Pi k Date Prepared September 26, 2014 Aspen Engineers, Chartered 485 W. Main St, Suite B PO Box 205 Kuna, Idaho 83634 (208)466-8181 Aspen File 14031 www.AspenEngineers.com P:\2014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc Stormwater Management Calculations for •ASPEN Generations Investments 317 SW 5th Ave ENGINEERS Meridian, Idaho Table of Contents Section and Description Page 1. Project Description 3 2. Sources of Information 3 3. Applicable Standards 4 4. Drawing Showing Site Drainage Areas 5 5. Stormwater Runoff Calculations for Drainage Area#1 6 6. Stormwater Runoff Calculations for Drainage Area #2 8 7. Stormwater Runoff Calculations for Drainage Area #3 10 Appendices A. Runoff Coefficient and Rainfall Intensity. 2 pages B. Infiltration Rate Information 1 page C. Sand /Grease Trap Cut Sheet 1 page IIMMIIIIMIIIIIIMIIIIIIIIIIMIIIMMOINIMBITIMIIIIIIIMINIMIIIs P:\2014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc Page 2 stormwater Management Calculations for Generations Investments l� 317 SW 5th Ave ENGINEERS Meridian, Idaho 1. Project Description These calculations and attachments provide the background for the design for a new stormwater management system associated with a new building and parking lot for Generations Investments, located at 317 SW 5th Ave in Meridian, Idaho. These calculations, together with the associated civil plans are meant to provide information on the proposed size and location of the seepage beds that will be used to manage stormwater runoff from the proposed building and parking lot. The proposed stormwater system will use pavement grading and roof drain lines to direct the stormwater runoff to three seepage beds in the site. A 1,000 gallon sand/grease trap will be used to help remove sediment and oil prior to entering each seepage bed. The distance between the baffles of the sand/grease trap was selected to keep the velocity of the water below 0.50 ft/sec to help provide residence time for sedimentation and in the trap. The seepage beds were sized to handle the anticipated runoff from the 100-year, 1-hour storm event using a combination of internal storage in the drain rock and the calculated percolation volume during the 1-hour design storm event. The seepage beds will be constructed with drain rock underlain by a 12" layer of ASTM C-33 filter sand. This will help provide some treatment before the stormwater infiltrates into the subsurface as well as promote infiltration into the subsurface. Since no site specific soils report was provided, for the purpose of these calculations an infiltration rate of 2 in/hr was assumed based off of surrounding projects. The elevation of seasonal high groundwater was estimated to be at 10 feet below existing grade based on experience in the surrounding area. The "hard-piped" roof drains shown in this design are an optional bid alternate and will only be used if the selected by the owner prior to construction. If this bid alternate is not selected, the roof runoff will be allowed to flow over the pavement and into the storm drain at the inlets. These roof drain improvements are not required by the City to have a functioning system. 2. Sources of Information The following sources of data were used in preparing these calculations: A. Urban Runoff Control Handbook for Ada and Canyon Counties, Idaho Ada/Canyon Waste Treatment Management Committee (January 1977). B. Architectural Site Layout provided by Dale Binning Architect (September 2014). P:12014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc Page 3 Stormwater Management Calculations for A S P E N Generations Investments 317 SW 5th Ave ENGINEERS Meridian, Idaho 3. Applicable Standards The following standards were used in preparing these calculations: C. Idaho Standard Public Works Construction Committee. Idaho Standards for Public Works Construction, Current Edition. D. City of Meridian,Ada County, Idaho. Supplementation Specification and Drawings to the Idaho Standards for Public Works Construction. E. Linsley, Ray, et al, 1992. Water Resources and Environmental Engineering, Fourth Edition, McGraw-Hill, Publishers, Inc. P:\2014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc Page 4 4. SITE DRAINAGE AREAS PAGE 5 0 25 50 100 SCALE (FT) DRAINAGE AREA #3 DRAINAGE AREA #1 6,280 SF 12,950 SF (0.14 ACRES) (0.30 ACRES) I of •--f311 ti/ i G reA II I A41I i . 4 I Vi.'''''://77,/// /\ \/- -- ,,,,-7/- /,7 IX Cii� 1 I \ 1 ! I I I 4 r/7/0/7/ II \ \" 4:e/ .///4\\ 1 \\ �,, . ,f\ '.. 1 1 0 I 1 Mw�i�i�ii�����iii���MMIE�1• `,----*--, ..... RD6 RD6 RD6 _-= :•���!�!�!.!Q•�.�.���!i!i?i�:�:•:�!� i i i I die , • air; \ 1'' .11 \( A I h ... ,n ... 14 -4-11 ___:___ ,___ _......._ —lb ,-I . `I I 0, I E DRAINAGE AREA #2 v am Ob 1 °®p 29,550 SF ® — (0.68 ACRES 1 1 1 I ) I w p 1 I 1 I I I 1 Project: Generations Investments Number: 14031 ASPEN Subject: Stormwater Runoff Calculations Date: 09/26/14 By: Jordan train Page: 6 ENGINEERS 5. RUNOFF CALCULATIONS FOR DRAINAGE AREA 1 A. FIND TIME OF CONCENTRATION(tc) Assume: The time of concentration (tc)for this area is defined as the time needed to reach the inlets from the point that is farthest away. It is assumed the time is 10 minutes. B. FIND PEAK DISCHARGE (Q) Design Storm 100-yr, 10-min Using the Rational Method (Q=CIA)for the 100-yr, 10-min storm which is the estimated time of concentration. Given: C Runoff Coefficient 0.80 See Appendix A.1 I Intensity 3.1 in/hr See Appendix A.2 A Drainage Area 0.30 acres See Page 5 Solution: Q Peak Discharge=C*I*A I 0.74 cfs C. FIND FLOW THROUGH DRAIN PIPE Given: Total Area D Pipe Diameter 12 in A Pipe flow area= pi*D^2/4 = 0.79 ft2 n Roughness coefficient= 0.009 R Hydraulic Radius= D/4 0.250 feet s Slope= 0.40% Solution: q Flow=[1.49/n * A*R^2/3 *s^0.5] q Flow= 3.26 cfs Check: Flow(q)>Peak Discharge(Q)? YES D. FIND VELOCITY IN GREASE TRAP(v) Given: Grease Trap Size 1,000 gal See Appendix C.1 wt Trap Width 4.00 ft d Distance Between Baffles 11 in a Flow Area=wt*d 3.67 sf Solution: v Velocity=Q/a 0.20 fps Check: Velocity(v) <0.5 fps? YES P:\2014\14031\Documents\Drainage Report\RevA\5. Storm Calcs- 14031 Project: Generations Investments Number: 14031 Subject: Stormwater Runoff Calculations Date: 09/26/14 ENGINEERS By: Jordan Crain Page: 7 E. FIND EXPECTED RUNOFF VOLUME(Vr)AND DESIGN VOLUME(Vd) Design Storm 100-yr, 1-hr Using the Rational Method (Q=CIA)for the 100-yr, 1-hr storm which is the estimated time of concentration. Given: C Runoff Coefficient 0.80 See Appendix A.1 I Intensity 1 in/hr See Appendix A.2 A Drainage Area 0.30 acres See Page 5 Q Discharge=C*I*A 0.24 cfs t Storm Duration 1 hr Solution: Vr Runoff Volume=Q*t 864 cf Vd Allow for 15%Sedimentation =Vr*1.15 994 cf F. FIND SEEPAGE BED PROPERTIES Given: H Height 5 ft Seepage Bed#1 =5'x 10'x 46' W Width 10 ft L Length 46 ft Solution: Vb Bed (Rock)Volume= He*W*L 2,300 cf Vs Storage Volume=Vb*0.4 920 cf G. FIND VOLUME FROM INFILTRATION Given: As Area of bottom of infiltration window 460 sf r Infiltration Rate 2 in/hr Assumed t Duration 1 hr Solution: Vi Volume from Infiltration =As*(r/12)*t 77 cf H.CHECK AVAILABLE STORAGE> REQUIRED STORAGE(V) Given: Va Available Storage Volume(Vs+Vi) 997 cf Vd Required Volume 994 cf Check: Available> Required? YES P:\2014\14031\Documents\Drainage Report\RevA\5. Storm Calcs- 14031 Project: Generations Investments Number: 14031 S P E]T Subject: Stormwater Runoff Calculations Date: 09/26/14 ENGINEERS By: Jordan Crain Page: 8 6. RUNOFF CALCULATIONS FOR DRAINAGE AREA 2 A. FIND TIME OF CONCENTRATION (tc) Assume: The time of concentration (tc)for this area is defined as the time needed to reach the inlets from the point that is farthest away. It is assumed the time is 10 minutes. B. FIND PEAK DISCHARGE(Q) Design Storm 100-yr, 10-min Using the Rational Method (Q=CIA)for the 100-yr, 10-min storm which is the estimated time of concentration. Given: C Runoff Coefficient 0.80 See Appendix A.1 I Intensity 3.1 in/hr See Appendix A.2 A Drainage Area 0.68 acres See Page 5 Solution: Q Peak Discharge=C*I*A 1.69 cfs C. FIND FLOW THROUGH DRAIN PIPE Given: Total Area D Pipe Diameter 12 in A Pipe flow area= pi*DA2/4 = 0.79 ft2 n Roughness coefficient= 0.009 R Hydraulic Radius= D/4 0.250 feet s Slope= 0.40% Solution: q Flow=[1.49/n * A*R^2/3 *s^0.5] q Flow= I 3.26 cfs Check: Flow(q)> Peak Discharge(Q)? YES D. FIND VELOCITY IN GREASE TRAP(v) Given: Grease Trap Size 1,000 gal See Appendix C.1 wt Trap Width 4.00 ft d Distance Between Baffles 11 in a Flow Area=wt*d 3.67 sf Solution: v Velocity= Q/a 0.46 fps Check: Velocity(v) <0.5 fps? YES P:\2014\14031\Documents\Drainage Report\RevA\5. Storm Calcs- 14031 Project: Generations Investments Number: 14031 S 1 i N Subject: Stormwater Runoff Calculations Date: 09/26/14 ENGINEERS By: Jordan Crain Page: 9 E. FIND EXPECTED RUNOFF VOLUME(Vr)AND DESIGN VOLUME(Vd) Design Storm 100-yr, 1-hr Using the Rational Method (Q=CIA)for the 100-yr, 1-hr storm which is the estimated time of concentration. Given: C Runoff Coefficient 0.80 See Appendix A.1 I Intensity 1 in/hr See Appendix A.2 A Drainage Area 0.68 acres See Page 5 Q Discharge =C*I*A 0.54 cfs t Storm Duration 1 hr Solution: Vr Runoff Volume=Q*t 1,958 cf Vd Allow for 15%Sedimentation =Vr*1.15 2,252 cf F. FIND SEEPAGE BED PROPERTIES Given: H Height 4 ft Seepage Bed#2=4'x 15'x 85' W Width 15 ft L Length 85 ft Solution: Vb Bed(Rock)Volume= He*W*L 5,100 cf Vs Storage Volume=Vb*0.4 2,040 cf G. FIND VOLUME FROM INFILTRATION Given: As Area of bottom of infiltration window 1275 sf r Infiltration Rate 2 in/hr Assumed t Duration 1 hr Solution: Vi Volume from Infiltration =As*(r/12)*t 213 cf H.CHECK AVAILABLE STORAGE> REQUIRED STORAGE (V) Given: Va Available Storage Volume(Vs+Vi) 2,253 cf Vd Required Volume 2,252 cf Check: Available> Required? YES P:\2014\14031\Documents\Drainage Report\RevA\5. Storm Calcs- 14031 Project: Generations Investments Number: 14031A S P E N Subject: Stormwater Runoff Calculations Date: 09/26/14 ENGINEERS By: Jordan Crain Page: 10 7. RUNOFF CALCULATIONS FOR DRAINAGE AREA 3 A. FIND TIME OF CONCENTRATION(tc) Assume: The time of concentration (tc)for this area is defined as the time needed to reach the inlets from the point that is farthest away. It is assumed the time is 10 minutes. B. FIND PEAK DISCHARGE(Q) Design Storm 100-yr, 10-min Using the Rational Method (Q=CIA)for the 100-yr, 10-min storm which is the estimated time of concentration. Given: C Runoff Coefficient 0.80 See Appendix A.1 I Intensity 3.1 in/hr See Appendix A.2 A Drainage Area 0.14 acres See Page 5 Solution: Q Peak Discharge=C*I*A 0.35 cfs C. FIND FLOW THROUGH DRAIN PIPE Given: Total Area D Pipe Diameter 12 in A Pipe flow area= pi*D^2/4 = 0.79 ft2 n Roughness coefficient= 0.009 R Hydraulic Radius= D/4 0.250 feet s Slope= 0.40% Solution: q Flow=[1.49/n * A*R^2/3 *s^0.5] q Flow= 3.26 cfs Check: Flow(q)>Peak Discharge(Q)? YES D. FIND VELOCITY IN GREASE TRAP(v) Given: Grease Trap Size 1,000 gal See Appendix C.1 wt Trap Width 4.00 ft d Distance Between Baffles 11 in a Flow Area=wt*d 3.67 sf Solution: v Velocity=Q/a I 0.09 fps Check: Velocity(v) <0.5 fps? YES P:\2014\14031\Documents\Drainage Report\RevA\5. Storm Calcs- 14031 Project: Generations Investments Number: 14031 C P I Ij Subject: Stormwater Runoff Calculations Date: 09/26/1410ENGINEERS By: Jordan Crain Page: E. FIND EXPECTED RUNOFF VOLUME(Vr)AND DESIGN VOLUME(Vd) Design Storm 100-yr, 1-hr Using the Rational Method (Q=CIA)for the 100-yr, 1-hr storm which is the estimated time of concentration. Given: C Runoff Coefficient 0.80 See Appendix A.1 I Intensity 1 in/hr See Appendix A.2 A Drainage Area 0.14 acres See Page 5 Q Discharge=C*I*A 0.11 cfs t Storm Duration 1 hr Solution: Vr Runoff Volume= Q*t 403 cf Vd Allow for 15%Sedimentation =Vr*1.15 464 cf F. FIND SEEPAGE BED PROPERTIES Given: H Height 5 ft Seepage Bed#3=5'x 8'x 27' W Width 8 ft L Length 27 ft Solution: Vb Bed (Rock)Volume= He*W*L 1,080 cf Vs Storage Volume=Vb*0.4 432 cf G. FIND VOLUME FROM INFILTRATION Given: As Area of bottom of infiltration window 216 sf r Infiltration Rate 2 in/hr Assumed t Duration 1 hr Solution: Vi Volume from Infiltration =As*(r/12)*t 36 cf H.CHECK AVAILABLE STORAGE> REQUIRED STORAGE(V) Given: Va Available Storage Volume(Vs+Vi) 468 cf Vd Required Volume 464 cf Check: Available> Required? YES P:\2014\14031\Documents\Drainage Report\RevA\5. Storm Calcs- 14031 ASPEN ENGINEERS APPENDIX A RUNOFF COEFFICIENTS AND RAINFALL INTENSITY P:\2014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc A.1 EXHIBIT"A" Recommended "C" Coefficients for"Rational Method Equation" Peak Rate of Discharge Description of Run-Off_Area 1 Runoff Coefficients"C" l Business Downtown areas 0.95 Urban neighborhood areas 0.70 Residential Single-family 0.50 Multi-family 0.75 Residential(rural) 0.40 Apartment dwelling areas 0.70 Industrial and Commercial Light areas 0.80 Heavy areas 0.90-4 USE 0.80 Parks,cemeteries 0.10 Playgrounds 0.20 Railroad yard areas 0.20 Unimproved areas 0.10 Streets Asphalt 0.95 Concrete 0.95 Brick 0.85 Drives and walks 0.85 Roofs 0.95 Fields: Sandy soil Flat 2% 0.05 Average 2-7% 0.10 Steep 7% 0.15 Fields: Clay soil Flat 2% 0.13 Average 2-7% 0.18 Steep 7% 0.25 Adapted from ASCE(1972 20,0 - I {No1j 1 1 I ' 1 15.0 a: reftecnIENCY ANALYSIS BY METHOD Of t0.0 - maw ammums imillall EXTREME VALUES, AFTER eltIMOrL =Ill ataNniangiliial. NM= z " aumumummumerameamm nummomme aue 0111 0 11111111111111111111111111 NEM 1111111111111111111111111111111 IIIC CC 6' amunummus mum Z 0 N E A IIIIIIII w 311111111111111111111111 a. 4.° 14:01111111 a I N T ENS IT Y-DUR ATION-FREQUENCY 1 ) ilit144111.111111111 =w illh. kihblibb. CURVE 111 111111 .0 Ilb- aml1i11e11a1111111r11111s1111111im11111u1111111%41.1.1s111111o1111111mM111111 1M1110 11 .. * ' 111111a111i1m1111u 11i1u11111i11m11111N11o1,•11111oio1n111 . •s1a111si111110ue2am / 11- ° a ••oe21111 11iNLC .., IIIIIIIIIIIIIIIIIIIIIIIIILR ).. nniiiniMMINDMIAL1 iiMMUinigi '-• 0., 11111111111111 11111115M11111111111111111111111110 1111111111111111•111.16MIMINiiiii wz 11111 I IIIIIIIMINIIIII I- 02 mg 111111111114Mil Mall LIMIIIIIIIMItMe =IIIIIMIIIIIIMHIIIIIIMmmmllIllIlliIllIllIllimmIMIIRNIIIIIIIIIIIIIMIIIIrqIIIigeMMM -"I 08 L alIMMUMOMMIIINUOIN ........111 .11111111......._11111.11111EililinikagiiMAN a aIIuIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIINIRIIIIIIIIIIIIIIIIIIWIIIINV; tk. D6 MUIIMIMIIIIIIIUIIIIIIIIINIIIIIIIIIIIIIIIIIIINIIIIIIIIIIIIIIIIIIIIIIIIIIIIIENIINZ' z ainialiMINIMMUMMINEIIMIMMIUMECE MIIIIIIIIIIIIIIIIIIIIIIIINIIIIMIIIIIIIIIIIIIIIIIIII LI 11111111111111111111111111111111111111111111 II 1111111111111111111111111111111111111 .2.5 10 15 20 30 40 so eo MI NU TE 3 2 3 4 5 6 a 10 12 IS 24 HOURS OUR ATI ON ASPEN ENGINEERS APPENDIX B INFILTRATION RATE INFORMATION P:12014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc B.1 TABLE 3-INFILTRATION RATES SCS Group and Type Infiltration Rate (Inches Per Hour) A. Sand 8 A. Loamy Sand 2 B. Sandy Loam 1 B. Loam 0.5 C. Silt Loam 0.25* C. Sandy Clay Loam 0.15 D. Clay Loam&Silty Clay Loam <0.09 D. Clays <0.05 *Minimum rate, soils with lesser rates should not be considered as candidates for infiltration facilities. 8013.4 Sediment and Grease Traps Properly sized standard sediment and grease traps shall be installed upstream of infiltration facilities. 8013.5 Ground Water Elevations Groundwater elevation shall be established in accordance with Section 8010.5. If groundwater is encountered during construction of the facility at an elevation higher than that shown on the plans, the facility shall be re-designed to account for the higher elevation. Water quality testing may be required by the District, Idaho Department of Water Resources or Central District Health Department. 8014 PERCOLATION FACILITIES 8014.1 Design In general percolation facilities are designed to contain the design inflow without overtopping. The water is stored within the effective pore volume and percolates into the ground. Percolation facilities may be designed to contain the runoff from the design storm for a primary system if the facility has a positive outflow to a secondary system. If there is not a positive outflow to a secondary system, the percolation facility must be designed to accommodate the runoff from the design storm for Adopted: Res. 469 (7/13/94) 8000- 17 Revised: 7/19/95; 2/14/96; Res. 657 (8/28/02) ASPEN ENGINEERS APPENDIX C SAND/GREASE TRAP CUT SHEETS P:\2014\14031\Documents\Drainage Report\RevA\1.Storm Calculation Introduction.doc C.1 r I -I r r -i O A �v`Vi�i5attitti,\�`1114,immolakiv 0-41,14.4 W w Alt%%k`` ��I� ___c i"9. - ����,011141�14. o z �k�4 ��i ilkip I-- i J 1 L_ J O PLAN VIEW 0 0 1=111=�=III—11=11LID LID 11=111=111=-111=-111:7-_1 I1III=111-111—I11=111— % —II1=II—II1=1I1—I11II1—III—II1—III _ p II-I=III-II=11=I=T-III=1 III=1 1=I1I 1=1I E--r4 I111-111=111_ TI=1 1=W'1=111—I 1=11 111 r ii ALLOWED CONSTRUCTION JOINT- "' 0 ,////////f/ • INLET L. " ' •e ' EL IN—7 SOW ///////////// ®EL.B '/ /////// OUTLET BAFFLE WALL OUTLET EL. OUT® ° CO ,',/-INLET BAFFLE WALL FLOW !//////////I XX_ < (see calculations and plan for a" distance between baffles) a SECTION A-A NOTES LEGEND O DESIGN LOAD: AASHTO HS-25 HIGHWAY LOADING. © ALL REINFORCING STEEL SHALL BE GRADE 60. O MANHOLE FRAME AND COVER PER SD-617 (TYPICAL) © DETAILED DRAWING OF A PRECAST BOX OR A POURED IN PLACE BOX DESIGN MUST BE APPROVED BY THE 0 LOCATION AND FL ELEV. PER DESIGN ENGINEER PRIOR TO CONSTRUCTION. PLANS. (TYPICAL) © HEIGHT OF OUTLET BAFFLE WALL AND LENGTH OF INLET 30 H512" USE GRADE RINGS (TYPICAL) BAFFLE WALL DETERMINED BY TANK CAPACITY AND 12"<H 24" USE 24" DIA RCP RISER FLOW RATE. 24"<H 120" USE MANHOLE CONE & OE BEFORE THESE BOXES ARE USED THE APPLICATION 48" DIRISERS. MUST BE APPROVED BY THE ENGINEER. ® EL. IN > EL. B BY 1" MIN. OF MANHOLE FRAME, COLLAR AND COVER SHALL BE EL. OUT < EL. B BY 1" MIN. PER SD-616 AND SD-617. UNLESS OTHERWISE APPROVED BY © PROVIDE STEPS WHEN THE DISTANCE FROM ACHD TOP OF MANHOLE FRAME TO TOP OF BOX O WATERTIGHT SEAL EXCEEDS 24". ©PRECAST BOX MANUFACTURER SHALL MARK FLOW DIRECTION AND LABEL INLET OR OUTLET ON SIDE OF BOX ACHD 2010 Revisions IDAHO STANDARDS FOR PUBLIC WORKS STANDARD DRAWING CONSTRUCTION SAND AND GREASE TRAP No. (ACHD SUPPLEMENT) SD- 624