Loading...
HomeMy WebLinkAboutStormwater Design Report 07-21-20 STORMWATER DESIGN REPORT FOR: PALISADES CONDOMINIUM BOZEMAN, MT Prepared By: MADISON ENGINEERING Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 May 2020 Revised July 2020 STORMWATER DESIGN REPORT FOR: PALISADES CONDOMINIUM BOZEMAN, MT OttiT,�rilri NA N,q CIiR!5 G.• ' QUDCS -I KI-1c s;OfillNA`���� Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 May 2020 Revised July 2020 PALISADES CONDOMINIUM SITE PLAN 3354 WARBLER WAY, BOZEMAN, MT STORMWATER DESIGN REPORT A. Introduction The proposed development for the Palisades Condominium Site Plan will be constructed at 3354 Warbler Way in Bozeman, MT. The site development consists of 6 residential condominiums and associated infrastructure. The following references were used in the preparation of this report: a. COB Design Standards and Specifications Policy, 2004 (DSSP). Addendum #6 b. COB Modifications to Montana Public Works Standard Specifications (MPWSS) B. Stormwater Management The site is separate into 6 separate drainage basins. Stormwater from each proposed drainage basin was graded to flow into various curb inlets and/or curb cuts throughout the site. From the curb inlets, stormwater is directed into separate underground retention systems consisting of perforated corrugated metal pipe (CMP) which will be installed in pervious rock backfilled trenches. From the curb cuts, stormwater is directed into separate at-grade retention ponds with 4:1 side slopes. Infiltration rock will be installed in the bottom of these retention basins to allow for the stormwater to infiltrated into the ground between storm events. It should be noted that Basin B is unique in that the underground CMP system is split with a portion of the required volume in a 66' long chamber located between buildings B and C and the other balance of the required volume is in two parallel 86' long chambers located behind building E. Basin B includes the existing two 4-plexes in the southwest corner that drain to the proposed curb inlet area drain. The Basin B infiltration basins are connected by a 12" storm pipe. Stormwater run-off was calculated based on the Rational Method and the retention systems were sized per the City of Bozeman's design standards for a storm intensity of 10-year frequency and a 2-hour duration. A summary table of the retention systems is provided in Table 1. Table 1 Stormwater retention system summary Property Basin A Basin B Basin C Basin D Basin E Basin F Type of Typical at- Underground Underground Typical at- Typical at- Underground retention grade pond CMP (two CMP grade pond grade pond CMP system separate locations) Req'd vol. (cfl 760 1 2,234 334 137 205 498 Prop. vol. (cfl 769 2,283 364 172 220 499 Palisades Condominium Stormwater Design Report Page 1 of 2 C. Groundwater We have been monitoring the groundwater to determine the depth during peak groundwater. A monitoring well was installed and located where the proposed underground stormwater basin will be located. Between 5/8/30 and 7/22 weekly measurements have been taken and the results are shown in Appendix D. To date, the highest measured groundwater depth in the monitoring well is 4657.83. Once the water and sewer mains are installed it is anticipated ground water will drop which is historical observed after mains are installed. Basin B — CMP Infiltration Basin Elevations • Minimum finish grade over basin 4763.0 • Top of porous stone(6") 4761.5 • Top of CMP 4761.0 • Invert of CMP (30") 4658.5 • Bottom of porous stone (6") 4758.0 • High Groundwater 4657.8 Basin C —CMP Infiltration Basin Elevations • Minimum finish grade over basin 4764.5 • Top of porous stone(6") 4763.2 • Top of CMP 4762.2 • Invert of CMP (24") 4660.2 • Bottom of porous stone (6") 4759.7 • High Groundwater 4657.8 Basin F —CMP Infiltration Basin Elevations • Minimum finish grade over basin 4763.0 • Top of porous stone(6") 4761.5 • Top of CMP 4761.0 • Invert of CMP (30") 4658.5 • Bottom of porous stone (6") 4758.0 • High Groundwater 4657.8 Appendices A. Stormwater basin calculations B. Stormwater Maintenance Plan C. Drainage Exhibit D. Groundwater Monitoring Summary E. Pipe Capacity Calculation Palisades Condominium Stormwater Design Report Page 2 of 2 Appendix Appendix A: Stormwater basin calculations Palisades Condominium 7/21/2020 Basin A Bldg A& 1/2 of Bldg B Roofs, & Driveways and Drive Lane Stormwater Run Off& Retention Basin Calculations Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations C Areas (ft): open space 7,470 0.20 Roof Area 5,314 0.90 Impervious 5,559 0.90 Total: 18,343 composite C: 0.61 Retention Pond Calculations: Q = CIA C = 0.61 (post-development) 1 = 0.41 in/hr(10-yr, 2-hr storm) A= 0.42 acres Q = 0.11 cfs required retention storage(ft3)= 760 ff' Volume held between contours: Cumulative Contour Area (ft ) Delta V(ft) Volume (ft) 4660.50 123 4661.00 369 123 123 4661.50 640 252 375 4662.00 936 394 769 Design storage at 1.5'depth (ft) = 769 A- Bldg A& B- Roofs and Driveway Retention Basin Calc 07-21-20.xls Palisades Condominium 4/29/2020 Basin B Revised 07-21-20 Bldg C&D-3 Plex Driveways&Drivelane&1/2 of Bldg B roof PLUS Ext'g 4-plexes and driveways Stormwater Run Off&Retention Basin Calculations Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations C Areas(ft): open space 12,807 0.20 Roof Area 10.051 0.90 Impervious 23,918 0.90 Total: 46,776 composite C: 0.71 Retention Pond Calculations: Q=CIA C= 0.71 (post-development) 1 = 0.41 in/hr(10-yr,2-hr storm) A= 1.07 acres Q= 0.31 cfs required retention storage(ft)= 2,234 ft' Contech Corrugated CMP Pipe Storage Calculations Pipe Area A=3.14xR`' Diameter Radius 2.5 1.25 3.14 = 4.91 ft Pipe Volume A=3.14xR2 Diameter Radius 2.5 1.25 3.14 = 4.91 ft2 Length(3-rows @ 65'each) = 238 ft Volume Stone Volume Stone Width = 4.75 ft Stone Depth = 3.5 ft Area = 16.625 ft2 Less Pipe Area = 4.91 ft2 Stone Area = 11.72 ft2 Pipe Length = 238 ft Storage Volume in Stone(40%voids) = 1,118 ft' Total Storage Volume = 1 2,283 ft' B-Bldg C&D-Driveway Retention Basin Calc 07-21-20.xls Palisades Condominium 4/29/2020 Basin C Revised 07-21-20 Bldg C&D-3 Plex Roofs Stormwater Run Off&Retention Basin Calculations Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations C Areas(ft): open space 0.20 Roof Area 5.511 0.90 Impervious 0.90 Total: 5511 composite C: 0.90 Retention Pond Calculations: Q=CIA C= 0.90 (post-development) 1= 0.41 in/hr(10-yr, 2-hr storm) A= 0.13 acres Q= 0.05 cfs required retention storage(ft3)= 334 ft3 Contech Corrugated CMP Pipe Storage Calculations Pipe Area A=3.14 x R` Diameter Radius 1 1 3.14 = 3.14 ft` Pipe Volume A=3.14xR2 Diameter Radius 2 1 3.14 = 3.14 ft2 Length(1-row @ 44'long) = 44 It Volume = 138 ft, Stone Volume Stone Width = 4 ft Stone Depth = 4 ft Area = 16 ft2 Less Pipe Area = 3.14 ft2 Stone Area = 12.86 ft2 Pipe Length = 44 It Storage Volume in Stone(40%voids) = F226 ft3 Total Storage Volume = 364 ft' C-Bldg C&D-Roofs Infiltration Retention Basin Calc 07-21-20.xis Palisades Condominium 4/29/2020 Basin D East Driveway Stormwater Run Off& Retention Basin Calculations Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations C Areas (ft): open space 1,432 0.20 Roof Area 0.90 Impervious 1,940 0.90 Total: 3,372 composite C: 0.60 Retention Pond Calculations: Q =CIA C = 0.60 (post-development) 1 = 0.41 in/hr(10-yr, 2-hr storm) A= 0.08 acres Q = 0.02 cfs required retention storage(ft3)= 137 ft3 Volume held between contours: Cumulative Contour Area (ft) Delta V(ft) Volume (ft) 4662.90 50 4663.4 156 52 52 4663.9 230 97 148 4664.0 257 24 172 Design storage at 1.1'depth (ft) = 172 D - East Driveway Retention Basin Calc 03-26-19.xls Palisades Condominium 4/29/2020 Basin E Bldg F-2 Plex& Driveway Stormwater Run Off& Retention Basin Calculations Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations C Areas (ft): open space 2,168 0.20 Roof Area 1,920 0.90 Impervious 985 0.90 Total: 5,073 composite C: 0.60 Retention Pond Calculations: Q = CIA C = 0.60 (post-development) 1 = 0.41 in/hr(10-yr, 2-hr storm) A= 0.12 acres Q = 0.03 cfs required retention storage(ft3)= 205 ft3 Volume held between contours: Cumulative Contour Area (ft) Delta V(ft) Volume(ft) 4662.80 10 4663.0 85 9 9 4663.5 204 72 82 4664.0 348 138 220 Design storage at 1.2'depth (ft)= 220 E- Bldg F-2 Plex Roof Retention Basin Calc 03-26-19.xls Palisades Condominium 4/29/2020 Basin F Revised 07-21-20 Bldg E-4 Plex Roof and Driveway Stormwater Run Off&Retention Basin Calculations Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 10 year IDF coefficient a 064 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations C Areas(ft): open space 3,686 0.20 Roof Area 3,774 0.90 Impervious 3,617 0.90 Total: 11,077 composite C: 0.67 Retention Pond Calculations: Q=CIA C= 0.67 (post-development) 1= 0.41 in/hr(10-yr,2-hr storm) A= 0.25 acres Q= 0.07 cfs required retention storage(ft')= 498 ft Contech Corrugated CMP Pipe Storage Calculations Pipe Area A=3.14xR` Diameter Radius 1.25 3.14 = 4.91 ft` Pipe Volume A=3.14xR2 Diameter Radius 2.5 1.25 3.14 = 4.91 ft2 Length(1-row @ 54'long) = 54 ft Volume = 265 ft' Stone Volume Stone Width = 4.5 ft Stone Depth = 3.5 ft Area = 15.75 ft2 Less Pipe Area = 4.91 ft2 Stone Area = 10.84 ft2 Pipe Length = 54 ft Storage Volume in Stone(40%voids) = r7 234 W Total Storage Volume = 499 ft' F-Bldg E-4 Plex Roof&Driveway Retention Basin Calc 07-21-20.xls Appendix B: Stormwater Maintenance Plan Detention Inspectionr • Underground stormwater detention and infiltration systems must Maintenance be inspected and maintained of regular intervals for purposes of CMP detention systems should be cleaned when on inspection reveals performance and longevity. accumulated sediment or trash is clogging the discharge orifice. Inspection Accumulated sediment and trash can typically be evacuated through Inspection is the key to effective maintenance of CMP detention the manhole over the outlet orifice. If maintenance is not performed systems and is easily performed. Contech recommends ongoing, as recommended,sediment and trash may accumulate in front of the annual inspections. Sites with high trash load or small outlet outlet orifice. Manhole covers should be securely sealed following control orifices may need more frequent inspections. The rate cleaning activities. Contech suggests that all syslems be designed with at which the system collects pollutants will depend more on- an access/inspection manhole situated at or near the inlet and the site specific activities rather than the size or configuration of the outlet orifice. Should it be necessary to get inside the system to perform maintenance activities,all appropriate precautions regarding confined system. space entry and OSHA regulations should be followed. Inspections should be performed more often in equipment Annual inspections are best practice for all underground systems. washdown areas, in climates where sanding and/or salting operations take place,and in other various instances in which During this inspection if evidence of salting/de-icing agents is observed within the system, it is best practice for the system to be rinsed, one would expect higher accumulations of sediment or abrasive/ including above the spring line soon after the spring thaw as part of the corrosive conditions.A record of each inspection is to be maintenance program for the system. maintained for the life of the system. Maintaining an underground detention or infiltration system is easiest when there is no flow entering the system. For this reason,it is a good idea to schedule the cleanout during dry weather. The foregoing inspection and maintenance efforts help ensure underground pipe systems used for stormwater storage continue to function as intended by identifying recommended regular inspection and maintenance practices. Inspection and maintenance related to the structural integrity of the pipe or the soundness of pipe joint connections is beyond the scope of this guide. • 1' ow::G IN nia CA Lu >-oULD h7 co•sr.JED s;%rc;�AVTr<rouceno"s w�icEsrD Haan_ CMP DETENTION SYSTEMS IJ_J:`SC�IREp ONL'r;O I,ELV kEl.D ECS v.YE iHtlK O','J.V E\'AIUATIDNS A`:D D`CISIO\',,;.,NCI«�E rJ_ITH`4 G'_I*�.NTEES 14OP'1:=RW`l'ICS OF SUJAIII_IT7 FOR 1-34"A ULICATION CC)NTECH/.1-1'Ec I,1J 44ti<t:Tt W-WSOEVEZ REi STED TG TW A°NIICaT10. 5 WJEI JAL,COATINGS,M P:ODJCV DiSC,M:D I I:f.EIN r'.I I V.=11�D 1'.A224!'rIEi Cti 1.1FRCI'hN'4BI_Il l SNI ALL 1','LIi D N'A':i=:lIIFS O"Ill:_= C",1•NTECH• FO2A`,PPUICUTA¢V,)kFD,_AAE D15CC+:I.MEG BY CCNTECH SEE CONTECH'S CO"DITill"N CF Sl_C 4 ('M;.i51F AT V-.,YJCOI IILCH,-' roe MOO c.ro�anov ENGINEERED SOLUTIONS C 2319COUT_,HE.N';INEET:DS:JLLITIONi ILC A(]U10ET_CO%I'Asn C_M1 kNTEII>N'__:S'..IJ=IJ%17'D" AIL 21G�TS?ESEWFJ F4INT_n 1%UjA PALISADE CONDOMINIUMS Storm Water Facilities Maintenance Plan Project Name File No. 19461 Owner's responsibility for routine inspection and maintenance 1. Keep the curb inlets, area drains and pipes free of leaves, rocks, and other debris. 2. Re-sod damaged or maintained areas immediately, or use grass plugs from the adjacent up-slope area. 3 Quarterly inspect and clean curb inlets, area drains and pipes. 4. Remove sediment from curb inlets sump by hand during the summer months whenever sediment has accumulated to greater than 3"in the bottom of the basin. 7. See that litter and other debris are removed from grates in order to reduce obstruction of flow. 8. The Contech CMP retention/infiltration system to be inspected quarterly and maintained per the attached Contech CMP Detention Inspection and Maintenance Guide. 9. Stormwater facilities shall be maintained by the owner or other responsible parry in a condition so that the facilities will function as designed. 10. Waste shall be disposed of from maintenance of facilities in accordance with applicable federal, state and local laws and regulations. 11. The owner or other responsible party shall create and maintain records of installation and maintenance and repair for the life of the development and shall be made available to the engineering department upon request. 12. Owner to maintain and fund Operation and Maintenance of facilities. aw Pali sad ondominium G:\MADISON ENGINEERING\PROJECTS\2018\18-122 Pallisades Condominium\Storm\Stormwater Maintenance Plan-Palisade 03-15-20.doc Appendix C: Drainage Exhibit UT A.- �T4 ul u G G- BASIN C UNDERGROUND7G 0 PG UP UE-G BASIN• A - 6:— U�p J�f u UJW7-7T7uj�p BASIN B UNDERGROUND Hp �ETENTION INFILTRATION SYSTEM BASIN D`— INFILTRATION SYSTEM (1 ) t--- POND r- _7 HLIENIIUN POND�' - - - - - - BASIN D r. SCALE �hl Vi r. l inch= 300f� BLDG C BLM D JR -17up BLDG C BLDGB BASIN C BASIN C BASIN A BLDGA L BASIN E RETENTION POND :3 BASIN B CURB INLET ww CURB INLET BASIN F UNDERGROUND I / /sus "' '> \ \ INFILTRATION SYSTEM BASIN E D '4!' • BASIN B UNDERGROUND \\ J BLDGF INFILTRATION SYSTEM (2) 100 BLDGia , BASIN F 10 ' BASIN B �o "r. EXrG 4-PLEX 00,400 %*o kx E =G 4-PLM 100 113- OW-00 00-00 PALISADES CONDOMINIUM SDI.0 STORM MADISON ENGINEERING WATER DRAINAGE EXHIBIT DRAWN BY: TDS 895 TECHNOLOGY BLVD,STE 203,BOMIAN,MT 59718 POST-DEV. DRAINAGE AREA DELINEATION PHONE(406)58"262 PROJECT h�.DATE: 7-21-20 V. 100 18-122 BOZEMAN,MT Appendix D: Groundwater Monitoring Summary Palisade Condominium Groundwater Monitoring Summary Top of Pipe Top of Casing Grnd Elevation Monitoring Elevation to Ground (ft) @ Pipe Base Date Measured GW GW Depth 4665.87 2.80 4663.07 5/8/2020 8.04 4657.83 5.24 4665.87 2.80 4663.07 5/15/2020 8.11 4657.76 5.31 4665.87 2.80 4663.07 5/23/2020 8.31 4657.56 5.51 4665.87 2.80 4663.07 5/27/2020 8.34 4657.53 5.54 4665.87 2.80 4663.07 6.5/20 8.70 4657.17 5.90 4665.87 2.80 4663.07 6.15/20 8.59 4657.28 5.79 4665.87 2.80 4663.07 6.26/20 8.42 4657.45 5.62 4665.87 2.80 4663.07 7./3/20 8.38 4657.49 5.58 4665.87 2.80 4663.07 7/13/2020 8.87 4657.00 6.07 4665.87 2.80 4663.07 22-Jul 9.02 4656.85 6.22 Appendix E: Pipe Capacity Calculation Palisades Condominium 7/21/2020 Basin B Bldg C & D -3 Plex Driveways& Drivelane& 1/2 of Bldg B roof PLUS Ext'g 4-plexes and driveways 25 year Stormwater Run Off Calculation Calculation of Required Volume for Storm Retention Pond Design Rainfall Freq. 25 year IDF coefficient a 0.78 IDF coefficient b IDF coefficient n 0.64 Post-development Calculations C Areas (ft): Landscaped 12,807 0.20 Roof Area 10,051 0.90 Impervious 23,918 0.90 Total: 46,776 composite C: 0.71 Retention Pond Calculations: Q = CIA C= 0.71 (post-development) 1 = 2.26 in/hr(25-yr, 2-hr storm) A= 1.07 acres Q= 1.72 cfs B- Bldg C & D-25 year Stromwater Runoff Calc 07-21-20.xls Pipe#1 8"SD Pipe-Bssin B Curb Inlet to Basin i Manning's Eqn. Q= 1.486 A Ry'S'n n Diameter,do(i 12.0 Enter Value Diameter,do(f 1.00 THETA Units= 1.486 _) n= 0.013 Slope,S(ft/ft) 0.006 Basin B-25 Year Storm Event-0.30 cfs Wetted Hyaraunc Hydraulic ecion Lnergy, Perimeter,P Radius,R Top Width, Depth,D Factor,Z Q(gpd-8 =V2/2g Depth,y(ft) Theta(rad) Area,A(ft2) (ft) (ft) T(ft) (ft) (ft s'Z) Q(cfs) Q(gpm) hour day) V(ft/s) (ft) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 00 0.0 0.0 0.00 0.05 0.90 0.01 0.45 0.03 0.44 0.03 0.00 0.01 5.4 2606.2 0.8 0.01 0.10 1.29 0.04 0.64 0.06 0.60 0.07 0.01 0.05 23.6 11330.7 1.3 0.03 0.15 1.59 0.07 0.80 0.09 0.71 0.10 0.02 0.12 55.0 26381.0 1.7 0.04 0.20 1.85 0.11 0.93 0.12 0.80 0.14 0.04 0.22 99.0 47526.2 2.0 0.06 0.25 2.09 0.15 1.05 0.15 0.87 0.18 0.06 0.36 154.9 74342.0 2.2 0.08 0.30 2.32 0.20 1.16 0.17 0.92 0.22 0.09 0.49 221.4 106280.3 2.5 0.10 0.35 2.53 0.24 1.27 0.19 0.95 0.26 0.12 0.66 297.3 142701.2 2.7 0.11 0.40 2.74 0.29 1.37 0.21 0.98 0.30 0.16 0.85 381.0 182888.0 2.9 0.13 0.45 2.94 0.34 1.47 0.23 0.99 0.34 0.20 1.05 471.0 226056.5 3.1 0.15 0.50 3.14 0.39 1.57 0.25 1.00 0.39 0.26 1.26 565.3 271357.0 3.2 0.16 0.55 3.34 0.44 1.67 0.26 0.99 0." 0.30 1.48 662.2 317873.6 3.3 0.17 0.60 3.54 0.49 1.77 0.28 0.98 0.50 0.35 1.69 759.E 364617.1 3.4 0.18 0.65 3.75 0.64 1.88 0.29 0.95 0.67 0.41 1.91 855.2 410513.5 3.6 0.19 0.70 3.96 0.59 1.98 0.30 0.92 0.64 0.47 2.11 946.6 454380.7 3.6 0.20 0.75 4.19 0.63 2.09 0.30 0.87 0.73 0.64 2.30 1031.0 494888.9 3.6 0.21 0.80 4.43 0.67 2.21 0.30 0.80 0.84 0.62 2.46 1105.2 530485.1 3.7 0.21 0.85 4.69 0.71 2.35 0.30 0.71 1.00 0.71 2.60 1165.1 559234.5 3.6 0.21 0.90 6.00 0.74 2.50 0.30 0.60 1.24 0.83 2.69 1205.0 578423.2 3.6 0.20 0.95 5.38 0.77 2.69 0.29 0.44 1.77 1.02 2.71 12149 583154.2 3.5 0.19 1.00 6.28 0.79 3.14 0.25 0.00 2.62 11310 542897.6 3.2 0.16 4.00 3.50 3,00 Oef 10, 2.50 i i -- .00 1.50 1.00 - 0.50 .' 000 0.00 0.20 0.40 0.60 0.80 1.00 1.20 Depth(ft)