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Home My WebLink AboutDrainage ReportW Aw THE LAND GROUP, INC. daPac Building Meridian, Idaho Storm Water Management Engineering Drainage Report Owner Engineer SNoI4 E The Land Group, Inc. ��5 �G\ST� Jason Densmer, PE 462 East Shore Drive 10g61 Eagle, Idaho 83616 Ph: 208.939.4041 Jr O6.03.15 OF ' \ N Dl N June 3, 2015 Project No. 114121 Site Planning Landscape Architecture - Civil Engineering - Golf Course Irrigation & Engineering - Graphic Design • Surveying 462 E. Shore Drive, Suite 100 Eagle, Idaho 83616 • P 208.939.4041 - F 208.939.4445 www.thelandgroupinc.com `rte L� ANNETHE LAND GROUP, INC. Site Description IdaPac Building Storm Water Management Engineering Drainage Report The project will construct an office building located at the northwest corner of the intersection of S. Spanish Sun Way and S. Linder Rd. in Meridian, Idaho. Peak Run -Off Rate & System Sizing On -Site Drainage System Description & Areas After development, the storm drainage from the site will sheet flow across the parking lots to catch basins. Roof drainage from each structure will be collected in underground pipes and routed to catch basins or other drainage structures. The site is divided into tributary areas, each with its own drainage system. An overview of the site is given in Appendix A. Collected flows will be treated by sand and grease traps prior to discharge into subsurface seepage beds below the parking lots. The seepage beds are designed to provide sufficient void space to accommodate the 100 -year storm event. After the storm, collected drainage will infiltrate from the seepage beds into the natural sub -soils. If the storm volume exceeds the design storm, excess collected storm water is provided with an emergency overflow to existing storm drain systems which take flows offsite. In this event, short-term ponding on the parking surfaces near inlets may occur. The calculations presented in this report show that the proposed facilities are adequately sized to accommodate the expected storm water runoff from the site. Developed Storm Volume The drainage systems have been designed to store the 100 -year, 1 -hour event. The drainage calculations are shown in Appendix B. or Site Planning • Landscape Architecture • Civil Engineering • Golf Course Irrigation & Engineering - Graphic Design , Surveying 462 E. Shore Drive, Suite 100 • Eagle, Idaho 83616 • P 208.939.4041 • F 208.939.4445 • www.thelandgroupinc.com THE LAND GROUP, INC. Appendix A Site Drainage Areas Exhibit 1— Post -Development Tributary Basins IdaPac Building Storm Water Management Drainage Report Site Planning - Landscape Architecture • Civil Engineering , Golf Course Irrigation & Engineering • Graphic Design - Surveying 462 E. Shore Drive, Suite 100 - Eagle, Idaho 83616 - P 208.939.4041 • F 208.939.4445 - www.thelandgroupinc.com 1 � 41p� ti � $1 RIM GVW -- - R/)R/W - Rl S Linder Rd — - M,ZI — - Tributary Basins HORIZONTAL SCALE: p' = 40' IdaPac Building Storm Water Management THE LAND GROUP, INC. Engineering Drainage Report Appendix B Drainage Calculations or Site Planning • Landscape Architecture - Civil Engineering - Golf Course Irrigation & Engineering • Graphic Design • Surveying 462 E. Shore Drive, Suite 100 • Eagle, Idaho 83616 • P 208.939.4041 • F 208.939.4445 • www.thelandgroupinc.com i— (based on Zone "A" OF Curve, 100 -yr Return Period) dollt 2,369 cf THE LAND GROUP. INC. 2,520 cf System OK (Excess Capacity) Drainage Area A Impervious Area = 32,444 sf Pervious Area = 0 sf EArea = 32,444 sf EArea = 0.74 acres C Coefficient = 0.95 Drainage System Characteristics - 2;20 1320 System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf InfTrench Width = 14.00 ft Inf Trench Length = 60.00 ft Inf Trench Depth = 7.50. ft Storage Volume of trench = 2520 cf Total Volume = 2,520 cf Infiltration Area = 840 sf Infiltration Rate = 560 cf/hr Drainage Calculations Basin Developed Volume Prepared By: J. Densmer Date: 06/03/2015 Project #: 114121 Storage Volume Required (100 -yr Storm) (based on Zone "A" OF Curve, 100 -yr Return Period) Maximum Runoff Developed = 2,369 cf Intensity 2,520 cf System OK (Excess Capacity) System Recovery Maximum Runoff = Time (min) Time (sec) (in/hr) Q dev. (cfs) V dev. (cf) V mf: (cTF Vs (cf) 10 600 ,3.11 - 2;20 1320 - 93 - 1,227 15 900 2.62 - 1 85 1 668 140 - 1 528 20 .._, 228 r,,... 161„ 1936 187 3, .,. 1749 30 .,.._. ... ............ 1800 .... 1.82 ....... - 1 29 ................ 2 318 280 2 038 40 ..... ,,,,,,,,, 2400 ...... ,,.,,.,1.37 ..... .,....... .. ..,,,,...... .. ........ ......... ........... 1953 .. .. ....... _.,,,, 50 ........ .,,. ,.,,,,,,,,_ 3 000 .,., 1.17 .....,,,.. .,..,.., 0.83 ,. ,,, 2 484 467 _ ....... ... ..... .. 2,017 60 ......... ......... ...... ........... 3,600 ............. 1.15 ........... 0.81 ;......... .,.........., 2,929 „.... ......... .,,;,,,....,,.. 560 ..........., 120 ,,,,,,,,,,,,, .................. .-... 7200 ._....... ...0„66 .,, ...... 047,........ 3362 - .,, ........ ,....1120 .,, ,,,,,,,,, 2242 .......... 0 . .........., ......... . .. ..18...... 10,800 .................... ,.,._0:48 i.......... 0.34 .............. 3 668 - . - 1 680 -,.......... d_.,..,., .. 1 988 .,........ 360 ,,,,,,,,,,,,,,,, .,,..... .... 21,600 ......... ............ 0.30 ,.,.,.... 021 4585,.,, 3,360 _,,,,.,,.,,,,,, 1225 .,......, .. ... .. 0.:19 ._,....... 0 13 ....... ...... o 5 808 ........ . .,.,,... 6,720 -, ... ... .,.,,........ .,... 0 _......... 1,440 _ 86,400 0.12 0.08 7,336 13,440 0 System Checks Maximum Runoff Developed = 2,369 cf Total Volume Provided = 2,520 cf System OK (Excess Capacity) System Recovery Maximum Runoff = 2,369 cf Other Sources = 0 cf Percolation Volume = 2,369 cf Recovery Time = 4.2 hours Recovery OK (<24 hrs) System Summary: 14.00 ft wide x 7.50 ft deep x 60.00 ft long D 150603 SDCalcs 114121.xlsx Drainage Calculations Basin Developed Volume Prepared By: J. Densmer Date: 06/03/2015 Project #: 114121 Storage Volume Required (100 -yr Storm) (based on Zone "A" IDF Curve, 100 -yr Return Period) 966 cf THE LAND GROUP, INC, Intensity Drainage Basin B Impervious Area = 13,286 sf Pervious Area = 0 sf EArea. = 13,286 sf IArea = 0.31 acres C Coefficient = 0.95 Drainage System Characteristics ........3.11 .......... System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 7.00 ft Inf Trench Length = 50.00 ft Inf Trench Depth = 7.00 ft Storage Volume of trench = 980 cf Total Volume = 980 cf Infiltration Area = 350 sf Infiltration Rate = 233 cf/hr Drainage Calculations Basin Developed Volume Prepared By: J. Densmer Date: 06/03/2015 Project #: 114121 Storage Volume Required (100 -yr Storm) (based on Zone "A" IDF Curve, 100 -yr Return Period) 966 cf Total Volume Provided = Intensity System Recovery Maximum Runoff = 966 cf Time (min) Time (sec) (in/hr) Q dev. (cfs) V dev. (cf) V inf. (cf) Vs (cf) ........... .. . 10,,, .......... 600 .......... ........3.11 .......... 090 .. ........... 541 39 502 ...15.....,....... 900 ......2,:62 ............. 076...........4 ........ 683 ..., „ , ......,...........................,,...,. 625 20 ..... .. ..... 1,200 2.28 ... 0.66 793 ......58 „„, 78 ........ 715 30,,,. ... ._ _ „ ..., 1 8001.82 ....... ................. 0 53 ....., ......._... 948,, .......... _,.,...... 117 ........,. 833 .... 40 ...........^ 2400 .... .,,,.._1.37 ........., 040.,........ ... 953 ... .,,. „ 156 ......., ......... 797 50.. 3000 1017 194 .. .......:. 823 ..._ ......... ........... .. .,,,.1.17 1034 ............... ....-_ �... ...... ...... „.. 60 3 600 .. 1.15 - .,, ..... 0 33 ......._ 1 200 .....,,,,._.. 120 7,200 - 0.66 0 19 - 1,377 ,233 _. 467 910 180 ... ..,.. 10 800 - ... ., 0.48 „ 0 14_ 1,502 700 . 802 360 .._ ... 21 600 ., 0.30 ._,..,... .., .... . 0 09 ...... 1 878 ... 1400 .........,. 478 720 .,... 43 200 ..... ,.. .0.19 „ ... 0 06 .......... 2 378 ........... o. ..... 2,800 _.........,. 0 1,440 1 86,400 _ 0.12 _ 0.03 3,004 .. 5,600 „ ...... 0 System Checks Maximum Runoff Developed = 966 cf Total Volume Provided = 980 cf System OK (Excess Capacity) System Recovery Maximum Runoff = 966 cf Other Sources = 0 cf Percolation Volume = 966 cf Recovery Time = 4.1 hours Recovery OK (<24 hrs) System Summary: 7.00 ftwide x 7.00 ft deep x 50.00 ft long D 150603 SDCalcs 114121.xlsx