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Home My WebLink AboutNORTHWEST ASPHALT V ?LW Northwest Asphalt Renton, Washington Storm Drainage Report Prepared For: Ty H. Ribera Construction, Inc. Prepared By: Pacific Engineering Design, Inc. November 6, 2000 PEDI Job No. 00040 CITY Or FIBITON RECEIVED NOV 0 7 2000 BUILDING DIV60N Storm Drainage Report Northwest Asphalt Renton, Washington Renton Project No. LUA00-115 Renton Permit No. B000485 November 6, 2000 Prepared For Ty H. Ribera Construction 13029 136th Avenue, SE Renton, WA 98059 (425) 430-1300 Prepared By Pacific Engineering Design, Inc. 4800 S. 188th Street, Suite 360 Seattle, Washington 98188 (206) 431-7970 I� t� Table of Contents Section 1 Project Overview................................................................ 2 Section 2 Site Analysis and Design.................................................... 3 Section 3 Conveyance System and ESC Analysis and Design.......... 4 Section 4 Drainage Calculations ........................................................ 5 Section 1: Project Overview In response to the City of Renton's comments, the grading plan has been revised and a stormwater facility has been designed. Per City of Renton regulations, the criteria used in the design of the storm drainage system were the 1990 King County Surface Water Design Manual. This permit application includes proposed grading as well as work that has already been completed. It is estimated that an area of 0.82 acres has already been filled. The owner proposes to fill an additional area of 1.45 acres. The total area of post-construction impervious surface is 3.23 acres (which includes 1.78 acres of existing impervious and assumes that the entire 1.45 of fill area will be impervious surface). The grading was revised in order to provide a buffer for the offsite wetland that exists adjacent to the southwest corner of the site. This wetland will be retained as part of the ongoing construction of the neighboring Maplewood Plat. Per the City of Renton, the buffer has been established at 37.5 feet. A wetlands biologist has designed a planting plan for this area. The proposed fill will be to the north and east of this area. The pond will be constructed in the new fill area. The bioswale will convey the outflow from the detention pond to its historical release point near the offsite wetland. To mitigate drainage impacts to the surrounding watershed from both the proposed and previous fills, a stormwater retention/detention pond will be constructed on the southern portion of the site. A biofiltration swale downstream of the pond will provide water quality treatment. This swale design will allow for sedimentation of the on-site stormwater runoff. The outflow control structure and live storage have been designed such that discharge from the pond will be limited to estimated pre-development levels. Discharge from the swale will outlet at the edge of the wetland buffer and flow downhill and offsite into the wetland itself. Section 2: Site Analysis and Design The property lies within the drainage basin of the lower Cedar River. The flow of surface water across the site is generally to the southwest. Immediately downstream of the site, stormwater runoff passes into a large offsite wetland (approximately 1 acre). This wetland will have a constructed outlet and will be incorporated into the drainage system of the neighboring plat of Maplewood Estates. As outflow from the wetland enters the storm drainage system, it will be conveyed into the storm drainage pond that is part of the new construction. Downstream flooding is not considered a major risk at this site. Flow leaving the site will be restricted to pre-existing levels and water quality treatment will be provided. This should minimize impact to the downstream area and the surrounding watershed. The large wetland area just downstream of the project site will provide storage volume for larger storm events. There are no anticipated backwater effects that could possibly impact offsite regions upstream of the subject property. Site hydrology has been analyzed using Waterworks software. The site area was analyzed as a single drainage basin. The pond and outflow control structure were sized to match the 2 and 10-year 24-hour storm events. The existing- et"conditions use in the analysis are the estimated site condi ' ns prior-to recent fill�hese nclude an existing impervious area of 1.78 acres. In this analysis,the remainder of the pre-existing site was assumed to be grassy. In calculating the post-development flows, it was assumed that all of the proposed fill area will be impervious surface. (See following Drainage calculations) The required water quality treatment for this site will be satisfied by the construction of a bioswale. All of the discharge from the detention pond will be routed through the bioswale before being released near the offsite wetland. 2 Section 3: Conveyance System and ESC Analysis and Design The placement of the detention pond and the site grading will serve to convey most of the site's stormwater runoff into the detention pond. This will provide water quality treatment of runoff from the on-site areas most likely to contain sediment or other pollutants. During construction, a temporary pond will serve as an erosion and sediment control pond to treat site runoff. On-site flows will be conveyed into the pond and retained, to allow sedimentation (see Erosion and Sediment Control calculations). The wetland adjacent to the southwestern corner of the property will be protected by a 37.5-foot buffer. Just outside of this buffer, silt fences will be installed along the southern and western edges of the property. These are intended to limit the transport of sediment from the site during construction activities. Constructed fill slopes will be vegetated in order to protect against erosion. The detention pond will provide a half-foot of dead storage depth. This volume will allow for some sedimentation of site runoff. As a further water quality protection, a bioswale will convey and treat discharge from the pond prior to its release. Outflow from the pond will be restricted by a FROP-T control structure located in a manhole adjacent to the pond. The manhole will provide access for maintenance to the control structure. There will be 4 feet of dead storage in the manhole below the outlet that will provide some volume for sediment. The control structure consists of a 12-inch diameter riser pipe equipped with 2 orifices to meter flow. The riser pipe connects to an outlet pipe that empties onto the bioswale. All of the pond discharge will pass through the control control structure and be released onto the bioswale. Outflow from the bioswale will be released on-site. Installation of a flow spreader and rock pad at this release point will disperse flow and prevent erosion. The bioswale has been designed per the KCSWDM and is intended to provide removal of suspended solids as well as biological uptake of pollutants (See the Swale Design calculations following this section). 4 Section 4: Drainage Calculations OAJ Al" ;s Ilk aj dr� CCT a w w�wi� w� 14 ✓ I N �A UR g SIR I ON4•a ��: - 4 lst € ,r ,¢� dk€ks.' ,, pp��, 'tr'R�'I �R�x.:Z.� _ - ___._.' ('�• g Ce I i��9"t€6R'�'dC9� 2:�[C i k�(M.d4 k(.F �a� aR tlCx'a ( i.i'� • l�tG A/Q�6/Yj 4 �l L k RIP ARw€RaWS"r un€RI16RGP�'" y� 4 OW Rtikka Arl Rpc on RaKIM .; n`€ '{, s,?" +� e�"ks. k €pz 4 4rr'4 "�R R�;:ck s4;ttfR„,€IkyR gel"air{ K� ,`RCu .d'� r i AsP�,.(t tit : 1061 off. PACIFIC ENdNEERINQ DESIGN INC. PHONE LOG ❑ CONFERENCE ❑ CIVIL ENGINEERING AND PLANNING CONSULTANTS MEMO ❑ INFO ❑ DISTRIBUTION: PROJECT t j2"Ji PROJECT NO. Q 66 41 INCOMING CALL ❑ DATE QTIME OUTGOING CALL ❑ PERSON +Gy t- h I Lk PHONE NO. Co FAX NO. FILE ❑ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I ta. • .. 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SIGNATURE 41300 S. 1 BBTH ST., SUITE 360, SEATTLE, WASHINGTON BB 1 BB 20B/431-797O FAX/431-7J75 10/5/00 9 : 38 : 50 am Pacific Engineering Design Inc page 1 NW ASPHALT DRAINAGE CALCULATIONS PED #00040 BASIN SUMMARY BASIN ID: EXIST002 NAME: EXISTING 2-YEAR STORM EVENT SCS METHODOLOGY TOTAL AREA. . . . . . . : 4 . 78 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 3 . 00 Acres 1. 78 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 85 . 00 98 . 00 TC. . . . : 29 . 78 min 29 . 78 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 0333 TcReach - Shallow L: 250 . 00 ks : 11. 00 s : 0 . 0320 TcReach - Shallow L: 30 . 00 ks : 5 . 00 s : 0 .2700 TcReach - Shallow L: 220 . 00 ks : 5 . 00 s : 0 . 0550 PEAK RATE: 1. 06 cfs VOL: 0 .45 Ac-ft TIME: 510 min BASIN ID: EXISTO10 NAME: EXISTING 10-YEAR STORM EVENT SCS METHODOLOGY TOTAL AREA. . . . . . . : 4 . 78 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 . 90 inches AREA. . : 3 . 00 Acres 1. 78 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 85 . 00 98 . 00 TC. . . . : 29 . 78 min 29 . 78 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 0333 TcReach - Shallow L: 250 . 00 ks : 11 . 00 s : 0 . 0320 TcReach - Shallow L: 30 . 00 ks : 5 . 00 s : 0 . 2700 TcReach - Shallow L: 220 . 00 ks : 5 . 00 s : 0 . 0550 PEAK RATE: 1. 86 cfs VOL: 0 . 75 Ac-ft TIME: 510 min 10/5/00 9 : 40 : 1 am Pacific Engineering Design Inc page 1 NW ASPHALT DRAINAGE CALCULATIONS PED #00040 --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: DEV002 NAME: DEVELOPED 2-YEAR STORM EVENT SCS METHODOLOGY TOTAL AREA. . . . . . . : 4 . 79 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 1. 55 Acres 3 . 24 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 0333 TcReach- Shallow L: 250 . 00 ks : 11. 00 s : 0 . 0320 TcReach - Shallow L: 30 . 00 ks : 5 . 00 s : 0 .2700 TcReach - Shallow L: 220 . 00 ks : 5 . 00 s : 0 . 0550 PEAK RATE: 1. 65 cfs VOL: 0 . 57 Ac-ft TIME: 500 min BASIN ID: DEV010 NAME: DEVELOPED 10-YEAR STORM EVENT SCS METHODOLOGY TOTAL AREA. . . . . . . : 4 . 79 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 . 90 inches AREA. . : 1. 55 Acres 3 . 24 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 0333 TcReach - Shallow L: 250 . 00 ks : 11. 00 s : 0 . 0320 TcReach - Shallow L: 30 . 00 ks :5 . 00 s : 0 . 2700 TcReach - Shallow L: 220 . 00 ks :5 . 00 s : 0 . 0550 PEAK RATE: 2 . 62 cfs VOL: 0 . 90 Ac-ft TIME: 490 min Cross Section Cross Section for Trapezoidal Channel Project Description Project File p:lsdsk\proj100040\flow master\bioswale.fm2 Worksheet Northwest Asphalt Bioswale Flow Element Trapezoidal Channel Method Manning's Formula Solve For Bottom Width Section Data Mannings Coefficient 0.350 Channel Slope 0.020000 ft/ft �QtJI<vZEQ �wPv� iC. 4 t' � PA►2C��/� 14 Depth 0.50 ft Left Side Slope 3.000000 H : V Right Side Slope 3.000000 H : V Bottom Width 8.20 ft EVE`e Discharge 1.65 cfs 3 0.50 ft J 1 8.20 ft V H 1 NTS 17 / 10/09/00 FlowMaster v5.13 01:36:36 PM Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06708 (203)755-1666 Page 1 of 1 Northwest Asphalt Bioswale Worksheet for Trapezoidal Channel Project Description Project File p:\sdsk\proj\00040\flow master\bioswale.fm2 Worksheet Northwest Asphalt Bioswale Flow Element Trapezoidal Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.030 Channel Slope 0.022500 ft/ft Left Side Slope 3.000000 H : V Right Side Slope 3.000000 H : V Bottom Width 8.00 ft Discharge 4.00 cfs iQ q c 6 flA96-5- 15 Results ..r Depth 0.20 ft ¢ V151- ^. 5=tv Flow Area 1.68 ftZ ' Wetted Perimeter 9.24 ft Top Width 9.17 ft Critical Depth 0.19 ft Critical Slope 0.023395 ft/ft Velocity 2.38 ft/s Velocity Head 0.09 ft Specific Energy 0.28 ft Froude Number 0.98 Flow is subcritical. 'rH t5 Stt�>�; �q��-• -r=-�� DES t g ill ru Aew Ca at✓E Y Tff� f D� - 1'E'rg .�T� � . 10/10/00 FlowMaster v5.13 10:43:30 AM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203)755-1666 Page 1 of 1 1019100 3 : 24 : 14 pm Pacific Engineering Design Inc page 2 NW ASPHALT DRAINAGE CALCULATIONS PED #00040 --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE STORAGE TABLE CUSTOM STORAGE ID No. DES VOL Description: -T= � STORAGE IN DESIGN POND STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> (ft) ---cf--- --AC-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- 446.50 0.0000 0.0000 447.40 734.95 0.0169 448.30 2023 0.0464 449.20 3973 0.0912 446.60 61.950 0.0014 447.50 841.25 0.0193 448.40 2239 0.0514 449.30 4189 0.0962 446.70 123.90 0.0028 447.60 947.55 0.0218 448.50 2456 0.0564 449.40 4406 0.1011 446.80 185.85 0.0043 447.70 1054 0.0242 448.60 2673 0.0614 449.50 4623 0.1061 446.90 247.80 0.0057 447.80 1160 0.0266 448.70 2889 0.0663 449.60 4839 0.1111 447.00 309.75 0.0071 447.90 1266 0.0291 448.80 3106 0.0713 449.70 5056 0.1161 447.10 416.05 0.0096 448.00 1373 0.0315 448.90 3323 0.0763 449.80 5272 0.1210 447.20 522.35 0.0120 448.10 1589 0.0365 449.00 3539 0.0813 449.90 5489 0.1260 447.30 628.65 0.0144 448.20 1806 0.0415 449.10 3756 0.0862 450.00 5706 0.1310 ,STo(LA-6-9;- VaL,L)M6�- tjL) vo �oTira j.A 5 Ev. 10/9/00 3 : 24 : 14 pm Pacific Engineering Design Inc page 1 NW ASPHALT DRAINAGE CALCULATIONS PED #00040 STAGE STORAGE TABLE CUSTOM STORAGE ID No. DES_LIVE Description: LIVE STORAGE IN DESIGN POND STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STORAGE----> (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --AC-Ft- (ft) ---cf--- --Ac-Ft- 447.00 0.0000 0.0000 447.80 850.40 0.0195 448.60 2363 0.0542 449.40 4096 0.0940 447.10 106.30 0.0024 447.90 956.70 0.0220 448.70 2580 0.0592 449.50 4313 0.0990 447.20 212.60 0.0049 448.00 1063 0.0244 448.80 2796 0.0642 449.60 4529 0.1040 447.30 318.90 0.0073 448.10 1280 0.0294 448.90 3013 0.0692 449.70 4746 0.1090 447.40 425.20 0.0098 448.20 1496 0.0344 449.00 3230 0.0741 449.80 4963 0.1139 447.50 531.50 0.0122 448.30 1713 0.0393 449.10 3446 0.0791 449.90 5179 0.1189 447.60 637.80 0.0146 448.40 1930 0.0443 449.20 3663 0.0841 450.00 5396 0.1239 447.70 744.10 0.0171 448.50 2146 0.0493 449.30 3879 0.0891 10/9/00 3 : 23 : 39 pm Pacific Engineering Design Inc page 1 NW ASPHALT DRAINAGE CALCULATIONS PED #00040 --------------------------------------------------------------------- --------------------------------------------------------------------- DISCHARGE STRUCTURE LIST MULTIPLE ORIFICE ID No. HOLE Description: ORIFICES FOR OUTFLOW CONTROL Outlet Elev: 447 . 00 Elev: 445 . 00 ft Orifice Diameter: 5 . 7891 in. Elev: 448 . 50 ft Orifice 2 Diameter: 5 .4844 in. COMBINATION DISCHARGE ID No. OUTLET Description: OUTFLOW CONTROL STRUCTURE Structure: HOLE Structure: Structure: RISER Structure: Structure: RISER DISCHARGE ID No. RISER Description: 12" DIAMETER RISER PIPE Riser Diameter (in) : 12 . 00 elev: 449 . 00 ft Weir Coefficient. . . : 9 . 739 height : 450 . 00 ft Orif Coefficient. . . : 3 . 782 increm: 0 . 10 ft 1019100 3 : 24 : 32 pm Pacific Engineering Design Inc page 1 NW ASPHALT DRAINAGE CALCULATIONS PED #00040 LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAK-> OUTFLOW STORAGE <--------DESCRIPTION---------> (cfs) (cfs) --id- --id- <-STAGE> id (cfs) VOL (cf) MATCH 2-YEAR STORM ........... 1.06 1.65 DES LIVE OUTLET 448.29 1 1.03 1689.01 cf MATCH 10-YEAR STORM .......... 1.86 2.62 DES LIVE OUTLET 448.91 2 1.18 3043.22 cf PACIFIC ENaINEERIN® ®ESK3N INC. 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