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HomeMy WebLinkAboutSWP272320 i ' � i/� • CONCEPT ENGINEERING, INC. 455 Rainier Boulevard North,Suite 200 Issaquah, Washington 98027 ' (206)392-8055 Fax: (206)392-0108 DRAINAGE CALCULATIONS FOR ' U.S. RENTALS ' CITY OF RENTON, WASHINGTON ' Prepared for: Treece & Company 320 2nd Ave. South, Suite 200 Kirkland, WA 98033 Phone: (206) 822-2577 ' FAX: (206) 822-8758 By: 00 33808 �++� �QrsTEItt �rA ONAL UPIRE4 4-4- a Kirk R. Smith, P.E. April 11, 1997 REVISED June 20, 1997 �`"4� � CIVIL ENGINEERING/SURVEYING/LAND USE PLANNING TABLE OF CONTENTS ' Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Summary of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Basin Summaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Runoff Curve Number and Time of Concentration . . . . . . . . . . . . . . . . . . . . . 8 Detention Pond Design Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 ' Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Backwater Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 ' Drainage Area Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 INTRODUCTION ' The following design report presents the design of the stormwater control facilities for the proposed 4.17 acre U.S. Rentals site at the intersection of Lind Ave. and SW 34th St. Existing Drainage Conditions ' The project site is currently a vacant parcel (Lot 8 of Burlington Northern Binding Site Plan). The parcel was filled approximately 18 years ago. The existing ground cover ' consists of mainly pasture grass in poor condition. The site is extremely flat with several shallow depressions. A 30 foot wide railroad easement borders the east side of the site. This railroad line has ditches on either side of the tracks which collect runoff from a portion of the site. The general overall slope is from east to west at an average slope of 0.2 percent. ' The site has two storm drainage stubs available, one on each frontage road. However, neither is currently receiving runoff from the site. The east and south sides of the site have been or are under development and will intercept any surface flow from upstream areas. Proposed Drainage Conditions Runoff from parking, equipment and material storage, landscaping and roof areas will 9 9 P 9 be conveyed via sheet flow to perimeter biofiltration swales. These perimeter swales ' convey the treated water to a combination detention/water quality pond located in the southern portion of the site. This pond will have 2-3 feet of dead storage to enhance ' water quality through settling of sediments prior to discharge from the site. A multi-orifice flow control structure is provided at the outlet from the pond. Post- detention peak outflows will be at or below the pre-developed peak runoff rates for the 2, 10 and 100 year storm events. The control structure outlet is connected to a 12 inch storm drainage stub near the midpoint of the west property line along Lind Avenue. This stubs connects with a 60 inch storm drain pipe along the west side of Lind Avenue. The 60 inch continues north to the Lind-SW 34th St. intersection and then turns west and continues down SW 34th St for approximately 1/4 mile until ' reaching Springbrook Creek. Per discussions with Scott Woodbury of the City of Renton, a tailwater condition from Springbrook Creek exists in the 60-inch culvert during storm events. Mr. Woodbury said that development projects in the area have been required to base their conveyance analyses on a 2-year tailwater elevation of 14.6 (NAVD 88). Converted ' to the vertical datum used in the site plans for this project, the tailwater elevation is 11 .26 feet. This tailwater was used in the backwater analysis for this project. ' -1- Core and Special Requirements Following is a description of how the 1990 King County Surface Water Design Manual core and special requirements were addressed in this design. ' CORE REQUIREMENT #1 - Discharge at the natural location: As described above, two drainage stubs have been provided to the site; both connect ' to a 60-inch system leading to Springbrook Creek. The proposed system will connect to the stub in Lind Ave. ' CORE REQUIREMENT #2 - Off-site analysis: The upstream and downstream systems are described above. CORE REQUIREMENT #3 - Runoff control: A stormwater detention pond will control runoff from the developed site and release at the existing condition peak runoff rates for the 2, 10, and 100-year, 24-hour storm events. Designing the system to the 100-year event resulted in a storage volume of 11 ,738 cubic feet, which is greater than the 10,201 cubic feet that would have been provided if the system had been designed to the 10-year storm with a 30% factor of safety added. Biofiltration swales have been provided as required. CORE REQUIREMENT #4 - Conveyance system: ' A uniform flow conveyance analysis has been provided for the proposed swales. A backwater conveyance analysis was performed for the proposed pipes. CORE REQUIREMENT #5 - Temporary erosion and sedimentation control plan: A TESC plan has been prepared consisting of construction sequence, gravel construction entrance, perimeter silt fencing, and a sediment pond. ' SPECIAL REQUIREMENT #5 - Special Water Quality Controls: A water quality pond (wetpond) has been provided since the proposed site plan ' contains more than 1 acre of impervious surfaces subject to vehicular use or the storage of chemicals. ' -2- SUMMARY OF RESULTS PROPOSED DETENTION SYSTEM ' Total Area of Project Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.17 acres ' Post-Devel- Post- Design Detention Design Pre-Developed oped Pond Developed Water Storage Peak Discharge Release Surface Storm (cfs) Inflow Rate Elevation Volume (cfs) (cfs) (ft) Icf► W.Q. NA 0.45 0.26 13.53 243 2 0.45 1 .76 0.44 14.06 4575 ' 10 0.91 2.68 0.89 14.44 7847 ' 100 1 .47 3.69 1 .29 14.86 11747 ' -3- ' BASIN SUMMARIES 1 1 1 1 � 1 1 2 97 1:22 :34 m Treece & Company / / P P Y US Rentals - Lind Ave. & SW 34th St. ' SBUH Hydrograph Analysis Preliminary R/D Sizing ------------------------------------------------- BASIN SUMMARY BASIN ID: DEV-002 NAME: POST-DEV 2-YEAR 24-HR STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 1.95 inches AREA. . : 0.42 Acres 3.75 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00 ' TC. . . . : 10.00 min 10.00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 1.76 cfs VOL: 0.58 Ac-ft TIME: 480 min BASIN ID: DEV-002W NAME: POST-DEV WATER QUALITY STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP ' PRECIPITATION. . . . : 0.65 inches AREA. . : 0.42 Acres 3.75 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00 TC. . . . . 10.00 min 10.00 min ABSTRACTION COEFF: 0.20 ' PEAK RATE: 0.44 cfs VOL: 0.15 Ac-ft TIME: 480 min BASIN ID: DEV-010 NAME: POST-DEV 10-YEAR 24-HR STORM SBUH METHODOLOGY ' TOTAL AREA. . . . . . . : 4.17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 .85 inches AREA. . : 0.42 Acres 3.75 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00 TC. . . . : 10.00 min 10.00 min ' ABSTRACTION COEFF: 0.20 PEAK RATE: 2.67 cfs VOL: 0.88 Ac-ft TIME: 480 min BASIN ID: DEV-100 NAME: POST-DEV 100-YEAR 24-HR STORM ' SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4.17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3.85 inches AREA. . : 0.42 Acres 3.75 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 90.00 98.00 TC. . . . : 10.00 min 10.00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 3 .69 cfs VOL: 1.23 Ac-ft TIME: 480 min ' -5- 1/2/97 1:22:34 pm Treece & Company US Rentals - Lind Ave. & SW 34th St. aph ' SBUHiminary R/D Analysis Preliminary R/D Sizing BASIN SUMMARY ' BASIN ID: EX-002 NAME: PRE-DEV 2-YEAR 24-HOUR STORM SBUH METHODOLOGY ' TOTAL AREA. . . . . . . : 4.17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 1.95 inches AREA. . : 4.17 Acres 0.00 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 88 .00 0.00 ' TC. . . . : 60.00 min 0.00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 0.44 cfs VOL: 0.32 Ac-ft TIME: 490 min ' BASIN ID: EX-010 NAME: PRE-DEV 10-YEAR 24-HOUR STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2.85 inches AREA. . : 4.17 Acres 0.00 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 88.00 0.00 TC. . . . : 60.00 min 0.00 min ABSTRACTION COEFF: 0.20 ' PEAK RATE: 0.91 cfs VOL: 0.59 Ac-ft TIME: 490 min BASIN ID: EX-100 NAME: PRE-DEV 100-YEAR 24-HOUR STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .17 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3.85 inches AREA. . : 4.17 Acres 0.00 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 88.00 0.00 TC. . . . : 60.00 min 0.00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 1.47 cfs VOL: 0.90 Ac-ft TIME: 490 min ' 1/2/97 1:22:34 pm Treece & Company US Rentals - Lind Ave. & SW 34th St. SBUH Hydrograph Analysis Preliminary R/D Sizing ------------------------ HYDROGRAPH SUMMARY 1 ' PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf\AcFt Acres 1 0.445 490 14004 cf 4 .17 2 0.909 490 25513 cf 4.17 3 1.470 490 39205 cf 4 .17 ' 4 1 .761 480 25082 cf 4 .17 5 2 .675 480 38466 cf 4.17 6 3.685 480 53450 cf 4.17 7 0.445 480 6393 cf 4 .17 14 0.442 550 25082 cf 4.17 15 0.891 540 38491 cf 4.17 16 1.289 530 53453 cf 4 .17 17 0.259 510 6394 cf 4 .17 ' RUNOFF CURVE NUMBER TIME OF CONCENTRATION 1 1 1 1 CURVE NUMBER SELECTION The fill soil was assumed to correspond to hydrologic soil group C. A Curve Number (CN) value of 88 was used for the pre-developed conditions. This was determined by taking an average of the "fair" and "good" conditions for open space and lawns. A CN value of 90 was chosen for the pervious areas in the post-developed condition. TIME OF CONCENTRATION A conservative time of concentration of 60 minutes was used for the pre-developed conditions. Due to the extremely flat topography with several small depressions, a typical calculation with a friction coefficient and slope is not appropriate. A post-developed T,, of 10 minutes has been used. The actual calculated T,,'s for the east and west swale basin are slightly more than 10 minutes, thus the analysis predicts more conservative peak runoff rates and volumes for the post-developed condition. 1 i 1 1 1 1 -9 1 ' DETENTION BASIN DESIGN DATA ' -10- 6/20/97 11 : 27 : 15 am Concept Engineering page 1 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing STAGE STORAGE TABLE ' TRAPEZOIDAL BASIN ID No . SP-1 Description: DETENTION STORAGE POND Length: 155 . 00 ft . Width: 50 . 00 ft . ' Side Slope 1 : 3 Side Slope 3 : 3 Side Slope 2 : 3 Side Slope 4 : 3 Infiltration Rate : 0 . 00 min/inch ' STAGE <----STORAGE----> STAGE ;----STORAGE------- STAGE <----STORAGE----> STAGE <----STORAGE----> (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- ------------------------------ 13.50 0.0000 0.0000 13.90 3199 0.0734 14.30 6600 0.1515 14.70 10206 0.2343 13.60 781.16 0.0179 14.00 4030 0.0925 14.40 7482 0.1718 14.80 11141 0.2558 13.70 1575 0.0362 14.10 4874 0.1119 14.50 8377 0.1923 14.90 12088 0.2775 13.80 2381 0.0547 14.20 5730 0.1316 14.60 9285 0.2132 15.00 13049 0.2996 IZ 6/20/97 11 : 20 :48 am Concept Engineering page 2 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing STAGE DISCHARGE TABLE ' COMBINATION DISCHARGE ID No. DC-1 Description: COMBO DISCHARGE #1 ' Structure : DO-1 Structure : Structure : DNW-1 Structure : Structure : STAGE c--DISCHARGE---> STAGE <--DISCHARGE---> STAGE -DISCHARGE---> STAGE <--DISCHARGE---> t _(ft)=====cfo====---------------- ===== (ft' cfo (ft)=====cfe (ft)=====cfo=====________ 13.25 0.0000 14.00 0.4245 14.80 1.1596 15.60 1.5013 13.30 0.1096 14.10 0.4519 14.90 1.3751 15.70 1.5417 ' 13.40 0.1898 14.20 0.6714 15.00 1.6651 15.80 1.5810 13.50 0.2451 14.30 0.7761 15.10 1.2790 15.90 1.6194 13.60 0.2900 14.40 0.8610 15.20 1.3266 16.00 1.6568 ' 13.70 0.3288 14.50 0.9353 15.30 1.3725 13.80 0.3635 14.60 1.0025 15.40 1.4168 13.90 0.3952 14.70 1.0645 15.50 1.4597 ' 13 6/20/97 11 : 20 :49 am Concept Engineering page 3 ' US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing STAGE DISCHARGE DISCHARGE TABLE ' NOTCH WEIR ID No. DNW-1 Description: NOTCH WEIR ON 18" RISER Weir Length: 1 . 0000 ft . Weir height (p) : 0 . 2500 ft . ' Elevation 14 . 75 ft . Weir Increm: 0 . 10 ' STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---Cfo-- ------- (ft) ---cfe-- ------- (ft) ---Cfa-- ------- (ft) ---cfe-- ------- -------------------------------------------------------------------------------------------------------- ' 14,75 0,0000 14,80 0,0371 14,90 0,1978 15,00 0,4358 ' 6/20/97 11 : 20 :49 am Concept Engineering page 4 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing STAGE DISCHARGE TABLE ' MULTIPLE ORIFICE ID No . DO-1 Description: MULTIPLE ORIFICE DISCHARGE Outlet Elev: 13 . 25 Elev: 11 . 25 ft Orifice Diameter: 4 . 2500 in. Elev: 14 . 10 ft Orifice 2 Diameter: 4 . 7500 in. ' STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfe-- ------- 13.25 0.0000 14.00 0.4245 14.80 1.1225 15.60 1.5013 13.30 0.1096 14.10 0.4519 14.90 1.1773 15.70 1.5417 13.40 0.1898 14.20 0.6714 15.00 1.2293 15.80 1.5810 ' 13.50 0.2451 14.30 0.7761 15.10 1.2790 15.90 1.6194 13.60 0.2900 14.40 0.8610 15.20 1.3266 16.00 1.6568 13.70 0.3288 14.50 0.9353 15.30 1.3725 13.80 0.3635 14.60 1.0025 15.40 1.4168 13.90 0.3952 14.70 1.0645 15.50 1.4597 ' 15 ' 6/20/97 11 : 20 :49 am Concept Engineering page 5 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing STAGE DISCHARGE TABLE BROAD CRESTED WEIR ID No. DOW-1 Description: EMERGENCY OVERFLOW SPILLWAY ' cd: 3 . 2100 Weir length: 6 . 0000 ft . El : 15 . 50 ft . Weir Increm: 0 . 10 ' STAGE <--DISCHARGE---> STAGS <--DISCHARGE---> STAGS <--DISCHARGE---> STAGE <--DISCHARGE---> (ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfe-- ------- ' 15.50 0.0000 15.70 1.8605 15.90 5.6520 16.00 8.1713 15.60 0.6334 15.80 3.5445 16.00 8.1713 ' Ib 1 ' 6/20/97 11 : 20 : 49 am Concept Engineering page 6 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing STAGE DISCHARGE TABLE ' RISER DISCHARGE ID No. DR-1 Description: 18" CMP OVERFLOW RISER Riser Diameter (in) : 18 . 00 elev: 15 . 00 ft Weir Coefficient . . . : 9 . 739 height : 16 . 00 ft Orif Coefficient . . . : 3 . 782 increm: 0 . 10 ft STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE <--DISCHARGE---> STAGE a--DISCHARGE---> (ft) ---cf©-- ------- (ft) ---cfo-- ------- (ft) -—cfe-- ------- (ft) ---cfo-- ------- -------------- 15.00 0.0000 15.20 1.3066 15.50 5.1649 15.80 7.6111 ' 15.00 0.0000 15.30 2.4004 15.60 6.5914 15.90 8.0728 15.10 0.4620 15.40 3.6957 15.70 7.1196 16.00 8.5095 ' 6/20/97 11 : 20 : 50 am Concept Engineering page 7 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis R/D Sizing LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAK-> STORAGE ---------DESCRIPTION---------> (cfe) (cfe) --id- --id- STAGE> id VOL (cf) ' 2-YEAR 1.5' POND ?? 0.44 1.76 SP-1 DC-1 14.06 14 4575 29 cf 10-YEAR, 1.5' POND .. . . .. . . .. . 0.91 2.67 SP-1 DC-1 14.44 15 7847.14 cf 100-YEAR, 1.5' POND .. . .. . . . .. 1.47 3.69 SP-1 DC-1 14.86 16 11738.61 cf ' W.Q. STM, 1.5' POND .. . .. . . ... 0.00 0.44 SP-1 DC-1 13.53 17 242.60 cf 1 I v F- J Q d x W Q rn GENERAL ' The water quality design consists of two elements: 1 . Biofiltration Swale 2. Wetpond CODE THRESHOLDS The threshold for biofiltration treatment of impervious surface runoff is 5,000 sq. ft. subject to vehicular use or storage. The site proposes approximately 2.5 acres of such surfacing and thus is ' over this threshold. The threshold for a wetpond (Special Requirement #5) is 1 acre of impervious surface subject to vehicular use or storage, and for the site to be within one mile of a Class 1 or 2 stream. Springbrook Creek is classified as a Class 2S stream and lies approximately 1/4 mile west ' of the site. Therefore, a wetpond is required. DESIGN PARAMETERS & METHOD The design parameters listed in the 1990 KCSWDM have been used to determine the required biofiltration swale and wetpond size. The site design utilizes perimeter swales to provide in excess of the required biofiltration surface area. These swales converge at a combination detention/water quality pond. The results are summarized below: East Swale 2-year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.64 cfs Design Flow Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 inches ' Required Bottom Width for 200 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .00 ft Equivalent Bottom Area Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 ft2 Provided Bottom Area for 460 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920 ft' Actual Channel Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.002 ft/ft Actual 2-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.79 ft/sec Actual 100-Year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.32 cfs ' Actual 100-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.98 ft/sec West Swale 2-year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.65 cfs Design Flow Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 inches ' Required Bottom Width for 200 If Swale . . . . . . . . . . . . 1.03 ft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equivalent Bottom Area Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 ft2 Provided Bottom Area for 384 If Swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684 ft' ' Actual Channel Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.002 ft/ft Actual 2-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.79 ft/sec Actual 100-Year Peak Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.33 cfs ' Actual 100-Year Peak Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.98 ft/sec ' -20- ' Water Quality Pond (Wetpond) ' Water Quality Storm Peak Runoff, Qwq . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.44 cfs Water Quality Storm Runoff Volume, VWq . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6393 ft3 Impervious Surface Tributary to Wetpond, At_,q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125,000 ft2 ' Required Wetpond Surface Area, A, (1 % of At_Wq) 1250 ft2 . . . . . . . . . . . . . . . . . . . . . . . . . . . Required Wetpond Dead Storage Volume = VWq 6393 ft3 ' Proposed Wetpond Surface Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7755 ft2 Proposed Wetpond Dead Storage Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13,210 ft3 Both the biofiltration swales and the wetpond will require seeding with a wetland-type vegetation consistent with the 1990 KCSWDM. ' -21- � BACKWATER ANALYSIS � -22- ' 6/20/97 10 : 59 :47 am Concept Engineering page 1 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis 100-Year Backwater Analysis REACH SUMMARY ' Hydraulic Gradeline for Reach HGL-MN <-FROM-> <--TO--> <FLOW> floss Ent HGL EntLoss ExtLoss OutLet Inlet AppHead BndHead JunHead HeadWtr -cb/mh- ' --------------------cfs -loss--=Elev==_-=loss=---loss=_-=filev----Elev=-==loos=--=loos=--=loos----Elev=-==Rim-- cb-exst 11.26 CB-01 cb-exert 3.69 0.94 12.20 0.07 0.34 12.61 13.17 0.34 0.31 0.00 13.14 17.80 CB-02 CB-01 3.69 2.01 15.14 0.07 0.34 15.55 14.63 0.34 0.11 0.00 15.32 17.00 INL-03 CB-02 3.69 0.05 15.38 0.34 15.72 15.30 0.00 0.00 0.00 15.72 16.00 Network Reach N-MAIN - REACH <-AREA> <-DIA> LENGTH SLOPE < n > DSGN Q % PIPE Ndepth %Depth Vact Vfull C Area ID (Ac) (ft) (ft) ft/ft ------ (cfs) ------ (ft) ------ (fps) (fps) ' P-03 4.17 1.00 6.03 0.0414 0.0120 3.69 43.49 0.48 48.09 9.86 11.07 P-02 4.17 1.00 221.50 0.0065 0.0120 3.69 >=100% Pressure flow 4.69 4.40 P-01 4.17 1.00 103.50 0.0269 0.0120 3.69 54.01 0.55 54.73 8.38 8.92 ' PIPE REACH ID No. P-01 From: CB-01 To: cb-exst Pipe Diameter: 1 . 0000 ft n: 0 . 0120 ' Pipe Length 103 . 5047 ft s : 0 . 0269 Up invert 11 . 8000 ft down invert : 9 . 0200 ft Collection Area: 4 . 1700 Ac . Design Flow 3 . 6852 cfs Dsgn Depth: 0 . 55 ft Pipe Capacity 6 . 8227 cfs ' Design Vel 8 . 3771 fps Travel Time : 0 . 21 min Pipe Full Vel 8 . 9152 fps PIPE REACH ID No. P-02 ' From: CB-02 To: CB-01 Pipe Diameter: 1 . 0000 ft n: 0 . 0120 Pipe Length 221 . 5038 ft s : 0 . 0065 ' Up invert 13 . 2500 ft down invert : 11 . 8000 ft Collection Area : 4 . 1700 Ac . Design Flow 3 . 6852 cfs Dsgn Depth: ft ' Pipe Capacity 3 . 3683 cfs Design Vel 4 . 6921 fps Travel Time: 0 . 79 min Pipe Full Vel 4 .4013 fps (surcharged tt) 2z 6/20/97 10 : 59 : 49 am Concept Engineering page 2 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis 100-Year Backwater Analysis REACH SUMMARY PIPE REACH ID No. P-03 From: INL-03 To : CB-02 Pipe Diameter: 1 . 0000 ft n: 0 . 0120 Pipe Length 6 . 0343 ft s : 0 . 0414 Up invert 13 . 5000 ft down invert : 13 . 2500 ft Collection Area: 4 . 1700 Ac . Design Flow 3 . 6852 cfs Dsgn Depth: 0 .48 ft Pipe Capacity 8 . 4737 cfs Design Vel 9 . 8632 fps Travel Time : 0 . 01 min Pipe Full Vel 11 . 0725 fps 1 2�= 6 20 97 10 : 50 : 21 am Concept Engineering 1 / / P g g page US Rentals - Lind Ave . & SW 34th St . ' SBUH Hydrograph Analysis 25-Year Backwater Analysis ' REACH SUMMARY ' Hydraulic Gradeline for Reach HGL-MN <-FROM-> <--TO--> <FLOW> floss Ent HGL EntLoss ExtLoss OutLet Inlet AppHead BndHead JunHead HeadWtr -cb/mh- -------- -------- cfs -loss- -Elev-- --loss- --loss- --Elev- --Elev- --loss- --loss- --loss- --Elev- --Rim-- 1 __________ __________________________________________________________________cb-exst 11.26 CB-01 cb-exst 3.18 0.70 11.96 0.05 0.25 12.26 13.01 0.25 0.23 0.00 12.98 17.80 CB-02 CB-01 3.18 1.50 14.48 0.05 0.25 14.78 14.47 0.25 0.08 0.00 14.61 17.00 INL-03 CB-02 3.18 0.04 14.65 0.25 14.90 15.04 0.00 0.00 0.00 15.04 16.00 Network Reach N-MAIN REACH <-AREA> <-DIA> LENGTH SLOPE < n > DSGN Q * PIPE Ndepth IlDepth Vact Vfull C_Area ' ID (Ac) (ft) (ft) ft/ft ------ (cfs) ------ (ft) ------ (fps) (fps) P-03 4.17 1.00 6.03 0.0414 0.0120 3.18 37.53 0.44 44.22 9.49 11.07 ' P-02 4.17 1.00 221.50 0.0065 0.0120 3.18 94.42 0.83 83.46 4.54 4.40 P-01 4.17 1.00 103.50 0.0269 0.0120 3.18 46.62 0.50 50.08 8.08 8.92 ' PIPE REACH ID No . P-01 From: CB-01 To: cb-exst Pipe Diameter. 1 . 0000 ft n: 0 . 0120 Pipe Length 103 . 5047 ft s : 0 . 0269 ' Up invert 11 . 8000 ft down invert : 9 . 0200 ft Collection Area: 4 . 1700 Ac . ' Design Flow 3 . 1804 cfs Dsgn Depth: 0 . 50 ft Pipe Capacity 6 . 8227 cfs Design Vel 8 . 0814 fps Travel Time: 0 . 21 min Pipe Full Vel 8 . 9152 fps ' PIPE REACH ID No. P-02 From: CB-02 To: CB-01 1 Pipe Diameter: 1 . 0000 ft n: 0 . 0120 Pipe Length 221 . 5038 ft s : 0 . 0065 Up invert 13 . 2500 ft down invert : 11 . 8000 ft Collection Area: 4 . 1700 Ac . Design Flow 3 . 1804 cfs Dsgn Depth: 0 . 83 ft Pipe Capacity 3 . 3683 cfs ' Design Vel 4 . 5415 fps Travel Time : 0 . 81 min Pipe Full Vel 4 .4013 fps ' 25 6/20/97 10 : 50 : 22 am Concept Engineering page 2 US Rentals - Lind Ave . & SW 34th St . SBUH Hydrograph Analysis 25-Year Backwater Analysis REACH SUMMARY PIPE REACH ID No . P-03 From: INL-03 To: CB-02 Pipe Diameter: 1 . 0000 ft n: 0 . 0120 Pipe Length 6 . 0343 ft s : 0 . 0414 Up invert 13 . 5000 ft down invert : 13 . 2500 ft Collection Area: 4 . 1700 Ac . Design Flow 3 . 1804 cfs Dsgn Depth: 0 . 44 ft Pipe Capacity 8 . 4737 cfs ' Design Vel 9 . 4938 fps Travel Time : 0 . 01 min Pipe Full Vel 11 . 0725 fps � (o � DRAINAGE AREA MAP � -27- fL d d J o 11J d � d O Z ;- u W .. cfj d � L� LJ I I ILw.84TtN 61=1 r'/ 8 1 l A t /' ' .. ...... .............. ... ........._........ ... ...._ ...... 1.j. .. ..... -....-...... a _+ 0 D SIG a N ,AflCH. TE'PLAN. a ' I ` tea.lyg 1{ `� - .. ....... SHE Fill' .6 Of J! t ti \�-134 LF SWALE 1 O 0.20X, 68 SF —x—x--x— �. BOTTOM A A ° � —(2)46 if 8- SD O 0.0�j w 460 LF DIOSWALE 0 0 20% I 920 SF BOTTOM AREA t I+ PROF SED r� t / co t i, BUR IING E T TUB 1 r 15 LF O 1 00% BUILDING: 10600 SF IE 2•DOt sri ul.,, WASH RAC 1390 SF Y1 ...�1;. t 1 .•;iug-1,.1'i Q) '� FIN. 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