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Home My WebLink AboutSWP272258(1) STORMWATER DRAINAGE REPORT FOR BURLINGTON NORTHERN INDUSTRIAL PARK LOT 6 OFFICE/WAREHOUSE FACILITY RENTON, WASHINGTON March 18, 1996 _ LANNthr l� ✓ OF*RFNTOF! Y z Prepared for: Anderson Richardson Company �o 2182 300 - 120th Avenue N.E. TER�'� Building 2, Suite 217 SSIDNAL Y, Bellevue, WA 98005 EXPIRES 6/30/ Engineering e 2qPlanning Surveying Penhallegon Associates Consulting Engineers, Inc. 750 SIXTH STREET KIRKLAND, WA 98033 (206) 827--2014 Anderson Richardson Company New Office/Warehouse Facility Drainage Report March 18, 1996 Pace Job# 96517 Project Description: The site of the proposed office/warehouse facility is approximately 3.70 acres in size and is located at the end of the cul-de-sac on S.W. 39th Street just west of Raymond Avenue and east of Springbrook Creek in Renton Washington. The site is currently a parking lot and was constructed by the Boeing Company in late 1985. The site is flat with typical parking stalls and planters associated with parking lots. The site is bordered to the north by S.W. 39th Street. Railroad tracks and the proposed Pac-Rim warehouse border the site to the east. The west side of the site is bordered by Springbrook Creek and to the south is a commercial building. Both accesses to the site are from the north from S.W. 39th Street. Proposed development of the site consists of an 38,000 square foot office and warehouse facility. Minor grading will occur to achieve a smooth transition from the new building to the existing asphalt. Most earthwork will be fine grading with asphalt and no major earthwork will be required for the proposed building construction. Site Drainage Features: Currently site runoff is controlled by the onsite storm and detention system. The existing system consists of 12" to 18" diameter storm drain pipes and catch basins for the conveyance of stormwater runoff. Detention for the site is contained in the same existing catch basins, storm pipes, and also provided by surface ponding. A plan of the original storm system design has been attached to this report as reference. Due to the location of the proposed building, the entire storm system except the flow control structure must be removed and relocated. The existing surface ponding will be eliminated since the overflow will be lowered to elevation 16.5 from 18.5. The new location of surface ponding will only be in the two loading dock areas. In order to provide an equal amount of detention volume that is being removed, a pipe detention system with a detention vault is proposed for this project. All volume lost due to the placement of the building will be replaced with similar size pipes and storm structures for the proposed storm detention system. The control structure will be altered, however, the diameter of the orifice has been changed to maintain the same allowable outflow rate that currently exists. The majority of the required detention volume will be provided by surface ponding in the loading dock area and the detention vault 1 Anderson Richardson Company New Office/Warehouse Facility Drainage Report March 18, 1996 Pace Job# 96517 Core and Special Requirements: Core Requirement #l: Discharge at the Natural Location - This project will discharge stormwater runoff in the same storm system as the existing system, and thereby satisfies this core requirement. Core Requirement#2: Off-Site Analysis - The proposed new impervious surface for this project is less than 5,000 square feet and therefore is exempt from this core requirement. Core Requirement #3: Runoff Control - The proposed new impervious surface for this project is less than 5,000 square feet and therefore is exempt from this core requirement. This project has an existing detention system that will be modified and is discussed within this report. Core Requirement #4: Conveyance System - The existing conveyance system will be modified and is discussed later in this report. Core Requirement #5: Erosion/Sedimentation Control Plan - See engineering plans for the project erosion control. This project does not propose major earthwork excavation . Erosion control for this project will mostly consist of catch basin interim protection. Sedimentation ponds, swales, etc. will not be required for this project. Special Requirements: There are no Special Requirements that are applicable to this project. 2 Anderson Richardson Company New Office/Warehouse Facility Drainage Report March 18, 1996 Pace Job# 96517 Conveyance and Detention System Modifications Calculations: As previously stated in this report, the existing conveyance and detention system for this site will be modified. Attached as part of this report are the original design plans and calculations for this project's existing storm system basin. The intent of the proposed storm detention system is to replace all storage volume removed without increasing the allowable release rate of the site. The maximum ponding elevation will be lowered to elevation 16.5 According to the original design plans and calculations, the total amount of required storage for the site is 4,278 cubic feet. On the following page is a summary of the proposed storm detention system and a summary of volumes of the proposed structures and storm drain pipes. Catch basin numbers are in accordance with the new design. Size Orifice - According to the original design report of the existing parking lot, the maximum allowable release rate for this project's tributary basin is 0.26CFS. Since allowable outflow is less than 1 CFS only one orifice will be required. Orifice Equation = Q=Ca(2gH)1.5 Qa m.bk = 0.26CFS H = 16.50(Prop. overflow elev.) - 11.50(Prop. inv. elev. @ control manhole). = 5.0 feet C = 0.62 g= 32.2ft/s^2 a = Area of orifice - to be determined Qsllowabio = 0.26CFS = 0.62a(2*32.2*5.0)"0.5 Solving for a = 0.02337 square feet d = Diameter of orifice = (4*a/n)^0.5 = (4*.02337/n)^.5 d = 2.07 inches = 2 1/16" Use sharp edged-shop drilled orifice with 2 3/16" diameter. 3 PENHALLEGON ASSOCIATES CONSULTING ENGINEERS,INC. :.;>:;:::.;:::::.:;:;::: .. .. . ::>: STQ�tAMs.,.�.:�QI.T�1 EXAW: T l T $I . _:. .... ........... ...................... . . .. ............ 3/18/96 STORAGE REQUIRED: 4278.0 cu ft STORAGE PROVIDED: 4283.2 cu ft NET DIFFERENCE: 5.2 cu ft (additional) DEPTH FROM OVERFLOW MANHOLE DIAMETER(in) AREA(sq ft) VOLUME(cu ft) TO INVERT(ft) CB#1 5.00 (Control MH) 54.00 15.90 79.52 CB#2 3.50 Type 1 3.97 13.90 CB#3 2.99 48.00 12.57 37.57 CB#4 2.74 Type I 3.97 10.88 CB#5 2.26 Type I 3.97 .8.98 CB#6 2.10 Type I 3.97 8.34 CB#7 1.00 Type I 3.97 3.97 CB#8 1.00 Type I 3.97 3.97 CB#9 3.30 Type I 3.97 13.11 180.25 CF LENGTH OF PIPE(ft) PIPE DIAMETER(in) AREA(sq ft) VOLUME(cu ft) CB-CB 1-2 195 12 0.79 153.15 2-3 136 12 0.79 106.81 3-4 63 12 0.79 49.48 4-5 118 12 0.79 92.68 5-6 39 12 0.79 30.63 6-7 53 12 0.79 41.63 8-6 53 8 0.35 18.50 9-1 115 12 0.79 90.32 Subtotal 583.20 CF 'ENTION VAULT (Inside Dimensions) Depth Width Length Volume (feet) (feet) (feet) 5 20 24 2400 CF SURFACE PONDING AT LOADING DOCK AREA Total Volume= 1062 CF (North Loading Dock) Total Volume= 234 CF (South Loading Dock) ... ..... ............. DETSTORG.XLS 4 Anderson Richardson Company New Office/Warehouse Facility Drainage Report March 18, 1996 Pace Job# 96517 Temporary Erosion/Sedimentation Control: All erosion/sedimentation control facilities can be seen on sheet C 1. Interim CB protection will be the only erosion control required for this project. No other calculations or facilities are required or provided for this project. 5 Anderson Richardson Company New Office/Warehouse Facility Drainage Report March 18, 1996 Pace Job# 96517 EXISTING PARKING LOT DESIGN CALCULATIONS Note: The attached calculations are only the relevant portion of the total calculations for the existing parking lot. This project only proposes to modify a small portion of the overall parking area. The drainage basin that this project lies within was termed Basin "A" of Parcel No. 2. The attached calculations only show values for this project's portion of the existing site. COMPUTATION SHEET JOB NO. �?O -DI- c�J DATE ,3� SHEET OF ESM inc. JOB NAME _ 7= 1✓ �'-r c�t - - 1=r: �.-��' .IC. (� T A CIVIL ENGINEERING,LAND SURVEY.AND PROJECT MANAGEMENT COMP. BY CHK.BY CONSULTING FIRM .i 451 Southwest 10th Street Suite 106 Renton,Washington 48055 CONTENTS (206)228-5628 L- - �u - B-A&lN A A � Tc = 1c �r;� _ �. j u77- j i � D AL �r i COMPUTATION SHEET JOB NO. _`� " 7 �� DATE o 2 SHEET OF_� ESMinC. JOB NAME -- - A CIVI4 ENGINEERING,LAND SURVEY.AND PROJECT MANAGEMENT COMP. BY CHK.BY. _... _. CONSULTING FIRM 451 Southwest loth Street Suite 106 Renton.Washington 98055 CONTENTS (206)228-5628 .�.i`eL -�v�PS= -r- - 2 s L 4- - ems l n v• 5 - _COMPUTATION SHEET JOB NO. DATE12 �` SHEET OF ESM inc. 9JOB NAME ^—''IG f+ T�.7�(.t A CIVIL ENGINEERING.LAND SURVEY,AND PROTECT MANAGEMENT COMP. BY � CHK.BY CONSULTING FIRM 451 Southwgst 10th Street Suite 106 Renton,Washington 98055 CONTENTS _—_- (206)228-5628 �rze �oNprnl Cam. -C42 zZ ZSv4- 1 417 23 Si7�, C D.5 ')�,3 4- z lc c.5 4-7 Z I I i 1 42-7810 �o�J�rJ%• `�o LLB-�� ? ,��J 1 Vo 3D S cog. 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