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Home My WebLink AboutSWP272258 } t STORMWATER DRAINAGE REPORT FOR SPRINGSIDE BUILDING OFFICE/WAREHOUSE FACILITY BURLINGTON NORTHERN INDUSTRIAL PARK LOT 6 RENTON, WASHINGTON April 30, 1996 Z 2 , o LY F ask Iw �1k � o Prepared for: Anderson Richardson Company 300 - 120th Avenue N.E. 32182 Building2, Suite 217 �o��SS�G1sT?, TONAL Bellevue, WA 98005 EXPIRES 8 130! Engineering e Planning Surveying Penhallegon Associates Consulting Engineers, Inc. 750 S=H STREET KIRKLAND, WA 98033 (206) 827-2014 e Anderson Richardson Company Springside building New Office/Warehouse Facility Drainage Report April 30, 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 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 due to the relocation of the storm system and minor raising of the site near the building. 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 not be altered. 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 Springside building New Office/Warehouse Facility Drainage Report April 30, 1996 PACE Job# 96517 Core and Special Requirements: Core Requirement #1: 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 93: 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 w Anderson Richardson Company Springside building New Office/Warehouse Facility Drainage Report April 30, 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 removedand replacing it with an equal or greater amount of detention volume than is required per the original calculations. The control structure will not be altered, only the area provided for detention 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. Temporary Erosion/Sedimentation Control: Interim CB protection will be the only erosion control required for this project. Truck washes may be required depending on site and weather conditions. No other calculations or facilities are required or provided for this project. 3 PENHALLEGON ASSOCIATES CONSULTING ENGINEERS,INC. ................. . ........ ..... ............. M . .... . ........... ..........ud.................- ......... . ...... ......... ....... ....... .. .. 4/30/96 STORAGE REQUIRED: 4,278.00 cu ft STORAGE PROVIDED: 4,324.66 cu ft NET DIFFERENCE: 46.7 cu ft (additional) DEPTH FROM OVERFLOW MANHOLE DIAMETER(in) AREA(sq ft) VOLUME(cu.ft) TO WVERT(ft) CB#1 6.61 (Control M11) 54.00 15.90 105.13 CB#2 4.35 Type 1 3.97 17.28 CB#3 3.65 Type 1 3.97 14.50 CB#4 2.73 Type 1 3.97 10.94 CB#5 1.70 (Rim-Overflow) Type 1 3.97 6.75 CB#6 2.55 (Rim-Overflow) Type 1 3.97 10.13 164.63 CF LENGTH OF PIPE(ft) PIPE DIAMETER(in) AREA(sq ft) VOLUME(cu ft) CB-CB Ex-1 210 12 0.79 164.93 2-3 139 12 0.79 109.17 34 120 12 0.79 94.25 4-5 94 8 0.35 29.32 6-Ex 115 12 0.79 90.32 Subtotal 487.99 CF DETENTION VAULT (Inside Dimensions) Depth Width Length Volume (feet) (feet) (feet) 6.04 18 19.5 2,120.04 CF SURFACE PONDING AT LOADING DOCK AREA Total Volume= 1,380.00 CF (North Loading Dock) Total Volume= 172 CF (South Loading Dock) Loading Dock Total 1,552.00 CF .......... DETSTORG.XLS 4 Anderson Richardson Company Springside building New Office/Warehouse Facility Drainage Report April 30, 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. 5 COMPUTATION SHEET JOB NO. =?2 'DI- c�J DATE SHEET _OF ESM inC. JOB NAME *- A CIVIL ENGINEERING.LAND SURVEY.AND PROJECT MANAGEMENT COMP.BY - CHK.BY CONSULTING FIRM 451 Southwest loth Street Suite 106 Renton,Washington 98055 CONTENTS -`l' - —� - (206)228-5628 Qce-� _ .o 0-10 of,5r V) 6 I ' COMPUTATION SHEET JOB NO. `~ %2 DATE SHEET OF JOB NAME — Kzr%�� ESM inc. - CHK. BY A CIVIL ENGINEERING.LAND SURVEY.AND PROJECT MANAGEMENT COMP. 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