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HomeMy WebLinkAboutRS_Drainage Memo_230424_V1.pdf 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.426.2600 | JACOBSONENGINEERS.COM MEMO REPORT To: City of Renton CED From: Alan Jacobson, PE Date: April 24, 2023 Subject: Hazen High School – 2023 Portables Drainage Memo Report This project involves the installation of two double portables (or 4 classrooms) that will be installed in the north central parking lot of the existing school property. These proposed portables will be placed on top of the existing asphalt surface, and no asphalt will be removed to install them. Splash blocks will be utilized to direct the storm runoff from the roofs, gutters and downspouts on to the existing asphalt to directed towards the closest catch basins. and gutters, The new portables will require some new underground utilities (communication, fire and power) to provide service. These utilities will be coming from the existing building, and be installed under the existing asphalt, and then patched. The clearing limit for utility trenching, is approximately 1,500 SF of disturbed area. Also, this Project will not construct/ modify a pipe/ditch 12-inches or larger, nor does it receive runoff from such a system. The Site is not in a flood, erosion, steep slope hazard or landslide hazard drainage area. The project is not a redevelopment project of an existing high use site. Based on these quantities and site characteristics, this Project falls below the thresholds for drainage review (less than 2,000SF new/replaced impervious and less than 7,000 SF land disturbing activity) as identified in Section 1.1.1 of the Renton Surface Water Design Manual. Several ESC/SWPPP measures are specified on the plans and were chosen in consideration of the lists in Section 1.2.5.1 of the Renton Surface Water Design Manual. Please contact me should you have any questions.