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HomeMy WebLinkAboutRS_Civil_Memo_Drainage_Report_LPD_220110_v1.pdf 1932 First Avenue, Suite 201 Seattle, WA 98101 p. 206.725.1211 f. 206.973.5344 lpdengineering.com Memorandum Date: January 10, 2022 To: City of Renton From: Laurie J. Pfarr, PE Project: Renton School District Lindbergh High School Renovation and Addition LPD Project No: 005-21-01 Subject: Civil Site Plan Review Documents This memorandum is to provide context to why the drainage report will not be included with the civil permit documents as a part of the overall Site Plan Review submittal to the City of Renton for the proposed Lindbergh High School Renovation and Addition project. Based upon the frontage coordination meeting on January 7, 2022, between the City of Renton, the Renton School District, and the Lindbergh High School Design Team, LPD Engineering is revising the frontage improvements per the updated City requests and re-designing drainage improvements to meet stormwater mitigation requirements for both on- and off-site development for the project. Since the site improvements did not independently require stormwater flow control mitigation and it was not until the additional requirements of the frontage that flow control mitigation was triggered. As part of this meeting and due to ongoing coordination and modification of the desired frontage improvements, Michael Sippo, Civil Engineer III with the City of Renton, indicated that the drainage mitigation and subsequent drainage report would hold up or prevent the submittal of the Site Plan Review documents. It was our understanding that both the drainage report and fully engineered frontage plans would not be required to be submitted with the overall Site Plan Review submittal and that the conceptual frontage plans would be sufficient to keep the project moving through the Site Plan Review process. As the project moves through the City’s Site Plan Review process, the Design team will obtain the required additional survey information, meet with the arborist, and continue to design the frontage improvements in accordance with the coordination with the City. Based the coordination with the City, the continued design will confirm threshold basins, look at options to provide mitigation that does not include formal detention, and develop the best stormwater strategy to move forward for both on and off- site mitigation. The project will meet the stormwater mitigation requirements resulting from both the on- site improvements and frontage improvements in the right-of-way in accordance with the City of Renton adopted the 2016 King County Surface Water Design Manual (KCSWDM) and the City’s 2017 Surface Water Design Manual amendment (RSWDM).