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13 /I//v/��/ [�f�j.� /R( J/r� CIVIL ENGINEERING. LAND PLANNING. SU ENVIRONMEN7ALOER�Eq�+ ..o F ........... .... November 11, 1997 irY. Facsimile: (425) 257-8829 Permit Servj F?e Larry Crawford, Public Works Director City of Everett Public Works Department 3200 Cedar Street Everett, WA 98201 RE: Verification of Compliance of Stormwater Management System for Proposed Home Base Project Everett, Washington Our Job No. 5947 Dear Larry: Ibis letter is to summarize the design work completed by our office for the proposed Home Base project and to assure the City of Everett that the stormwater management system and temporary erosion control plans have been designed in accordance with City of Everett development standards and the conditions of the Mitigated Determination of Nonsignificance issued by the City. Our office has completed extensive and detailed design work on the project through coordination with City of Everett staff, Wetland Resources Inc., the Hydro -Geological and Geotechnical Engineers, and the General Contractor to ensure that the final design not only meets the requirements and conditions of the City, but can also be constructed through a series of phases that will minimize impacts to the downstream drainage system and adjacent wetlands while also maintaining adequate on -site storage volumes and erosion control measures to help prevent increased runoff and erosion. ne final design of the stormwater management system will replace both the live and dead storage volumes provided in the existing wetlands that will be filled as part of the project, as well as replace the groundwater recharge and water quality functions. Extensive studies and analysis have been completed by several subconsultants to determine the existing storage capacities, water quality functions, and habitat functions so that these elements can be adequately replaced and incorporated into the overall design of the project. Actual surveyed cross sections were completed within the wetland area, followed by monitoring of the water elevation to measure the fluctuation so that accurate volume calculations could be completed. Conservative values were used in the final design of the stormwater management system. I have reviewed both the final design plans for the permanent stormwater detention and water quality treatment system and the phased grading and temporary erosion control plans for this project. It is my professional opinion that the system has been designed to meet or exceed the requirements of the City of Everett and the Department of Ecology and will adequately replace the dead and live storage volumes and the water quality functions of the existing wetlands. It is also my opinion that the phased grading and temporary erosion control plans have been designed to meet or exceed City of Everett and Department 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX