7000 HARDESON RD 2018-01-02 MF Import

PUBLIC WORKS MEMORANDUM TO: Al Locke/Gordon Witcher FROM: Jane Zimmerman DATE: June 3, 1996 SUBJECT: Drainage Calculation/Compost Filter Review, Community Transit A letter should be sent to the City from the applicant indicating how much of the available 4.43 acre feet of regional stormwater detention will be used to satisfy stormwater detention requirements for this site. Owners of currently undeveloped parcels of the Merrill Creek site (that were originally a part of the Seaway Center Binding Site Plan, SEPA #30-90) should receive copies of the letter. A copy of the operations and maintenance manual, referred to on sheet 6.4 of the civil plan set, must be provided to the City for review, approval, and future reference. The testing results the City currently has appear to be for the original compost bed treatment configuration. I have some concerns about the effectiveness of the radial filters, particularly with respect to the linear distance stormwater will flow through the compost media. If test results exist for the radial cartridge configuration, they should be submitted with the drainage calculations. At the very least, the applicant should indicate the distance of the flow path through the radial filter as opposed to other treatment configurations for Jch monitoring of pollutant removals has occurred. To satisfy the conditions of the DNS for this project and City standards, the removal efficiencies of the treatment system should be at least as good as expected for a wetpond designed in accordance with City standards.