7000 HARDESON RD 2018-01-02 MF Import

PUBLIC WORKS MEMORANDUM TO: Al Locke/Gordon Witcher FROM: Jane Zimmerman DATE: July 16, 1996 SUBJECT: Drainage Calculation/Compost Filter Review, Community Transit The applicant has submitted testing results from the radial flow compost filter units and also a maintenance and operations manual. This information has addressed many of my previous questions/comments, with the exception of the following: A letter must 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 contingency plan must be submitted to the City for review and approval, defining what constitutes failure of the compost system and indicating the steps to be taken in the event of system failure. For clarification, this contingency plan will address the actions to be taken should reasonable maintenance and replacement of the cartridge filters not suffice to keep the system operating and treating the design flow. A monitoring plan must also be submitted to the City for review and approval. For clarification, the City's goal for the monitoring plan is to ensure that the flow through the compost filters remains adequate to treat the stormwater runoff from the 6 month, 24-hour storm. We are willing to assume that if flow actually occurs through the compost, with an adequate resident time, that the stormwater will be adequately treated. Therefore, the City intended for this plan to focus on the hydraulics of the system relative to sediment loading and its impact on flow through the filters. n +J