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Stormwater Drainage System Minimum Maintenance & Repair Introduction Redmond Municipal Code (RMC) 13.06, titled Stormwater Management, requires that stormwater drainage systems be maintained, citywide. This document has been developed by the stormwater utility to provide drainage system owners/operators a concise document outlining minimum requirements for maintenance and repair of stormwater drainage systems. This document also locally modifies some maintenance standards (detailed below). Maintenance and Repair Requirements In 2007, The City of Redmond updated its Clearing, Grading, and Stormwater Management Technical Notebook (“Stormwater Notebook”) which governs various aspects of how Redmond does stormwater management. The Stormwater Notebook locally adopts the 2005 Washington Ecology Stormwater Management Manual for Western Washington (“2005 Ecology Manual”), which focuses on development and redevelopment stormwater management regulations. The 2005 Ecology Manual also regulates stormwater system maintenance requirements and source control measures (which reduce pollutants from being introduced into runoff and water resources). Volume V, Chapter 4.6 of the 2005 Ecology Manual provides detailed discussion of maintenance requirements, which constitutes the remainder of this document. Locally Modified Maintenance Standards Redmond has made some local modifications to Volume V, Chapter 4.6 of the 2005 Ecology Manual. These modifications are to include pipe maintenance standards as well as tighter maintenance requirements to some stormwater drainage system features. These local modifications are discussed in the Stormwater Notebook and are as follows. The numbering below (i.e. No 4) has been used to indicate which stormwater facility number in the 2005 Ecology Manual is locally modified. No. 4 Control Structure/Flow Restrictor: Redmond requires cleaning when material/sediment exceeds 20% from bottom of the control structure to lowest outfall pipe. The City shall require cleaning of any control structure where visible oil sheen/pollution is identified during inspection. ---PAGE BREAK--- No. 5 Catch Basins Catch basin shall be cleaned when the sump has 60% of it volume obstructed by sediment/debris. No. 15 Stormfilter™ (leaf compost filter) All media filter cartridges regardless of the type of media will use the 2005 Ecology Manual requirements for maintenance. No Number Vortex/Swirl Concentrator manholes (considered vaults in city’s mapped system): Will be maintained and cleaned annually and recharged with clean water after maintenance. Pipe Maintenance Requirements The 2005 Ecology Manual does not provide maintenance requirements for conveyance (i.e. pipes) as a separate feature it is part of the structure (catchbasin, manholes, control structure, vaults, ponds) Redmond inspects conveyance as a separate part of the stormwater system. When sediment/debris exceeds 10% of pipe or culvert volume it will need to be cleaned. All pipes or culverts with roots will need to be root cut if blockage is too great or pipes become damaged due to excessive root cutting those sections of the pipe will need to be replaced with like pipe material. Failed infiltration pipes, drywells or trenches will need to be re‐designed to meet new regulations for replacement and or removal. Please contact the City of Redmond Wellhead Protection Program for more information about replacing/removing infiltration systems. Phone [PHONE REDACTED] or e‐mail at [EMAIL REDACTED] Maintenance Standards for Emerging Stormwater BMPs not in the 2005 Ecology Manual or the Stormwater Notebook: All facilities that do not have maintenance standards discussed in either the 2005 Ecology Manual or the Stormwater Notebook are required to have a maintenance manual submitted with the City prior to installation (RMC 15.24). The maintenance manual provided to the City during installation shall be kept by the owner if privately owned/operated. ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK---