Cedar Grove Composting Stormwater Permitting

(Maple Valley, WA)  Cedar Grove Composting recycles 350,000 tons of residential and commercial yard and food waste every year at its Everett and Marysville facilities. Landau Associates provided design and stormwater permitting services for a 9-acre finished-compost storage pad for Cedar Grove’s Maple Valley composting facility. Our services included geotechnical engineering, assessment of stormwater discharge by the composting facility; preparation of a Stormwater Pollution Prevention Plan; design of stormwater detention/infiltration facilities with a bioretention swale to pre-treat and manage runoff from the storage pad; and consultation with regulatory agencies regarding the discharge of stormwater to surface water at the facility.

Our geotechnical services for the storage pad included evaluation of subsurface soil and groundwater conditions, slope stability assessments, subgrade preparation, pavement design for support of heavy equipment and storage loads, preparation of specifications for site earthwork activities, and project construction drawings.

Landau Associates staff worked closely with King County Department of Permitting and Environmental Review to acquire the necessary permits for clearing and grading, and with the Washington State Department of Ecology for the construction stormwater permit. We also coordinated with the Washington State Department of Fish and Wildlife and U.S. Army Corps of Engineers to design the critical area mitigation plan for wetland and stream impacts in compliance with state and federal guidelines. We are currently overseeing the installation and monitoring of the stream and wetland mitigation.