4730 COLBY AVE SEPA 016 - 027 - YMCA Geotech Report 2025-04-14

October 25, 2015 YMCA - Everett L&A Job No. 15-089 Page 21 rolled with a piece of heavy earthwork equipment prior to fill embankment construction. An 18-inch wide by 24-inch deep key should be cut into the firm bearing soil in the middle of the fill embankment footprint. Fill embankments should be constructed of clean, fine- grained, fine-sandy to clayey silt or clay soil, free of organics and other deleterious substances, with the following gradation requirements: Passing U.S. Standard Sieve No. 100 20 90 40 80 60 65 100 30 200 Fill embankments should be placed in lifts no more than 8-inch thick in loose state and compacted to at least 95% of the maximum dry density determined by ASTM D1557 (Modified Proctor method). After completion, the sloping face of cut banks and fill embankments should be compacted to a non-yielding state with a hoe-pack. If groundwater quality is critical, the rain garden ponds should be lined with a layer of amended soil at least 18 inches thick. The amended soil should consist of 40% of compost by volume mixed with clean medium to coarse sand to achieve an organic content of at least 10% by dry weight. The rain garden ponds should be vegetated for erosion control and the vegetation should be fully established before the ponds can be put in use. Planted vegetation should be tolerant of LIU & ASSOCIATES, INC.