5221 23RD AVE W 2023-04-10 - Laserfiche WebLink

• • September 10, 2021 G-5535 Geological Assessment Letter Page 4 5221 23`d Avenue W,Everett, Washington hazard area can safely be reduced to a minimum distance of up to 25 feet while still protecting the sloped areas to the east from being disturbed by the proposed development activities. To eliminate potentially significant geological hazards on the proposed development site and off- site properties, grading and mitigation work for the proposed deck should be restricted to the minimum needed to achieve proposed final grades. The area where construction work will be performed should be cleared of vegetation,topsoil, organics, debris, and any other deleterious materials that are found. These materials should be hauled off site or used for landscaping, as appropriate; they should not be used as backfill for the project. Temporary erosion and sedimentation controls (TESCs) should be installed as part of site clearing activities. TESCs for the project can include using silt fences, check dams, straw mulch, hay bales, and a stabilized construction entrance. The silt fences or other barrier controls should be placed along the construction perimeters to prevent sediment-laden runoff from being discharged off site. Additional fencing should be placed along the east property line to protect the mapped potential landslide area and ensure that the sloped topography east of the property will remain undisturbed over the duration of the project construction. Exposed soils, including stockpiled soils, should be covered with plastic sheeting when they are not being worked. Post-construction erosion potential can be mitigated by a combination of terracing disturbed areas with retaining walls or rockeries;planting new vegetation; placing landscape gravel or pavers; and limiting permanent unreinforced or unsupported slopes to inclinations of 2H:1 V (Horizontal:Vertical) or less. Sincerely, GEO Group Northwest, Inc. vg,M Cy N hp�C wASNi �'r fr-, h_ wet. tT • �T920,i4o .��, Bryce Frisher,E.I.T. Fss�lsT�¢��c,� ' William Chang,P.E. Staff Geotechnical Engineer �QNAI Principal Engineer GEO Group Northwest,Inc.