2725 32ND AVE NE 2018-01-02 MF Import

WEYERHAEUSER S611tH IS" LA DFLL.L CLOSURE MAPROVEMIENTS AND NPOES OUTFALL 006 ELYW7K)N SEPA ENVIRONMENTAL Ch6CKUST There are no known surface indications or history r•` ,1):stable soils in the immediate vicinity of the landfill and the outfall. The waste within the landfill has high moisture content and low bearing capacity. e. Describe the purpose, type, and approximate quantities of any filling or grading proposed. Indicate source of fill. Implementing the landfill closure improvements will require the following filling and grading operations: • Excavate waste and re -grade - 33,000 cubic yards • Excavate existing dikes (30,000 cubic yards) and remove sediments within the perimeter ditch (500 cubic yards) • Import clean fill to grade the landfill surface and construct access roads — 82,000 cubic yards • Import drain sand for cover system — 50,000 cubic yards • Import clean topsoil for cover system — 51,000 cubic yards Elimination of Outfall 005 will require plugging the existing outfall pipe. The outfall pipe will be sealed on the river side and the entire pipe will be filled with concrete. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. Best management practices will be in place to ensure that erosion is minimized during the Outfal1005 work. Similarly, construction runoff from within the ditch and the landfill will be collected and conveyed to the Smith Island wastewater treatment system to minimize erosion. g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? No additional impervious surfaces will be added as part of this project. The entire 30-acre landfill cover will include an impervious geomembrane 2 feet below the ground surface. The landfill surface soil will be seeded with native grasses. Any runoff from the landfill and surrounding area will be collected in the perimeter ditch and directed to the wastewater treatment system. h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: As noted above, best management practices will be used to ensure that no erosion occurs during grading along the existing dike and on the landfill. Examples of best management practices include silt fences, straw mulch, and covering of exposed or stockpiled soils. These measures will be determined through the grading permit process. 2. Air a. What types of emissions to the air would result from the proposal (i.e., dust, automobile, odors, industrial wood smoke) during construction and when the pro!, ct is completed? If any, generally describe and give approximate quantities if known. Fugitive dust emissions are not anticipated clue to wet site conditions. Similarly,. emissions from construction equipment and vehicles will be minimal. In accor.lance with Section 9.15 of Puget Sound Air Quality Requirements for Fugitive Dust Control Measures, reasonable 12