1901 MERRILL CREEK PKY 2018-01-01 MF Import

• Provide erosion control system redundancies. For examplc, the abave preventive measures should be combined with installation of silt fences, straw bales, and rock check dams where apptopriate. A rock stabilized temporary entrance pad should also be provided at all consuuction entranca to the site. • Implement pettaanent erosion control facitities and l,ydroseed all finished slopes as se�n as practical during the projecc. Temporary erosion protec::on may be necasa.ry until �_. permanent erosion protection is established. I EARTHWORK Site Preperation ! � We.recommend that all areas to be graded be cleared and grubbed of all surface and subsurface deleterious matter including tra stumps, roou, and underbrush. The canditioac encountered in our ezplorations indicate the thiclrness of the topsoil layer beneath the forest duff and undergrowth is approximately 6 to 8 inches. The topsoil may be left in place provided it does not contain significant organic matter. However, the forest duff, tree roots, and all deleterious material should be removed. We mommend that areas prepared for structurai fill be thoroughly proofrolled with heavily + loaded cubber-tired construction equipment if site preparation is done during eztended dry weather conditions. If soft or otherwise unsuitable azeas revealed during proofrolling cannot be compacted to a stable and unifomily dense condition, excavation to firm soil or to 2 feet, whichever is less, and replacement with structurai fill should be accomplishea, or as otherwise � directed by the soils enginear. If site preparation is done during wet weather, the exposed surface should not be proofrollai because of the disturbance that would be caused. During wet weather, the site should be stripped where necessary with lightweight equipment and construction traffic kept off the ezposed surface. The subgrade should be evaluated and p�obed by a representative from our firm to identify areas of loose fill soils which may need to be replaced. Thae loose areas should be overexcavated to the depth determined by our repruentative. ' Much of the native soils possus high fines (silt) content such that repeated construction traffic will result in considerable disturbance during wet weather construction. Therofore, if wet weather construction is necessary, it may be necessary to provide a layer of quarry spalls, ccushed rock or pit mn sand and gravel for construction haul roads if the native soils become wet and begin to pump. Ground water was not encountered in our tat pit ezplorations completed at the site. As described previously, it is our opinion that perched zones of seepage from surface water percolating through the weathered till soils will occur during extended periods of wet weather. Ground water could also be encountered in the outwazh sand above the more impermeable Whidbey Focmation. We anticipate tMat any ground water seepage encountered during construction will be minor and can be controlled by sloping the site to dratn and, if necasary, directing the water to coilection ditches where the water would be pumped. G e o E n � i n e e r � 7 File No. 1�60-006�7�-1170/111297