11632 EVERGREEN WAY BASE FILE 2018-01-01 MF Import

Proposed Retail Development J-1�-43 - 112°i Street and Hwy. 99 February 26,20G4 � fiverett,Vdashington Page 11 Stripping,excavatiun, grading,and subgrade preparation should'oe performed in a manner and scquence that will provide drainage at all times and prcvide proper control of erosion. If ponded surfacc water collects it should be pumped or drained to provide a suitable working .c` p]atform. The sile should be graded to prevent water from ponding in conskuction azeas and/or i tlowing into excavations. Exposed grades should be crowned, sloped, and smooth-drum rolled at th, end of each day to facilitate drainage if inclement weather is forecasted. Accumulated water must be rcmoved frnm subgrades and work areas immediately and prior to performing further work in the area. Equipment acccss may be limited and f amount of soil rendered unfit for use as structura] fill may be greatly increused if drainage efforts are not accumplished in a timely sequence. Site preparation should inc(ude demolition and removal of all existing buildings and utilities on the sile. Buricd utilities, underground storage tanks or septic tanks on the site should be remo��ed, relocated, or abandoned, as necessary, in accordance with all local, state and federal regulaticas. Localized excavations made for removal of foundations, underground structures, utilities, and the removal of unsuitable/undocume��'.ed fill materials should be backfilled with structural fill as outlined in the following section of this report. We recommend that the large- diameter concrete pipc that routes Swamp Creek beneath the site be completely reoved and the resulting excavation backfilled with compacted slructural fill. We also recommend that a ditch plug bc installed in the end of the trench excavation nearest to the new stream alignment. This would prevent seepage from entering the structural bac�ll and migrating under the proposed building. ( Site prepazation will also tequire removing surface vegetation and organic-rich topsoil or other deleterious materials in planned building and pavement areas. Weeds, brush, trces, and tlicir associated root systems, as well as a sporadic organic-rich topsoil layer were encountered. We estimate that the average topsoil thiclaicss is on tl�e ordcr of 4 inches. However, topsoil as thick as 18 inches was encountered. 7'he stripped topsoil and roots should be considered unsuitable for reuse as structural fill. Dee�cr cxcavations to remove additional organics such as trce ronts should be anticipated across the site. Actual removal depths should be determined by a representative of ZZA at the time of grading bascd on the subgrade material's organic content and stability. At a minimum, all undocumented fill soils aad native peat soils within the building pad should be overcxcavated and replaced witi: compacted structural fill. In most cases, the fill appears to b� reusable as structural fill from a composirion standpoir.t. However, some the fills may require drying to achieve the minimum compaction leveis. The undocumented fill that was encountered 'ut test pit TP-9 of this evaluation is considered unsuitable for reuse as structural fill because of the considcrable arimount of deleterious material (tires, metal, plastic, etc.) in the soil. When unsuitab(c fill ic know to be present or when it is encountered duiing construction, we recommend that it be entirely removed (chased) and replaced. The material should be considered unsuitablc for any use on site and it should be hauled to an approved off-site disposal location. Layers of organics and peat wcre encounte:ed in test pils TP-1, TP-7, and TP-8 during the ' October 2002 Limited Phasc II Environmental Assessment as wcll as io borings $-11, B-24, and B-30 complcted as part of this evaluation. T6e�nft peat vazicd in thiclmess from 1 to 6Yx feet and was covercd with 3 to 6%z feet of undocumen[eu Within the building pzd, the peat should be J-1443,022l04 � 11 �