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

Yroposed Retail Developmenc J-1443 1 l2'�Street and Hwy.99 Pebruary 26,2004 ` fiverctt,Washington Page 2 center of the subject property. A layer of undocumented fill between 5 and 9Ys feet enco'�uitered in tcst pit TP-9 (Phase II, October 2002) contained significant amounts of inetal, tires and wood debris. Interprctul fill depths aze presented on Figure 1, the Sitc and Exploration Plan. • Layers of organics and peat were encountered in test pits TP-1, TP-7, and TP-8 during the October 2002 Limiled Phase Il Environmental Assessment as wel( as in borings B-11, B-24, and B-30 completed as part of this evaluation. The soft peat varied in thiclmess&om 1 to 6%z feet and was covered with 3 to 6Yz feet of undocumented fill. • During the October 2002 Limited Phase II evaluation, hydrocazbon odors were noticed during the excavation of test pits TP-7, TP-9, and TP-17. Lahoratory test results indicated that lhe Total Petroleum Hydrocarbon concentrations varied from 140 ppm to 660 ppm, all beluw the MTCA Mcthod A cleanup standards. • Surficial topsoil was cncountered in several exploradons across the site and typically varied from 2 to 6 inches in thickness. However, a few explorations encountered topsoil that varied in thickness from 8 to 18 inches. In generel,near-surface topsoils had organic contents of less than 6 percent, although a few areas of surficial material had organic contents of 8 to i l percent. Some layers of relic topsoil were also encountered below undocumented fills. • Slight to moderate groundwater scepage was observed in 24 of the 32 borings completed as � part of tlils evaluation. Additionally, slight to heavy groundwater seepage was observed in 12 of the 21 test pils completed as part of this evaluation. The seepage observed was generally interpreted to be perched groundwater above the dense to very dense glacial till soils. Thc depths to groundwater vazied from lYs to 9 feet below existing grades. Perched groundwater is likcly to bc more prevalent across the site during and after wintcr rains. Sitc Preparation • Where present, topsoil typicafly was on the order of 2 to 6 inches thick and contained most of the root systems of the grass, weeds, and brush. Average stripping depths on the order of about 4 inches should be anticipated across the site. 5ome areas of decper organic-rich soil should be expected across the site. The feasibility of Icaving low organic content topsoil in place should be determined at the time of grading, based on soil organic content, stabiliry of the subgrade and thiclrness of non-organic struciural fill placed ovcr it. • All undocumcnted fill soils within the building pad should be overexcavated and replaced with compacted structural fill. In most cases, the fi(1 appears to be suitable for reusc as structural till from a composition standpoint. However, the fills may require drying to achieve lhe minimum compaction levels. Fill such as lhat encountered between 5 and 9%:feet bclow grade in test pit TP-9 (October 2002 cvaluation) should be considered unsuitable for � rcuse as structural fill due to the significant amounu of wood,metal and other materials. ' • The pcat encountered in boring B-11 and test pit TP-1 (Oct�bcr 2002 evaluation) should be � completely rcmoved from thc building pad area including those arcas extending 10 feet J-1443,022604 � �