9300 W MALL DR 2018-01-01 MF Import

G & M Znvestments November 11, 1993 It should be noted that groundwater with rainfall and other fact�rs. groundwater could be found between the soils and the underl�ing glacial till, soil layers or pockets within the till GENSRAL P-3161 Page 4 levels vary seaeonally We anticipate that near-surface weathered and in more permeable soils. CONCLUSIONS AND RECOt�LENDATION3 The teat pits encountered typical soil conditions found throughout most of the upland areas around Puget Sound. Below the topsoil layer is a layer of tan, weathered glacial till often referred to as Alderwood loam. This soil overlies dense ylacial till that is highly consolidat�d and hae poor permeability. The small wetlands on the site have been created by poor surface drainage causing wet conditions. The water is perched above the relatively impermeable glacial till soils. The plans provided show that the parking garage for the buildings will be set below the adjacent wetland elevation. This excavation is likely to encounter water seepage and wet soil conditions. However, we anticipate ttiat the site can be dewatered with trench drains� and pumps in aumps in the excavation. A large amount of water is not expected based on the test pit results. It is our opinion that the project will have no effects on the wetlands due to the relatively impervious soil conditions located betweer� the drains required for the baaement aad the wetland areas. We recommend that the excavation be covered with a layer of quarry spalls or a"mud" slab of lean concrete to protect the excavation subgrade during the construction process. The thickness of the layer required will depend upon conditions observed at the time of the excavat.ion. We recommend that the footing beari�ig surfaces be protected with a thin layer of cncrete placed immediately after excavation if wet conditions are found. Underslab drains also will be required where wet conditions are observed. These drains can be constructed in a similar manner to the foundat:on drains. In addition, a mat of gravel or clean crushed r� :k will be required if seepage is encountered. We prefer to leave the decision as to the necessity of additional drains, drain spacing, and drain mat thickness until the site is excavated. However, for olanning GEOTECH CONSULTANTS� ZNC.