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DWR CONSULTANTS, Inc., Gen;echnical lnvesligafion <br />Proposed Saleway Gasoline Sfafion, June 8, 2000 <br />4.0 INVESTIGATION <br />This seciion presents the factual data used to perform the analysis supporiing <br />our ronclusions and recommendations. The only judgements presented are those that <br />we conclude wculd result in near or complete agreement with other professionals <br />working in ihe field. For example, the designation of a soil layer as "silt with fine s�nd" <br />would not t�e an apparent fact to the layman, but would reach consensus among most <br />professionals in geotechnical engineerinc�. <br />4.1 Site Conditions <br />The site is part of the intra-shopping cenier parking and routing area. As such <br />ihe site is covered with either asphalt or architeciural islands. <br />4.2 Subsurface Investigation <br />This site is part of a well developed area. As such we have performed <br />geotechnical investigations or viewed sites under construction within a reasonable <br />proximity of the site. Furthermore, the geology is consistent on this plateau, which is <br />governed by the Holocene Era Scabland Floods. <br />This deposit of compact to dense, coarse gravel, cobble and boulders, little <br />sand, trace silt, down to at least 30 ft. deep provides an excellent soii bearing material. <br />Most difficulties arise during ihe construciion process when ihe excavation contractor <br />disturbs the base and fails to re-compact lhe disturbed sub-grade. We have (ound that <br />the soil contains a high permeability as well. <br />We have found ihat the use of standard geotechniral drills is of little value in this <br />soil (rock) as the Standard Penetration Test (SPT) simply encounters the coarse gravel <br />and cobble without advance. Therefore, the use of a geotechnical drill is of no practicai <br />value. <br />A lithology summary from a test pit, at Reference Site 1(see topographic map}, <br />follows: <br />Surface to 1.7 ft. deep- Compact, BROWNISIT YELLOW SILT, AND FINE <br />SAND. <br />1_7 '� 5 ft. deea- Compact, GRAVEL AND COBBLE, WELL-CEMENTED <br />(cal�+�m carbonate cement). Trace brownish silt. <br />5 ft. to 10 ft. deep- Compact, medium gray, fine-medium-coarse poorly sorted <br />gravel, with cobble and boulders. A basaltic sand is present in the interstices. <br />Area of substantial pit caving. <br />Page 2 of 11 <br />