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Geofogicaf Technics Inc. <br /> 2601 P ver Ppad 93 d U 4' Imak' <br /> Modesto,California 95351 <br /> (2 09)538-64241Fax#538-5852 <br /> June 7, 1993 <br /> Mr. Mike Collins <br /> San Joaquin County <br /> Public Health Seraices <br /> Post Office Box 2009 <br /> Stockton,California 95201 <br /> RE: Addendum to Work Plan Lodi Ready Mix and Building Materials <br /> - 851 East Lodi Avenue,Lodi, CA <br /> Dear Mr. Collins: <br /> I am following up to our site meeting of June 1, 1993. We discussed the location for the <br /> confirmation soil boring and determined that thebest location is just to the south of the Former <br /> f excavation as determined by 1) interview of an;employee and 2) the observation of newer <br /> concrete pad presumably over the former excavation area. The attached Figure 2 Site Map <br /> shows the approximate location for the proposed soil boring. <br /> t We had also discussed the possibility of'l) an angle boring in which I recommended against <br /> because of a very limited target zone and the definition of a vertical concentration gradient <br /> cannot be known for a discrete area (which in your letter you request) and 2) drilling through <br /> the excavation which I recommended against because if pea gravel had been used to backfill the <br /> excavation (which is common practice to achieve necessary compaction) then drilling down to a <br /> significant depth (40 feet) would be prevented because a peagravel formation lacks shear <br /> strength and will slough into the boring and be flighted to the surface causing a large void <br /> beneath the concrete pad by the time 40 feet is achieved. <br /> Please call with your comments. <br /> Sincerely, <br /> GEOLOGICAL TECHNICS INC. <br /> i Timothy J. McDonald <br /> Geologist <br /> TJM/tam <br /> cc: Patrick Sherman, E.F. Mitchler Company <br /> Beth Thayer,RWQCB <br /> i <br />