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Lerner Texaco 521 North Cherokee Lane, Lodi Site Code 1324 August 1, 1995 Page 2 "closure " As it may be possible to use MW-1 with a vapor extraction system (potentially as an extraction well or a sparge well), the destruction should not be performed until after a vapor extraction test at the site In addition, I recommend a monitor well be installed in the parking6 lot of the Del Rancho Motor Inn to allow an assessment of the southern migration of the plume and a monitor well on the south side of Murray Street west of the site to assess contaminant migration within the southwest quadrant Furthermore, based on the results of the CPT survey, it appears that vapor extraction may be a viable remediation alternative Therefore, several vapor Q) wells should be installed to allow testing and potentially interim remediation Lastly, because the pump island area has yet to be investigated and significant soil contamination has not been reported at this site, I recommend collecting soil data from beneath each of the pump islands Workplan Addendum This addendum provides the proposed locations and rationale for the wells/borings recommended above Each of the wells/borings will be installed in accordance with the 13 March 1994 workplan unless either otherwise stated herein ,or discussed with (and approved by) the lead regulatory agency (SJCPHD/EHD) Soil Bonngs Two soil Bonngs (B-4 and B-5) will be advanced in the pump island area (Plate 3) Because of the limited access, the borings will be slant drilled to allow the collection of a soil sample beneath each end of each pump island It is anticipated that the southern end samples can be collected at a depth of approximately 5 feet bgs while the northern end samples may be as deep as 20+ feet bgs Vapor Wells Three vapor wells are initially proposed (Plate 3) The wells will be roughly triangulated to allow an evaluation of potential spacial heterogeneities Each vapor well boring will be continuously logged to provide detailed lithologic information for remedial design and correlation to the CPT data It is anticipated that at least VE-1 and VE-2 will be screened from l.-- approximately 15 feet bgs to approximately 40 feet bgs Because VE-3 is proposed in a location where the soil column is not thought to be significantly impacted, VE-3 may be screened near the groundwater's capillary fringe Final well design will be dependant on field evidence collected during drilling Monitor Wells Two onsite and five offsite monitor wells are proposed to verify the contaminant limits established with the CPT survey and better define the groundwater plume in the southwest quadrant (Plate 3) A soil sample from within the capillary fringe of each well will be analyzed for TPH as gasoline and BTEX