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l <br /> i' <br /> Wright <br /> Environmental <br /> Ser-vices, Inc. <br /> June 21, 1995 <br /> Project No. 4062-R <br /> San Joaquin County JUN <br /> Public Health Service-Environmental Health Division 2 6 199 <br /> P.O. Box 2009 ENVIRON <br /> 445 N. San Joaquin Street pF�MlTIS&TTALV, HEALTH <br /> Stockton, CA 95201 RVlCES <br /> ATTN: Ms. Linda Turkatte <br /> Re: Subsurface Soil and Groundwater Sampling <br /> Groundwater and Vadose Welt Installation and Modification <br /> Waterloo School, 7007 N. Pezzi Road, Stockton, CA <br /> Dear Ms. Turkatte, <br /> Wright Environmental Services, Inc. (Wright) has prepared this workplan for the <br /> above referenced site. As you know Wright has discussed this project in several <br /> conversations with the San Joaquin County Public Health Services-Environmental <br /> Health Division (PHS-EHD) representative's remediation concerns and the desire of <br /> the PHS-EHD for interim site cleanup given the lack of funds of the Linden School <br /> District (District). This Nvorkplan supersedes all other technical workplans and <br /> scopes of work previously discussed or submitted to PHS-EHD. <br /> Introduction and Technical Approach <br /> it is our understanding that an interim vadose zone cleanup is desired at this time by <br /> the PIIS-EHD. The District currently has funds for only limited assessment and site <br /> mitigation. It is important for at least some additional assessment to be done since the <br /> previous consultant did not install a monitoring well to groundwater, but completed it <br /> as an excessively screened vapor monitoring well. Consequently, the groundwater <br /> quality at the spill source is unknown several years after the fact. Also the design of <br /> the existing vadose well is questionable and may crosscut vadose aquitards which <br /> could have been retarding horizons to vertical contaminant migration. This design <br /> deficiency may be detrimental to the overall goal of cleaning the site. <br /> Soil contamination in the vadose zone has been only partially defined, with data gaps <br /> at the depth interval of about 26.5 feet to 56 feet, and below 82 feet. The highest <br /> concentrations of Total Petroleum Hydrocarbons as Gasoline (TPHG) observed were <br /> 7,500 parts per million (ppm) and Benzene at 35 ppm at the 26.5 foot depth. <br /> Groundwater is currently estimated to occur at depths of over 100 feet, and the <br /> installation of several groundwater monitoring wells at this time would pose a <br /> burden to the budget of the District. Wright feels that groundwater quality should be <br /> addressed at this time, at least to the reconnaissance level, regarding the current <br /> conditions. Also some additional soil data is needed to ascertain what contaminants if <br /> any are present at the 25 foot to 56 foot interval, and below 85 feet to the capillary <br /> fringe. In this way, the District will have a minimum knowledge of existing <br /> conditions in the vadose soil column and groundwater. <br /> Waterloo School Workplan Page 1 <br /> 4220 Commercial Dr. #5 • Tracy,California 95376 `A, <br /> Telephone (209) 833-0758 • Fax(209) 832-5152 <br />