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�ugvsi �a , iq 4q <br /> �Qs7an� Q�e�t <br /> Former Discharge Area :Investigation Report <br /> Trinkle and Boys Agricultural Flying service Facility <br /> Tracy, California <br /> OWN 1. . r) Introduction <br /> The following .report presents the methodologies, findings and <br /> conclusions of a shallow groundwater and soil investigation <br /> conducted by ROY F. WESTON, INC. (WESTON) as specified in the <br /> Former. Discharge AreA :investigation Work Plan dated July 29 , 1989 <br /> as amended by WESTON's letter to John Menke at the California <br /> " dated April 14 , <br /> Recjional. Wates: Quality Control Board (CRWQCB) <br /> 1+91^119 The i.nv .stigation focused on the determination of the <br /> extent of pesticide residues in the shallow soil-s and groundwater <br /> ` -►'. the Trink!e ..nci Boys Agricultural Flying Service (Trinkle and <br /> facility located at 31244 South Highway 33 , Tracy, Califor-- <br /> nia. <br /> ho 2 . 0 Site Background <br /> Tx*i.nkl.e and Boyce awns and operates an aerial agricultural crop <br /> .m spray application facility as shown on Figure 1. The site has <br /> be.f-:n used. for the loading and rinsing of aerial applicators since <br /> to 1950 ' x. ]:'rior to 1986, rinse water runoff was collected in a <br /> low drainage area (identified as the "Gravel Rinse Basin" on <br /> WM Figure 1) southwest of the aerial applicator loading area. Since <br /> 1986, the applicator rinsate has been stored in a large plastic <br /> tank. for reu.sc-< i:it.. the fac.i_.l.ity. <br /> om <br /> In 1986, as part of a district wide investigation of aerial <br /> applicators, the CRWQCB gathered shallow soil and shallow ground- <br /> ` 6,!ate.r samples from within the rinse basin area. Analysis of <br /> ttzc=se samples rcve.aled the presence of various pesticides and <br /> l,.erbi.c-:i.des, a f.'ollow-up to their initial investigation, the <br /> CR'0QCB, on October 27 , 1987 , issued Cleanup and .Abatement Order. <br /> No.. 87-734 to Trinkle and. Boys. The Cleanup and Abatement Order <br /> specified thatt follow-up activities be conducted in an effort to <br /> evaluate if pesticide residues , identified by the previous <br /> sampling, extended deeper into the soil. profile, thereby posing a <br /> threat to the beneficial usages of groundwater in the area. <br /> This report covers Activities #1 and #2 as specified by the <br /> Cleanup and Abatement Order. Approval of the amended Work Plan <br /> was provided by the. CRWQCB on April 24 , 1989 . <br /> r. 3 . 0 Field Work. <br /> Field work consisted of the drilling and installation of three <br /> shallow groundwater monitoring wells, the sampling and analysis <br /> of groundih,ater at the three wells and soil sampling and analysis <br /> , a total of six. borehole locations. Placement of the wells was <br /> designed to provide: site specific groundwater gradient <br />