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,::,;� <br />- _xe <br /> IRESNA WATERWORK CORP. <br /> TR UES <br /> t� <br /> s <br /> April 2, 1991 , <br /> APR i 3 '^"f <br /> ENVIROWAFNTAL HEALTH <br /> Ms. Diane Hinson PERMIt/SERVICES <br /> San Joaquin County public Health Services <br /> Environmental Health Division <br /> P.O. Box 2009 <br /> Stockton, CA 95201 <br /> Re: 1991Secvrid- uarter Report-Tri-Valley Growers, <br /> 26200 Novell Road, Thornton, CA. <br /> Dear Diane: <br /> This letter report updates the activities at Tri-Valley Grower's <br /> Thornton plant during the second quarter of 1991. Activities <br /> during the quarter have included sampli).3 for dissolved hydrocar- <br /> bons and monitoring of groundwater. <br /> Groundwater monitoring conducted in January, February, and March <br /> showed the water table has risen from 2.3 to 3.4 feet during the <br /> quarter (,able 1). The groundwater contour maps (Figures 1-3) show <br /> the direction and magnitude of the gradient (Table 1) has shifted <br /> from a westerly direction last quarter to a southwesterly <br /> direction. While the direction of tht. gradient has shifted <br /> slightly the gradient magnitude has fluctuated significantly with <br /> a minimum of .0047 ft/ft in January and a maximum of .023 ft/ft in <br /> February. It appears that the shallow groundwater at the site may i <br /> be responding to non-precipitation related effects including <br /> river/tidal stage and local pumping. The groundwater monitoring <br /> results are summarized in Table 2. <br /> Groundwater samples were collected from the six wells on March 7, <br /> 1991, for analysis of benzene, toluene, ethylbenzene, xylenes <br /> (BTEX) and total petroleum hydrocarbons as gasoline (TPHG), by EPA <br /> methods 8015/8020. In addition, monitoring well, MW1 was sampled <br /> for oil and grease by EPA method 5520 C G F. Sampling was done <br /> _ using dedicated pumps in each well. Applied Analytical (DOHS Cert. <br /> # 1211) performed the analyses. Laboratory results continue to <br /> show MW4 with moderate concentrations of gasoline hydrocarbons. <br /> Low concentrations of xylenes were recorded in MW5. Oil and grease <br /> _ ----concentrations were_.below--detectable- levels in MWl_.- The results --- - - . - - -- -- - - -- --- <br /> are summarized in 'Table 3, and the laboratory reports and <br /> chain-of-custody documentation are presented in attachment 1. <br /> 1710 MAIN STREET e ESCALON.CA 95320 • (209)838-3507 <br /> 2350-A WALSH AVENUE a SANTA CLARA,CA 95051 . (408)496.1249 <br />