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.:- z MWOy _ _--. �' ' ,e:t ; 1 •;ei a ,� `h -'asA� �^ - `sxL-" `,� f <br /> h <br /> s. <br /> Quarterly Ground-Water Monitoring March 8, 1989 <br /> Beacon Station No. 3-492, Manteca, California AGS 86102-3 <br /> At the request of Beacon, Applied GeoSystems began quarterly <br /> monitoring of ground water in monitoring wells MW--1 through MW-3 <br /> in May 1987. Because free product was observed in a sample of <br /> ground water collected from well MW-1 during the September 1988 <br /> monitoring event, Applied GeoSystems recommended that subjective <br /> analyses of ground water and removal of free product be performed <br /> on a monthly '.asis (AGS Report No. 86102-3, dated January 31, <br /> 1989) . <br /> A geologist from Applied GeoSystems was present at the site on <br /> October 21, November 16, December 5, and December 20, 1988, to <br /> measure the depth to water and thickness of any free product, <br /> perform subjective analyses of ground water samples, and remove <br /> any free product observed in monitoring wells MW-1, MW-2, and <br /> MW-3. The depth to ground water and thickness of free product in <br /> well MW-1 were measured to the nearest 0.01-foot with an <br /> interface probe manufactured by Oil Recovery Systems. The depth <br /> to water in wells MW-2 and MW-3 were measured to the nearest <br /> 0.01-foot with a Solinst water level indicator. Samples of <br /> ground water were then collected from the air-fluid interface in <br /> each well for subjective analysis by lowering approximately half <br /> the length of a clean Teflon bailer through the interface. The <br /> bailer was retrieved and the water sample examined for free <br /> f product, sheen, or other subjective evidence of hydrocarbon <br /> contamination. Results of these and previous subjective analyses <br /> are summarized in Table .1. The.thzckness. of .free;:product <br /> measured in well''MW,1°varied from 0.03-inchta= 0 25minbh. from <br /> September ,6;:.to December 5. ' 1988, 'on December 20;; 1988 a <br /> measurable thi'ekness of free product was not present in the well, <br /> and free product was not observed in the water;sample collected <br /> for subjective analysis. No free product 'or other `subjective­" <br /> evidence of contamination has been observed in water samples from <br /> wells MW-2 and MW.-3 <br /> ' On December 5, 1988, ground-water samples were collected from the <br /> monitoring wells for laboratory analyses. Prior to sample <br /> collection, a minimum of 51 gallons (approximately 3 well <br /> volumes) of ground water was purged from each monitoring well <br /> 9 using an electric submersible pump; that volume was sufficient to <br /> produce stable temperature, pH, and conductivity measurements on <br /> t field instruments. After the wells were allowed to recover to <br /> static levels, ground-water samples were collected by lowering a <br /> clean Teflon bailer through the air-water. interface. The bailer <br /> was retrieved-and-the-_samples-were-transferred_-to-laboratory-------- --- -- - - -- ------- . ------ <br /> cleaned, 40-milliliter glass vials which contained concentrated <br /> hydrochloric acid as a preservative. The vials were completely <br /> ti <br /> filled thereby eliminating headspace. Three blank method samples <br /> 2 <br /> � ,Q�pll�c� (se��ystgr�s <br /> INNNIII milli <br />