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E PARTMENT <br /> ENVIRONMENTAL HEALTH � <br /> PQuit <br /> !M AN JOAQUIN COUNTY Unit supervisors <br /> S <br /> �.•—,�_ '�94 Carl Borgman,R.E.H.S. <br /> �i <br /> Aonna K.lieran,R E.Hs. 304 East Weber Avenue,#Third,Floor Mike Huggins,R.E.H.S.,R.D.I. <br /> Director Douglas W.Wilson,R.E.H.S. <br /> AI Oisen,R.E.H.S. Stockton, California 95202-270 <br /> ., -j .P• Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> iii fi oda Laurie A.Cotulla,R.E.H.S. Robert M rcell on, .E.H. S. <br /> Fax: (209} 464 013$ I MarkBarcelios,R.;J.H.S. <br /> Program Manager <br /> 8 2004 <br /> MARTIN HARRIS <br /> 5151 ALMONDWOOD DRIVE o. <br /> MANTECA CA 95337 <br /> Bo Trailers , SITE CODE: 1424 <br /> RE: Tuff y <br /> 5151 Almondwood Drive M t' <br /> Manteca CA 95337 '' <br /> Count Environmental Health Department�(SJCIEHD} has reviewed <br /> San Joaquin Y 004 and <br /> i4 <br /> Additional Subsurface Investigation Summary Report (Report) dated April 27, 2 <br /> the first and second quarter 2004 Groundwater <br /> rouG�oundrZero}toring Reports,.ari'd has the following ttcommentsr <br /> Zero your <br /> behalf by Ground Z Analysis, I <br /> The Report documents a site investigation that took place during anary 4.' a soil .; <br /> boring (SB-4) and three additional groundwater monitoring ( rtical and lateral extent <br /> MW-7)were installed onsiMW- <br /> te to continue the investigation of the ve <br /> of the contamination at your site. The report concludes, based on the findings of the <br /> investigation, that the vertical extent of the groundwater contamination has been defined, <br /> and that the lateral extent has been "essentially" defined, though detections of methyl <br /> tertiary butyl ether (MtBE) are reported in the furthest down-gradient wells. <br /> Soil boring S13-4 was advanced by direct push drilling cone enetrometor <br /> method. A p test <br /> boring was advanced first, which was proposed to be advanced to approximately 75 feet <br /> below surface grade (bsg) but extended to only 35 feet bsg. 'Two groundwater samples <br /> were collected from boring SB-4, one at 22-26 feet bsg, and one at 31-35 feet bsg. The <br /> shallow sample contained MtBE at 5.2 micrograms per liter (µgll); the deeper sample was <br /> non-detect for all constituents analyzed. This appears Ito indicate that vertical migration of <br /> the plume near the source area has been limited, but f6rther�i investigation at depth further <br /> from the source area would provide more conclusive evidence of vertical delineation of the <br /> plume, especially considering that the total depth and construction details of the onsite <br /> domestic well, which is located approximately 180 feet from the source area, remain <br /> 'i <br /> unknown. 1 <br /> The new monitoring wells were initially sampled on January 23, 2004, and have <br /> subsequently been sampled at two routine quarterly groundwater monitoring and sampling <br /> events. Reported analytical results from the quarterly events show increasing trends in <br /> the concentrations of MtBE in monitoring wells MW-1,I MW-3 and MW-5, though <br /> concentrations are currently below the primary maximum contaminant level. However, <br /> risk analysis performed by Ground Zero (Ground Zer61 document dated October 3, 2002) <br /> predicted that both the onsite domestic well and the closest offsite domestic well would <br /> eventually be impacted by the plume. That analysis was performed using an average <br /> concentration of MtBE from MW-1 of 8.6 µg11; the average concentration of MtBE in MW-1 <br /> is now 9.9 µg11. The average concentration of MtBE in MW'5, which is located <br /> approximately 70 feet down gradient from MW-1, is 6'3 µg/l, and that of MW-3 is 5.8 µg11. <br /> li, �E <br />