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<br />Chevron Products Company 4
<br />Former Chevron Station #9-5775La01 West Kettleman Lane, Lodi, California October 9, 2009
<br />Quarterly Monitoring Data
<br />Quarterly groundwater monitoring and sampling at the site began in February of 1999,
<br />TPHg has been reported in monitoring wells MW -1, MW -3, MW -4, MW -5A, and
<br />MW -6 at concentrations ranging from 150 to 51,000 ug/l. In the most recent quarterly
<br />sampling event (second quarter 2000), TPHg was reported in monitoring wells MW -3,
<br />MW -5A, and EX -1 at concentrations of 220 ug/l, 67 ug/l, 1,290 ug/l, respectively.
<br />TPHg has not been reported in the deeper monitoring wells.
<br />Historically, benzene has been reported in monitoring wells MW -1, MW -3, MW -4,
<br />MW -5A, MW -6, and EX -1 at concentrations ranging from 0.72 to 39,000 ug/1. During
<br />the most recent quarterly sampling event, benzene was reported in monitoring wells
<br />MW -3, MW -5A, MW -6, and EX -1 at concentrations of 8.3 ug/l, 0.73 ug/l, 0.57 ug/l,
<br />455 ug/l, respectively. Benzene has not been reported in the deep monitoring wells at
<br />the site,
<br />Concentrations of MtBE have been reported in monitoring wells MW -1, MW -3, MW -4,
<br />MW -5A, MW -6, MW -8, MW -9A, and EX -1 at concentrations ranging from 2.75 to
<br />720,000 ug/l. During the most recent quarterly sampling event (July 24, 2000),
<br />concentrations of MtBE were reported in shallow and deep monitoring wells MW -3,
<br />MW -4, MW -5A, MW -5B, MW -6, MW -9A, MW -10B, MW-14/EX-2, and EX -1 at
<br />reported concentrations of 30 ug/l, 1,900 ug/l, 810 ug/l, 170 ug/l, 3.5 ug/l, 5.8 ug/l,
<br />' 2,100 ug/l, and 197,000 ug/l, respectively.
<br />Historical monitoring data from these wells indicate that groundwater at this site has
<br />been measured between 54 to 59 feet bgs. Groundwater flow has generally been
<br />reported to the west-southwest, south, and southeast. Quarterly monitoring and
<br />sampling, as well as soil vapor extraction and groundwater extraction is ongoing at the
<br />site.
<br />SITE GEOLOGY AND HYDROGEOLOGY
<br />The site is relatively flat and is situated approximately 42 feet above mean sea level
<br />(MSL). Soil in the vicinity of the site consists of Pliocene to Holocene continental
<br />rocks and deposits consisting of heterogeneous mix of generally poorly sorted clay, silt,
<br />sand, and gravel (R.W. Page, 1986). The nearest surface water is South Main Canal,
<br />located approximately 0.75 miles west of the site. Pixley Slough is located
<br />approximately 2.5 miles north of the subject site.
<br />Based on observations during drilling activities, the site vicinity is underlain primarily
<br />by silty sands and sandy silts in varying amounts. Soil encountered consists primarily
<br />of near surface sandy silts, extending in some locations to 35 feet bgs, with
<br />discontinuous sand and clay lenses. The sandy silt layer is underlain by a silty sand
<br />layer, which in some locations extends to 43 feet bgs. A sandy silt to clayey silt layer
<br />was encountered in some locations extending to a depth of approximately 55 feet bgs.
<br />077.41991.04319-5775 W P t 00900.doe
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