ARCHIVED REPORTS_XR0005099 - Laserfiche WebLink

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3 0 CONCLUSIONS, RECOMMENDATIONS AND PROJECT STATUS Between December 17, 2001 and March 19, 2002, the groundwater surface beneath the site ' rose an average of 2 75 feet, the groundwater flow direction shifted approximately 20 degrees to the west, and the groundwater gradient increased slightly from 0 0011 to 0 0012 foottfoot ' Between March 19 and June 26, 2002, the groundwater surface beneath the site dropped an average of 4 18 feet, the groundwater flow direction shifted approximately 5 degrees to the ' northwest, and the groundwater gradient remained constant at 0 0012 foot/foot Concentrations of petroleum hydrocarbons detected in groundwater, including TPH-as-diesel, TPH-as-gasoline and BTEX compounds, remained relatively constant between December 2001, March 2002 and June 2002 The oxygenate compounds and 1,2-DCA continued to be below laboratory detection limits Since the three monitoring wells were installed in December 2000, the concentrations of petroleum hydrocarbons in groundwater have generally declined, probably in response to source removal and natural attenuation processes Given that petroleum hydrocarbon concentrations in groundwater and groundwater flow direction and gradient appear to be stable, benzene concentrations appear to be relatively low (maximum concentration of 32 µg/l in June 2002), oxygenate compounds and 1,2-DCA are below detection limits, and no sensitive receptors appear to be threatened, Ramage Environmental recommends that the groundwater monitoring and sampling frequency be reduced from quarterly to semi-annually On July 16, 2001, Ramage Environmental published Work Plan, Additional Site Investigation PHS/EHD approved the work plan on July 25, 2001 Currently, implementation of the approved ' scope of work is pending an encroachment permit approval from the city of Manteca Approval of the encroachment permit is expected during October 2002 1 10