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- � CpeologuaC?ecFcnus Inc ,- -- -- - - - - - - - _ --- Page 6 <br /> Groundwater Monitonng Report <br /> Project No 425 2 <br /> 1 <br /> February 17,2000 <br />' On December 22, 1999, American Valley Waste Oil, under the supervision of Del Tech, <br /> picked up 250 gallons of well purge water and transported it to Industrial Services Oil Co , <br />' Inc of Los Angels, CA A manifest is included in Appendix D <br /> 3.0 CONCLUSIONS AND RECOMMENDATIONS <br />' The following conclusions have been drawn regarding the status of the groundwater at this <br /> site and recommendations for future work <br />' Conclusions <br />' 1 The water table groundwater gradient historically flows in a northern direction at about <br /> 0 002 ft/ft However, over the past year and a half, the gradient has shifted towards the <br /> east The cause for this is not known at this time <br /> 2 Vertical groundwater gradients have been found to be flowing upward during early spring <br /> and downward during late spring and summer This may be do to the annual cycle of <br /> groundwater pumping needs of the community The upward flow of groundwater during <br />' certain portions of the year may be responsible for preventing these contaminants from <br /> significantly impacting the deeper aquifer zones <br /> 3 The concentrations of these petroleum compounds in the groundwater appear to be stable <br /> and not decreasing at a significant rate at all <br /> 4 The shallow water table groundwater plume is laterally defined except to the west <br /> 5 Free-floating gasoline was not present in MW-2 in September and only droplets in <br /> December 1999, but typically is present in late fall and winter months <br /> 6 Petroleum hydrocarbons concentrations in the groundwater at the site appear to fluctuate <br /> with each monitoring event <br /> 7 It appears that the deeper groundwater gradient is defined vertically since MW-102 and <br /> MW-202 is now non-detect <br /> 8 The domestic wells associated with this site remain non-detect <br /> 9 With several domestic wells associated with the residence surrounding the property and <br /> the wells for the elementary school located a short distance northeast of this property, this <br />' groundwater plume appears to continue to pose a significant threat to public health and <br /> the environment <br /> Recommendations <br />' The following recommendations are made <br /> 1 The 12 monitoring wells and 3 domestic wells should be sampled for natural attenuation <br /> parameters during future monitoring events so it may be determined if remediation by <br /> natural attenuation is occurring <br /> 2 The high concentration of contaminants at the source should be removed to provide <br /> protection to surrounding water wells, facility natural attenuation, and to achieve closure <br />