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Geolo ccal TecFir�ccs Inc Page 2-=— --� - ----- <br /> g <br /> Groundwater Monitoring Report <br /> Project No 425 2 <br /> January 25, 2002 <br />' A summary of findings include <br /> 1 Hydrogeology <br /> • The predominant groundwater gradient direction for the shallow aquifer was to the <br /> north from May 1995 to May 1998 After this period the direction has trended to the <br /> -northeast For both of the-December 2001 events the direction was calculated to be <br />' northeast which is consistent with historical data <br /> • The predominant groundwater gradient direction for the intermediate depth aquifer <br /> is towards the east-northeast For the December 3, 2001 event the direction was <br /> ' calculated to be north and this is anomalous when compared to the historical site <br /> data For the December 21 event, the direction was to the east-northeast and this is <br /> consistent with historical site data <br /> Vertical groundwater gradients do exist at the site and range from 2 to 20 times the <br /> - magnitude of the horizontal gradient At times the site has experienced both a <br /> ' negative and positive vertical gradient No clear trend has been recognized to <br /> account for these differences, but variations in community groundwater pumping <br /> and rainfall may be causal factors Thus, during low pumping demand, the vertical <br /> ' groundwater gradient would be expected to be upward, and the inverse would also <br /> be expected The vertical gradient was positive or upward for both of the December <br /> 2001 monitoring events <br /> 2 Groundwater Contamination <br /> C TPH-G contaminant concentrations have decreased in well MW-2 since the June <br /> 2001 event The impacted soils in the vicinity of the former USTs were excavated in <br /> July 2001 The decrease is probably the result of the reduction of available mass to <br /> leach to groundwater after the excavation project in July 2001 Additional <br /> ' monitoring is required to determine contaminant trends <br /> o All of the deep-screened wells (MW-102, MW-105 MW-107 and MW-202) were <br /> non-detect for the event This is the fifth consecutive event for this condition <br /> ' O The domestic wells associated with the site were non-detect for all constituents <br /> 1.0 GROUNDWATER MONITORING <br /> 1.1 Hydrology of Site <br /> ' 1.1.1 Horizontal Groundwater Gradients <br /> ' The average water table elevation at the site on December 3, 2001 was 71 70 feet above <br /> mean sea level This represents a decrease of 0 54 feet since the September 2001 <br /> monitoring event The water table groundwater gradient was 0 001 ft/ft flowing N48°E <br />