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Ge0kgwdTechn ws Znc Page 4 Groundwater Monitoring Report Project No 281 2 December 18, 1996 Conclusions 1 Relatively elevated concentrations of petroleum hydrocarbons is present in two of the three monitoring wells 2 Free floating gasoline is present in MW-2, which is on the edge of the property down gradient of the former tank location 3 Groundwater gradient flows in a northern direction at about 0 024 ft/ft 4 Two domestic water wells are located within about 150 feet down gradient from MW-2 5 MTBE was tested for but not confirmed So we are not sure if it is present or not 6 With residence all around the property and an elementary school located a short distance northeast of this property, this groundwater plume appears to pose a significant threat to public health and the environment Recommendations The following recommendations are made 1 Place the site on monthly groundwater level measurements to complete an annual cycle of groundwater gradient calculations and a quarterly groundwater monitoring schedule The next monitoring event is scheduled for the first part of January 1997 2 The three domestic water wells tested in September of 1996 should also be included in the quarterly monitoring routine and the results of these tests should be forwarded to the respective home owner 3 Test the monitoring well water samples for MTBE and confirm its presents by testing by method 8260 Also test these samples for dissolved oxygen (DO) and oxidation- reduction-potential (ORP), m addition to the standard field water quality measurements of temperature,pH, and conductivity 4 If free product appears in any of the wells in the future, continue removing that material by hand bailing methods 5 Additional site characterization work should be implemented immediately The following approach is recommended. o Perform an exploratory soil gas survey (SGS) using the Gore Passive SGS method The purpose for this work is to define the lateral extent of the high level of gasoline impacted areas and the areas that have lower concentrations of gasoline o Perform a receptor survey (including a water well survey within a 200 foot radius of the site) o This information would then be used to propose location and construction of additional groundwater monitoring well installation The goal of these additional wells would be to define the lateral and vertical extent of groundwater impacted by this gasoline and to have sentinel wells located between the high levels of contamination and the domestic wells that are located in the immediate area of the site 6 After this information is gathered, a fate and transport analysis and risk evaluation should be performed 7 The site can then be evaluated for the need for engineered remediation 1