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0 • ADDITIONAL ASSESSMENT WORKPLAN JAMAR SERVICE,STOCKTON • APRIL 2002 The locations of all wells will be surveyed to latitude and longitude coordinates with an accuracy of 1 meter or less using a Leica GP50 Differential GPS receiver These data will be added to the site's database and be submitted electronically in accordance with the requirements of AB 2886 Aquifer Performance Test An APT will be completed on extraction well EW-1 to evaluate the aquifer characteristics to estimate the potential rate of transport away from the site through the groundwater The APT will be 6 to 8-hours and will be completed as a step drawdown test The step drawdown test will consist of pumping from the extraction well at a minimum of three different constant pumping rates below 5-gallons per minute(gpm),while monitoring the water level in the pumping well Each pumping rate will be maintained for a period that is equivalent to the product of 15 tines the borehole volume and the inverse of the pumping rate This will insure that the volume of water contained in the borehole will be removed within the first step and that water produced from the well will be released from the formation surrounding the well The groundwater pumping duration of the step drawdown test will be approximately 1-hour or until the water level in the pumping well stabilizes An electronic data logger or manual measurement using an electric water level indicator,will be used to chart the changes in water levels with time during the test A downhole submersible pump, capable of sustained pumping rates of approximately 5- gpm will be used in the pumping well Groundwater produced during the test will be pumped into a 1,500-gallon poly tank Water generated during this testing will be discharged as necessary following groundwater analysis Using the data collected,the hydraulic conductivity and sustained yield will be evaluated using the Bouwer and Rice Method Groundwater samples will be collected before the APT, after the APT is concluded and again after 24-hours The wells will not be purged prior to collecting the sample after 24- hours The groundwater samples will be analyzed for TPH G,TPH D, BTEX, 1,2-DCA, EDB, and fuel oxygenates using EPA Methods 8015M and 8260B,respectively Vapor Extraction Test A one day vapor extraction feasibility test will be conducted at the site on extraction well EW-1 Samples will be collected and analyzed for concentrations of TPH G and BTEX to establish pre-remediation concentrations A vacuum will be placed on extraction well EW- 1 and vacuum will be monitored at MW-1,MW-2 and MW-4 with a manometer during the VET. 11