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S ECOR -- Ms Margaret Lagorio May 2, 2005 Page 2 Scope of Work The purpose of this IRAP revision is to develop a work plan to evaluate the feasibility of groundwater extraction as an interim control measure to prohibit MTBE from moving further laterally downgradient of the Site. The first step in this work plan would be to conduct a pump test, as requested in SJCEHD's letter(3/16/05), on wells MW-2, MW-3, and MWO- 1X. This pump test would be used to calculate transmissivity, hydraulic conductivity, and storativity, so that the feasibility of groundwater extraction as an interim remedial action measure could be evaluated. To conduct the pump test, SECOR would perform the following tasks: Task 1: Pre-Field Activities SECOR will ensure a Health and Safety Plan has been developed and is current for the Site. SECOR will also secure the equipment necessary to complete pumping tests, including a variable rate submersible pump and pressure transducers /data loggers for each well that will be monitored. SECOR will also obtain the equipment and permits necessary to collect and if necessary discharge pumped groundwater. i Task 2: Conduct Step Drawdown Tests in MW-2, MW-3, and MWO-1X A step drawdown test will be conducted for MW-2, MW-3, and MWO-1X. In a step drawdown test, groundwater is pumped from a well at a set flow rate and over a specified amount of time. Drawdown in the well is measured; if drawdown does not initially occur, then the pumping rate is increased until drawdown to a constant, specified level is achieved. The flow rate used to achieve the desired drawdown is applied for the constant rate pumping test. This test provides information about the potential capture zone of the potential groundwater extraction system for each well tested, and the feasibility of using groundwater extraction as an interim remedial action measure. SECOR will conduct a test for each well at a minimum of three flow steps. SECOR anticipates each test will take approximately one hour. Task 3: Conduct Constant Rate Pump Tests on MW-2 and MW-3, and MWO-1X. A constant rate pumping test is used to derive aquifer parameters that will be used to quantify plume capture if groundwater extraction and treatment is chosen as an interim remedial action measure. In this test, groundwater is extracted at a rate chosen on the basis of the step drawdown test over a set period of time for each well. In this case, SECOR proposes to extract groundwater over a period of six hours from each well. During the test, groundwater levels are measured at the pumped well as well as at wells surrounding the pumped well. The difference in drawdown between the pumped and monitored wells is used to estimated transmissivity, storativity, and hydraulic conductivity of the aquifer. Wells MW-2, MW-3, and MWO-1X will be tested separately. MTBE will be sampled in each pumped well prior to, in the middle of, and after the pump test. MTBE concentrations will be evaluated to determine whether concentrations remain constant or decrease during the pump test, which will help determine the potential effectiveness of groundwater extraction as an interim remedial alternative. JTP_IRAP_V01.doc CADocuments and semngsusaxWy Documents\05-04\Joe's Truck Stop\IRAP\JTP_IRAP_V01.doc