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Mr. Philip Isorena Proposal P93-040.31 <br /> July 12, 1993 <br /> Page 10 <br /> Bail down tests are a method for determining true thickness of the mobile hydrocarbon <br /> layer in the formation from monitoring wells. These tests are performed because generally <br /> the thickness of free product observed in a well is significantly greater than the actual <br /> thickness of free product in the formation. Data from the recovery portion of the bail <br /> down tests can also be used to determine potential product recovery rates for evaluating <br /> the effectiveness of floating product recovery methods. <br /> The bail down tests will be conducted in monitoring wells containing free product <br /> according to the Hughes method. The method entails bailing or pumping product from a <br /> well (without removing water) until significant drawdown of product is achieved. After <br /> it is bailed, product in the well should recover at a constant rate until the elevation of <br /> product in the well is equal to the elevation of the base of the mobile hydrocarbon layer <br /> in the formation. After this elevation is reached, each increment of recovery reduces the <br /> product driving head; therefore, recovery continues at a constantly decreasing rate. The <br /> recovery of product level versus time is recorded and the data are plotted on an arithmetic <br /> graph. The recovery graph should consist of two sections: (1) a linear section representing <br /> a constant recovery rate and (2) a curvilinear section representing a constantly decreasing <br /> recovery rate. The corresponding elevation point on the graph where linear (constant) <br /> recovery ends and curvilinear (decreasing) recovery begins represents the base of the <br /> mobile hydrocarbon layer. This method is valid only if the base of the mobile <br /> hydrocarbon layer is above the groundwater potentiometric surface. <br /> Product generated during the bail down tests will be drummed in a 55-gallon drum. <br /> EMCON will assist the STTC in arranging for appropriate disposal. <br /> Task 11. Interim Product Recovery <br /> The STTC proposes to install passive product recovery devices in groundwater monitoring <br /> wells containing measurable free product (>0.01 foot). The latest data from the synoptic <br /> monitoring event (September 1993) conducted during the interim pollution assessment <br /> study indicate that five wells contain a measurable amount of floating product (September <br /> 1992). The actual number of wells to be included in the product recovery program will <br /> be determined after the fust monthly water level monitoring event. Free product will be <br /> recovered using passive skimming devices consisting of a tube-shaped <br /> petroleum-absorbing material encased in a perforated polyvinyl chloride canister. The <br /> devices will be suspended on a nylon cord in wells containing free product. The devices <br /> will be inspected and changed out if needed during the monthly synoptic water level <br /> monitoring events. <br /> SAGPROT93"304031.bc-93 1mc:5 <br />