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__y IRRI 111111 g lip APDL-NDIX 4 ADDITIONAL SCOPE OF WORK Brown and Caldwell (DC)recornmends the following additional work: - I. S(ratigraplt-te Study. Lithologic information from existing well logs and geologic cross sections for the local and regional area will be analyzed. The purpose of this analysis is to determine the stratigraphic interconnection between the aquifers underlying the area. Any thick, continuous clay zone(s) that might block vertical migration of groundwater will be identified. In addition, an analysis of the regional stratigraphy may indicate whether agricultural pumping west of the City of Lodi (City) in the spring and summer months or pumping of nearby municipal wells might affect the extraction well's capture zone. T2. Extraction Well Installation. The extraction well will be located near monitoring Well W-2. This Iocation is close to the leak site and area of highest groundwater coniarnination. The extraction well will have a pumping rate of about 30 gallons per minute (gpm). The extraction well will be about 100 feet deep and will be screened from slightly above the water table to the total depth of the well. The exact depth of the extraction well will be dependent on the results of the e -: stratigraphic study. 3. Aquifer Testing. An aquifer test will be required to determine aquifer parameters, F � the pumping rate necessary to capture the contaminated plume, and the groundwater reinjection rate. The aquifer test will be used to detennine the p. following parameters. • Maximum yield of the aquifer • Transmissivity and permeability of the aquifer Storage coefficient of the aquifer r _ Drawdown at the extraction well Drawdown at the monitoring wells f t-� Additional sampling data on benzene,toluene,xylene(BTX)concentrations The aquifer test will entail installation of the extraction well, a 72-hour pump test ' t's with a mobile groundwater treatment system,and data interpretation. L Municipal Well 12 Pump Test. . Drawdown in the eight shallow monitoring wells will be measured while municipal well 12 (Well 12) pumps groundwater from she deeper aquifer into the City's storm sewer. This information will be important in establishing the degree of hydraulic communication between the deep and shallow i aquifers in the immediate vicinity of Well 12. Establishing the amount of hydraulic communication will aid the City in determining whether Well 12 can safely be -----returned-to-;service. BC recor-trnends sampling Well 12 during the pump test for - - - ----- - -- BTX:constituents (EPA Method 602). The C;ty's permission and cooperation will be t necessary to perform this pump test,to determine the pumping rate and duration of. rthe test, and to ensure that pumping of nearby municipal wells does not interfere 1 with the Well 12 pump test.