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. 6.2 Recommendations Based on the data presented in this report, SEACOR recommends the use of vapor extraction in conjunction with dewatering and treating groundwater, unless an air sparging feasibility study indicates that the combination of groundwater sparging and vapor extraction is a more viable approach 6 2 1 Groundwater Extraction and Treatment According to the data collected during the aquifer pump test, hydraulic conductivity appears to be low, and therefore, likely incapable of producing enough groundwater to affect a successful pump and treat system A possibility remains that the monitor well MWI used for the pump test was damaged or impaired to a degree which could have inhibited the flow of groundwater Before ruling out pumping and treating groundwater at the site, monitor well MW4 should be thoroughly developed and pumped excessively during a quarterly monitoring event to substantiate the apparent poor hydraulic conductivity of the groundwater-bearing zone Drawdown and recharge rates recorded during excessive pumping of this well will confirm the pump test data or indicate that an additional pump test should be performed using a well other than MW1 6 2 2 Soil Vapor Extraction Soil vapor extraction is recommended for use as a remedial technology at the site to remove petroleum hydrocarbons in the range of gasoline from the vadose zone and capillary fringe zone soils Contaminants can be removed from the capillary fringe zone best if a vacuum is applied while dewatering this zone Vapor extraction will affect a subordinate amount of groundwater remediation during the removal of hydrocarbons from the vadose zone Dewatering will expose the capillary fringe zone to allow vapor extraction Treatment of the water generated during dewatering will need to be conducted onsite using a groundwater filtration and purification system Vapor extraction alone however, will not remove the dissolved fraction of hydrocarbons detected in the groundwater beneath the site A combination of technologies will likely be required, therefore, to successfully meet the remediation goals set for the site We recommend soil vapor extraction in conjunction with either groundwater air sparging or groundwater pump and treat (if determined to be suitable during a secondary aquifer pump test and quarterly monitoring observations) 6 2 3 Air Spargmg It is our recommendation that an interim feasibility study for groundwater air sparging be conducted prior to initiating remedial action at the site This test will require the installation of a minimum of three sparge points Data collected during the air sparging pilot test should be used to assess the vapor conductivities and zones of influence Three temporary sparge wells should be installed in locations selected (if possible) to be incorporated into the final remedial system A positive displacement blower equipped with a pressure meter and anemometer should be used to perform the • SEACOR 014-01 1 par 21