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Report-Pilot Remed,al System Test Page 3 Former Manna Pro Site Project No 207 3 • July 3 I,2000 converted to groundwater monitoring wells Between 1993 and 1996, Groundwater Technology Inc (GTI) installed four additional monitoring wells, a combination ' groundwater/vapor extraction well and three observation wells These observation wells were used for the completion of a simultaneous groundwater pumping and vapor extraction pilot test In 1996, GTI conducted a feasibility study which included pilot level ' field work to test several remedial options The GTI report concluded that a combination of vapor extraction and groundwater pumping offered the most attractive option for remediation of the gasoline plume at this site Up until April of this year, a total of eleven groundwater monitoring wells, three observation wells, and one combination groundwater and vapor extraction well have been ' constructed on or near the Manna Pro site In April of 2000, concurrently with some of the field work documented in this report, Geo-Phase Environmental drilled and constructed a 97 foot deep monitoring well intended to investigate the vertical ' distribution of gasoline hydrocarbons A 55 foot deep air sparge well, a 50 foot deep vapor extraction well, a 50 foot soil boring backfilled with Oxygen Releasing Compound ' and two 30 foot air monitoring wells were also installed at this time 1.2 Scope of Work lie The goal of the work described herein was to develop new engineering data by conducting a pilot study, to be used later in conjunction with previously existing data, especially that developed by GTI in their Pilot Testing Report and Conceptual Corrective Action Plan The data will be used produce a technical data base adequate to identify the most feasible and cost effective method to adequately mitigate the residual soil and groundwater contamination at the former Manna Pro facility The Feasibility Study, which will follow this current report, will compare several alternatives for remedial action and determine which methods should be used to generate the final Remedial ' Action Plan (RAP) The pilot work, described in the following sections, was completed pursuant to a directive of the San Joaquin County PHSIEHD dated June 23, 1999 ' 1.2.1 Conceptual Basis Past work performed by Groundwater Technology Inc (GTI) documented pilot level field rtesting of a remedial concept involving simultaneous vapor extraction and groundwater pumping This work provides some of the basis for the recently completed additional ' pilot testing work needed to complete a Feasibility Study In recent years, groundwater at the site has been recorded at historically high levels The surface of groundwater has recently been as high as 25 feet bgs, but as late as 1994, the groundwater surface was as low as 40 feet bgs This rise in groundwater elevation was • 2937 Veneman Ave , #13240 Geo-Phase Environmental Inc Phone(209) 569-0293 Modesto,CA 95356 Fax(209)569-0295 r