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m Mr.James Barton,RWQCB May 14, 2008 Work Plan for Additional Site Assessment Former Dolly Madison Bakery,Stockton,California Page 8 impact, Stratus is proposing to complete three additional groundwater monitoring wells (MW-17 through MW-19) to-' this interval of the subsurface. Since MW-17 through MW-19 will be situated outside of the known area of petroleum hydrocarbon impact to shallow groundwater, installation using the hollow stem auger drilling method (instead of the sonic method used to complete MW-8,MW-9, and MW-14) is proposed. In March 2008, Stratus completed'a pilot test to evaluate use of soil vapor extraction(SVE) and air sparging (AS) to mitigate petroleum hydrocarbon impact to vadose zone soil and shallow groundwater. The results of the pilot test indicate that SVE and AS appear to be viable remedial alternatives for remediating shallow-petroleum hydrocarbon impact to the subject property: A report documenting this pilot test will be submitted in May 2008. The report will recommend that an SVE/AS remedial system be installed at the site. Stratus is proposing to install three additional vapor extraction wells (VW-4 through VW-6) and three additional air sparge wells (AS-2 through AS-4) during this phase of investigation at the site. Installation of the vapor extraction and air sparge wells at this time will eliminate the need for separate mobilizations of drilling equipment to the,site prior to initiating remedial efforts, and may reduce the time needed to begin mitigation of impact to the shallow -subsurface. SCOPE OF WORK i The objectives of the proposed scope of work are to: • Further assess the lateral and vertical extent of petroleum hydrocarbon impact to the subsurface. • Furthercharacterize the geology beneath the site. • Install additional remediation wells during this phase of investigation.for future use in SVE/AS remediation. • If required by the City of Stockton,properly destroy well MW-3. To accomplish these objectives, Stratus is proposing the following work activities: •. Drill and install two (2) groundwater monitoring wells (MW-15 and MW-16) to approximately 35 feet bgs using the hollow stem auger drilling method. • Drill and install three (3) vapor extraction wells (VW-4 through VW-6) to approximately 25 feet bgs using the hollow stem auger drilling method. • Drill and install three (3) air sparge wells (AS-2 through AS-4)to approximately 32 feet bgs using the hollow stem auger drilling method. KATimotby Kong Propert-y\Work Plans\Kong_rnayn$worimlan.doc