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INTERIM REMEDIAL ACTION PLAN <br /> 4491 West Durham Ferry Road <br /> Tracy, CaLforrua <br /> Delta Project No 40-91-732 <br /> Page 11 <br /> The air biofiltration alternative was selected because initial site data indicate that hydrocarbon <br /> concentrations in the soil vapor will be relatively low In addition, this alternative was selected because <br /> of the relatively small capital investment and small operation and maintenance costs Biofiltration <br /> operation and maintenance costs can be less than one-tenth of the other air treatment options previously <br /> discussed Total operation and maintenance costs usually range from $0 50 to $1 50 per 100,000 cubic <br /> feet of air treated. <br /> 5.2 Ground Water Remediation <br /> A ground water treatment system is not proposed at this time because the extent of the plume of <br /> petroleum hydrocarbons has not been defined Also, it is believed that hydrocarbons in ground water <br /> may be reduced by insitu soil vapor extraction By applying a vacuum to the soils, the pressure above <br /> the ground water table is reduced which in turn increases the volatilization rate of the dissolved <br /> hydrocarbons In addition, oxygen is introduced into the surrounding soils which increases natural <br /> bioactivity and in turn increases the biodegradation of the dissolved hydrocarbons in the ground water <br /> Quarterly monitoring of the hydrocarbon concentrations in the ground water should confirm ground water <br /> quality trends <br /> 6.0 RECOMMENDED FUTURE WORK <br /> Delta recommends that the preparation of a SVE well installation work plan and procurement of SVE well <br /> permits under Phase I of the protect be completed next Once this has been completed, the SVE wells <br /> should be installed and an SVE test be conducted to Help design the interim SVE system Delta also <br /> recommends that the extent of the petroleum hydrocarbon plume in ground water be defined by <br /> installation of additional monitoring wells A Problem Assessment Report (PAR) should be prepared after <br /> ' the extent of petroleum hydrocarbons in soil and ground water have been defined Table 5 shows a <br /> chronological approach at approximating the times of task completion for future work under Phase I <br /> ' RPT045 TA <br />