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' t of the impacted soil remains within the capillary impacted soil remains at the site Most p l r p ry fringe or phreatic(saturated) zone. It is likely that groundwater will remain impacted as long as the impacted soil remains at the site 5.4 Remediation of Impacted Soil There are two options for remediation of the remaining petroleum hydrocarbon impacted soil excavation and in-situ remediation If the remaining impacted soil is excavated, the overburden soil, approximately 5 feet, would be set aside and used for backfill material This would allow the removal of most of the remaining impacted soil The impacted soil would ' then be removed and disposed The limits of excavation would be constricted by the property boundaries to the north and west, and the building to the east Monitonng well MW-1 would be destroyed in this process This well would have to be replaced The ' excavation should also be dewatered at least once (preferable twice), therefore facilitating groundwater remediation This would also reduce overall dissolved phase petroleum hydrocarbons in the groundwater ' Options for in-situ remediation of soil include vapor extraction/air s ar iii and P P P g g ' bioremediation Additional wells, some located off-site to the west, would need to be installed for either of these alternatives Soil at this site has a high clay content, which would make vapor extraction difficult Vapor extraction is not efficient in the remediation of diesel range compounds However, gasoline range compounds are prominent at this site Air sparging/vapor extraction would help in the remediation of groundwater In-situ bioremediation is capable of remediation of both diesel and gasoline range compounds in ' soil and water Excavation and disposal of impacted soil could likely be completed within 30 to 60 days of ' removal of the impacted soil, in-situ methods of remediation routinely requires between 6 months and two year treatment periods ' Depending upon the specific method, costs of in-situ treatment for a site of this size can range from $50,000 to $100,000 Excavation and disposal of approximately 400 cubic yards of impacted soil, based upon previous costs at the site, could range from $35,000 to $60,000, ' including backfill material Additionally, MW-1 would have to be replaced However, until the exact volume and concentration of impacted soil is known, these costs could vary greatly IIf the current occupant at the site is not opposed to the disturbance created by excavation, we recommend excavation and disposal of the impacted soil However, if excavation of the impacted soil will impair operations, we recommend that a vapor extraction test be initiated ' to determine the viability of vapor extraction at the site o..lnral And.S C i.c. QRJ"9VMI S I 1 r