SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Frontier Transportation c. 425 Larch Road Page 2 of 3 excavated soil weight (1200 to 1500 tons) that the excavation could be as deep as 27 feet(if soil weight is 125 pounds per cubic foot). Analytical data from soil samples on your site demonstrate that most contaminant mass is at approximately 10 feet below surface grade (bsg) and that little contaminant remains in soil at 15 feet bsg, with the possible exception of the former tank pit excavation area where impacted soil was present at 14 feet bsg. Effective use of excavation is not always to remove all traces of the contaminant, but to remove enough significantly impacted soil as to greatly reduce rate of contaminant transfer from soil to water(flux rate),thereby reducing the work load for the technology selected to remediate groundwater directly, such as ozone injection. It may be possible to significantly reduce the sorbed contaminant mass by use of excavation to such depth as can be achieved in the former tank pit area without demolition of the building or use of expensive shoring. In EHD's experience, fine-grained soil, such as occurs to a depth of approximately 20 feet bsg on your site, may maintain fairly steep slopes without shoring, although this should be evaluated by a properly qualified engineer. The potential effectiveness of partial excavation perhaps combined with a separate approach for direct groundwater remediation should be evaluated. • EHD can conceive of no significant potential benefit to the use of neutron logging of the wells. To date, at least 28 borings have been advanced on your site with soil samples generally collected at 5-foot intervals. The samples were directly observed and described on boring logs. At least 18 borings were advanced and samples logged under the direction of one of your current consultants, Mr. Jazmin. A geophysical sensing of the borings will not refine the lithology of the site beyond what has already been directly observed, and indeed, neutron logs cannot directly determine lithology. Neutron logging is sensitive to water and can give `moisture measurements' if properly corrected, but EHD fails to see the usefulness of this; with the lithology known and assumed to be fully saturated below the water table, the moisture content will equal the porosity. A table of average porosity values was included in the back of the ICAP. Further refinement of this is of dubious value as the critical element for ozone contacting contaminants is permeability of the soil, and permeability generally has no direct relationship to porosity and cannot be determined from neutron logs. EHD has no knowledge of how "neutron logs supplemented by soil gas analysis will determine the radius of influence of the injected ozone and increased bioactivity resulting from the injection process as well as direct oxidation of the MTBE"beyond what the soil gas data will or will not show independently. EHD will not approve the use of neutron logging of the wells unless authoritative, peer-reviewed publications are provided to EHD that clearly demonstrate the claimed beneficial applications. With groundwater commonly approximately 10 feet bsg and the former tank pit area excavated to 14 feet bsg, EHD concurs with the conclusion that soil vapor extraction is unlikely to be of benefit. An aquifer test, if conducted to determine the hydrologic