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3A11-1G-'91 WED 12:09 I JAX TECHNOLOGIES TEL NO-.439 7`. 3 #493 P17 __... grade at temporary vapor probes installed for the remedial investigation, At the time of the investigation, groundwater was reported at a depth of approximately 48 to 58 feet below grade. Although a groundwater remediation program is to be initiated, and even if the groundwater at the site is fully remediated, hydrocarbons that remain in the Soil may migrate down to groundwater level with the passage of time, or groundwater may come in contact with hydrocarbon-impacted soil during periods of higher water table level , i .e. , during the winter Months of a normal rainfall year. Therefore, it is important to eliminate the hydrocarbon source in the soil . The current drought status provides an excellent opportunity to achieve remediation with minimal threat to the groundwater. In-Situ Vapor Extraction Soil Remediation System The greatest risks associated with this remediation alternative are the risks associated with use of heavy equipment during system underground installation procedures. However, since the project site is a vacant lot, public contact with the site should be minimal . Additional perceived risks associated with this technology are emissions of air ' pollutants and noise, Since the air emission levels will be regulated by county agencies, the levels emitted will not be a threat to public health. There will be no uncontrolled releases with the use of this technology. Should the noise generated during system operation prove an annoyance, the system equipment or equipment layout can be modified. The expected project duration using vapor extraction is 6 to 12 months. There are no other limitations associated with use of this technology. Soil Excavation and Disposal This remediation alternative has the greatest risks associated with it. There are major hazards to the public and field technicians associated with excavation of large quantities of soil : use of heavy equipment, danger of the sidewalls of the excavation pit collapsing, transporting large quantities of soil , and the open pit resulting from the excavation. Although public contact with the project site will be minimal and chain link fencing will secure the excavated area, the danger remains until the project is completed, and the excavated area is backfilled and compacted. The environmental hazards associated with this alternative include: uncontrolled vapor releases from the exposed soil to the environment and the possibility that not all of the hydrocarbon impacted soil is removed. Major limitations to use of this alternative are the areal extent and depth to which it is physically possible to excavate, Excavation and removal of the soil can be achieved in approximately 1 month of field �-- work. - I3 -