ARCHIVED REPORTS XR0009987 - Laserfiche WebLink

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Conclusions and Recommendations Selection of Cleanup Option It is Wnghts opinion given the PHS-EHD concern for residual contaminants and the responsible parties desire to obtain closure that, Option 3 is the best option Option 3 naturally degrades contaminants that may contribute to the Iong-term dissolved plume presence The placement of indigenous petroleum degrading bacteria in the contaminated areas would enhance natural attenuation by degrading these residual contaminants in a shorter period of time than natural attenuation Moreover, Wright asserts that Option 3 is the most reliable, cost-effective and least disruptive approach considenng the con-fined working area, of the residential trailer lot Options 1 and 2 were not selected fro the following reasons Soil Excavation and Removal/Option I would remove contaminated soil and groundwater from the "hotspot areas" but is not attractive due to the cramped working area involved with this site and the lack of access for heavy equipment and dump trucks during an excavation process There is no doubt that some trailers will have to be temporarily moved and the occupants relocated for a short time causing them personal disruption An additional complication is the fact that the contamination hes close to a nearby irrigation pipeline The owner of the pipeline has strongly noted that they do not want an excavation anywhere near the pipeline given the potential for possible damage to the line In addition, there are water, sewer and gas Innes that crisscross the entire area making it virtually impossible to excavate the contaminated soils without disrupting the utilities of all tenants on site Finally the costs to relocate residents and replace these utilities would be prohibitive Soil and Groundwater Dual Phase Extraction/Option 2 may be equally disruptive as In-situ Biodegradation/Option 3 and also similar from a cost standpoint depending upon the amount time the system must operate to aclueve the desired level of contaminant reductive to achieve site closure The vapor contaminants could be destroyed by combustion however the groundwater contaminants would be absorbed onto carbon and the quantity of carbon use will directly affect the overall costs If the project life assumes carbon change outs every two months, and contaminant removal would occur and this should lessen the TPHG and Benzene concentration in the area of MW-9 and MW-3 The duration of system use to attain assumed cleanup values in the vicinity of less than I part per million TPHG and less than 50 parts per billion, or less, of Benzene is anticipated to be at least 18 months If contaminant levels decline at a rate less than projected and the carbon usage requires more frequent changes or a longer duration of extraction, the costs escalate accordingly Page 16