ARCHIVED REPORTS XR0009921 - Laserfiche WebLink

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Corrective Action Plan Page 45 available and the project is authorized Permitting procedures are estimated to require an additional seven weeks When all requisite permits have been secured, construction of the groundwater recovery and treatment system can be completed six and a half weeks thereafter Operating trials to ensure that air and waste-water discharges are within regulatory luruts will require one week Accordingly, it is estimated that the groundwater recovery and treatment system will be full operational approximately five months after work begins Startup of the groundwater recovery and treatment system will be followed by a three- month commissioning period during which groundwater quality, discharge quality and system performance parameters will be monitored in various combinations at weekly and monthly intervals to establish system characteristics and provide a data base for future monitoring Experience has shown that it is difficult to predict the total time required to fully remediate contaminated groundwater However, where the hydrogeologic characteristics are similar to those beneath the subject property, large reductions in contaminant concentrations usually occur within the first several month after groundwater pumping is started and the concentrations are normally reduced to very low levels within two to three years When the concentrations of total petroleum hydrocarbons (quantified as gasoline), benzene, toluene, ethyl benzene and total xylenes in samples recovered from the monitoring and recovery wells have been reduced to less than, or close to, detectable levels and it is judged that further operation of the remediation system would not be cost- effective, pumping from the groundwater recovery wells will be discontinued However, quarterly rounds of groundwater sampling and analysis will be continued until the concentrations of contaminants measured in the samples have been reduced to less than that of regulatory concern Based on the considerations outlined above, it is estimated that remediation of the site will be substantially complete within four years from the time construction of the remediation system is authorized and it may be possible to obtain closure of the property as the site of an unauthorized release of fuel hydrocarbons within approximately five years from that same time However, the actual time required to remediate the site will depend on the rates at which the concentration of contaminants in the groundwater can be reduced and the total time required to eliminate any residual traces of contaminants to less than those of concern to the regulatory agencies Also, because the natural processes that control the late stages of soil and groundwater remediation are extremely complex, it must be recognized that the actual time required to complete the work may differ substantially from that estimated