Former Electronics Components Manufacturing Site Groundwater Remediation - When Is It Appropriate to Change Remedial Technologies?

摘要

A confidential remediation site located in south central Pennsylvania(the Site),exhibits groundwater in a carbonate bedrock aquifer with concentrations of chlorinated volatile organic compounds(VOCs)exceeding relevant standards.A traditional groundwater extraction and injection system(pump and treat)was installed at the Site by a previous owner and operated between 1985 and 2002.Although the rationale for choosing this design has been lost to time and the incomplete files left behind by previous ownership,based on the Site location and aquifer characteristics,it was not optimally suited for the task.During the period of system operation,an immediate and significant reduction in VOC concentration was attained,however,residual concentrations of VOCs in groundwater persisted.The high mineral content of the local groundwater resulted in the calcification and failure of several sets of stripping towers between 1985 and 2002 and reduced efficacy of the remedial system.Changes occurred in the technologies available for groundwater remediation,the regulatory processes for Site classification and the process of determining cleanup standards since the groundwater remediation program at the Site began.A study was performed to assess the residual VOC concentrations and to evaluate the most appropriate technologies currently available to bring the Site to full regulatory closure in a cost-and time-effective manner.The Responsible Party for the Site(not the current Site owner)and CRA embarked on a program to update the hydrogeologic characterization of the Site,review alternative groundwater treatment technologies,and evaluate options to attain Site cleanup status and to secure release from liability.Based on this work,the Responsible Party successfully obtained permission to change remedial technologies from the Pennsylvania Department of Environmental Protection(PADEP).The changes were implemented in the spring of 2001.The current remedial technology employs in-situ ozonation,and preliminary results appear to be positive.