Pilot Region-Based Optimization Program for Fund-Lead Sites in EPA Region 3. Site Optimization Tracker: Croydon TCE Site, Bristol Towns, Pennsylvania:Final rept

摘要

The TCE concentrations at the site are relatively low (a maximum of approximately 16 ug/L relative to the MCL of 5 ug/L), and concentrations continue to decrease. Although this represents significant progress toward aquifer restoration, it also means that the P&T system is having a diminishing effect on removing contaminant mass and progressing toward aquifer restoration. The site team should begin to consider the point at which P&T will provide no additional benefit to the natural processes of dilution and dispersion (and possibly degradation) that are occurring. With P&T operation, TCE concentrations may continue to decline or they may become asymptotic, indicating the impracticability of the P&T system to meet the current (or potentially modified) cleanup standard. It is unlikely that any decision to shut down the P&T system will be made before the site is transferred to the State. As a result, the evaluation team suggests that an exit strategy for the P&T system be deferred until after the site is transferred to the State in November 2005. The State can then work with EPA to consider the concentration trends, determine the effect the P&T system has on reaching the cleanup standard, develop an appropriate cleanup standard, and determine an appropriate point to discontinue P&T.