Four separate treatment buildings were designed and constructed with AS and SVE treatment systems. The individual solenoid valves on each AS and SVE well, combined with a programmable logic controller (PLC), allowed CDM Smith to create multiple pulsing networks, which are modified periodically to optimize PCE removal. Design and installation of four smaller treatment systems rather than a single, large treatment system and operation of the systems in pulsing rather than continuous modes allowed the use of smaller capacity compressors and blowers for capital and energy savings and increased system effectiveness. Optimization of flow balances between the AS and SVE pulsing networks has further reduced electrical usage by 30 percent.
Subsequently, at the Ravenswood site, CDM Smith evaluated existing data from the state of West Virginia’s extensive investigations and developed a groundwater flow model, plume maps, trend analyses and mass balance calculations to define treatment options. Ravenswood’s existing municipal Venturi strippers had been providing limited treatment capacity, with high maintenance needs.
Leveraging the experience gained at the Vienna site and the Ravenswood groundwater model, CDM Smith helped EPA develop a strategy to reuse Vienna’s decommissioned TU4 AS/SVE treatment system at Ravenswood for a pilot study, enabling rapid installation with limited costs.
At the Vienna site, within the first 4 years of treatment system operation, 1,529 pounds of PCE mass were removed, with a >98 percent decrease at the larger source area. By the end of 2013, 1,778 pounds of PCE had been removed. CDM Smith’s installation and operation of the pilot system at the Ravenswood site has limited the PCE entering the municipal water supply, as EPA designs a larger, permanent treatment system for Ravenswood.
Both sites have realized energy savings from the pulsing networks employed to increase system effectiveness. Excavated materials from both the Vienna and Ravenswood systems were recycled and reused as additional green measures.