Project Overview
Background
The New Hampshire Department of Environmental Services (DES) was notified by the U.S. Air Force in May 2014 that water samples from the Haven public water supply well at the location of the former Pease Air Force Base (AFB), contained levels of perfluorooctanesulfonic acid (PFOS) at 2.5 ug/L and perfluorooctanoic acid (PFOA) at 0.35 ug/L. The City of Portsmouth closed the Haven well and commenced the investigation, design and testing to remediate the impacted groundwater. Firefighting foam used at the former Pease Air Force Base, prior to its closure in 1991, is the presumed source for the PFOA and PFOS in groundwater.
The groundwater extraction, treatment and reinjection system, called the Airfield Interim Mitigation System (AIMS), was constructed in May 2018 to remediate groundwater throughout the area surrounding the former AFB, where the groundwater is also used by private water supply wells. The AIMS system adsorbs per- and polyfluoroalkyl substances (PFAS) from the groundwater with granular activated carbon (GAC) and a granular resin. The treated water then accumulates in an equalization (EQ) tank, where the water is used to backwash the media filters or is returned to the aquifer through a series of injection wells at a rate of approximately 350 million gallons per year. The resin, containing extracted PFAS, can be regenerated for a period and then must be destroyed at an off-site hazardous materials incineration facility. The former Pease AFB is the first site in the country to use this resin technology. The Air Force has spent $58 million, to date, cleaning up and protecting groundwater at and near this former AFB.
Solution
Members of T&M’s Automation and Controls Team were responsible for the design, fabrication, commissioning and start-up the control system. The system incorporated Variable Frequency Drives (VFD) to improve operational efficiency and energy savings, instrumentation, automated valves, programmable logic controller (PLC), a Supervisory Control and Data Acquisition (SCADA) system and the fabrication of the entire power distribution system for the treatment plant.
This solution permitted the system to be fully automated, allowing operators to monitor the system remotely and receive alarm notifications by email or text message. T&M is still supporting Wood Group in SCADA upgrades and system optimization.
