The potential presence of PFAS led MCAS Cherry Point to request an merging contaminant assessment. If treatment systems caused significant delays to the utility corridor’s construction schedule or if estimated treatment costs were outside of the project budget, it would prevent the F-35 program from being established at the installation. This emerging contaminant assessment had to be done promptly.
SOLUTION
Prior to mobilizing the field assessment, our team prepared a groundwater characterization work plan that specified procedures and protocols to be followed by field personnel and the laboratory supporting the project. This plan included sampling standard operating procedures such as specific measures to prevent sample contamination by PFAS and cross-contamination of PFAS samples.
Without any certified methods in place for PFAS assessment, it’s up to consultants and the buyers to vet and partner with laboratories that can process the samples to help define the extent of the problem. Our team helped MCAS Cherry Point navigate the selection of a reputable laboratory for these services.
The site assessment began with a desktop review and moved quickly to sampling four monitoring wells along the corridor. Although the scope of work focused on testing for PFAS, the assessment looked for other suites of compounds that could impact PFAS treatment technologies.
Once the results were in, a historical data review was performed to identify data indicative of groundwater quality along portions of the corridor where there were no existing monitoring wells. This combined dataset informed the team’s prediction of the worst-case water quality for dewatering fluids that would require treatment. The assessment indicated that PFAS, select chlorinated solvents and hydrocarbons, and arsenic were the present contaminants requiring treatment. Treatment objectives were established to support the discharge of dewatering fluids to the base storm sewer, which is subject to National Pollutant Discharge Elimination System permitting.
Before outlining treatment options, our team collaborated with MCAS Cherry Point to understand how it would typically sequence this project. We were then able to calculate dewatering rates that informed the volume of water that would need to be treated.
Our team then outlined multiple treatment technologies for site remediation in a feasibility study, comparing the remediation options against potential risks to the site. We sought options that would be productive, protective and prevent exposure.
Given the scope of construction dewatering, options such as powdered activated carbon, nanofiltration and reverse osmosis were determined to be infeasible. These technologies would be either ineffective in treating all the contaminants present, result in reject concentrates that would require additional treatment or management, or could not easily be delivered in a mobile treatment system.
Granular activated carbon and ion exchange resins were then compared to assess the cost to treat dewatering fluids using mobile treatment systems relying on granular activated carbon and ion exchange for the removal of PFAS. This assessment demonstrated that ion exchange technologies would be more cost-effective, due to the longevity of the ion exchange treatment media. Based on this complete evaluation, our team identified a treatment system that would include granular activated carbon to treat the chlorinated solvents and hydrocarbons, to be followed by ion exchange for removal of PFAS and arsenic.
RESULTS
In just three months, MCAS Cherry Point had a PFAS sampling report and treatability assessment that outlined the recommended treatment system for use in construction. We worked with contractors to obtain estimates to treat the anticipated volume of dewatering fluids throughout construction. This report reduced the environmental contingency on the project by over 80%, allowing their mission to move forward. It also informed the construction bid’s project scope. The project’s construction contract will include this treatment system as part of the larger utility corridor construction project.
With this assessment and future contaminant treatment plans in place, MCAS Cherry Point will be ahead of anticipated federal regulations on PFAS remediation. MCAS will address the contaminant as part of this massive construction project for a long-term program.
