Fairfax Water gave an update on their work to ameliorate their PFAS problem in the Occoquan Reservoir to comply with the U.S. Environmental Protection Agency (EPAs) new national drinking water standard PFAS chemicals.
In April 2024, the EPA announced the final national primary
drinking water standards for six poly- and perfluoroalkyl substances (PFAS).
Public water systems have five years (by 2029) to implement solutions that
reduce these PFAS if monitoring shows that drinking water levels exceed the
maximum contaminant levels (MCLs). Fairfax Water has stated that they
will ensure their water meets these standards by the regulatory date.
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| image from Fairfax Water |
Fairfax Water supplies not only Fairfax, but parts of
Loudoun and Prince William County as a water wholesaler to American Water and
Prince William Service Authority . Fairfax Water participated in the Virginia
Department of Health (VDH) Occurrence Study that was completed in 2021. It
is important to point out that the practical quantitative limit was 4 ppt just
at the proposed regulatory limit. Some of Fairfax Water’s results for PFOS and
PFAS were above the MRL and the regulatory limit. The ones below cannot be
quantified, they might be just below the quantitative limit or lower.
Prince William Water (then called the Prince William County
Service Authority) also participated in a Virginia Department of Health (VDH)
study to test for PFAS in water samples collected from the distribution systems.
The Service Authority collected samples from its East and West systems and the
results for the east system (which comes from the Occoquan Reservoir) were
above the detection limit and ultimately the EPA MCL.
At the time that EPA finalized the primary drinking water
standard, Fairfax Water said: “Our
data shows that the PFNA, HFPO-DA (commonly known as GenX chemicals), PFHxS,
and PFBS levels in our water are all below the MCLs and HI. PFOA and PFOS
results for Potomac treated water are less than the MCL of4.0 parts per
trillion (ppt). PFOA and PFOS results for the Griffith Water Treatment Plant,
which treats water from the Occoquan Reservoir, are slightly above the MCL of
4.0 ppt. Fairfax Water is evaluating treatment processes to ensure that our
water will meet these standards.”
Fairfax Water performed additional sampling and testing. Fairfax
Water hired an independent lab to test their water Every sampling found
elevated PFOA and PFOS at or near the MCL of 4.0 ppt.
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| image from Fairfax Water |
Now, Fairfax Water has made available the 2024 third quarter update of their work on PFAS and their conclusions. Based on the most recent quarterly running annual average (RAA), the Occoquan (Griffith Water Treatment Plant) will not comply with the EPA regulation for PFOA when it goes into effect in 2029. Compliance for PFOS is marginally below the regulatory limit. Additional treatment processes will be required to comply with regulations.
Sampling data for the Potomac River water supply indicate that
the Corbalis Water Treatment Plant will comply with the PFAS regulations
without additional treatment. So, Fairfax Water is moving ahead with designing
a water treatment train to remove PFAS from the water drawn from the Occoquan
Reservoir.
Fairfax Water estimates that it will cost $389 Million over
next 6 years to comply with the EPA MCL by 2029. This begins with studies of removal
technology and bench testing which took place this past year. Next year they
plan to have a pilot plant up and operational. Finally, the Design and
Construction of plant scale PFAS Removal and Treatment should be completed by the
end of 2029. Additional PFAS infrastructure may be required to support the new Luck
quarry reservoir supply. In addition to the capital expenditures Fairfax Water
expects to spend around $24 million per year in additional operating expenses
forever. This is about one fifth of their current operating expenses.
The water in the Occoquan Reservoir comes from the Occoquan
Watershed. Our water supplies are connected to each other and the land. Two
thirds of the Occoquan Watershed that supplies the Occoquan Reservoir is in
Prince William County. The former Rural Crescent allowed rainwater to flow
gently over vegetation, feed the aquifers that provide water to the private
wells and the Evergreen water system, but also feeds the tributaries to Bull
Run and the Occoquan River assuring the base flow to the rivers and streams
that feed the Reservoir.
The Upper Occoquan Service Authority, UOSA, the wastewater
treatment plant also delivers 40 million/day of recycled water that originated
in the Potomac River to the Occoquan Reservoir. Supplementing the supply. Keeping
PFAS out of the source water is a real challenge when PFAS is in our diet and
wastewater is reused in our drinking water supplies. To stay within the
regulatory limit, Fairfax Water will have to identify the PFAS content in the
various sources of water and can either mix them to minimize exposure or remove
them.
Armed with $750,000 in new equipment for the purpose, the
Occoquan Watershed Laboratory has been testing water samples from throughout
the Occoquan watershed to determine where the PFAS in the reservoir is coming
from to see if it is possible to address the problems at the sources at the
expense of the polluters rather than the water customers. PFOA and PFOS were found
above drinking water MCLs in multiple sampling locations at levels several times
higher than the drinking water limit.
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| Image from Fairfax Water |
Sampling has so far confirmed Industrial wastewater discharges to UOSA from Micron Semiconductor plant and from Freestate Farms. Also confirmed as a source of PFAS by sampling is the Federal/Military in the Vint Hill area and Vint Hill Farms. The old Vint Hill army base where the Fauquier Times reported that for the past several years, the U.S. Department of Defense has been monitoring PFAS contamination at Vint Hill that is believed to be tied to a former burn pit where soldiers practiced putting out fires with firefighting foam containing PFAS chemicals, which then leached into the soil and the groundwater. These sources have been confirmed by sampling.
There are also several potential sources that need to be
further investigated: the non-Micron reclaimed water from UOSA, accidental
releases from Manassas airport, Dulles Airport, the legacy CERCLA sites – IBM in
Manassas and Atlantic Research in
Gainesville currently being redeveloped into data centers. PFAS in biosolids
land applied under a permit in the watershed.
Occoquan stakeholders are engaged on the PFAS issue - UOSA, Fairfax County, Prince William County, Prince William Water, Virginia Tech (Occoquan Watershed Monitoring Lab), Virginia Department of Environmental Quality (DEQ), Virginia Department of Health (VDH)
Ongoing and emerging efforts to characterize PFAS include:- Adding PFAS to existing groundwater monitoring sites
- Adding PFAS to the scope of the Occoquan Watershed Monitoring Program
- Working with potential sources to understand past and/or ongoing use of PFAS
- Characterizing PFAS in industrial wastewater discharges to UOSA
- Monitoring other wastewater and industrial stormwater discharges for PFAS
