Protections are needed for the Occoquan

This week is Source Water Protection Week. While scrolling through local news reports, I came across this news report in the Potomac Local:

“According to the airport’s operations manager Richard Allabaugh, about 11:53 p.m. on August 24, there was an accidental discharge of fire-retardant foam at the Leidos Hangar facility on Frank Marshall Lane. There had been no fire in the hanger, which is when such a system would have gone off as designed.” (Rick Horner, Potomac Local)

Mr. Allabaugh, himself, was kind enough to send me the pictures below.

The release took place at night

The berms were place to prevent the foam from leaving the site

The next morning

For the second time in less than two years Manassas Airport has had a significant release of fire suppression foam unrelated to fires. Aqueous film-forming foam, which is known as AFFF, is a firefighting foam widely used in the aviation industry because it quickly extinguishes fuel fires by spreading across the surface, depriving the fire of oxygen. This also makes a spill hard to control. The foam contains chemicals known as per- and polyfluoroalkyl substances (PFAS) that are persistent in the environment and bioaccumulate.

This time the foam did not reach the waterway and according to Mr. Allabaugh was fully contained on-site by the cleanup crew. DEQ, the County HazMat team, and Fairfax Water were appropriately notified of incident. The Manassas Airport is upstream from the Occoquan Reservoir along Cannon Branch which flows into Long Branch, and accidents do happen.  The response by the airport operations was by the book.

from Google maps

The Occoquan Reservoir consists of 1,400 acres containing 8.5 billion gallons of water that provides 40% of the daily water supply for Fairfax Water which in turn supplies Prince William Service Authority and a significant portion of Loudoun County. The reservoir’s water quality is a reflection of its watershed; spills, roadway runoff, stormwater carrying oil, salt and dirt are all carried into the Occoquan Reservoir. The water from the reservoir is then treated by the Griffith Water Treatment Plant and piped out to customers.

Forty percent of the 570 square miles of the Occoquan Watershed including the headwaters of the Occoquan are in Prince William County. When the Occoquan Reservoir was first built 1957 it was located in a rural and forested area and the water was pristine. The unrelenting growth and development in this region has changed that.  Without additional treatment lines there are limits to what contaminants the Griffith Water Treatment Plant can remove from the raw water.  Because they are water soluble, traditional water treatment technologies used by Fairfax Water are not able to remove PFAF from the raw water.

Reportedly, testing was done after the February 2020 spill of fire suppression foam that was not fully contained on site. The Occoquan Watershed Monitoring Laboratory did not find significant PFAS contamination in the Reservoir. The 8.33 billion gallons would have diluted the PFAS present if it was carried to the Reservoir, but PFAS is known as the forever chemicals because they take hundreds if not thousands of years to degrade and accumulate in people and the environment. Traces of these chemicals have become ubiquitous in our environment.  The levels of PFAS found were all below the U.S. Environmental Protection Agency’s (EPA) health advisory level of 70 ppt. The EPA has not yet established a health based MCL.  

Still, the water quality of the Occoquan Reservoir is of concern. Last fall, the Prince William County Board of Supervisors issued Directive No. 20-86 for county staff to develop a protection overlay district for the Occoquan Reservoir. County staff reports that they have reviewed a recent report prepared by the Occoquan Watershed Monitoring Lab of the Occoquan Watershed and the Reservoir System water quality. The county staff has discussed the report-findings with the Northern Virginia Regional Commission. 

Staff is also reviewing reports and recommendations from local committees and environmental groups and evaluating current design standards and development practices, in relation to water quality trends in the Reservoir. An overlay district could be used to limit the types and amount of development on land within the watershed to protect the Occoquan Reservoir to control non-point source contamination, it could also be ineffective if too loose or constantly overridden by the Board of Supervisors. Further development is a very real threat to our drinking water supply for more information see the Occoquan Watershed Monitoring Lab report.