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.

The Occoquan Reservoir and Development in the Rural Crescent

 Last Monday the Prince William Conservation Alliance sponsored Protecting the Occoquan Reservoir: Our Shared Water Source! with special guest Stephen Souza PhD, past president of the North American Lake Management Society, the article below is based on his presentation.  Dr. Souza addressed how development of the Rural Crescent and essential portion of the Occoquan Reservoir watershed will negatively affect the reservoir and drinking water in our region.

The Occoquan Reservoir is 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 is a reflection of its watershed.  The Occoquan Watershed is 590 square miles two thirds of which is in Prince William County including the all important headwaters of the Occoquan.

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.  In 1982 to protect the Occoquan from contamination, Fairfax County turned 5,000 acres bordering the reservoir into parkland and down zoned 41,000 acres. Today in Fairfax there are 51 homes on the shore of the Reservoir. In Prince William County there are 450 homes along the shore of the Occoquan Reservoir and Reservoir and watershed are under threat from the development of the Rural Crescent  as development pressures have moved further out with urbanization of the region. 

 Development in the watershed triggers a number of problems that begin with storm water runoff as the primary driver, though waste water point sources and non-point sources also contribute to the deterioration of the water quality. Pollution from runoff, called non-point source pollution is threatening the health of the Occoquan Reservoir and our drinking water supply. As you can see in the diagram below which originally came from the U.S. EPA and Dr. Souza used in his presentation, the hydrology of an area changes with development.

US EPA 2003

One acre of wooded area produces 1,360 gallons of stormwater runoff. While one ace of parking lot and roadways produces 25,800 gallons of stormwater runoff. According to Dr. Souza, the typical suburban lawn is almost as compacted as a parking lot and produces similar runoff. This increased runoff not only reduces groundwater recharge and stream base flow to the region, but also increases flooding, scour and erosion of the stream banks.

Increased runoff reduces water quality and increases the costs to treat the water to meet drinking water standards. Stormwater can also impact groundwater quality. Contaminants are mobilized by runoff and can infiltrate into the surficial groundwater and the fractured rock system that predominates the northwestern portion of the Rural Crescent. This can carry road salt, petroleum hydrocarbons and heavy metals into the groundwater which is the drinking water supply for the Rural Crescent.

Development of the watershed impacts stream flow and health, water quality, the regional ecology and stability of water supply to our region. Prince William County is in the very early stages of studying whether an “Occoquan overlay district” is needed to help protect the reservoir from becoming further polluted, although the County Board of Supervisors is much further along in planning to develop the rural area that is an essential protection and buffer for the Occoquan. 

According to Dr. Souza, development of the rural area of the county could push the Occoquan Reservoir to a water quality tipping point and the next generation will have to address eutrophication of the Occoquan Reservoir. A memorable legacy.  

Saving the Occoquan Reservoir

Prince William County is considering instituting restrictions in an Occoquan Overlay District. How this planning tool is used and implemented will have long term consequences for the Occoquan Reservoir and our drinking water supply. Fairfax Water supplies drinking water to around two million people in Fairfax County, Loudoun County and Prince William County. An essential portion of the Fairfax Water supply especially during times of drought is the Occoquan Reservoir which supplies the source water to the Griffith water treatment plant. The Occoquan Reservoir holds 8.3 billion gallons of water.

When the Occoquan Reservoir was first built 1957 it was located in a rural and forested area and the water was pristine. Now, however; the Occoquan Reservoir is under threat from the urbanization of the region. Pollution from runoff, called non-point source pollution is threatening the health of the Occoquan Reservoir and our drinking water supply.

Non-point source pollution is fertilizer and herbicides from agricultural land and suburban lawns. The largest crop in Virginia is suburban lawns. Pollution form urban and suburban stormwater runoff carrying oil, grease, solvents and tire rubber; septic systems, pet and recreational animal waste bacteria, nutrients and sediment from improperly managed landscaping; and finally, salt.

Development increases impervious surface area. The physical condition of the Watershed's tributaries has been measured to fall with development. Increased stormwater runoff from impervious surfaces flows into streams and creeks at a higher volume and velocity. The result is increased erosion of stream banks that leaves a degraded ecosystem. However, these roads, sidewalks, parking lots all have to be cleared of snow and ice. Over time this has meant an increasing level of salt.

 According to the Virginia Department of the Environment (DEQ) analyses from three different studies at multiple locations have found increasing freshwater salinization in Northern Virginia. According to Fairfax Water, salt contamination in the source water is becoming a generational problem.

from Fairfax Water presentation

While salts are very effective at deicing roads, when the snow or sleet melts the salts are washed off into local waterways or seep through soils into groundwater systems with negative impacts on water quality and the environment. Salts pollute drinking water sources and are very costly to remove. The current water treatment plants cannot remove the salt. The only available technology to remove salt from the source water is reverse osmosis which is cost prohibitive and requires a significant amount of energy to run. This will significantly increase the cost of water in the region.

Planning to protect the Occoquan Reservoir is planning to maintain forested areas, not build more roads, homes or businesses in the Occoquan Reservoir. If we fail to plan for the future and protect the Occoquan Watershed and source water we will have failed the next generation.  To learn more watchthe linked video of Greg Prelewicz and Nicki Bellezza from Fairfax Watertalking about water supply and water protection in the Occoquan Watershed andthe Occoquan Overlay District under consideration in Prince William County.