Water In Eastern Prince William County

There was a Town Hall meeting held at Jenkins Elementary School on Thursday, June 2nd  2022 about the changes planned in land us in the Comprehensive Plan Update and Amendments and what the impact will be on Prince William County. Below is my talk:

If you live in the eastern portion of Prince William County you should care very much about the fate of the Rural Crescent because the Rural Crescent is about water, your water. The public water supply in eastern Prince William (blue) comes from the Occoquan Reservoir. PWSA purchases 15 million gallons of water a day from Fairfax Water for you- it is all drawn from the Occoquan Reservoir. 

The Rural Crescent allows rain water 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.

Development will impair the recharge of the groundwater aquifer, but also increase sediment and salt flow into the Occoquan Reservoir, reduce stream flow and deteriorate water quality while increasing demand for water to feed more homes, businesses and data centers.

Development increases impervious cover from roads, pavement and buildings does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. According to the EPA groundwater recharge is reduced from 50% to about 15% and runoff increases from around 10% to 55%.

When generally open rural area is developed stormwater runoff increases in quantity and velocity washing away stream banks, flooding roads and buildings, carrying fertilizers, oil, grease, and road salt to the Occoquan Reservoir. The salt level in the Occoquan Reservoir is rising almost to the critical point, Fairfax Water says it will cost $1-$2 billion to build desalination treatment their plants.

Our future and our children’s future is our water. We can’t allow it to be destroyed by paving roads and building data centers, warehouses and housing developments that will produce windfall profits for the landowners while leaving us with the bill of one to two  billion dollars to remove the increasing salt level from the Occoquan Waters.

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.

Occoquan Watershed

Recently, the Prince William County Board of Supervisors approved the development of the Preserve at Long Branch, rezoning a portion of the Rural Crescent. No analysis was done as to the potential impact of this development to the hydrology of the Occoquan Watershed.  There is no understanding what the impact this might have to the sustainability of the drinking water supply of adjacent property well owners and the quality of the Occoquan Reservoir itself. 

Occoquan Watershed

The Occoquan Reservoir is an important part of our drinking water supply. The Occoquan supplies about 40% of the clean drinking water for around 2 million people and, in an emergency, can supply all for a short period of time. The reservoir’s current storage capacity is estimated by ICPRB to be 8.3 billion gallons. Prince William land accounts for 40% of the Occoquan watershed which contains 1,300 stream miles, Lake Jackson and Lake Manassas as well as the Occoquan Reservoir.  Water from the Occoquan Reservoir is distributed to customers in Fairfax and Prince William Counties. This water is essential. 

Development impacts water quality. Minimizing impervious surface cover and maintaining the tree canopy is critical to the protection of the County’s streams which flow to the Occoquan and other reservoirs. There is a direct correlation between stream health and impervious surface cover and tree canopy. According to the Northern Virginia Regional Commission, watersheds with impervious surface cover of 10 to 15% show clear signs of degradation, while watersheds with impervious surface cover greater than 25% typically do not support a diverse stream ecology and are dying.

During development the primary impact is erosion and sediment that are carried by stormwater into the streams. The primary post-development impact is increased stormwater volume and velocity that is caused by the removal of tree canopy cover and the replacement of pervious surfaces of plants and grass with the impervious surfaces such as roads, parking lots, rooftops, driveways, patios, etc.

Development increases impervious surface area, and this has created in the past and will in the future create a host of concerns for managing the Occoquan Watershed. For instance, 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.

The Occoquan Watershed is more than just a source of water for the Reservoir. In addition to its role as an essential portion of the drinking water system for approximately 1.2 million Northern Virginians, the Reservoir and the Watershed also serves to improve water quality:

• The Reservoir is an essential element in meeting the Chesapeake Bay TMDL by trapping sediments and nutrients. According to the Occoquan Watershed Monitoring Lab (OWML) the Reservoir captured 34% of total nitrogen, 56% of total phosphorus, and 83% of total sediment.
• The downzoned portion of the Watershed within Fairfax and the Rural Crescent serve as a natural water treatment system and high quality ecological habitat.
• The Reservoir is a regional recreational asset.

Prince William has ignored its responsibility to best manage the Occoquan watershed in conjunction with Fairfax County’s management of Occoquan Reservoir (and their side of the Watershed) maintaining the primary benefit of the Reservoir as an essential and reliable source of safe, clean drinking water for Prince William County and the importance of the Reservoir as an integrated ecological and hydrological system with multiple uses.

Texas Leads the Nation in Water Recycling

The drought burns on in Texas. The state's water plan calls for construction of new reservoirs, desalination plants, pipelines and greater conservation and recycling of water to  make the water supply in Texas sustainable, and Texans are doing it. Direct recycling of wastewater is about to begin in Big Spring, Texas. No other state is taking such bold action to secure their future, but without a reliable potable water supply there is no future. 

The earth has a fixed amount of land and water. All the water that ever was or will be on earth is here right now. More than 97% of the Earth’s water is within the in oceans. The remaining 2.8% is the water within the land masses, as groundwater, rivers, streams, lakes, and within the ice caps and glaciers (over 77% of fresh water is currently frozen and according to climate scientists a significant portion of that may melt). Only a tiny fraction of water falls as rain each year to make the rivers flow, recharge lakes and groundwater. Precipitation does not fall uniformly- there are wet locations and arid locations within a country or region and rainfall varies from year to year and over time as climate changes. Water availability is determined by the weather, climate and the variable length of different parts of the water cycle. Texas has suffered a long drought. 

As the demand for water grows in our population centers, we are straining to meet the demand. Even in generally water rich areas there are limits to the availability of water and United States has slowly and quietly begun to address the availability of water by recycling the water indirectly. In the United States municipal wastewater represents a significant potential source of reclaimed water, an estimated 32 billion gallons of water a day (121 million m3/day) is treated in wastewater treatment plants throughout the country. Currently, National Research Council Water Science & Technology Board estimates that only about 7% to 8 % of this municipal waste water is reused, but a third of this water could be reused.(NRC Water Science & Technology Board titled Water Reuse: Potential for Expanding the Nation’s Water Supply Through Reuse of Municipal Wastewater)

Direct water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, toilet flushing, and replenishing a ground water basin (referred to as ground water recharge) and less commonly returning the water directly to reservoirs. Many of the existing projects that recycle waste water avoid the negative emotional response of drinking water from wastewater treatment plants by either using the water for irrigation and municipal irrigation (golf courses in Arizona) or by treatment and then supplementing river flow, reservoirs or groundwater.

Since 1978, the upper Occoquan Sewage Authority here in Virginia has been discharging recycled water into a stream above Occoquan Reservoir, one of the two potable water supply sources for Fairfax County, Virginia. Recycled water has been part of the Occoquan supply for 34 years supplying Fairfax, parts of Prince William and Loudoun counties with water. Noman M. Cole, Jr developed the Occoquan Watershed Policy in 1971 that specified the type of waste treatment practices that would  be adopted on a basin-wide scale, and provided for an on-going program of water quality monitoring to measure the success (or failure) of the wastewater treatment. This resulted in the construction of the Upper Occoquan Service Authority, UOSA, advanced wastewater treatment plant with tertiary treatment to replace the eleven small secondary treatment plants and the creation of the Occoquan Watershed Laboratory to monitor water quality.  

For 30 years Los Angeles County has recycled the water from wastewater treatments plants. This water from both secondary and tertiary treated wastewater is discharged into spreading basins to recharge groundwater. Groundwater recharge can be done by surface spreading or direct injection wells. California guidelines recommend spreading over injection because of concerns about water quality and potential health hazards. The groundwater is then mixed with other fresh water supplies for delivery to customers. Many of the existing projects that recycle waste water avoid the negative emotional response of drinking water from wastewater treatment plants (the Toilet to Tap Yuck factor) by either using the water for irrigation and municipal irrigation or by treatment and then supplementing river flow, reservoirs or groundwater.

In Texas they are taking it even further. The population of Texas is expected to double in the next 50 years and several cities in Texas have been forced by the population growth, the extended drought and extreme heat of the past several years to address their water supply and sustainability problems head on. Cities in Texas currently use reclaimed water for power plant cooling, argument stream flow, and to irrigate golf courses and landscapes. Now, the city of Big Spring is the first  in the nation to make the direct leap to piping completely treated wastewater to a drinking water treatment plant. 

The Colorado River Municipal Water District in Big Spring, Texas is finishing construction on a $14 million wastewater recycling plant. Previously, Big Spring discharged its wastewater into a creek, which passed it through a wetland area that processed it naturally, making the wastewater potable again. The water recycling plant will short circuit that process, fully treating the wastewater and produce approximately 1.8 million gallons per day of raw water and piping it directly back into the town's water treatment plant where it will be blended with other raw water from the reservoirs for treatment and distribution.

This is a huge and unprecedented step. The Texas Commission on Environmental Quality and EPA have lagged behind Big Spring, failing to develop guidance regulations on direct water reuse. Texas law strictly prohibits interconnection between reclaimed water and potable water systems, though both Big Spring and Brownwood Texas have received permission to build water reuse plants connected to the water treatment plants. In addition the Texas Commission on Environmental Quality has funded a study to develop a resource document that can assist in planning future direct potable reuse projects in the state. No other community has ever bridged the emotional gap of direct water reuse before and Big Spring will shortly be followed by Brownwood. Texas leads the way into the future.

Less Rain Means a Cleaner Bay

Rainfall has been below normal. In the Washington Metropolitan area Virginia, Maryland and the District of Columbia are dependent on the flows of the Potomac River and the Occoquan for their water supply. Potomac River basin has been abnormally dry this year with the eastern shore of Maryland in a moderate drought and river flows below normal. Although the recent rainfall has eased drought in some areas, not enough rain has fallen to raise watershed stream flow to normal levels. Temperatures have been abnormally high and there appears little chance for precipitation in the near term.  But for now, the Interstate Commission on the Potomac River Basin, ICPRB, reports that from a water supply perspective, there is sufficient flow in the Potomac River to meet both the Washington metropolitan area’s water needs and the environmental water flow needs without augmenting river flows by releasing water from the upstream reservoirs. So we can enjoy the clearer flows of the river with little worry or need to conserve water for now.

The ICPRB allocates and manages the water resources of the Potomac River through the management of the jointly owned Jennings Randolph and Little Seneca reservoirs, the Potomac River Low Flow Allocation Agreement and the Water Supply Coordination Agreement adopted in 1982 which designated the ICPRB as responsible for allocating water resources during times of low flow and assist in managing water withdrawals at other times. The ICPRB limits water withdrawals by the local water utilities coordinating Fairfax Water’s utilization of the Occoquan and Potomac and limiting total withdrawals from the Potomac if necessary. In the event that the Potomac River flow at Little Falls is below 700‐million gallons per day the ICPRB releases water from Jennings Randolph and Little Seneca reservoirs to make up the flow and ensure that the saline and freshwater balance necessary to maintain the oxygen levels for oysters, clams and crab populations is maintained. The reservoirs ensure in-stream flows to meet minimum aquatic habitat requirements and the drinking water needs of the region.  

The July 5th Water Supply Outlook from the ICPRB reports that both groundwater and stream flow remain adequate for the short term, but are below normal as rainfall has been below normal for much of the early spring and June. Jennings Randolph (the big reservoir) is full and we are not going to run out of water this year. The good news is that nitrogen and phosphorus contamination in the Chesapeake Bay could fall to the lowest levels since the droughts of a decade ago. The nitrogen and phosphorus contamination in the Bay is correlated with rainfall as seen below and we can enjoy this little preview of what a cleaner Bay might look like.

From the Chesapeake Bay Program 2012

Since the 1970’s large algae blooms have formed in both the Potomac and Upper Bay portions of the Chesapeake Bay watershed each summer. Larger than normal blooms occurred in the upper Chesapeake Bay and its tributaries during August and September 2000 and 2011. These blooms were probably the result of greater than normal amounts of freshwater and nutrients entering the Bay in those years, but there are still factors that need to be studied.  The dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of phytoplankton, which is a group of single-celled algae. While the phytoplankton produces oxygen during photosynthesis, when there is excessive growth of algae the light is chocked out and the algae die and fall below the interface between the warmer fresh water and fall into the colder sea water. The phytoplankton is decomposed by bacteria, which consumes the already depleted oxygen in the lower salt level, leaving dead oysters, clams, fish and crabs in their wake. Thus, the name- dead zone.

In a wedge estuary such as Chesapeake Bay the layers of fresh and salt water are not typically well mixed, there are still several sources of dissolved oxygen. The most important is the atmosphere. At sea level, air contains about 21% oxygen, while the Bay’s waters contain only a small fraction of a percent. This large difference between the amount of oxygen results in oxygen naturally dissolving into the water. This process is further enhanced by the wind, which mixes the surface of the water. Recent heavy wind storms may have increased oxygen levels in various water layers. ICPRB staff scientists will be working with Maryland and West Virginia natural resources scientists to survey algae blooms in the upper Potomac watershed. Researchers will visit numerous sites along the Potomac, its South Branch up to Moorefield, W.Va., the Cacapon River, and the lower Shenandoah River. The summer-long assessment will document the types and extent of algal blooms in this section of the watershed.

While the recent storm brought much damage, the powerful winds that took down trees also served to mix the waters of the Potomac. The waters of the Bay appear clearer than they have in recent years. While drought does improve nitrogen, phosphorus and sediment levels in the Bay in the short run, the cost of drought can be high (agricultural losses and water restrictions) and ultimately droughts end and the rains will come.  The Chesapeake Bay Foundation still judges the Bay to be “dangerously out of balance” despite progress made in the health of the Bay in the past 30 years and this year’s clear waters and healthy shad run. As the Washington Post Reported recently, the District’s 45 miles of Potomac watershed streams and rivers is so tainted with bacteria from the combined sewer overflows that the city prohibits swimming. The waters of the Potomac are the primary drinking water supply for the region they should be clean enough to be safe for swimming and recreation.  The Watershed Implementation Plans from the six states and Washington DC and the $2.6 billion sewage treatment plant upgrade for Washington DC under the Chesapeake Bay TMDL will further improve the waters of the Potomac and the Bay in the next decades. The Maryland, Virginia and the District estimates that it will cost more than $30 billion for them to meet the mandates of the Chesapeake Bay TMDL pollution diet over the next 13 years. Water is not free, it’s just we do not often see many of the costs associated with it. We need to see and understand all the cost of guaranteeing 24/7 access to clean abundant water.  

The Rural Crescent, the Occoquan and the Water Supply

The Board of Supervisors of Prince William County have allocated $60,000 to engage a study to examine if the goals desired from the creation of the Rural Area of the county have been met through the implementation and management of the Rural Crescent. In addition, the study is to identify other rural preservation tools that would allow the elimination of the Rural Crescent restrictions on development density. This is a direct result of a motion by Supervisor Martin Nohe at the regular March meeting of the Prince William County Board of Supervisors.

The Rural Crescent was created in 1998 and originally intended as an urban growth boundary for the county designed to preserve the agricultural heritage and force redevelopment along the Route 1 corridor rather than development in the remaining rural areas. This was to be accomplished by limiting development to one home per 10 acres with no access to public sewers. The Rural Crescent has been chipped away at for years, but still contains 80,000-acres; however, active farming in Prince William continues to decrease.  To adequately judge the utility of the Rural Crescent the study must consider its impact on water resources and water ecology. While the Rural Crescent may have been the wrong policy to preserve our agricultural heritage, it has been a success at preserving water resources, protecting our groundwater and supporting the ecosystem of our estuary. In addition, continued redevelopment of areas with preexisting infrastructure will allow Prince William County to improve storm water management in those areas and score nutrient points for the EPA mandated TMDL as well as revitalize older areas of the county and support of sustainable development. The Rural Crescent is about water, specifically groundwater.

The Rural Crescent in Prince William aligns roughly with the Culpeper groundwater basin, one of the more important watersheds in Virginia and essential to the health of the Occoquan Reservoir which in turn is an essential element in the drinking water supply of Fairfax Water - Prince William Service Authority, PWSA, obtains most of the drinking water they distribute in the county wholesale from Fairfax Water. Besides purchased water from Fairfax Water, PWSA operates the Evergreen water wells that draw water directly from the Culpeper Basin and thousands of home owners have private wells that also draw from the aquifer. The Virginia-American Water Company also distributes water purchased from Fairfax Water. Any changes in land use have the potential to negatively impact groundwater, the watershed and the Occoquan Reservoir and should be considered in the study of “other preservation tools.”  

The Rural Crescent is located within the northeast quadrant and eastern quadrant of the Culpeper basin and consists of an interbedded sequence of sedimentary and basaltic that is highly fractured and overlain by a thin cover of overburden. While ground water flows generally speaking west to east, the fractures within the rock run predominately north south. Contaminants can enter the groundwater at these fractures and zigzag through the aquifer, but these fractures also serve as recharge areas. Groundwater is typically protected against contamination from the surface by the soils and rock layers covering the aquifer, but there is inadequate overburden in much of the Rural Crescent. Once contaminated, groundwater is very difficult to clean and in a fractured rock system there is limited if any natural attenuation and the aquifer could be polluted beyond our ability to remediate.

Generally, groundwater in the Culpeper Basin is replenished each year through precipitation. Groundwater recharge through precipitation requires adequate area for infiltration of rainwater, control of sheet flow created by roads and paved areas, as well as protecting the most geologically favorable infiltration points. Precipitation and snow melt flows over the ground as surface runoff. Not all runoff flows into rivers, much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes the saturated subsurface rock of the aquifer, which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into rivers, creeks, and ponds as base flow for the rivers, and some ground water finds openings in the land surface and emerges as fresh water springs.

According to the U.S. Environmental Protection Agency, impervious cover levels of 10% can significantly impact watershed health increasing stormwater runoff. When runoff volume increases, runoff velocity increases, and peak storm flows causes flooding and erosion.  Increased stormwater velocity increase soil erosion, increases nutrient contamination and reduces water infiltration into groundwater. The groundwater is essential as the base flow to the streams and rivers that feed the Occoquan Reservoir during the dry months. The groundwater stored in the watershed can supply adequate water to maintain river flow during droughts. Maintaining open areas provides areas of groundwater recharge and controls runoff. Decisions about the fate and management of the Rural Crescent will impact groundwater quantity and quality and in turn will impact water flows to the Occoquan Reservoir during dry periods.  Flow to the Occoquan Reservoir is essential in managing the drinking water withdrawals from the Potomac River.  The Interstate Commission on the Potomac River Basin, ICPRB, manages the Potomac River drinking water allocations for the entire region by “suggesting” the quantity that Fairfax Water draw from the Occoquan and Potomac daily.  Prince William County’s decision on the fate of the Rural Crescent could impact drinking water supplies in Fairfax, Maryland, and DC as well as our own county.

 

The “rural preservation tools” to be investigated as part of the study are sustainable community concepts, high density communities utilizing the strategies of Low Impact Development, LID, which include dedicated open space. While high density communities built adjacent to dedicated open space of cute community farms as is being done in Loudoun might preserve our agricultural heritage, it will not guarantee the preservation of our ecosystem and water. When development disturbs more than 10% of the natural land by covering surfaces with roads, driveways, walkways, patios, and homes the natural hydrology of the land is disturbed, irreparably disturbed. These developments while much better than traditional developments still disturb more than half the land area by significantly increasing building density. 

The lack of overburden limits natural protection to the aquifer, but has allowed easy infiltration. The sedimentary rocks of the Rural Crescent are productive aquifers and feed not only the groundwater wells that provide drinking water to Evergreen and other communities, but also feeds the tributaries to Bull Run assuring the base flow to the rivers and streams that feed the Occoquan. Our freshwater resources need to be managed as a whole. Development that will impair the recharge of the aquifer can result in impacts to the entire region, including the decrease in water level and aquifer storage, reductions in stream base flow and lake levels, loss of wetland and riparian ecosystems, saltwater intrusion and changes in groundwater quality. Our future and our children’s future is our water. We can’t allow it to be destroyed  in paving roads and building houses for short term gain.