Prince William county is promoting regressive land use policies and practices, those from a time when we did not know all water is connected. Increased development in the Occoquan watershed as seen in the outline of the Vint Hill Small Area plan will increase paved surfaces and runoff and decrease forested and agricultural land that allow groundwater recharge and store water. The result will be an increase in salinity and chemical and sediment contamination and decrease in streamflow. in the Occoquan watershed.
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| from USGS |
Since 2001 we have added all the “red” impervious surfaces. From 2014 to 2021 Prince William County has lost
almost 2,000 acres of trees. No one knows what has been knocked down in the
past 4 years of unrestrained development and land clearing.
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| slide prepared by Vida Carrol for her PWCA presentation |
So let’s talk a little bit about what’s planned. There are currently 7 rezoning plans already in progress: Strathmore, Silver Bell, the Villages at Broad Run, the Greens at Broad Run, Longleaf at Kettle Run, Alderwood at Kettle Run and Hawthorn at Kettle Run. On Wednesday, October 15th , Longleaf at Kettle Run, Alderwood at Kettle Run and Hawthorn at Kettle Run will be heard at the planning commission. Together these three total 1,123 acres and will have 1059 housing units (townhouses and single-family homes) built.
It is likely that the drinking water for the development in
the small area plan will come from the western system of Prince William Water that is supplied primarily from the Potomac
River via Fairfax Water from the Corbalis Plant (PW Water also draws from Lake
Manassas for the Western system). Drinking water for Woodbridge, Occoquan,
Dumfries, Triangle and Hoadly Manor comes from the Occoquan Reservoir via
Fairfax Water Griffith plant which serves the customers in the eastern portion
of Fairfax Water’s service area and the Eastern Distribution System of the
county (in the Pink). Water from the Occoquan Reservoir supplies the
Griffith treatment plant. The Occoquan Reservoir supplies water to nearly a
million people.
Prince William County holds about 44% of the Occoquan
Watershed; but more importantly, the Occoquan Watershed is more than two thirds
of Prince William County land. Decisions made in Prince William County
will impact all the customers of Fairfax Water and the nearby users of
groundwater. To properly protect the Occoquan Watershed and the regional water
supply you need to know what the impact of development will be.
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| from NVRC |
The Occoquan Watershed Model was developed over decades as we learn more to evaluate the impact of land use decisions and compare potential land use scenarios and their impact on the Occoquan Reservoir water quality. Prince William County helped pay for the creation of that model, but has not yet received the results of the latest study- they are planned to be delivered late this year. Though, Prince William County declined to provide the development plans for the scenarios. Nonetheless, the Board of County Supervisors approved the changes to the comprehensive plan that did away with the Rural Crescent and wholesale change in the land use of the county without even considering what the impact will be on our water supply. Each supervisors meeting seems to rewrite the comprehensive plan and they do not want to look at the damage their decisions are projected to make to the Occoquan Watershed and ultimately the quality and quantity of water to the Occoquan Reservoir.
Prince William County and the Board of County Supervisors
have also failed to consider the impact of the proposed zoning changes to the
quality, availability and sustainability of the groundwater as they are
required to do under the Comprehensive Plan law. Nor did they consider
the impact on meeting goals for the Chesapeake Bay pollution diet.
This is the average flows to the Occoquan Reservoir from each of its sources:
Bull Run Watershed 25%
Occoquan River Watershed 48%
Groundwater and other watershed 20%
UOSA Reclamation Facility 6%
The region’s water supply is under threat. Pave over the sub-watersheds and you eliminate the streamflow. Our woodlands are fast giving way to
impervious surfaces, impacting the water tables and the ecosystem exacerbating
drought. Research by the Chesapeake Bay Program
shows that Prince William County and Loudoun County have lost nearly 5,400
acres of tree canopy to development over just seven years due to human
development. The threats to tree canopy include; the construction of
utility scale solar arrays, warehouses, data centers road expansions and
electrical transmission lines. The loss of trees reduces the recharge of
groundwater which in turn reduces stream flow. The volume of natural freshwater
for drinking reduced and episodic storm water flooding increases. There is no
mechanism on earth for making more water, we have only what falls from the sky
and is stored in the land. Disrupt the
water cycle and you change the ecology.
As Dr. Stanley Grant, director of the Occoquan Watershed Monitoring Laboratory, made clear at his presentation to the PWC BOCS, emerging water quality issues are a result of the “built” environment. As we continue to develop the Occoquan Watershed we endanger the sustainability of the water supply for up to 1 million people in northern Virginia. When population density increases, the impervious surfaces in a watershed increase. However, the increase is not linear, once the population density reaches 100 people per square mile, the rate of increase in impervious surfaces increases rapidly. This is what will finally turn the most urbanized watershed in the United States into a memory.
The salinity in the reservoir has been rising over time and
may be reaching a critical stage. The rising salt in the reservoir is
primarily from watershed runoff (salting roads) during wet weather and
reclaimed water from UOSA during dry weather. Sodium concentration in the
reclaimed water from UOSA is higher than in outflow from the two watersheds
right now and will rise with the increase in blowdown from data center cooling
and increased population density. Along with the salt are all the trace chemicals that we pour down the drain, flush down the toilet and pass through us. However, increasing paved areas increases the
salt runoff into the watershed, so that will increase also.
The only way to remove salt from the drinking water supply
is to invest billions of dollars (from your water rates) in building and
installing desalination equipment in the region’s water treatment plants which
are not currently capable of removing salt from the source water. There is no
other source of water to supply our area. The costs to add treatment lines at
Fairfax Water to keep the Occoquan Potable is estimated to cost between $1 and
$2 billion. This is a cost that will be borne by the water rate payers
including the 350,000 public water users in Prince William County.
Prince William County is on a tear to build housing throughout
the open land in Prince William County. The belief that we need more housing
has overridden any concern for the watershed and the Board of County
Supervisors did not even consider the impact of continued development to the
health of the watershed. The Occoquan watershed is often described as the most
urbanized watershed in the nation. Think about that for a minute, certainly
there are far more urbanized areas in the United States, but they do not have
functioning watersheds. During their growth and development cities across the
nation from New York, to Philadelphia through Baltimore and Washington,
confined and subsumed many thousands of streams, erasing them from memory and
destroying the watersheds.
Scientists have found that land use management can enhance
or destroy stream water quality.
Particularly they found that when 5-10% of a watershed is developed it begins to die,
but can still be restored for a while. If urban land use exceeds the tipping
point water quality does not respond to restoration measures. Once you destroy
a watershed we do not know how to restore it.
Before we do irreversible harm to the ecology and our
regional drinking water supply, we need to look at what the impacts of planned
changes will be to the water supply. The cost to restore the basin and treat
the water is in the billions of dollars that will be borne by us, the
residents. In the future may be too late to protect this essential portion of
our water supply. No analysis has been done as to the potential impact of these
developments to the hydrology of the Occoquan Watershed. There is no understanding
what the impact this might have to the quality and quantity of water to
the Occoquan Reservoir. Yet the Occoquan Reservoir is irreplaceable for
the region.
Land use changes that increase impervious cover more than
5-10% 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-
Increasing flooding.
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| NVRC |
Prince William County and the Board of County Supervisors talk constantly about the need for more housing. Whether of not that is true, we cannot build in the open land in the Occoquan Watershed if we still want to have sustainable drinking water. Period.
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