Wednesday, October 26, 2022

Montclair Town Hall

 On Wednesday there was a Town Hall Meeting at the Montclair Library. Below is from 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 and grey) 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, soak into the earth, feed the aquifers that provide water to the private wells and the Evergreen water system. But groundwater also feeds the tributaries to Bull Run and the Occoquan River assuring a constant base flow to the rivers and streams that feed the Reservoir and control of stormwater.

from UOSA

Development will impair the recharge of the groundwater aquifer, but also increase sediment and salt that flows 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%. To prevent flooding, storm damage and reduction in water resources that runoff needs to be captured and redirected. To make sure that this water is not lost, it will have to be stored for future use. 

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 at the water treatment plants. In addition, the Reservoir will have to dredged to restore the lost volume and potentially enlarged at great expense.


The salinity in the Occoquan Reservoir has been rising for a number of years and is reaching the critical level and will be made worse by development in the Rural Crescent and by data centers in particular. There are two ways that data center will increase the salt in the Occoquan:

Pavement. In winter all that pavement in parking lots around backup generators and roads will be sprayed with brine solution or salted and increase the salt content in the runoff.

Cooling. Cooling evaporates some of the water concentrating the salt that is already in the water. In addition to increase the efficiency and life of cooling equipment they soften it (which means they add brine, salt water). The minerals and salt build up in the cooling tower and are blown out. The cooling tower blow down contains high salt levels and is sent to the wastewater treatment plant which has no ability to remove salt.


The water in the Occoquan Reservoir comes from: Bull Run, the Occoquan River and the UOSA. A significant portion of the water flowing to the Occoquan Reservoir is from the Upper Occoquan Service Authority wastewater treatment plant. That water is getting saltier. It is believed that the other sources of sodium include the data centers effluent.


Haymarket data Center (AWS)

Data centers are also a potential source of diesel contamination to the watershed. The data centers need to operate 24/7 so they maintain a backup power system consisting of banks of giant generators. Data centers need immense amounts of power (2.6 gigawatts capacity and growing fast) they require about 40 - 2 Mw generators each to keep operating. Backup generators at a data center usually run on diesel; not one of the cleanest fuels. Banks of backup generators are lined up at each and every data center. To power these generators, diesel fuel needs to be stored onsite, so each site contains large fuel storage tanks with pipes and valves to feed each generator- all potential spots for leaks and spills.

Just to give you a look of how big these generators here are three next to a diesel fuel truck.

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.



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