Monday, May 9, 2016

Coal Ash Water Treatment Begins at Possum Point

This morning, May 9th 2016 Dominion Power was scheduled to begin operation of the $35 million portable Water Treatment Plant at Possum Point. If you recall, Dominion Power has been moving forward with a plan to “close in place” 3.7 million cubic yards of coal ash under the recently finalized U.S. EPA Coal Ash regulation. The plan for Possum Point is to consolidate all of the on-site coal ash into one impoundment. There is estimated to be 3.7 million cubic yards of coal ash. Dominion has collected more than 1 million cubic yards of ash from four smaller ponds, put them in a 120-acre pond that already contains 2.6 million cubic yards of coal ash that they will dewater. Ultimately, the pond will be capped with an impermeable membrane to prevent future infiltration of rain.

These coal ash ponds have been open to the elements and taking on water for decades. Trace contaminants and metals in the coal ash may have already leached into the groundwater, Quantico Creek and Potomac. The State Water Control Board and Virginia Department of Environmental Quality (DEQ) are the regulating agencies that oversee the dewatering of the ponds, though the U.S. EPA maintains authority to review applications and permits for "major" discharges, a distinction based on discharge quantity and content. In January 2016 DEQ and the Water Control Board approved the modifications to Dominion’s Virginia Pollutant Discharge Elimination System (VPDES) Permit allowing the treatment and subsequent discharge of the coal ash waters to Quantico Creek, which flows into the Potomac River.

from Dominion Power

The water treatment process begins with aeration. Water is pumped from one of the coal ash ponds into an aerator. Adding oxygen to the water helps the treatment process by separating coal ash particulates in the water.

Chemicals are added to the water, to adjust the pH cause the coal ash sediment to coagulate. The pH is a measure of acidity in the water. Decreasing the acidity of the water encourages particles in the water to settle and polysaccharides act as a coagulant. The chemicals allow the coal ash sediment to bond to form a mass that can be easily removed from the water.

The water is passed through a series of ever finer filters called Geotubes, to remove the particles. Water then flows into a Geotube that separates coal ash sediment from the water and removes them. The water moves onto the next Geotube in the series until all the sediment has been removed. Dewatered sediment from the Geotubes will be hauled away by truck and properly disposed of. Following this filtration the water flows into sand filters where more coal ash sediment is trapped.

Then the water is tested and pumped into holding tank where it will be held until the test results are confirmed. If certain constituents remain at or near trigger levels, then the enhanced treatment will be is used to remove them. The water will be pumped back from the holding tank into a large series of tanks where a process called “weak acid cation exchange” occurs, and the water is treated again.

Because they decreased the acidity of the water at the start of the treatment process, it may need to be readjusted to levels that are safe for the river. After the testing process is complete and the water is tested and confirmed to be safe for the environment, aquatic life and the community, the water will be released into Quantico Creek.

GAI Consulting will collect samples of the filtered water every hour. Pace Analytical Services will then analyze the samples. Dominion will be posting the test results on their web site so that you can monitor the remediation process if you are so inclined at .
from Dominion Power Richmond cleanup

It will take a 11-12 months to treat the water in the ponds. Dominion Power’s plan is to move the remaining 200,000 cubic yards of coal ash from ponds A, B, C, and E to Pond D once the dewatering process is complete. Then the ponds will be covered with high density polyethylene caps, commonly known as a clay caps followed by two feet of soil and vegetation on top of the caps. All five ponds will be monitored for groundwater leaks following the closures. Pond D, the only pond that will still contain coal ash will be monitored for 30 years.

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