Water Withdrawals & Conservation
We are fully committed to the responsible use and conservation of water resources, which are critical to our operations.
We heat highly purified and pressurized water in our steam-electric generating units to produce the steam that spins turbines to generate electricity. Water is also the most common source of cooling for these units, which use either once-through cooling systems or closed-loop systems to remove excess heat.
In 2011, total surface water withdrawn dropped by about 6 percent from 2010 levels, to 4.3 trillion gallons from 4.6 trillion gallons.
About three-fourths of our facilities withdraw water and return it to the source (once through) at a slightly elevated temperature but with little to no consumption involved. The other 25 percent have closed-cycle cooling or air-cooled condensers and withdraw very little water, compared to facilities using once-through cooling.
Other ways that we use water in our operations include:
- water sluicing processes (transporting coal ash);
- water treatment systems (sediment ponds);
- air pollution control equipment (sulfur dioxide scrubbers); and
- drinking and sanitary purposes at our various facilities.
Closed-loop Cooling Towers
In 2011, Dominion nearly completed construction of a $570 million, twin closed-loop cooling tower system at the company’s Brayton Point station in Massachusetts, one of the largest fossil-fired stations in New England. The towers are now fully operational, and the amount of water withdrawn from Mt. Hope Bay has dropped by more than 90 percent, from about 1 billion gallons per day to about 100 million gallons per day.
Reuse and Conservation
At two of our fossil-fired stations, one located in Virginia and one in Massachusetts, we have partnered with local wastewater treatment facilities to reuse their treated waste water rather than fresh water to supply the air-pollution control devices, known as scrubbers, that we use to control sulfur dioxide emissions at the stations. In 2010, we reused or recycled nearly 334 million gallons of municipal wastewater at our power stations, according to internal estimates.
In 2011, water reuse and recycling of municipal wastewater increased – by about 9 percent from 2010 levels – to approximately 364 million gallons. We attribute this increase primarily to the reuse of wastewater in a scrubber at one of the company's power stations in Virginia.
As in other areas of our business, we also are successfully making use of the Six Sigma process improvement methodology in a number of projects to reduce our city water usage, the water used in our power station systems, and the river water used in the clarified water systems at various company facilities.
CDP Water Disclosure
In 2011, we participated for the first time in the Carbon Disclosure Project’s “Water Disclosure” reporting process to share data and information about Dominion’s overall water use and risk management practices.
Natural Gas Business
The water used in our gas transmission and distribution businesses is significantly less than the amount of water that we withdraw or use at our electric generating stations.
We use water to pressure test new and existing natural gas pipelines. This water is filtered and tested before it is discharged in accordance with applicable state and federal permits. Of course, we also use water for drinking and sanitary purposes.
At the Cove Point LNG terminal on the Chesapeake Bay, we use extracted groundwater as part of the vaporization process that assists in turning liquefied natural gas into its gaseous form for shipment to markets along the East Coast.
And we produce water when operating our gas storage and production wells. The majority of this produced water, known as brine, is collected and injected into permitted underground injection wells (UIC Class II) that are designed and operated for brine disposal. About one-fourth of this produced water is sent to approved off-site disposal facilities for treatment.