Water Sources and Treatment
The Western Virginia Water Authority provides an average of 23 million gallons of drinking water per day to more than 155,000 people (55,000 customer accounts) via more than 1,000 miles of pipes, storage tanks and pump stations in the City of Roanoke and Roanoke County. Water from all Western Virginia Water Authority sources is disinfected with chlorine. Fluoride is added to promote strong teeth.
Water Division staff continuously monitors the treated water supply at water sources and throughout the distribution system in a chemical laboratory and a state-certified bacteriological laboratory. Chemical tests on samples are run daily, allowing plant operators to make appropriate adjustments in the treatment process. Bacteriological tests also are run daily to ensure that the water is safe for consumption. All monitoring is done in compliance with the Commonwealth of Virginia Board of Health and the U.S. Environmental Protection Agency in accordance with the Safe Drinking Water Act (1996).
The entire water supply system is monitored with SCADA (Supervisory Controls and Data Acquisition/Distribution Control System) software. SCADA allows operators to control operations at the filter plants and twenty remote transmission units throughout the water distribution system.
The Western Virginia Water Authority’s drinking water comes primarily from four sources: Carvins Cove Reservoir, Spring Hollow Reservoir, Crystal Spring and Falling Creek Reservoir. In addition, the Water Authority maintains several wells that supply small areas of eastern Roanoke County. A limited amount of water is also purchased from the City of Salem to supply a small area of Roanoke County west of Salem.
Carvins Cove Reservoir
Carvins Cove Reservoir is within Carvins Cove Natural Reserve, a 12,700-acre area near Hollins University in Botetourt and Roanoke Counties. The land in the Natural Reserve above the 1,200-foot contour is owned and operated by the City of Roanoke. The land below this elevation, and the reservoir, are owned and operated by the Western Virginia Water Authority. In addition to receiving water from the Cove's 11,200-acre drainage area (or watershed), the reservoir is fed from two underground tunnels that carry overflow from Tinker and Catawba Creeks. This surface water source covers 630 acres and stores 6.4 billion gallons of water at full pond. Carvins Cove Water Treatment Plant has the capacity to treat 28 million gallons of water from the reservoir every day. The plant normally treats 11 to 15 million gallons of water a day and supplies most of the City of Roanoke and parts of northern Roanoke County.
The filtration process takes place in a series of basins. Water is first aerated to remove unwanted dissolved gases and to oxidize dissolved metals, which reduces any unpleasant tastes and odors. Flash mixing of chemicals is the next step, where alum is added to coagulate suspended particles. Water then flows into settling basins where the particles clump together, become heavy and settle to the bottom of the basins. The water is next filtered through gravel, sand and carbon. Filtered water flows from the two finished-water reservoirs at Carvins Cove Filtration Plant into two 36" lines to the water distribution system.
Spring Hollow Reservoir
The main source of supply for customers in Roanoke County is Spring Hollow Reservoir, which is a pump storage reservoir near the headwaters of the Roanoke River in Roanoke County. The reservoir was formed by a roller-compacted concrete dam that is 243-feet high and has a crest length of 990 feet. Spring Hollow has a working volume of 3.2 billion gallons, a surface area of 158 acres and a drainage area of 540 acres. The reservoir is supplied by a pumping station that pumps water from the Roanoke River when the river's flow is at or above the state-permitted withdrawal level. The pumping station is capable of pumping up to 80 million gallons per day into the reservoir.
Advantages of the pump-storage reservoir are that water can be stored and used when river flows are below permitted withdrawal levels. Also the reservoir acts as a large settling basin, which allows suspended particles to settle out, improving water quality to help the water-treatment process.
The Spring Hollow Water Treatment Facility treats about 7 million gallons daily but has the capacity to treat 36 million gallons of water a day. Treatment consists of chlorine dioxide addition for pre-disinfection/pre-oxidation; ferric sulfate used to coagulate suspended particles; clarification; and filtration through mixed media filters consisting of two grades of sand and anthracite coal. The water is further filtered in granular activated carbon contact basins, chlorinated for disinfection and stored in a 2-million-gallon finished-water clearwell. Finished water is pumped from the clearwell by four, 4,000 gallon per minute pumps into the water distribution system via a 30" and 24" water transmission lines.
Crystal Spring
In the fall of 2002, the Crystal Spring Filtration Plant was completed. Using more than 1 million hollow polypropylene strands, the plant’s microfiltration system filters out all particles to 0.2 micron (one micron is one thousandth of a millimeter). With the capacity to filter 5 million gallons of water a day, Crystal Spring Filtration Plant is the largest microfiltration plant in Virginia.The plant currently filters about 4 million gallons of spring water daily. In 2003, Crystal Spring was awarded a Project of the Year award from the American Public Works Association. Crystal Spring was also honored with a 2003 Construction Management Achievement Award from the Construction Management Association of America.
Falling Creek Reservoir
Falling Creek Reservoir is a surface water source in Bedford County east of Vinton. It covers 21 acres and stores 85 million gallons of water at full pond. It is fed by Beaver Reservoir, which covers 69 acres and stores 435 million gallons of water at full pond. The treatment process of this water source is similar to that of Carvins Cove Filtration Plant. The treatment capacity of Falling Creek Filtration Plant is 1 million gallons a day.
In addition to the sources listed above, the Water Authority also maintains several wells that supply small areas of eastern Roanoke County. A small amount of water is also purchased from the City of Salem to supply a small area of Roanoke County west of Salem.