The good news is that Crozet’s drinking water, drawn from Beaver Creek Reservoir and processed at the Crozet Water Treatment Plant, will be plentiful for the next 50 years or more. That was the message from Bill Mawyer, Rivanna Water and Sewer Authority (RWSA) executive director, and his colleagues at their June Crozet Community Advisory Committee presentation. From there, says the RWSA, the news only gets better.
“As we reported to you last year, the state of Virginia is requiring us to upgrade the Beaver Creek Dam spillway,” said Mawyer. “In connection with that, we wanted to take a long-range look at the water supply, because if we will be modifying the dam for safety issues, we also want to incorporate any needed water supply changes.”
Based on a study of forecasted population growth and water demand conducted by outside engineering consultant Hazen and Sawyer, the RWSA has concluded that the Crozet water supply will meet the community’s needs going forward. “We don’t have to raise the dam, we don’t have to expand the pool, we won’t have to look for alternative water sources for many years,” said Mawyer.
Drink to your health
Currently, there are two sets of water system improvements underway: (1) three ongoing projects at the Crozet Water Treatment Plant (WTP), and (2) three interrelated projects at the Beaver Creek Dam. Upgrades to the WTP on Rt. 240, first described in detail here in February, have progressed according to schedule. Those upgrades include the installation of granular activated carbon filters for cleaner water, now operational, at a cost of $3.4 million, and the construction of a new finished water pump station, now 90 percent complete and expected to be online by September, at a cost of $2.6 million.
Also at the WTP, a plan to significantly expand the plant’s treatment capacity, from 1 million gallons per day (mgd) to 2 mgd, is 95 percent through the design phase. That expansion is expected to be complete by 2020, at a cost of $6.9 million. Mawyer noted that none of these projects is funded by taxes. “All of our revenue comes from ratepayer water and wastewater service collection,” he said, referring to the monthly water bills that county residents pay to the Albemarle County Service Authority.
Water under the bridge
Over at Beaver Creek Reservoir, the dam modifications will use cutting edge technology and will be completed within the next three to five years, but will involve some inconvenience to local residents while in progress.
“Right now, there is a 200-foot-wide earthen auxiliary spillway designed to channel water during a storm so as not to overtop the dam,” explained Randy Bass of Schnabel Engineering, pointing to the grassy area just past the dam to the left of the roadway. “That spillway has inadequate capacity [by Virginia’s revised statewide standards], and due to erosion it would likely fail.”
After considering several alternative plans to pass through a greater volume of water safely during a major storm, the RWSA has settled on a “labyrinth spillway”—a concrete chute designed in a zig-zag pattern to accommodate more water—that will be constructed straight through the center of the dam. Browns Gap Turnpike, the roadway that currently runs across the top of the dam, will be rebuilt as a bridge over the spillway, which will require motorists to detour around the area while it is under construction.
“Though the spillway will take 18 months to build, we’ll try to minimize the length of the road closure as well as the temporary loss of the [Beaver Creek] park for recreation,” said Bass. The spillway may also be paired with a concrete parapet—a one- to two-foot-tall sidewall along the top of the dam on the reservoir side—which would serve as an inexpensive way to bolster the dam height for extra protection.
The second dam-related project will be the construction of a new raw water pumping station on the lower side of the dam to enable better control of the water’s flow than the current station allows. “We need to optimize reservoir storage with easier control of the sluice gates,” said Reed Palmer of Hazen and Sawyer, “and we need to pump enough water to the water treatment plant as well as control minimum in-stream flows.” The new plan includes motorized gates for remote water flow management.
The third project is a “cutting edge” way to improve water quality even before it is pumped to the WTP, says Jennifer Whitaker, RWSA Director of Engineering. “Beaver Creek Reservoir is constantly monitored for lake health,” she said, “and we plan to install a very progressive method for treating blue-green algae and nutrients in the water.” A new hypolimnetic oxygenation system will aerate the water using a pump that sits on the shore of the reservoir next to the pump station, and this aeration will allow for cooler, lower algae water delivery to the treatment plant.
In total, the dam projects will cost almost $21 million: $11.3 million for construction of the dam, $3.2 million for engineering, permitting, and easements for the dam, $5 million for the new, relocated raw water pump station and intake, and $1.1 million for the hypolimnetic oxygenation system in the reservoir. Mawyer assured the CCAC that the RWSA would keep the committee apprised of the projects as they evolve.
The design, permitting, and easement processes will run from now until early 2021, and construction is expected to be complete by early 2023.