Task force discusses role of South Fork Rivanna Reservoir in community water supply
At their latest meeting on October 13, 2008, the South Fork Reservoir Stewardship Task Force viewed two presentations on sedimentation as well as an explanation of how the South Fork Rivanna Reservoir will be used in the adopted Community Water Supply Plan. Questions were raised throughout the meeting about whether the task force is allowed to specifically recommend dredging to create more water storage capacity under the plan.
Podcast produced by Charlottesville Tomorrow * Player by Odeo
Listen using player above or download the podcast:
PUBLIC COMMENT PERIOD
Although the task force’s next meeting will be fully dedicated to receiving public comment, members of the public were also invited to comment at the beginning of this meeting. Charlottesville resident Leslie Middleton urged the task force to continue its course following its charge and to not be redirected towards a referendum on the adopted community water supply plan. But, the other seven people who spoke urged the task force to consider dredging as a way to restore storage capacity in the South Fork Rivanna Reservoir.
Tom Olivier, who represents the Piedmont Group of the Sierra Club, said nothing in the task force’s charge prevented the study of dredging. Former City Councilor Kevin Lynch insisted that the Four Chairs listed “water supply” as one of the public resources that the task force was meant to study.
“When our forebears built this reservoir back in 1964, they weren’t thinking ‘boy, we could use a better fishing spot,” Lynch said. “They were thinking we need a spot for water, and that’s why it was built.” He said the adopted community water supply plan was going to be too expensive, and urged for dredging to begin as soon as possible.
PRESENTATION ON SEDIMENTATION AND LAND CREATION
One of the stated tasks of the task force is to develop a timeline that plots out the “expected disposition” of the South Fork Rivanna Reservoir if no maintenance dredging is performed.
After Stephen Bowler’s presentation on sedimentation in the South Fork Rivanna Reservoir at the last meeting
, the County’s current Water Resources Manager, Greg Harper, gave a “back of the envelope” assessment of the reservoir’s future. Harper used aerial photography of the Ivy Creek area from 1974 and superimposed it over contemporary photographs to show where the sediment has collected in the reservoir. He also said that his low-tech and cost-effective study was not meant to address the reservoir’s capacity, but rather to discuss how its surface area has shrunk over the past 42 years.
Harper said his method shows there has been a loss of about 16% of the surface area of the reservoir since 1974, or about 6.4 acres. He also extrapolated out to 2057 and estimated that an additional 24% would be filled in as more sediment is deposited, an additional 9.7 acres. Harper said the forces at play as water pours into the reservoir are causing it to become more like a river.
Dede Smith of Citizens for a Sustainable Water Plan said it was her opinion that sedimentation would occur at a much faster rate than Harper had projected over the next 50 years. Harper acknowledged that his was just a prediction, but that it was certain that the reservoir would continue to fill-in.
Ridge Schuyler of the Nature Conservancy made a presentation after Harper, and detailed how one particular island has formed near Panorama Farm. He said understanding how sedimentation creates new land in the reservoir can help predict how it will change in the future.
“Somehow a tree stump or tree got washed down into the reservoir… and got stuck and then debris built up in front of it, and that debris then becomes a way of slowing down the water,” Schuyler said. He showed one image depicting a willow tree growing on land that did not exist in 1994.
Schuyler said the South Fork Rivanna Reservoir is historically a river system, and that the geology of the area continues to want it to return to that state. That means the reservoir will continue to get more narrow, until it reaches some sort of equilibrium, where sediment is carried further downstream.
Smith of said she appreciated the presentations from Harper and Schuyler, but said they were not expert analyses. She claimed “massive land formation” would occur within ten years.
“To just look at surface water is ignoring the fact that the sedimentation is happening under that water,” Smith said.
Mike Gaffney, chair of the Rivanna Water and Sewer Authority (RWSA) Board, said the river will reach equilibrium when it stops dropping sediment and sends it over the dam. Harper said that would not happen for a very long time, perhaps 200 years. After a discussion about whether the rate of sedimentation is increasing or decreasing, Smith said that dredging firm
Gahagan and Bryant
told her that water quality would decrease as the reservoir fills in.
FREDERICK EXPLAINS THE ROLE OF SOUTH FORK RIVANNA RESERVOIR IN ADOPTED PLAN
Tom Frederick, RWSA Executive Director, appeared before the Task Force to explain how the South Fork Rivanna Reservoir fits into the adopted community water supply plan. Before beginning, he told the Task Force they are looking at “all the issues related to the reservoir and are going to be making decisions about what types of maintenance, whether to dredge or not dredge based on a whole variety of issues and this is just one piece of a much bigger puzzle that you’re looking at.”
Under the adopted plan, the pipeline that carries water from the Sugar Hollow Reservoir to Ragged Mountain Reservoir is scheduled to be retired. Once that happens, Frederick says 99% of the urban water supply watershed will drain into the South Fork Rivanna Reservoir.
“Without the reservoir, there is no ability to provide the water for the future of the community,” Frederick said. A new pipeline would be built to carry water from the South Fork to the Ragged Mountain Reservoir. Frederick said a new intake will be built in order to boost the ability to take water from the reservoir. He said that during the community meetings held while the adopted plan was being created, maintenance dredging of the SFRR was encouraged.
“Dredging can certainly enhance the South Fork Rivanna Reservoir as a water supply resource, and can enhance water quality as well, but it’s not necessarily vital in the strict sense of the 50-year water supply need,” Frederick said. Future storage to meet the safe-yield target of 18.7 million gallons a day (MGD) comes with the expansion of the Ragged Mountain reservoir with the construction of a new 112’ dam.
“The water plan does not prohibit dredging in any shape or form. It just simply provides for enough storage so that if dredging did not occur, the public’s water supply would be provided,” he said.
Frederick said that when Gahagan and Bryant visited the community, they had identified that sedimentation of the South Fork Rivanna Reservoir is not an immediate threat to water quality, because the intake which draws water into the community water supply is located near the dam. Liz Palmer of the Albemarle County Service Authority (ACSA) said she pressed
Gahagan and Bryant
representatives for a more precise answer of when sedimentation would be a threat to water quality, and said she was told “75 to 100 years.”
Frederick said that water treatment processes are advancing to the point where sediment can easily be taken out before it reaches the water supply. Thomas asked if water treatment was more expensive after heavy rain storms because of the additional silt caused by stormwater. Frederick said it does costs more in chemical costs. The group discussed how sedimentation rates are affected by water volume and velocity.
Tom Jones, who is representing property owners around the South Fork Rivanna Reservoir, asked Frederick what steps the RWSA takes to prepare for expected high-volume storm events. Frederick says the RWSA runs water quality tests hourly, that the various pipes are sized appropriately to deliver additional chemicals for treatment, and that they maintain extra vigilance during storms. Jones asked if more water is released during major events. Frederick said Sugar Hollow Reservoir is generally dropped five feet in advance of major storm events, and that the South Fork Rivanna has an “unusually wide spillway” that can handle large volumes.
“If a maintenance dredging commitment is made, it’s important to remember that dredging alone does not meet the 50-year safe yield target that was set in the community water plan,” Frederick said. “The safe yield number with dredging followed by continuous dredging to maintain near original conditions is 14.3 MGD… That one alternative alone does not meet the demand. Certainly, dredging can increase storage from the South Fork Rivanna Reservoir as long as the total usable storage is the same, there can be some offset. If there’s more storage provided at South Fork because dredging has been employed, that can allow for a lowering of the Ragged Mountain pool, but it’s not by a significant amount.”
Frederick said if 2 million cubic yards were removed from the South Fork Rivanna Reservoir, that would allow for a new Ragged Mountain dam that would be 5 feet lower from the one that has received a permit from the
Army Corps of Engineers
as well as the
Virginia Department of Environmental Quality
. However, he said the status of those two permits would need to be reviewed if those changes were made to the adopted plan.
Dede Smith wanted more details on the second intake that Frederick is proposing be built. Frederick said the existing intake can draw up to 12 MGD, but averages between 8 to 10 MGD. The adopted plan calls for the eventual drawing of 16 MGD from South Fork Rivanna Reservoir directly into the water supply, as well as the expansion of the Observatory water treatment plant to take 10 MGD from the Ragged Mountain. The permit also calls for an additional 25 MGD to be taken from the South Fork Rivanna Reservoir in order to fill Ragged Mountain.
“The concept is to transfer water when there’s plenty of water in storage so that the downstream conditions are always maintained,” Frederick said. Required stream-flow releases are independent of pumping, and must be satisfied before any pumping can occur between the South Fork and Ragged Mountain Reservoirs.
DISCUSSION OF PUBLIC MEETING
At the public hearing scheduled for October 27, 2008, the Task Force decided to share a brief presentation about its role before taking public comment from as many people who want to speak. Members of the Task Force will be given the chance to respond to the comments as soon as all members of the public have had their chance to speak.
Regarding the task force’s charge, Tom Jones said he appreciated the presentation from Tom Frederick, but said there appeared to be a difference in opinion as to whether the group could discuss the water supply as a reason to dredge.
“I am not anxious to turn this task force into a referendum on the water supply plan or a group that is trying to come up with a new water supply plan, “ Jones said. But he added that dredging for other reasons would create additional capacity, and asked other task force members to comment on whether that should be factored in to the adopted water supply. He said the public might get confused if some members of the task force are seeking to alter the adopted plan.
John Martin, an ACSA Board Member who is representing the Rivanna River Basin Commission, said he has worked as citizen for ten years to help create the adopted plan.
“It’s over. The water supply plan is done. We’re talking right now about what to do with the reservoir.” That prompted a negative reaction from both Dede Smith and Wren Olivier, who is representing the Sierra Club.
Jones responded and said the pipeline to fill Ragged Mountain is a conceptual plan at this point, and there are many unanswered questions about its right-of-way and how it would be engineered. “I am willing to take it as a given… but if we’re not allowed to suggest things that would affect [the plan], like dredging… I’m not sure why we’re here.”
Liz Palmer, who also been active for many years to create the water supply plan, said the plan addresses a lot of issues such as aging infrastructure, and that the task force is not charged to look at all those details. Palmer acknowledged that dredging might achieve some additional capacity, but that the task force is not charged with making sure that those results meet the safe yield target. Dede Smith said a lot had changed with the plan, and that the
rising cost estimates
were causing a “financial black hole.”
Supervisor Dennis Rooker agreed the task force needed to respond to questions about why it was formed before the start of the public hearing.
“As I understand it, the green sheet that we had handed out to us at our first meeting set forward the charge,” Rooker said. The charge was given by the chairs of the City Council, the Board of Supervisors, the RWSA and the ACSA. Thomas asked RWSA Mike Gaffney Chair to explain how the charge was created. Gaffney said the
Four Chairs came together at a public meeting on June 30, 2008
to establish the task force. Rooker asked Gaffney who wrote the green sheet, and Gaffney responded that it was developed from the minutes, and the four chairs agreed to it via correspondence.
TIMELINE FOR PODCAST: