When county Supervisor Sally Thomas met with dredging consultants Gahagan & Bryant Associates last month about the possibilities of dredging the South Fork Rivanna Reservoir, they said the first question to answer was, Why are you dredging?
“That’s a very obvious sort of thing, and yet it was also kind of eye-opening,” says Thomas. “Ever since then, I’ve been using it as a mantra. We’ve got to know why we’re dredging before we go into this dredging business.”
 The South Fork Rivanna Reservoir is losing about 1 percent of its capacity per year because of siltation. |
Now that City Council has reaffirmed its support of the 50-year water supply plan, which involves involving a bigger dam at the Ragged Mountain Reservoir and a new pipeline from the South Fork Rivanna Reservoir, local officials face a decision about maintenance dredging the South Fork Reservoir. Because of its large, 259-acre watershed, that reservoir has been silting in rapidly since it was created in 1966, at a rate of approximately 1 percent per year. It has never been dredged.
Dredging means sucking out that silt, but the process is complicated because there has to be a site to dewater and store the sediment, which could be resold depending on its contents and the market for fill material. Those uncertainties have complicated cost estimates. Possible reasons for dredging include expanding its capacity for potable water storage; clearing out lanes for rowing and other recreational activities like fishing; and preventing potentially smelly wetlands from building up and decreasing property values for those who live around the reservoir.
As part of its resolution reaffirming the water supply plan last week, City Council included a call for the Rivanna Water and Sewer Authority (RWSA) to “undertake a study of the South Fork Rivanna Reservoir and the viability and merits of maintenance dredging, siltation prevention and any other appropriate initiatives” that would improve the reservoir, and asked that the county do the same. At the supervisors’ June 4 meeting, the Board kicked around the idea of adopting the same resolution about dredging passed by City Council, and will likely approve similar language at its June 11 meeting.
Mike Gaffney, chairman of the RWSA board, says that the organization’s No. 1 goal is to provide water and wastewater services to the city and county. “This is a little bit outside of that goal, but our two customers and their customers pay for everything we do,” says Gaffney. “So if they asked us to do [dredging studies], we’d certainly want to do that. We truly are committed to the long-term viability of South Fork Rivanna Reservoir and certainly maintenance dredging should be a part of that.” He says that RWSA will need direction from the county, but that the topic will likely be discussed at the Board’s June 23 meeting.
To answer the “why” question, Thomas envisions a meeting of major stakeholders—South Fork residents, RWSA, the county Parks & Rec Department, rowing clubs, the Ivy Creek Natural Area, and other city and county officials. “I’m not in favor of a great, long, dragged-out taskforce,” Thomas says, “but I tend to think in terms of a visioning session or two in which we all lay it on the table why we want dredging.”
Ken Boyd, chairman of the Board of Supervisors, plans to meet with city Mayor Dave Norris to figure out how to move forward. Norris wants RWSA to go ahead with a sediment study of the South Fork, which would cost at least $100,000, as soon as possible. He believes that conversations about why we should dredge happen concurrently rather than holding up the study.
Norris also thinks that dredging could make for a lower dam at Ragged Mountain. “If in that [dredging] process, we’re going to free up, even inadvertently, some water supply, then I think we have an opportunity there to save some money on the height of the dam and save some trees and acreage [at Ragged Mountain].”
But Tom Frederick, RWSA’s executive director, says that the final decision of the dam’s height needs to be made in the coming months. Consulting firm Gannett Fleming is in the midst of designing the base of the new dam, but “there will come a point in the coming months where we have to complete the design and put the project out to bids,” says Frederick. “What is the height we’re actually going to build? At this point, we haven’t been given any direction other than to build it to the full height.”
 “I’m not in favor of a great, long, dragged-out taskforce,” says Supervisor Sally Thomas, “but I tend to think in terms of a visioning session or two in which we all lay it on the table why we want dredging.” |
One big question looming on the horizon is who pays for dredging. RWSA is funded by ratepayers—water users in the city and county—and it makes sense for them to foot the bill if it’s only a question of providing adequate water supply. But if key drivers to dredge include recreation or county property values, then part of the bill could go to area taxpayers.
“I’m not sure that the bill for maintenance dredging should be paid through the water rates,” Gaffney says. “I think that may need to be paid through something else. But again, that’s part of the discussion that we need to have.”
C-VILLE welcomes news tips from readers. Send them to news@c-ville.com.