Firm provides lower estimate for phased concrete dam for Ragged Mountain
By Brian Wheeler
Tuesday, February 8, 2011
Black & Veatch
has revised its cost estimate for a concrete dam expansion that the city of Charlottesville is considering for the
Ragged Mountain Reservoir
as part of the
community water supply plan
. The overall price estimate has decreased by a range of $2.5 million to $3.4 million.
In a vote last month
, the City Council made a big step toward a regional water plan favored by Albemarle County by endorsing a significantly larger reservoir expansion. However, the details of the exact height and approach for a larger dam at the Ragged Mountain Reservoir continue to be negotiated.
“Previously, a 45-foot pool height increase was being considered,” said Greg Zamensky, an engineer with Black & Veatch in an interview. “Now 42 feet is the revised ultimate height increase, and we developed a proposal for that and for the 30-foot pool height increase now being considered [in the first phase].”
Black & Veatch now estimates that the first phase of a concrete dam extension could be built for between $10.6 million and $15.3 million to raise the reservoir pool by 30 feet, but with a foundation that could support the ultimate height. Including other cost factors if the dam is fully built, the total revised cost of the phased concrete dam would be $21.2 million to $26.7 million, based on the preliminary design concept.
“We have attempted to make these cost estimates as comparable as possible [to the earthen dam proposal],” Zamensky said.
The city and county have been at odds over the 50-year water plan, which was originally approved in 2006. County leaders favor a new earthen dam at Ragged Mountain Reservoir. City leaders have preferred building a smaller dam in phases on top of the existing dam, while adding dredging at the
South Fork Rivanna Reservoir
to bolster the water supply. Both localities support a new pipeline to fill Ragged Mountain from South Fork.
The cost estimate for the earthen dam design has also dropped significantly from earlier estimates.
showing how 1908 concrete dam (existing gravity dam) can be replaced with a phased earthen dam to raise reservoir by 42 feet (upper illustration) or in phases at 30 feet initially (lower illustration
, Thomas L. Frederick Jr., executive director of the Rivanna Water & Sewer Authority, said the construction costs alone for the earthen dam design had dropped to between $15.9 million and $19.5 million. Including other project expenses, Frederick has said that, from this point forward, the earthen dam would cost between $24.8 million to $28.4 million to build.
On Jan. 18, three of five city councilors endorsed a water plan featuring a dam at least 30 feet taller, a major concession to Albemarle, which wants the reservoir 42 feet higher. Before that vote, the City Council had advocated a much more modest reservoir expansion with a first phase height increase of only 13 feet.
voted to support the larger dam, one which she said should be more than adequate for the community’s water supply needs.
“We have made our big move and we are waiting to see what happens,” Szakos said in an interview. “In the city, we don’t need a lot of capacity beyond that. If the county wants the option [of a larger foundation] for further capacity later, that’s something the county will need to think about.”
Citizens for a Sustainable Water Plan
, has been a vocal supporter of dredging before construction of a larger dam. She has criticized the council’s 3-2 vote for the new alternative.
“The only thing [the City Council] said was that the dam would be no more than 30 feet higher,” Smith said in an interview. “They did not specify that it be earthen or concrete, existing or new. It was kind of lame really. It wasn’t exactly a rock-solid decision.”
Smith says she wants the council to get more information on the costs of dredging and of building on top of the old dam.
“I was disappointed to see the councilors back away from a more conservative and phased approach, because I thought that was in the best interests of the city,” Smith added.
City resident Martha Levering thanked the council Monday for its vote to increase the size of the dam.
“The recent suggestion to build [the dam] to its full height and only raise the pool level 30 feet is the more fiscally responsible plan,” Levering said. “The cost for building the reservoir pool 30 feet higher is 99 percent of the cost to expand it the full 42 feet. For the price of fuel and man-hours to move the extra dirt, we can spare future councilors from having to vote to tear up the land a second time.”
At least one member of the Board of Supervisors says he is open to the city’s proposal.
“We have clearly expressed what we thought was the best approach for the community, that is to go ahead and build an earthen dam,” Supervisor
Dennis S. Rooker
said. “It is a much better arrangement for the community to build it to the full 42-foot height, but if we are not able to get that, would I support 30 feet? I probably would.”
“It may cost us another $1.2 million or $1.5 million to build an expansion of the dam later, but I don’t think that’s so far out of line that we shouldn’t move forward,” Rooker said. “I certainly appreciate how far the city has come in their position, and we have an obligation to move this forward and not debate this interminably.”
The council’s discussion of reports by Black & Veatch and by
came after press time Monday. See Wednesday’s Daily Progress and the Charlottesville Tomorrow website for complete coverage.