By Brian Wheeler
Charlottesville Tomorrow
Wednesday, June 2, 2010
Charlottesville has hired its own engineering firm to study repairing and raising the existing
Lower Ragged Mountain Dam
as an alternative to the replacement earthen dam
recently proposed
by
Schnabel Engineering
.
Black & Veatch, headquartered in Kansas, was one of five firms to respond to the city’s request for professional services. The study of the dam is expected to cost up to $348,695. Charlottesville’s utilities director, Lauren Hildebrand, said that the first phase will cost about $200,000 and the second phase will be pursued only if necessary.
“We are going to look at what the maximum height is to which we could raise the dam,” Hildebrand said. “If one of the options appears to be feasible, then we will move forward with the second phase.”
Hildebrand said the project was
authorized by Charlottesville’s City Council in January
, and the
contract
, which was signed May 26, does not require further council approval. Funding will come from the city’s utilities budget. Albemarle County is not contributing to the cost of the study because the approach is not part of the 50-year
community water supply plan
approved in 2006.
City resident
Bob Fenwick
said in an interview that he would prefer the city invest in dredging the
South Fork Rivanna Reservoir
.
“Until we do dredging, anything else is an unnecessary expense,” Fenwick said. “The whole point of this is good water for us, for businesses, for growth, for the benefit of both the city and the county. If that is really the goal, you should do the simple things first, and I guess I have to keep making the case for dredging first.”
Schnabel Engineering
recommended last week
that the
Rivanna Water & Sewer Authority
build a massive earthen dam just downstream from the current Lower Ragged Mountain dam, which was built in 1908. The new dam would raise the reservoir’s water level by 45 feet, as contemplated in the 2006 plan, and submerge the old dam.
RWSA Executive Director Thomas L. Frederick Jr. has said that a decision to move forward with the earthen dam could lower its cost in the current construction market. The earthen dam currently has an estimated cost of $28.5 million and $36.6 million, which includes final design and engineering work, an environmental mitigation plan and protection of the Interstate 64 embankment, which the larger reservoir will reach.
Albemarle County Supervisor
Kenneth C. Boyd
, a member of the RWSA board, said he was concerned about the time needed for additional studies.
“I am still concerned given the construction atmosphere we are in,” Boyd said. “People tell me they can’t believe we are not moving forward with a dam concept that has been approved when doing so now could save us up to 30 percent on construction costs in this market.”
In February 2009, Charlottesville Mayor
Dave Norris
suggested that instead of building a new dam, the existing dam could be raised by 13 feet as a way to provide sufficient water storage at a potentially lower cost. The so-called Norris Plan relies on a combination of this refurbished dam with dredging, increased water conservation and a new supply pipeline to South Fork.
The City Council has indicated that it wants to know the cost and feasibility of building the smaller dam before it makes any final decisions on the water plan’s next steps. Two other water studies are already under way related to the costs of dredging at South Fork and a review of the demand analysis that is the basis for the 2006 plan.
Norris has said the City Council will have the information it needs to make a final decision when these studies and the new project by Black & Veatch are completed.
“I have no interest in prolonging this debate for many more months and years,” Norris said in a recent interview. “It needs to be decided by summer or early fall.”
Hildebrand said the first phase of Black & Veatch’s study of the existing dam would take about four months and that staff had determined the project was necessary even with the recent proposal for an earthen dam.
“We still need to answer the questions that council has identified,” Hildebrand said. “We are going to do the initial alternatives development, then some of the subsurface investigations. If the subsurface investigation proves that one of the alternatives will be feasible, then we will look at costing that out.”
Black & Veatch will conduct subsurface borings of the 1908 dam and its earthen buttress, which was added in 1934, to build on past research conducted by a previous consultant. Gannett Fleming studied upgrading the dam in 2002-03. The firm identified safety issues with both the spillway and the potential for instability of the earthen buttress.
In its 2003 report, Gannett Fleming said, in part: “The earthfill buttress has lower than acceptable factors of safety against rotational failure under both static and seismic loading conditions. Permanent repairs are therefore required to satisfy current dam safety criteria.”
An independent panel of dam experts recently reviewed engineering data for the Lower Ragged Mountain Dam, including a safety report that raised concerns about the structure as early as 1913. The 102-year-old dam has a conditional operating certificate from Virginia dam safety officials. Last month, the Soil & Water Conservation Board approved a six-month extension that allows continued use of the reservoir until November. At that point, the RWSA has to update the board on the community’s progress repairing or replacing the dam before it can get another extension.
Charlottesville officials have maintained that the dam is safe and even emphasize in the
statement of work
for the Black & Veatch study that the dam and buttress meet “current structural stability criteria.” The city and RWSA both agree there are safety issues with the dam’s spillway.
“The research that I have done and the reports I have seen reassure me that the existing dam is safe,” Norris said at a
Charlottesville Regional Chamber of Commerce luncheon in January
. “What we heard from Gannett Fleming was that it was not the stability of the dam itself, it’s the spillway that needs to be repaired. The dam itself is going to be quite safe for decades to come.”
Hildebrand said the second phase of the Black & Veatch study, including conceptual plans and cost estimations, would take eight to 10 weeks after one or more alternatives for raising the dam is selected for further study.
