Dam experts say renovation of existing dam requires more significant study
By Brian Wheeler
Wednesday, November 24, 2010
An independent panel of dam experts says there is insufficient information to determine whether building on top of the 1908 Lower
Ragged Mountain Dam
should be considered as part of the
Charlottesville-Albemarle water supply plan
Three dam experts met for two days with local officials and dam engineers to evaluate a
prepared in July by
Black & Veatch
at the request of Charlottesville leaders. That feasibility study said the existing dam could be raised to increase the water level by 35 to 45 feet.
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“I think the panel’s discussions were very constructive,” said Thomas L. Frederick Jr., the executive director of the
Rivanna Water & Sewer Authority
, in an interview. “There were one or two areas of disagreement between [the panel and Black & Veatch], but it was more an acknowledgment of differences of opinion.”
The panel’s findings were presented Tuesday to the RWSA Board of Directors.
Daniel Johnson, vice president of Tetra Tech, Golden, Colo., and a member of the panel, said in an interview that the body concluded it would need more information before it could advise whether to expand the existing dam or build a new one.
“We don’t have the information to make that decision now,” Johnson said. “If the costs end up being close together, it’s always better to go with new technology rather than an old system.”
In his presentation to the RWSA board, Johnson outlined areas that could increase the Black & Veatch cost estimates, some relating to deficiencies in the design
identified as far back as 1913
. For example, he said the panel recommended a grout curtain be installed beneath the existing dam to limit seepage if the renovation option was pursued, something not included in the Black & Veatch proposal.
Other grouting applications, excavation work and the widening of the road leading to the construction site were all areas that Johnson said could raise the cost of renovating the existing dam.
Black & Veatch reported in August that a 45-foot increase in the reservoir pool could be accomplished for between $21.4 million and $27 million. The firm also reported that the existing dam could be raised 13 feet for a cost between $9.9 million and $13.1 million or just repaired for $6 million to $7.9 million. There are no cost estimates for phasing the construction from one height to another.
Charlottesville’s City Council
voted in September
to expand the existing
Ragged Mountain Reservoir
as part of a revised water plan by building a new or renovated dam in phases, beginning with a 13 foot height increase. No preliminary engineering has been completed on a concrete extension of the existing dam.
Albemarle County, however, has stuck by its preference for
a new earthen dam
to be built all at once, raising the reservoir by 42 feet. The Albemarle County Service Authority is paying Schnabel Engineering to complete the final design work on that earthen dam, which has an upper cost estimate of about $40.7 million.
Greg Zamensky, an engineer with Black & Veatch who participated in the panel’s review, responded to questions from the RWSA board.
“We need a chance to go back and look at the extent of their comments,” Zamensky said. “As it stands now, I can’t tell you how I could respond to each of those points or how it would impact the cost.”
Judith Mueller, the city’s director of public works, said she believed that the Black & Veatch proposal merits further study. Zamensky said his firm could spend several weeks responding to the panel’s major questions.
told the RWSA board he wanted Black & Veatch to respond to the panel’s feedback in order to update the cost estimates.
“I think they have their marching orders to walk through all the points that were raised in the [panel’s] review,” Norris said.
Frederick began the board meeting by asking for “clear direction” from the policy makers about the specifics of the community water supply plan. No verdict was reached at the meeting.
“I think the judgment that the board really needs to make is a gut call as to what is in the best interest of the community,” Frederick said in an interview. “The question is, do we spend more time and money to find out if this option should be pursued? It’s a judgment call they will have to make.”
Norris reiterated that he thinks the city is close to wrapping up its review of this option for an enlarged reservoir.
“It’s really the last major sticking point between the city and county on how to proceed,” Norris said after the meeting. “We will get this report back in a couple weeks and at that point we will be able to make a decision as to whether we want to see the dam renovated or replaced.”
At a meeting in Richmond last week
, the Virginia Soil and Water Conservation Board granted a six-month extension for continued use of the Ragged Mountain Reservoir through May 31, 2011 on the condition that construction permits be issued for the dam’s repair, renovation or replacement by the end of May 2011.
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