Report: Bigger South Fork pipeline won’t affect required size of new Ragged Mountain dam
By Sean Tubbs
Charlottesville Tomorrow
Thursday, July 30, 2009
At their meeting on July 28, 2009, the Board of Directors for the
Rivanna Water and Sewer Authority
was updated on the implementation of the 50-year
community water supply plan
, and heard the results of a study to determine whether a larger diameter pipeline called for in the plan would allow for a reduction in height of the new Ragged Mountain Dam.
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Board receives updates on water supply plan
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The 50-year community water supply plan adopted by the
Charlottesville City Council
and the
Albemarle County Board of Supervisors
in June 2006 established a requirement that the water supply be able to maintain a
safe-yield
of 18.7 million gallons a day (MGD) by the year 2055. That is the daily amount that could be safely be taken from the water supply while ensuring a reserve large enough to provide drinking water during the
worst drought on public record
.
The plan, which has received permits from the
Army Corps of Engineers
and the
Virginia Department of Environmental Quality
, would meet the 2055 demand by expanding the Ragged Mountain Reservoir to a total storage capacity of billion gallons. Currently the reservoir holds 464 million gallons. The new dam would need to be 45 feet higher in order to create the necessary storage. The Ragged Mountain Reservoir would be filled via a new pipeline from the South Fork Rivanna Reservoir.
However, the plan has been come under fire from some in the community who for various reasons would prefer to increase the system’s water capacity by dredging the South Fork Rivanna Reservoir to its original capacity. Since the fall of 2007, members of the group Citizens for a Sustainable Water Plan have put pressure on the Charlottesville City Council to reconsider the adopted plan.
Councilors and Supervisors both reaffirmed the plan in June of 2008, but not without reopening negotiations about some of the elements of the plan. In March 2008, City Council and the Board of Supervisors
held a joint meeting
with the RWSA and Albemarle County Service Authority (ACSA) boards at which it was decided that additional information was needed to provide better cost estimates to determine if dredging met the community’s needs while remaining cost-effective.
At their retreat in June, RWSA Board members requested a status update on the efforts to obtain the additional data on the elements of the community water supply plan. Frederick provided the following updates at the July meeting of the RWSA Board.
During the public comment period, Betty Mooney of the group Citizens for a Sustainable Water Plan said the RWSA staff was misrepresenting the wishes of City Council in the way the dredging feasibility study is being characterized.
“The City is
paying for studies
not for opportunistic dredging or for selective dredging or for recreational dredging, but for full restorative dredging to possibly be part of the long-term solution for our 50-year water supply plan,” Mooney said. “The City has clearly said they want the dredging information to make a cost comparison to the dam-pipeline concept and that is why they are paying for a large part of the study.” Mooney said one of the proposals makes no references to restorative dredging. City Councilor Holly Edwards now represents Council on the RWSA Board.
Mooney also called upon the RWSA to revisit the demand analysis conducted in 2004 by Gannett Fleming that established the safe-yield target of 18.7 MGD for 2055. She and other members of her group argue that the community will need less water in the future because of better technology and education about water conservation.
Bigger South Fork pipeline won’t decrease necessary size for new Ragged Mountain dam
At the March 2008 meeting of the four boards, Mayor Dave Norris asked for a study to be conducted to determine if the size of the new Ragged Mountain Dam could be lowered if a larger diameter pipeline could be installed to connect the South Fork Rivanna Reservoir to the Ragged Mountain Reservoir. The theory was that the community could have enough water supply to withstand a drought if the Ragged Mountain Reservoir could be filled more quickly.
The RWSA hired Hydrologics, a water resource management firm based out of Raleigh, North Carolina, to study the issue. Their engineers conducted a series of simulations in which different pipeline sizes were tested using the same meteorological and hydrological data from previous droughts. They concluded that diameter of the pipeline would have no bearing on the necessary storage needed in the entire water supply system to meet the projected safe yield demand of 18.7 million gallons a day in 2055.
Download the report from Hydrologics
Dede Smith of Citizens for a Sustainable Water Plan accused the RWSA of doctoring the report, claiming that they had issued a Freedom of Information Act request to obtain correspondence between RWSA officials and Hydrologics. Tamara Ambler, Water Resources Manager for the RWSA, explained that the document was edited to make it more clear to the public.
“I can guarantee you that no factual changes were made,” Ambler said. “I’m not an engineer and one of the things that I think is important given public scrutiny is that we make sure that reports written by engineers can be understood by people who are not engineers.”
Other news from the meeting:
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