HDR Engineering’s February 2010

Dredging Studies

By Brian Wheeler

Charlottesville Tomorrow

Thursday, March 4, 2010

Critics of the long-term water supply plan, approved by Charlottesville and Albemarle County in 2006, said Wednesday that dredging of sediment from the

South Fork Rivanna Reservoir

could be completed for $10 million and satisfy all of the community’s water needs for the next 50 years.


Citizens for a Sustainable Water Plan

announced their projections after reviewing the initial dredging feasibility studies completed by

HDR Engineering

for the

Rivanna Water and Sewer Authority

.

RWSA Executive Director Tom Frederick, however, said that the HDR studies completed thus far provide no information on the cost of dredging or final numbers on the volume of water storage that would be made available.

“I think at this point in the study, it is premature to draw conclusions,” said Frederick.

At a Wednesday news conference to announce the citizens group’s reading of the dredging study, former City Councilor

Kevin Lynch

said on behalf of the group that the study showed neither a new dam nor a new pipeline is needed.

“The analysis of the reservoir shows … the conditions are much more favorable to dredging than even we thought,” said Lynch. “The reservoir has much more water in it than we originally thought. It has been filling with sediment much more slowly than we originally thought. And it will take much less dredging to get it back to its original usable volume.”

The

water plan endorsed in 2006

would cost more than $140 million and includes construction of a higher dam at Ragged Mountain Reservoir and a new pipeline to carry water from the South Fork Rivanna Reservoir to Ragged Mountain. It does not include dredging.

Dredging is one component of a water-supply alternative that has been advocated by Charlottesville Mayor Dave Norris, but even the so called “Norris Plan” includes a new pipeline and additional storage via expansion of the existing dam at Ragged Mountain.

In an interview, Frederick said the HDR report also leaves open questions about wetlands at Rivanna.

“We have yet to learn or understand what the limits of dredging the reservoir might be with respect to wetlands and we need to fully understand that issue.”

“If the wetlands are disturbed, it would have to be mitigated,” said Frederick. “If we are going to protect the wetlands, we can’t restore the original volume of the reservoir and HDR has not yet quantified the net gain in volume from the dredging that could take place.”

HDR identified 45.6 acres of wetlands that have formed in the reservoir since it was built in 1966. The firm recommended protecting the wetlands with a “no-dredge buffer zone along the reservoir shoreline.”

Lynch said any water plan would incur additional costs to repair the existing Ragged Mountain Dam, maintain the Sugar Hollow Pipeline, and build additional water treatment capacity.

While the original water plan would abandon

the pipeline used to carry water

from the

Sugar Hollow Reservoir

near White Hall to the

Ragged Mountain Reservoir

, Lynch’s alternative would continue using that pipeline, and would not build a new line between the Rivanna and Ragged Mountain reservoirs.

“Nobody is so naive to think that other improvements won’t need to be done to the system over the next 50 years,” said Lynch.

Those costs are not included in the group’s $10 million estimate for dredging, which Lynch said was based on an unsolicited 2004 dredging proposal from Blue Ridge Sand Inc., adjusted to reflect HDR’s findings and inflation.

The RWSA is hosting a public input meeting on the first phase of the dredging feasibility study on March 9 at 6 p.m. in the CitySpace meeting room in the Market Street Parking Garage.

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