Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: WEDNESDAY, February 15, 1995                   TAG: 9502150043
SECTION: VIRGINIA                    PAGE: C-3   EDITION: METRO 
SOURCE: JAN VERTEFEUILLE STAFF WRITER
DATELINE:                                 LENGTH: Medium

ENGINEER: DAM LEAKS NOT CRITICAL

"The seepage is more than we expected," said John Bradshaw of Hayes Seay Mattern & Mattern, "but we don't feel it endangers the function of the dam."

A $50,000 grouting job should correct the problem, he said.

Despite rumors that Spring Hollow Reservoir is leaking into underground caverns, there is more net inflow, or water staying in the reservoir, than engineers expected at this point. The reservoir is 65 percent full, with 900 million gallons.

As the reservoir continues to fill and more water is up against the dam, more seepage can be expected. Most of the leaks are around the abutments on the sides of the dam, which is where engineers want to grout.

The $73 million project has a $500,000 contingency fund for such work, Utility Director Gary Robertson said.

"We still have a good, stable, sound project for the valley," Bradshaw said. "There isn't a dam that doesn't experience seepage."

The Clifford D. Craig Memorial Dam, named after the county utility director who died last year, has a waterproof membrane across the front, so it leaks less than most dams, Robertson said.

But it's losing 250 gallons a minute, so slowing the seepage will be cost-effective over the life of the reservoir, which will hold 3.2 billion gallons when it's completely filled later this year.

Engineers have planned for water loss through evaporation and seepage. They expect that, when full, the reservoir will gain 1 million gallons a day from streams that feed into it. They figured that the acceptable net loss is 2 million gallons a day. Right now, it's losing a quarter-million a day. As the reservoir empties, water will be pumped in from the Roanoke River to maintain an acceptable level.

Engineers figured that the acceptable net loss for the reservoir - when full, it will lose water through evaporation and seepage, and gain a million gallons a day through streams that feed into it - is 2 million gallons a day. Right now, it's losing a quarter million a day.

About the rumors concerning underground caverns in the area, Robertson said the county spent more than $1million grouting them before the reservoir began filling. Monitoring wells are checked monthly, he said.

Filling the reservoir has taken longer than expected. From September through Thanksgiving, the Roanoke River was so low that no water could be pumped out of it into the reservoir. Since December, the county has been pumping water only at night to avoid high electricity prices in effect during peak hours through February.

And the reservoir is being filled 10 feet at a time and sitting for two weeks after each filling to monitor seepage.

Robertson said it should be full by summer.

Construction on the water treatment plant is beginning, and one phase of the county's water transmission system has been completed. Waterlines to Cotton Hill Road and to Steve Strauss' new subdivision near the Blue Ridge Parkway are finished. Three other phases are in the works in South County.

The route of the transmission lines in North County is being worked out, and utilities staff will meet with residents in March and April about acquiring easements. The north loop generally will follow Interstate 81, Robertson said.