Repairs needed to leaky Fort Jackson dam, Army says
By SAMMY FRETWELL | The State | Published: July 29, 2020
(Tribune News Service) — Fort Jackson is concerned about an aging, high-hazard dam that sparked safety questions as far back as 1979 and was in such poor shape that inspectors have found erosion and water seeping through the earthen structure in recent years.
Those are the highlights of a new federal report that says repairs at the Weston Lake dam are needed to keep the 49-year-old structure from failing. Following inspections in 2017 and 2018 that found problems, Fort Jackson made emergency repairs to the dam in 2019.
But those repairs were only temporary and a more comprehensive effort is needed, the Army says. The dam has had ongoing seepage problems in the sandy, easy draining soils of Richland County. Major concerns include problems with the spillway, a kind of chute that helps release water to prevent dams from breaking during storms.
The Weston Lake dam is near Leesburg Road, just uphill from neighborhoods populated by hundreds of people in eastern Richland County. It is classified as a high hazard dam because people downstream could die if the structure burst.
“Ongoing embankment seepage and the potential loss of highly erodible soils in the earthen emergency spillway during large flood events have reduced the reliability of the structure,’’ Fort Jackson said in a news release Tuesday. The release said repairs would “reduce the safety risk to downstream populations.’’
Fort Jackson officials did not respond to questions from The State over what the federal government has told the surrounding community about the dam’s problems.
The report, which said repair work won’t have much environmental impact, said water has seeped through the dam since Weston Lake was built in 1971. Dam safety inspectors identified problems in 1979, most notably that the emergency spillway was “grossly undersized” and the dam could be over-topped by more than three feet during a major flood, the environmental assessment report said.
The 2017 inspection noted “erosion, pin-sized boils and surficial slope instability,’’ while the 2018 report found “additional flowing seepage.’’
According to plans, the army wants to repair the Weston Lake dam, instead of rebuilding the structure. The environmental assessment report said building a new dam would take up to three years and cost $37.5 million.
The report did not say how much the preferred alternative to repair the dam would cost, but the plan calls for building a berm, or a type of embankment, near the existing embankment on the downside of the Weston Lake dam. The spillway would be upgraded with armoring, and a pool that serves the spillway would be reconstructed, according to plans.
Rep. Jimmy Bales, D-Richland, said he heard last year about problems with the dam and is glad the federal government plans to make more repairs. The work last year was minimal, he said. Bales said he doesn’t recall hearing of problems with the dam before last year.
“You don’t want the dam to be leaking,’’ Bales said. “That makes it potentially dangerous.’’
Weston Lake is a 173-acre waterway that is mostly used for recreation. It is the largest of 26 lakes and impoundments on Fort Jackson, according to a 2016 report for the U.S. Nuclear Regulatory Commission. In contrast, Semmes Lake, a reservoir whose dam broke in 2015, is about 30 acres.
The safety of earthen dams has been a high-profile issue in South Carolina since a historic 2015 storm swamped Columbia and other communities, causing flooding worse than many people could remember. More than 80 dams have failed in storms since 2015 across South Carolina. The dams serve smaller ponds and lakes, rather than major reservoirs.
Critics say the state’s bare-bones dam safety program allowed dams to go years without repairs. Questions have also surfaced about federal efforts to repair dams at Fort Jackson, which is not regulated by the state.
During the October 2015 storm, multiple dams burst in the Gills Creek watershed and other parts of Columbia. The failure of the Semmes Lake dam at Fort Jackson was blamed for flooding the adjacent Kings Grant neighborhood.
That dam is being rebuilt, but the safety of other Fort Jackson dams also has come into question. In 2016, The State obtained a federal inspection report showing that the dam at Weston Lake was among five dams on the military training base listed as in “serious’’ condition, the newspaper reported.