Rising water levels will likely delay repairs to a 160-foot-long landslide along the Lewisville Lake dam, a possible threat to the hundreds of thousands of North Texans who live downstream.
The U.S. Army Corps of Engineers said 16 inches of rain from severe thunderstorms over the Thanksgiving and Christmas holidays have caused problems with tarps they put over the landslide, The Dallas Morning News reported.
The corps, which manages the lake for the federal government, had planned to begin repairs on the landslide today. Lewisville Lake manager Rob Jordan said that’s now highly unlikely.
More erosion of the dam, rated by the corps as the eighth most hazardous in the country, is possible.
The massive landslide appeared in late June after record rainfall hit North Texas in May, Jordan said. The landslide is adjacent to another major slide that occurred in 1995, suggesting instability within the embankment.
Back then, large rocks covering the embankment and a section of the asphalt road along the crest of the dam came tumbling down toward the 2.3 million acre-feet of lake that provides electricity, drinking water and recreation for North Texans.
2015 was the wettest year on record in Texas and more waves of rain are in the forecast, leading some engineers to say the new slide could threaten the dam’s foundation.
The corps’ dam safety program manager, Sarwenaj Ashraf, said the corps developed a plan to repair the landslide by building a cofferdam around the damaged area to isolate the 23-foot-deep hole in the side of the dam caused by the landslide. But the plan was never carried out.
Three members of North Texas’ congressional delegation pledged to raise money to hasten the repairs following a report by the newspaper about the dam’s threat.
The corps estimates that permanent repairs will cost between $50 million and $500 million and would take several years.