DENR lists dam in “high hazard” category

Polk County is being required by the state to do a special inspection of its Turner Shoals dam at Lake Adger that could cost $32,290.

Commissioners met Aug. 19 and heard from engineer Dave Odom who presented the board with two proposals for the inspection, one for the approximate $32,000 and another for approximately $50,000.

The N.C. Department of Environment and Natural Resources (DENR) sent the county a letter in June reviewing its annual visual inspection of the dam, which was done on April 24 this year. DENR’s letter, sent by Laura C. Herbert, PE, regional engineer, reviewed issues with the Turner Shoals Dam and is requiring a special inspection in addition to the required inspection every five years.

The letter stressed the importance of maintaining the dam, the dangers of dam failure and said that DENR continues to list the Turner Shoals Dam in the “high hazard” category.

“In the event of a dam failure, human life and significant property would be endangered because of the downstream location of NC Highway 9, other roads, and possibly residences,” Herbert said in the letter. “During this inspection we investigated the potential for property damage and loss of life in the event your dam fails. This investigation determined that failure of your dam could result in serious property damage and possible loss of life. Therefore, we continue to list your dam in the “High Hazard” category.”

The county continues to budget money annually for the known repairs needed to the dam after commissioners were told that future repairs are necessary.

Odom said over time the county knows it will have to complete repairs to meet new earthquake and flood stability requirements.

Issues noted by DENR included deterioration at various locations, seepage through many of the areas of deterioration and seepage along the toe of the bulkhead area and of the arches.
“Continued deterioration of the concrete undermines the structural integrity of the dam. Seepage contributes to the deterioration by leaching constituents of the concrete and promoting freeze/thaw damage,” said DENR’s letter.

Commissioners expressed concern that the two proposals for the inspection were so different in price. The lowest proposal of $32,000 came from AECOM, which has done the county’s last two reports on the dam. Black & Veatch provided the approximate $50,000 proposal and has also done a report on the county’s dam in the past.

Odom said he wasn’t sure why there was such a difference but recommended AECOM do the inspection. He said AECOM could be lower due to them having the most recent information on the dam. Odom also said he has told DENR the county has asked for proposals and doesn’t think the inspection is required immediately. He said the county likely has six months to complete the inspection.

Commissioners decided to table hiring a firm until its Sept. 9 meeting in order to determine why the proposals were so different.