The Altoona Water Authority plans to have inspections done on the pair of inflatable rubber dams attached to the tops of the spillways at Lake Altoona and the Impounding Dam near Horseshoe Curve, after discovering signs of wear.

An authority worker who noticed a compressor running more frequently than normal at the Impounding Dam conducted a leak test on the rubber dam there that proved positive, and officials have noticed “serious signs of decay and rubber cracking” on the dams, said general manager Mark Perry Thursday.

“It’s shaping up we (may) need to replace them,” said Perry of a possible project that with materials and installation could cost three-quarters of a million dollars, according to Perry and consulting engineer Mark Glenn.

In preparation for such a project, Glenn has reached out to a company in Germany that manufactures rubber dams, which are used to add capacity to reservoirs, Perry said.

The ones currently in place near the Curve were made in China and were installed seven years ago.

The previous rubber dams they replaced lasted 30 to 35 years and were still operable even then — needing to be taken down only because of their age, Perry said.

They were manufactured by Bridgestone, a Japanese company, which no longer makes rubber dams, according to Perry and online sources.

The current rubber dams are “clearly inferior,” Perry said.

The 134-foot-long rubber dam at Lake Altoona raises the spillway top by four feet, adding 116 million gallons of capacity, Perry said.

The 117-foot-long rubber dam at the Impounding Dam raises the spillway top by five feet, adding 65 million gallons of capacity, he said.

The additional capacity the rubber dams provide is important to the authority, especially in times of drought, according to Perry and Glenn.

It’s an inexpensive way to add capacity, Perry agreed.

The additional capacity provided at Lake Altoona alone is nearly equivalent to the total capacity of the authority’s Plane 9 reservoir, Perry said.

There have been rubber dams on the spillways of Lake Altoona and the Impounding Dam since the 1960s, Glenn said.

The current iterations are the third — and the shortest-lived, according to Glenn.

The rubber of the dams is perhaps a half-inch thick and reinforced with fiberglass, according to Glenn and Perry.

They’re inflated at low pressure — about four pounds per square inch, Perry said.

Mirror Staff Writer William Kibler is at 814-949-7038.