As part of the long-term East Branch Dam Safety Initiative project, lake personnel continue to work closely with staff from the Pittsburgh District of the U.S. Army Corps of Engineers in overseeing the construction of a new cutoff wall inside the dam.
The $280 million project is in response to a safety issue related to potential internal erosion discovered in 2008, similar to a seepage issue encountered in 1957 which required the lowering of the lake for repairs. The multifaceted project has a completion date of 2017.
During a recent stakeholders' meeting, East Branch Park Manager Mike Setlock said staff is continuing to provide additional water to maintain downstream water quality and temperature along with real-time lake temperature.
As of Sept. 10, East Branch Lake is near 1,622 feet for its winter pool depth. The lake's original full pool is set at 1,685 feet with a summer pool of 1,670 feet and a winter pool of 1,651 feet. However, since 2008 the interim depths have been established at 1,650 feet for summer pool and 1,623 feet for winter pool. This year the lake reached its summer pool depth by mid-May.
"Part of the whole project that began in 2008 was the constant 24/7 monitoring which we're going to do through the entire cutoff wall construction," Setlock said.
A team of three maintenance trainees monitor the lake along with the assistance of permanent staff. A portion of the monitoring includes the daily reading of piezometers, used to measure liquid pressure specifically the height of a column of water. Staff also utilize inclinometers in the measuring of elevation, slope or depression of an object.
Setlock explained the piezometers' readings assist staff in determining if the lake depth is fluctuating and if so, by how much. This information is sent daily to Corps staff in Pittsburgh, who then advise lake personnel on a course of action.
A geotechnical investigation was completed in the spring, with the installation of instrumentation done in July. This fall a bid will be awarded for the automating of instrumentation for more instant data.
Mike Rattay, project manager from the U.S. Army Corps of Engineers, said project plans are on schedule. The Corps had a successful fiscal year in 2012 on the project.
"We have to be very careful during construction to have a proper safety plan and safety notification in place. This will be enhanced by having the proper instrumentation and the right people on the ground," Rattay said. "Safety during construction is key to our successful execution of the project. We have to be concerned about public safety in close proximity to the construction activities."
Rattay stated an environmental assessment has been completed addressing the project's risk reduction alternatives and proposed long-term risk reduction plan, along with bimonthly water quality analysis of the dam outflow and an aquatic ecology survey from May through October.