The spillway for the nearly 90-year-old dam that forms Peters Lake needs upgrades with a preliminary cost estimate in the hundreds of thousands of dollars.
“And it’s probably never going to be used,” said Mark Zemaitis, Peters Township director of engineering. “I know that sounds jarring, but the fact is, the existing spillway can handle 98% of the storm events out there.”
The Pennsylvania Department of Environmental Protection, though, is requiring the township, as the dam’s owner, to bring the spillway into compliance with regulations governing adequate capacity.
As such, township council Monday awarded a professional services contract to Rizzo International Inc., headquartered in Pittsburgh, to determine an appropriate design.
Rizzo submitted a $61,645 cost proposal for developing an alternatives analysis and to help “negotiate with the DEP on what needs to be built,” Zemaitis said. The township’s 2021 budget contains an appropriation of $60,000.
Eventually, construction and associated costs could add up to between $200,000 and $400,000, according to an estimate mentioned to council by township manager Paul Lauer. Those numbers are based on what he and Zemaitis discussed with Rizzo International representatives during an interview conducted as part of the bidding process for the contract.
Township officials interviewed four firms. All were asked: “What do you envision as a solution?”
“And the solutions that three of the four came up with were spillways that will be millions of dollars to build,” Lauer said.
Funding for the project is anticipated to be a mix of local money and state grants, according to information in the request for proposals distributed for the professional service contract.
In 1932, Citizens Water Co. of Washington built what officially is called Canonsburg No. 2 Dam to form a reservoir. The dam was part of Pennsylvania-American Water Co.’s 1990s sale of property to Peters Township, which subsequently established Peters Lake Park at the site.
“Since the township took ownership, the dam has been inspected annually as required by the PaDEP with relatively minor repairs being required. The outlet works piping was inspected in the late 1990s, and the valve arrangement was modified in the early 2000s,” the request for proposals states.
The DEP, though, notified the township in 2012 that in the department’s opinion, the spillway lacked the capacity necessary to discharge the results of what is deemed probable maximum precipitation, the estimate of the theoretical maximum depth of precipitation that can occur over a specified area at a given time of year.
“My objection, which was shared by many other high-hazard dam owners across the state, has been that the modern design criteria requiring spillways to discharge the probable maximum precipitation storm event was unreasonable given the outdated nature of Pennsylvania’s statistical rainfall data,” Zemaitis wrote in an April 14 memo to Lauer.
“The PaDEP eventually agreed with the dam owners’ concerns and commissioned a new PMP study, which was completed by Applied Weather Associates and adopted by PaDEP last year. Now that the new study is complete, the PaDEP once again directed dam owners to bring their spillways into compliance.”
Nevertheless, Zemaitis cited one of the region’s heaviest recorded rainfalls, the September 2004 remnants of Hurricane Ivan, as raising the level of the lake to the point where two feet of freeboard, the vertical distance between the crest of the embankment and the water surface, remained above.
“That tells me that seven inches of rain with Ivan, it can handle a lot more than that,” he told council. “The PMP event is somewhere near 22 inches of rain, so we’ve got a long way to go.”