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Rocky stream to cascade down Highland Park
Thursday, January 03, 2002 By Lillian Thomas, Post-Gazette Staff Writer
By fall, a winding, rock-lined stream will cascade through a series of small ponds behind the reservoir in Highland Park and flush out the stagnant Lake Carnegie below.
It could have been a concrete culvert with concrete blocks in it, but designers decided against ugly.
The babbling brook project -- a name used jokingly in early discussions that seems to be sticking -- came about through informal discussions about what to do with water used to rinse the filters of the new microfiltration plant being built behind Reservoir No. 1, said John Kasper, senior project management engineer for the Pittsburgh Water and Sewer Authority.
"It's one of those things that came up in discussion with a lot of people," said Kasper. "Any water processing plant produces various waste streams. Some are only waste streams in a very stringent sense of the term" -- in this case, water with a higher concentration of chlorine and algae than of drinking water. "We realized if we treated it slightly, it would be a wonderful addition to Carnegie Lake, which has a tendency to be stagnant."
"Air-stripping," or aerating the water is one good way to dissipate the chlorine, he said. "And exposing it to organic materials is another good way to get stuff out. A good way to do both is run it over rocks in a stream. You can do it with a concrete channel with concrete blocks, but it looks pretty ugly. Since it's in the middle of a park, we wanted to do something that would fit in better."
Kasper said the authority can pay only for work that is necessary to a project. It can pay for a retaining wall, for example, but not for stone facing to make it more attractive.
"I can do it as long as it doesn't cost more than the concrete channel. It's not that I have to make it ugly, but I can't spend [extra] money to make something look good."
But if someone else pays the extra cargo for the aesthetics, Kasper can make it happen.
Cost of digging the approximately 1,000-foot-long channel and basins will be about $100,000, he said. But the Pittsburgh Parks Conservancy will use grant and donation money to pay for the cost of much of the project's aesthetic elements.
The stream will begin below a concrete chamber across from the filtration plant. Storm water from the plant, the access road and two small buildings that border the reservoir will be collected in one 10- to 12-foot pond, which will cascade into a second pond of about the same size. Runoff from the plant will flow into that second pond. The stream will wind down a steep slope, and there might be a path or stairways alongside it. Just above the steps that lead to the Highland Park swimming pool, it will go underground into a hidden catchment and then into Carnegie Lake. The lake has a drain, so the regular infusions of water should keep it clearer and fresher.
The city of Pittsburgh is building a new pump and filtration system to distribute water in the city rather than cover the reservoir as the federal government had wanted. It is scheduled for a spring start-up, though Kasper expects up to a yearlong "shakedown" period in which adjustments to the system will be made.
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