Repairs sought to stop groundwater that costs Alcosan every month
On a dry summer day, most of the water that flows into the Allegheny County Sanitary Authority's wastewater treatment plant has no business going there.
It's not sewage. Alcosan doesn't get paid to treat it but pays to treat it anyway.
About 60 percent of the 200 million gallons that flow to Alcosan each day during dry weather is groundwater.
Alcosan couldn't say how much it spends to treat groundwater or how much it costs to treat even 1,000 gallons of water, but if groundwater were an Alcosan customer, its bill would be about $20.2 million a month this year for dry months and $22.4 million a month after a rate increase that takes effect Friday.
The groundwater either seeped into sewer systems in Allegheny County through old, crumbling, leaky pipes or from streams and creeks that were rerouted decades ago from their natural paths to the rivers into the sewers, said John Schombert, executive director of 3 Rivers Wet Weather, a Lawrenceville water quality nonprofit that recently finished a $500,000 study on the issue.
Solving the groundwater problem could go a long way toward solving Alcosan's overflow problem, Schombert said. But it won't be easy.
“In decades, we could take on this problem. There is not an overnight solution,” Schombert said. “It's not simple, and it's disruptive.”
Gray or green?
Jan Oliver, director of regional conveyance for Alcosan, said she thought Schombert's 60 percent figure seemed a bit high but agreed groundwater flowing to Alcosan is a problem. In terms of reducing overflows from the sewage system into the rivers, giant tunnels under the rivers and expansion of Alcosan's North Side plant will handle most of it. Addressing groundwater is a second-tier solution, she said.
Alcosan is under a federal court order to cut the 9 billion gallons of wastewater and stormwater that overflow into area rivers each year to a range of 4 billion to 5 billion gallons by 2026. The authority will raise rates Friday — the third increase in a row — to begin paying for the $2 billion to $3 billion fix.
Alcosan's original plan includes tunnels under the rivers to store wastewater and stormwater during heavy rains, a so-called “gray” solution. Environmental activists and some public officials, including Pittsburgh Mayor Bill Peduto and county Executive Rich Fitzgerald, have called for more environmentally friendly “green” solutions in the plan, such as rain barrels, green roofs, rain gardens and permeable pavement.
Alcosan officials have been negotiating with the Environmental Protection Agency for most of the year to include more green solutions and get more time to complete the project.
Schombert said that while the solution to groundwater infiltration is gray — fixing or replacing old pipes, rerouting streams out of the sewers and back into the rivers — the result is green as the reclaimed groundwater will recharge streams.
Old pipes, older maps
The groundwater problem for Alcosan and many of the 83 municipalities it serves is twofold: old pipes and rerouted streams.
About 75 to 80 percent of 4,200 miles of sewer pipes are terracotta. As the pipes crack, leak and deteriorate, groundwater seeps in and eventually ends up at Alcosan's treatment plant, even though it does not need to be treated. Laterals leading from homes to the sewer also allow groundwater into the system.
The second cause was inherited. An old map of Pittsburgh or Allegheny County will show many small streams tumbling toward the rivers. The streams don't exist on newer maps. As the region developed, streams, some of which were the original sewers, were routed into the system.
Part of the problem is measuring the problem. Alcosan studied how much water was flowing into its system and from where in 2008. From that study, Alcosan generated a list of communities that were sending the most water into its system.
This year, Schombert's organization installed monitors in some of those communities to measure how much of the flow wasn't wastewater or stormwater. The meters measured flow between midnight and 5 a.m., when most people are sleeping and not flushing the toilet, in February, March and April, Schombert said.
The $500,000 study found that 80 percent of the flow comes from 20 percent of the sewer system, Schombert said. It will help municipalities determine which pipes to repair or replace to keep the largest amount of water out of the system.
“This now gives the municipalities the tool if they (want) to go in and spend their money wisely on flow reduction.”
Some, however, question how effective it is to spend money on keeping groundwater out.
David Montz, Green Tree's borough manager, likened repairing old pipes to taking thimbles of water out of the system — while separating combined sewer systems, where stormwater and wastewater flow in the same pipe, could remove barrels.
Tim Rogers, manager in Shaler, said his municipality spends about $400,000 a year lining pipes to keep out groundwater. The work eliminates only hundreds of gallons of water.
“It's not a good bang for the buck,” Rogers said.
Alcosan has taken the lead in addressing the second part of the problem.
In 2010, Alcosan, Pittsburgh, Bellevue and Ross completed an $8.5 million restoration of Jack's Run. The project removed 200 million to 250 million gallons annually from the sewer system. Alcosan treats just shy of 70 billion gallons a year.
The project returned the stream to the Ohio River. It cleaned up debris, improved the slope, stabilized the bank, recreated natural stream features and brought in new topsoil and native plants. More than 600 feet of the stream that once ran through a pipe underground was “daylighted,” meaning the pipe was cut away, exposing the water.
“In the end, you did have a huge problem resolved,” Oliver said.
Alcosan has completed what it calls stream removal projects along Pine Hollow in Stowe, Kennedy and McKees Rocks, in Carnegie Park in Carnegie, along Orr Street in Stowe, and near the former Millvale Industrial Park. A project at Sheraden Park in Sheraden is in progress. Projects along Ravine Street in Sharpsburg and Dooker Hollow in North Braddock are scheduled to start next year. The projects combined could cost $24.5 million and remove 785 million gallons a year from the system.
Aaron Aupperlee is a Tribune-Review staff writer. He can be reached at 412-320-7986 or firstname.lastname@example.org.