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9/29/2025
WT Staff
 Got water questions? Give us a call at 877-52-WATER (877-529-2837), or email us at info@wtny.us
Tuesday, Sep 30, 2025 1145 am EDT
Return of freshwater mussels could be a sign of improving water quality in the upper Allegheny River
Pennsylvania's largest wastewater utility may just be proving that investment in a Clean Water Plan can pay environmental dividends. Sensitive aquatic creatures are making a recovery in the upper Allegheny River, a tributary of the Ohio River system. PA state biologists wading and exploring the riverbed found 35 freshwater mussels of various species, a positive indication that water quality downstream of the wastewater treatment plant has improved enough to allow for the return of nature's original water filters, the mussels.
See the full article by Abigail Hakas, here.
Today, Allegheny County Sanitary Authority (ALCOSAN) operates a regional wastewater treatment facility serving Pittsburgh and 82 additional municipalities. The massive operation treats an average 250 million gallons per day at the confluence of the Allegheny and Monongahela Rivers, the head of the Ohio River. A decade ago, ALCOSAN was taken to court by the PA Department of Environmental Protection and the Allegheny County Health Department for repeated and ongoing violations of the Clean Water Act (CWA). Combined sanitary and stormwater sewer collection infrastructure and treatment facilities can become overwhelmed during heavy rain events. These uncontrolled releases of raw sewage have had devastating effects on the receiving river, the drinking water supply for communities downstream.
ALCOSAN proposed to settle the overflow problem with a Clean Water Plan. The PA DEP and County Health agreed, the Consent Decree was approved by the US District of West PA judge in 2018. ALCOSAN's commitment, a "comprehensive, $2 billion, long-term plan to significantly reduce the overflows of diluted, untreated wastewater into the region's rivers" is enforceable by the court.
The remedy proposed for wet weather overflows, a critical component of the Clean Water Plan is a network of massive storage tunnels, 150 ft underground. Sixteen miles of tunnels are planned, the storage capacity is sufficient to manage 70% of the annual storm water volume. The utility is also committed to a plan of social engagement with the communities it serves, partnered with 600 educational institutions and organizations, offering facility tours, science and technology workshops for everyone.
Regional Model
Another critical aspect of the Clean Water Plan is the shift to a regional service model. From the website, "Regionalization involves the voluntary transfer of some of the largest municipal sewers and sewer facilities in the service area over to ALCOSAN ownership." Municipalities continue to maintain local sewage collection lines, sending the wastewater on to ALCOSAN's central plant for treatment and release to the Ohio River. Environmental compliance tasks are managed by ALCOSAN staff. ALCOSAN currently operates 90 miles of sewer, on the way to 265 miles when the plan is fully implemented. Streamlining of operations allows for the centralized management of the tunnel infrastructure, large enough for adults to walk through comfortably.
Since the Consent Decree in 2018, the Clean Water Plan and infrastructure investment have been promoted widely. A school locator tool on the utility website includes dozens of daycares, preschools and elementary schools. Municipal wastewater is apparently a hot topic for children, with dozens of hands-on science workshops and activities offered. In one such activity called, Drip, Drip, Drop! The caption reads, "Students will test a variety of materials to explore absorption of fabric." This activity is listed suitable for Grade Level Pre K with PA Standard(s): 3.2.PK.A6 under the Category Physical Sciences: Chemistry and Physics. Daycare centers listed on the ALCOSAN website do not appear to reciprocate in advertising a relationship with the wastewater utility.
The ALCOSAN Clean Water Plan will not prevent all wet weather sewage overflows, however the water quality appears to have improved enough to support the return of mussels to the river. The good news, reported by Next Generation Newsroom, there are now more mussels near the ALCOSAN outfalls than were surveyed in 1904. The summer biological survey shows concerted efforts by the state, the tens of thousands of mussel larvae released in the rivers is finally paying off. Picture tiny mussel larvae bumper-shining on the gills of fish until they are ready to drop off, grow a shell and make a life filtering river water. It remains to be seen if these fledgling mollusks will endure through the winter season. Stay tuned for an update in 2026.
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