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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 updated Oct 8, 2025
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. More than 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 original Consent Decree approved by the US District of West PA judge in 2008 (editor's note of correction, this was originally reported 2018), a modified consent decree approved in 2020. The Consent Decree is, according to the document itself, "a judicial order, judicially-enforceable schedules and requirements for the development and implementation of a water-quality-based long-term control plan and associated tasks". ALCOSAN's commitment estimated $3.5 billion to implement, including, "to modify its operation and maintenance procedures, to revise its industrial pretreatment program, to eliminate sanitary sewer overflows, to meet certain monitoring and reporting requirements, and to cooperate with Customer Municipalities to develop area-wide planning and combined sewer overflow control activities."
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 Modified Consent Decree 2020, the Clean Water Plan and infrastructure investment have been promoted widely with a Scholastic Outreach and Education. A school locator tool on the ALCOSAN website lists dozens of daycares, preschools and elementary schools with a description of the 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.
WT contacted ALCOSAN media room to find out more about the programming offered for students, specifically, the interest and uptake in programming from daycare centers in Pittsburgh. Amanda Mueller is the Public Information Officer in Communications at ALCOSAN. We received an email response from Mueller, stating "Our scholastic program is an outreach program, we're not hosting young children at our plant..." The ALCOSAN website indicates special programming is supplied to students of all ages, "At ALCOSAN, we're not just treating wastewater – we're also dedicated to spreading knowledge and promoting sustainability. That's why we're committed to developing innovative and creative programs that encourage students, professionals, and communities to learn more about our wastewater treatment process." The Scholastic program has provided "free, hands-on programming to over 21,000 students from Pre-K to 12th grade at nearly 150 sites." On site, Mueller reports, "We do have crowds of all ages at our annual Open House event."
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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