Wastewater and power cross-connections
The construction and subsequent disuse of power production facilities afforded some opportunities for wastewater and storm water management in later decades. As mentioned, the present wastewater treatment facility was constructed on the former site of the Adams Generating Station. One factor in choosing this location was the use of the Tailrace Tunnel for conveying treated effluent from the plant to the lower river. The tunnel would also accept storm water drainage collected at the new plant site through both the Ice Run Shaft and the former International Paper Company Tunnel connection downstream. The diversion sewer continues to convey storm water runoff and SPDES-permitted flows.
Above ground, the reuse of the site required the demolition of the powerhouses and paper plant structures. The inlet canals to both facilities had been filled to permit roadway, railway, and building construction. The foundation of Powerhouse Two was reused for the plant's chemical building, sewer maintenance garage and offices, and chemical storage tanks. A portion of the Powerhouse One foundation was covered, with the remaining northern section left open as a "planter." Bulkheads were also constructed to isolate the wheel pits from the tunnel, retaining fill within the pits.
The decommissioning of the Schoellkopf Station also led to the closing and filling of its 1923 tunnel inlet and outlet. The middle portion remained open, and presently receives storm water from the city's convention center parking area and nearby roadways. Water exits the tunnel through a low level drain connection to the Adams Tailrace Tunnel beneath Lackey Plaza. Runoff from other downtown streets flows directly into the tailrace tunnel through a shaft more recently installed between the plaza and the outfall.
An indirect connection exists between the upper river, the Power Authority's conduits, and the city's Falls Street Tunnel. The FST currently suffers from a high rate of infiltration into the sections immediately adjacent to cuts made for the conduits 40 years ago. The rock is highly fractured, allowing ground water to enter the tunnel about 30 ft below ground level; just 300 ft away competent rock provides a fairly dry tunnel. Recent isotope tracer testing has established a hydraulic pathway from the upper river, along the exterior of the NYPA conduits and into the FST. Historical FST flow data reinforces this relationship, correlating flow over the falls to river stage, local ground water level, and tunnel infiltration. Efforts are underway to conduct a grouting project to reduce or eliminate the leakage, since treatment plant discharge permit conditions require the full treatment of the tunnel leakage in dry weather. Removal of this 6 to 7 mgd would also greatly enhance first flush capture at the GPS and treatment plant. Similar grouting projects in 1989 and 1990 produced very satisfactory results.