Planning
HRG’s professionals guided this successful regional planning effort that included eight municipalities and authorities. The HRG team was instrumental in developing the solution to convey the combined communities’ wastewater to an adjacent municipal wastewater treatment plant (WWTP) and thus eliminating the burden of operating the two existing plants.
The Delaware Township Municipal Authority (DTMA) served as the lead municipal partner for the project to design and construct the new pump stations and force mains to convey the wastewater to a newly upgraded state-of-the-art WWTP located five miles away.
Pump Stations
The Watsontown Main Pump Station (submersible) replaced the aged Watsontown WWTP (ADF 0.32 mgd), which was constructed adjacent to the old plant and within the floodplain of the West Branch of the Susquehanna River. The significant design aspects included: precast, post-tensioned concrete structures for the wet well and wet-weather tank; elevation of electrical elements on a platform 11 feet above grade (and the 100 yr. flood level); and a 300,000 gallon wet-weather equalization tank.
The Dewart Main Pump Station (suction lift) replaced the nearing capacity DTMA WWTP (ADF 0.085 mgd) and was constructed using the existing building of the plant to house the new pump station equipment. The significant design aspect was the maintenance of the process operations during construction within the building, which contained the existing electrical power, controls, laboratory, blower and generator elements.
Force Mains
The force mains associated with the new pump stations included 7,500 LF of 8-inch (Dewart), and 26,500 LF of 12-inch (Watsontown) HDPE pipe. Nearing the destination Milton Regional Sewer Authority (MRSA) WWTP, the 12-inch force main was combined with the flows from the MRSA’s Front Street Pump Station (conveys 90% of the MRSA system flow). The force main pipe was increased to 20-inch C905 PVC for 3,000 LF to accommodate these combined flows. The entire 8-inch force main and 80 percent of the 12-inch force main located within the urban municipal streets of Milton was installed with HDD methods. The drilling alignment included the crossing of four streams that required elevation changes of up to 40 feet to complete. Plug valves and full-size tees were installed at each air-valve chamber to permit the isolation and bypass of any section of the force main in case of damage.
Gravity Sewer Replacements
Predesign video inspection of the critical sections of the existing gravity collection system in Watsontown noted that significant failures required correction to adequately convey the new flows. These failed portions of the gravity collection and interceptor system were replaced, resulting in a significant reduction of Inflow/Infiltration contributions
