New Hampshire's $92 Million Wastewater Treatment Plant Nears Completion

Jan. 28, 2020

Portsmouth, New Hampshire’s new $92 million wastewater treatment plant is nearing completion.

Portsmouth's new $92 million Pierce Island Wastewater Treatment Plant is on schedule for Apr.1 compliance.

“It’s been a long time coming,” said Public Works Director Peter Rice. “It’s been a significant investment of time and money and hopefully it will serve for 20 or 30 years.”

This comes 10 years after the state and federal government sued the city for discharging wastewater with E. coli and coliform bacteria into the Piscataqua River and South Mill Pond, reported the Portsmouth Herald

According to the federal lawsuit filed in September 2009, the old wastewater treatment plant had repeatedly violated limitations on the concentration of “five-day biochemical oxygen demand and total suspended solids” in wastewater discharged into the Piscataqua River. 

The treatment plant was built in 1964 and provided only “enhanced” primary sewage treatment, reported the Portsmouth Herald. The suit also alleged the city polluted South Mill Pond by discharging a mixture of storm water runoff and untreated sewage from its combined sewer overflows (CSOs) during heavy storm events. 

The litigation was resolved through a consent decree to separate storm water lines and build the new plant.

The city announced that general contractor Methuen Construction met a Dec. 31, 2019 milestone to achieve substantial completion of the biological aerated filter (BAF), which is the central component of the new wastewater treatment process.

Water is now running continuously through the new plant, the biomass is being developed and microbes are being concentrated in the tanks, reported the Portsmouth Herald. As new sewage is introduced, microbes will consume it and the wastewater will be disinfected.

Preliminary tests on effluent show levels of pollutants decreasing.

The final $91.9 million cost includes early planning, engineering and pilot programs. The old plant was incorporated into the new system and there is about a year remaining of construction for a lab/operations building.

Ratepayers won’t see a decrease in their monthly bills, however, according to the city. Terms of the state loan for the project call for no payment until a year after construction is complete and the new plant costs more to operate. Ratepayers can expect to see another sewer-rate increase, this time of 4%.

Included in the consent decree is also a mandate for a sewer line extension to properties near Sagamore Creek by June 30, 2022. How that will be funded remains uncertain, reported the Portsmouth Herald.

The consent decree also contains a provision saying Portsmouth agrees to spend $500,000, in annual $100,000 installments to support activities that advance the Great Bay 2020 vision.

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Cristina Tuser