Peirce Island Wastewater Treatment Facility

Portsmouth, NH
Big changes on small island complicate Portsmouth, NH wastewater upgrade

The Peirce Island Wastewater Treatment Facility (WWTF) serves a complex sewer collection system dating back to the 1800’s. The nearly $100 million project is the largest public works project in Portsmouth, NH.


The upgraded facility, which involved work on six structures, needed to fit within the existing footprint, a fenced area of only 3.7 acres. Further compounding this was the challenge of getting construction materials and trucks on site through the 18th century streets of South End Portsmouth. Close coordination was required among all the design disciplines to maintain existing service throughout construction.


Given the extreme space constraints, the City’s Master Plan recommended consideration of high-rate, small footprint treatment technologies. Because these high-rate technologies have fewer installations than conventional type treatment technologies, the project team recommended piloting three different technologies on site. The final technology selection was based on a prioritized ranking of criteria including treatment performance and other characteristics.


Ultimately, a two-stage Veolia Water Technologies BIOSTYR™ Biological Aerated Filter (BAF) was constructed and began operation in early 2020.


2021 Associated Builders and Contractors of NH and VT Project Excellence Award and Chairman’s Award

2021 Water Environment Federation Project Excellence Award

Project Details




The City of Portsmouth, NH

Project Budget

$92 million


Design on this project started in 2013. The project was completed in 2021.

Services Provided by Petersen Engineering

Provided early identification of sustainability opportunities. HVAC, Plumbing and Fire Protection Engineer of Record.