The Piscataqua River will be dyed red Monday night as Portsmouth studies how wastewater from a local treatment plant would affect shellfish harvesting.
The city will release a nontoxic red dye into the river along with treated wastewater from its Pease outfall. The study will last about 12 hours, starting Monday evening into Tuesday.
The flow of the dye will simulate how untreated wastewater would move in the river, if filtration at the Pease plant ever malfunctioned.
City officials say it’ll show what areas of the river in Portsmouth and Kittery, Maine, would be at the greatest risk for contamination.
The state will also use the study to find safe places for recreational and commercial shellfish aquaculture on the Piscataqua.
Similar dye tests have taken place in the past at wastewater plants around Great Bay and down the Seacoast.