PORTSMOUTH — City officials have identified two potential sites to replace the contaminated city-owned Haven Well at the Pease International Tradeport, according to Deputy Public Works Director Brian Goetz.

The two sites that the city is beginning its initial study on to see if they are suitable for city wells is a combination of city-owned and private land in the Great Bog area of Portsmouth and property located in Greenland near Interstate 95, Goetz said.

“For the sake of the private landowners, we won’t release exactly where the Greenland property is” until the city gets to the point where it is negotiating to buy the land, Goetz said Monday.

The initial survey work that will be done on both sites involves trying to determine if the properties are a good site for wells before they start drilling, Goetz said.

“They have electronic equipment like solar equipment that sends signals down into the ground to decipher how deep the aquifers are and where the bedrock is,” Goetz said.

The city is searching for a new well because in May Air Force tests showed the presence of perfluorooctane sulfonic acid, or PFOS, in the city-owned Haven Well. PFOS is one of a class of chemicals known as PFCs, or perfluorochemicals. PFOS are organic chemicals that have been used in a variety of commercial and consumer products, such as stain and water repellents, fire fighting foams and nonstick cookware, according to the Environmental Protection Agency.

The EPA classifies PFOS as a “contaminant of emerging concern because the risk to human health … may not be known,” according to the federal agency’s website.

Tests done by the Air Force Civil Engineer Center found that one private well in Newington had elevated levels of PFOS and levels above the EPA’s provisional health advisory level, but tests on other area wells came below below the provisional health level.

Officials believe the PFOS found in the Haven Well — which is located near the main runway — came from firefighting foam used in drills.

City officials have reached a memorandum of agreement with the Air Force concerning the contamination of the Haven Well.

The Air Force has agreed to pay the city $154,000 for the initial costs to find a new water supply, according to Deputy City Attorney Suzanne Woodland.

“The city has supplemented the Pease water system from other sources, but if the Haven Well cannot return to use, as is anticipated, a new supply source must be found for the long term,” Woodland said in a recent memo to City Manager John Bohenko.

The $154,000 will be used to reimburse the city “to complete hydrogeological studies on potential water supply sites,” Woodland states in the memo. “A new groundwater source in New Hampshire normally takes two to five years to bring into service.”

The Air Force also agreed to pay the city $26,000 in reimbursement fees for the cost of hiring Weston & Sampson, which was hired by the city after Air Force officials discovered the contamination.

“The agreement expressly reserves the right of the city to request additional funding including funding for geological investigations, permitting efforts, land acquisition and construction to bring a new well on line,” Woodland states in the memo.

Goetz said ongoing testing at sentry wells around the Haven Well are “trending toward almost non-detectable levels” of PFOS.

“They’re located around the Haven Well,” Goetz said about the testing wells.