The Leonard Lane facility is about two miles from the well in question, according to the DEP.
Research into PFCs is still emerging, but studies indicate that the compound is toxic to animals, resulting in adverse developmental and reproductive effects.
"The department believes the concentrations found at Paulsboro's Well #7 warrant actions," Karen Fell, DEP assistant director of water supply operations, wrote to the borough in the letter, dated last Friday.
Mayor W. Jeffery Hamilton in a statement provided Thursday said: "I am troubled that DEP did not provide any guidance for our residents until we demanded it."
Hamilton said he wanted to ensure residents would not be burdened by the cost of bottled water. Solvay officials said they were considering providing an alternative supply, but declined to discuss specifics.
A meeting between the DEP, Paulsboro, and Solvay on Wednesday was characterized as significant and positive by all parties.
The borough declared its intent to sue Solvay last week.
The 6,100-resident borough has grappled with an onslaught of environmental worries. In 2012, a freight train derailment released vinyl chloride into the air.
Last year, another water supply well was found to have high levels of radium, a naturally occurring and regulated metal. While an upgrade to that well's water system is underway, the borough continues to rely on Well No. 7.
Solvay said it ended its use of PFCs - often used to make water- and stain-resistant materials - in 2010. There is no state or federal maximum contaminant level for drinking water in place for PFCs.
Studies examining the water contamination in Paulsboro started as early as 2009, but the results showing elevated levels in Well No. 7 were not made public until last year, when the advocacy group Delaware Riverkeeper Network obtained records through the Open Public Records Act.
Brad Campbell, a former DEP commissioner and lawyer representing Paulsboro, said the borough did not act on a DEP notice at the time because officials were not informed of any potential concerns.
"People in Paulsboro have been drinking that water all this time," said Tracy Carluccio, DRN deputy director.
DEP officials "sat on their hands, and this is a disgrace," Carluccio said. She called the department "laggard" in taking the lead to rectify the situation and adequately educate residents.
For years, Carluccio said, residents have used household water to feed their young children.
"Those impacts on those infants could have been avoided if people had known," she said.
The DRN has asked the federal Agency for Toxic Substances and Disease Registry to step in, but the agency has not offered a final decision.
The organization also sent a letter to the DEP on Thursday, asking it to establish groundwater criteria for PFCs, including the type found in Paulsboro. The group also wants more extensive tests conducted to determine the contaminant's spread.