The borough has been preparing to make costly updates to its wastewater treatment plant, but recent estimates suggest that the multimillion-dollar project could be over twice as expensive as anticipated.

Late last year, borough officials placed the project in the $3 million to $5 million range; the new price tag is over $12.5 million.

“This is considerably more than what we were planning on,” said Borough Manager Jeff Good. Construction costs are rising nationwide and the borough has had to adjust estimates on many major projects accordingly, but he still “wasn’t expecting that amount.”

The $1...