On Wednesday, the state of New Jersey issued three permits to the Williams Transco company allowing them to begin construction work on the natural gas pipeline project that will run through the environmentally sensitive Princeton ridge and parts of Montgomery.

The $650 million project would add a 42-inch pipeline to an existing line. Transco needed permits for freshwater wetland and flood hazard areas from the Department of Environmental Protection before beginning construction. The project is part of the 6.36-mile Skillman Loop that will transport gas to produce enough energy to heat about two million homes, according to the company.

Construction is scheduled to begin May 1. Gas in the existing pipeline will be shut off for safety reasons. Clearing of trees for the pipeline expansion began last month.

In February, a public hearing where numerous concerns were raised by local residents resulted in several changes made to Transco’s application. The company plans now to tunnel beneath stream and wetland areas instead of digging open trenches.

The Princeton Ridge Coalition, a residents’ group, said last week that the permit approval process was being rushed to conform with Transco’s schedule. The NJ Sierra Club has also commented that the approval was being rushed. The Sierra Club is calling for a full Environmental Impact Statement about the project, saying it will destroy wetland, forests, and cause flooding.