The $8.1 million environmental assessment is to examine effects of noise and vibration, air pollution, social and economic changes, and historic-preservation efforts.
Federal and state agencies asked the engineering firm STV Inc., which is conducting the study, for "additional field surveys for threatened and endangered species and historic resources," said Joe North, project manager for STV.
North said publication of the draft version of the study "is now projected for later this year."
After the draft study is published, a 45-day public review and comment period will precede the issuance of a final version of the impact statement.
If the project gets the go-ahead from federal and state officials at that point, construction could start in 2016, and trains could be running on part of the line by 2019, according to STV.
But significant questions remain on how the line would be paid for or who would operate the trains.
The Delaware River Port Authority is overseeing the ongoing environmental studies, but DRPA officials have said the agency will not pay for or run the rail line. NJ Transit has not committed to paying for it or operating it.
Preliminary plans call for trains operating every 71/2 minutes during peak hours and 15 minutes during nonpeak times.
Trains would operate until midnight, and as many as 18,000 daily riders are expected by 2030.
The line would run alongside a Conrail freight line through Glassboro, Pitman, Mantua, Wenonah, Woodbury, Deptford, West Deptford, Westville, Bellmawr, Brooklawn, Gloucester City, and Camden.
It would connect to PATCO and River Line trains at the Walter Rand Transportation Center in Camden, where passengers could catch trains to Philadelphia or Trenton.
A trip from Glassboro to Camden, with 14 stops, would take from 34 to 40 minutes, planners estimate.