PROVIDENCE, R.I. – Giant tankers carrying liquefied natural gas through Narragansett Bay could cause traffic backups, hurt tourism and marine economies and slow emergency response times, according to two studies released Tuesday.

The studies focus on how the economy and traffic would be affected by LNG tankers heading to the planned Weaver’s Cove Energy terminal in Fall River, Mass., which has been approved by the Federal Energy Regulatory Commission.

The studies were conducted by two independent companies for the Aquidneck Island Planning Commission, a regional group composed of the cities of Middletown, Newport and Portsmouth. The commission has not taken a position on the LNG proposal, although the communities have each joined a legal fight against it.

Newport Harbor would be blocked for at least 20 minutes each time a tanker passes because of the wide security zone required around the ships, according to the economic impact report by Lincoln-based Pare Engineering Corp. Weaver’s Cove has said it initially plans 50 to 70 tanker voyages per year.

That would restrict use of the bay several times a week during the boating season, and could result in the loss of major regattas and the Tall Ships festival. It could also damage the city’s reputation as a tourist destination – one of the region’s largest industries.

Jamestown Harbor would also be affected, as would the narrow waterway spanned by the Mount Hope Bridge farther north.

Also, the tankers could conflict with testing at the Naval Undersea Warfare Center in Newport, where the U.S. Navy tests torpedoes and sonar. The Navy asked FERC earlier this month to reconsider its approval of the Weaver’s Cove project.

Gov. Don Carcieri, who opposes the project, said the studies reinforce his view.

“LNG tankers traversing Narragansett Bay would have a significant negative impact on neighboring communities,” he said.

Spokesmen for Weaver’s Cove Energy did not immediately return messages for comment.

While public concern has centered largely on the fear of an explosion or attack, the reports examined other potential consequences of LNG shipments on the water.

“This has nothing to do with terrorists or tankers blowing up or anything,” said Keith Stokes, executive director of the Newport County Chamber of Commerce. “This has to do with our vision over the next 10 years for the economy of Aquidneck Island. This just doesn’t fit.”

If the terminal is built, tankers the size of three football fields would enter the bay’s East Passage between Jamestown and Newport with little advance notice, the Pare Engineering report said.