SOMERSET — Activists opposed to a proposal at the Somerset Generating Station, on Riverside Avenue, to use plasma power to convert coal into synthetic gas yesterday renewed their warnings that the facility would eventually be burning trash, and they unveiled a plan to turn the property into a recreation and housing complex.

A rally on the issue, in the park on Slades Ferry Avenue, drew 13 people.

The owner of the plant, NRG Energy Inc., has repeatedly said it has no plans to burn trash — or construction or demolition debris — at the facility, formerly known as Montaup Point.

NRG would need a special permit from the state for that.

The $100-million conversion is supposed to dramatically reduce pollution at the plant, which is north of the better-known facility, Brayton Point.

Nonetheless, activists, including the Massachusetts Clean Air Coalition, keep insisting that waste incineration is going to happen there if residents allow the conversion to go through.

Alfred J. Lima, director of research for Green Futures, presented the artist’s conception of what the site might be used for if NRG left town and the area was cleaned and reclaimed.

It showed a waterfront promenade and walking path, a playground, playing fields, an outdoor performance area, a boat dock, and a “waterfront festival” area with shops, restaurants and 225 units of housing.

“We hope that Somerset has the chance to review the alternative and begin to make a choice as to whether it wants an incinerator at the Montaup plant site, which is very likely, or whether it should be looking at other alternatives over the long term that would add to the quality of life for Somerset residents,” said Lima.

gemery@projo.com