A former commissioner of the state’s Department of Environmental Protection testified Thursday that an environmental permit granted to a $2 billion casino slated for the Everett waterfront was a “clear outlier’’ and that state regulators should have required more concessions from the developer, Wynn Resorts.

“Given the size, mass, and location of the Wynn project, I would have expected a much larger and more robust mitigation package,’’ Robert Golledge said at a DEP hearing in Boston. “I think this mitigation package is essentially average.’’

Golledge testified on behalf of Somerville, which is appealing the DEP’s January decision to grant Wynn Resorts a waterfront development permit for the casino. The appeal, filed in February, has prompted Wynn Resorts to halt environmental cleanup work at the 33-acre property, just over the Mystic River from Somerville, and sparked a war of words between Wynn officials and Somerville’s mayor, Joseph Curtatone.

Curtatone, an unwavering opponent of the 24-story casino and hotel complex, contends that the size of the project, which is expected to draw some 18,000 cars a day, should dictate that Wynn Resorts take additional steps to offset environmental impacts.

Wynn Resorts, which says the casino will create 4,000 construction jobs and 4,000 permanent positions, wants a quick resolution of the dispute so it can remain on schedule for a late 2018 opening. Company officials have denounced the Somerville’s legal challenge as a “selfish, blatant attempt’’ by Joseph Curtatone to politicize the casino issue.

On Thursday, Tony Starr, a lawyer for Wynn Resorts, touted plans for a 6-acre park and 435-foot dock at the site as “extra benefits to the public.’’

The park is 2 acres larger than required under waterfront regulations, and the dock is almost 150 feet longer, Starr said.

Ben Lynch, a DEP official who first reviewed Wynn’s application, said the company had met all the requirements of the law. The agency’s top officials had also signed off on the project because of its size and “the amount of attention it had received’’ from the public, he said.

A single DEP hearing officer presided over Thursday’s hearing, and after reviewing written closing arguments from both sides will make a recommendation to DEP Commissioner Martin Suuberg. Suuberg is expected to make a decision in July or August, and could choose to set new conditions for the permit.

Both sides can challenge the DEP order in Superior Court.

As part of the development, Wynn plans to provide public access to the waterfront along landscaped paths and parks. Waterfront access is now highly restricted due to chemical contamination of the site.

But Golledge said the state’s failure to require water taxi service to the casino was “a major flaw.’’

“Water transportation has been a priority for years,’’ he said.

Last summer, the casino cleared a major hurdle when it secured a key environmental permit from the state, an approval that came after more than two years of analyzing traffic and other impacts.

That approval allowed Wynn Resorts to file for a waterfront development permit, the last major approval needed before it could begin construction. It received the permit in January, and Curtatone appealed within days.

As a result, Wynn suspended work at the site and held successive news conferences designed to ratchet up pressure on Curtatone to drop the appeal.

The news conferences featured pro-casino labor groups, mayors, and leaders of environmental groups, including the Environmental League of Massachusetts, the Boston Harbor Association, and the Mystic River Watershed Association.

But Curtatone vowed to continue his fight against the project, saying “no amount of public theater and political harassment will stop me.’’

In February, Curtatone said he was trying to get the best deal possible for Somerville residents, and that Wynn Resorts should pay for whatever measures are necessary to offset the influx of cars spewing exhaust in the city’s neighborhoods.

“I’m not saying money is not involved,’’ Curtatone said. “It will cost money to address the impacts on health and environment.’’

In response, casino developer Steve Wynn was blunt.

“The chances of the mayor of Somerville getting any extra money from us are zero,’’ he said at the time.

Sean P. Murphy can be reached at smurphy@globe.com. Follow him on Twitter @spmurphyboston.