BUZZARDS BAY — The developers behind a proposed hotel and conference center in Buzzards Bay took their longest stride to date Tuesday toward their goal of breaking ground on the project next year, winning an allocation of 27,108 gallons of wastewater output per day for the planned complex.

Bourne’s five sewer commissioners, who double as the town’s selectmen, voted unanimously to allocate those gallons to the Perry Ave. Corp. developers for the next year.

At the one-year mark, the commissioners will review the developers’ progress before deciding to continue reserving the 27,108 gallons for the hotel and conference center.

Now that they have the allocation in hand, Chris Bailey, a senior broker with Commercial Realty Advisors who is consulting on the project, said the developers have the confidence to refine the plans in preparation for planning board review. Bailey said Tuesday that the plans currently call for a four-story hotel with between 120 and 126 rooms.

Construction is expected to cost between $20 million and $30 million, and developers hope to complete the work by spring 2016.

“If they had gone in a different direction tonight, we would have been concerned. We’re thrilled with what they’ve done,” Bailey said, adding that the sewer commissioners’ rhetoric throughout the meeting showed a willingness to work with the developers.

With wastewater output capped at 200,000 gallons per day under an agreement with Wareham, Bourne sewer commissioners had raised concerns over the summer that an allotment for the development would bring the town too close to its daily limit. But in July, the sewer commissioners directed Town Administrator Thomas Guerino to investigate the possibility of reducing Hideaway Village’s daily allotment of 60,000 gallons to 25,000 — an amount closer to the Head of the Bay Road condominium property’s average output per day during the past decade.

Early last month, the state Department of Environmental Protection informed Guerino that the sewer commissioners have the flexibility to allocate daily wastewater flows as they see fit, opening 35,000 gallons for the town to reallocate.

Guerino met Thursday night with representatives of Hideaway Village, a cluster of condominiums off Head of the Bay Road, and described the discussion as “positive.” Peter Meier, a sewer commissioner and chairman of the Board of Selectmen, echoed Guerino’s praise of Hideaway Village representatives for “being willing to work with us.”

“In some ways, we’re pulling the rug out from underneath them,” Meier said. “Legally we could have still done it, but it could have been ugly in other ways.”

The developers had initially planned on building a $55 million mixed-use building with first floor retail space, 144 residential units and a rooftop restaurant with a seven-story view over Cape Cod Canal. But, to accommodate the town’s limited wastewater capacity, the developers offered to first build the hotel and conference center, which would require a smaller wastewater allocation.