HOUMA — Terrebonne Parish voters probably will decide May 4 whether to approve a property tax designed to pay for water service.

The Parish Council voted last week to put the 2.11-mill property tax on the ballot. The council must still ratify the measure Jan. 23 after a public hearing.

The tax is a requirement for Terrebonne to join the Bayou Lafourche Freshwater District, which supplies Terrebonne with 80 percent of its drinking water.

Al Badeaux, a member of the Terrebonne Waterworks District board, said the agency conducted studies to find alternate ways to get fresh water to parish residents.

Options included processing saltwater and reintroducing more fresh water from the Mississippi River into local bayous. None of the proposals proved to be more cost-effective than continuing to draw from Bayou Lafourche.

Terrebonne’s 40-year contract with the Bayou Lafourche water district expires in 2014. Terrebonne officials say costs are expected to rise afterward.

“We had a sweet deal for 40 years,” Badeaux said. “That’s running out.”

The parish now pays 3 cents per 1,000 gallons under the 1974 contract, or about $20,000 annually.

However, Badeaux said discussions with agency officials indicate it would likely jump to at least 35 cents per 1,000 gallons, more than 10 times the current rate.

Officials say joining the district — and paying the tax — would be cheaper than increasing water bills to pay the projected higher cost.