HAMMOND | The Hammond Sanitary District's customer communities of Griffith, Highland and Whiting may see a rate increase depending on the results of a new rate study the Sanitary District is eyeing.

Sanitary commissioners on Tuesday approved 2008 rate adjustments that comply with a complex cost-of-service model developed in the early 1990s, but indications are the model over the years has led to a wide divergence between what Hammond and Munster pay for water treatment and what their user communities pay.

Based on a far simpler model, District Manager Michael Unger calculated it costs an estimated $2.35 to treat 1,000 gallons of water in Hammond and Munster in contrast to 92 cents in Griffith, 87 cents in Highland and about 62 cents in Whiting.

The discrepancy led Commissioner Louis Karubas to request exploring an updated model.

"They're not paying their fair share," Karubas said of Griffith, Highland and Whiting.

Adding to the Sanitary District's frustration are indications the three communities' overuse of the system during heavy storms is contributing to Hammond's flooding problems.

Commissioner Russell Snyder, who represents Munster, suggested a new study could take the communities' overflow into consideration when setting rates.

Snyder said the study, once kicked off, could launch prolonged negotiations with the three communities, resulting in higher rates not taking effect until 2010 or 2011.

Meanwhile, efforts to lock the three communities into not exceeding their contracted usage are at a standstill.

A more than $8 million flood plan developed by Unger is set for discussion with the Hammond City Council at 6 p.m. March 5 at City Hall.