KeySpan announced details of its proposed merger with National Grid Monday, including an increase in prices.

According to KeySpan, the company will institute a one-time increase in the price it charges customers to deliver natural gas by 2.8 percent, or about $5.70 a month per household. The company said the increase, which will come two years after the deal between National Grid and KeySpan is finalized, is necessary to pay for increases in property taxes and medical costs for employees totaling about $60 million. After the one-time increase, the price for gas delivery will be frozen until 2012, representing a single increase in 16 years, KeySpan said. The possibility of rising costs is a concern to some Long Island residents.

?Already in the summertime we are paying extra with the air conditioning running constantly,? said local business owner Antonietta Caruso. ?Any increase would be terrible.?

Suffolk County Legislator Wayne Horsley is worried about how the merger will affect the cleanup of Long Island toxic gas manufacturing sites. He expects the cost of those cleanups to be around $1 billion and fears Long Islanders may get stuck with the bill.

?What they have got to do is come to the table and make that part of the deal,? said Horsley. ?Otherwise, frankly, we are going to pay, and that is insulting.?

State approval on the deal is still pending, but the state Public Service Commission is expected to discuss it at an August 22 meeting.