COVENTRY -- Two years ago, the $13-million Amgen Inc. sewer line project carried the promise of sewer service to a large swath of the town. It also brought headaches for merchants along Sandy Bottom Road and Washington Street whose customers had to negotiate an obstacle course to reach them.

Tomorrow, officials will hold a ceremonial groundbreaking to mark the start of a project to further extend that service -- and inevitably bring months of similar traffic disruptions to Tiogue Avenue (Route 3).

The 2004 project entailed building a five-mile main linking Amgen's pharmaceuticals complex in West Greenwich to the regional sewage treatment plant in West Warwick.

The new project will extend that line south on Tiogue from Hopkins Hill Road to Reservoir Road, then through the Ramblewood Estates Mobile Home Park, Colonial Acres and Pine Ridge residential developments. The project also includes adding sewer lines on Ray Street, on about 195 feet of Anthony Street and on Wood Street.

The $2.5-million project is being undertaken with a loan from the Rhode Island Clean Water Finance Agency, a state entity, that will be repaid with revenue from assessments that will be charged to households and businesses that the extension will serve, said Public Works Director Sheila M. Barrett.

Officials expect the project to be completed by the spring.

It was critical to get the project under way now, Barrett said, because the state Department of Transportation plans to begin a major overhaul of Tiogue Avenue next year. Once that work is done, she said, a five-year moratorium on any excavation work on the road would begin.

The Central Rhode Island Development Corporation, a nonprofit agency based in Warwick, is assisting Coventry with its sewer projects. It is helping the town pursue grant money and is working to keep local merchants and residents abreast of the project about to start.

"We have fielded a certain amount of outcry from the businesses, but that's normal with this type of construction," said George de Tarnowsky, the corporation's executive director. "It's going to block their parking. [Motorists] will have to go around. It will be awkward."

Tiogue Avenue's configuration in the project area varies. It is a three-lane road near Hopkins Hill Road and drops to two lanes and then to four lanes as it approaches Reservoir Road.

Barrett said construction crews will try to keep a minimum of two lanes open at all times. But she said there may be times when the highway will be reduced to one lane and detours will be in place.

Merchants are already anticipating a tough time.

One of them is Bill Tortolani, who manages the Smiling Sole, a wholesale fish market, on Tiogue Avenue near Hopkins Hill Road.

Tortolani said that his landlord is already connected to the Hopkins Hill line, so the project won't be a benefit. And he doesn't like the prospect of seeing Tiogue Avenue torn up twice, once for the sewer line and again for the highway upgrade.

"It's more suffering for the merchants," Tortolani said.

A few doors down, at Anthony's Liquors, owner Anthony Petrarca says the project will bring him sewer service. So he welcomes the impending work -- as long as customers can reach the store while it's in progress.

"I've been waiting 30 years for sewers. I think it will be a positive thing for Coventry. Tiouge Avenue will be able to expand and we can have fine restaurants and even hotels," said Petrarca, who is also a member of the town's Zoning Board of Review.

"If they do it right, businesses will have no problem."