ATTLEBORO - A $30 million, three-year reconstruction of the city's wastewater treatment plant has been completed on time and under budget.

The city's building commission designated the project "substantially complete" this week, meaning that 99 percent of the work is done, and all new equipment and machinery are operating as intended.

Jack Jacobi, chairman of the municipal building commission, the city's watchdog on major construction jobs, said it was "a very smooth project," compared with some others.

"It finished a month early, and with $250,000 in the till," Jacobi said. "It was a breath of fresh air."

Jacobi and the commission have scrutinized the construction of a half-dozen schools, a library addition, a fire station and the water treatment plant, but this job was remarkable for its lack of problems, he said. A cash surplus and no pending claims make the project a special success, he said.

The fact the project came in under budget will be a relief to ratepayers who are footing the bill for the job and have seen rates skyrocket from $2.72 per 100 cubic feet to $7.25 per 100 cubic feet, a 167 percent increase since 2003.

The city borrowed $30.2 million in 2003 to pay for the work.

The outside of the plant, which processes as much as 4.5 million gallons of raw sewage a day, looks the same, but all major machinery and electronic technology in the 27-year-old facility was replaced.

Work was completed on a piecemeal basis under a complicated plan that kept the plant running 24-hours-a-day, seven-days-a-week.

"It's been a long time, but everything went real well," said Wastewater Superintendent Paul Kennedy, who had high praise for the general contractor, Methuen Construction.

"They did a fantastic job. They were right with us every step of the way," he said.

One of the major additions to the operation is a computerized supervisory control and data acquisition system, which allows workers to monitor every function of the plant from one place and make adjustments as needed.

For example, adjustments to chemicals and aeration can now be made remotely. Before, they had to be done manually at the site of the machinery.

The system also records and stores all daily data generated at the plant and can retrieve it quickly for reference if needed. Formerly records were kept on paper and research required a lot of work, Kennedy said. Kennedy said the new equipment makes the plant much more efficient, and that he really enjoys coming to work now knowing that he won't be faced with an equipment breakdown, which happened frequently with the old machinery.

"Everything is brand new, so we won't be having breakdowns all the time," Kennedy said. "Before, we never knew what we were going to be walking into."

The new plant has a life expectancy of about 20 years, Kennedy said.

Kennedy praised his crew, which worked closely with the contractor, Camp Dresser and McKee, which designed the new system, as well as on-site CDM manager Mike Pappas for a job well done.

Pappas said smaller upgrades will likely be needed in the coming years because of increasingly stringent wastewater rules from the state and federal governments, but overall the plant is expected to function well for at least two decades.

"What is here now will serve the city well for 20 to 25 years," he said.

The former plant had a similar life expectancy.

GEORGE W. RHODES can be reached at 508-236-0432 or at grhodes@thesunchronicle.com.