An impending multibillion-dollar revamp of the Allegheny County Sanitary Authority is drawing the attention of both the Allegheny County and city of Pittsburgh controllers, who plan to jointly audit the agency.

City Controller Michael Lamb and county Controller Mark P. Flaherty announced yesterday that they will join forces to probe Alcosan's coming expenses and contracting procedures. They billed it as the first of many team efforts.

"For the first time, our offices, the city controller's office and the county controller's office, [will be] doing an audit jointly," Mr. Lamb said.

"I hope this is a framework that can be used time and time again," said Mr. Flaherty.

Alcosan will be their first joint project because its board is appointed by both county and city leaders, and because it faces state and federal mandates to reduce dramatically the flow of sewage into rivers during wet weather. "If [sewage overflow reduction] is not done, massive fines will be levied," Mr. Flaherty said.

He noted that estimates putting the cost of needed improvements at around $3 billion are now years old, and that generally, construction costs have gone up. Higher sewer rates are funding the early stages of the work, and without any easily identifiable federal or state help, Alcosan may have to boost rates much more to cover the more expensive projects to come.

Mr. Lamb said if the controllers can estimate a cost and calculate the rate increases that would be needed to bear it, that "should jump-start some action" toward finding outside funding. In light of the impending billions of dollars of contracts, his office will focus on Alcosan's contracting procedures. "We want to make sure that the process of awarding the contracts is a fair one," he said.

"We do welcome this, and we had a great first meeting" with the controllers in May, Alcosan spokeswoman Nancy Barylak said.

The two controllers said that in the future they could jointly report on city and county functions that could be merged.