The Allegheny County Sanitary Authority will most likely need about $21 billion in the next 15 to 20 years to comply with a federal order to upgrade its storm water and sewer management system, according to an audit released yesterday.

Allegheny County Controller Mark Patrick Flaherty and city of Pittsburgh Controller Michael Lamb said their audit of Alcosan --from January 2007 to July 2008-- also revealed that the authority has not been complying with all of its contracting practices and procedures.

Both said the authority's funding troubles may lead to as much as a $3,104 annual rate increase for ratepayers in the Alcosan system if the authority doesn't receive any outside funding to help pay for its system-wide upgrade slated to start in about five years. Businesses served by Alcosan, they added, could see rate increases up to $25,000.

"You should be aware that in the future, your sewerage bill is probably going to cost more than your water bill," said Mr. Flaherty, adding that the amount of funding the authority needs over the next 15 years will be "the largest municipal project ever undertaken in our area."

Alcosan last year signed a consent decree with the federal Environmental Protection Agency, the state Department of Environmental Protection and the Allegheny County Health Department over charges that it has been discharging untreated sewage into rivers and streams for years.

Both controllers said that so far, the authority has complied with all the requirements of its consent decree, paying $1.2 million in civil penalties and is in the process of putting together a comprehensive Long Term Wet Weather Plan to be submitted to its regulatory agencies by 2013.

But John Schombert, executive director of the nonprofit 3 Rivers Wet Weather, said more than projecting cost estimates for the system's upgrade, the authority and regional leaders should focus their efforts on the process of how the terms of the consent decree will be implemented. Consolidation of the system, Mr. Schombert said, will most likely yield the biggest cost savings needed to upgrade Alcosan's storm water and sewer management plan.

"We are in the process of analyzing water flow as it goes through our system, but this audit is a good start in projecting the cost of upgrading the whole system," said Arletta Scott Williams, Alcosan executive director.