The new sewage plant planned for Piru could go back to the drawing board, after the bids to build it came in at nearly double what the county of Ventura was expecting to pay.

The Ventura County Board of Supervisors will be asked today to reject all five bids on the project and send it back to the Public Works Agency to be redesigned. Contractors' bids on the project ranged from $17 million to $19.2 million, far above the county's estimate of $9.9 million.

If the board agrees, the county will try to design a new plant that will cost about $12 million. That would keep Piru residents' sewer bills about $80 a month, up from their current level of $57 a month, said Reddy Pakala, the county's director of water and sanitation.

The county must have a new plant up and running by February 2009, or by February 2010 if the Los Angeles Regional Water Quality Control Board grants a one-year extension. The regional board has the power to fine the county if it is still using the old plant, which releases pollutants into the Santa Clara River that exceed state standards.

If the county redesigns the project and asks for new bids, the plant will probably be finished around the end of 2009, Pakala said.

The first estimates were so high in part because the cost of materials is constantly rising, he said. The county's estimate also called for the new plant to be built where the existing one is now, and that turned out to be more expensive than anticipated.

"What we found out is the treatment plant we designed with existing land was very difficult to construct," Pakala said. "So, what we are considering is looking into buying land next door, so we can keep the existing plant operating while constructing a new plant. We believe that will keep the cost lower."

The county might also revisit its decision to use a filtering technology called membrane bioreactors. It's more expensive than some other choices, but it uses less land and releases cleaner water.

It may turn out that buying more land and using a different method will be cheaper, Pakala said.

The sewage treatment plant is on 1.2 acres, and the county could buy another 3 acres. It is one of the smaller plants in the county, processing about 240,000 gallons of sewage per day. The new plant would have a capacity of 500,000 gallons per day.