The Los Osos sewer project is experiencing several unexpected cost increases, but the overall project remains within its $173 million budget.
That’s the bottom line of a briefing the San Luis Obispo County Public Works Department will give the county Board of Supervisors on Tuesday. Supervisors receive periodic updates on the huge infrastructure project that includes installation of a collection system and construction of a wastewater treatment plant.
The engineering services contract for the collection system needs an additional $1.25 million and construction of the sewage treatment plant is expected to be $10 million more than originally estimated, Supervisor Bruce Gibson and Public Works officials told The Tribune on Friday.
These increases are due to unanticipated problems in the installation work and a less competitive bidding environment for construction projects, they said.
But the additional costs will be made up through contingency funds and the fact that bids for installation of the collection system came in $17 million under original budget estimates, said Paavo Ogren, county Public Works director.
Installation of the collection system began in September 2012 and is about 30 percent complete, said John Waddell, project manager. Installation is scheduled to be completed by July of next year.
The final phase of the project is construction of the sewage treatment plant. That portion is expected to go out to bid in September.
The collection system is being installed under three different contracts with the firm CDM Smith providing overall engineering services and design. Public Works is asking that the CDM Smith contract be increased from nearly $5 million to just over $6 million.
The increase is due to hundreds of requests by homeowners to change the location of their lateral hookups and conflicts with other underground utilities.
In order for individual homes to be connected to the sewer system, a lateral line must be installed from the property line to the main collection line. Since the project began, almost 600 requests have been received to change the location of the lateral connect point and that number could grow to more than 1,000, Waddell said.
During installation of the underground pipes, workers must avoid other existing utilities, including water and natural gas lines and fiber optic cables. Utility companies provided information about the location of these utilities and some of the locations were verified by exploratory digging.
“In many cases, the information provided by the utility companies has been found to be incorrect, and it has been necessary for CDM to change the sewer design to avoid conflicts with the existing utilities,” Waddell said.
Public Works is also projecting that the cost of the sewage treatment plant will jump by $10 million to $41 million. The plant will be built on a small plot of farmland behind the cemetery in Los Osos.
The increase is due to higher engineering costs as a result of the small lot size coupled with the loss of the competitive bidding environment the county enjoyed during the beginning of the sewer project which caused bids to come in lower than expected, Ogren said.
The county is also gearing up for a new challenge — the disposal of tens of millions of gallons of groundwater that will seep into the sewer line installation trenches dug in areas of Los Osos close to the bay where the water table is high.
Installation trenches range from 6 to 20 feet deep, which is below the water table in some areas. Water that seeps into the trenches can contain several types of pollutants, including nitrates, ammonia and bacteria.
State water officials have given the county permits to dispose of this water through a variety of means, such as land application, percolation ponds, dust control and into the bay, with the bay being the least desirable option, Gibson said. A small amount of dewatering has already been needed, but the bulk of the pumping will take place over a six-month period beginning later this year.
The supervisors’ discussion of the Los Osos sewer project is the last item on the board’s afternoon agenda Tuesday.