Construction costs to clean up groundwater leaching from under a long-closed landfill in Los Osos keep oozing up higher and now top $1.8 million for the overall project.
County Supervisors approved a third contract amendment for $151,000 with the Jensen Drilling Company for the “Groundwater Extraction and Treatment System, Los Osos Landfill Project,” which entails the cleanup and monitoring of the groundwater leaching from under the Los Osos Landfill, which closed in the early 1990s after decades in operation.
In 1995, the County, which assumed responsibility for the landfill from the original owners, was ordered by the Regional Water Quality Control Board to clean up contaminated groundwater down gradient of the landfill (Order #95-66) off Turri Road.
But after decades of slow movement, the water board cracked down. “The RWQCB,” reads a County Public Works report, “is dissatisfied with progress of cleanup and is requiring more corrective action to further remediate the groundwater impacted by the Landfill, which is being addressed by constructing this groundwater extraction and treatment system.
“Advancing corrective actions to remove groundwater contamination are required to continue until volatile organic compounds [VOC] concentrations are reduced to background levels, which in this case is non-detect (zero). At a minimum, we must complete the project, and startup operation, testing and 12 months of reporting to show progress in complying with the RWQCB order.”
The water board reportedly said it would ease up on the throttle after the extraction system is up and running for a full year and the County has a full year of data on the groundwater, according to the report.
Jensen Drilling’s contract was originally for $777,000 to install several monitoring wells and cleanup equipment. There have been two previous change orders plus this recent third one and the contract is now up to $934,193.
The County anticipates there’ll be another change order for an additional $15,120 and so now estimates the final construction contract will top $949,300.
So what happened with the extraction system, which has already been installed? The County said, “During testing it was found that the groundwater flow rate to the wells is much higher than anticipated. As a result, the existing air compressor system does not have the capacity to adequately run the pneumatic wells.
“A new, upgraded air compressor system and associated electrical modifications are necessary to sufficiently power the wells to meet the Regional Water Quality Control Board permit requirements.”
The $151,000 change order reimbursed the contractor for the new equipment and its installation.
And it won’t end with the fulfillment of the water board’s cleanup order, as the County anticipates it could have to go on monitoring the old dump indefinitely.
“Until regulatory compliance is achieved,” the County said, “ongoing corrective actions will continue to be an unavoidable cost to the County. To reduce cost impacts, staff is researching and reviewing specific grant opportunities for supporting ongoing operation, monitoring and maintenance of groundwater remediation programs.”
