The Carson City Board of Supervisors will take its first major steps toward expanding and improving the city's wastewater reclamation and treatment system Thursday.
City Engineer Larry Werner said the process has gotten much more complicated since expansion of the treatment plant was first put before the board in 2001.
"Initially we were not going to worry about nitrate removal," he said.
But new and tougher environmental standards under the federal Clean Water Act require the city to include nitrate removal in its new wastewater reclamation plant.
Those changes added several million dollars to the cost of the project, bringing it to an estimated $14.5 million. And they necessitated a $537,493 expansion of the contract with Carollo Engineers of Las Vegas to design the project, bringing the total design contract to more than $1.3 million.
That contract change is before the supervisors Thursday along with an agreement with the federal EPA to monitor and mitigate seepage from the Brunswick Reservoir. EPA is contributing $192,000 to the monitoring program. The city's cost is $157,418.
To actually perform the monitoring, the board will be asked to expand the contract with Berryman & Henigar of Seattle by $297,311 for a total of $410,779.
The purpose is to determine the existing water quality in the Carson River, determine what impact the seepage from the wastewater reservoir is having on water quality, what improvements would come if they stop the seepage from reaching the river and estimate any benefits from lining the reservoir.
Over the years, seepage from the reservoir has grown to about 2,000 acre feet a year. Werner said the ground is acting as a filter with the result that nitrates in the water coming out of the springs below the reservoir are reduced by 90 percent from the amount in the reservoir.
Because of that and other factors, the city doesn't believe it necessary to line the reservoir, which would be very costly. City officials propose controlling discharge from those springs to eliminate direct flow into the Carson River and monitoring the water quality of the river to determine whether it will be necessary to partly or completely line the reservoir in the future.
"Unfortunately, the background of the Carson River is such that it can't take any more (pollutants) at all," he said. "From the state's definition, that is an illegal discharge of effluent to the Carson River and it's not permitted."
He said, however, performing the monitoring and studying the impact of those springs on the river will help keep the city out of legal trouble with the state while it figures out how to permanently handle the problem.
- Contact reporter Geoff Dornan at email@example.com or 687-8750.