Water Facilities

07 - Plant grounds

Water Supply Intake

The water supply intake is located just north of the water treatment plant on the shore of Lake Berryessa. The intake consists of two screened submersible pumps placed at different depths to give Operators withdrawal flexibility based on water quality analyses.

Water Treatment Plant

The District's original water treatment plant was replaced in 2014. The new plant uses a high rate contact clarification / dual media filtration treatment process and clearwell tank. From the clearwell, water is pumped into the distribution system/500,000 gallon tank for potable uses.

08 - filter unitsNBRID - Filtration Unit

The treatment process is monitoring 24 hours a day by SCADA (supervisory control and data acquisition) software that collects process data for regulatory reports. The system also includes alarm capabilities that will automatically shut the plant down if water quality does not meet regulatory standards. Is an alarm condition is met, operations is alerted and and dispatched to the plant to resolved the alarm.


Recently, two pre-settling tanks were installed to assist with the removal of THM (Total Trihalomethane) precursors prior to entering the treatment plant. The settling tanks will also assist with the removal of ash and other fire debris that is likely to flush into the lake with winter rains. Past fires in the Lake Berryessa watershed have led to algal blooms and aquatic plant growth that has impacted our plant and required extensive operator overtime for process control adjustments to meet regulatory requirements.

09 - settling tanks and plant

Water Distribution System

The distribution system includes ~ 33,000 ft of asbestos-cement and steel water mains sized between 4 and 12 inches. The distribution system is divided into seven different pressure zones managed by 6 pressure reducing stations located throughout the District, and water is provided through gravity by a single 500,000 gallon welded steel water tank.

12 - 500k tankNBRID - Pressure Tank StreetNBRID - Pressure Tank Rebuild

Reporting a Water Leak

Before reporting a problem, please note the following:

  • Where is the leak located – curb, corner, street, meter, other?
  • Is water pooling, trickling, or flowing down the street?
  • Is there construction activity nearby?
  • How long have you noticed the problem?

Then call the District main office at (707) 259-8600, or the District’s operations team at (916) 584-1893.

Permit Information

Our permit to operate is issued by the Mendocino District of the California Division of Drinking Water

Current Operating Permit (PDF).

The Water Watch website provides regulatory information about our system, including results of water quality testing.