The major source of drinking water for City of Fresno customers comes
from the Fresno Sole Source Aquifer, a large underground water system that supplies many communities in the San Joaquin Valley. To supply water, water production wells are drilled to extract water from the aquifer. Water is then distributed through pipelines to individual customer services. Approximately 260 water wells are scattered throughout Fresno to provide water to the community.
FRESNO SURFACE WATER TREATMENT FACILITY
While groundwater has traditionally been the sole source of water for Fresno, the Surface Water Treatment Facility (SWTF) now supplements our system with water delivered directly from the Sierra Nevada Mountains to the facility for treatment. The SWTF supplies thousands of homes in Northeast Fresno – more than 20 million gallons of water per day. During the peak demand summer season the facility supplies approximately 15% of Fresno's potable water. During the low demand winter periods the facility supplies more than 30% of the community's supply. A second surface water treatment facility is planned in southeast Fresno to meet demands anticipated by the redirection of growth suggested in the 2025 General Plan.
SOURCE OF SUPPLY AND CONVEYANCE
Implementation of the Metropolitan Water Resources Management Plan to develop the infrastructure for conjunctive use of all of the City's surface water supplies, along with enhanced groundwater recharge and onservation, would balance Fresno's groundwater budget for the first time in over 75 years. As a part of this proposal, expansion of the existing Northeast surface water treatment facility (SWTF) and creation of a second SWTF in southeast Fresno are planned in order to offset current demands and to meet future demands from anticipated growth. Construction of the Regional Transmission Distribution System will allow treated surface water to be delivered everywhere in the City in order to support current demands and future growth. This plan will enable us to conserve our groundwater as an alternate supply that can be relied on during periods of drought.
Precipitation and snow melt from the Kings and San Joaquin watersheds are provided by the City's federal Central Valley Project contract and Fresno Irrigation District entitlements. The snow melt from the Sierra Nevada Mountains, runs into the Kings and San Joaquin Rivers. Currently, water is supplied via the Enterprise Canal, a 25 mile circuitous, open channel that winds its way through ag and urban settings. The Enterprise Canal can deliver from either of the City’s water supply sources.
In the near future, a five mile pressure pipeline will be constructed directly from the Friant-Kern canal to the SWTF. The pipeline will provide raw water quality enhancements, additional public health protection and adequate hydraulic head to operate the treatment works without supplemental lift. After pipeline completion, the Enterprise Canal will become a secondary supply source.
ABOUT THE TREATMENT
The SWTF utilizes a three-step treatment process: clarification, filtration and disinfection. “ACTIFLO®” is a patented term for a unique clarification process, which involves treatment additives plus microsand being injected into the water and rapidly mixed together to form a “ballasted floc.” This process removes suspended material and bacteria that may be living within those particles. The process repeats itself in a series of basins as the growing floc settles at the bottom. The cleaner water travels upward through a honeycomb-like set of tubing and is finally sent on to the ozone contact basin. This entire process is commonly called coagulation, flocculation, and sedimentation. While it could take nature several years to achieve this clarity of water, this entire process takes about 15 minutes.
The ozone contact basin is where both ozone disinfection and oxidation occur. Water coming from the ACTIFLO® process is injected with thousands of tiny ozone bubbles. A powerful oxidant, ozone destroys many types of microorganisms; color, taste and odor compounds; and some man-made organic compounds. Once the ozone has effectively done its job (within about 10 minutes), it rapidly dissipates. By the time the water leaves this basin, it is ozone-free and travels on to the granular activated carbon filters for additional purification.
More than 128 physical, chemical and microbiological tests are performed every day for the SWTF to ensure that the entire treatment process has achieved its primary public health goal. All data collected in the laboratory is submitted each month to the California State Department of Health Services as part of a monthly regulatory report on the performance of the entire treatment process. An average of 48 water quality tests are taken each workday for groundwater.