Water Treatment

Water rights were granted in March 2011 and are subject to conditions imposed by the state. Water diversions are limited during summer and other dry periods. A more senior water right for 10,000 acre feet was purchased from the Conaway Preservation Group to provide summer water supply. 45,000 acre-feet of water are diverted per year from the Sacramento River for treatment and distribution. Groundwater continues to be used in Davis during periods when demand for water cannot be met with surface water supplies alone. The City of Woodland uses Aquifer Storage Recovery (ASR) wells to meet peak demand.

The water treatment facility can supply up to 30 million gallons of water per day, with an option for future expansion to 34 million gallons per day. Of the 30 million gallons per day, Woodland's share of treated surface water is 18 million gallons per day, Davis' share is 10.2 million gallons per day, and UC Davis’ share is 1.8 million gallons per day. Approximately 4.5 miles of pipeline transports "raw" water from the surface water intake on the Sacramento River to the water treatment plant located south of Woodland. From there, the treated water travels 7.8 miles via pipeline to Davis, and approximately 1.4 miles to Woodland.

FAQs

How is surface water treated?

The surface water is treated with proven treatment technologies, including flash mixing, sand ballasted clarification, ozonation, granular media filtration and chlorine addition for disinfection. It is designed to meet or exceed current and potential future drinking water regulations. See diagram below.

What testing is done for contaminants?

Drinking water quality standards in California are established by the Federal government under the Environmental Protection Agency (USEPA) and the State Water Resources Control Board (SWRCB). To ensure the safety of drinking water, WDCWA and Cities are required by the SWRCB, Division of Drinking Water (DDW) to take samples regularly and test them for a multitude of compounds to ensure they meet drinking water quality standards. Samples are taken both at the connection points between the WDCWA pipelines and the Cities distribution systems within the Cities at locations agreed to by SWRCB DDW. WDCWA requires that the Regional Water Treatment Facility produce high quality water that will exceed current drinking water standards.

Each City publishes a yearly water quality report that details the results of water quality testing for the calendar year (January-December). Included in the report are helpful details about where the water comes from, what it contains, and how it compares to the State’s water quality standards. Below is a link to Woodland, Davis, and UC Davis’ Annual Water Quality Reports.

Woodland: https://www.cityofwoodland.org/529/Drinking-Water

Davis: https://www.cityofdavis.org/waterquality

UC Davis: https://facilities.ucdavis.edu/utilities/reports/water-quality

Does the treated water contain fluoride?

No, fluoride is not added to water supplies.

Are there chloramines in my drinking water?

No. Currently, finished water from the new treatment plant is designed to add chlorine, not chloramines, based on the needs of each City. Chlorine will be added to meet the minimum chlorine residual required by the Division of Drinking Water (DDW) to ensure that the distribution system is clear of harmful bacteria. Finished water chemicals (sodium hypochlorite, sodium hydroxide, orthophosphate corrosion inhibitor and phosphoric acid) can be added at the Regional Water Treatment Facility to the pipelines delivering treated surface water to Woodland and Davis. Each City has the ability to select individual values for finished water pH, chlorine residual, orthophosphate corrosion inhibitor, and phosphorous residual to be served to its distribution system.

What is Zinc Orthohosphate?

Zinc Orthophosphate (ZO) is used as a corrosion inhibitor against the release of iron, copper, and lead into our drinking water distribution system. ZO has successfully been used as a dissolved metals inhibitor in municipal water systems for more than 50 years. The US Environmental Protection Agency (USEPA) identified ZO as one of the best available technologies to minimize leaching of metals into drinking water. The Regional Water Treatment Facility uses ZO to prevent corrosion.

ZO works by creating/coating a film or scale barrier on the inside of the distribution pipe and trapping the underlying metals below. The control of this microscopic scale in an existing water system is one of the primary factors in maintaining water quality that is low or free from excessive dissolved metals.

ZO’s use is well known, reliable, and safe. It has been recommended for use in drinking water by American National Standards Institute/National Sanitation Foundation (ANSI/NSF) Standard #60 Drinking Water Treatment Chemicals, and has been widely approved for use in potable water systems by the State Water Resource Control Board (SWRCB), Division of Drinking Water (DDW). Proper use of ZO easily adapts to existing and changing water conditions without changing water chemistry or taste.

How do I report problems?

If for any reason you believe your water quality is in question, please contact your City immediately as follows:

City of Davis water users: Call Public Works Utilities and Operations at (530) 757-5686 (7 a.m. - 3:30 p.m.). The City requests water users call to report water quality problems so they can be quickly addressed. Please do not email to report water quality concerns. For water quality issues after hours, customers are asked to call Davis Police Dispatch at 530-747-5400 and press 0 to speak with the dispatch operator.

City of Woodland water users: Please call 530-661-5962 (7 a.m. – 4 p.m., Monday-Friday). After hours, the call will roll over to Yolo County Communications, which is available 24 hours per day, 7 days per week. Water users may also email Public Works, or submit a report through the “myWoodland” mobile app.

Do I need a water filter and/or water softener?

Most people will not need to use a water filter as the surface water delivered goes through a treatment process. However, a water filter can provide additional protections for people with severely compromised immune systems. Surface water is naturally much softer than groundwater, so a water softener in most cases is not necessary. Additionally, removing water softeners improves the quality of treated wastewater discharges to the environment. Water softeners add salts to wastewater discharge and ultimately impact the cities’ ability to meet state and federal wastewater quality discharge requirements. If you choose to continue to use a water softener, please contact your service provider to ensure it is programmed properly for reduced water hardness.

How much is an acre-foot of water?

An acre-foot of water – a common unit of measure for water – is about 325,000 gallons. That’s enough to cover an acre of land, around the size of a football field, one foot deep in water.

Conserving Water and Using Resources Wisely

Water conservation is, and always will be, essential to ensuring that water supplies are reliable.

Water conservation can help extend the lifespan of our water supplies and reduce the impact to our environment. See the tips below to save water around the house and yard.

Monitor your water use

Both the City of Woodland and the City of Davis offer an online water-use portal to their customers called AquaHawk. AquaHawk allows water customers to view their hourly water usage and set and then receive usage alerts.

Learn more and register at:

City of Davis Water Use Portal

City of Woodland Water Use Portal

AROUND THE YARD:

Adjust sprinkler heads and fix leaks (save up to 6,300 gallons of water per month)
Choose water-wise plants and trees (save 30-60 gallons per 1,000 sq. ft.)
Water in the early morning or late evening (save up to 50% of sprinkler water that would be lost to wind and evaporation)
Use mulch (save up to 30 gallons each time you water)
Set lawnmower blades to 3” (save 16-50 gallons per day – encourages deep roots)

AROUND THE HOUSE:

Fix toilet leaks (can save up to 200 gallons per day)
Fix leaks inside and outside the home (save 27 to 90 gallons of water each day)
Take 5-minute showers (save up to 12.5 gallons per shower)
Run the clothes washer and dishwasher only when full (clothes washer: save 15-45 gallons per load; dishwasher: save 5-15 gallons per load)
Recycle indoor water and use it to irrigate your garden (can cut water use by up to 30%)

Water Conservation Resources: