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Woodland and Davis are two of only a very few cities in California that still rely entirely on groundwater for water supplies. In the past, groundwater was plentiful enough to meet community needs, and also state and federal water quality regulations. By itself, it is not expected that groundwater will be able to meet future state drinking water quality and wastewater discharge regulations. The quality of local groundwater supplies is deteriorating. Our groundwater has an increasing amount of salts and other minerals that threaten the environment and public health. The Cities cannot meet anticipated future regulations for the water coming into homes, or for water returned to the environment after leaving the wastewater treatment facilities, using groundwater only. An alternative, high-quality water source is needed to largely replace and supplement the groundwater supplies.
The many benefits include health and safety of drinking water supplies, reduced costs from avoidance of wear and tear on water using appliances, compliance with treated wastewater discharge requirements, and environmental benefits associated with improvements to discharged wastewater and with the replacement of an antiquated intake on the Sacramento River with an intake with state-of-the-art fish screens. Resulting improvements in the quality of treated wastewater will increase the opportunity for water reuse, advance environmental stewardship in the Yolo Bypass, and potentially lower wastewater treatment costs from what they otherwise would be in the future. Additionally, there will be opportunities to implement aquifer storage and recovery, which involves injecting high-quality, treated surface water into wells for later use. This will allow the cities to maximize the use of surface water supplies by storing the surface water in the ground during the winter months when more water is available, and delivering that water to customers during summer months and other dry times when surface water supplies are not as readily available.
It’s the quality of the water – not the quantity – that’s driving the shift from groundwater to surface water. It’s also getting more and more difficult to meet demands for water use and water quality regulations using existing infrastructure. A number of groundwater wells in Davis and Woodland have been shut down and destroyed because they no longer work and can’t be fixed, or because they exceed drinking water quality limits. Over the past several years numerous wells in Woodland and in Davis have had to be removed from service due to excessive nitrate levels. It is also likely that a number of wells in both cities will be unable to meet pending hexavalent chromium limits. Even with major improvements to groundwater facilities (wells and pumps, for example), we would still fall short of meeting future water quality regulations for drinking water and treated wastewater. In short, we need a higher-quality source of water.
An acre-foot of water – a common unit of measure for water – is about 325,000 gallons. That’s roughly the amount of water used by two households in a year, including landscape water use.
Water conservation can’t improve water quality, and it will not reduce the salt content or eliminate other water quality constituents of concern in either the water supply or wastewater systems. Again, it’s primarily the quality of the water – not the amount – that has created the need for the project. However, more aggressive water conservation can save money for both individual water customers and water utilities. Both Cities are well on their way to meeting the new State requirements for reducing per capita water demand by 20 percent by 2020.
The high, naturally-occurring salt content in the groundwater combined with additional salt from consumer uses (including water softeners) results in a high concentration of salts in the water. “Used” water that leaves our homes – also known as “wastewater” – has even higher concentrations of salt than the water that comes into our homes. For wastewater, the Central Valley Regional Water Quality Control Board (Regional Board) is aggressively pursuing requirements for reductions in salt discharges to protect the environment and other downstream water users.. Discharges of treated wastewater in the Central Valley will have to meet more stringent salinity standards in the future.
Desalination – reducing the salt content in water or wastewater – is very costly (in fact, far more expensive than the Project’s costs), both for construction and operation. Even with emerging new technologies, desalination requires high amounts of electrical energy and expensive systems, and poses serious and costly problems with disposal of brine from the treatment process. To provide the most value, desalination would be needed at each individual groundwater well. However, many of the wells are in residential locations where there is not enough room to construct treatment facilities, including the storage and disposal facilities to handle the brine that would be a product of treatment. The amount of high-saline brine that would require disposal would be 20 percent or more of the volume of water being treated. This brine would need to be transported to an area closer to the coast for ocean disposal. It is expected that it would be very difficult, if not impossible, to get permits to implement all aspects of desalination, including brine disposal.
WDCWA’s water right permit authorizes it to utilize up to 45,000 acre feet of water per year. However, diversions will be limited during summer months and other dry periods. During these times, WDCWA will utilize up to 10,000 acre feet of water under a senior water right purchased from the Conaway Preservation Group (see below). WDCWA is also exploring the possibility of implementing aquifer storage and recovery facilities, which involves the injection of high-quality, treated surface water into water wells for later extraction and delivery to water users. Injection into the wells would occur during the winter months when more surface water is available, and could be extracted and used in summer months and during other times when diversions are restricted.
WDCWA purchased a senior water right for 10,000 acre feet of surface water from the Conaway Preservation Group. This water is subject to fewer restrictions between April and October and will be used during times when water under the primary water right is not available. Existing groundwater sources will continue to be used along with higher-quality groundwater from the deep aquifer to help meet peak summer demands. Combined use of surface and groundwater sources, referred to as “conjunctive use,” and the blending of supplies will result in substantial year-round improvements in water quality, including the summer months.
Yes. Independent professional studies commissioned by the Davis City Council repeatedly confirmed this project as the best long term option for meeting drinking water and wastewater quality regulations, and ensuring that water is always available when needed. A panel of nationally-recognized drinking water experts was convened in 2008 by the National Water Research Institute and their results were provided in a written report. A similar independent evaluation was completed in early 2009 by retired UC Davis engineering professors Ed Schroeder and George Tchobanoglous (click here to read the report).
Planning for the project over the past 20 years has involved a number of expert professionals, including: Bartkiewicz, Kronick & Shanahan; Bartwell Wells; Borcalli & Associates; Brown & Caldwell; BSK Engineers, Geologists, Environmental Scientists; Environmental Science Associates; Kennedy/Jenks Consultants; LTD Engineering; Larry Walker Associates; Luhdorf & Scalmanini; Montgomery Watson Harza; West Yost Associates; Winzler & Kelly; and Wood-Rodgers.
Lastly, the project was studied by independent, citizen-led water utility advisory groups in both cities in 2012 (the Water Advisory Committee in Davis and the Water Rate Advisory Committee in Woodland). Both groups recommended that the respective City Councils support the project. In early 2013, the project was put before City of Davis voters for a vote, resulting in majority support for moving forward with the project.
Even without new homes and residents, the Cities would still be required to improve the quality of their water. The regional water supply project is designed to provide water that meets state and federal regulations, not to encourage growth and development. Existing residents in both Cities will always need safe drinking water, and the Cities will always be required to meet water quality and wastewater discharge regulations, regardless of growth.
In December 2010, UC Davis entered into an agreement with WDCWA for a potential water supply contract. Under the terms of the agreement, UC Davis has an option to purchase 1.8mgd of the project’s 30mgd capacity. The option is valid up until the surface water project starts operation. Should UC Davis decide to exercise its water purchase option, the agreement obligates it to pay “into” the Project for capital and fixed and variable operating costs. UC Davis, a long-time project partner, paid its fair share of Project costs through September 15, 2009, the date on which the Woodland-Davis Clean Water Agency was formed. Project costs incurred after that time will be assessed to UC Davis should they decide to rejoin the project. Payment for UC Davis’ share of capital and fixed operating costs for the water treatment plant would be assessed at a rate equal to UC Davis’ share of the treated water. Operating costs for their share of the transmission pipeline from the water treatment plant to Davis will also be assessed.
The size of the Project facilities does not change with or without UC Davis’ participation. If UC Davis exercises its water purchase option, the costs to Woodland and Davis would be decreased in proportion to UC Davis’ share of the treated water.
Fluoride is a naturally occurring element found in water supplies throughout California. Optimum levels of fluoride have been shown to improve oral health and decrease tooth decay. In California, state law requires that optimum levels of fluoride be added to any public water systems with 10,000 or more connections. Currently, neither Woodland or Davis add fluoride to their water supplies since they lack a central treatment location where fluoride can be added, monitored and adjusted as needed. The construction of the surface water supply project, with its state-of-the-art treatment facility, offers both cities the option to add fluoride to their respective water supplies. Fluoride would be added post water supply treatment and would be done independently for each city. For this reason, each City Council will have the opportunity to consider whether or not it should fluoridate its water, taking into account a variety of factors such as cost and ability to effectively regulate fluoride levels when using a blend of groundwater and surface water. Recently, the Yolo County Board of Supervisors cited community health benefits when it adopted a resolution encouraging both cities to add fluoride to their water supplies.
There is some controversy around the fluoridation of water supplies. Supporters emphasize the proven health benefits of fluoride supplementation, along with the reduced medical costs and cases of dental disease in communities with fluoridated water systems. Opponents cite concerns that consumers who drink fluoridated water may get too much of the substance since it is added to toothpastes and other personal care products. Ingesting too much fluoride can present health risks. For that reason, the state and federal governments have adopted maximum limits on how much fluoride – the total of naturally occurring and added – can be present in tap water delivered into homes. This maximum limit takes into account the fluoride that consumers are receiving from other sources.
The City Councils for both Woodland and Davis will provide an opportunity for public consideration and input into their decisions about whether or not to fluoridate their water supplies, and what factors will be considered in making those determinations. The Woodland-Davis Clean Water Agency will be responsible for implementing the decisions of the cities.
The DBO process, the least-costly means to implement the project, will result in a single contractor that will design and build the water treatment plant and pipelines, and then operate the facility for a fixed price for a specified number of years, currently set at 15. (The DBO contract will include a buyout provision for the Operations portion of the contract. This will allow the cities to maintain flexibility regarding how the facilities are operated in the future once successful startup and initial operation of the facilities has been demonstrated.) This method streamlines the process because the same team is involved in all aspects of the project implementation, reducing conflicts between the various stages (design, construction, operation).
A Request for Proposals for DBO contractors was developed and then later amended by the Agency’s Board (April 2013). The successful DBO contractor must demonstrate an ability to meet or beat the Agency’s maximum project cost (reduced 20 percent from original engineering estimates); outline a plan for the competitive pricing of approximately 70 percent of construction work, which is expected to include materials and the construction of the pipelines and water treatment facility; and provide for an “open book” review of costs for the roughly 30 percent of the work they will perform directly, such as project design.
The Design-Build-Operate contractor will be responsible for developing a traffic management plan to share with the community. This plan will outline any proposed traffic impacts to roads and streets in and around the project areas, along with detours and alternate routes, as needed. This plan will be developed in conjunction with pre-construction activities.
The Agency is requiring that approximately 70 percent of the construction be competitively priced. Local contractors will be notified of and encouraged to participate in the bidding process.
Reclamation District 2035 and the Woodland-Davis Clean Water Agency are ...
WDCWA Board Meeting, September 15, 2016 - Davis