* Editor’s note: This is the fifth in a series of “Ask the expert” columns appearing in advance of the Measure I election, regarding various technical aspects of the city’s water utility and the proposed Woodland-Davis surface water project.
The expert: Walt Sadler, a registered professional civil engineer in California with a bachelor’s degree in civil engineering from Sacramento State and a master’s degree in environmental engineering from UC Davis. Sadler also is a licensed water treatment operator with surface and groundwater experience and has more than 40 years of experience both as a consultant and staffer for municipal agencies.
The question: If the city elected to continue to supply its residents with only well water, what would it have to do to ensure that the supply meets all regulatory standards — including those effluent standards coming up in 2017? Or in other words, what upgrades would it have to make to the system? Can you estimate how long those upgrades would last and how much they would cost Davis to make?
The answer: The city of Davis, with its existing groundwater supply, currently meets all state and federal drinking water standards and, with minor changes in operation, can address the 2017 waste discharge requirements without the need for surface water or additional groundwater wells to meet current supply requirements.
The immediate need for the surface project, as explained to the Water Advisory Committee, was selenium, salinity and Woodland’s schedule.
Hydraulic modeling of the city’s existing water supply and distribution system has demonstrated that with changes in operation, selenium concentrations identified in the discharge requirements can be met, and total dissolved solids and hardness levels will decrease.
Implementing the city’s plan to irrigate parks and greenbelts with intermediate wells will only improve water quality.
This determination is not hypothetical, it can be found in Brown and Caldwell’s April 5, 2012, technical memorandum, “Water Distribution System Water Quality Modeling,” which was prepared at the city’s request.
With regard to the city of Woodland, they apparently have made no effort to limit their selenium discharge by changes in operation, as evidenced by their use of a well that has a concentration of approximately six times their discharge requirement limit. Salinity is a regional issue.
To address this issue there are a variety of activities occurring in the professional and regulatory community, the most significant being the Central Valley Salts Initiative, in which neither the cities of Davis or Woodland participate.
Eliminating water softeners has been identified as a method to address salinity. The city could use the existing hydraulic model to identify those individuals who do not need water softeners by virtue of the water quality of the well water they receive.
UC Davis professor Graham Fogg’s recent article substantiates the fact that the current well system is not in danger of immediate failure. Therefore, statements suggesting immediate well failure are intentionally false and fail to recognize that well construction technology has improved.
Wells, like surface water treatment plants, need maintenance and/or replacement over time, much like a car. To meet regulatory requirements, the city does not have to make any physical changes to its groundwater wells, merely modify its operational procedures.