Well Design Engineering and Water Supply Planning Services, Sonoma County

EKI has been working with Valley of the Moon Water District (VOMWD) since 2014 and has successfully completed various water supply, conservation, infrastructure design and construction support projects.

Park Avenue Well Replacement, Chestnut Exploratory Borehole, and Aquifer Storage and Recovery: EKI is leading the implementation of the District’s Aquifer Storage and Recovery (ASR) project at two well sites. The project has been completed in several phases beginning with EKI assisting the District with obtaining an approximately $3 million grant for drought-relief funding through the State Water Resources Control Board. The drilling phase included preparation of design documents for the construction of a replacement supply well at one of the sites, the construction of three monitoring wells between 300 and 700 feet deep, and drilling of an 850-foot-deep exploratory borehole to site a future supply well.  The pilot study phase included preparation of a feasibility study to determine if ASR was appropriate at the two sites and whether any adverse geochemical conditions may occur during injection. Following the feasibility study and approval by the Regional Water Quality Control Board, a pilot study was performed at each site and included two rounds of injection, storage and extraction over several months. The pilot study indicated that ASR was appropriate at both well sites, with minimal geochemical reactions, and improved water quality at one site. EKI then prepared design documents for the construction of ASR infrastructure at both sites, utilizing much of the existing production well infrastructure at each site, including connections to a wellhead treatment system. The permanent ASR facilities included Baski flow control valves; a new well pump; new piping, valves, and instruments; and construction of a well pedestal and pad at one of the sites.

Well 5A Production Well Replacement: EKI prepared design documents, performed construction management, and led permitting for the Well 5A Production Well Project, which included construction of a new well cased to a depth of 692 feet, rehabilitation and refurbishing the existing iron and manganese treatment system, and piping and appurtenant work.

Water quality testing during construction of Well 5A, which replaced an existing well at the same site, showed that there were elevated levels of arsenic, iron, and manganese, as well as a periodic hydrogen sulfide odor in the groundwater. The well system already had a greensand filter to remove iron and manganese, so EKI developed a design for a new ferric chloride feed system that would allow the existing filters to co-precipitate and remove the arsenic and a residuals management system. To address the hydrogen sulfide odors, EKI developed a scope of work for a driller to perform zone testing and oversaw water quality testing of hydrogen sulfide during scope implementation. While the testing identified areas of higher hydrogen sulfide, the well was subsequently incorporated into the District’s ASR project.

Outcome

The ASR project has progressed through final design and construction, permanent ASR systems at both well sites have been completed and are operational. At full implementation, the project can provide approximately 80-acre-feet per year of additional groundwater supply while improving water quality and operational flexibility. These wells will give the District the ability to store drinking water in the ground for later extraction and use, especially in emergencies. It will also give the District and its partners, the ability to inject water into the lower aquifer in the Sonoma Valley, helping reverse years of decline.