In the heart of Sonoma County, California, the city of Santa Rosa is home to approximately 177,500 people. The city is responsible for delivering 6 billion gallons of drinking water annually, and has long partnered with Woodard & Curran’s water resources experts for water supply planning, regulatory support, and recycled water services. In 2013, we developed the Santa Rosa Plain Salt & Nutrient Management Plan, which was updated with a Monitoring & Reporting Program in 2017 to define a groundwater monitoring framework. As a result, Woodard & Curran has supported several projects identified in these planning documents for the city.
Santa Rosa operates two main supply wells and several other unused or underutilized wells that only come online during service interruptions. The Leete Well, constructed in 1953, served as part of the city’s Emergency Groundwater Supply Program until November 2011. The 10-inch-diameter, steel-cased, production well with a depth of 310 feet below ground surface was taken offline due to sand intrusion stemming from a well casing separation. With limited options to site a new well — an expensive investment for a water utility — the city hired Woodard & Curran to conduct a condition assessment, repair, and rehabilitation to bring Leete Well into service again.
Woodard & Curran assembled an interdisciplinary team of hydrogeologists, engineers, and operators with institutional knowledge of the local groundwater basin to first conduct a thorough assessment of the well and well house. The team leveraged a variety of activities and technologies, including video surveys, dynamic flow and chemistry profiling, aquifer testing, water quality sampling, well casing and screen integrity analysis, and a geophysical survey. The data collected during the assessment were evaluated to determine feasibility of well screen repair and rehabilitation, as well as estimated capacity and sustainable yield.
The assessment findings served as the basis for the proposed rehabilitation of Leete Well, and Santa Rosa hired Woodard & Curran to complete the design based on our recommendations. The scope of work included removal of 29 feet of fill in the bottom of the well and mechanical and chemical methods to remove the accumulation of iron and manganese oxide secretions of biomass from the well casing, screen, and gravel pack to the extent possible. Another video survey documented the condition of the well after cleaning was completed and identified two separations in the well screen. Results from a pumping test indicated the initial rehabilitation significantly improved the well capacity by 69 percent, indicating the well can be pumped at a rate of 400 gallons per minute.
With such a substantial improvement in well capacity, the city authorized Woodard & Curran to repair the casing separations with two 5-foot-long liners and conduct a pumping test to document any reduction in well capacity. With no reduction in well capacity found, the city also asked Woodard & Curran to develop an operations and maintenance plan to prevent future biofouling and to conduct an alternatives analysis to bring Leete Well online as a regular production well, rather than an emergency supply well. The alternatives analysis and associated cost estimates will be used to identify the optimal pressure zone and distribution of this new water supply.
The outcome of the work to date has significantly benefited the city by transforming a dormant asset with unknown value into an additional production well. This new supply source will improve the resilience of the city’s water system and support planned growth.