Hydrogeologic Studies

Scotts Valley Water District
Santa Cruz County, California

The photograph above shows the highly permeable sandstone deposits that crop out above a proposed recharge basin site in Scotts Valley.

The City of Scotts Valley and surrounding areas rely solely on groundwater from the Santa Margarita Groundwater Basin for their water supply. Scotts Valley Water District (District) is responsible for provision and management of water and has been active in developing strategies to optimize water resources.

Since 1984, the District has relied on Todd Engineers to provide hydrogeologic support for a full range of groundwater management activities. We have developed and implemented the District's groundwater management program to optimize and protect the Santa Margarita sole-source aquifer.

Hydrogeologic Characterization

The groundwater basin is situated in the Santa Cruz Mountains where depositional and tectonic history have produced a complex, folded and faulted bedrock aquifer system. Todd Engineers has characterized the groundwater basin through hydrogeologic data collection and analysis programs. We have produced an extensive catalog of surface and subsurface maps and cross sections of the basin.

We are currently directing a data collection field program to collect additional hydrogeologic data. Todd Engineers spearheaded the effort to win a $250,000 AB 303 grant, which is funding this study. The study includes the installation of water level and water quality monitoring wells, geologic and geophysical logging, and micro-paleontological analysis and interpretation.

Development and Exploration

Todd Engineers directs the groundwater exploration program, which has led to installation of several production wells, redistribution of pumping, and enhanced understanding of the complex hydrogeologic setting. The groundwater development program has involved planning and supervision of test drilling, including completion of test wells as deep as 1,100 feet. Various pumping tests have been conducted to determine aquifer characteristics and expected well production capacities, including aquifer tests using a packer to isolate specific aquifers. The program has resulted in the successful siting, design, construction, and testing of municipal wells.

Groundwater Management

The District manages water resources through its ongoing AB 3030 Groundwater Management Plan, prepared by Todd Engineers. The report describes water supply and water quality conditions. Recent groundwater storage declines around major wells are being addressed with a variety of management activities, including groundwater exploration, water conservation planning, potential artificial recharge, and water recycling.

Groundwater Modeling

Todd Engineers is responsible for construction, calibration, and validation of a basin-wide three-dimensional MODFLOW groundwater model. This model is used as a tool to evaluate the impacts of numerous water management scenarios, including the impacts of drought, redistribution of groundwater pumpage, wastewater recycling, and artificial recharge.

The computer model continues to be applied to management issues and is being updated regularly to incorporate new data on aquifer geometry, hydraulic conductivity, storativity, and water levels.