Project-Specific Hydrogeologic Evaluations

PES has provided technical assistance to a Central California Health Department to evaluate hydrogeologic and water quality aspects of development projects under County review and for use in completing initial studies for CEQA purposes. As part of our services, PES has assessed water-supply and water quality issues for numerous proposed development projects throughout the County, including: (1) the availability of long-term groundwater supply; (2) potential effects on the local and basin-wide water balance; (3) potential effects on nearby wells due to increases or changes in groundwater production; (4) potential effects on groundwater quality from increased septic system recharge; and (5) potential cumulative effects on the underlying aquifer in terms of groundwater quantity and quality. As part of these projects, PES has coordinated closely with numerous public and private stakeholders.

In performing the groundwater supply evaluations, PES has routinely applied the following hydrogeologic techniques:

  • Detailed analyses of geologic and hydrogeologic conditions, including: (1) evaluating the source capacity of water-supply wells; (2) evaluating lithologic and geophysical well log data; (3) evaluating and analyzing aquifer test and pump test data to estimate hydraulic properties of local aquifers; and (4) reviewing local and regional groundwater level trends;
  • Calculating local and regional water balances, which incorporated estimates of groundwater recharge, evapotranspiration, surface water runoff and streamflows, soil moisture demands, and groundwater demand;
  • Assessing the potential effects to the local nitrate balance using mass balance calculations;
  • Developing analytical groundwater flow models based on project-specific hydrogeologic data to analyze potential hydraulic interferences to neighboring water-wells; and
  • Developed potential mitigation measures that could be implemented to minimize effects of additional demands placed on groundwater resources resulting from the proposed development, including recommendations for water conservation measures, enhanced groundwater recharge programs, properly siting water-supply wells, and properly siting septic systems.