Santa Barbara Indirect Potable Reuse Evaluations

Working with two engineering firms, GSI helped the City of Santa Barbara evaluate the feasibility of indirect potable reuse of recycled water through groundwater recharge and recovery as a means of increasing groundwater supply capacity and reliability for the City. The City’s goal was to determine whether indirect potable reuse could replace its desalination supply and eliminate the use of an ocean intake. GSI provided technical evaluations of the recharge alternatives by working with the U.S. Geological Survey to complete groundwater modeling of surface infiltration of tertiary and advanced treated wastewater, injection of advanced treated wastewater, and recovery of the water. Our evaluation of the modeling results indicated that indirect potable reuse via surface recharge was not feasible at the target rates and that injection wells, coupled with dedicated recovery wells, are capable of storing the required volume of water with acceptable retention times to the nearest wells.

GSI's work involved:

• Conducting a fatal flaw and feasibility evaluation of subsurface intake methods that would be in compliance with California regulations for coastal desalination plans.
• Evaluating potable reuse opportunities associated with use of advanced-treated recycled water from the City’s wastewater treatment plant.
• Working with the U.S. Geological Survey and its numerical groundwater model of the basin to evaluate the amount of recycled water that could be recharged and the potential for negative impact under a number of climate conditions.
• Evaluating multiple scenarios, including simulations of injects wells along the coast as a seawater intrusion barrier.
• Determining that up to 8,500 acre feet per year could be stored in the basin annually with concomitant recovery pumping to create adequate storage space and meet the minimum retention time requirement.