The Santa Cruz Water Department and the Soquel Creek Water District have formed the scwd² Task Force to evaluate reverse osmosis seawater desalination. Both agencies, which are located in Santa Cruz County, California, have identified seawater desalination as the most reliable, flexible and overall best option for addressing shortfalls from existing water sources. If seawater desalination is implemented, a full-scale plant would be designed to produce up to 2.5 million gallons per day of permeate. This paper briefly describes the scwd² seawater reverse osmosis (SWRO) desalination pilot-scale study, and presents summary results from eight months of testing that compares alternative pretreatment systems before the RO desalination membranes. Includes figures.