Mr. Leighton is a hydrogeologist with more than thirty years of experience, including sixteen years with the U. S. Geological Survey that included time as the USGS California District coordinator. He collects and manages hydrologic data, analyzes groundwater systems, and develops and implements numerical models. He specializes in the development and application of Geographic Information Systems (GIS) in hydrologic investigations and groundwater modeling. He helped develop and maintains the groundwater flow model used to facilitate groundwater management in parts of San Mateo and San Francisco counties. His experience includes analysis of groundwater and water quality conditions related to subsidence mitigation strategies in the Sacramento-San Joaquin Delta and agricultural reuse of treated wastewater.