The Sacramento Regional County Sanitation District (California) and Brown and Caldwell have developed a unique land treatment system for final disposition of the District’s lagooned biosolids. The system has been pilot tested for 5 years in a 0.4 hectare (1.0 acre) synthetic-lined land application facility. Long-term loading rates of 390 to 450 dry metric tonnes per hectare per year (175 to 200 dry tons per acre per year) have proven acceptable. Since this is far above agronomic loading rates, there are no crops grown at this site. The primary purpose of the system is cost-effective final treatment and disposition of digested, lagooned biosolids. Since there was no known experience with using a synthetic geomembrane liner and a leachate (infiltrate) collection system for a biosolids land application site, the District proceeded to build and operate the pilot facility and provide long-term operation and performance testing to define acceptable loading rates, confirm costs, and insure reliable performance of system components. This extensive testing work has been completed and the results are summarized here. The District is proceeding on a course to implement full-scale lined land treatment and disposal sites in 2002 and 2003.