||Several large field scale research projects were initiated by the U.S. EPA Drinking Water Research Division, MERL, Cincinnati, OH to evaluate the performance of GAC under varying operating conditions and different source water. Most of this research has been completed at nine locations (Cincinnati, OH; Manchester, NH; Jefferson Parish, LA; Evansville, IN; Miami, FL; Huntington, WV; Beaver Falls, PA; Passaic, NJ; and Thornton, CO). Various carbons produced for organics removal were evaluated at the nine locations. Over 150 specific organics were detected at these locations. In addition to these specific organics, surrogate parameters such as total organic carbon and total organic halide were used in many cases to determine GAC performance. Most of these compounds were removed by GAC. Also, microbiological data was evaluated. Actual cost data associated with the construction and operation of full scale research facilities were summarized. In addition, cost estimates for various GAC treatment scenarios were developed to examine the effect of economies of scale and cost tradeoffs between alternative GAC treatment systems.