The recently proposed Stage 1 Disinfectant/Disinfection Byproducts(D/DBP) Rule will lower the total trihalomethane (TTHM) level to 80 ug/L and impose a maximum contaminant level (MCL) on the sum of five haloacetic acids (HAA5). The groundwater source for the Long Beach Water Department (LBWD) of Long Beach, California, contains a high level of organic precursors, resulting in elevated levels of disinfection byproducts (DBPs) if these materials are not removed prior to chlorination. Although LBWD has been treating this groundwater through conventional filtration since 1950, the primary objective of this treatment was for color and not organics removal. Depending on the blend of the wells used, the distribution system TTHM concentrations have been measured at over 100 ug/L. This paper details the method that LBWD used for determining the appropriate treatment necessary in order to achieve compliance with future DBP regulations. Enhanced coagulation was selected as the preferred treatment, and the new groundwater treatment plant was completed and has been successfully operated since 1997, producing water containing TTHMs of less than 40 ug/L. Includes 7 references, tables, figures.