East Bay Municipal Utility District (EBMUD) converted its entire distribution system disinfectant from free chlorine to chloramine early in 1998. The loss of disinfectant residual due to a rapid decomposition of chloramine in the Upper San Leandro (USL) Water Treatment Plant (WTP) service area led to nitrification in that portion of the system. Laboratory tests conducted on water collected from various locations in the USL WTP treatment train indicated that the rate of chloramine decomposition is not relatively constant for a given pH, temperature and TOC, as originally expected, but depends on plant operation. To date, major operational factors identified as impacting chloramine decomposition rate have been the use of strong oxidants before and after filtration, and operation of the filters. Bench-scale chloramine holding tests were conducted from January through August, 1999 to investigate: the effects of oxidation by free chlorine, ozone, hydrogen peroxide, and chlorine dioxide on chloramine decomposition rate in filtered USL water; the effects of TOC removal by activated carbon adsorption, ultrafiltration and nanofiltration on chloramine decomposition rate in settled, ozonated and filtered USL waters; the effects of biofiltration at USL and Sobrante WTPs on chloramine decomposition rate; and, formation of associated total trihalomethanes and haloacetic acids. Includes 8 references, table, figures.