2006 Water Comprehensive Plan - City of Bellevue

Am Test Laboratories14603 NE 87 th St.Redmond WA 98052425-885-1664Seattle Public Utilities – Water Quality Laboratory800 S. Stacey St.Seattle WA 98134206-684-3000STAGE 2 DISINFECTANTS/DISINFECTION BY-PRODUCTS RULEThe Stage 2 DBPR was promulgated on January 4, 2006, concurrently with the Long Term 2Enhanced Surface Water Treatment Rule (LT2ESWTR) and became effective in March 2006.Because this regulation was not effective between 1998 – 2004, it was not included in theevaluation of Bellevue’s regulatory compliance status described in the previous sections.However, there are regulatory milestones associated with the Stage 2 DBPR that will haveimmediate impacts on Bellevue.The Stage 2 DBP Rule has been developed by the EPA to further reduce exposure to DBPs thathave been linked to bladder, rectal, and colon cancers. This Rule applies to community waterand nontransient, noncommunity water systems that serve drinking water treated with a primaryor secondary disinfectant other than UV. The Stage 2 Rule does the following:• Changes the method of calculating DBP regulatory compliance to a locationalrunning annual average (LRAA) of quarterly samples, in which the systemcalculates a running annual average for each DBP monitoring location instead ofcalculating a running annual average for the entire system.• Reestablishes the location and number of DBP monitoring sites. The proposedrule requires systems to conduct an Initial Distribution System Evaluation (IDSE)to select Stage 2 DBP monitoring locations in the distribution system.Additionally, the final Stage 2 DBP Rule requires systems to determinemonitoring requirements based on population.• Establishes DBP operational evaluation levels. A system that exceeds this level isrequired to conduct an operational evaluation, evaluating their distribution systemoperations and determining ways to reduce DBP levels. The system is required tonotify the state of an operational evaluation level exceedance and submitevaluation results within 90 days of the exceedance.• Consecutive systems that purchase drinking water carrying a disinfectant arerequired to implement Stage 2 DBP requirements.Bellevue’s first step in complying with the Stage 2 DBP Rule will be conducting an IDSE. Thegoal of the IDSE is to identify areas that have routinely higher DBP concentrations than otherareas in the distribution system and use this information to select monitoring locations for longtermStage 2 DBP compliance monitoring. The IDSE requirement can be met in four ways:10-10