2006 Water Comprehensive Plan - City of Bellevue

Table 10-2Annual Average of Total Trihalomethane SamplingYearMaximumContaminantLevel (MCL)(µg/L)AnnualAverage -SampleLocationBE-S15 (µg/L)AnnualAverage –SampleLocationBE-E9 (µg/L)AnnualAverage -SampleLocationBE-W7 (µg/L)AnnualAverage -SampleLocationBE-S13 (µg/L)1998 100 28 661999 100 65 512000 100 40 662001 100 32 432002 80 35 232003 80 30 44Phase II RuleRegulatory RequirementsAs part of the Phase II Rule regulating synthetic organic chemicals and inorganic chemicals,systems with a significant amount of asbestos-cement (AC) pipe must conduct periodic asbestosmonitoring in the distribution system. In Washington State, DOH has historically requiredsystems that contain more than 10% AC pipe to comply with the monitoring requirement. Thesesystems must collect one sample in the distribution system at a tap served by AC pipe and underconditions where asbestos contamination is most likely to occur.Bellevue StatusAs of 2005, approximately 53% of Bellevue’S distribution system was comprised of AC pipe.(Four- and six-inch diameter AC pipe is being replaced with ductile iron pipe at a rate ofbetween one and two miles per year.) Therefore Bellevue was required to monitor for asbestosduring the first three-year compliance period of each nine-year compliance cycle, beginning inthe compliance period starting January 1, 2001 and ending December 31, 2003. Bellevueconducted the required asbestos monitoring during January of 2002. The sample indicated thatthe asbestos level was below detection. The MCL for asbestos is 7 million fibers per liter. Thenext compliance period will begin in 2010.Surface Water Treatment RuleRegulatory RequirementsThe Surface Water Treatment Rule (SWTR) applies to systems using a surface water supply orgroundwater under the influence of a surface water body. In addition to the SWTR, the InterimEnhanced Surface Water Treatment Rule (IESWTR) regulates the treatment and disinfection of10-5