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AUG-15-1995 17:01 FROM TO 91x'09478171-6-563541 P.05 Pools for Emergency Drin.ting Yater Page 4 r Table I describes the 50 pools sampled for minerals and trace metals, and indicates which ten pools were additionally tested for volatile and semi- volatile organics, Thirty pools used trichloroisocyanuric acid ("Triehlor") as a disinfectant; ten used gas chlorine; and ten used hypochlorite, or liquid 't chlorine, The pools using as chlorine tended p g 8 to be larger pools, maintained by educational institutions, The pools in general were well maintained, although ten pools had a free chlorine residual below 1 ppm on the sampling day. The pH ranged from 7.0 to 7.8 at all but four pools, for which the pH was 8,0. Most pools had been drained within the past five years. Table 2 lists the results of the mineral, trace metal, and trihalomethane analyses. The table lists the average concentration, the maximum concentration detected, and the interpolated 95th percentile concentration. In many cases, the results are below the method detection limit. The - trihalomethane concentrations were determined for only 10 pools. All of the other results are based on 50 samples. Also listed are drinking water standards for most of the analytes, taken either from California drinking water regulations or from Health Advisories for Drinking Water Contaminants, published by the US Environmental protection Agency (US EPA, 1993). For several analytes with no specific standard, the table lists the guideline for total dissolved solids (TDS). Slight exceedances of drinking water standards were found for Arsenic, chloride, fluoride, nitrate, and silver. A significant exceedance was found for antimony. Except for trihalomethanes, no volatile and semi-volatile organics were found above method quantitation limits in any of the ten pools sampled. In - one pool, methylene chloride was detected at a concentration of 2 ppb, below the method quantitation limit of 5 ppb. Appendix A lists the organic compounds analyzed for. Table 3 describes the 50 additional pools which were sampled for cyanurate concentration, each using trichlor as a disinfectant with or without - gas or liquid chlorine, The average cyanurate concentration was 63 ppm, with a maximum of approximately 160 ppm. The field colorimetric method used depends on a visual estimate of a test solution's murkiness, and is therefore only semi-quantitative. Figure 3 shows the correlation for cyanurate levels - for the 10 pools tested, comparing the primary lab (County) and the confirmatory lab (State). The correlation is 0.86. For one sample ("25), the measured cyanurate levels differed by 82 ppm; for all others the agreement _ was much less. From this data and from our experience, we estimate that the field cyanurate concentrations are probably accurate to within a factor of two or three. - We looked at a subset of the sampled pools likely to have better water quality than the others--pools using gas chlorine which had been drained and refilled within the past year. Of the ten gas-chlorine using pools in our sample, five had been drained within the past year, Table 4 lists these pools' results for those analvtes with exceedances of drinking water standards- - antimony, arsenic, fluoride, nitrate, and silver. The highest antimony level