Reaching local postal boxes last week, the quality report for Wrangell’s water supply indicates a slight decline.
The study was conducted last year by the Alaska Department of Environmental Conservation Drinking Water Protection Program, and provides a snapshot of water quality for 2015. Of the 80 contaminants being measured for by the the assessment, Wrangell’s water showed 11 but passed muster for 10 of them. One area, the level of haloacetic acids (HAA5), measured beyond the maximum contaminant level allowed by federal guidelines.
HAA5 is considered a byproduct of chlorination during the water treatment process, and along with disinfection byproducts trihalomethanes (TTHM) and bromate are considered a health risk. Research funded by the Environmental Protection Agency has concluded that long-term ingestion of higher concentrations of these can increase cancer risk for some people.
Wrangell’s measure for HAA5 came at 67.9 parts per billion, above the upper threshold of 60. This was only a slight increase over measurements taken in 2014, at 57 ppb. TTHMs and bromate were both well within safe limits, though showing a slight rise over the previous year.
The town’s water originates from a pair of surface reservoirs on Mount Wrangell. These are connected by a spillway, with raw water moving from the lower reservoir to the treatment plant. Based on their situation, ADEC has rated the sources’ protection area “very highly” susceptible to contamination. This includes bacteria and viruses, nitrates and nitrites, volatile organic chemicals and heavy metals. Organic chemical contamination was considered to be a “medium” level risk.
Water entering the town’s
plant is treated with ozone to remove iron, reduce the level of organics and provide some initial disinfection. Afterward, it is run through a pair of roughing filters, then four sand filters. Chlorine is then added before being stored in the plant’s two 424,000-gallon tanks.
Other inorganic contaminants were identified in the water, but were deemed to be below the allowable levels. Most substances were found to have remained the same proportionally as had been found in 2014 – these include barium, chromium, alpha emitters, lead, nickel and copper. Nitrates had increased slightly, from 0.169 parts per million to 0.172, with a threshold of 10.
An electronic copy of the report is available on the City and Borough of Wrangell’s website, http://www.wrangell.com, under the Public Works section. Paper copies can also be obtained from City Hall. For more information on the report, contact the Wrangell Public Works Department at 874-3904.
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