With the start of the borough’s new business year beginning Sunday, residents Monday found summaries for local water quality during 2017 in their postal boxes.
Conducted last year by the Alaska Department of Environmental Conservation’s Drinking Water Protection Program, sampling measured treated water for various inorganic and radioactive contaminants, as well as gauging residual disinfectants and disinfection by-products still present. Across the board, Wrangell’s water fell within regulatory thresholds for safety.
The results showed an improvement in water quality over the previous year. During the second quarter of 2016, a slightly higher than acceptable reading of haloacetic acids (HAA5) had been detected, at 61 parts per billion, above the 60 ppb limit. In 2015 the measurement had been even higher, at 67.9 ppb. Last year’s readings came in at an average of 47.3 ppb, with a low of 36 and high of 55 taken.
HAA5 is considered a byproduct of chlorination during the water treatment process, and along with other disinfection byproducts trihalomethanes (TTHM) and bromate, are considered a health risk. Long-term ingestion of higher concentrations of these can increase cancer risk for some people. As in previous years, Wrangell’s measurements for TTHM and bromates were well within acceptable thresholds.
The new water report indicated process improvements in the department as well. During the second quarter in 2016 Wrangell’s water department had failed to collect two of its quarterly water samples, specifically for HAA5 and for bromate, a common compound found in municipally treated water. The department has since regained compliance with collecting its samples.
Wrangell’s water comes from a pair of reservoirs on Mount Wrangell, with the more elevated of the two feeding into the lower, from which the city’s treatment plant draws its supply. Water is treated in a series of processes, which includes coagulation and flocculation to remove impurities, and “slow sand” filtration through a sedimented medium.
Because the water comes from an open, unprotected source, chemical disinfectants are added before storage to kill bacteria and other microbial contaminants. ADEC also assesses municipalities’ source water for vulnerabilities, and has given Wrangell’s a rating of “very high” susceptibility. Its water system has been rated a high susceptibility for bacteria and viruses, very high for nitrates and nitrites, high for volatile organic chemicals, high for heavy metals, and medium for other organics and synthetic organic chemicals. A high vulnerability does not
confirm the presence of any of these contaminants, but only gauges the potential for contamination.
Inorganic contaminants like copper and lead were also detected during sampling taken from consumer taps.
The presence of each typically comes from erosion of natural deposits or, more often, corrosion of household plumbing systems. Lead levels came in at 6.5 ppb, well below the federally-set safety threshold of 15 ppb. At elevated concentrations, lead can cause serious health
problems, in particular for young children and pregnant women. Those concerned about lead levels in their own fixtures can seek out further information and testing materials at http://www.epa.gov/safewater/lead.
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