Selawik Safewater Facility

What it means: This entry tracks violations of the Maximum Residual Disinfectant Level (MRDL) for chlorine — meaning too much disinfectant residual in the distribution system, not too little. Chlorine is added to water to kill pathogens, but excess residual can react with organic matter to form disinfection byproducts.

Health effects: Acute high-dose exposure to chlorinated water can cause eye and nose irritation, stomach discomfort, and nausea. Chronic exposure above the MRDL is primarily a concern because elevated chlorine accelerates formation of trihalomethanes and haloacetic acids, which are associated with increased cancer risk over time.

Limit: MRDL: 4.0 mg/L as an annual average

What it means: The Interim Enhanced Surface Water Treatment Rule (IESWTR), finalized in 1998, strengthened protections for systems serving 10,000 or more people by tightening turbidity limits and requiring Cryptosporidium removal. It was an intermediate step between the original SWTR and the Long-Term Enhanced SWTRs.

Health effects: Violations indicate failure to meet treatment technique requirements that reduce exposure to Cryptosporidium, Giardia, and other microbial pathogens. Cryptosporidium poses the greatest risk to immunocompromised individuals, infants, and the elderly, and can cause severe or fatal illness in vulnerable populations.

Limit: Treatment technique — no numeric MCL; compliance means meeting turbidity limits (0.3 NTU in 95% of monthly samples) and Cryptosporidium removal benchmarks

What it means: The 1991 LCR uses action levels rather than MCLs: if the 90th percentile of high-risk tap samples exceeds 15 ppb lead or 1.3 mg/L copper, the system must take escalating corrective actions. Violations typically indicate failure to maintain adequate corrosion control — the treatment that keeps lead from leaching out of pipes, solder, and fixtures.

Health effects: Lead: no safe level for children. Causes irreversible neurological damage, impaired cognitive development, behavioral problems, and reduced IQ in children under 6. In adults: hypertension, cardiovascular disease, kidney damage. Copper: acute gastrointestinal distress at high levels; liver/kidney damage at very high chronic levels.

Limit: Action levels: lead 15 ppb, copper 1.3 mg/L — 90th percentile of tap samples at high-risk sites

What it means: When a system violates a drinking water standard, it must notify customers promptly: within 24 hours for acute violations (e.g., E. coli), 30 days for non-acute MCL violations, and 1 year for monitoring failures. A violation means the notification was late or missing — not that the underlying water issue is necessarily severe.

Health effects: No direct health risk from the notification violation itself, but delayed notification means customers may have consumed contaminated water without the chance to take protective action (boil water orders, bottled water use).

Limit: No MCL — compliance requires meeting specific notification deadlines

What it means: The 2013 RTCR (effective 2016) replaced the original TCR. It triggers automatic E. coli testing whenever total coliform is found. A single E. coli-positive sample is an acute MCL violation. It also requires systems exceeding 5% total coliform-positive samples to conduct a formal assessment and correct any deficiencies, helping prevent contamination before it escalates.

Health effects: Total coliform bacteria indicate that the disinfection barrier has been breached or fecal contamination is entering the system. E. coli specifically indicates fecal contamination and the possible presence of disease-causing pathogens (norovirus, Salmonella, Shigella, Campylobacter). Illness can be severe in elderly, young children, and immunocompromised individuals.

Limit: Zero E. coli; ≤5% of monthly samples total coliform-positive

What it means: All systems using surface water (rivers, lakes, reservoirs) or groundwater under surface influence (GWUDI) must filter and disinfect. Treatment technique violations mean the system failed to maintain adequate disinfectant residual, exceeded turbidity limits, or lacked required permits. Snowmelt and storm events can raise turbidity and pathogen loads in surface water.

Health effects: Without proper filtration/disinfection: Giardia lamblia (severe diarrhea, cramping), Cryptosporidium (life-threatening for immunocompromised individuals), viruses (hepatitis A, norovirus). Turbidity itself is not a health risk but can shield pathogens from disinfection.

Limit: Treatment technique: turbidity ≤0.3 NTU in 95% of monthly samples; detectable disinfectant residual in 95% of distribution samples

What it means: TTHMs are four compounds — chloroform, bromodichloromethane, dibromochloromethane, bromoform — formed when chlorine reacts with organic matter in water. They are among the most common disinfection byproducts and form more readily in surface water systems with high organic loads.

Health effects: Long-term exposure is associated with increased bladder cancer risk. Some studies link high TTHM exposure to adverse reproductive outcomes. Bromodichloromethane is classified as a possible human carcinogen.

Limit: 0.080 mg/L (80 ppb) locational running annual average (LRAA)

What it means: HAA5 are five haloacetic acids formed when chlorine disinfectants react with naturally occurring organic matter in source water. Higher levels occur with more organic-rich source water or when water sits longer in distribution pipes. The violation indicates the locational running annual average exceeded the MCL.

Health effects: Dichloroacetic acid is a probable human carcinogen (Group B2). Long-term exposure to trichloroacetic acid may also increase cancer risk. Animal studies show liver, kidney, and reproductive effects at high doses.

Limit: 0.060 mg/L (60 ppb) locational running annual average (LRAA)