Upton Junction Phase 11

What it means: Radium-226 and Radium-228 are naturally occurring radioactive isotopes produced by the decay of uranium and thorium in bedrock. They dissolve into groundwater, particularly in deep aquifers with low oxygen and low pH. Granite bedrock and some deep sandstone and limestone aquifers present conditions where combined radium can reach detectable levels in drinking water.

Health effects: Radium is a bone-seeking radionuclide that accumulates in skeletal tissue after ingestion. Long-term exposure increases the risk of bone cancer and leukemia. There is no safe threshold for ionizing radiation — the MCL is set at a level balancing risk reduction with treatment feasibility. Children are particularly vulnerable due to higher rates of bone growth and calcium uptake.

Limit: 5 pCi/L (combined Ra-226 and Ra-228)

What it means: Uranium is a naturally occurring radioactive heavy metal found in rock and soil formations across the United States. It leaches into groundwater through weathering of uranium-bearing minerals, and is more prevalent in granite-rich and other uranium-bearing geologies. Mining and milling operations can also elevate uranium in nearby water supplies.

Health effects: Uranium poses both radiological and chemical health risks. Chronic exposure is primarily associated with kidney damage due to its chemical toxicity as a heavy metal. The radiological risk — increased cancer probability — is also present but secondary to the nephrotoxic concern at drinking water concentrations. There is no safe threshold for radiation exposure.

Limit: 0.030 mg/L (30 µg/L)

What it means: Gross alpha particle activity is a screening measurement of all alpha-emitting radionuclides in water, excluding radon and uranium (which are regulated separately). If gross alpha exceeds 5 pCi/L, further analysis is required to identify specific radionuclides. Elevated gross alpha typically indicates water drawn from deep aquifers in contact with uranium- or thorium-bearing bedrock.

Health effects: Alpha-emitting radionuclides accumulate in bone and soft tissue, delivering sustained internal radiation doses that increase lifetime cancer risk. There is no established safe threshold for ionizing radiation. Individual contributors such as radium-226 and polonium-210 have their own MCLs; gross alpha serves as a cost-effective screening tool that triggers more specific radionuclide analysis when exceeded.

Limit: 15 pCi/L (excluding radon and uranium)

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: The 2021 LCRR updated the 1991 LCR with mandatory lead service line inventories and replacement planning, a new 'trigger level' at 10 ppb requiring optimization, and strengthened public education. The 2024 Lead and Copper Rule Improvements (LCRI) further requires replacing all lead service lines within 10 years.

Health effects: Same as Lead and Copper Rule (5000). Violations typically reflect failure to complete the required lead service line inventory or submit a required replacement plan. Lead service lines are the primary source of lead at the tap in many older systems.

Limit: Lead action level: 15 ppb (trigger level: 10 ppb); copper action level: 1.3 mg/L

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