6.2 SDWA Regulations & Compliance Reporting

6.2 SDWA Regulations & Compliance Reporting

The Safe Drinking Water Act (SDWA), passed in 1974 and amended in 1986 and 1996, is the federal law protecting drinking water supplies. The EPA sets legally enforceable standards to limit contaminants. Operators must comply with these regulations to protect public health and avoid severe legal and financial penalties.

Primary vs. Secondary Drinking Water Standards

The EPA divides drinking water standards into two categories: Primary and Secondary standards.

National Primary Drinking Water Regulations (NPDWR) are enforceable health-based standards. They establish a Maximum Contaminant Level (MCL), the highest level of a contaminant allowed, and a Maximum Contaminant Level Goal (MCLG), the level below which there is no expected health risk. MCLGs are non-enforceable. The EPA sets MCLs as close to MCLGs as technologically and financially feasible.

National Secondary Drinking Water Regulations (NSDWR) are non-enforceable guidelines regulating contaminants that cause aesthetic effects (such as taste, odor, or color) or cosmetic effects (such as skin or tooth discoloration) in drinking water. Although federal secondary standards are recommendations, individual states can choose to adopt and enforce them as state regulations.

The Lead and Copper Rule (LCR)

The Lead and Copper Rule (LCR), promulgated in 1991, protects public health by minimizing lead and copper levels in drinking water. Unlike most other contaminants, lead and copper typically do not originate in the source water or the treatment plant; instead, they enter drinking water through the corrosion of lead pipes, copper pipes with lead solder, and brass fixtures in household plumbing.

To monitor for lead and copper, systems must collect tap water samples from high-risk homes (specifically those with lead service lines or lead plumbing). These samples must be first-draw, one-liter tap water samples that have stood motionless in the plumbing system for at least six hours.

The LCR does not establish a traditional MCL. Instead, it establishes an action level (AL) based on the 90th percentile of all samples collected during the monitoring period:

• Lead Action Level: 0.015 mg/L (or 15 micrograms per liter, $\mu\text{g/L}$).
• Copper Action Level: 1.3 mg/L.

To calculate the 90th percentile, the operator sorts all sample results in ascending order. In a system that collects 10 samples, the 90th percentile is the 9th sample result. In a system collecting 100 samples, the 90th percentile is the 90th sample. If the 90th percentile value exceeds the action level for either lead or copper, it is not an immediate violation of the rule, but it triggers mandatory actions. The system must implement corrosion control treatment (such as adjusting pH or adding orthophosphate), conduct source water monitoring, and deliver public education to the community.

Public Notification Rule and Compliance Reporting

When a public water system violates a primary drinking water regulation, it must notify the public under the Public Notification Rule. Violations and situations are categorized into three tiers based on the severity and immediacy of the potential health risk.

Tier 1 Public Notice (Immediate Threat)

Tier 1 violations pose an immediate, acute threat to human health. Water systems must notify the public as soon as possible, but no later than 24 hours after learning of the violation. The notice must be broadcast on local television or radio, posted in public areas, or hand-delivered to consumers. Tier 1 situations include:

• A violation of the E. coli MCL, or a failure to test for E. coli after a total coliform-positive routine sample.
• An exceedance of the nitrate or nitrite MCL ($10\text{ mg/L}$ and $1\text{ mg/L}$, respectively), which poses an immediate risk of blue baby syndrome (methemoglobinemia) in infants.
• A chlorine dioxide maximum residual disinfectant limit (MRDL) exceedance.
• A single-sample turbidity exceedance exceeding $5.0\text{ NTU}$, if the primacy agency determines a Tier 1 notice is warranted.

Tier 2 Public Notice (Potential Serious Threat)

Tier 2 violations have the potential to cause serious adverse health effects, but do not pose an immediate health risk. The water system must notify the public as soon as practical, but no later than 30 days after the violation occurs. Tier 2 situations include:

• Exceedances of MCLs for inorganic, organic, or radiological contaminants (excluding nitrate/nitrite).
• Violations of treatment technique requirements (such as failing to meet turbidity removal ratios or failing to correct LCR exceedances).
• Failure to comply with variance or exemption conditions.

Tier 3 Public Notice (Administrative or Monitoring Violations)

Tier 3 violations do not pose a direct threat to public health. They typically involve a failure to comply with monitoring or testing procedures. The water system must notify the public within one year of the violation. These notices are frequently published in the system's annual Consumer Confidence Report (CCR), which must be distributed to all customers by July 1st of each year. The CCR summarizes information about the source water, detected contaminants, compliance with drinking water regulations, and educational health information.