Groundwater Quality Regulation: SDWA, UIC, and State Programs

Groundwater quality regulation: key concepts and programs

• Groundwater is a critical resource: only about $2\%$ of the world’s water is freshwater; within that freshwater: $68\%$ is in ice caps/glaciers, $2\%$ is in surface water, and $30\%$ is groundwater. Thus groundwater becomes one of the most important sources of freshwater.
  • This elevates the importance of groundwater quality regulation in environmental law.

Safe Drinking Water Act (SDWA) and groundwater

• The SDWA is a primary way the federal government regulates groundwater quality.

• How it works:

  • The EPA proposes both Maximum Contaminant Level Goals (MCLG) and Maximum Contaminant Levels (MCL).
  • MCLG is a nonenforceable goal; it is almost always zero for a contaminant.
  • MCL is an enforceable, achievable standard; it can depend on the natural background of the raw source water (e.g., naturally elevated arsenic or copper when water flows through ore bodies).
  • Public water systems: regulated entities are those serving an average of $25\text{ people per year}${ or $15\text{ service connections}$; very small drinking water systems may not be regulated under the SDWA and may be governed by state programs.
  • SDWA applies to public water systems that provide water for human consumption.

• Additional SDWA provisions that contribute to groundwater regulation:

  • Treatment techniques: required treatment methods depending on source water characteristics. Treatments range from filtration (e.g., slow sand filtration, granular activated carbon) to advanced methods like reverse osmosis (RO).
  • Action levels: thresholds for contaminants such as lead and copper; if exceeded, trigger public notification and corrosion control requirements.
  • These collectively form the national primary drinking water standards.

• Sanitary surveys (a key enforcement and compliance tool):

  • State agencies conduct sanitary surveys of each public water system to verify compliance with SDWA/ Safe Drinking Water Act requirements.
  • Inspections review sampling for MCLs and action levels, consumer confidence reports, reporting requirements, and record retention.
  • Public water system reporting and transparency are emphasized via consumer confidence reports.

• Monitoring Assistance Programs (MAPs):

  • MAPs assist small or rural drinking water systems with monitoring and compliance costs.
  • As standards tighten (lowered levels for contaminants), costs to treat and monitor water can rise, especially when concentrations drop below detection limits.
  • MAPs help offset these costs; funding may come from state programs to support very small systems that lack revenue to stay compliant.
  • This can affect public water systems’ pricing and economics.

• Groundwater under the direct influence of surface water (GWUDI):

  • SDWA requires treatment depending on source water; groundwater that is influenced by surface water may require more stringent treatment because it can resemble surface water (e.g., higher likelihood of bacteria, E. coli, fungi, algae).
  • Concept explained with a riverbed illustration:
  • A shallow well near a river may draw water that behaves like surface water (subflow), requiring more treatment.
  • An aquitard (layer of clay or granite) might block surface water from seeping into groundwater, yielding true groundwater. However, the cone of depression around a well can extend beyond the aquitard, causing some surface water influence.
  • Practical takeaway: the degree to which groundwater requires surface-water–like treatment depends on local hydrogeology and well placement.

• Sole source aquifer designation:

  • The EPA can designate an aquifer that provides at least $50\%$ of the overlying land's drinking water as a sole source aquifer.
  • Implications:
  • Projects receiving federal funds are not approved if they risk contaminating the aquifer.
  • Federal funds can be made available for projects that protect/improve the sole source aquifer.

• Wellhead protection program:

  • Implemented at state/local levels.
  • Community groups establish land-use requirements around wells to minimize contamination, typically through zoning laws.

• Underground Injection Control (UIC) program:

  • Also under SDWA; regulates injection into wells of any regulated substance that could affect underground drinking water sources.
  • Assumes all aquifers are underground drinking water sources unless stated otherwise; injection requires a UIC permit from the EPA.

• Carbon sequestration under the UIC program:

  • New class of UIC permits for injecting sequestered carbon (to mitigate climate change) into underground formations.
  • Carbon streams may contain impurities (e.g., mercury); impurities can contaminate groundwater, illustrating the Hardin principle: you cannot do just one thing without other impacts.
  • Sequestration activities are regulated to manage these ancillary risks.

• Septic tanks and UIC:

  • Septic tanks are permitted under UIC only if they are large-capacity (non-single residences) systems, i.e., multiple residences or nonresidential systems serving 20 people or more.
  • This regulatory approach seeks to prevent groundwater contamination from septic systems at larger scales.

• Fracking and UIC exemptions (controversial):

  • Hydraulic fracturing (fracking) injects high-pressure fluids into shale formations to release natural gas and has impacts on groundwater risk.
  • In the UIC framework, fracking has been exempted from UIC regulation, which is a major point of controversy.
  • Arguments around fracking involve a trade-off: potential groundwater contamination risk vs. potential energy independence and relatively cleaner combustion (natural gas vs. oil/coal) with climate considerations.
  • The Hardin principle is cited here again: it’s not possible to optimize for one objective without affecting others.

• State-level regulation and examples (high-level):

  • In many cases, state governments shoulder the primary responsibility for protecting groundwater quality; federal role is complemented by state programs.
  • Arizona example:
  • Aquifer Protection Permit (APP) program: regulates discharges of pollutants directly into the aquifer or into the vadose zone, or any discharge with a reasonable probability of reaching the aquifer.
  • APPs often include:
    • Exemptions (some categorical exemptions, e.g., household uses).
    • General permits or area-wide permits for contiguous properties owned by a single entity, providing one point of compliance.
    • Aquifer water quality standards tied to SDWA MCLs; pollutant allocations assigned to each permittee to comply with aquifer standards.
  • Water Quality Assurance Revolving Fund (WQARF): Arizona’s fund dedicated to cleaning up contaminated aquifers and protecting groundwater from pollution, including nonhazardous substances like sulfates.
  • Additionally, Arizona has specific well drilling requirements: to drill a well, one must be a licensed well driller and comply with well-drilling standards.
  • A common source of groundwater contamination is faulty well construction.
  • New Mexico example:
  • Rather than a single aquifer permit, there are multiple discharge permits for a facility, illustrating a different regulatory approach to groundwater protection compared to Arizona.

• Takeaways on regulation: state-by-state variation

  • Groundwater quality regulation is not uniform across the United States.
  • Unlike the Clean Water Act, groundwater regulation shows significant state-by-state differences in structure and stringency.
  • The course will revisit these differences in more depth in the next module/course.

• Ethical, practical, and policy implications highlighted in the lecture

  • Hardin principle (cannot do just one thing): climate policy, energy development (fracking) vs. groundwater protection involve trade-offs between multiple environmental and public health goals.
  • Economic considerations: tightening standards increases monitoring/treatment costs, potentially impacting water pricing and small systems disproportionately; MAPs are one mitigation strategy.
  • Federal vs. state roles: while SDWA sets baseline federal standards, many groundwater protections are implemented at the state level, leading to varied regulatory landscapes.

• Key terminology recap

  • MCLG: Maximum Contaminant Level Goal (nonenforceable, often zero)
  • MCL: Maximum Contaminant Level (enforceable standard)
  • GWUDI: Groundwater Under the Direct Influence of Surface Water
  • Subflow: water flow influenced by surface water entering shallow groundwater near surface water bodies
  • Aquitard: a layer that can impede groundwater flow (e.g., clay or granite)
  • Cone of depression: the drawdown cone around a pumping well that can extend beyond natural barriers and alter groundwater characteristics
  • Sole source aquifer: aquifer designated as providing at least 50% of overlying drinking water and receiving federal protection/funding considerations
  • UIC: Underground Injection Control program (regulates injection into subsurface wells to protect groundwater)
  • APP: Aquifer Protection Permit (Arizona-specific program)
  • WQARF: Water Quality Assurance Revolving Fund (Arizona)
  • MAP: Monitoring Assistance Programs (state-funded support for small systems)

• Final note on regulation landscape

  • Groundwater quality protection combines federal standards (SDWA) with state programs that tailor implementation (e.g., APP, WQARF, well drilling licenses, discharge permits).
  • The regulatory approach can vary dramatically from state to state (e.g., Arizona vs. New Mexico), with implications for compliance costs, monitoring, and groundwater protections.
  • The course will explore these differences further in the next course, reinforcing the idea that groundwater regulation is not monolithic and requires understanding local hydrogeology, regulatory frameworks, and policy trade-offs.