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Small Drinking Water System Variances

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A small system variance enables a public water system to utilize a treatment technology that achieves the maximum removal of the contaminant that is both affordable and protective of public health, but does not remove the contaminant to the degree specified by the drinking water regulation. States may grant small system variances only for those drinking water standards that EPA has determined are unaffordable for one or more categories of small systems.

To date, EPA has found its new and existing non-microbial drinking water rules to be affordable. Therefore small system variances have not been available for states to issue to small systems. For future non-microbial contaminant rules, EPA will evaluate the need for small systems variances based on affordability analyses.

Small System Definition

Under the Safe Drinking Water Act (SDWA), small public water systems (PWSs) are broadly characterized as systems serving 10,000 or fewer customers. This category of systems represents more than 92% of the nation’s 51,000 community water systems (CWSs), and nearly all of the 100,000 non-community water systems. SDWA further breaks down small systems into those serving 3,301 – 10,000 persons, those serving 501 – 3,300 persons, and those serving 500 persons or fewer.

Some small systems face unique financial and operational challenges in providing drinking water that meets EPA standards. To address these challenges, EPA encourages and supports utilization of small system compliance and sustainability tools to strengthen and target financial support to small systems, including working with United States Department of Agriculture Rural Utilities Service, strengthening capacity development tools and promoting restructuring of non-sustainable systems.

SDWA Provisions for Small System Variances

In the 1996 amendments of the Safe Drinking Water Act (SDWA), Congress authorized the potential use of small system variances (SSV) to address small system challenges. A SSV would allow a small system to use a variance technology that:
  • does not reduce a contaminant to the level required by the regulation,
  • is affordable, and
  • is protective of public health.

States do not have the authority to grant small system variances from national primary drinking water regulations unless EPA makes two determinations at the time it promulgates the regulation. First, EPA must determine for small systems of a similar size and with similar source water that there are no affordable technologies available that achieve compliance with the standard. Second, EPA must also determine that there are affordable variance technologies available that are “protective of public health.” 

The SDWA specifically does not allow small system variances for the following:
  • any contamininant MCL or treatment technique promulgated prior to January 1, 1986; or
  • for microbial contaminants.
EPA’s existing methodology for determining whether there are affordable compliance technologies for a new drinking water standard for small systems was published in the Federal Register in 1998 (63 FR 42032). It compares the cumulative cost of providing drinking water that complies with the new standard to an affordability threshold equal to 2.5% of median household income (about $1,100).
For national primary drinking water regulations (NPDWRs) promulgated before the 1996 SDWA amendments, EPA was required to: 
  • list technologies for small systems that meet the Surface Water Treatment Rule;
  • issue a list of technologies that achieve compliance with the MCLs or treatment technique requirements for other existing NPDWRs; and
  • issue guidance or regulations for variance technologies for the existing NPDWRs for which a small system variance can be granted.

Re-evaluation of Small System Variance Policies

In 2002, Congress required EPA to re-evaluate small system variance policy because of the concern with the high cost of arsenic treatment in small communities. In response, in 2003, EPA consulted with the National Drinking Water Advisory Council (NDWAC) and the Science Advisory Board (SAB). The SAB and NDWAC made a number of recommendations regarding the method by which EPA evaluates the affordability of compliance with drinking water standards.
Some key recommendations made by both the SAB and the NDWAC include:
  • EPA should consider the household cost of each new regulation on an incremental basis rather than a total cost of all water treatment regulations, and
  • EPA should consider reducing the current affordability threshold.

Links to the two reports are below:

SAB Report

NDWAC Report

In 2006, EPA published a Federal Register notice to request comment on revisions to EPA’s national affordability methodology for small drinking water systems and a methodology for determining if an affordable variance technology is protective of public health. The proposal described a number of options for revising the affordability methodology for public review and comment. 

Federal Register Notice: Small Drinking Water System Variances – Revision of Existing National-Level Affordability Methodology and Methodology to Identify Variance Technology that is Protective of Public Health