August 9, 2000 - National Primary Drinking Water Regulations: Ground Water

Federal Register Notice:  National Primary Drinking Water Regulations: Ground Water Rule; Proposed Rules

In response to the notice published May 10, 2000, in the Federal Register, the American Society for Microbiology (ASM) would like to comment on the proposed rule National Primary Drinking Water Regulations: Ground Water Rule, under the direction of the Environmental Protection Agency (EPA).

The ASM is the premier educational and scientific society dedicated to the promotion of the microbiological sciences and their application for the common good. The Society represents more than 42,000 microbiologists, including scientists in academic, industrial and government institutions working in a variety of areas, including medical, applied, molecular biology and genetics, environmental and food microbiology, and public health.

ASM applauds the efforts of the EPA in developing the Ground Water Rule (GWR). There is little doubt that this is one of the more significant components of the Safe Drinking Water Act.

  • Groundwater is linked to more than 58% of waterborne outbreaks and in most cases the cause of the outbreak is never identified.
  • EPA estimates 168,000 illnesses per year are linked to groundwater systems.
  • The recent E. coli outbreak at a fair in New York exemplifies the need to monitor and treat non-community systems.

The rule is comprehensive and ASM supports the principal elements of the proposed rule, which include sanitary surveys, hydrogeological assessments, source water monitoring, correction of deficiencies, adequate microbial reduction of viruses, and compliance monitoring.

The ASM is concerned however, with several of the scientific approaches described in the proposed rule. For example, it has been acknowledged for several decades that coliform bacterial indicators are no longer adequate in predicting microbial water quality and public health risks. EPA recognizes the risk viruses pose to groundwater, yet fails to address virus risks in the rule. The proposed rule also fails effectively to address advances in water microbiology equipment and techniques. The ASM believes the GWR must address these inadequacies if the rule is to protect consumers from exposure to contaminated drinking water supplies in the nation's groundwater.

Short-term water providers

The ASM recommends that EPA provide guidance for non-community water systems (NCWS) and transient non-community water systems (TNCWS), particularly those that provide groundwater for events serving large numbers of people even for short time periods. Prior monitoring of use is recommended, at a minimum of 3 replicate samples at 15, 10 and 5 days, particularly for those associated with rain events. Periodic monitoring during use is also recommended as transient events may cause groundwater to become contaminated rapidly, despite prior evidence of non-contamination. For wells serving over 10,000 individuals (for any one event), sanitary surveys are also recommended.

Best Management Practices (BMP)

While this data is useful, most of the information on microbial risks is from coliform bacterial indicator data, and thus, does not provide an adequate picture of the microbial risks. Disinfection and residuals provide the greatest and most significant association, while little scientific data supports other BMPs, particularly in the control of viruses.


Thirteen studies on groundwater have been conducted with some examining as few as 17 wells and only five studies looking at 100 wells or more. Most studies took only one sample from each well. It should be acknowledged that microbial contamination is likely to be transient, and given such temporal variability, multiple samples from each well would need to be sampled. Additionally, groundwater-monitoring studies to date are not representative of geographical and national differences with respect to microbial contamination. Even with the limitations in the numbers, methods and volumes examined, fecal indicators, human viruses and Legionella were all detected in most studies.

Emerging contaminants, including new viruses, will be discovered in the future and effective monitoring programs must be in place. The ASM supports a comprehensive microbiological evaluation monitoring program, particularly during national surveys and sanitary surveys that includes:

  • Multiple indicator testing (fecal coliform bacteria, enterococci and coliphage).
  • Large volume sampling (100 to 1000ml)
  • Human virus testing
  • Molecular testing (PCR testing for emerging disease-causing viruses, bacteria, non-cultivatable viruses, source tracking[human or animal], and rapid assessment of risk [e.g. identification of E.coli 0157H7] )

Furthermore, viable non-CPE viruses are now being detected in groundwater and other waters by integrated cell culture-nucleic acid hybridization and cell culture-PCR methods. For these reasons, ASM recommends EPA develop a comprehensive molecular (PCR-based) testing program to rapidly screen characterized well systems (perhaps in conjunction with USGS) for vulnerability to virus contamination. It is further recommended that integrated cell culture-PCR methods be used in conjunction with direct PCR screening for the detection of infectious viruses that do not produce CPE.

Risk Estimates

ASM supports the use of microbial risk assessments. However, the data on microbial occurrence in groundwater is largely limited. The data used comparing PCR to cell culture, for calculating the proportion of viable viruses, certainly underestimates microbial concentrations and exposures. A new risk assessment using improved occurrence data as it is generated through monitoring should be undertaken for future revisions of the GWR.

Guidance on Sanitary Surveys

The ASM believes that monitoring is the key element in the sanitary survey. This is because it immediately provides direct evidence of microbial contamination and risk. Five-year sanitary surveys are also needed and should include more detailed analysis, using microbial monitoring, GIS mapping of groundwater aquifers, wells and sources of pollution (septic tanks, sewer lines). We agree with EPA that individual State set back distances are not virus risk based and are not necessarily indicative of risk or protection. Only through the gathering of water quality data will the public health risks be identified, recognized and thus finally controlled.

Alternative approaches to Hydrogeological Sensitivity Assessment

Virus transport models are not adequate at this time to predict risk. Until such models become acceptable the ASM supports virus monitoring and sanitary surveys. The hydrogeologic sensitivity assessment component of the Rule is extremely weak. Addressing this complex issue has been left to the States. This allows each State to undertake it's own assessments. However, States may not have the expertise or resources to handle this aspect of theRule. This is likely to result in very different water qualities across the country, as some states will be more rigorous than others.

Monitoring Disinfecting Systems and all Systems

ASM strongly supports the monitoring of all systems, regardless of treatmentlevels, as a high percentage of waterborne outbreaks (~40%) occur in systems that were disinfecting.

The Ground Water Rule is important to the safety of drinking water in the U.S. but should be viewed as a first-step, with greater potential to be more fully developed in the future. The latest advances in microbiological methods and a comprehensive microbiological monitoring program needs to be incorporated into the language of the rule, particularly as triggered monitoring (Table VI-6, pg. 30262) has the greatest impact of all options in reducing illness.

Sandy Aquifers

EPA identifies karst, gravel and fractured rock aquifer settings as sensitive and proposes that these systems must perform routine source water monitoring. The EPA Drinking Water Committee Science Advisory Board (DWCSAB) recommended that sandy aquifers also are designated as sensitive and be subject to the same monitoring requirements. About 1/3 of the nation's production wells will be found in sandy aquifers and more information is needed to determine their vulnerability category. The ASM supports the approach of identifying sensitive aquifers and requiring them to be routinely monitored. In addition, the ASM strongly supports the inclusion of sandy aquifers in the category of high vulnerability (experimental evidence from laboratory and field studies have demonstrated the persistence and mobility of viruses in sandy aquifers). Groundwater from such aquifers has also been found repeatedly to be contaminated with enteric viruses and to be responsible for waterborne outbreaks. Exclusion of sandy aquifers from the category of sensitive settings, which requires monitoring, will cause consumers to remain at risk of virus exposure from public water supplies using such aquifers.

Treatment to Achieve 99.99% Reduction of Viruses

The Rule allows utilities to install a single barrier to microbial contamination - disinfection - as a solution to microbial contamination. The ASM is concerned that a single barrier, such as an UV system, will be inadequate in inhibiting microbial contamination. Unfortunately, there is currently no satisfactory way to continuously monitor the efficacy of an UV system or ensure that it is working at the level required to achieve a 4-log removal. In addition,with an UV system there is noresidual in place. An additional concern is the relatively small number of systems impacted by this rule and the number of full-time operators assigned to a system. In many cases, the operator will have little or no training on how these systems work. Additional guidance will be needed to implement and reliably assess any treatment technology.

The ASM appreciates the opportunity to provide comments in response to the proposed rule for the National Primary Drinking Water Regulations: Ground Water Rule and hopes that these recommendations provide assistance as the EPA prepares its final rule on this important topic.