Understanding the Requirements of the National Primary Drinking Water Standard’s Ground Water Rule
Part 1: System Evaluation and Assessment for Susceptibility to Fecal Contamination; A Risk-targeted Approach
Steve Cason and Cary Jackson, Ph.D.z
Hach Company
5600 Lindbergh Drive
Loveland, Colorado 80539 USA
Introduction
The United States Environmental Protection Agency (USEPA) published the Ground Water Rule1 (GWR) on November 08, 2006 with the intention of bringing systems that use ground water as a source to similar infrastructure and disinfection standards as the Surface Water Treatment Rule2. The requirements of the GWR apply to all Public Water Systems (PWSs), Community Water Systems (CWSs), and Non-community Water Systems (NCWSs) that use ground water sources, in whole or in part (including consecutive systems that receive finished ground water from another PWS), except where PWSs combine ground water with surface water or ground water under the direct influence of surface water (GWUDI) prior to treatment under the SWTR.
Specifically, the GWR establishes a risk-targeted approach to identify ground water systems that are susceptible to fecal contamination. The occurrence of fecal indicators in a drinking water supply is an indication of the potential presence of microbial pathogens that may pose a threat to public health. This Rule requires ground water systems that are at risk of fecal contamination to take corrective action to mitigate cases of illnesses and deaths due to exposure to microbial pathogens. Corrective action includes changes to plant infrastructure, plant management, source water monitoring, disinfection treatment, and compliance monitoring. Public Water System compliance with the GWR is scheduled for December 1, 2009. This series of articles is intended to deconvolute the intricacies of the GWR that relates to fecal contamination and pathogen disinfection.
Part 1: System Evaluation and Assessment for Susceptibility to Fecal Contamination; A Risk-targeted Approach
The GWR establishes a risk-targeted approach to identify a subset of approximately 147,000 public water systems that are susceptible to fecal contamination. The GWR further requires systems that have been identified as susceptible to fecal contamination, to incorporate disinfection and provide disinfection residual monitoring to insure 4-log treatment of viruses (99.99% inactivation and removal. The risk-targeted strategies include the following:
* regular GWR Sanitary Survey evaluation and assessment
* historical evaluation of Total Coliform Rule 3 (TCR) monitoring results
* ground water source monitoring to detect fecal contamination of PWSs that do not provide 4-log removal of pathogens
* treatment techniques that sufficiently address deficiencies detected from the Sanitary Surveys
* compliance monitoring to insure 4-log treatment of viruses
Sanitary Surveys
Similar to the SWTR, the GWR requires each PWS to conduct regular sanitary surveys to assess deficiencies in eight key operational areas:
1) source
2) treatment
3) distribution system
4) finished water storage
5) pumps, pump facilities, and controls
6) monitoring, reporting, and data verification
7) system management and operation
8) operator compliance with state requirements
When a significant deficiency is identified by the sanitary survey, the PWS must as directed by the State, to take immediate corrective action to mitigate the situation. Failure to take corrective action may result in fines, penalties, and the PWS providing an alternate supply of water to its community.
Significant deficiencies may include, but are not limited to, the following:
Source
* well near a source of fecal contamination (e.g., failing septic systems or a leaking sewer line)
* well in a flood zone
* improperly constructed well (e.g., improper surface or subsurface seal)
* spring boxes that are poorly constructed and/or subject to flooding
Treatment
* inadequate application of treatment chemicals (e.g., disinfection contact time is inadequate)
* lack of redundant mechanical components where disinfection is required
* unprotected cross-connections with treatment chemical systems
* inadequate treatment process monitoring
Distribution System
* negative pressures that could result in the entrance of contaminants
* inadequate disinfectant residual monitoring, when required
* unprotected cross-connections
Finished Water Storage
* inadequate internal cleaning and maintenance of storage tanks
* lack of proper screening of overflow pipes, drains, or vents
Source Water Monitoring
Source water monitoring is an effective tool to identify and target at-risk systems that must take corrective action. Indicators of risk may come from total coliform monitoring, hydrogeologic sensitivity analysis, or other system information. Ground water systems that have a distribution system TCR sample that is positive for total fecal coliforms is required to conduct triggered source water monitoring to evaluate and discern whether the total coliform present is due to fecal contamination in the source water. A GWS that does not provide 4-log treatment of viruses must conduct triggered source water monitoring upon being notified that a TCR sample is positive.
Triggered source water monitoring requires testing for one of three State-specified fecal indicators (E. coli, enterococci, or coliphage). Upon receiving a fecal-positive result from the source water sample, the GWS is required to notify the State and the public. Unless directed by the State to take immediate corrective action, the GWS must collect and analyzes five additional source water samples within 24 hours. If any one of these samples is fecal indicator positive, the GWS must notify the State and the public and begin to comply with treatment technology requirements. Corrective action is determined in conjunction with the State or primacy agency.
Treatment Technology Requirements
Specific treatment technique requirements are triggered when significant deficiencies identified during the sanitary survey or if any one of the five additional ground water source samples has tested positive for fecal contamination. When one or more significant deficiencies have been identified, the GWS is required to implement at least one or more of the following corrective actions:
* correct and mitigate all significant deficiencies;
* provide an alternative source of water;
* eliminate the source of contamination; or
* provide treatment that achieves at least 4-log inactivation or removal of viruses
The GWS is also required to notify the public served by the water system of the situation and of any uncorrected significant deficiencies and/or fecal contamination in the ground water source.
Compliance Monitoring
Compliance monitoring is the verification of 4-log inactivation and removal of viral and bacteriological pathogens of the GWR. All public water, community water, and non-community water systems that provide 4-log treatment of viruses using chemical disinfection, membrane filtration, or a State-approved alternative treatment technology (e.g., ultra-violet radiation) must conduct compliance monitoring to demonstrate treatment effectiveness.
Alternative Treatment Technologies and the Verification of Pathogen Disinfection (Compliance Monitoring)
The description of treatment technology alternatives that lead to pathogen disinfection and the details of compliance monitoring to meet the requirements of the GWR are discussed in Part 2 of this series of articles: Understanding the Requirements of the National Primary Drinking Water Standard’s Ground Water Rule.
1 Federal Register / Vol. 71, No. 216 / Wednesday, November 8, 2006 / Rules and Regulations
2 Federal Register / Vol. 63, No. 241 / Wednesday, December 16, 1998 / Rules and Regulations
3 Federal Register / Vol. 54, No. 124 / Thursday, June 29, 1989 / Rules and Regulations