The Groundwater Rule
The GROUNDWATER RULE (GWR) was published in November of 2006 and takes effect on December 1, 2009. This rule will impact all public water systems that utilize groundwater including systems that purchase groundwater and mix groundwater and surface water.
The GWR will impact water systems in the following areas:
- Source water sampling
- Compliance Sampling
- Corrective Actions
There are actions a groundwater system can take to get ready for the GWR. DWB has prepared a FACT SHEET to assist water systems in preparing for the GWR.
Small water systems may face a unique set of challenges in complying with the GWR. Small systems should read the COMPLYING WITH THE GROUND WATER RULE: SMALL ENTITY COMPLIANCE GUIDE for background information and guidance on complying with the GWR.
Source Water Sampling
If a Groundwater System (GWS) has any routine bacteriological samples that are total coliform-positive, it will be required to collect at least one sample from each ground water source in use at the time the total coliform-positive sample was collected. Triggered source water monitoring is used to determine if fecal contamination is present in the ground water source. If a triggered source water sample tests positive for E. coli, the GWS must take corrective action at the direction of the Environment Department.
If a GWS serves fewer than 1,000 people, they may use the triggered source water sample collected from a ground water source (as described above) to meet both the requirements of the GWR and part of the requirements for repeat sampling under the Total Coliform Rule (TCR) when it has a coliform positive sample in the distribution system.
A GWS can forgo triggered source water sampling if 4-log virus inactivation/removal can be demonstrated and continuous disinfection monitoring is installed.
The GWR has additional triggered source water monitoring requirements that apply to consecutive systems and their wholesale systems. If a consecutive system is notified that a sample it collected for compliance with the total coliform rule is total coliform positive, that consecutive system is required to notify its wholesale system of the positive sample. The wholesale system is then required to perform triggered source water monitoring if 4-log treatment is not provided by the wholesale system. If a triggered source water sample collected by the wholesale system is positive for a fecal indicator, the wholesale system must notify all consecutive systems served by that groundwater source of the fecal indicator source water positive result. For more information and guidance on the GWR requirements for consecutive systems, refer to the CONSECUTIVE SYSTEM GUIDE FOR THE GROUNDWATER RULE.
You can view DWB's guidance document MICROBIOLOGICAL SAMPLING REQUIREMENTS SUMMARY FOR GROUND WATER SYSTEMS UNDER BOTH THE TOTAL COLIFORM RULE (TCR) & GROUND WATER RULE (GWR).
4-log Treatment of Viruses
Groundwater systems that provide 4-log treatment of viruses (either as a corrective action or to avoid triggered source water monitoring) must be certified by the DWB. Systems desiring to be certified as providing 4-log treatment of viruses must complete the APPLICATION FOR GROUNDWATER RULE 4-LOG CERTIFICATION and provide all information requested by the DWB. To aid water systems in performing the necessary calculations, DWB has created the GUIDANCE FOR DETERMINING FREE CHLORINE CONTACT (CT) TIME TO ESTABLISH 4-LOG INACTIVATION OF VIRUSES.
Compliance Monitoring and Reporting (for 4-log treatment of viruses)
GWSs that use chemical disinfection and serve more than 3,300 people must continuously monitor it's disinfectant concentration. GWSs must maintain the minimum disinfectant residual concentration determined by the state. Other methods to provide 4-log treatment of viruses must also be approved by DWB, and monitoring and requirements will vary depending upon the type of treatment used.
GWSs that use chemical disinfection for 4-log treatment of viruses and serve 3,300 people or fewer must take daily grab samples at the time of peak flow or meet the continuous monitoring requirements described for GWSs serving more than 3,300 people. DWB has created a GROUNDWATER RULE MONTHLY OPERATING REPORT to assist water systems in tracking 4-log treatment.
Corrective Actions
If a source water sample tests positive for E. coli, the Environment Department will require the GWS to take corrective action. The corrective action will include at least one of the following:
- Correct all significant deficiencies that have been identified as possible causes of the contamination.
- Provide an alternate source of water.
- Eliminate the source of contamination.
- Provide treatment that reliably achieves at least 4-log treatment of viruses (using inactivation, removal, or a state-approved combination of 4-log virus inactivation and removal) before or at the first customer for the ground water source.
EPA has produced the CORRECTIVE ACTIONS GUIDANCE MANUAL to assist States and Public Water Systems (PWSs) to select and implement corrective actions in response to significant deficiencies identified during sanitary surveys or in response to fecal contamination of source water as required under the Ground Water Rule (GWR).
Additional Information
For more information, view the EPA GWR WEB PAGE, EPA's GWR FACT SHEET EPA's GWR QUICK REFERENCE GUIDES or EPA's articles that covers the basics of the GWR; the second article which covers Triggered and Additional Source Water Monitoring; and the third article which covers Compliance Monitoring and Assessment Source Water Monitoring. In addition, read the GWR NOTIFICATION LETTER sent by the Drinking Water Bureau to all public water systems potentially impacted by the GWR.
Contact Mike Huber at 505-476-8638 or Andy Edmondson at 505-476-8631 for additional information.