Section 421. Groundwater system treatment techniques

A. Owners of groundwater systems that (i) have confirmed E. coli contamination as described in 12VAC5-590-379 B or (ii) have been notified in writing of a significant deficiency as described in 12VAC5-590-350 D shall meet the requirements of this section. Failure to meet any requirement of this section after the applicable time period specified is a treatment technique violation.

1. Owners of groundwater systems meeting either one of the conditions in clause (i) or (ii) above shall implement one or more of the following corrective actions:

a. Correct all significant deficiencies;

b. Provide an alternate source of water;

c. Eliminate the source of contamination; or

d. Provide treatment of the groundwater source that reliably achieves at least 4-log treatment of viruses before or at the first consumer.

2. Unless the ODW directs the groundwater system owner to implement a specific corrective action, the groundwater system owner shall consult with the ODW regarding the appropriate corrective action within 30 days of receiving written notification from the commissioner or the laboratory. This consultation may take the form of a telephone conversation, electronic mail, meeting, or other mechanism agreed to by the ODW.

3. Within 45 days of receiving this notification, the groundwater system owner shall submit a written Corrective Action Plan (CAP) to the commissioner that satisfactorily addresses the deficiency. The CAP shall include a schedule for completing individual actions, and shall include one or more of the corrective actions in subdivision A 1 of this section. Approval of the CAP by the commissioner constitutes an approved CAP.

4. Within 120 days of receiving written notification from the commissioner or the laboratory, the groundwater system owner shall either:

a. Have a completed corrective action in accordance with the commissioner-approved CAP including commissioner-specified interim measures; or

b. Be in compliance with a commissioner-approved CAP and schedule subject to the conditions specified in subdivisions 4 b 1 and 2 of this subsection.

(1) Any subsequent modifications to a commissioner-approved CAP and schedule shall also be approved by the commissioner.

(2) If the commissioner specifies interim measures for protection of the public health pending the commissioner's approval of the CAP and schedule or pending completion of the CAP, the groundwater system owner shall comply with these interim measures as well as with any schedule specified by the commissioner.

5. When a significant deficiency is identified at a waterworks that uses both groundwater and surface water or a GUDI source, the owner shall comply with this section unless the commissioner has determined that the significant deficiency is in a portion of the distribution system that is served solely by surface water or a GUDI.

B. Owners of groundwater systems that provide at least 4-log treatment of viruses before or at the first customer shall conduct compliance monitoring to demonstrate treatment effectiveness.

1. Existing groundwater sources. A groundwater system that is not required to meet the source water monitoring requirements of 12VAC5-590-379 for any groundwater source(s) because the owner has been notified by the ODW that the groundwater system provides at least 4-log treatment of viruses before or at the first customer for any groundwater source(s) shall comply with the following:

a. The groundwater system owner shall have written approval from the ODW that the groundwater system provides at least 4-log treatment of viruses before or at the first customer served by the groundwater source.

b. The groundwater system owner shall conduct compliance monitoring as required by subsection C of this section within 30 days of placing the source in service.

2. New groundwater sources. A groundwater system owner that places a new groundwater source into service shall meet the requirements of subdivisions 1 a and b of this subsection and conduct raw water monitoring in accordance with 12VAC5-590-425. The groundwater system owner shall provide engineering, operational, or other information as required by the ODW.

C. The owner of a groundwater system subject to the requirements of subsection B of this section shall monitor the effectiveness and reliability of treatment for that groundwater source before or at the first customer as follows:

1. Chemical disinfection.

a. The owner of a groundwater system that serves greater than 3,300 people shall continuously monitor and record the residual disinfectant concentration using analytical methods specified in 40 CFR 141.74 (a)(2) at a location approved by the ODW and shall record the lowest residual disinfectant concentration each day that water from the groundwater source is served to the public. The groundwater system owner shall maintain the ODW-determined residual disinfectant concentration every day the groundwater system serves water from the groundwater source to the public. If there is a failure in the continuous monitoring equipment, the groundwater system owner shall conduct grab sampling every four hours until the continuous monitoring equipment is returned to service. The system shall resume continuous residual disinfectant monitoring within 14 days.

b. The owner of a groundwater system that serves 3,300 or fewer people shall monitor the residual disinfectant concentration using analytical methods specified in 40 CFR 141.74 (a)(2) at a location approved by the ODW and record the residual disinfection concentration each day that water from the groundwater source is served to the public. The groundwater system owner shall maintain the ODW-determined residual disinfectant concentration every day the groundwater system serves water from the groundwater source to the public. The groundwater system owner shall take a daily grab sample during the hour of peak flow or at another time specified by the ODW. If any daily grab sample measurement falls below the ODW-determined residual disinfectant concentration, the groundwater system owner shall take follow-up samples every four hours until the residual disinfectant concentration is restored to the ODW-determined level. A groundwater system that serves 3,300 or fewer people may monitor continuously to meet the requirements of this subsection.

c. Failure to maintain the ODW-specified minimum residual disinfectant concentration for a period of more than four hours is a violation of the treatment technique requirement.

2. A groundwater system owner that uses an ODW-approved alternative treatment to meet the requirements of this section by providing at least 4-log treatment of viruses before or at the first customer shall:

a. Monitor the alternative treatment in accordance with all ODW-specified monitoring requirements; and

b. Operate the alternative treatment in accordance with all ODW-specified compliance requirements necessary to achieve at least 4-log treatment of viruses.

3. Failure to meet the monitoring requirements of subsection C of this section is a violation and requires the groundwater system owner to provide public notification as required in 12VAC5-590-540.

D. Discontinuing compliance monitoring or treatment.

1. A groundwater system owner may discontinue compliance monitoring if the ODW determines and documents in writing that compliance monitoring is no longer necessary for that groundwater source. Owners of groundwater systems that have ODW approval to discontinue compliance monitoring shall be subject to the triggered source water monitoring requirements of 12VAC5-590-379.

2. A groundwater system owner discontinuing compliance monitoring is still subject to the requirements of 12VAC5-590-380 G.

3. Owners of waterworks with groundwater sources that have been required by the commissioner to provide at least 4-log treatment of viruses shall not discontinue treatment or monitoring.

Historical Notes

Derived from Volume 28, Issue 05, eff. December 7, 2011.

Statutory Authority

§§ 32.1-12 and 32.1-170 of the Code of Virginia.