Section 379. Groundwater waterworks monitoring

A. General monitoring requirements.

1. Owners of groundwater waterworks, including consecutive and wholesale waterworks, shall conduct monitoring in accordance with this section, except that requirements do not apply to waterworks that combine all of their groundwater with surface water or with groundwater under the direct influence of surface water prior to treatment in accordance with 12VAC5-590-420.

2. Source water monitoring for owners of groundwater waterworks that do not provide 4-log treatment of viruses for their groundwater sources before or at the first customer are described in subsection B of this section.

3. Owners of groundwater waterworks that provide at least 4-log treatment of viruses before or at the first customer are required to conduct compliance monitoring in accordance with 12VAC5-590-421 C.

4. Owners of groundwater waterworks that have confirmed fecal contamination, as determined by source water monitoring conducted under subsection B of this section or have been notified of a significant deficiency as described in 12VAC5-590-350 D shall implement one or more of the corrective actions outlined in 12VAC5-590-421 A 1, as prescribed by the commissioner.

5. Owners of groundwater waterworks that do not provide 4-log treatment of viruses before or at the first customer and are not performing compliance monitoring shall provide triggered source water monitoring plans to the commissioner.

6. Any source water sample collected in accordance with this section shall be analyzed for E. coli using one of the analytical methods in 40 CFR 141.402(c).

B. Groundwater source microbial monitoring.

1. Triggered source water monitoring.

a. General requirements. Groundwater waterworks owners shall conduct triggered source water monitoring if both the conditions identified in subdivisions B 1 a (1) and (2) of this section exist.

(1) The groundwater waterworks does not provide at least 4-log treatment of viruses before or at the first customer for each groundwater source; and

(2) The groundwater waterworks owner is notified that a sample collected under 12VAC5-590-370 A is total coliform-positive and the sample is not invalidated under 12VAC5-590-380 E.

b. Sampling requirements. Groundwater waterworks owners shall collect, within 24 hours of notification of the total coliform-positive sample, one groundwater source sample from each groundwater source in use at the time the total coliform-positive sample was collected under 12VAC5-590-370 A, except as provided in this subdivision B 1 b.

(1) The commissioner may extend the 24-hour time limit on a case-by-case basis if the owner cannot collect the groundwater source water sample within 24 hours due to circumstances beyond his control. In the case of an extension, the commissioner shall specify how much time the owner has to collect the sample.

(2) If approved by the commissioner, owners of waterworks with more than one groundwater source may meet the requirements of this subdivision B 1 by sampling a representative groundwater source or sources. Owners shall submit, for the commissioner's approval, a triggered source water monitoring plan that identifies one or more groundwater sources that are representative of each monitoring site in the waterworks' bacteriological sample siting report or that identifies groundwater sources that are hydro-geologically similar and clearly identifies which sources will be sampled.

(3) A groundwater system serving 1,000 people or fewer may use a triggered source water sample collected from a groundwater source to meet both the requirements of 12VAC5-590-380 and to satisfy the monitoring requirements of this subdivision B 1 for a groundwater source.

c. Additional requirements.

(1) If an E. coli-positive triggered source water sample collected under this subdivision B 1 is not invalidated under subdivision B 2 of this section, the groundwater waterworks owner shall provide public notification and collect five additional source water samples from the same source within 24 hours of being notified of the E. coli-positive sample.

(a) If the E. coli-positive triggered source water sample is also used as a repeat sample, then an E. coli PMCL violation is incurred under 12VAC5-590-380 B 1 a.

(b) If a waterworks takes more than one repeat sample at the monitoring location required for triggered source water monitoring, then the number of additional source water samples required under subdivision B 1 c (1) of this section may be reduced by the number of repeat samples taken at that location that were not E. coli positive.

(2) If any of the five additional samples are E. coli positive, the groundwater system owner shall comply with the treatment technique requirements of 12VAC5-590-421.

d. Consecutive and wholesale waterworks.

(1) A consecutive groundwater waterworks owner that has a total coliform-positive sample collected in accordance with 12VAC5-590-370 A shall notify the wholesale waterworks owner and the district engineer within 24 hours of being notified of the total coliform-positive sample.

(2) A wholesale groundwater waterworks owner shall comply with the following:

(a) A wholesale groundwater waterworks owner that receives notice from a consecutive waterworks it serves that a sample collected in accordance with 12VAC5-590-370 A is total coliform-positive shall, within 24 hours of being notified, collect a sample from its groundwater source(s) as described in subdivision B 1 of this section.

(b) If the sample collected under this subdivision B 1 is E. coli positive, the wholesale groundwater system owner shall within 24 hours notify all consecutive waterworks served by that groundwater source of the E. coli source water positive sample as described in 12VAC5-590-540 and shall meet the requirements of subdivision B 1 c of this section.

e. Exception to the triggered source water monitoring requirements. A groundwater system owner is not required to comply with the source water monitoring requirements of this subdivision B 1 if the commissioner determines, and documents in writing, that:

(1) The total coliform-positive sample collected in accordance with 12VAC5-590-370 A is invalidated under 12VAC5-590-380 E.

(2) The total coliform-positive sample collected in accordance with 12VAC5-590-370 A is caused by a distribution system deficiency (sanitary defect).

(3) The total coliform-positive sample collected in accordance with 12VAC5-590-370 A was caused by distribution system conditions that will cause total coliform-positive samples.

2. Invalidation of an E. coli-positive groundwater source sample.

a. A groundwater waterworks owner may obtain the commissioner's invalidation of an E. coli-positive groundwater source sample collected under subdivision B 1 of this section only under the conditions specified in subdivisions B 2 a (1) and (2) of this section:

(1) The groundwater waterworks owner provides the commissioner with written notice from the laboratory that improper sample analysis occurred; or

(2) The commissioner determines and documents in writing that there is substantial evidence that the E. coli-positive groundwater source sample is not related to source water quality.

b. If the commissioner invalidates an E. coli positive groundwater source sample, the groundwater system owner shall collect another source water sample under subdivision B 1 of this section within 24 hours of being notified by the commissioner of the invalidation decision and have it analyzed for E. coli.

3. Sampling location. All groundwater source samples required under subdivision B 1 of this section shall be collected at a location prior to any treatment of the groundwater source unless otherwise approved by the commissioner.

4. Public notification. The owner of a groundwater waterworks with a source sample collected under this subsection that is E. coli positive and that is not invalidated under subdivision B 2 of this section, including consecutive waterworks served by the groundwater source, shall conduct public notification as required in 12VAC5-590-540 A 1.

5. Monitoring violations. Failure to meet the monitoring requirements of subdivision B 1 of this section is a violation and requires the groundwater waterworks owner to provide public notification as required in 12VAC5-590-540 A 3.

Historical Notes

Derived from Volume 28, Issue 05, eff. December 7, 2011; amended, Virginia Register Volume 33, Issue 03, eff. November 2, 2016.

Statutory Authority

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