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9VAC25-260-170. Bacteria; other recreational waters.

A. The following bacteria criteria (colony forming units (CFU)/100 ml) shall apply to protect primary contact recreational uses in surface waters, except waters identified in subsection B of this section:

E. coli bacteria shall not exceed a monthly geometric mean of 126 CFU/100 ml in freshwater.

Enterococci bacteria shall not exceed a monthly geometric mean of 35 CFU/100 ml in transition and saltwater.

1. See 9VAC25-260-140 C for boundary delineations for freshwater, transition and saltwater.

2. Geometric means shall be calculated using all data collected during any calendar month with a minimum of four weekly samples.

3. If there are insufficient data to calculate monthly geometric means in freshwater, no more than 10% of the total samples in the assessment period shall exceed 235 E. coli CFU/100 ml.

4. If there are insufficient data to calculate monthly geometric means in transition and saltwater, no more than 10% of the total samples in the assessment period shall exceed enterococci 104 CFU/100 ml.

5. For beach advisories or closures, a single sample maximum of 235 E. coli CFU/100 ml in freshwater and a single sample maximum of 104 enterococci CFU/100 ml in saltwater and transition zones shall apply .

B. The following bacteria criteria per 100 ml (CFU/100 ml) of water shall apply:

E. coli bacteria shall not exceed a monthly geometric mean of 630 CFU/100 ml in freshwater.

Enterococci bacteria shall not exceed a monthly geometric mean of 175 CFU/100 ml in transition and saltwater.

1. See 9VAC25-260-140 C for boundary delineations for freshwater, transition and saltwater.

2. Geometric means shall be calculated using all data collected during any calendar month with a minimum of four weekly samples.

3. If there is insufficient data to calculate monthly geometric means in freshwater, no more than 10% of the total samples in the assessment period shall exceed 1173 E. coli CFU/100 ml.

4. If there is insufficient data to calculate monthly geometric means in transition and saltwater, no more than 10% of the total samples in the assessment period shall exceed 519 enterococci CFU/100 ml.

5. Where the existing water quality for bacteria is below the geometric mean criteria in a water body designated for secondary contact in subdivision 6 of this subsection that higher water quality will be maintained in accordance with 9VAC25-260-30 A 2.

6. Surface waters designated under this subsection are as follows:

a. (Reserved)

b. (Reserved)

c. (Reserved)

Statutory Authority

62.1-44.15 of the Code of Virginia; 33 USC 1251 et seq. of the federal Clean Water Act; 40 CFR Part 131.

Historical Notes

Derived from VR680-21-02.2, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Volume 19, Issue 7, eff. January 15, 2003; Volume 20, Issue 9, eff. February 12, 2004; Volume 26, Issue 12, eff. February 1, 2010.


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