{"data":{"id":"us-va/9vac25-260-170","jurisdiction":"us-va","citation":"9VAC25-260-170","heading":"Bacteria; other recreational waters","body":"A. The following bacteria criteria  (counts/100ml) shall apply to protect primary contact recreational uses in surface waters, except waters identified in subsection B of this section:\n\nIn freshwater, E. coli bacteria shall not exceed a  geometric mean of 126  counts/100ml and  shall not have greater than a 10% excursion frequency of  a statistical threshold value (STV) of 410  counts/100 ml, both in an assessment period of up to 90 days.\n\nIn transition and saltwater, Enterococci bacteria shall not exceed a  geometric mean of 35  counts/100ml and  shall not have greater than a 10% excursion frequency of  a statistical threshold value (STV) of 130  counts/100ml, both in an assessment period of up to 90 days.\n\n1. See 9VAC25-260-140 C for boundary delineations for freshwater, transition, and saltwater.\n\n2. In VPDES discharges to freshwater, bacteria in effluent requiring disinfection shall not exceed a monthly geometric mean of E. coli bacteria of 126 counts/100ml. Alternative performance standards may be established where an approved long term control plan establishes an alternative level of disinfection for a combined sewer system.\n\nIn VPDES discharges to transition and saltwater, bacteria in effluent requiring disinfection shall not exceed a monthly geometric mean of enterococci bacteria of 35 counts/100ml.\n\nB. The following bacteria criteria per 100 ml (CFU/100 ml) of water shall apply:\n\nE. coli bacteria shall not exceed a monthly geometric mean of 630 CFU/100 ml in freshwater.\n\nEnterococci bacteria shall not exceed a monthly geometric mean of 175 CFU/100 ml in transition and saltwater.\n\n1. See 9VAC25-260-140 C for boundary delineations for freshwater, transition, and saltwater.\n\n2. Geometric means shall be calculated using all data collected during any calendar month with a minimum of four weekly samples.\n\n3. 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.\n\n4. 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.\n\n5. 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.\n\n6. Surface waters designated under this subsection are as follows:\n\na. (Reserved)\n\nb. (Reserved)\n\nc. (Reserved)","path":["Title 9. Environment","Agency 25. State Water Control Board","Chapter 260. Water Quality Standards","Part II. Standards with More Specific Application"],"source_url":"https://law.lis.virginia.gov/admincode/title9/agency25/chapter260/section170/","current_through":"2026 Regular Session (effective July 1, 2026)","vintage":"","retrieved_at":"2026-09-14T04:49:14Z","sha256":"12d6423e69205fdaded363fa481e1ccce8452b5a245f646d2c372f24827718d4","source_id":"us-va-vac","stale":false,"prev":"us-va/9vac25-260-160","next":"us-va/9vac25-260-180"},"notice":"GroundRules: Original legal text. Not legal advice."}