N.Y. Comp. Codes R. & Regs. tit. 10, § 6-2.15 – Water quality monitoring.

(a) No bathing beach shall be maintained or operated on any body of water when the water quality is determined by the permit-issuing official to constitute a potential hazard to health if used for bathing. To determine if the water quality constitutes a potential hazard to health requiring closure of the beach, the permit-issuing official shall consider one or a combination of any of the following items: results of a sanitary survey; historical water quality model for rainfall and other factors; verified spill or discharge of contaminants affecting the bathing area; and water quality indicator levels specified in this section.
(b) Sample collection and analysis when required for surveillance or design purposes shall be in accordance with the frequency, locations and procedures specified by the permit-issuing official. All samples collected from bathing beaches shall be examined in laboratories possessing State Department of Health certification for water supplies.
1. (1) Based on a single sample, the upper value for the density of bacteria shall be:
  1. (i) 1,000 fecal coliform bacteria per 100 ml; or
  2. (ii) 61 enterococci per 100 ml for freshwater; or
  3. (iii) 104 enterococci per 100 ml for marine water; or
  4. (iv) 235 E. coli per 100 ml for freshwater (E. coli is not to be used as an indicator in marine water).
2. (2) Based on the mean of the logarithms of the results of the total number of samples collected in a 30 day period, the upper value for the density of bacteria shall be:
  1. (i) 2,400 total coliform bacteria per 100 ml; or
  2. (ii) 200 fecal coliform bacteria per 100 ml; or
  3. (iii) 33 enterococci per 100 ml for freshwater; or
  4. (iv) 35 enterococci per 100 ml for marine water; or
  5. (v) 126 E. coli per 100 ml for freshwater (E. coli is not to be used as an indicator in marine water).
3. (3) When the above described levels are exceeded, the permit-issuing official shall cause an investigation to be made to determine the source or sources of pollution and, along with other factors described in subdivision (a) of this section determine if the beach shall be closed.
  (d) Chemical quality.
  The water shall be free of chemical substances capable of creating toxic reactions, skin or membrane irritations to the general public.
  (e) Physical quality.
  Physical inspection shall verify that the water is free of deposits, growths, oils, greases or other substances in the water capable of creating a health or safety hazard.
  (f) Biological quality.
  Algae and aquatic vegetation shall be controlled so that no hazard to bathers result. Any chemical used to control vegetation and algae shall not be capable of creating toxic reactions, skin or membrane irritations when the beach is in operation.
(c) Bacteriological quality.
The following bacteriological indicator levels shall be used when determining acceptability of water quality for bathing beaches.