105 CMR 445.031
Indicator Organisms
(A) For marine water, the indicator organism shall be Enterococci. No single Enterococci
sample shall exceed 104 colonies per 100 ml. and the geometric mean of the most recent five
Enterococci levels within the same bathing season shall not exceed 35 colonies per 100 ml.
(B) For fresh water, the indicator organisms shall be E. Coli or Enterococci.
(1) No single E. Coli sample shall exceed 235 colonies per 100 ml. and the geometric mean
of the most recent five E. Coli samples within the same bathing season shall not exceed 126
colonies per 100 ml; or
(2) No single Enterococci sample shall exceed 61 colonies per 100 ml. and the geometric
mean of the most recent five Enterococci samples within the same bathing season shall not
exceed 33 colonies per 100 ml.