Evaluation of water quality using acceptance sampling by variables

Under section 303(d) of the Clean Water Act, states must identify water segments where loads of. pollutants are violating numeric water quality standards. Consequences of misidentification are quite important. A decision that water quality is impaired initiates the total maximum daily load or TMDL planning requirement. Falsely concludin~ that a water segment is impaired results in unnecessary TMDL plannine and oollution control i~n~lemeniation costs. On the other hand. hlscly concluding that a ,&ment is not in lp~~rcd m.8~ pose a nrk to human health or to the sen ices of the aquatic environment. Becausc of the cunsequencc,, a method 1s dc,ired that minimizes or controls the error rates. The most commonlv applied aooroach is to use the Environmental . .. .. Protection Agency (EPA)'s mw score approach in which a stream scgmrnr is lirted 31 impired when grcaler than 10 per cent of the measurements of water quality conditions exceed a numeric criteria. An alternative to the EPA