356 
baseline analysis indicates that there could be 846 POTWs currently thac have 
at least one exceedance. The estimate of 846 is low because it does not take 
into account ambient levels of toxics in the receiving water or the contribution 
to water quality degradation due to upsets or bypass at the POTW. In addition, 
the normalizing assumptions used in modeling industrial discharge loadings 
and POTW removal efficiencies also tend to minimize the estimate of water 
quality exceedances. 
Table 4-3 shows the reduction in the number of exceedances due to the 
application of each of the options. About 61 exceedances are eliminated by 
most of the options, except for Option 2 (the existing program with categorical 
standards for metal finishing only) where 50 exceedances are eliminated. It 
is not known how effective Option 4 (water quality-based limits for POTWs) would 
be. At least 61 violations would be eliminated through this option; however, 
there are limits to the extent that exceedances can be reduced through more 
stringent controls on industry pecause in many cases non-industrial sources 
are significant contributors. Since the federal back-up for Option 5 is the 
application of categorical pretreatment standards, it is assumed that munici- 
palities will reduce at least 61 of the exceedances (as in Option Ll). 
Sensitivity analysis was performed for a broad range of factors, such 
as changes in ambient conditions and federal water quality criteria. Even 
under sensitivity analysis, the ability of the options to reduce the number of 
exceedancés remained stable, indicating that where water quality problems 
exist they are generally severe. 
- 4.5 COST, COST=EFFECTIVENESS AND BENEFITS 
This section first summarizes the cost of the options to industry and to 
POTWs and then examines the cost-effectiveness of the options. The benefits 
that are obtained from eliminating exeedences are also discussed. It was not 
practical to include analysis of economic impacts (such as industrial plant 
closures) in this report because of data limitations. 
