A manufacturing plant needed to ensure that allowable peak styrene loadings to a Publicly Owned Treatment Works (POTW) were not exceeded. To reduce the potential for spills of styrene monomer, hazard analysis techniques were used to identify release scenarios that could impact the POTW. Recommendations were then made to reduce or eliminate the likelihood of spills. Cost estimates were done for all recommendations requiring capital outlays. A Layer of Protection Analysis (LOPA) was conducted to rank the spill scenarios by frequency. The recommendations were then assessed for their effectiveness in reducing spill frequencies using the LOPA. The analysis showed that of the 34 recommendations requiring capital outlays, 10 reduced the spill frequency by a factor of 40. The rest had a small impact on the spill frequencies. Thus, the LOPA evaluation of the recommendations saved about a half million dollars in capital outlays that would have brought little risk reduction.