Finding NEMO (Near-optimal Entrainment Mitigation Options)

The new 316(b) rule requires facilities withdrawing more than 2 MGD to achieve a site-specific BTA for entrainment mortality reduction.  In many cases, particularly for larger cooling water withdrawals, BTA selection should consider a range of technologies and operating practices, including flow reduction, exclusion, and avoidance-inducing options.  Quantitative evaluation requires a detailed analysis  framework in which all information inputs are clearly identified.  Some types of information may be unavailable, therefore assumptions used as surrogates for the information need to be recognized and evaluated.  We present a framework for the evaluation, the types of information required, and present examples where the BTA determination may be adversely affected by commonly used assumptions used instead of actual information.