On May 14, 2014, the U.S. Environmental Protection Agency (EPA) issued its final rule, under Section 316(b) of the Clean Water Act, requiring that facilities operating cooling water intake systems (CWIS), use best technologies available to minimize adverse environmental impacts. The purpose of the rule is to reduce impingement and entrainment of fish and other aquatic organisms by CWIS structures.

Under the rule, the performance/compliance standards for reducing entrainment mortality are to be determined on a case-by-case basis and require multiyear data that quantifies facility entrainment. To date, most entrainment samples have assumed that all entrained organisms were live when drawn into the intake along with the cooling water. However, it is well known that larval fish and their eggs experience a high percentage of natural mortality, unrelated to the facility.

In 2011, an Electric Power Research Institute report, titled, "Potential entrainment of dead and moribund fish eggs and larvae at cooling water intakes", identified the following challenges encountered throughout the U.S. regarding the assessment of entrained organisms: 1) lack of well-defined and defensible criteria that classify individuals into alive, dead, or moribund; 2) lack of detailed descriptions that credibly document evidence of the classified organisms; and 3) lack of studies that confirm ichthyoplankton condition.

With EPRI funding, LimnoTech has teamed with SENES Consultants to initiate a framework and develop content for a reference resource tool that offers standard guidance for defining categories of ichthyoplankton condition using high quality images and linked documentation for use in entrainment mortality assessments. The tool, named ENTRAIN, organizes and stores entrainment terms and definitions as well as detailed images that define and support ichthyoplankton condition categories (e.g., live, dead, moribund, etc.). The content for ENTRAIN was initially developed using freshwater organisms found in the Great Lakes region; however, the tool is flexible in design so that it is easily expandable for inclusion of other organisms.