|A juvenile striped bass impinging on water screen|
However, we still don't know what constitutes an "adverse environmental impact" because the rule, which was first introduced in 1972, does not provide a definition. The term has long been understood by the scientific community to refer to adverse changes in the abundance and productivity of fish and other aquatic life. The problem is this: There is no scientific evidence that shows a reduction in entrainment and impingement would lead to measurable improvements in fish populations.
|We recommend Wedgewire Screens as BTA|
The 316(b) rule was first enacted in 1972 when Congress passed the Federal Water Pollution Control Act Amendments (Clean Water Act). Since then, the rule has been suspended and rewritten several times in a long and drawn out legal battle between utilities and environmental groups. After 40 years, the EPA is expected to release the final rule in November.
Adverse impacts have been implicitly or explicitly defined as entrainment and impingement per se, irrespective of whether any adverse changes in populations can be demonstrated or predicted. The rarity of documentation of such impacts, after 40 years of operation of large power plants, some of which have been conducting extensive monitoring programs for several decades, provides substantial evidence that impacts related to entrainment and impingement are generally small. (Power Engineering, August 2013)