The leaders who signed off on the original 40 percent nutrient reduction goal in the 1987 Bay Agreement may turn out to have been closer to the mark than anyone realized.

The 40 percent goal was based on what was the best guess at the time of what it would take to clean up the Chesapeake.

Shortly after the 1987 agreement was signed, though, the 40 percent goal was significantly changed as officials added the word “controllable” to the goal. Subsequently, many of the nutrients reaching the Bay were written off as “uncontrollable,” including those originating from headwater states such as New York, West Virginia and Delaware, as well as from air pollution and a variety of other sources.

Ultimately, the “40 percent” goal became a 20 percent reduction for nitrogen and a 31 percent reduction for phosphorus for the watershed.

But a real 40 percent nitrogen reduction from the 337 million pounds of nitrogen estimated to have entered the Bay in 1985, the baseline for measuring reductions, would be 203 million pounds — a figure that falls between the Tier 2 and Tier 3 levels of effort, an area where many believe the process will end up.

For phosphorus, a real 40 percent reduction would result in 17 million pounds entering the Bay, a figure close to Tier 2.