A "D-plus" grade usually signals underachievement. Not only is it below average, but it's barely above failure.

That said, members of the Chesapeake Bay Foundation are somewhat cheered by the D-plus grade they gave the Chesapeake last week. Not only does it exceed the D-minus grade of the previous year, but it managed to achieve that rating despite two major storms that dumped large amounts of sediment in the bay.

The September 2011 storms — Hurricane Irene and Tropical Storm Lee — created record flood levels along the Susquehanna River. Runoff from farms, developments, streets, construction sites, etc., infiltrated the bay. Large amounts of sediment cloud the water and prevent sunlight from reaching grasses. That deprives the plants of oxygen and creates dead zones.

But dead zones formed in the wake of the two storms were the second-smallest since 1985. The Foundation, in its 2012 State of the Bay report, attributed the smaller dead zones to increased efforts on the part of states, including Pennsylvania, to limit runoff and reduce pollution.

Lancaster County farmers have been pressured to improve practices and reduce runoff through no-till farming methods and by creating buffers around streams. Lancaster Farming reports that farmers are being encouraged to plant switchgrass — a plant that not only takes up nutrients but can be used for bedding or, because of its high carbon content, can be sold as a fuel.

Pennsylvania also is one of three states — Maryland and West Virginia are the others — that have been pushing nutrient trading as a cost-effective, environmentally sound way to meet looming pollution deadlines.

Although the practice has its critics, farmers who put in place conservation measures beyond those that are required are assigned nutrient credits by the state Department of Environmental Protection can then sell the credits to industries that need to expand capacity or reduce the amount of phosphorus or nitrogen discharged into local streams and eventually the Chesapeake Bay.

Communities throughout the county also play a role. Lancaster city has embarked on a $140 million program to retrofit parking lots with porous pavement that will lessen runoff from storms and thus contain pollution. The School District of Lancaster has included "green-roof" design into its school renovations.

In Lititz, efforts to reduce sediment runoff showed a 47 percent improvement between 2004 and 2012, according to a report given to Lititz Borough Council last year.

Reducing sediment, nitrogen and phosphorus is key to generating the growth of underwater grasses.

In fact, the decline in bay grasses is what led to the D-plus grade. Had the grasses not experienced a 20 percent drop in recent years, the foundation indicated it would have given the bay's health a higher mark.

Polcies regulating runoff have not been warmly received by all groups, but the fact that oyster and blue crab populations are growing and that the bay is showing signs of regeneration suggest that the two-year "pollution diet" imposed upon businesses, sewage treatment plants, construction sites and farmers is having a positive effect.

The bay will never again be pristine, but it is cleaner today than it was four years ago, And the prospects are that, if current measures remain in place, it will be even cleaner two years from now.