The states making up the Chesapeake Bay watershed yesterday pledged to cut back runoff of nutrients and sediments into the bay so sharply that it will be removed from the federal “dirty water” list within 10 years. Maryland Gov. Parris Glendening (D) said that if the states reach the goal to surpass Clean Water Act standards, the Chesapeake “would be one of the largest bodies of water to ever show such an improvement.” But first, the hard work. Maryland, Pennsylvania, Virginia, the District of Columbia, the U.S. EPA, and the Chesapeake Bay Commission — which together form the Chesapeake Executive Council — agreed to restore 25,000 acres of wetlands and increase oyster populations tenfold by 2010. But a major goal remains up in the air. Five of the parties say it is essential that the states pledge to cut the annual loss of forests and other open space by 30 percent, but much to their disgust, Virginia is refusing to endorse that goal, arguing that land use is the purview of local governments and it cannot pledge to meet a specific numerical goal.