Given the very serious implications of Section 104(f) through Rock Creek Park, it's not surprising. And the state has a history of not following through on its park-related promises (witness the ICC).
What were the problems on the ICC?
Building the 2-mile Beltway segment through Rock Creek Park in Montgomery County, Maryland, most likely would have been impossible to build after enactment of the 1969 National Environmental Policy Act (NEPA), with its stringent federal environmental standards. Unfortunately, these kind of highway designs were commonplace all over the U.S. before NEPA, as the rationale was that it enabled urban and suburban highway segments to be built in places that did not displace houses and businesses. Engineers and planners routinely routed highways through areas which would provide the least resistance, and in practical terms that often meant sites that were occupied by minorities or the poor, or riverfronts or stream valleys or parks that housed few or no residents or business owners to complain.
The Maryland segment of the beltway was planned to follow open corridors as much as possible, to avoid heavily developed areas where possible, and in Prince Georges County it was possible to avoid heavily developed areas, but in Montgomery County that was not possible in every area as there were some segments with heavy impacts to developed areas with many homes and businesses acquired for the highway right-of-way; and a 2-mile beltway segment was built through Rock Creek Park over the objections of state and federal public park agencies, something that probably would not have been possible after Congressional enactment of the 1969 National Environmental Policy Act (NEPA), as one of the many things that NEPA did was to make it virtually impossible to build a highway through major public parkland. The alternative to the Rock Creek Park alignment would have been to locate the highway on a straighter alignment about a mile to the north, which would have been advantageous from a traffic engineering standpoint, but which was effectively politically impossible as it would have passed through heavily developed and very affluent residential sections of Bethesda. After NEPA, it is quite possible that it would not have been possible to find a feasible location build that segment of the Beltway if it had not already been built, and that would have left a missing link in the Beltway between MD-355 Wisconsin Avenue and MD-97 Georgia Avenue.
http://www.capital-beltway.com/Capital-Beltway-History.html