A plan to store hundreds of unused railroad cars on a line in the Adirondack Park is drawing fire from conservation groups and has Warren County officials checking a lease that controls the only way into the line.Chicago-based Iowa Pacific Holdings is preparing to have cars brought in for indefinite storage on the Saratoga and North Creek rail line that runs from a former iron mine in Tahawus in Essex County south to North Creek in Warren County.Iowa Pacific owns that section of the line, and leases the remainder, which runs south from North Creek to Saratoga Springs, in Saratoga County, from Warren County and the town of Corinth.