For more than 270 years, the Merrimack Village Dam in New Hampshire helped power saw mills, gristmills, a shoe factory and provided water for a chemical factory. No longer powering industry and scheduled for demolition, the dam has one last role to play ? that of movie star. Beginning this week, NOAA, in partnership with the Conservation Law Foundation, will capture live on camera the removal of the dam, opening up 14 miles of the Souhegan River from Milford to Merrimack, N.H., providing extensive habitat for river herring, Atlantic salmon, American shad and American eel.