A barge being used as part of a floating platform, broke free on the Potomac River near Washington, D.C. suffered some structural failure .   Reports state the barge’s 500 gallon fuel tank began to leak diesel fuel releasing some 50 gallons of fuel into the water.   The Coast Guard and local authorities responded and placed a boom around the barge to contain the spill.    A pollution response team has been dispatched to the scene.