A barge being towed by two towing vessels, the 65-foot Shannan C (Imo 8991724) and 22 meter long Portier I, allided with the Highway 90 Bridge over Chef Menteur Pass which connects Lake Pontchartrain to Lake Borgne near New Orleans, Louisiana.  The barge caused considerable damage to the bridge forcing officials to close the bridge to vehicle and marine traffic.   Estimates place the cost of damage near $100,000.    The Coast Guard is conducting an investigation into the incident.