The Gulf Intracoastal Waterway will be closed during week nights starting today running through May 13 at the point where the Army Corps of Engineers is building a major storm surge barrier.  The canal will be closed between 6 p.m. and 6 a.m..   Mariners also won't be able to use Bayou Bienvenue during this period, because another gate project has closed it.  The surge barrier is being built to protect New Orleans from hurricane surge coming from Lake Borgne.