The cause of a May 1 rupture of the Mountain Valley Pipeline in Roanoke County, Virginia is still undetermined. The Pipeline and Hazardous Materials Safety Administration says the agency hasn’t received the results of a metallurgical analysis and that there's no timeline for completion of an analysis being performed by DNV. Meanwhile, erosion issues have persisted for the 303-mile, 42-inch-diameter pipeline, whose lead developer has been Washing…