In December 1967, Lavelle was assigned to the Defense Communications Planning Group located at the United States Naval Observatory, Washington, D.C., where he served as the Deputy Director for Forces. In February 1968 he assumed duties as the director of the Defense Communications Planning Group. The appointment was made by Secretary of the Air Force Harold Brown and carried with it promotion to Lieutenant General. The Defense Communications Planning Group (DCPG) ran the secret development of seismic and acoustic sensors to detect truck traffic on the roads that made up the Ho Chi Minh Trail in Laos. It was also known as the Igloo White Project. The idea was the brainchild of the Scientific Advisory Board and embraced by Secretary of Defense Robert S. McNamara, who made it a priority development under the direct control of Brown and using primarily Air Force funds to budget it.