Map of bedrock-surface topography in parts of the Paterson and Pompton Plains quadrangles, New Jersey

A seismic-refraction survey was done by the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers (ACOE), to define the altitudes of the bedrock surface beneath part of a proposed water diversion tunnel to control periodic heavy flooding along parts of the Passaic and Pompton Rivers in northeastern New Jersey. The altitude of the top of the tunnel is planned to be approximately at sea level. The ACOE would like to have a minimum of 40 ft of bedrock above the top of the tunnel for construction and engineering purposes. The results of the study show that the bedrock ranges in altitude from 40 to 140 ft above sea level, and that there is a northeast trending bedrock valley that overlies the proposed tunnel alignment. (USGS)