The Loudon WTP installed a new water line through a the extremely hard local rock. Drill-tech the tunneling contractor commented that this was the hardest rock they had ever tunneled through. The drill and blast tunnel was completed successfully followed by the installation of a new large diameter water line. The annular space between the water line and the new pipe was backfilled (tunnel grouted) with cellular concrete. Throop Cellular Concrete successfully placed approximately 750 CY of cellular grout. Grout was pumped approximately 500′ to the pit then down the length of the tunnel through slicklines.