Dartford Tunnel East – London, England

The tunnel, which carries traffic on the M25 London Orbital Motorway under the Thames River, started leaking in several places. Total water make was 350 liters per minute. After several unsuccessful attempts by others to adequately seal the water, Sovereign mobilized in September 1989 to perform a trial sealing exercise on the worst 100-meter section. Within 6 shifts, the total water make in the tunnel was reduced to an acceptable rate of 125 liters per minute. An August 1992 inspection certified that no further leaks had developed in the 100-meter SCEM66 trial area.