In the late 1970s, offshore supply tugboats were in high demand and their success led to experimentation by the Canadian Coast Guard.

The results of the test proved positive and in 1983, the Canadian Coast Guard contracted Robert Allen Ltd of Vancouver to create a design based on this setup.

[4][5][6] Earl Grey is powered by four Deutz 4SA 9-cylinder diesel-electric engines driving two controllable pitch propellers that create 8,836 horsepower (6,589 kW).

[4][6] Samuel Risley is powered by four Wärtsilä Vasa 16V22 12-cylinder geared diesel-electric engines driving two controllable pitch propellers that create 6,595 kW (8,844 hp).

The vessel has a capacity of 692 m3 (152,000 imp gal) of diesel fuel that gives Samuel Risley a range of 16,700 nautical miles (30,900 km) at 12 knots (22 km/h).

Earl Grey and CCGS Mary Hichens recovered wreckage from the plane, while transferring human remains to HMCS Preserver.

[12] In early 2015, Samuel Risley worked alongside other icebreakers to rescue many commercial ships that had become stuck in the ice on the Great Lakes.

[16] Samuel Risley deployed to the Arctic Ocean during the 2018 sailing season, taking part in the resupply mission to the United States Air Force base at Thule, Greenland.