Gravelly Shoal Light
Undated USCG photo
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| Location | Saginaw Bay, Michigan |
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| Coordinates | 44°1′6″N 83°32′14″W / 44.01833°N 83.53722°WCoordinates: 44°1′6″N 83°32′14″W / 44.01833°N 83.53722°W |
| Year first constructed | 1939 |
| Year first lit | 1939 |
| Foundation | 50-foot (15 m) diameter concrete pier |
| Construction | Steel-sided tower |
| Tower shape | Art Deco |
| Markings / pattern | white, gray scaffold atop |
| Height | Tower - 65 feet (20 m) |
| Focal height | Focal plane - 75 feet (23 m) |
| Current lens | 14.8-inch (375 mm) lens |
| Intensity | 15,000 candela |
| Range | 9.6 nautical miles; 18 kilometres (11 mi) |
| Characteristic | red flash every 6 seconds |
| Fog signal |
Every 30 seconds, operates year round. Radio beacon signal transmitted at 296 kHz, and emitted a group of 0.5 -second dashes for 15.5 seconds, followed by 14.5 seconds of silence. |
| ARLHS number | USA-340 |
| USCG number | 7-10540 |
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Every 30 seconds, operates year round.
Gravelly Shoals Light is an automated lighthouse that is an active aid to navigation on the shallow shoals extending southeast from Point Lookout on the western side of Saginaw Bay. The light is situated about 2.7 miles (4.3 km) offshore and was built to help guide boats through the deeper water between the southeast end of Gravelly Shoals and Charity Island. Architecturally this is considered to be Art Deco style.
As part of President Roosevelt's New Deal and its program to "Put America Back to Work" the new light tower was put up for bid, and built in 1939. It replaced an earlier gas-lit buoy. It also displaced the Charity Island Light, which was constructed in 1857, and operated until 1930.
Contemporary unmanned lights in the Art Deco style is the Indiana Harbor East Breakwater Light and its twin, the better known Port Washington Breakwater Light in Wisconsin.
When built according to its original specifications, the contractor warned that the foundation was inadequate to withstand the buildup of ice, and put in a bid for a contract modification. However, at the time jurisdiction over the light had just been transferred to the Coast Guard from the United States Lighthouse Service, and they chose to disregard the warning, and to accept the light as built. This resulted in substantial additional expense in due course, as the light had to be retrofitted.
This light is designed as an autonomous automated electrified station. It is under the control and maintenance of Coast Guard Station in Tawas City, Michigan. Ordinarily it displays a 15,000 candela 14.8 inches (375 mm) light powered by a 120 volt electric lamp. Power is supplied through a submarine cable, which crosses the shoal from Point Lookout. The 75-foot (23 m) focal plane makes its flash (1-second every 5 seconds) visible for 14 nautical miles; 26 kilometres (16 mi). It is supplemented by a standby 110 candela acetylene light with a half second flash every three seconds—which activates automatically if there is a power failure. In foggy weather, mariners are warned by twin compressed-air two-tone #3 diaphones, which operate on a 30-second cycle (3-second blast followed by 27 seconds of silence).
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Wikipedia