Gravelly Shoal Light
Undated USCG photo
|Location||Saginaw Bay, Michigan|
|Year first constructed||1939|
|Year first lit||1939|
|Foundation||50-foot (15 m) diameter concrete pier|
|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|
|Range||9.6 nautical miles; 18 kilometres (11 mi)|
|Characteristic||red flash every 6 seconds|
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.
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.
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).
The National Data Buoy Center lists the Site Elevation as 588 feet (179.2 m) above sea level; an automatic readout for wind, waves and weather is operated there.
The National Weather Service operates an automated weather observing station at the lighthouse.
An added large steel tower atop the light is a radio beacon. The 1953 Coast Guard Light List indicates that the signal transmitted at 296 kHz, send forth a group of half-second dashes for 15.5 seconds, followed by 14½ seconds of silence. As of 2001, both the light and radio beacon served as active navigational aids.
A good passing view of the light can be had while riding the ferry from Au Gres to Charity Island, which is 10 miles (16 km) to the east in the middle of Saginaw Bay. Tours of Charity Island (and even dinner cruises) are available, which can include the privately owned, rebuilt Charity Island Light lightkeeper's house. They are available from Charity Island Transport, Inc. in Au Gres, Michigan on the mainland, south of Tawas.
It is also possible to take a telephoto shot from shore.
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