History
As one approaches the Delaware River from the south 14
Foot Bank Lighthouse is the second Delaware Bay
lighthouse to be seen, Brandywine Shoal lighthouse being
the most southerly.
Fourteen Foot Bank Lighthouse is named for the 14 feet
of water that cover this shoal bank. The shoal is nearly
6,000 feet long and 1,300 feet wide and many ships lie
beneath the sea in and around the shoal. Since 1876 the
shoal had been lit by a lightship during most of the
year, but due to the ice floe danger, it could not
remain on station during the winter months when it was
most needed.
The Lighthouse Board decided to erect a lighthouse on
the location. Many plans were submitted to the Board,
but the Board finally adopted the proposal of its chief
engineer, Major D. P. Heap, in 1883.
Heap proposed to build a lighthouse with a caisson
construction of a cast-iron cylinder 73 feet high with a
35 foot diameter, composed of 1.50" thick iron plates
each 6 feet high and 6 inches wide with both horizontal
and vertical flanges that would be bolted together to
assure a water-tight fit.
The government supplied the materials and requested
bids from contractors to assemble and sink the caisson.
The firm of Messrs. Anderson and Barr, a New York civil
engineering firm was awarded the contract. They proposed
to sink the caisson by means of a pneumatic process.
A square wooden working caisson was constructed on the
shore. It measured 40 foot square, 5 feet thick, with
walls 7 feet high around all four sides. The water-tight
structure was roofed on top and open at the bottom. The
bottom was to act as a cutting edge when resting on the
bottom of the bay. An air shaft was constructed in the
center of the wooden caisson, and provided the means for
entry and exit from the working chamber. The permanent
caisson of iron was built atop this working caisson
initially to a height of 18 feet.
When completed the composite structure was towed into
position on the shoal. A layer of concrete was put on
top of the wooden caisson and this formed the floor of
the permanent structure. Both units were then sunk to
the bottom by allowing water to enter through 6 inch
valves.
The box and the cylinder descended slowly to the bottom
of the bay, but unfortunately came to rest listing
12 . The top of the cylinder's upper edge was just
inches from the surface of the bay, an increase of tide
or wind conditions would drive the sea over the top thus
repeating a disaster that occurred during the
construction of the Rothersand Shoal Lighthouse.
The engineers quickly averted disaster by adding
additional sections of cylinder wall and filling the
cylinder partially with rip-rap hastily procured on
shore and rushed to the site by tugboat. The cylinder
finally righted itself, the extra weight driving the
edge of the wooden caisson deep into the bed of the bay.
More sections of wall were bolted onto the iron caisson
and the water was pumped out from below. The wall of the
iron caisson was finally some 20 feet above mean high
water.
It became necessary then only to increase the length of
the air shaft at the same rate at which the men dug into
the bay bottom, and fill the upper iron caisson
periodically with concrete to drive the wooden caisson
to the required 33 feet into the bottom of the bay.
Eight men worked eight hour shifts around the clock
removing about two inches of bottom an hour. On August
18, 1855, the required depth had been reached, just one
month after digging and concreting had begun.
While the digging and sinking operation was going on,
another group was busily engaged in the dumping of some
6,000 tons of rip-rap around the base of the caisson to
secure it from movements of the current as well as to
protect it from ice floe and shipping.
The iron caisson was then flattened, the air shaft
filled in, and a quaint, picturesque three-story gabled
house built upon it. The lighthouse cost $125,000 to
build. It is 59 feet to the focal plane of the light.
The lighthouse is still in operation and described on
current nautical charts as "GP Fl (2) 20 sec. 50 ft. 12
m Horn," which indicated to mariners that the light is a
group flashing light (2), every 20 seconds on a 59 foot
tower, visible 12 nautical miles at sea and that the
station is equipped with a fog horn.
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