west. A large emergent spit in the bay on the west side of the breach stabilized the west breach
bank. The final closure procedure took advantage of the spit by changing direction of the fill
abruptly to the north to connect the fill with the spit and allow for immediate closure of the
breach. The breach was closed by early October. The remainder of the fill was placed from west
to east and the final cross-section was completed in December of 1993.
Grays Harbor, Washington. Grays Harbor is located on the southwest Washington coast at the
mouth of the Chehalis River, about 45 miles north of the Columbia River mouth. The estuary is
enclosed on the ocean side by spits that are separated by a 2-mile-wide opening that forms the
natural harbor entrance. Two convergent rock jetties extend seaward from the spit points. The
jetties are part of the Grays Harbor Navigation Project, which is a federally constructed and
maintained navigation channel that allows deep-draft shipping.
Following construction of the south jetty, the shoreline on the bay side of the spit receded as a
result of inner bank erosion. Inner bank erosion is a common phenomenon at the landward
terminus of jetties on sandy shorelines and often creates a crescent shaped bay, as is the case at
Grays Harbor. Recession rates on the bay side of the spit at the Grays Harbor south jetty have
ranged from approximately 3 to 25 ft per year since 1946. Beginning in the late 1960s, the ocean
side of the spit also eroded with shoreline recessional rates ranging from 2 to 62 ft/year (Osborne
et al. 2003).
In December 1993, the persistent erosion on both the ocean and bay sides of the south spit at
Grays Harbor culminated in formation of a breach between the south jetty and the adjacent
beach. The breach widened rapidly, exposing the landward end of the jetty and eroding portions
of the adjacent state park. Within hours of breach formation, the width was estimated by visual
observation to be approximately 25 ft. Approximately one week later, aerial photographs show
the breach had widened to approximately 275 ft. The breach reached a maximum width of
approximately 540 ft before it was mechanically filled by the U.S. Army Engineer District,
Seattle, in the fall of 1994 (Wamsley et al. 2005).
The City of Westport became alarmed by the rapid growth of the breach and expressed concern
for further expansion of the breach, damage to water wells and a sewer treatment plant, and
consequences for the Grays Harbor navigation project as the breach continued to widen during
the winter storm season. In March 1994, the Seattle District was directed by the Department of
the Army to close the breach. In September 1994, the filling operation commenced. The breach
closure was considered a temporary measure to protect the Grays Harbor navigation project and
to alleviate local concerns.
The sand to fill the breach was dredged from the adjacent navigation channel. The channel was
dredged with two small hopper dredges and pumped to the breach fill site with a 2000-hp,
24-inch booster pump.
Problems were encountered because the booster pump was
underpowered. The filling operation began pumping coarse material, but had to switch to a finer
source material because the coarse sand could not be efficiently pumped. As a result, the
majority of the fill was constructed with finer-grained material. Filling with finer-grained
material slowed the operation, as it did not accumulate as fast as the coarse material.
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