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Eldon

On Hamma Hamma Bay, was a brisk town in the early 1900’s, when logging operations on the upper Hamma Hamma River were extensive. During the 1930s, a CCC side camp was stationed near the river. Weathered buildings along the bay and an abandoned railroad fill are reminders of this vanished activity. Constructed in 1924, two identical concrete tied-arch bridges that span the South Hamma Hamma River and North Hamma River on either side of Eldon are listed in the National Register for the innovative engineering employed at the time of construction.

North of Eldon US 101 swings across the Hamma Hamma River and again plunges into dense forests broken occasionally by small clearings and open spaces, which afford panoramic views of Hood Canal and the wooded shores beyond. Traces of development remain, with the Hamma Hamma Oyster Co. on the canal side and Camp Hamma Hamma against the mountain.

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South and North Hamma Hamma River Bridges

Two identical single-spanned concrete tied arches were constructed by the Colonial Building Company in 1924 over the North Hamma Hamma and the South Hamma Hamma River. Spaced a few hundred feet apart, their arched forms frame a pathway of trees creating the momentary illusion of a serene, sheltered boulevard along Highway 101 on the Olympic Peninsula. Each bridge is 154 feet long, and consists of a 150 foot three hinged arch with a rise of 30 feet. Unlike the flat truss or girder, the arch exerts a horizontal thrust on the skewbacks. In most arches, massive abutments and foundations are necessary to resist the horizontal thrust. However, in the tied arch, the horizontal thrust is resisted by longitudinal ties which extend between the hinged springing points. In the Hamma Hamma River Bridges, the deck slab itself, which is hung by suspenders from the pair of arch ribs, acts as a tie. Since the arch is in compression, the deck slat, is subject to a tensile stress. The double function of the deck slab was an economical solution, and it eliminated the need of massive abutments. Originally, six reinforced concrete struts connected the Hamma Hamma River arches above the roadway. However, two struts were removed from each bridge to increase the vertical clearance of the spans. The North and South Hamma Hanuna River Bridges are two of five concrete tied arches within the State. Of the five bridges, their arch spans are the longest. They are a rare concrete arch form.