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RIVER CROSSING A 12 -acre single-family residential development in Mill Creek comprising 59 lots. The scope of work included clearing, grading, piping, surface improvements, and the construction of a 1,200 lineal foot causeway, including two waterway crossings. The project was constructed and substantially completed between April and October of 1999 at a cost of $3.3 million. Spotlight Environmentally sensitive construction techniques. Problem The 59-lot plat was designed on a tract of land adjacent to Mill Creek Center that would only be accessible by building a 1200’ long, 15’ high causeway across a wetland. The wetland contained two separate fish-bearing waterway crossings inside a temporary construction easement of only 35'. Solution To accomplish the work, North Creek water flows were diverted through a 140' long - 42" diameter steel casing. Bridge abutments and pier foundations were excavated below the original streambed, and a 100' span reinforced concrete bridge was constructed. The streambed was then reconstructed to preconstruction conditions. To tie the bridge into the levels above the wetland, a reinforced fill, 1100' long, was constructed utilizing Hilfiger walls. Results The causeway and bridge were constructed within the permitted stream crossing period without causing an environmental impact on the neighboring wetlands or fish-bearing habitat. Acknowledgements
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