This project focused on the design of two stream crossings: Mine Creek and the Little Washougal River. For the Little Washougal crossing, based on safety and economic analysis of the available options, the prestressed concrete bridge design is our recommendation. It exceeds all safety and load requirments, and is the least expensive option when the lifespan of the structure is taken into account. For an in depth analysis of the different options, see the Bridge Design section of this report. The Mine Creek crossing was complicated due to some debate over the presence of fish in Mine Creek at the point of our crossing. Therefore, we have produced one design that allows fish passage, and one that does not. If no fish passage is required, we recommend a 60 inch diameter culvert. If fish passage is required, we recommend a 65 inch X 40 inch pipe arch. In either case, we recommend 1:1 fill slopes at the crossing. The culvert or pipe arch will be 68 feet long due to the 28 foot road width required for curve widening and the 20 feet of fill necessary at the centerline. To view our analysis of the Mine Creek crossing, see the Culvert Design section of this report.
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