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}} The Yamhill River lock and dam was completed in 1900. It was built near Lafayette, Oregon to allow better river transport on the Yamhill River from Dayton to McMinnville, Oregon. While the Corps of Engineers had recommended against construction of the lock, it was built anyway, largely as a result of political effort by the backers of the project. For almost forty years prior to the lock construction there had been efforts made to construct a lock and dam on the Yamhill River.〔 The lock was a single lift chamber 210 feet long and 40 feet wide, located on the west side of the river. The dam extended from the east bank of the river to the eastern lock wall, and when the lock gates were shut, acted to back up the Yamhill river and raise the water level sufficiently to allow ready steamboat navigation to McMinnville during the summer dry season. During the winter however the lock and dam were more of an obstruction than an navigational aid, as they were frequently overtopped by freshets and floods, sometimes as high or higher than twenty feet above the lock walls. The lock ceased to be used in any significant way soon after it was built. There was an upsurge in use of the river during the 1930s and 1940s primary for transport of logs. The lock continued in operation until the 1950s when the U.S. government concluded that the little amount of traffic on the river no longer justified their expense. The lock and dam were then turned over to Yamhill County. The county lacked the funds to maintain or restore the lock, and the dam, having been viewed as a barrier to spawning salmon was eventually destroyed with use of explosives. The lock walls remain however to this day. The lock keeper’s residence, built at the same time, and now in private hands, also remains. A county park is nearby from which the lock structure can be viewed. Some other remains of the work, such as pilings, are also visible at low water. While not particular remarkable as an engineering project, the lock was one of only three dock and dam projects commenced in Oregon and indeed in all of the Pacific Coast states by the United States government during the 19th century. The lock and dam are also representative of the results of local pressure for expenditure of funds from the national government for works of a local nature.〔 A substantial portion of the project remains visible to this day, and has been said to be “one of the last tangible remnants in the Upper Willamette Valley of a time when river navigation played an important role in transporting freight and passengers.”〔 The lock is sometimes referred to as the Lafayette Lock.〔 The Lafayette Locks Park, maintained by Yamhill County, Oregon now occupies the site of the old lock and dam.〔 〕 ==Location== The lock was (and is) located about one mile downriver from the town of Lafayette, Oregon and about five miles upriver from the confluence of the Yamhill and the Willamette Rivers.〔 The fall of the Yamhill river between McMinnville and the lock was 13 feet.〔 The river in its natural state had a stretch of rapids running from Lafayette, which was originally called Yamhill Falls, downriver to the lock site, over which the river fell nine feet.〔 The source of the Yamhill River was the Coast Range in Oregon. The river flows to the east about 45 miles, to a point about 40 miles upriver from Portland, Oregon, where it joins the Willamette River. Light-draft steamboats routinely ran to Dayton, about five miles above the river’s mouth. The town of Lafayette was about 8 miles up from the river mouth.〔 At Lafayette there was a stretch of rapids over which the river fell 8.8 feet in one mile. From the foot of the rapids to the mouth of the river the fall was just one foot. High water in the Yamhill River, or a rise of 10 feet in the Willamette River would submerge the rapids.〔 From Lafayette the river ran about 9 miles to McMinnville, the seat of Yamhill County, a prosperous agricultural region. This stretch of the river was from 40 to 100 feet wide, and obstructed with snags and overhanging trees. The snags were particularly bad for a stretch running from McMinnville three miles down river. If the snags and overhanging trees were removed, steamboats drawing 2.5 to 3.0 feet of water could proceed to McMinnville. However, the season in which boats could pass over the rapids was limited to about five months a year.〔 In December 1892 there had been no preparation at all for use of the river to ship products by water. No roads led to the river, and there were no storehouses on the banks. There seemed to be very little interest taken in the recent clearance of the river. One steamer regularly the whole year between Portland and Dayton, and made a good business. This steamer could have extended its route to McMinnville if there had been sufficient business on the river to make it worthwhile.〔 In 1892, a rail line crossed the Yamhill river at McMinnville and at LaFayette, which were only five miles apart by wagon road. Lafayette and Dayton were only two miles apart by road, and all of the country was flat.〔 In 1910, the Yamhill river was described as “a limpid stream of shallows and deeps in Summer, a brawling torrent in Winter.” In 1874, the Yamhill was examined by the engineering department of the U.S. army, which found that the river would vary from a shallow chain of pools in the summer to a “river of great power and strength” whose waterlines along the banks showed a rise, sometimes, of over 60 feet during winter and spring floods. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Yamhill River lock and dam」の詳細全文を読む スポンサード リンク
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