Journal of the Association of Engineering Societies (1881)
Association of Engineering Societies (U.S.) · New York, [etc.] Board of Managers · leaf 234
their bottoms are the hard clay underlying all this region, in which it is difficult for the peren- nials to get a start, comparatively little difficulty will appear from this cause. But as this clay loosens under frost action and the natural erosive action of the water and is carried away by it,… … Sand Hill River Ditch, Polk County. Thirteen Miles Long. Exerts a Beneficial Influence over at least 50,000 Acres. Cost $24,000. It may require a half dozen years for this tendency to develop to any apprehensive stage in the majority of the ditches which have a sufficient slope, i.e., from 3 to 5…
Engineering
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