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Show MIHMI GIVES KSTIIIS State Engineer Discusses Feasibility of Plans for Better "Swamp Roads." By GEORGE, W. COOLEY, State Engineer of Minnesota. Road superintendents sometimes fail to provido lio elaborate drainage necessary to obtain a proper foundation, because expensive drainage work reduces the funds available for surfacing. Tills applies ap-plies particularly to the great mileage of main rural roads on which there is an Insistent demand by ' road users tor surfacing, sur-facing, with impatience at any delay made to provide proper foundations. In u ml ev eloped - swa mp count ry tho most permanent work is obtained by building the roadway embankment of material ma-terial obtained by d red gins a ditch on ,lho upstream side of the road, with an auxiliary road ditch on the other side. Tho top soil from the ditches is first spread over the roadway and the dredge then excavates enough firm material to provido a substantial foundation when deposited de-posited on the top soil. The ditches are dug with practically vertical sides, in or-' or-' der to obtain the largest amount of firm j material, usually found at the bottom. ! The ditches must he of sufficient size to ' I provide the necessary drainage after they! have beoomo contracted by the breaking i 'down of the slopes. The low points in the 1 j ditch, excavated to eecure material, will become filled with sediment after a year or two. It sometimes appears extravagant to , make such large ditches on road work, but in new country lateral drainage is always carried to the road ditches and . should be provided In advance. There is not much difference in cost, however, between be-tween small ditches dug: by hand and a , large dredged ditch, on account of, th , lower cost of machine work per cubic yard. ; After drainage is secured, the important impor-tant work is to eliminate all vegetable and perishable matter and to build up the foundation uniformly. Dragging and planing plan-ing the subgrade as it is being- built will prevent the waviness of surface which develops occasionally after the completion comple-tion of a road, and it is advisable to specify spe-cify such work. Surfacing with gravel constitutes the final work on the main rural roads in many parts of the country, and a great deal of money Is wasted In not preparing the foundation properly for this surfacing. Until it Is compacted the coat of gravel acts like a sponge, holding1 water until the foundation becomes bo soft that traffic drives some of the gravel into the underlying material. This causes not oniy a loss of gravel, but also an uneven surface. A hard foundation for gravel can be obtained where the soil Is clay by spreading spread-ing two or three inches of sand or gravel over the clay, mixing them together, and rolling until a smooth surface is obtained. With a sandy subsoil, clay Is required to make a firai foundation. Where no clay is available, success has been attained by spreading about four inches of loose straw over the sand, but care must be exercised exer-cised to prevent the straw from becoming mixed with the gravel. Muskeg or pulverized pul-verized peat has also been used to ad- y vantage under like conditions. |