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_ . _ ~. • <br />4.9.3 Replacement <br />Prior [o topsoil replacement the spoil may be scarified to reduce excessive com- <br />paction a[ the spoil/soil interface if it is determined such conditions exist. <br />Alternatively, the topsoil may be replaced and then chisel plowed or ripped to <br />interrupt the spoil/soil interface. <br />While topsoil is being replaced in an area, it is probed with hand or power- <br />driven equipment to confirm the depth of replacement. If the depth is <4" than <br />planned in an area of >1/2 acre on cropland, i[ is restaked and more topsoil is <br />applied. Four inches is selected as a cutoff point because the scrapers are <br />incapable of handling layers less than [hat, i.e. it is the degree of depth <br />accuracy possible with a scraper. On rangeland, topsoil depths may range from <br />about six inches to as much as 14 inches. However, the average depth will be <br />approximately 10 inches on those areas disturbed after May 3, 1978. <br />Soil samples are selectively taken during topsoil depth probing to determine <br />nutrient levels in the replaced topsoil. Fertilization practices are based on <br />results obtained from analyses of these samples as well as plant response (see <br />Section 3.6.2.3 and 3.6.3.3 for more detail on fertilization practices). <br />All retopsoiled areas are seeded [he same year topsoil is replaced [o achieve as <br />rapid of vegetative stabilization as is possible. On occasions, small areas of <br />30-40 acres may be retopsoiled but not seeded in the same year as a result of <br />early snow fall. Generally retopsoiled areas are directly seeded to perennials. <br />Compaction on retopsoiled areas is usually mitigated by the freeze-[haw action <br />during winter. Areas where over compaction results from repeated equipment <br />travel or high soil moisture content are disced, plowed or ripped before seeding. <br />Erosion control measures such as contour furrows, small depressions, land <br />imprintings, etc. may be used to stabilize the topsoil and promote plant estab- <br />lishment (see Sections 3.6.2.5 and 3.6.3.6). <br />4-256 <br />