Laserfiche WebLink
<br />e <br /> <br />~ <br /> <br />, <br /> <br />e <br /> <br />. <br /> <br />" <br /> <br />e <br /> <br />EM 1110-2-1913 <br />31 Mar 78 <br /> <br />CHAPTER 4 <br /> <br />BORROW AREAS <br /> <br />4-1. General. In the past borrow areas were selected largely on the <br />basis of material types and quantities and haul distances. Today, <br />borrow areas receive much more attention and must be carefully planned <br />and designed, because of considerations such as environmental aspects, <br />increasing land values, and greater recognition of the effects of borrow <br />areas with respect to underseepage, uplift pressures, overall levee <br />stability, and erosion. The following paragraphs discuss some factors <br />involved in locating and using borrow areas. <br /> <br />4-2. Available Borrow Material. <br /> <br />a. Material TYPe. Almost any soil is suitable for constructing <br />levees, except very wet, fine-grained soils or highly organic soils. In <br />some cases, though, even these soils must be used. Accessibility and <br />proximity are often controlling factors in selecting borrow areas, <br />although the availability of better borrow materials involving somewhat <br />longer haul distances may sometimes lead to the rejection of poorer but <br />more readily available borrow. <br /> <br />b. Natural Water Content. Where compacted levees are planned, it <br />is necessary to obtain borrow material with water content low enough to <br />allow placement and adequate compaction. The cost of drying borrow <br />material to suitable water contents can be very high, in many cases ex- <br />ceeding the cost of longer haul distances to obtain material that can be <br />placed without drying. Borrow soils undergo seasonal water content <br />variations; hence water content data should be based on samples obtained <br />from borrow areas in that season of the year when levee construction is <br />planned. Possible variation of water contents during the construction <br />season should also be considered. <br /> <br />4-3. General Layout. Generally, the most economical borrow scheme is <br />to establish pits parallel and adj~cent to the levee. If a levee is <br />adjacent to required channel excavation, levee construction can often <br />utilize material from channel excavation. Large centralized borrow <br />areas are normally established only for the construction of urban levees, <br />where adjacent borrow areas are unavailable. Long, shallow borrow areas <br />along the levee alignment are more suitable, not only because of the <br />s):lorter haul distance involved, but also because they better satisfy <br />environmental considerations. <br /> <br />4-1 <br />