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<br />7 <br /> <br />topsoil, organic soils or any soils that are black in color for pipe support or for fill or backfill <br />below roadways. <br /> <br />Laboratory moisture content of the clayey soils indicated that the soils were likely above their <br />assumed optimum soil moisture content. Clayey soils that will be reused as fill or backfill will <br />likely need to moisture conditioned (dried) to meet the recommend compaction levels. <br />Summer months are typically more favorable for drying wet clays. <br /> <br />We recommend bedding material be thoroughly compacted around the pipes. We recommend <br />that engineered fill placed to establish pavement grades be compacted to a minimum of 95 <br />percent of its standard Proctor density (ASTM D 698), the exception being within 3 feet of the <br />proposed pavement subgrade, where 100 percent of standard Proctor density is required. In <br />landscaped areas, if any, we recommend a minimum compaction of 90 percent. <br /> <br />Granular fill classified as SP or SP-SM, if used, should be placed within 65 percent to 105 <br />percent of its optimum moisture content as determined by the standard Proctor. Other fill <br />soils should be placed within 3 percentage points above and 1 percentage point below its <br />optimum moisture content as determined by the standard Proctor. All fill should be placed <br />in thin lifts and be compacted with a large self-propelled vibratory compactor operating in <br />vibratory mode. <br /> <br />Fill and backfill placed on slopes must be “benched” into the underlying suitable soil to reduce <br />the potential for slip planes to develop between the fill and underlying soil. Likewise, any fill <br />placed for embankment construction should be “benched” into the existing roadway <br />embankment. We recommend “benching” or excavating into the slope at 5 feet vertical <br />intervals to key the fill into the slope. We recommend each bench be a minimum of 10 feet <br />wide. <br /> <br />Prior to placing/replacing the aggregate base (Class 5) we recommend compacting and/or <br />proof-rolling the subgrade soil to provide a more uniform surface and to identify soft, weak, <br />loose or unstable areas that may require additional subcuts or corrections. Backfill, if needed, <br />to attain pavement subgrade elevation can consist of any mineral soil provided it is free of <br />organic material or other deleterious materials. <br /> <br />4.4 Pavements <br /> <br />General The City of Orono may have standard plates that dictate pavement design. If so , we <br />recommend that the pavements be designed and constructed in accordance with the city <br />standard plates. The following paragraphs provide general pavement recommendations in <br />the absence of city standard plates. <br /> <br />Traffic & Street Section Based on the plan provide, the new street will provide access to about <br />6 single family residences. We assume the street will be used mostly by automobiles and light <br />truck but will also include some heaver single-unit trucks such as garbage trucks, school <br />busses, and delivery vans. Based on the assumed traffic types and traffic volumes we estimate <br />that the pavements will be subjected to Equivalent Single Axle Loads (SEAL’s) significantly <br />less than 50,000 over a 20-year design life. This value has not account for any future growth. <br /> <br />213