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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />November 29, 2006 <br />Project 06-507B <br />2007 Street Reconstruction <br />Deerfield 3rd Addition Improvements <br />Elk River, Minnesota <br /> <br />We recommend that any imported fill and utility trench backfill material consist of <br />mineral soils meeting the requirements specified below. No organic soils, roots, stumps, <br /> <br />logs, brush, etc. should be used as structural fill below any utility structure or pavement <br />section. We recommend that all fill and utility trench backfill material be free of soft, wet <br />or frozen soils, highly expansive soils, rubble, debris and rocks in excess of 6 inches in <br />diameter. The fill and utility trench backfill material should be as uniform as possible <br />both in composition and moisture content. <br /> <br />We recommend that all fill and utility trench backfill material be placed in 12-inchloose <br />lifts and compacted to a minimum of 95% of standard proctor maximum density (ASlM <br /> <br />----- ...--...-.---------. -- ------.-------.-------...-.---.-...----.--- --------------.---- -------.- - -.---- ---" <br /> <br />D698). Any fill placed in the top 3 feet of the road subgrade should be compacted to at <br />least 100% of standard proctor maximum density. All fill and utility trench backfill <br />material should be compacted at a moisture content within plus or minus 2% of the <br />optimum moisture as determined by a standard proctor. We recommend compaction tests <br />be taken at a minimum rate of one test per two feet of fill per 200 linear feet of the utility <br />trench backfill, roadway sub grade, and aggregate base material. <br /> <br />E. Pavement Recommendations <br /> <br />The majority of the expected subgrade soils in the Deerfield 3rd Addition consist of silty <br />sands (SM) and silty- clayey sands (Se-SM). These soils are classified as A-2-4 soils in <br />accordance with the American Association of State Highway Transportation Officials <br />(AASHTO) classification system. A-2-4 soils are rated as fair material for use as <br />roadway subgrade material. Without benefit of a laboratory R-value determination and <br />based on Mn/DOT guidelines, an R-value of30 can be assumed for the onsite soils. <br /> <br />Page 7 <br />