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Lino Lakes 81st Street November 4, 2023 <br />Project #: 22538.23.MNT Page - 5 <br />________________________________________________________________________________________________________ <br /> M I N N E S O T A IOWA W I S C O N S I N <br />D.3. Trench Bottom Stability <br />Depending upon location and depth, the utilities are expected to bear primarily on clean sands. These <br />materials are considered suitable for support of pipes. If soft and unstable conditions are encountered, <br />we recommend placing bedding of coarse sand or gravel at the base of the trenches to provide a more <br />stable bottom for crews laying the pipes. Such conditions are not expected. <br />In order to reduce the potential for point loads on the pipes, we recommend removing any cobbles or <br />boulders to a depth of at least 6 to 8 inches from around pipes and replacing those materials with clean <br />sand or gravel that can more readily conform to the pipes. Again, cobbles and boulders were not observed <br />during drilling. <br />D.4. Fill Placement and Compaction <br />The sands encountered are considered suitable for use as backfill above utilities and supporting the <br />pavements. Soils placed as backfill below paved areas should be compacted to 100% of their maximum <br />standard Proctor density (ASTM D 698) in the upper 3 fe et, and to at least 95% below. In green areas, <br />90% compaction is normally adequate. <br />E. Pavement Recommendations <br />E.1. Stripping and Grading <br />We recommend removing the existing asphalt, aggregate base, and topsoil or other unsuitable soil from <br />within 3 feet of the proposed pavement section subgrade before placing the new pavement material <br />sections. It may be possible to reclaim and reuse the existing asphalt and aggregate for use as part of the <br />new pavement’s aggregate base, provided it meets MnDOT specifications. <br />After the removals, utility construction, and grading, the near-surface soils are expected to primarily <br />consists of clean sands. We recommend scarifying and compacting all near-surface soils in order to even <br />out any localized discontinuities in the subgrade materials and to provide a more gradational transition <br />between differing materials. This action is intended to limit differential frost heave and provide more <br />uniform pavement support. <br />Subgrades should be test rolled using a tandem axle truck. Any soft areas detected should be scarified, <br />dried, and recompacted. If time constraints prohibit drying, soil corrections, extra aggregate base, breaker <br />run, sand subbase, and/or geotextiles may be necessary for stabilization. <br />E.2. Preliminary Pavement Design <br />As mentioned earlier, subgrade soils are expected to consist primarily of clean sands. The effective <br />Hveem-stabilometer R-values for dominant sands would be expected to range from 50 to 70. We <br />recommend using a value of 50 for pavement design. <br />In the absence of traffic loading, we recommend a pavement section consisting of at least 3 inches of <br />asphalt and 6 inches of aggregate base. As noted before, the existing pavements could possibly be milled