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4.5 Pavement Areas <br /> After removing the existing pavement sections and backfilling the utilities, the final subgrade should have <br /> proper stability within three vertical feet of grading grade (grade which contacts the bottom of the <br /> aggregate base). This will generally be achieved in fill areas with proper compaction of embankment <br /> materials and in cut areas through proper subgrade preparation. The stability of the pavement subgrade <br /> should be evaluated using the test roll procedure (MnDOT 2111), except a fully loaded tandem axle dump <br /> truck or a full water truck should be utilized for the proof roll. If unstable soils are found under the test roll, <br /> these soils should be improved by means of scarification, moisture conditioning, and re-compaction, or by <br /> subcutting and replacement. If the on-site soils cannot be moisture conditioned and compacted as <br /> recommended, we recommend removing these unsuitable materials and replacing them with Select <br /> Grading Material (MnDOT 2105.1.A.6). We also recommend a proof-roll be performed again on the <br /> aggregate base just prior to placement of the bituminous pavement. <br /> Table 3 below presents the approximate pavement section thickness and subgrade soils that were <br /> encountered within the borings. <br /> Table 3: Existing Roadway Soil Boring Profiles <br /> Bituminous Aggregate <br /> Boring No. Thickness Base Subgrade Soils <br /> (inches) Thickness (Upper 4 feet) <br /> (inches) <br /> PB-1 4 7 Fill: Sand with silt <br /> PB-2 3 '/2 6 Fill: Silty sand and sand with silt <br /> PB-3 4 '/2 5 Sand and Sand with silt <br /> PB-4 4 '/2 7 Fill: Silty sand and sand with silt <br /> PB-5 4 7 Fill: Silty sand <br /> PB-6 4 3 Fill: Silty sand <br /> PB-7 5 4 Fill: Sand with silt <br /> PB-8 3 '/2 4 Fill: Lean clay <br /> PB-9 4 9 Fill: Sand with silt <br /> PB-10 3 7 Fill: Lean clay <br /> PB-11 3 '/2 7 Fill: Sand with silt <br /> PB-12 3 6 Fill: Sand with Silt <br /> PB-13 3 '/2 5 Fill: Sand with silt and silty sand <br /> Once the site has been prepared as recommended, we anticipate the subgrade will consist predominately <br /> sand with silt, sand and silty sand. The MnDOT Flexible Pavement Design Guidance Memo from January <br /> 2017, indicates soils such as those anticipated have an estimated R-value ranging from 20 to 70. It has <br /> been our experience that on projects with utility construction the final subgrades are generally a mix of <br /> soils excavated from the trenches. Also, lean clay was present in the subgrade at some locations, as <br /> such, we used an R-value of 20 for our design. <br /> Being traffic counts were not provided to us, we have assumed that the volume and distribution of <br /> vehicles using these roadways will have 20-year flexible Equivalent Single Axle Loads (ESAL's) less than <br /> 75,000. <br /> Geotechnical Report <br /> 2020 PMP Street Improvements <br /> Arden Hills,Minnesota <br /> WSB Project No.014297-000 Page 6 <br />