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Report of Geotechnical Exploration and Review Fox Street Improvements, Orono, Minnesota AMERICAN July 29, 2016 ENGINEERING Report No. 20-14448 TESTING, INC. Page 9 of 12 soils placed within the critical subgrade zone be compacted to a minimum of 100% of the standard maximum dry unit weight defined in ASTM: D698 (Standard Proctor test), at a water content 65% to 102% of the standard optimum water content. A reduced minimum compaction level of 95% of the standard maximum dry unit weight can be used below the critical subgrade zone. The sand subbase can be considered part of a composite subgrade; and the top of the subbase can be figured as the top of the 3-foot subgrade zone needing the 100% compaction level. However, the lower (dry) end of the water content range requirement does not need to apply to the sands. If additional aggregate base is required, the imported materials should meet the requirements of MnDOT 3138 100% crushed Class 5. The aggregate base should be tested for compaction using a MnDOT Dynamic Cone Penetrometer and meet the requirements of MnDOT Specification 2211.3.C3. 6.3.5 Tapers Uniformity of the soil below the roadway and separation from the water table are important factors in order to minimize frost heave and freeze thaw weakening related pavement distress. It is also important that any subgrade correction performed be tapered to minimize differential frost heave conditions. We recommend 10:1 (H:V) longitudinal tapers between the new streets and any connection to existing streets. 6.4 Existing Subgrade R-Value Based on the available information and our experience, we estimate the soils within the critical subgrade zone have an R-value of about 12. In the case where a 1-foot thick sand subbase is placed over the R=12 subgrade, an increased estimated R-value can be used in the pavement design. Based on values given in Section 5-3 of the MnDOT Pavement Manual, an equivalent design R-value of 25 can be used for the composite subgrade case. 6.5 Pavement Design The roadways are planned to be reconstructed to a 9-ton section. The most recent average annual daily traffic (AADT) data from MnDOT on Fox Street from Old Crystal Bay Road to Willow Drive is 1,400 (2010), Willow Drive to Brown Road is 1,000 (2015 data), and from Brown Road to Orono Orchard Road is 1,650 (2011 data). Using a growth factor of 2%, as previously requested by the City, and a truck percentage of 5.9, we estimate the AADT at a 20-