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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 5 of 12 susceptibility to frost heaving and freeze thaw weakening. The cohesive soils can have quite variable strength and stability properties, depending on the moisture content. The buried organic soils have low strength and stability properties. The cohesive soils and organic soils are considered to be moderately to highly susceptible to frost heaving and freeze thaw weakening. 6.0 RECOMMENDATIONS 6.1 Approach Discussion Based on the conditions encountered at the boring locations, the upper subgrade soils will consist of clayey sand and silty sand with varying amounts of gravel. Future pavement performance (from a frost standpoint) would be similar to that experienced in the past. Consideration could be given to incorporating a sand subbase into the pavement design. Further discussion on this topic can be found in later sections. The existing pavement and aggregate base (where present) could be reclaimed for use as aggregate base for the reconstruction project. However, the thicknesses varied greatly throughout the project, and we recommend performing additional investigation, such as Ground Penetrating Radar, by the project contractor to better plan depth adjustments during reclaim operations. Several borings encountered peat and organic clay. Our standard penetration resistance values in the organic soils indicated that they were generally in a very soft to soft condition, and that continued long-term settlement of the road embankment will occur. We expect the roadway will continue to experience settlement in areas where there are buried organic soils present. The organic soils are compressing from the weight of the embankment fill placed to support the roadway; this may cause longitudinal cracking to develop in the future. To reduce future longitudinal cracking, consideration should be given to placing a geogrid in the road embankment as part of the resurfacing project in the area of the organic soils. The geogrid will not reduce or stop the settlement; this will strengthen the fill embankment to provide a more uniform bridging action over the buried organic soils. If you wish to consider this option, a detailed reinforcement design should be performed. A possible drawback of using a geogrid is that it would be cut if an excavation is performed for below grade work.