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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 4 of 12 (fine alluvium and glacial till) at Boring Nos. 11, 12, and 19. Boring Nos. 19 through 22 terminated in organic clay at depths of 16 feet below grade. 5.3.1 Critical Subgrade Zone The limiting soils concerning pavement support in the upper 3 feet of subgrade below the pavement generally consisted of sandy lean clay and clayey sand with general AASHTO Classification designations of A-2-6, A-6, and A-7-6. These classifications are indicative of frost susceptible soils, which can heave when frozen, and also lose strength upon thawing in the spring. This type of subgrade is susceptible to pavement damage from heavy trucks during periods when the subgrade is coming out of thawing, or when in a saturated condition. Enforcement of load restrictions in the spring for these types of pavement is important; however, some vehicles such as garbage trucks regularly travel over streets even in the load restriction period. 5.4 Groundwater We measured groundwater in 3 of the borings at the time of drilling. Groundwater was not observed in the other 21 borings performed for the project. Groundwater was observed at Boring Nos. 4, 11, and 20 at depths of 8.6 feet, 14 feet, and 13 feet below grade, respectively. The majority of the site soils are relatively slow draining clayey soils and an extended period of time would be required for ground water to appear and stabilize in an open borehole; therefore, the absence of ground water in our borings should not be taken to mean that ground water would not be encountered in an excavation. Perched groundwater levels can occur in sand and clay matrixes and groundwater may be encountered if deeper excavations are performed at the site. Long-term groundwater level measurements were not part of our scope of services on this project. Groundwater levels fluctuate due to varying seasonal and annual rainfall and snowmelt amounts, as well as other factors. 5.5 Engineering Review of Soil Properties Typically, the granular materials encountered have moderate to high strength, unless they become disturbed. In general, the less silty granular materials possess good to moderate drainage characteristics, while the silty sands have fair drainage characteristics. The clayey sand and lean clay soils have poor drainage characteristics. The silty sands have at least a moderate