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, �� Hennepin County AET Project No. OS-06764 May 24, 2016 Page 3 of 5 • Adult Correctional Facilitv The soil boring encountered fill that extended to a depth of approximately 6 %z feet. The fill consisted mostly of lean clay with gravel to a depth of 2 '/2 feet then lean clay with sand to a depth of 5 feet, sandy lean clay with a trace of gravel to a depth of 6 feet and clayey sand to a depth of approximately 6 'h feet. The boring terminated at a depth of 7 feet in sand that was fine to medium grained. It was not possible to determine if the sand was natural soil or fill. Helical Anchor Analysis We completed a dynamic cone penetrometer (DCP) test at a depth of 6 feet in each of the borings. Based on a correlation to DCP blows, we estimated the standard penetration resistance (N-value) at the DCP locations. Using the estimated N-value, we determined the uplift resistance of the soil with installation of a 4-inch diameter helical anchor. Our analysis indicates that adequate capacity is available to resist pullout from a 990-pound force from the guy wires. Our analysis includes a minimum factor of safety of two. The test location at the Adult Correctional Facility encountered uncontrolled fill. Uncontrolled fill is fill that appears to have been placed without regard to consistency or compaction effort. Consequently, inadequate bearing capacity may occur at some of the anchor locations because of the variability in the condition of the fill. As a result, deeper embedment of the anchors may be required at this site. The capacity of the anchor will need to be verified at the time of placement by measuring the torque required to install it. Deadman Anchor Anal.� We understand that concrete deadman anchors may be utilized at some of the towers. The size and installation of the deadmen is specified in the Campbell Instruction Manual. For a deadman anchor buried with compacted backfill and its top at grade (i.e. no soil overburden on the anchor), we recommend assuming the resistance to uplift is equal to the weight of the concrete in the anchor. Backfill around the deadman anchor should be compacted to a minimum of 95 percent of its maximum dry density based on the standard Proctor test (ASTM International, Specification D698). For wind uplift, which is a transient load, we recommend using a minimum factor of safety of 1.5 for the ratio between the calculated uplift resistance and the design uplift loads. For a 2'x 2' x 2' deadman (as specified in the Campbell Instruction Manual), the weight would be approximately 1,200 pounds which is 1.2 times the design uplift load. To achieve a 1.5 factor of safety, a minimum 27" x 27" x 27" deadman should be used. Frost Heave The soils present on the five sites have a moderate to high frost heave potential. If lenses of silt are present within the soil profile, about 1 to 3 inches of frost heave may occur. Frost penetration in clay soils would be approximately 4 feet during an average winter, and 5 feet during a severe winter. Comparable frost penetration for sand soils would be about 6 feet during an average winter, and 7 feet during a severe winter. These frost penetration depths assume there is no snow cover providing insulation to the underlying ground.