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Hennepin County � AET Project No. 09-00552 July 7, 2017 �'"' �"�`° '� �'' � �' � Pa e2of4 `'��M,i`��i�� g Analvsis Results Review of Tower Support Svstem The design of the tower structure and guy wire assembly (i.e. materials, connections, etc.) has been engineered by Campbell and was not included in our scope of services. Based on the requirements of ASCE-7 and the 2015 Minnesota Building Code, we estimate the maximum tension in the guy wires with a 110 mile per hour wind speed will be approximately 990 pounds. Our analysis took into account ice formation on the tower. Refer to the Screw Anchor Analysis section below for our opinion on the adequacy of the proposed screw anchor to resist this load. If concrete deadmen are used to anchor the tower and guy wires,the Campbell design installation procedures are appropriate with the exception of the size of the guy wire deadman. We recommend the concrete deadmen for the guy wire anchor be at least 27" x 27" x 27". Site Soils We completed a hand auger soil boring at the tower location. A Subsurface Boring Log is attached in the appendix. A summary of the soils encountered is provided below: • The soil boring encountered approximately 3 inches of dark brown silty sand topsoil. Fill consisting of sandy lean clay was encountered beneath the topsoil and extended to a depth of approximately 4.5 feet. The underlying soil consisted of a 3 foot layer of organic swamp deposit over stiff sandy lean clay that extended to the boring termination depth of approximately 9.5 feet. Screw Anchar Anal.� We completed dynamic cone penetrometer (DCP) testing in 6 inch increments from 4 to 9.5 feet of the boring. 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 screw anchor. Due to the uncontrolled nature of the fill soils in the upper region of our soil boring, our analysis indicates the capacity of the screw anchor to resist pullout from a 990-pound force from the guy wires is indeterminate. Our analysis includes a minimum factor safety of two. Given the marginal site soils, an in situ load test of a screw anchor installed as it will be in service was authorized by the County to document the performance of the anchor under load. Refer to the In Situ Load Test section below for the results. These services were in addition to the original scope proposed in our proposal dated May 25, 2017. In Situ Load Test The load test was performed on a screw anchor installed by the County prior to our arrival on site. The location coincided with the approximate center of the proposed tower. The anchor was installed in a vertical orientation with the center of the eye approximately 4 inches above grade. The vertical orientation is counter to the Campbell UT20 and UT30 Universal Towers