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Report of Geotechnical Exploration <br />North Arm Bay Boat Launch; Mound, MN <br />April 10, 2023 AAMEMICAN <br />AET Report No. P-0016964 E-NEER NG TEST - <br />1.0 INTRODUCTION <br />Hennepin County is proposing improvements to the existing boat launch along North Shore Drive <br />in the North Arm Bay of Lake Minnetonka in Mound, MN. The improvements consist of a new <br />storm water management system that will include elements of water retention and/or water <br />infiltration. To assist planning and design, you have authorized American Engineering Testing, <br />Inc. (AET) to conduct a subsurface exploration program at the site and conduct soil laboratory <br />testing. This report presents the results of the above services. <br />2.0 SCOPE OF SERVICES <br />AET's services were performed according to our proposal to you dated December 6, 2022, which <br />you authorized on December 8, 2022. The authorized scope consists of the following. <br />• Drilling and sampling 4 standard penetration test (SPT) borings to 20 feet in depth. <br />• Reviewing the recovered soil samples and perform limited laboratory soil testing. <br />• Conducting a geotechnical engineering review based on the data and preparing this <br />report. <br />These services were conducted for geotechnical purposes only. The scope is not intended to <br />explore for the presence or extent of environmental contamination in the soil or groundwater. <br />3.0 PROJECT INFORMATION <br />It is AET's understanding that Hennepin County is planning to improve the boat launch on North <br />Arm Bay with a stormwater management system. We understand infiltration trenches will be <br />constructed with bottom depths about 12 to 14 feet below existing grade, corresponding to about <br />2 to 4 feet below water table. We understand the infiltration system is planned to consist of, from <br />bottommost layer to uppermost layer: filter fabric, coarse aggregate, filter fabric, pea gravel, filter <br />fabric, sand subgrade. Drain tile may also be implemented as added assurance that the <br />stormwater runoff reaches the infiltration trenches. <br />4.0 SUBSURFACE EXPLORATION AND TESTING <br />4.1 Field Exploration Program <br />The subsurface exploration program conducted for the project consisted of four standard <br />penetration test borings performed on February 3, 2023. The logs of the borings and details of <br />the methods used appear in Appendix A. <br />Page 1 of 5 <br />120 <br />