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Preliminary Report of Geotechnical Exploration <br />Main & Gates Redevelopment; Elk River, Minnesota AMERICAN <br />July 9, 2021 ENGINEERING <br />Report No. P-0001445 TESTING, INC. <br /> <br /> <br /> <br />Page 5 of 10 <br />completely removed. This would result in excavation depths at the boring locations as shown in <br />Table 6.2.1. <br /> <br />Table 6.2.1 – Recommended Excavation Depths <br />Boring Location Surface Elevation (ft) Excavation Depth (ft) Approximate Excavation <br />Elevation (ft)* <br />1 96.3 4 92 <br />2 94.4 7 87 <br />3 89.3 3 86 <br />4 92.9 7 86 <br /> *Rounded to the nearest ½ foot. <br /> <br />The depths/elevations indicated in Table 6.2.1 are based on the soil conditions at the specific <br />boring locations. Since conditions will vary away from the boring locations, it is recommended <br />that AET geotechnical personnel observe and confirm the competency of the soils in the entire <br />excavation bottom prior to new fill or footing placement. <br /> <br />Where the excavation extends below foundation grade, the excavation bottom and resultant <br />engineered fill system must be oversized laterally beyond the planned outside edges of the <br />foundations to properly support the loads exerted by that foundation. This excavation/engineered <br />fill lateral extension should at least be equal to the vertical depth of fill needed to attain <br />foundation grade at that location (i.e., 1:1 lateral oversize). <br /> <br />Prior to placing fill soils above the naturally deposited alluvial soils, we recommend the soils be <br />surface compacted to improve density and provide a more consistent subgrade condition. We <br />recommend the soils be compacted by a self-propelled roller having a minimum drum diameter <br />of 3 feet. The compactor should make at least 8 passes over the entire excavation bottom in <br />perpendicular directions (e.g. 4 passes east-west and 4 passes north-south) before beginning fill <br />placement. The base soils may need to be wetted prior and during compaction. <br /> <br />6.2.2 Fill Placement and Compaction <br />Fill placed to attain grade for foundation and floor slab support should be compacted in thin lifts <br />(less than 8 inches in thickness), such that the entire lift achieves a minimum compaction level of <br />98% of the standard maximum dry unit weight per ASTM:D698 (Standard Proctor test). Fill Draft