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Hennepin Parks ' <br /> Project BABX-91-589 <br /> December 19, 1991 , <br /> Page 4 <br /> � ' <br /> ' <br /> C. Preliminary Analysis and Recommendations <br /> tion � <br /> C.1 Proposed Construc <br /> We understand the proposed construction will consist of a one-story visitors center as well as <br /> paved parking and drive areas. At this time, the type of construction, floor grade and building ' <br /> loads are unknown. For this report, we have assumed column loads to be less than 50 kips <br /> and wall loads to be less than 3 kips per lineal foot. We have also assumed a floor grade of � <br /> 942.0 feet. Once actual loads and tloor grades have been finalized, a review of this report <br /> should be made by us to determine ir the recommendations contained herein need to be ' <br /> revised. <br /> C.2 Building Pad Preparation ' <br /> We recommend the topsoil and the upper clay layer be removed from within the building <br /> area. The estimated excavation depth at each boring location is about 2 feet. Variations will , <br /> likely occur between the borings which will not be evident until the excavation is underway. <br /> If areas of the building require fill below proposed footing grades, we recommend the <br /> excavation of topsoil be oversized to provide lateral stability to the fill. The bottom of the ' <br /> excavation should be oversized 1 foot beyond the o.utside edge of the footings for each foot of <br /> depth below the bottom of the footing (a 1:1 slope). ' <br /> We recommend the bottom of the excavation be observed by our soils engineer or an assistant <br /> to evaluate the completeness of the topsoil removal and the suitability of the soils left inplace. ' <br /> This must be cione prior to the placement of fill. <br /> In the area of Boring ST-7, wz recommand the loose silty sand be surface compacted to , <br /> increase its inplace relative densitv. Given the soil's classification and moisture content, there <br /> is, however, a small risk the surface compaction will result in the sands becoming unstable. If , <br /> this occurs, a limited subcut of the silty sand may be needed. <br /> With suitable soils exposed, we recommend the bottom of the excavation be surface , <br /> compacted by several passes of a large drum, self:propelled compactor. This will further <br /> densify the upper natural sands. The excavation can then be backfilled with controlle� fill ' <br /> using loose lifts not exceeding 12 inches and compacted by a large drum, self-propelled <br /> compactor. The moisture content of the fill should be within three percentage points of , <br /> � <br />