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, Hennepin Parks <br /> Project BABX-91-589 <br /> December 19, 1991 <br /> ' Page 5 <br /> ' . <br /> ' o timum to enhance com atibili . We recommend all fill be com acted to a minimum <br /> P P tY P <br /> relative density of 92 percent of modified Proctor density (ASTM D 1557). <br /> ' . <br /> We understand you propose to obtain fill soils from other portions of this site. These soils <br /> ' will likely be similar to those encountered in the borings. The soils encountered in the borings <br /> are generally over the optimum moisture content and will not make good fill material unless <br /> dried to lower the moisture content. If the on-site soils cannot be sufficiently dried, drier fill <br /> ' will likely have to be imported to reestablish grades. <br /> ' C.3 Foundations <br /> After completing the recommended excavation and backfill, the soils will be suitable for <br /> support of the building using typical spread footings designed for an allowable bearing <br /> , pressure of 2,000 pounds per square foot (psfl. <br /> ' We recommend the perimeter footings be founded a minimum of 42 inches below exterior <br /> grade for frost protection. Interior footings may be placed immediately beneath the floor stab, <br /> provided the building will be heated during the winter months. <br /> ' <br /> C.4 Floor <br /> , After the building pad preparation has been completed, we anticipate the floor subgrade will <br /> be compacted fill. Backfill of footing excavations and below-slab mechanical trenches should <br /> be compacted to a minimum of 90 percent of the modified Proctor density. The compacte� fill <br /> ' should then be suitable for floor slab support. We suggest the upper 6 inches of soil below the <br /> floor slab consist of a clean sand (less than 10 percent fines passing the number 200 sieve) to <br /> ' reduce capillary rise of ground moisture, and thus reduce the potential for dampness of the <br /> floor. <br /> ' If floor coverings less permeable than the concrete slab will be used, we recommend a vapor <br /> barrier be placed beneath the slab. Consideration should be given to burying the vapor barrier <br /> ' beneath a layer of sand to reduce curling of the floor slabs. <br /> , <br /> ' <br /> , <br />