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�. <br /> � Mr. Charles Thompson <br /> Project BL-04-05907 <br /> � October 27, 2004 <br /> . Page 6 <br /> � � <br /> � <br /> = If excavations extend below the bottom of footing grade, the bottoms of excavations should be oversized <br /> � 1-foot horizontal for every vertical foot of excavation below the proposed footings. The oversizing is to <br /> � provide lateral support to the building's footings. If excavations occur in highly organic soils, the <br /> oversizing should be increased to 1 1/2:1 or 2:1 (horizontal to vertical). This should be reviewed in the <br /> � field o�a case-by-case basis by a qualified geotechnical engineer. <br /> � Fill required to attain the proposed grades may consist of any debris-free,non-organic mineral soil. We <br /> � recommend that each lift be compacted to a minimum of 97 percent of its maximum dry density <br /> , determined in accordance with American Society for Testing and Materials (ASTM)Test Method D 698 <br /> (standard Proctor). The fill should have a moisture content within 3 percentage points of its optimum <br /> s , moisture. Moisture conditioning of these soils may be necessary to achieve minimum densities. All �11 <br /> , should be placed in 8-inch lifts and compacted with a large vibratory compactor. <br /> � If deeper excavations are performed near the area of Boring ST-4,which would result in greater than <br /> i10 feet of replacement fill soils needed to attain desired footing grades,the soil compaction level should <br /> � be increased to a minimum of 100 percent for the standard Proctor density. In addition,it may be prudent <br /> � to import granular soils in this area to reduce the risk of long-term post-filling settlements. Sand fill <br /> � should be placed to an elevation where no more than 10 feet of additional clay fill is needed to reach final <br /> grades. This situation should be reviewed on a case-by-case basis as the design process continues. The <br /> � need for an increased soil compaction soil specification and the possibility of importing granular soils as <br /> � portions of the fill soils would be determined based no the proposed building elevations, loads, and <br /> construction schedule. <br /> � <br /> � If water accumulates in excavation bottoms, it should be removed prior to fill placement. Alternately, <br /> S clean sand(less than 5 percent passing the number 200 sieve and less than 50 percent passing the number <br /> 40 sieve) should be used until the fill is at least 2 feet above water levels. . <br /> � <br /> � C.4. Foundations <br /> ! C.4.a. Depth. We recommend that the perimeter footings in heated areas be founded a minimum of <br /> � 42 inches below the nearest exterior grade for frost protection. Interior footings may be placed <br /> immediately beneath the slab. Foundation elements in unheated areas should be founded at least 5 feet <br /> � below grade for frost protection. <br /> � <br /> C.4.b. Subgrades. At these depths,we anticipate that the footings will bear on native glacial till or <br /> = outwash soils or on engineered fill. <br /> � <br /> � <br />