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Inwood 10 LLC <br />Project B14-08413 <br />December 3, 2014 <br />Page 8 <br />The excavation depths indicated in the above tabulation are approximate and will vary. The actual depth <br />of excavation needs to be determined in the field at the time of construction. An experienced <br />geotechnical engineering technician, under the direction of a geotechnical engineer, should work closely <br />with the excavating contractor during excavation to make the necessary field judgments regarding the <br />suitability of the exposed soils and to determine the extent of soft soils. <br />To provide lateral support and control settlement to the structural loads they will support, we <br />recommend oversizing (widening) the excavations 1 foot horizontally beyond the footings for each foot <br />the excavations extend below bottom-of-footing elevations. <br />Prior to the placement of engineered fill or footings, we recommend the exposed sand soils in the <br />bottoms of the excavations be surface compacted using a minimum of 5 passes over an area with a large <br />(minimum 3-foot-diameter drum), self-propelled vibratory drum compactor. <br />D.1.b.Excavation Support <br />Sandy soils are prevalent in the near surface soils, and portions of the sands are described as poorly <br />graded sand and would be classified as Type C Soil under OSHA guidelines. Based on this classification it <br />should be anticipated unsupported excavations be maintained at a gradient no steeper than 1 1/2 to 1 <br />(horizontal: vertical). In areas of the site encountering only silty sand tills the soils would be classified as <br />Type B Soil under OSHA guidelines. Based on this classification it should be anticipated unsupported <br />excavations be maintained at a gradient no steeper than 1 to 1 (horizontal: vertical). Slopes constructed <br />in this manner may still exhibit surface sloughing. If site constraints do not allow the construction of <br />temporary slopes with these dimensions, then temporary shoring may be required, and we should be <br />consulted for additional recommendations. <br />An OSHA approved competent person should review this soil classification in the field. Excavations must <br />comply with the requirements of OSHA 29 CFR, Part 1926, Subpart P, “Excavations and Trenches.” This <br />document states excavation safety is the responsibility of the contractor. Reference to these OSHA <br />requirements should be included in the project specifications. <br />D.1.c.Placement and Compaction of Backfill and Fill <br />Based on the results of the borings and laboratory tests, the sand soils frequently encountered below the <br />topsoil appear generally suitable for use as engineered fill. Any clay soils encountered being fine-grained, <br />will be more difficult to compact if wet or allowed to become wet, or if spread and compacted over wet <br />surfaces.