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Bolton & Menk, Inc. <br />Project B2204011.00 <br />April 20, 2023 <br />Page 3 <br /> <br /> <br />Utility Installation Recommendations <br /> <br />Utility Subgrade Stabilization <br />We anticipate the soils at typical invert elevations will be suitable for utility support. However, if <br />construction encounters unfavorable conditions such as soft or loose soils or perched water at invert <br />grades, the conditions may require some additional subcutting and replacement with sand or crushed <br />rock to prepare a proper subgrade for pipe support. If crushed rock is used as pipe bedding, we <br />recommend wrapping the aggregate in geotextile fabric to prevent the migration of fine-grained <br />materials into the voids of the aggregate. <br /> <br />Excavation Oversizing <br />If subcutting beneath utilities is required, we recommend extending the excavations outward and <br />downward at a slope of 1H:1V (horizontal:vertical) or flatter to a maximum depth of 2 feet. <br /> <br />Excavated Slopes <br />Based on the borings, we anticipate the majority of on-site soils in excavations will consist of cohesive till <br />deposits. These soils are typically considered Type B or C Soil under OSHA (Occupational Safety and <br />Health Administration) guidelines. OSHA guidelines indicate unsupported excavations in Type B soils <br />should have a gradient no steeper than 1H:1V, while Type C soils have a gradient no steeper than <br />1 1/2H:1V. Slopes constructed in this manner may still exhibit surface sloughing. OSHA requires an <br />engineer to evaluate slopes or excavations over 20 feet in depth. <br /> <br />An OSHA-approved qualified person should review the 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. The project specifications <br />should reference these OSHA requirements. <br /> <br />Excavation Dewatering <br />We recommend removing accumulated water from the excavations. Project planning should include <br />temporary sumps and pumps for excavations in low-permeability soils, such as clays. <br /> <br />