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June 13,2023 <br />HWA Project No. 2022-188-21 <br />over-excavated areacan be backfilled with controlled density fiIl (CDF) to raise foundations <br />above wet conditions. Over-excavation to remove compressible soils should extend on either <br />side of the pipe a distance equal to the depth of over-excavation beneath the pipe. <br />General recommendations relative to the bedding of underground utility pipelines include: <br />. Pipe bedding material, placement, and shaping should be in accordance with the project <br />specifi cations and the pipe manufacturer's recommendations. <br />. Pipe bedding materials should be placed on relatively undisturbed coarse granular native <br />soils, or properly compacted fill. If the native subgrade soils are loosened during <br />excavation, the loosened material should be compacted or removed and replaced with <br />compacted bedding material. Pipe bedding should provide a ftrm, uniform, support <br />cradle for the pipe of at least 6 inches thickness. <br />o Prior to pipe installation, the pipe bedding should be shaped to fit the pipe haunches with <br />reasonable closeness to provide continuous support along the pipe. <br />Pipe bedding should extend to at least 6 inches above the top of the pipe, for the full width of the <br />trench. In areas where a trench box is used, the bedding material should be placed before the <br />trench box is advanced. Advancement of trench boxes should be performed carefully to prevent <br />disturbance of the bedding and any backfill. <br />4,10.2 Trench BackfiIl <br />Trench backfill should be considered structural fill and should meet the criteria set forth in <br />Section 4.12.2. However, where pipe trenches exist beneath landscaped areas, backfill <br />compaction requirements may be reduced, consistent with higher levels of backfill settlement <br />that may be tolerable. <br />4.ll PavsNInNr CoNsronnq,TIoNS <br />HMA (hot mix asphalt) pavement will be required for the extension of the access road, paving <br />for the recycling center, tire recycling area, scale and transfer station access ramps, compost area <br />and parking areas. Subgrade preparation, stabilization, placement, and compaction of crushed <br />rock base course and HMA should be conducted in accordance with the procedures outlined <br />below. <br />4.11.1 Subgrade Preparation for Areas to be Paved <br />Subgrade stripping should be conducted to remove all loose organic topsoil and other deleterious <br />materials exposing native mineral subgrade, sandy silt or sandy lean clay or sandy gravel with <br />silt. After stripping and excavating to remove topsoil, and prior to placing any fill, subgrade soils <br />2022-188-21 KCTS - Final Geotechnical Report 15 HWA GEOSCIENCES INC.