AIA 101 Agreement 08302024 - Laserfiche WebLink

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June 13, 2023 HWA Project No. 2022-188-21 Structural fill should be moisture conditioned, placed in loose horizontal lifts less than 8-inches thick, and compacted to at least 95% of maximum dry density as determined using test method ASTM D 1557 (Modified Proctor) for material containing less than 30% coarse gravel by weight. Achievement of proper density of a compacted fill depends on the size and type of compaction equipment, the number of passes, thickness of the layer being compacted, and soil moisture -density properties. In areas where limited space restricts the use of heavy equipment, smaller equipment can be used, but the soil must be placed in thin enough layers to achieve the required compaction. When the first fill is placed in a given area, and/or anytime the fill material changes, the area should be considered a test section. The test section should be used to establish fill placement and compaction procedures required to achieve proper compaction. The geotechnical consultant should observe placement and compaction of material in the test section to assist in establishing an appropriate compaction procedure. Once a placement and compaction procedure is established, the contractor's operations should be monitored and sufficient periodic density tests performed to verify that proper compaction is being achieved throughout. 4.12.3 Ground Water Control We anticipate that groundwater seepage may be encountered locally in the fine-grained alluvium or within the coarse -grained alluvium. Ground water monitoring conducted by others indicates that the ground water level is likely higher during the summer months during the local irrigation season. Therefore, we recommend that excavation in excess of what is required for subgrade preparation take place in the fall months after local irrigation has been terminated. During construction, the Contractor should be prepared with appropriate means and methods to ensure work takes place in relatively dry conditions during over -excavation and removal and replacement of compressible soils as necessary. It is recommended that if excavation takes place during the irrigation season the Contractor be prepared to control ground water through use of a combination of sumps and pumps and ditching to convey water away from the work area. The Contractor should limit the area opened up to that which can be backfilled with minimal sidewall sloughing during one shift. Quarry spalls or other permeable rockfill may be used to backfill below the ground water table and provide a stable base for placement of structural fill. Where quarry spalls or permeable rockfill is used, a non -woven geotextile meeting the requirements for separation found in Table 3 of Section 9-33.2(1) of the WSDOT Standard Specifications (WSDOT, 2023) shall be installed over the rockfill prior to placement of structural fill. 4.12.4 Temporary Slope Cuts We anticipate that the foundation cuts for the new transfer station building, and the new scale facility can be made with conventional excavating equipment. However, excavation wherever the coarse -grained alluvium is encountered, difficult digging conditions may be expected to exist, and the Contractor should be prepared to encounter cobbles and boulder -sized material. 2022-188-21 KCTS — Final Geotechnical Report 23 HWA GEOSCIENCES INC