1206 & 1206 1%2 S Newhope St - Soils Report

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be performed for verification of the potential corrosion of the on-site soils to ferrous metals and copper, ifneeded. The test can be performed during and/or after completion ofgrading. All utility and drain line trench backfills should be compacted to a minimum relative compactron of 90 percent (per ASTM D1557). The existing subgrade earth materials cannot be densified adequately by water flooding and jetting techniques. Therefore. native trench backfill materials should be placed in lifts approximately 6 inches in thickness, watered as necessary to achieve near optimum moisture conditions, and then mechanically compacted in place to a minimum relative compaction of 90 percent (per ASTM D|557). A representative of the project geotechnical consultant should probe and test the backfills to verify adequate compaction. Note: The pipes should be embedded and shaded with about 6 inch thick layer of imported clean sand (for protection ofthe pipes) prior to backfilling with native soils. As an altemative. where drain pipe or utility lines may be damaged by mechanical compaction equipment, imported clean sand having a sand equivalent (SE) value of 30 or greater may be utilized. The clean sand backfill materials should be watered to achieve near optimum moisture conditions and then tampcd into place. No specific rclative compaction will be required tbr clean sand backfill: however. observation. probing. and if deemed necessary, testing should be performed by a representative ofthe project geotechnical consultant to verify an adequate degree of compaction ofclean sand backfill. If imported clean sand is to be used for backfill of exterior trenches. it is recommended that the upper l2 inches of trench backfill materials be consisted of properly compacted on-site soil materials. This is to reduce the potential substantial infiltration of irrigation and rainwater into granular trench backfi ll materials. Where an utility trench is proposed near a building footing, the bottom ofthe trench should not extend below a l:l (horizontal to vertical) plane projected downward from the bottom edge of the adjacent footing. Where this condition occurs. the adjacent fboting should be deepened or the utility line should be installed first and the trench backfilled and compacted prior to constructing the footing. Ceotechnical lntemational will cooperate with the c iv illstructural design engineer and other consultants of record for this project and geotechnically review the foundation plan and other plans. if any (to be used for this project) to ensure that our recommendations have been properly interpreted and incorporated into the design and preparation of the plans. After acceptance of the plans. we will sign and stamp on the plans. Geotechnical Obserl ation and I'estins During Construction We recommend that a qualified geotechnical consultant be retained to provide geotechnical engineering services, including geotechnical observation/testing. during the construction phase of the project. This is to verify the compliance with the design, specifications and/or Page 8 Utilitv and Drain Line Trench Backflll Cooperation With Pro.iect Civil/Structural Desiqn Ensineer And Other Consultants And Ceotechnical Review of Plans