Agenda - Public Works Committee - 01/17/2017

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Sunwood Drive—Street Improvements Ramsey,Minnesota NTI Project No.16.61770.100 UTILITY LINE CONSTRUCTION The native sand soils observed in soil borings were generally suitable for utility support and utility backfill. Due to the encountered groundwater levels and depending on the installation depth of the utilities,temporary dewatering may be required during the utility trench excavations. Stabilization of the trench subgrade may be required in order to provide a stable platform for construction. Stabilization could consist of a one half to one foot layer of crushed rock or sand with a maximum 5 percent material passing the No. 200 sieve and 50 percent passing the No. 40 sieve. The Geotechnical Engineer of Record or their designated representative should observe the project excavations to determine that unsuitable materials have been properly removed and adequate bearing support is provided by the exposed soils. The exposed soil at the base should be compacted to no less than 95 percent standard Proctor maximum dry density(ASTM D698). Such observations and testing should be performed prior to backfilling. The on-site non-organic soils are anticipated to be suitable for reuse if properly moisture conditioned and compacted. Replacement backfill required in utility trenches should consist of non-organic material similar to the surrounding soil. All import fill should be approved by NTI or the City's representative. It is especially important that trench backfill for utility construction within paved areas be thoroughly compacted to minimize future pavement damage. We recommend that such soils be compacted in accordance with the recommendations noted in the "Placement and Compaction of Engineered Fill" section in Appendix B of this report. The stability of embankments along utility excavations is dependent on soil strength, site geometry, moisture content, and any surcharge load for excavated soils and equipment. We present cautionary remarks concerning stability of excavation sideslopes in the "Excavation Stability' section of this report. The Contractor is solely responsible for assessing the stability of and executing underground utility and project excavations using safe methods. The contractor is also responsible for naming the "competent individual" as per Subpart P of 29 CFR 1926.6(Federal Register-OSHA). The Geotechnical Engineer of Record or their designated representative should observe the project excavations to determine that conditions are similar to those encountered in the borings, and that adequate bearing support is provided by the exposed soils. Excavation Stability Excavation depth and sidewall inclination should not exceed those specified in local, state or federal regulations. Excavations may need to be widened and sloped, or temporarily braced, to maintain or develop a safe work environment. Contractors must comply with local, state, and federal safety regulations including current OSHA excavation and trench safety standards. Temporary shoring must be designed in accordance with applicable regulatory requirements. Excavations that penetrate the groundwater surface will require dewatering with sand points or wells. We recommend that the groundwater surface be maintained a minimum of 2 feet below the bottom of the exposed excavation. Page 4 of 7