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<br /> <br /> <br />Geotechnical Report <br />2018 PMP Streets <br />Arden Hills, Minnesota <br />WSB Project No. 010111-000 Page 8 <br />damage caused from settlement. Additional tests would be required to estimate the settlement below the <br />utility pipe, but we would estimate it could be greater than 6 inches. <br /> <br />In addition, we recommend sand conforming to MnDOT Specification 3149.2F Granular Bedding be <br />placed in the bottom of an unstable or wet excavation and below the utility pipe. The sand should have <br />100 percent by weight passing the one inch (1”) sieve and less than ten percent (10%) by weight passing <br />the #200 sieve. The granular bedding should be placed to at least the crown of the pipe. Trench backfill <br />above this point may consist of the non-organic excavated soils once properly moisture conditioned. <br /> <br />4.4 Dewatering <br />If dewatering is required, it can likely be accomplished with sumps and pumps placed at low points in the <br />utility trenches. In sandy areas, sand point wells may be required. <br /> <br />4.5 Backfill and Fill Selection and Compaction <br />The on-site non-organic soils may be reused as backfill and fill provided they are moisture conditioned <br />and can be compacted to their specified densities. Any wet soils excavated would need to be dried <br />before reuse as an engineered fill. Backfills with cobbles larger than six inches (6”) should not be placed <br />within 3 feet of the pavement section or in contact with utilities. We recommend that sandy soils be <br />moisture conditioned to meet compaction specifications and clayey soils be moisture conditioned to within <br />two percent (2%) below to three percent (3%) above their optimum moisture contents as determined from <br />their standard Proctor tests (ASTM D-698). Fill should be spread in lifts of less than 8 inches for clays <br />and less than 12 inches for sands. <br /> <br />Where organics are excavated for utility placement, we recommend placing a lightweight fill to prevent <br />increased loads on the subgrade soils below the utility pipe. <br /> <br />Table 4 indicates the recommended compaction levels. <br /> <br />Table 4: Recommended Level of Compaction for Backfill and Fill <br />Area Percent of Standard Proctor <br />Maximum Dry Density <br />Pavement: Within 3 feet of top of subgrade <br /> Within 3 foot radius of vertical utility structure <br />100 <br />Pavement: Greater than 3 feet below top of subgrade 95 <br />Utility Trench 95 <br />Landscaping (non-structural) 90 <br /> <br />4.6 Construction Considerations <br />Good surface drainage should be maintained throughout the work so that the site is not vulnerable to <br />ponding during or after a rainfall. If water enters the excavation, it should be promptly removed prior to <br />further construction activities. Under no circumstances should fill be placed into standing water. <br /> <br />Soil corrections at this site for pavement subgrades may not be continuous in all areas. We recommend <br />tapering the fills back to native soils at a ten to one (10:1) slope. <br /> <br />4.7 Construction Safety <br />All excavations must comply with the requirements of OSHA 29 CFR, Part 1926, Subpart P “Excavations <br />and Trenches”. This document states that excavation safety is the responsibility of the contractor. <br />Reference to this OSHA requirement should be included in the job specifications. <br /> <br />The responsibility to provide safe working conditions on this site, for earthwork, building construction, or <br />any associated operations is solely that of the contractor. This responsibility is not borne in any manner <br />by WSB.