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Old Snelling Avenue Geotechnical Recommendations <br />October 7, 2020 <br />Page 4 <br /> <br /> <br />density. Project specifications are recommended to include material testing provisions such as gradation <br />and Standard Proctor tests for all sources of trench backfill. <br />Soil Correction <br />Soil correction is recommended for watermain in the vicinity of Boring B-8. Peat is recorded in the logs <br />between depths of 7 to 9 feet. A very loose layer of clayey sand (SC) underlies the peat. It is <br />recommended to excavate and remove all organic soils including peat as well as the very loose soil layer <br />below the watermain to a minimum depth of 11 feet below the ground surface and backfill with Select <br />Granular Borrow (MnDOT 3149.2B.2) prior to installation of the watermain. Compact the backfill to a <br />minimum 95% of the Standard Proctor maximum dry density. <br />A Type VI geotextile (MnDOT 3733) is recommended to be installed in conjunction with soil correction to <br />a depth below the bottom of the peat in lieu of the soil correction to a depth of 11 feet below the ground <br />surface. <br />STORM SEWER RECOMMENDATIONS <br />Storm sewer pipe and structures are recommended to be bedded on a minimum of 6 inches of Select <br />Granular Borrow (MnDOT 3149.2B.2). Structures installed deeper than 5 feet from finished grade are <br />recommended to be bedded on a minimum of 12 inches of Granular Borrow (MnDOT 3149.2B.2). <br />Backfill for proposed storm sewer pipe is recommended to conform to Select Granular Borrow (MnDOT <br />3149.2B.2). Place backfill in lifts of not more than 6 inches thick from the bottom of the trench to a <br />minimum of 6 inches from the top of the pipe. Compact the trench backfill to a minimum 95% of the <br />Standard Proctor maximum dry density. Project specifications are recommended to include material <br />testing provisions such as gradation and Standard Proctor tests for all sources of backfill. <br />See Watermain Recommendations section for trench backfill recommendations. <br />SANITARY SEWER RECOMMENDATIONS <br />It was assumed that sanitary sewer pipe and structures are to be installed at a depth of 10 to 12 feet <br />below finished grade using and open cut trench. The trench is recommended to extend a minimum of 12 <br />inches below the bottom of the pipe. <br />Backfill around the pipe is recommended to conform to Select Granular Borrow (MnDOT 3149.2B.2). <br />Place backfill in lifts of not more than 6 inches thick from the bottom of the trench to a minimum of 12 <br />inches from the top of the pipe and compact to a minimum 95% of the Standard Proctor maximum dry <br />density. Project specifications are recommended to include material testing provisions such as gradation <br />and Standard Proctor tests for all sources of backfill. <br />See Watermain Recommendations section for trench backfill recommendations. <br />GENERAL CONSTRUCTION CONSIDERATIONS <br />Depending on weather and season, dewatering may be required for subgrade and utility excavations <br />along the project. Project specifications are recommended to require a written Dewatering Plan to be <br />submitted by the contractor prior to commencing any excavation work. <br />Excavations are recommended to be in accordance with OSHA 29CFR Parts 1926.650 through <br />1926.652.