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<br /> <br /> <br />Geotechnical Report <br />2021 Street Improvements <br />Hugo, Minnesota <br />WSB Project No. 015887-000 Page 7 <br />be achieved in fill areas with proper compaction of embankment materials and in cut areas through <br />proper subgrade preparation. The stability of the pavement subgrade should be evaluated prior to <br />placement of the sand subbase using the test roll procedure (MnDOT 2111), except a fully loaded tandem <br />axle dump truck or a full water truck should be utilized for the proof roll. If unstable soils are found under <br />the test roll, these soils should be improved by means of scarification, moisture conditioning, and re- <br />compaction, or by subcutting and replacement. <br /> <br />4.4 Pavement Area <br />Once the site has been prepared as recommended, we anticipate the prepared subgrade soils will consist <br />mostly of sands. Based on the MnDOT Flexible Pavement Guide from 2017, the R-values of the <br />subgrade soils would generally be 70. Due to the presence of fills and normal diversity within glacially <br />deposited soils, we used a design R-value of 50 for the roadway. <br /> <br />Traffic volumes were not available for the roadways. Based on our experience with similar roadways, we <br />estimated the Equivalent Single Axle Loads (ESAL’s) to be about 50,000. Our design is based on a <br />standard twenty (20) year design life of the pavement section and a 10-ton design. <br /> <br />Based on MnDOT’s FlexPave excel design utilizing granular equivalent charts, we recommend the <br />pavement section indicated below in Table 5. <br /> <br />Table 5: Recommended Flexible Pavement Section <br />Section Thickness (inches) Granular Equivalent <br />Bituminous Course, MnDOT 2360 SPWEB340C 2 4.5 <br />Bituminous Course, MnDOT 2360 SPWEB340C 2 4.5 <br />Aggregate Base, MnDOT 3138 (Class 5, 5Q, or 6) 8 8 <br />Subgrade Preparation, MnDOT 2112 Yes - <br />TOTAL - 21 <br /> <br />We recommend limiting Recycled Asphalt Pavement (RAP) within the upper wear course to a maximum <br />of 10 percent in order to minimize cracking. We have assumed a traffic level of 3 in our design to provide <br />resistance to rutting. <br /> <br />Aggregate base placement for pavement support should meet the gradation and quality requirements for <br />Class 5, 5Q, or 6 per MnDOT specification 3138. Aggregate base material should be compacted to 100 <br />percent of its standard Proctor maximum dry density. <br /> <br />Within several years after initial paving, some thermal shrinkage cracks will develop. We recommend <br />routine maintenance be performed to improve pavement performance and increase pavement life. <br />Pavement should be sealed with a liquid bitumen sealer to ret ard water intrusion into the base course and <br />subgrade. Localized patch failures may also develop where trucks or buses turn on the pavement. When <br />these occur, they should be cut out and patch repaired. <br /> <br />The pavement sections above provide options to meet the ESAL requirements. Other pavement design <br />options would be acceptable as well as long as they meet the minimum requirements for bituminous <br />thickness, aggregate base thickness, and can meet the ESAL requirements. <br /> <br />4.5 Utilities <br />Invert elevations for the watermain and sanitary sewer are anticipated to be between 8 and 12 feet below <br />grade. Based on the borings, the subgrade soils for the utilities will consist chiefly of sands. <br /> <br />Underground utilities are expected to be installed by backhoes completing th e excavations and placing <br />fills. Soil compactors should be used to compact the fill in even lifts to the specified densities.