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HR Green, Inc. <br />Project B2204225 <br />October 3, 2022 <br />Page 10 <br /> <br /> <br /> <br />In areas of widening, to the extent possible, we recommend matching the existing soil in the upper 5 feet <br />of roadway with soils of a similar classification, moisture content, and performance characteristics. Do <br />not place non-granular backfill adjacent to in-place granular soils. <br /> <br />We recommend spreading engineered fill in loose lifts approximately 12 inches thick. We recommend <br />compacting engineered fill in accordance with the MnDOT specifications listed in Table 3 above. The <br />project documents should specify relative compaction of engineered fill, based on the structure located <br />above the engineered fill, and vertical proximity to that structure. <br /> <br />The project documents should not allow the contractor to use frozen material as engineered fill or to <br />place engineered fill on frozen material. Frost should not penetrate under pavements during <br />construction. <br /> <br />We recommend performing density tests in engineered fill to evaluate if the contractors are effectively <br />compacting the soil and meeting project requirements. <br /> <br />C.3. Pavements <br /> <br />C.3.a. Design Sections <br />Our scope of services for this project did not include laboratory tests on subgrade soils to determine an <br />R-value for pavement design. Based on our experience with similar clayey soils anticipated at the <br />pavement subgrade elevation, we recommend pavement design assume an R-value of 12. Note the <br />contractor may need to perform limited removal of unsuitable or less suitable soils to achieve this value. <br />Table 3 provides recommended pavement sections, based on the anticipated subgrade soils. <br /> <br />Table 3. Recommended Bituminous Pavement Section <br />Material <br />Thickness <br />(inches) Designation Specification <br />Bituminous Wear 3 (2 lifts) SPWEA240C 2360 <br />Aggregate base 6 Class 5 or 6 3138 <br /> <br /> <br />C.3.b. Performance and Maintenance <br />We based the above pavement designs on a 20-year performance life for bituminous. This is the amount <br />of time before we anticipate the pavement will require reconstruction. This performance life assumes <br />43