6.3. SR 02-07-2005 - Laserfiche WebLink

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I I I City of Elk River Project BN-04-06875 December 8, 2004 Page 5 I I D.l.b. Proofrolls. Before placing the aggregate base, we recommend the pavement areas be proofrolled to help detect soft areas. As a final check, just prior to placing the bituminous, we recommend the areas again be proofrolled. This precautionary measure will assist in detecting localized soft spots. Any soft spots noted during the proofrolling process should be subexcavated, replaced with drier soils, and compacted. A qualified geotechnical engineer should observe the proofrolling process to make a [mal evaluation of the subgrade. I I D.l.c. Anticipated Subgrade. After the preparation, we anticipate the subgrade will be compacted silty sands and poorly graded sand with silt. Laboratory tests to determine the R- values of these soils were not included in our scope of services. In the absence of additional data, we recommend an R-value of30. I I D.l.d. Design Sections. For the above subgrade and the assumed traffic (see Section C.l), we recommend a minimum of 3 1/2 inches of bitumin pus surface over 7 inches of crushed gravel base. I I D.l.e. Materials and Compaction. We recommend all backfill and fill placed beneath proposed pavements be compacted to a minimwn of 95 percent of the standard Proctor maximum dry density up to within 3 feet of the final subgrade elevations.. We recommend all fill placed in the top 3 feet of the pavementsubgrades be compacted to a minimum of 100 percent. I We reco:inmend specifying aggregate base meeting the requirements ofMn/DOT SpeCification 3138 (Class 5). We recommend the bituminous base and wear courses meet the requirements ofMnlDOT Specifications 2350, Type MV. We recommend the aggtegate gradation for the asphalt mix meet the gradations inMnlDOT Table 2350-1. The gradation chosen will depend on the bituminous layer thicknesses. We recommend thePeIfolmanc~ Graded Asphalt cement be a PG 64-22 or 58-28. I I We recommend compacting the Class 5 to at least 100 percent of its maximum standard Proctor dry density. We recommend compacting the asphaltic concrete to at least 91 1/2 percent of its theoretical maximum density. I I D.2, Excavation It is our opinion that the soils encountered by the borings can be excavated with a backhoe, front- end loader, motor grader Or scraper. The borings indicate that the soils in the sidewalls of the excavations will be Type C soils under Department of Labor Occupational Safety and Health Administration (OSHA) guidelines. I I I