Agenda - Council - 01/13/2015 - Laserfiche WebLink

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The proof roll should be performed with a tandem axle dump truck loaded to gross capacity (at least 20 tons). Acceptance criteria of the proof roll shall be limited to rut formation no more than one inch (1”) depth (front or rear axles) and no pumping (rolling) observed during the visual inspection. Proof roll tests should be observed by an experienced technician or geotechnical engineer prior to placement of the aggregate base course to verify the subgrade will provide adequate pavement support. th We estimate that a properly prepared subgrade for Garnet Street Northwest and 168 Avenue Northwest will have an average stabilometer R-value of 30. For a 20-year design pavement life, Table 3 presents our thickness recommendations for flexible (bituminous) pavement. These recommendations were based upon subgrade conditions, the anticipated lightly loaded residential traffic described previously in this report, and the City of Ramsey’s typical street section for low- volume residential streets. Table 3: Flexible Pavement Thickness Design th PavementGarnet Street 168 Avenue Section Northwest Northwest Bituminous Wear Course (in) 1 ½ 1 ½ Bituminous Base Course (in) 2 2 Class 5 or 7 Aggregate Base (in) 6 6 Pavement recommendations assume the subgrade soils and aggregate section below paved surfaces will drain to subsurface piping for eventual discharge into storm sewer, or above grade to ditching, or similar acceptable systems. Lack of surface and subsurface drainage will significantly reduce the capacity and longevity of the pavement structures indicated above. Due to the relatively thick layer of soft and potentially compressible clay soil, long term secondary settlement may continue to occur near boring SB-2 and other areas with similar subsurface conditions. Since a soil correction excavation to remove the soft fat CH clay layer is likely not a practical option, additional maintenance in this area to fill cracks or build up settled areas may be required. The City should anticipate minor road maintenance and repairs in this area. We recommend pavements receive annual maintenance, as a minimum, to correct damages to the pavement structure, clean and infill cracks which develop, and repair or resurface areas which exhibit reduced subgrade performance. The lack of maintenance can lead to moisture infiltration of the pavement structure and softening of the subgrade soils. This, in turn, can degrade the performance of the pavement system and result in poorly performing pavements with shortened life expectancy. 5