Agenda - Public Works Committee - 12/18/2018

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Brookview Estates Reconstruction Ramsey, Minnesota NTI Project No. 18.MSP06855.000 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 systems indicated above. 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. Mill and Overlay Option Portions of the roadway sections appear to have a sufficiently thick, in-place pavement section, which would lend itself to rehabilitation via mill and overlay techniques. The existing pavement thickness generally about 4 ½ inches thick, but locally was observed to be about 2 ½ inches thick. If a mill and overlay were performed, we would recommend that thin pavement areas (such as near SB-2) and distressed pavement areas be removed and replaced with a full depth (6 inch) patch. Full depth reclamation (FDR) would be feasible for this project area. Usually a blend of mineral aggregate base with the bituminous pavement is blended and the teeth of the reclaimers need to extend beyond the bituminous layers in order to prevent overheating. The pavement could be milled off and removed and replaced with fresh bituminous pavement. The millings can be blended with on-site aggregate base, with imported aggregate base or remixed at the plant to provide fresh aggregate base. The blended material should contain no more than 50 percent bituminous millings. In general, locations suitable for FDR would have aggregate base that is about the same thickness as the pavement plus 3 to 4 inches remaining to support the weight of the heavy machinery required for FDR. We recommend that the base be proof-rolled prior to placement of the new pavement materials to determine soft or unstable subgrade areas. 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 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. If rutting or localized unstable subgrade areas are observed, those areas should be subcut, moisture- conditioned, and re-compacted or removed to a stable depth. Excavations for soil corrections (if any) in paved areas should allow for a 2 foot oversize beyond the edges of the pavement. Page 5 of 7