CCP 04-08-2002 - Laserfiche WebLink

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I I. I I . I I I I .. I I I I I I . .. . II. PROPOSED ROADWAY IMPROVEMENTS Three alternatives have been considered for this project: A. Full depth mill and overlay. B. Reconstruct 28'with a 40' radius end. C. Reconstruct 32' with a 50' radius end. A. Full depth mill and overlay. From the soil borings taken and review of the PCI rating data, it was determined that the distress to the pavement surface is predominantly due to the frost heave action of the soils beneath the pavement. The original bituminous pavement and base had an initial thickness of 8 inches which provided minimum protection from the effects of annual frost heaving. A mill and overlay would improve the surface in the short term but is expected to deteriorate at a rapid rate because it doesn't "fix" the subbase problem. If the Council decides to select the mill and overlay option the City Engineer believes that a full depth mill will be needed (cold in-place recycling) as the as the existing pavement would more than likely break up completely as a result of the operation of the milling machine. B. and C. Full Reconstruction Both of the reconstruction alternatives would include the construction of concrete curb and gutter, driveway aprons, driveway pavement (within ROW), roadway subdrainage and 4" of bituminous pavement in accordance with the City's standard plans. It is assumed that the reconstruction alternatives would be built within the existing right of way and would follow the existing alignment. Eight soil borings were taken to determine the condition of the existing subbase, 3 in each ofthe cul-de-sacs and 2 on Benton Way. The soil borings show that the road was built correctly to the design standards when it was constructed but would not meet current design standards. The borings indicate that the existing clay base is stable but retains moisture and is therefore susceptible frost heaving during freeze/thaw cycles. The geotechnical engineer anticipates that the addition of 12" of sand subbase with drain tile connections to the existing storm sewer catch basins would provide the necessary drainage and protection from frost heaving damage. The City's standard street construction includes sand subbases and drain tile for this purpose. The geotechnical engineer was consulted on his opinion relative to the potential of construction traffic damaging Benton Way. The geotechnical engineer believes that based upon the soil boring information, construction traffic will likely shorten the life span of the Benton Way pavement but the likelihood of significant immediate or noticeable damage is low. 4