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City of Arden Hills <br /> Project BL-12-05201 <br /> September 28, 2012 <br /> Page 3 <br /> A pavement life of 20 to 25 years will typically include at least one major repair, such as an overlay, in <br /> addition to timely localized repairs(patching and crack sealing)and seal coating. According to the <br /> historical data,Glenhill Road was sealcoated in 1998. While routine maintenance most likely occurred, <br /> no other preventive maintenance was recorded in the pavement management system. <br /> According to the available data,the last structural improvements in each of the segments ranged from <br /> 17 years to 32 years. Given the condition data and the age of the pavements, it is our opinion that the <br /> segments are in need of a major structural improvement,such as reconstruction or pavement <br /> reclamation. <br /> Recommendations <br /> The general nature of the materials encountered by the borings suggests that the subgrade soils are <br /> reasonably well-suited for pavement support. It is our opinion that the pavements can generally be <br /> designed assuming silty sand subgrade soils. A conservative R-value of 30 can be assumed for design <br /> purposes. If areas of less-suitable soils are encountered,we recommend subgrade improvements; <br /> particularly if those areas will be excavated for new water main installations.The recommended <br /> corrections would include subcutting and replacing the less-suitable soils with compacted fill. <br /> Alternatively, if it is desired to reduce earthwork corrections in those areas,the pavement layers could <br /> be thickened to account for weaker subgrade soils. <br /> Groundwater was not noted in any of the borings to depths of 5 to 6 feet and will not likely significantly <br /> impact the design or construction of the pavements. Given the likely depth of watermain between 6 <br /> and 10 feet, it is possible that groundwater will be encountered. Dewatering may be required to <br /> facilitate placement and compaction of watermain backfill at some locations. <br /> Boring B16 encountered a layer of organic clay from 3 1/2 feet to 4 feet. We recommend that this be <br /> removed and replaced with suitable MnDOT select granular borrow. <br /> Reconstruction <br /> For full reconstruction,we typically do not recommend construction of full-depth pavements <br /> (pavements placed directly over subgrade soils without aggregate base),particularly when the subgrade <br /> soils consist of clayey soils,as was noted in some of the boring logs. We believe that there would be <br /> long-term benefits to placing an aggregate base layer beneath the bituminous surfacing. <br /> Based on the MnDOT State Aid design chart and assuming an ADT between 400 and 1000,we <br /> recommend a pavement section that includes 3 1/2 inches of bituminous pavement over 6 inches of <br /> aggregate base material with the following considerations: <br /> ■ We recommend removing the existing bituminous pavement. Reclaiming the existing <br /> bituminous pavement is an option, however,this may prove to be difficult without aggregate <br /> base. Seethe following section for more information pertaining to reclamation. <br /> BRAUN <br /> INTERTEC <br />