Agenda - Council - 01/26/2016 - Laserfiche WebLink

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Andrie Street Improvements Ramsey, Minnesota NTI Project No. 15.61197.100 OPINIONS OF MINIMUM PAVEMENT THICKNESS Estimates of minimum thicknesses for new pavement sections for this project have been based on the procedures outlined in the MnDOT Pavement Design Manual using soil parameters based on soil types. The following minimum thicknesses were estimated based upon our estimated traffic loading, limited soils information, variation across the project area, and experience with similar projects and soil conditions. The performance of stabilometer or similar tests, were beyond the scope of this report; however, they may be performed, upon request, for an additional fee. We estimate that a properly prepared subgrade would have an average stabilometer R -value of 40. For a 20 -year design pavement life and light commercial traffic volumes, Table 2 presents our thickness recommendations for flexible (bituminous) pavement. The 9 -ton design assumes that there will less than 300 heavy commercial vehicles per day, a thicker pavement section may be needed if the city anticipates more growth in the project area. The pavement section also is intended to approximate the existing pavement section to help create a more uniform pavement surface in areas of lane widening. Table 2: Recommended Flexible Pavement Thickness Design Alternative Pavement Section (7 -ton) (9 -ton) Bituminous Wear Course (inches) Bituminous Base Course (inches) Class 5 or 7 Aggregate Base (inches) 1.5 2.0 6.0 2.0 2.5 8.0 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. EXCAVATION STABILITY Excavation depth and sidewall inclination should not exceed those specified in local, state or federal regulations. Excavations may need to be widened and sloped, or temporarily braced, to maintain or develop a safe work environment. Contractors must comply with local, state, and federal safety regulations including current OSHA excavation and trench safety standards. Temporary shoring must be designed in accordance with applicable regulatory requirements. ENGINEERED FILL & WINTER CONSTRUCTION The soils encountered at the project locations will be susceptible to freezing if not provided adequate drainage, insulation or coverage. Frozen soil should not be used as backfill. When the ambient air temperature falls below freezing for an extended period of time, frost forms, and soil near the surface grade expands. Settlement of the fill may occur as the frozen soils thaw. Page 4 of 15