Agenda - Council - 04/14/2020 - Laserfiche WebLink

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�1 20-01 Variolite Street Reconstruction Ramsey, Minnesota NTI Project No. 19. MSP09109.000 Due to the compressibility of the localize underlying swamp deposited soils, positive changes in grade should be minimized to the extent practical. In addition, any proposed increases in grade should occur as early as possible in the construction process to allow for as much consolidation as practical to occur prior to the placement of aggregate base and pavement. 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 based on soil types as referenced below: • Poorly graded sand (SP) — R-value of 50 • Poorly graded sand with silt (SP-SM) — R-value of 40 • Silty sand (SM) — R-value of 25 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. Properly constructed pavements, even those constructed entirely over inorganic soil, will crack due to creep movements, changes in temperatures, frost action, and other factors. Due to the organic nature in some areas of the roadway subgrade, the pavements should be expected to move and crack more than a typical pavement section. Features that would help reduce this movement and cracking include: • Installing finger drains about catch basins, low lying areas, • Placing a reinforcement geotextile or geogrid under the aggregate base or within the aggregate base, • Adding a 1 foot or thicker section of clean sand below the aggregate base to act as a drainage layer. 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. Page 9 of 10