Agenda Packets - 1991/07/01 - Laserfiche WebLink

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Rating System The rating system employed for MOunds View streets is a visual ranking of common defects associated with reducing the life of a street. These defects include rutting (depressions in the wheel tracks) , raveling (loss of surface aggregate or binder material) , flushing (excess asphalt bleeding to the surface) , corrugations (ripples across the direction of traffic) , patching, and various types of cracking. Each type of defect is ranked according to the severity and area affected. The rankings are then used to determine a 'score' for each segment of street. The segments are usually a city block in length. The inventory of scores is maintained in a computer database. The maintenance strategy appropriate for different segments is then established by a computer program that searches the database comparing various scores to the maintenance strategy under consideration. This is also the method for determining the street segments to be included for reconstruction. Preventive Maintenance During the last 3 years the city has had a preventive maintenance program for city streets. This program has included thin overlays (in 1988) and chip seals (in 1989 & 1990) . Patching is currently a year around program under city forces . The purpose of preventive maintenance is to improve certain types of pavement defects before they create problems requiring reconstruction. The pavement of a street can be compared to a roof of a house. As long as moisture is kept out of the pavement system, the structural integrity is maintained. When moisture permeates the system, the structural integrity is reduced significantly. Similar to a roof, the strength is decreased as the structural components deteriorate. The subsoil and base courses of a roadway can lose up to 75% of the structural capability when saturated-. Preventive maintenance such as chip seals, is an attempt to restore the impermeability of the pavement. This is accomplished by the asphalt layer sprayed onto the surface. The chip layer is intended to protetit th- _ . . . - wearing sur ace for traffic. The chips also improve stopping distance_ andimprovereflectivity of the pavement, both safety considerations. Thin overlays function much the same as chip seals. However, there is also an increase in the load carrying capability of the pavement system. Overlays are significantly more expensive than chip seals and therefore are used only where conditions warrant the additional expense. Patching and crack sealing are maintenance strategies that address isolated areas of the pavement. Patching is obviously the method of filling potholes and repairing pavement cuts . It is 2