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The Engineering Division administers an annual program to repair and maintain City streets. Staff utilizes a computerized Pavement Management System (PMS) that is used to inventory city streets, categorize their current and future condition, and produce budget projections for short and long-term repair programs. The PMS, in conjunction with Engineering staff field reviews, is utilized to produce the yearly resurfacing list. The list is then modified and tailored for actual field conditions, and to fit within the City's resurfacing budget, which averages about $3,000,000 per year. The Resurfacing Program is divided into two main procedures, Overlays and Slurry Seals.
What They Are
The term "overlay" refers to the application of a layer of hot asphalt concrete (a.c.) to the surface of an existing street. Overlays are generally from 1-1/2 to 3 inches in depth, and must be rolled and compacted upon placement. A slurry seal differs from an overlay in that only a thin liquidy layer of asphaltic material and fine aggregate is placed onto the existing street surface. Only about 1/4 to 3/8 inch thick, the slurry mix is "squeegeed" onto the existing street surface. In both cases, the new material is carefully placed and allowed to cure prior to allowing use by public traffic.
What They Do
The application of hot mix a.c. actually thickens the existing street, giving it additional structural strength. Overlays are used to repair streets that are already in a state of deterioration, and are sometimes combined with grinding or pulverization of the existing street material, depending on the condition of the street. They vary in cost from $1.50 to $2.00 per square foot. The slurry seal is used on streets that are still in "good" shape, that is, with little or no cracking, rutting or structural failure. A slurry seal is a more preventative measure and is much less costly than an overlay (only around 15 cents per square foot). This treatment effectively extends the life of the pavement by sealing small surface cracks against water intrusion, and can postpone the need for resurfacing or other structural repairs by as much as five to seven years
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