Street Maintenance Programs
As one of the City’s largest assets, the street network must be properly maintained or it will fall into disrepair and become a liability. To obtain the best return on investment, it is necessary to apply the most appropriate maintenance program to the pavement at the time it is needed most. Apply maintenance too soon and money will be wasted. Apply the maintenance too late and the pavement may not be salvaged. An average of $2,567,000 is expended every year by the City of Amarillo, Streets Department, to maintain over 2000 lane miles of streets. These maintenance programs are comprised of Crack Sealing, Chip Sealing and Overlay operations. Maintenance activities extend the life of the street by preventing water intrusion. Repair work, such as pothole repairs, restores the street if it has been damaged.
Crack sealing is a intermediate maintenance activity that is done between seal coats or overlay cycles and prolongs the life of the street surface. Sealing the street cracks with hot asphalt sealant will keep water from infiltrating the supporting sub-grade soils. If sub-grade soils should become wet, the asphalt will break or crack as traffic drives over the soft spot. Left unattended, the soft spot will expand and lead to more costly repairs.
|CHIP SEAL PROGRAM
Chip seal is sometimes referred to as seal coating. Seal coating is the primary maintenance activity for local, or residential, streets. Seal coating is the most cost effective full width street maintenance activity (2010 cost – $1.21/Sq. Yard).
The objective is to place a layer of liquid asphalt on a paved surface that has oxidized and is drying out and lost its flexibility. Hot liquid asphalt will rejuvenate the pavement and seals it to stop water from infiltrating to the supporting base material. A layer of pre-coated gravel rock is spread on top of the hot liquid asphalt to provide a “wear” course. The liquid asphalt holds the rock in place once it cures and the rock provides vehicles with better traction and a surface that will improve the longevity of the paved street. A seal coat should be placed on a paved street every 8 to 10 years depending on weather, traffic load, and soil conditions.
Street overlays are necessary to rehabilitate the street surface and are generally used on arterial and collector streets to extend the design life an additional 10 – 12 years. Overlays are the primary full width maintenance activity for thoroughfares (2011 cost – $5.66/Sq Yard).
A small thickness of the street’s surface may be removed by milling and a new asphalt surface (typically 1” thick) is placed on top of the remains of the paved street. This operation will provide a new ride surface that is smoother than the older road surface and completely seals the surface of the street. The City of Amarillo’s; Street Department and Engineering Department coordinate together to prioritize which streets are recommended for a new surface overlay.
Major streets, commonly called collectors or arterials, are very difficult to Chip Seal because of the higher speeds and the high traffic volumes. The primary maintenance program for this category of streets is an Overlay Maintenance Program. The City typically budgets $900,000 each year for this maintenance activity. However, because there are over 590 lane miles of arterials and collector streets in Amarillo, spending $900,000 each year would take about 30 years to provide an overlay on each of these streets at current prices. To obtain the maximum benefit, these streets should be overlaid with a new surface about once every 10 years.