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 based on their pavement condition index (PCI), 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 generally cost $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 20 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
What does PCI represent?
PCI stands for Pavement Condition Index. It is a numeric value that corresponds to the condition of a street’s asphalt pavement. PCI values range from a high of 100 for new streets to a low of 0 for streets that need reconstruction. The City regularly reviews the condition of all City streets and maintains the pavement information in a database that is used to prioritize pavement maintenance and rehabilitation.
When does the City slurry seal or overlay streets?*
Slurry seal treatments are used as a preventative maintenance measure and prolong the life of a street. Streets with a PCI of about 70 or greater are good candidates for slurry seal treatment. Slurry seal treatments make streets less susceptible to water intrusion and extend their useful life. They are a cost effective way to protect our public streets.
Pavement overlays are used as a rehabilitative measure and are generally used on streets with a PCI that has dropped to 60 or lower. Pavement overlay typically uses 1 ½ or 2 inches of new asphalt placed over the surface of treated streets.
*PCI is an important piece of information used in determining which streets are in need of pavement treatments but there are several other factors that are also considered. Those factors include traffic volume, ride quality and the condition of underlying utilities, among other factors.
The future of Livermore’s Roadways
The City of Livermore currently has about 305 centerline miles of streets to maintain. Each year the City has enough funding to overlay about 3 centerline miles of streets. Currently the average PCI for all streets is 77. To maintain our City’s overall relatively good PCI of 77 over the next 5 years, the City would need to increase expenditures on street maintenance from $3 million annually to about $6.8 million annually.
However, due to limited fixed funding resources, it is not possible increase the street maintenance funding by an additional $3 million annually in order to maintain the City streets present pavement condition that we all enjoy. As a result, over time the pavement condition for our streets will drop to a lower standard PCI as streets continue to deteriorate without additional funding to maintain our City streets present condition.
The Measure B Program, Alameda County’s sales tax for transportation purposes, will add a significant amount of new revenue for the maintenance of the City’s streets, bike, sidewalk and pedestrian facilities, if approved by the voters in the November 2014 election. The City of Livermore would receive approximately an additional $1 million annually in new revenue for our street, bicycle and pedestrian path maintenance. ore information on the Measure B Program.
If you have any questions about street resurfacing in the City of Livermore, please call the Engineering Division at (925) 960-4500 or email email@example.com.