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Pavement Preservation Compendium II
Preserving Pavements and Budgets
California's Strategies Leverage Limited Funds
by Susan Massey and Pattie Pool
Pavement preservation is a priority in California, which is spending nearly $1 billion in 2003 to keep its highway system - the most heavily traveled in the nation - in working order. An effective pavement preservation program protects the taxpayer investment and improves user perceptions. Pavement preservation on the 50,000 lane-miles of California highways includes a range of preventive maintenance (PM) techniques applied to pavements in good condition.
PM strategies for flexible pavements include seal coats such as chip seals, slurry seals, microsurfacing, thin overlays, and crack sealing. PM treatments for concrete pavements include crack and joint sealing, dowel bar retrofit, partial depth slab repairs, and diamond grinding for smoothness and improved pavement texture.
These treatments reduce the amount of water infiltrating the pavement, slow the rate of deterioration, or correct surface roughness. Timely application can maintain or extend a pavement's service life another 5 to 10 years before a significant maintenance effort.
Retiring Distressed Lane-Miles
When resources are scarce, a policy of funding the worst pavement rehabilitation projects first will not retire enough distressed lane-miles to maintain a healthy state highway system. PM has restored more lane-miles at less cost per lane-mile than a rehabilitation-only program would have accomplished.
The 2003-2004 state fiscal year budget for pavement rehabilitation was nearly $300 million. To include some pavement preservation projects in that budget, a statewide rating system was used to allow projects normally covered in the Capital Preventive Maintenance (CAPM) program to compete with the worst roadway rehabilitation projects. Through the CAPM program, the California Department of Transportation (Caltrans) addresses projects in the category between maintenance contracts and full rehabilitation.
The option that targeted only the worst pavement rehabilitation projects would have retired only 326 lane-miles of distressed pavement. But the option that included the CAPM projects would retire more than 1,200 distressed lane-miles with the same budget, underscoring the effectiveness of pavement preservation. A mixed program of rehabilitation and preservation would include such strategies as preventive maintenance contracts, CAPM projects, nonconventional asphalt concrete treatments, and warranties to help maintain the state highway system through the budget crisis.
Budgeting for PM
Caltrans set a budget goal of $100 million annually for preventive maintenance: $50 million for state-funded maintenance projects and $50 million for federally funded CAPM projects. After several budget reductions in the 2002-2003 state fiscal year, Caltrans was able to secure $38 million for PM, adding service life to 1,635 lane-miles of pavement.
In the same state fiscal year, the pavement rehabilitation budget was $340 million, with approximately $30 million from CAPM program funds. Approximately 300 lane-miles were rehabilitated at a cost of less than $80,000 per lane-mile. In short, PM enabled Caltrans to leverage the reduced funds to restore more lane-miles than with dedicated funds. Typical preventive treatments include modified binder (rubberized and polymer-modified), asphalt overlays, chip seals, slurry seals, microsurfacing, thin bonded wearing course, and recycled materials.
According to the 2002 Pavement Condition Survey, candidate projects for PM represent approximately 15,000 of the 50,000 total lane-miles in the state highway system - that is, about 30 percent of the roads are already in good condition. The goal is to treat one-fifth of all PM locations in the first year, establishing a 5-year cycle for PM.
Budget cuts in the 2002-2003 state fiscal year, however, allowed allocations for only 60 percent of the targeted lane-miles. Nonetheless, earmarking part of the budget for PM has made it possible to keep up the overall condition of the state highways despite the rate of pavement deterioration.
Caltrans determined that for every $1 spent on PM, $3 can be saved on CAPM, $6 on rehabilitation, and $20 on reconstruction, if the treatment is applied at the right time. Reconstruction in urban areas has been more expensive than expected - instead of the originally estimated $500,000 per lane-mile, costs have exceeded $2 million per lane-mile.
The primary savings for PM comes from a reduction in the time spent on design and construction. Before PM, Caltrans performed as much corrective maintenance as the budget allowed, until full rehabilitation or reconstruction was necessary. PM projects, which involve pavement only, require less design time and can be delivered faster. Pavement surfaces are renovated with thinner treatments, contributing to faster production. Fewer construction working days reduce the disruption to the traveling public.
The one-year warranty provided another incentive for trying nonconventional asphalt concrete products for pavement preservation. The purpose of the warranty is to protect the pavement from failure during the first year after construction. The contractor must meet the performance requirements in the specifications.
In this way, the contractor assumes more responsibility for the materials and workmanship and must ensure a high-quality product free from defects for one year. Responsibility is placed on the contractor, not on the contracting agency.
When the nonconventional treatments were new, the warranty reduced the risk to the state if the performance criteria were not met. If there was a failure, the contractor had to come back and make repairs. A one-year warranty for performance covers such defects as rutting, potholes, raveling, flushing, streaking, and delamination; the financial impact on the Caltrans maintenance budget is minimal.
Although the California state budget is uncertain, the Caltrans Offices of Roadway Rehabilitation and Roadway Maintenance will continue to use pavement preservation and to dedicate funds to cost-effective PM treatments. Caltrans has relied on a combination of PM contracts, CAPM projects, nonconventional asphalt concrete treatments, and warranty projects to make the pavement budget go farther. Simple and more cost-effective PM treatments will maintain the highway system at a higher level of service, despite a reduced budget for maintenance and rehabilitation.
Massey is Supervising Transportation Engineer, Caltrans Office of Roadway Rehabilitation; Pool is Transportation Engineering Technician, Caltrans Pavement Management, Sacramento.
From TR News, September-October 2003, pp. 4-15. Copyright, Transportation Research Board (TRB), National Research Council, Washington, D.C. Reprinted with permission of TRB.