Report 2005-135 Summary - July 2006

California Department of Transportation: Although Encouraging Contractors to Use Recycled Materials in Its Highway Projects, Caltrans Collects Scant Data on Its Recycling and Solid Waste Diversion Efforts


Our review of the California Department of Transportation's (Caltrans) use of recycled aggregate in its highway construction projects found that:


The California Department of Transportation (Caltrans) designs, constructs, maintains, and operates the California State Highway System, including that part of the Interstate Highway System lying within state boundaries. Many Caltrans projects require aggregate materials--natural minerals such as sand, gravel, and crushed stones--commonly used as foundation material for constructing streets and highways. These materials are available in several forms, including "virgin" aggregate mined from gravel quarries, and recycled or reclaimed aggregate from building or road demolition. The California Department of Conservation expects that in 50 years the demand for aggregate will exceed the supply at sites with permits for mining aggregate in most regions of California, including highly urbanized regions. Fortunately, asphalt pavement and concrete waste materials can be recycled into aggregate, increasing the life span of existing aggregate resources. A study conducted for the California Integrated Waste Management Board (board), however, found that in 2003 almost 1 million tons of such waste material were disposed of in California's landfills.

Legislation passed in 1989 to encourage the maximum use of recycled materials, including aggregate, required Caltrans to review and modify all bid specifications for purchasing paving materials and base, subbase, and pervious backfill materials. This requirement was later incorporated into the Integrated Waste Management Act of 1989 (act), which intended to reduce the amount of waste materials disposed of in landfills. Although Caltrans does not generally see any impediments to using recycled aggregate in its construction projects and allows its contractors to use up to 100 percent recycled materials, it permits the contractors to decide when and to what extent recycled aggregate is more cost-effective than virgin aggregate. With no statutory requirement to report how much recycled aggregate is used, Caltrans does not collect these data and thus does not know how much recycled material its contractors use in highway construction projects.

However, to demonstrate compliance with a 1999 amendment to the act, Caltrans captures some data on how much waste construction material its contractors generate on its construction projects and divert away from landfills. This amendment requires all state agencies and large state facilities, which include Caltrans' 12 districts, to divert at least 25 percent and 50 percent of their solid waste from landfills or transformation facilities1 by January 1, 2002, and January 1, 2004, respectively. This amendment further requires each state agency and large state facility to report annually to the board on its progress in diverting solid waste during each calendar year.

To comply with the 1999 amendment, each Caltrans district submits an annual waste management report to the board, specifying amounts of solid waste generated for highway construction projects and amounts diverted from landfills. However, in reviewing the data the Caltrans' districts collected and reported to the board, we found that Caltrans did not report the solid waste generated on all of its construction projects and often could not support the data it did report. For its 2002 through 2004 annual reports, Caltrans generally reported the solid waste generated on only one project in each of its 12 districts. For its 2005 report, Caltrans intended to report the amount of solid waste generated and diverted away from landfills for all contracts advertised and awarded after November 2004. To capture these data, Caltrans required all project contractors to submit "diversion forms" that specify the amounts of diverted solid waste. However, we found that Caltrans did not ensure that all of its contractors submitted these forms. Further, some of its resident engineers responsible for collecting diversion forms either did not do so or did not forward the completed forms to the designated district coordinators, who summarize this information and report it to the board. As a result, the 2005 reports Caltrans' 12 districts submitted to the board accounted for only about 14 percent of the projects that should have been included in those reports.

Not only did Caltrans underreport projects to the board, but the data it did report also contained inaccuracies. From a sample of 30 projects, our review of the 28 projects for which Caltrans had diversion forms available found that Caltrans' resident engineers did not always review the forms and many forms contained errors. For example, resident engineers for 11 projects did not sign the diversion forms to indicate that they had reviewed them. In addition, the amounts of waste reported on diversion forms for nine projects were clearly inaccurate, with some diversion forms not accounting for the materials reused on the project. Although the diversion forms for the remaining projects did not have obvious quantity errors, the nature and complexity of construction activities often made it difficult to assess the completeness and accuracy of the reported quantities on most projects. Besides quantity errors, contractors included inconsistent information, such as reporting that they disposed of the materials in a landfill but giving the name of a recycling center as the location where they took the material. Finally, we also found that more than half of the diversion forms failed to specify the reporting period, reflected periods crossing calendar years, or included waste generated outside the applicable calendar year.


To ensure that its annual waste management reports on its diversion efforts to the board are complete and supported, Caltrans should:

Agency comments

Caltrans agreed with our recommendations and will take steps to implement them.
1 A facility whose principal function is to convert, combust, or otherwise process solid waste by incineration, pyrolysis, destructive distillation, or gasification, or to chemically or biologically process solid wastes, for the purpose of volume reduction, synthetic fuel production, or energy recovery.