Report 99113 Summary - August 1999

Department of Transportation: Disregarding Early Warnings Has Caused Millions of Dollars to Be Spent Correcting Century Freeway Design Flaws


After nearly 30 years of controversy, court injunctions, and delays, the California Department of Transportation (CalTrans) opened the Century Freeway in Los Angeles County in October 1993. In March 1995, problems again arose for the freeway when, less than two years after the opening, CalTrans discovered cracking and sunken sections in the shoulder areas of the freeway that it had constructed below ground level. Although it originally thought the problems involved maintenance issues, by January 1996 CalTrans became aware that matters were far worse: it had not designed the lowered section of the freeway to compensate sufficiently for the effects of rising groundwater beneath the pavement.

During the planning, design, and construction phases for the Century Freeway, CalTrans disregarded warning signs that could have prevented design flaws in the freeway's 3.5-mile lowered section. Most significantly, CalTrans disregarded the 1968 recommendation of its staff to test extensively the soils and the groundwater levels in the area planned for the lowered section, even when it designed the modified storm-drain system for the freeway in 1973. Further, in late 1981, CalTrans agreed to extend the length of the lowered section of the freeway west toward the Los Angeles River, and the department apparently designed this extension without adequate research and consideration, such as additional testing of the soil and groundwater conditions in the area. If CalTrans had performed these tests, it could have realized the rising groundwater would threaten the freeway as designed, and it could have taken appropriate steps early in the project.

CalTrans has documents from 1987 showing that groundwater levels had risen substantially between 1985 and 1987 in the area planned for the below ground level section of the freeway. However, because this analysis was for determining bridge foundations, it was not sent to the district unit designing the lowered section. During construction of the drain system for the lowered section in July 1990, CalTrans installed four dewatering wells because it was encountering a lot of water. The ground was so wet that CalTrans halted construction for more than six weeks. Another six years passed before CalTrans realized it had a serious groundwater problem.

While CalTrans was struggling to move forward with the Century Freeway project, another agency was taking action that was to have important consequences for the freeway. The freeway crosses over two groundwater basins. By the 1950s, the groundwater of these basins had been overpumped, reducing available groundwater supplies while demand for groundwater was increasing. As part of the effort to restore the health of the groundwater basins, a water replenishment district was established in 1959 to return water to the basins. By early 1997, the groundwater levels had increased over 30 feet. Although the groundwater replenishment involves all the geological layers, those layers closest to the surface, which are about 25 feet below grade, are the ones affecting the lowered section of the Century Freeway.

CalTrans may have pushed ahead without further analyzing groundwater conditions because it was under some pressure to begin construction of the freeway after the 1981 lifting of a court injunction that had halted progress for many years. To qualify for federal highway funding for this project, CalTrans had to meet certain construction deadlines.

In January 1996, once CalTrans acknowledged that the cracking and sinking were more than ongoing maintenance problems, it spent $22 million in emergency repairs and planned to use another $45 million for permanent repairs to the drainage system. CalTrans engaged both in-house engineers and outside consultants from academia and private practice to evaluate the underlying causes of the problems and develop options to resolve them.

Although it is working to remedy the situation, CalTrans must still determine what it will do with the groundwater it pumps from beneath the freeway. As of May 1999, CalTrans had paid, under protest, more than $370,000 in taxes to pump out the groundwater. The department is currently diverting the water into the Los Angeles and San Gabriel rivers: thus the water is not available for other uses. CalTrans is, on the other hand, reviewing proposals with two local cities to find beneficial uses for the extracted water so that it does not waste the water or undermine the efforts of the local water replenishment district. Because CalTrans has not determined the best resolution to the groundwater disposal problem, it has no firm estimates of the costs related to the reuse of the extracted water. However, preliminary estimates suggest that the additional costs could be more than $50 million for initial costs and from $370,000 to $5 million in annual costs.

In responding to concerns that CalTrans withheld information about the problems it was experiencing on the Century Freeway, CalTrans acknowledged it could have done more to inform the Legislature. However, CalTrans did include some information related to the Century Freeway problems in its normal communications with local legislators, the public, and the California Transportation Commission.

Since the groundwater problems became apparent, CalTrans has reassessed some of its policies and procedures and convened an in-house review of the circumstances leading to the problems at the lowered section of the Century Freeway. The review panel made numerous recommendations for new or revised procedures and most units have responded appropriately. However, CalTrans has not monitored some units, which were slow to implement changes.


CalTrans should inform the Legislature, through its Senate and Assembly Transportation committees, as well as the California Transportation Commission about the department's progress in determining an environmentally sound and cost-effective method for reusing the groundwater pumped from under the Century Freeway.

CalTrans should continue working with the Water Replenishment District of Southern California to coordinate actions so that neither agency jeopardizes the other's efforts to fulfill its organizational mission.

To ensure that it properly puts into practice the recommendations from special in-house staff reports, CalTrans should ensure that the unit designated to implement these recommendations periodically reports its progress to department management.


The Business, Transportation and Housing Agency and CalTrans agreed with our recommendations. In addition, the department suggested several wording changes to the draft report. We have accepted some of the department's suggestions in developing our final report.