California culvert inspection program
California Department of Transportation
GPS receivers and data loggers allow Caltrans to conduct statewide condition assessment of highway culverts.
When Manuel Morales was hired as a senior transportation engineer and head of the culvert inspection program for the California Department of Transportation (Caltrans), he knew he would be responsible for bringing consistency to the state’s culvert maintenance program. What he didn’t know was that he was embarking on a 15-year project that would ultimately save the state hundreds of millions of dollars. But that’s exactly what is happening. Morales and his team are six years and 24,000 culverts into a statewide mapping project that will ultimately provide a detailed overview of California’s culvert network.
It all started in the late 1990s when a San Diego culvert failed, closing part of an interstate highway. "Prior to the San Diego incident, each of Caltrans’ 12 districts had their own method of tracking the location and condition of culverts," said Morales. "Some districts kept track of culvert data in an Excel spreadsheet, some took notes and kept them in a three-ring binder, and others stored the data in the heads of the guys who had worked there the longest. Collectively, we had no idea of the condition of the state’s culverts, or even where most of them were located."
When culverts fail, repairing sinkholes, washed-away roads, and erosion can cost millions of dollars, in addition to the inconvenience and lost productivity of having major state highways closed for repair.
When culverts fail, as in the San Diego case, repairing sinkholes, washed-away roads, and erosion can cost millions of dollars, in addition to the inconvenience and lost productivity of having major state highways closed for repair. Because many of the state’s culverts were reaching the end of their 50-year lifespan, Caltrans officials then requested—and received—funding from the California legislature to implement a culvert management program. The program was designed to provide consistent reporting across all districts and to mitigate damage caused by culvert failure.
Initially, Caltrans officials implemented a two-year pilot program in four districts to study what it would take to implement a statewide culvert inspection program. The pilot program team decided to incorporate the paperless procedure already in use by District 2, based in Redding. The Redding team was using a Trimble GPS receiver and handheld data logger with Trimble TerraSync and GPS Pathfinder Office software to map and record culvert data. Using GPS Pathfinder Office software, the team created a data dictionary, which provided consistent fields to be populated by field engineers.
Once the data dictionary was complete, field teams would map the exact location of each culvert’s components using a lightweight, handheld Trimble GPS receiver. In June 2001, the engineers used Trimble GPS receivers to begin mapping the location of all culvert features throughout the district, including all drainage inlets, manholes, discontinuations in the pipes, junctions, and other attributes.
Using GPS receivers and data loggers, Caltrans field engineers assess each culvert’s condition, noting deterioration of culvert material, joints, shape, alignment, and waterway capacity.
In addition to logging each culvert’s location, the inspectors used the data dictionary to record the culvert type, physical dimensions, and material. An assessment of each culvert’s condition was also made by evaluating different culvert components, such as the deterioration of culvert material, joints, shape, alignment, and waterway capacity.
Each day, the field team downloaded the information onto a desktop computer and differentially corrected the field data for improved position accuracy. Using Trimble GPS Pathfinder Office software, engineers could create a visual representation of the day’s work.
Field teams map the exact location of culvert features, including drainage inlets, manholes, discontinuations in the pipes, junctions, and other attributes.
"The pilot program was a huge success. For the first time, we were beginning to keep a spatially accurate record of all of our culvert features, as well as detailed information about each feature’s condition," said Morales. "After a big rain, we knew exactly which culverts needed to be re-checked, and we knew which held the highest priority for repair. Suddenly, we were able to monitor the condition of our culverts and repair those in need before roads were washed away."
Following the pilot’s success, Morales and his team requested additional funding to implement the program statewide. In 2005, Caltrans received perpetual funding for a comprehensive, statewide culvert maintenance program. Since then, Caltrans teams have begun using Trimble GeoXT GPS handheld receivers—integrated rugged GPS receivers and data collectors—to map their culvert networks statewide. Each district has received the technology, training, and guidance necessary for the culvert mapping initiative. Engineering technicians are now developing a comprehensive database of the state’s culvert system.
"Each day, our engineers are inspecting the condition of our culverts across the state. So far, we have mapped more than 24,000 culverts; of those, we know that 70 percent are in great shape, and more than 10 percent are in need of major repair," said Morales. "We already have teams of engineers working on the culverts most needing repair, and I’m sure we have already prevented some major culvert failures across the state."
Today, all of the state’s culvert data is stored in one centralized GIS where Morales can access maps, drawings, and reports about the condition of California’s culverts. "Now, I can pull up a color-coded drawing that will show me exactly where our most troublesome culverts are throughout the state," said Morales. "We can use that information to make important decisions about culvert repair and maintenance."
Morales predicts it will take his team approximately 15 years to collect data about every culvert feature in the state. "We’re already seeing a five-to-one return on investment and we’ve just scratched the surface of this project," said Morales. "My goal is to prevent the state of California from ever having another catastrophic culvert failure."
Ron Bisio is director of marketing, Mapping & GIS Division, at Trimble. He can be contacted at firstname.lastname@example.org.