Flooding concerns are delaying the construction of a new bridge over the Trinity River in Dallas.
A layer of sand instead of clay was found in the east levees, raising questions about how access ramps will be built.
Excavation for the support columns that went up for the link between Woodall Rodgers Freeway and West Dallas found the sand.
The state says the project is not canceled, but federal requirements could be slow and expensive. Engineers will need to study how much of a risk the sand is to the levees and find out how widespread the sand is, the Dallas Morning News reported Wednesday.
"So really the delay is the big unknown, how much of a delay we will have," Cynthia Northrop White, of the Texas Department of Transportation said.
Building the bridge piers in sand can create issues when they contract and expand with the weather, leaving ways for water to move into the levee system, the Dallas Morning News reported.
The U.S. Army Corp of Engineers recently rated the Dallas levees as "unacceptable." The levees protect huge portions of the city.
Civil engineer Tom Witherspoon says protecting the levees is the highest priority.
"When they breach, an earthen levee like this, it just rapidly erodes, and it could just devastate this whole area and the damage would just be enormous," he said.
Lesser floods, such as one three years ago, tested the levee system. The city says it is already working on improvements.
Meanwhile, contractors who have already hired to build the bridge may have to be paid, an issue White said the state is aware of.
The U.S. Army Corp of Engineers will release details on the problems it found with the levees by the end of this month.