UNDERWATER WORK ON BRIDGE HITS SNAG

The underwater construction of the Bill Emerson Memorial Bridge has hit a snag that may set construction back two weeks.

Randy Hitt, MoDOT area engineer, said weak rock conditions and cracks in the solid rock underneath the site of pier 3 will require special attention before the underwater construction can begin.

Hitt said while finishing final drilling, cracks were found underneath of the bedrock along the edge of the pier site.

Eleven cores were taken to determine the consistency of the rock layers. Weak layers were found near the perimeter of where the 109-foot-by-67-foot steel caisson.

To support the outside of the structure during an earthquake, concrete must be inserted into the cracks or fissures.

"We can make these changes by making some modifications to the original design of the bridge," Hitt said.

The cracks or the weak layers will be filled in with cement grout.

During normal conditions the bridge will be able to withstand seven tons of pressure, but during an earthquake, pressure increases to 30 tons.

Hitt said with the modifications the weight of the new bridge will keep the foundation secure for a maximum force earthquake.