The Metropolitan St. Louis Sewer District is investigating why a force sewer main in Oakville keeps breaking.

Crews from MSD have finished cleanup after a second force main break happened last week at the same force main on Christopher Drive in Oakville that was previously broken, spilling more than 200,000 gallons of raw sewage into Sugar Creek, a tributary of the Mississippi River.

This time, about 300,000 gallons of sewage overflowed.

The break is near the intersection of Christopher Drive and Nellie Avenue in the southeast corner of Oakville, MSD said.

The latest break was discovered the morning of Dec. 17 after a property owner reported sewage in the area, MSD said.

MSD said its crews “quickly” responded, located the break and called in an emergency excavator to make repairs, working through the night. Work wrapped up Dec. 19.

Cleanup and disinfection followed.

This is the second break along this force main this fall. The last break happened while contractors were repairing the main after a small leak was discovered during a routine inspection by MSD staff. MSD said it will do a thorough investigation into the condition of the main and other factors to determine how to prevent additional breaks in the future.

MSD has reported the break to the Missouri Department of Natural Resources, as required by law.

Sewer service was not affected, but access to Christopher Drive around the break was restricted.

The sewer district posted warning signs in the area advising the public of the overflow.

MSD said there was no “immediate” threat to health or safety, but asked anyone in the area to steer clear of creeks and streams.

Anyone who comes into contact with sewage should wash thoroughly with soap and water.

A force main is a sewer line that uses pumps to transport wastewater. Pumps and force mains are necessary when gravity alone is not enough to move wastewater through flat areas or over hills to a wastewater treatment plant.