Record Rainfall and Severe Flooding Causes Wastewater Spill in Ten Mile Creek

Arlington - High velocity floodwater in Ten Mile Creek in southern Dallas and northern Ellis County causing major erosion, resulted in the collapse of creek banks and undermining of two sections of a 39-inch pipeline located near the creek bank. This pipeline transports wastewater to the Trinity River Authority’s Ten Mile Creek Regional Wastewater System treatment plant. The creek bank failure caused two sections of the pipeline to separate during the morning of July 1.

The eroded creek bank had been discovered by TRA on June 30 and the Authority had already directed a contractor to stabilize the pipeline. Before the contractor could move heavy equipment to the site to shore up the creek bank, approximately 16-feet of pipeline separated and collapsed into the creek.

At the location of the failure, the pipeline was transporting the wastewater flows from portions of Cedar Hill, DeSoto, Duncanville, and Lancaster, along with an even larger volume of storm water.

It has been estimated by TRA that a total of 1.89 million gallons of wastewater spilled into Ten Mile Creek before the outflow was stopped. The impact of this inadvertent spill was minimized by high floodwater in the creek, which during the ten plus hours of the overflow the creek flow ranged from a low of 70 million gallons per day to as high as 150 MGD, significantly diluted the untreated wastewater.

TRA constructed a temporary cofferdam to contain flow escaping from the broken line. The line was plugged upstream and downstream of the failure in order to completely eliminate flow into the creek. Crews worked through the night Thursday to complete the repair. Work will continue today to restabilize the creek bank.

Portions of the flow from Cedar Hill were diverted to another Authority treatment plant, which reduced the volume of wastewater. Diversion of the remaining flow was made to a second nearby pipeline, as quickly as possible, while repairs were underway. 

TRA began taking water quality samples to document conditions below the broken line immediately after the incident began. No impacts on water quality or fish and wildlife are expected to result from this spill because of the flooded condition of Ten Mile Creek that diluted the spilled wastewater.

Wastewater pipelines are built adjacent to streams and creeks to take advantage of gravity flow, instead of relying on lift stations and pressurized pipelines that require huge amounts of power to move water. TRA routinely monitors its pipelines during major rain events because of their proximity to creeks and had discovered creek bank erosion in the area the day before. Many erosion problems along Ten Mile Creek have been detected and stabilized prior to line failure during the 34-years this regional wastewater system has been in service.

FOR MORE INFORMATION CONTACT JOHN JADROSICH, TRA PUBLIC INFORMATION OFFICER AT (817) 467-4343.