Potomac sewage spill: Repairs to take weeks longer after large rocks found in pipe

The blockage inside the collapsed sewer line that sent hundreds of millions of gallons of sewage into the Potomac River is worse than previously thought, and it’s going to take weeks longer to repair, DC Water officials said.

It will likely take an additional four to six weeks to get a system in place to safely remove large rocks and boulders crews found inside the sewer line during an overnight inspection, DC Water said in an update early Friday morning.

“Standard cleaning methods using industrial vacuums and jets are not sufficient to remove these large boulders,” DC Water said. “Addressing this blockage will require both larger machinery and manual labor. Workers will need to safely enter the pipe, use slings to maneuver around the rocks, and then rely on heavy equipment to extract each boulder, making removal a complex and highly specialized operation.”

The “large rock dam” stretches about 30 feet downstream of the original pipe collapse, the agency said.

According to DC Water, the rocks were likely excavated during the pipe’s construction in the 1960s and used as backfill. When the pipe failure happened last month, the rocks were drawn in by the force of the wastewater flow.

Then, as the surrounding material eroded into the sinkhole created by the collapse, extra rocks and soil accumulated and filled the pipe, helping create the rock dam.

DC Water said its bypass pump system near the spill has mostly contained the overflow of wastewater, but hasn’t stopped it. Reducing the flow of water through the pipe further means adding more of those pumps, DC Water said.

University of Maryland researchers say the spill spewed harmful bacteria as far as 10 miles downstream from the sewage overflow site.

The bacteria now in the Potomac River water, according to those UMD researchers, includes E. coli, the bacteria behind Staph infections and the antibiotic-resistant form of Staph known as MRSA.

To make matters worse, the cold water and outdoor temperatures are acting like a refrigerator, keeping the bacteria alive for longer as it travels downstream.

News4 Meteorologist Ryan Miller explained how the colder temperatures may be slowing the natural cleansing of the river from the spill.

“The water temperature right now is 39 degrees,” Miller told News4’s Mark Segraves. “That’s refrigerator temperature water. And that water will help to slow the growth of the bacteria, prevent the die-off, a massive die-off of the bacteria. So from that standpoint, the cold water can actually help transport further distances some of the pathogens.”

UMD officials urged anyone who comes in contact with the water to get tested.

DC Water is also conducting water quality sampling at multiple locations to check for E. coli bacteria, and also found elevated levels after the spill.

The spill took place below the point in the river where D.C.’s drinking water comes from, which means the D.C. water supply has not been impacted and is safe, according to DC Water.

It’s been more than two weeks since the sewer pipe collapsed on Jan. 19, causing 300 million gallons of sewage and wastewater to flow into the Potomac River.