By Missy Schrott | firstname.lastname@example.org
Research for the Combined Sewer Overflow remediation project uncovered a mysterious cache of lead along the waterfront.
Alexandria’s combined sewer system has been a concern for decades. During heavy rains, a mixture of wastewater and stormwater runoff discharges through four combined sewer outfalls into the Potomac River. In April 2017, the Virginia General Assembly passed a bill requiring the outfalls be remediated by July 1, 2025 – a feat that will involve extensive excavation and reconstruction in Old Town.
Alexandria Renew Enterprises has taken the lead on the project through a program called RiverRenew. Since July 2018, the organization has been conducting a subsurface exploration program in preparation for constructing an underground tunnel system that will direct combined sewage to the AlexRenew wastewater treatment facility.
The subsurface exploration program has involved boring and collecting soil samples at 70 locations. It was during exploration at CSO-001, the outfall near Oronoco Bay Park, that RiverRenew came across the lead, according to Caitlin Feehan, program manager for RiverRenew.
After coming across the elevated levels of lead in the soil, RiverRenew conducted more borings to understand the size and scope of the impacted soil.
There are about 22,000 total cubic yards of soil – the size of about seven Olympic-sized pools – at the CSO-001 site that will need to be excavated to allow construction of the tunnel system. Of those 22,000 cubic yards, about 3 percent, or 660 cubic yards, is impacted by lead, Feehan said.
Because lead can be dangerous, RiverRenew is taking extra precautions to remove the impacted soil.
“When we found the lead-impacted soil, we took it a step further and are incorporating additional controls to handle the soil and further ensure that residents are not exposed to lead,” Feehan said.
The removal process for the band of lead will involve loading the soil into watertight soil bags, individually loading the bags into a lined truck bed, covering them with a tarp and tying down the tarp, Feehan said. The trucks carrying the impacted soil will go through two wheel-washes and be inspected before leaving the site. The trucks will then take the soil to a special landfill that will dispose of it.
It will take about one month and 75 truck loads to remove the impacted soil, Feehan said. Because RiverRenew would have been excavating the soil anyway, it does not impact the timeline of the CSO project.
RiverRenew informed the RiverRenew Stakeholder Advisory Group and the city council-AlexRenew workgroup of the lead discovery at meetings in December.
The information has prompted discussions about the lead’s origin.
“We got into a lively discussion about who would have done it? How long ago did they do it?” Yvonne Callahan, a member of the advisory group, said. “When was it done, who did it and why? It’s just kind of a very interesting speculative thing. … You don’t bury lead unless you know it was dangerous.”
City spokesman Craig Fifer said the city’s archaeology department has not been involved in the lead discovery.
Feehan said RiverRenew would need to do more research to understand its origin.
“It’s something that we’re trying to do more testing on to really understand what’s there, but it’s most likely from a previous manmade operation,” Feehan said.
Callahan said she is not concerned about lead exposure, especially after RiverRenew outlined its removal procedures.
“The fact that [RiverRenew has] number one, identified it and, two, knew pretty exactly how to get rid of it in a safe manner and where it needed to go, kind of took care of the problem. The issue is more ‘who done it.’ It’s kind of an interesting mystery,” Callahan said.
Construction for the CSO project will start in 2021, Feehan said. This particular site will be under construction from 2021 to 2024.