Water resources warn temporary pretreatment systems must remain as reservoirs shed sediment after storm Helene

City water resources staff told Asheville City Council June 5 that temporary pretreatment systems installed after Tropical Storm Helene remain necessary to protect the water treatment plants at North Fork and DeBruel, and that the city faces elevated sediment and turbidity risks until permanent solutions are built.

Clay Chandler, water resources staff, said the U.S. Army Corps of Engineers installed temporary pretreatment systems to reduce turbidity at both North Fork and DeBruel and that “these temporary systems provide a critical layer of resilience at both of the treatment facilities.” Chandler said the Corps’ original lease was extended 90 days and that the lease termination is now set for early August.

Chandler reviewed engineering analysis showing large canopy losses in the two watersheds. He said North Fork experienced about a 15% canopy loss and that the watershed could see roughly a 20‑times increase in sediment entering the reservoir during the first year after the storm (dropping to about four times in the second year, absent further storm events). He said DeBruel experienced roughly a 35% canopy loss and that its watershed could see up to a 50‑times increase in sediment the first year (dropping to nine times the second year if no additional events occur). Chandler said recorded turbidity values immediately after Helene reached roughly 90 NTU at North Fork and approached 500 NTU at Beech Tree in some areas, compared with normal readings of about 0.1–0.5 NTU.

Chandler said that if the DAF pretreatment systems become unavailable and the city must shut down existing filtration systems to avoid damage, the temporary units would have to meet 100% of customer demand. He warned that without those units, “80% of the water system — basically everything north of the Blue Ridge Parkway — will begin to lose service within 24 hours,” and that North Fork could be forced to send highly chlorinated raw water into the distribution system, requiring a boil‑water notice.

Chandler said staff planned to post a request for proposals to assume management of the DAF units and would continue coordinating with FEMA and state partners to seek funding and to design and build permanent pretreatment systems. He said both the temporary and proposed permanent system projects have been submitted to FEMA for review as potential Public Assistance reimbursements.

Council members thanked staff for the update. Council member Rodney (full name not specified on the record) said he looked forward to “good news on approval of a permanent solution,” and several council members expressed appreciation for the Corps’ work and for staff efforts to stabilize service.

City staff said they would continue to press federal and state partners on funding and to pursue a local procurement path for continued operation of the temporary systems until permanent treatment is delivered.