State health officials point to isovanillin after Orange County water odor; investigation continues

Dwayne Roadcap, director of the Virginia Department of Health’s Office of Drinking Water, told the Orange County Board of Supervisors the department believes an isomer of vanillin — isovanillin — is the most likely cause of an objectionable odor that prompted a safety advisory in late August.

Roadcap, speaking by video conference, said the compound was detected at concentrations of about 8 to 10 parts per billion in taste‑and‑odor testing. He told the board that VDH’s toxicology review found limited data on isovanillin but noted that vanillin — a related compound the Food and Drug Administration lists as generally recognized as safe for food use — provides some context for the agency’s preliminary risk assessment. Roadcap said the chemicals detected (isovanillin, benzaldehyde and a single detection of BCE) at the concentrations observed would not cause short‑term health concerns.

"The reported concentration of isovanillin in the drinking water was 8 to 10 parts per billion," Roadcap said. "At this point we believe that isovanillin is the likely cause of the objectionable odor that the customers experienced." (Dwayne Roadcap, Director, Office of Drinking Water)

Tim Clemons, general manager of the Rapidan Service Authority (RSA), told the board that customer calls began Aug. 21 and that, after consulting with state partners, RSA issued a precautionary "do not use" order that day and later downgraded it to "do not drink" as additional testing came back. Clemons said multiple submersible pumps at the wet wells experienced failures (one between Aug. 19–20 and two others afterward), and repair contractors later characterized the failures as "catastrophic." RSA staff and contractors observed a slimy residue they believe to be mineral oil on submerged equipment in the wet well.

"We did go ahead and do that on the 21st," Clemons said of the do‑not‑use order, "out of an abundance of caution just because we weren't sure what people were smelling." (Tim Clemons, General Manager, Rapidan Service Authority)

Both officials described the investigation as ongoing. VDH said it had been posting daily incident updates on an online page and had sent samples to a national taste‑and‑odor expert for additional analysis. Roadcap said two primary investigative steps remained: additional wet‑well sampling (collected Sept. 9) and examination of pump components and coatings to determine whether burned materials could have produced the odor compounds.

Agency officials distinguished the acute odor event from a separate, longer‑standing concern about disinfection byproducts (DBPs) in the system, which they said RSA is also addressing through pilot filtration and regulatory notification procedures.

The board asked several questions about timing, the possibility of higher earlier concentrations, and whether field detections of hydrocarbons were false positives. Roadcap acknowledged early field equipment detections suggested hydrocarbons but said those were likely false positives from rushed field assays, and that laboratory and taste‑and‑odor expert work pointed to isovanillin as a more plausible cause.

RSA said it will not reinstall the submersible pumps until it can be assured the failures will not recur; RSA is operating with rental/diesel pumps and plans to pilot granular activated carbon filtration to address DBP concerns.

The health department said it will publish an investigative report when its review is complete and will release final findings and conclusions at that time.

The board did not take a formal vote on policy in tonight’s presentation; supervisors praised the cross‑agency cooperation and asked staff to continue regular public updates.