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An internal assessment by Danville Utilities and the city of Danville of events that led to and followed the recent boil water advisory incident has determined that the water treatment plant and plant operators performed to their capabilities.
However, equipment needs were identified that will enhance treatment and better monitor turbid water. In addition, measures were pinpointed to better notify and disseminate information to key water users and the general public in the event of future incidents.
“It is understood that this (advisory) caused considerable anxiety on the part of the general public, inconvenience and expense for all, and a loss of business by many restaurants and other commercial establishment s,” City Manager Joe King said. “We genuinely regret this and will do our upmost to avoid such events in the future.”
The Virginia Department of Health, in conjunction with the Danville Health Department and Danville Utilities, issued a boil water advisory during the late afternoon on March 26 when the water treatment plant – following heavy rainfall over preceding days – continued to experience difficulty in treating the raw water taken from the Dan River, and as a result the city’s storage capacity of treated water fell short.
King noted that the boil water advisory was only a precautionary measure intended to address a potential water quality threat. Once an advisory is issued, testing of the water quality must be conducted for at least 48 hours before an advisory can be lifted. The advisory was lifted on the morning of March 29.
All tests conducted throughout the duration of the advisory showed the water to be safe.
“It is clear that no water treatment plant inadequacies, facility failures or operator failings caused this incident,” King said. “If anything, plant operators and the Virginia Department of Health erred on the side of caution in issuing the advisory.”
The city has issued boil water advisories in the past for neighborhoods affected by low pressure due to water line breaks. This incident prompted the first citywide advisory.
Barry Dunkley, director of water and wastewater treatment for Danville Utilities, said water treatment can be difficult following any heavy rainfall because of sediments washed into the river. The sediments can force operators to shut down the water treatment plant for short periods of time, as was necessary prior to and during this incident.
During these periods, the city relies on two large finished water storage tanks at Ballou Park to supply water to customers.
“The Ballou Park large storage capacity had provided sufficient time in the past to allow operators to adjust to the difficult water quality while the plant was shut down,” Dunkley said.
Dunkley said a raw water impoundment or retention pond, such as one used by the city of Eden, N.C., would best prevent sediments from entering the treatment plant. However, an impoundment is not economically feasible.
He said a large capacity mobile pump should be acquired to allow water and solids to be separated more quickly and, as a result, shorten the amount of time in which the plant is shut down.
In addition, other equipment could be purchased to provide earlier knowledge of changing river water conditions and more quickly detect water quality changes during the treatment process.
The internal assessment also pinpointed measures to better notify and disseminate information to key water users and the general public.
“Local news media outlets did an outstanding job helping get information out on the boil water advisory and how the situation could be handled by the public,” King said. “However, there were several aspects of the public notification process undertaken by city staff on March 26 that could have been improved upon.”
All large and special needs water users should have received advance alert that conditions may require issuance of a boil water advisory. For the general public and media, the initial boil water advisory should have included consumer information regarding food preparation, general hygiene and pets.
King said a call center should have been activated to handle calls from the public about the water situation.
He also said the city’s “Reverse 9-1-1” system should be replaced with one capable of handling citywide calls and use of social media. The current system works well for small area alerts, but is not effective for larger events.
Procedures also were identified to provide updates to large water users and the general public, including daily media conferences.