Background
About the Advisory and the City's Response
On Nov. 30, 2019, at the state's direction the City of Poway issued a precautionary boil water advisory following a heavy rain event that caused some stormwater overflow into part of the City’s drinking water system. The boil water advisory ended Friday, Dec. 6 when water samples confirmed the ongoing safety of Poway water. All testing conducted during that seven-day period confirmed the safety of the drinking water and the water system; however, it was important to follow state regulatory procedures, which called for a series of tests and water quality confirmation.
The event began on Friday, Nov. 29, following days of heavy rain, when the city Public Works department received five calls from residents reporting discolored water. Though city offices were closed for the Thanksgiving holiday, the Public Works after hours response team was immediately dispatched to test the water at each of the five residences. Tests for chlorine residuals, which is an important water quality indicator, at these residences as well as other sampling points in the Poway water distribution system found the water to be well within health standards.
However, since the water discoloration appeared to be citywide, out of an abundance of caution, Poway water officials notified the State Water Resources Control Board and all parties determined a precautionary boil water advisory was in the best interest of our community. Customers were quickly notified of the advisory through the county’s reverse 911 system and multiple other channels, including an alert to business customers in the water billing database. As part of the state’s notification process, the county’s department of Environmental Health issued closure notices to Poway food establishments. The city set up two distribution points to provide bottled water to its water customers and distributed 117,850 gallons of water.
The specific cause of the discoloration was a storm drain that backed up into our water treatment facility’s clearwell reservoir during storm. These facilities have been in place for more than 50 years and are regularly inspected, including as recently as fall 2019. The City promptly secured the stormwater outlet to eliminate any future backflow occurrences and flushed the water distribution system to ensure all pipelines are in proper condition.
Timeline
Friday 11/29: Public Works receives calls from water customers and send after hours response team to test water at residences. Chlorine residuals, an important factor in water quality, were well within health standards. Turbidity, which has to do with clarity, was high. Public Works set out to determine source of the discoloration.
Saturday 11/30: Crews complete an extensive examination of the City's water distribution system to identify and isolate the source of the discoloration. A storm drain attached to the clearwell reservoir at the water treatment facility was identified as the source of the discoloration. Chlorine residuals were still within standards; turbidity was still high. The City contacted the state and a precautionary boil water advisory was issued. At about 6 p.m. the advisory was finalized, and notification went out to residents.
Sunday 12/1: Public Works secured the storm drain outlet. The City set up a bottled water distribution site at Lake Poway for Poway water customers and delivered water to residents who needed assistance.
Monday 12/2: The City began draining the north section of the reservoir in order to isolate the area affected and disinfect it. A second bottled water distribution site was set up at City Hall.
Tuesday 12/3: The clearwell was disinfected and refilled. The City was able to share testing results showing Poway water continues to meet health standards as two certified test results taken since the incident began showed that the water is absent of bacteria. An update was provided by Public Works at the City Council meeting.
Wednesday 12/4: Water samples were collected for the first of two state-required tests. The City followed state protocol for testing and reporting information, which required two water sample collections 24 hours apart taken the day after the clear well was disinfected and refilled. In addition to the state-required test, the City received its third certified testing results that the water continued to meet health standards.
Thursday 12/5: The City collected the second round of water samples required by the state (to be collected 24 hours after the first samples). City also received certified results from Wednesday’s required tests, which showed that Poway water continued to meet health standards. These results were forwarded to state for review.
Friday 12/6: At 5 p.m. the City received the second round of state-required test results. These certified results showed that Poway water continued to meet health standards. (Read complete testing results.) Results were sent to the state for review and at 6 p.m. the state approved the cancellation of the advisory.
Back to top