The Sewerage and Water Board (SWBNO) has investigated the series of events that led to two drops in water pressure on Friday, Oct. 19 and Saturday, Oct. 20, respectively, resulting in the issuance of two precautionary boil water advisories.
This narrative is part of an ongoing effort by SWBNO to increase transparency and accurate accounting of its operations to its customers and the public.
The Carrollton Water Plant on Claiborne Avenue has eight pumps that distribute potable water to the East Bank of the City of New Orleans. There are no booster pumps or intermediate pumps in the system, so water must rely on the power of the pumps to travel from Carrollton to the furthest point in our service area, such as Venetian Isles, and everywhere in between. SWBNO runs four water pumps at all times with four reserve pumps on standby in case an issue arises.
Around 8 a.m.* Friday, SWBNO staff detected an oil leak in Pump A of the High Lift station at the Carrollton Water Plant. Operators worked to take it out of service and replace it with a reserve pump. Pump A, however, shut down before the reserve pump could be turned on, resulting in a drop in water pressure.
A gauge at Drainage Pumping Station 5 in the Lower 9th Ward detected a water pressure drop to 16.76 pounds per square inch (psi), which is below the new state standard of 20 psi. The Louisiana Department of Health (LDH) raised the minimum municipal water pressure from 15 psi to 20 psi on Aug. 1, 2018. These events would not have triggered boil water advisories under the previous state standard.
Consistent with LDH’s requirement and out of an abundance of caution, SWBNO staff contacted LDH on Friday, Oct. 19, and issued a precautionary boil water advisory for the Lower 9th Ward only.
SWBNO chemists began testing water quality samples around 3 p.m. that Friday. The samples were incubated to determine whether there was a presence of harmful bacteria in the water. On Saturday, during that incubation period, the Turbine 1 generator at the powerhouse at the Carrollton Water Plant experienced a voltage spike that caused turbines 1 and 4 to trip off line while power was being transferred from Turbine 4 to Turbine 1. Neither turbine generator was damaged in the event because the generators’ protection systems performed as designed. The cause of the voltage spike has been determined to be an unstable voltage regulator. Solutions to address it are under discussion.
That shutdown at 8:09 a.m. Saturday caused a loss of power to the water pumps, which led to low pressure readings on the East Bank. SWBNO staff turned on additional pumps and normal water pressure was restored at approximately 8:19 a.m. Water pressure, however, dropped below the 20 psi threshold at gauges at Drainage Pumping Station (DPS) 19 on the west side of the Industrial Canal; DPS 5 in the Lower 9th Ward; and DPS Jahnke in New Orleans East. Water pressure remained above the minimum threshold elsewhere in the City.
Turbine 5 generator was turned on, and all operations returned to normal by 8:35 a.m. Saturday. The approximately 25 minutes between the voltage spike and the start of Turbine 5 accounted for the time it takes to start one of these massive turbines. All five turbines at the Carrollton Plant are currently available.
The SWBNO is close to bringing into service one of two large water towers under construction at the Carrollton Plant. Its performance will help stabilize water pressure in the distribution system, giving SWBNO staff approximately 20 extra minutes to make any necessary adjustments to the power supply or pump equipment and reduce the frequency of future boil water advisories. The second water tower is scheduled to be completed in spring 2019.
SWBNO Operations Chiefs, in consultation with LDH, issued a precautionary boil water advisory on Saturday for all areas east of Franklin Avenue to protect public safety in the affected areas and to minimize the impact to as many homes and businesses on the East Bank as possible.
After water quality samples found the drinking water to be safe, and after again conferring with LDH, SWBNO lifted the boil water advisories for all areas of the City shortly before noon on Sunday, Oct. 21. Water Pump A is being scheduled for repairs.
* CORRECTION: A previous version of this article stated that the pressure drop at DPS 5 occurred at 1 p.m. Friday, Oct. 19. That pressure drop occurred around 8 a.m. A precautionary boil water advisory was issued shortly thereafter. SWBNO apologizes for the error.