Update: Southwest Water Reclamation Facility Overflow
“We had close to two inches of rain in one hour that doubled the flows from the Southwest Water Reclamation facility from approximately 20 MGD to 42 MGD within 45 minutes.
This resulted in a short-term wave of water surge through the plant that would normally have been fully handled. However, because of the plant being under construction, half of the chlorine contact chamber was out of service for expansion during our fast-track construction.
The fast-moving nature of the plug flow of water caused 50,000 gallons of treated chlorinated water to spill from the chlorine contact chamber. The spill occurred on the SWWRF plant site where it was fully contained onsite.
We have no reports of discharges of raw or untreated wastewater anywhere in our system.
In consulting with Construction Manager Haskell, we are closely evaluating the event to determine how we will manage future fast-moving, short term flows through our plant while it is under construction. As is our practice, we are reviewing our operating procedures with staff to learn more.
We want to ensure that all protocols are followed and that new protocols are added as necessary.
The chlorine contact chamber was in full operation on Tuesday when we had our press conference. The Contractor began modifications to the existing chlorine contact chamber on Wednesday. In order to construct the planned improvements to the chlorine contact chamber, the Contractor took half the chamber offline, leaving the other half available to handle daily flows. Modification of the offline chamber began Wednesday for a 10-day rehabilitation.
The fast inflow of storm-related flow made it all the way through our treatment process to the chlorine contact chamber. The water received chlorination/disinfection before spilling over the sides of the chlorine contact tank in use.
Wet weather flow started entering the SWWRF at approximately 6:30 pm. We successfully treated and disposed of 1.0 M gallons of wet weather flow during a two hour period total two-hour flow was 3.7 M gallons). We then spilled 50,000 gallons of treated water over the contact chamber walls. We then regained full control of the wet weather flows and successfully managed the remaining 2.75 M gallons. (5.5M gallons of total flow over six hours)."