A City of Tacoma investigation has determined that a side sewer line from the Tacoma Mall is connected to the Citys stormwater system instead of the wastewater system.
The stormwater line drains into a marshy area near Wapato Lake and ultimately seeps into the lake.
Mall management has worked with the City to aggressively address the problem. The flow of wastewater into the stormwater system has been stopped. Until the investigation is complete, the magnitude of the problem and length of time needed to make a permanent fix can’t be determined.
It appears that wastewater from the mall’s food court and a number of retail spaces was flowing into the wrong system. In the City system, wastewater flows through one system of pipes to treatment plants before it is released into Puget Sound. Stormwater goes into a different system of pipes before it goes into the Sound or other drainage.
The mall’s wastewater and stormwater lines and manhole structures are privately owned. They connect to the City’s system on the southeast corner of the mall property.
Further investigation is needed to determine how long wastewater was flowing from the mall into the stormwater system. The City last inspected the mall’s private system in 1992 and found no improper connections.
The problem was discovered during “inflow and infiltration” testing the City’s Public Works Environmental Services Source Control unit was doing to reduce the infiltration from the wastewater system into the stormwater system. This kind of testing was last done in the City more than 10 years ago. It takes more than a year to test the entire City system.
The problem with the mall lines was discovered Wednesday through a smoke test, when smoke was introduced into the wastewater system and began appearing in catch basins in the parking lots and roadway areas. A dye test Thursday morning confirmed that water from toilets is flushing into the stormwater system.
The mall owner is being officially notified by letter dated today (June 15). The City has notified the Tacoma-Pierce County Health Department and the state Department of Ecology.
