In mid-July we received a number of complaints of a sewage smell from just downstream of the TJ Meenach Bridge. We deployed our water quality monitoring team to make sure that the smell was not associated with harmful pathogens in the water that could infect river users.
We investigated and found the smell to be coming from the Cochrane Basin Combined Sewage Overflow (CSO) #12, which at the time was being worked on. The City of Spokane is installing large overflow tanks in each CSO basin to capture raw sewage that otherwise would flow into the river during heavy rain events. Installation of these 24 tanks is part of the Integrated Clean Water Plan, including upgrades to the wastewater treatment and installation of low impact development.
Water was flowing out of the large pipe behind a metal grate even though there had been no recent rainfall. We called in a complaint to the City of Spokane Wastewater Department, who explained to us that the smell was gas coming from the pipes and the water we saw was irrigation water that had found it's way into a storm drain.
The next day I returned to sample the outfall for fecal coliform. Fecal coliform is a bacteria that inhabits the gut of warm blooded animals. It's presence indicates waste from either mammals or birds in the water. A quick inspection of the pipe showed clear water that did not have a black bacterial sludge associated with it, as would be expected with raw sewage. Although the smell of sewage was strong, no other indicators of sewage was present. We grabbed a sample, making sure not to contaminate it, and put it on ice for transport to Anatek Labs in Spokane. The sample results of 4.5 bacteria/100mL were of a safe level for water recreation. Although it varies, anything over about 100 bacteria/100mL is considered unsafe for recreation.
In this case, the sample came back safe. Our water quality monitoring program in part aims to determine if local streams and rivers are safe to swim in. If a high sample does occur, we would report that on all of our social media, as well as contacting the city to investigate further. We would continue to sample until samples come back safe.