In the February edition of the City of Yelm’s Public Services Small Talk newsletter, Brad Chatwood, Yelm’s projects and programs manager, claimed that Cochrane Park has a path forward in regards to allowing more water outfall into the park.
On Friday, March 7, Chatwood said the city is working to identify what its treatment plan will look like in order to allow more reclaimed water to outfall at Cochrane Park. He said this will help with recharging the aquifer.
“I guess that could sound odd, but any water we outfall to Cochrane Park will go through the ponds and to rapid infiltration basins, through our natural treatment process, and ends up back in the aquifer,” Chatwood said. “What we want to make sure we’re doing correctly is putting the water that goes into the park at acceptable nitrogen levels to go back into the aquifer. (Washington State Department of) Ecology is asking us to sample, over the next year, not only from the park but a local resident well that is just upgradient of the park. We want to compare the two locations to indicate the biology of the water is basically the same.”
He added the city will use the sampling results from the private residency as a baseline of where Cochrane Park needs to be. The more important number from Cochrane’s sampling study, according to Chatwood, will be the water’s nitrogen levels. He said the Washington state Department of Ecology wants to determine what Cochrane Park’s nitrogen level should be before the water returns into the aquifer.
“At that point, once we have that determined level of nitrogen that we can put into the park, then we know what our treatment will have to be to make that happen,” Chatwood said. “This is a long term sampling process to make sure we’re doing the right thing environmentally-wise.”
Chatwood noted that the reclaimed water in the city is filtered through Yelm’s wastewater treatment plant, where it’s chlorinated, disinfected and then dechlorinated before it’s sent out for irrigation, to schools, city parks and outfall at Cochrane Park.
The city’s projects and programs manager noted that there is also an outfall pipe to the Nisqually River and canal if the city needs to get rid of excess reclaimed water.
“To some this may sound wild but this water is scrutinized closely to make sure it is clean for all of our outfall options,” Charwood said.
“We can’t always use it all. It goes through a process and gets treated, and then everything that goes to Cochrane Park is retreated again through a natural process,” Chatwood said. “As the water enters the park, it goes down the little waterfall that everybody sees. It also goes into the ponds, and that’s basically a natural process. The plants are eating up nitrogen, especially in the summertime. Eventually, the water goes to the rapid infiltration basins that are basically a large natural filter made of sand and rock.
“The best filter on the planet is the planet,” Chatwood said. “This all stems from us wanting to outfall more water to the park than we currently are.”
According to Chatwood, the work up to this point has been very minimal in cost to the city. He said once the project is at a point where there’s an idea of the treatment plan needed, then costs will begin to be incurred.
“We really don’t know what that is going to be for now. We do have some preliminary plans in place that we have engineered, which will be a good start,” Chatwood said. “For now, everything is just on hold until we have a solid yearlong analysis of the water. The only thing that’s costing us money right now is the sampling and analysis process itself.”
