Plan for Issaquah stormwater angers water district
Sammamish Plateau Water and Sewer District worries about a plan to treat Issaquah Highlands stormwater by filtering it into soil above a drinking-water aquifer
Seattle Times staff reporter
More than a decade and a half after construction began on the 7,000-resident Issaquah Highlands community, renewed conflict has erupted over how to handle the stormwater it generates.
The state Department of Ecology is on track to allow treatment of the water by filtering it through sand and gravel above an aquifer that provides drinking water to tens of thousands of area residents.
Officials at Ecology and the city of Issaquah say the plan — envisioned for years — is a safe, proven way of replenishing the aquifer and removing potentially harmful bacteria.
But the area’s largest water provider, the Sammamish Plateau Water and Sewer District, wants contaminants including fecal coliform removed before the water goes into the ground.
Jay Krauss, the district’s general manager, briefed reporters Monday on the district’s concerns about the purity of the water it provides to 54,000 customers in Sammamish, Issaquah and neighboring communities.
He said his district has offered to pay part of the cost of pretreatment of the rainfall that runs off 734 acres of homes, yards, businesses and roads, but city officials have shown no interest.
“The groundwater is at risk; there is a unilateral move on the part of the city to take us over and acquire the district, and the public needs to know what’s at risk with our water supply,” Krauss said.
Issaquah is considering acquiring the water district’s assets inside the city. Krauss suggested the city should instead spend its money on pretreatment of stormwater.
A draft permit that would allow the water to seep into the aquifer through an “infiltration gallery” of perforated underground pipes may be released for public review this month, said Ecology engineer Jerry Shervey.
Officials are still working out just how much, if any, bacteria would be permissible in monitoring wells that lie between the infiltration gallery and the water district’s wellfield, Shervey said.
The water would contain bacteria introduced by droppings from ducks, dogs and other animals, Shervey said, but those wastes would be removed as the water seeps through sand to the drinking-water aquifer.
“These types of systems are used in the city of Spokane, the city of Portland, and they’re both finding that their groundwater still meets drinking-water standards,” Shervey said.
The Sammamish Plateau water district contends the infiltrated stormwater should be held to a higher standard — that it cause no degradation to groundwater quality.
The no-degradation standard in state law isn't absolute, if other values — such as recharging an aquifer — are also at stake. Filtering stormwater into the ground is, in the long term, better for the aquifer and nearby Issaquah Creek, Shervey and Issaquah Mayor Ava Frisinger said.
The city and Ecology have long been committed to returning stormwater to the aquifer, offsetting other withdrawals of water that serve urban development.
Building an infiltration gallery, Frisinger said, was part of an attempt “to have a water balance that is as close as possible to predevelopment conditions.”
But the effort to replicate nature at Issaquah Highlands has run into problems over the past decade.
In 2004, saturated soils under stormwater detention ponds caused landslides below the urban village. And in 2008, after fecal coliform was found in monitoring wells, Ecology ordered an end to infiltration pending further study.
Since then, stormwater has been diverted into the north fork of Issaquah Creek, a practice the city and Ecology are eager to end.
Frisinger said Issaquah, which, like the Sammamish Plateau water district, draws water from the aquifer, is equally committed to clean water.
“We care about water for everyone, not just for Issaquah,” Frisinger said. “We in fact drink from the same glass, citizens of Issaquah and Sammamish.”
Krauss said water-district officials are concerned that the water-filtering sand above the drinking-water aquifer may not be as deep as Ecology believes — thus putting the aquifer in jeopardy.
He said he also believes the city’s current study of a possible buyout of the district’s assets within the city is intended to diminish the district’s influence over Ecology’s stormwater decision.
Frisinger said the possible acquisition reflects that cities “almost always” provide sewer and water service to their citizens. She also said the utility district’s opposition to in-ground filtration appeared to be based largely on a “jurisdictional concern.”
Keith Ervin: 206-464-2105 or firstname.lastname@example.org