E. coli contamination still a mystery four months later

by Lis Stewart, originally posted on December 3, 2016


NAMPA — Southwest District Health Department officials are still trying to figure out how nine privately-owned wells south of Nampa became contaminated with E. coli last summer.

“Unfortunately, this is a complicated situation and takes time,” Southwest District Health spokeswoman Laurie Boston wrote in an email to the Idaho Press-Tribune.

The health department reported six wells contaminated in August, and three more tested positive soon after. Most of the wells still had E. coli when they were last tested in September, Boston said. Due to privacy concerns, the health department will not release the exact locations of the contaminated wells, but Boston said they are in the area of Powerline Road and Locust Lane.

The wells are not owned by the city of Nampa.

Some tests performed in September are still being evaluated, while others were found to be inconclusive, according to a Dec. 1 update from Southwest District Health Environmental Health Director Brian Crawford.

With no recent tests, it is unclear how many wells are still contaminated.

The Department of Environmental Quality is assisting the health department in testing the water. Dean Ehlert, groundwater and remediation manager for DEQ’s Boise regional office, said the state is putting together a report intended to shed more light on the situation.

Public health officials say they must first determine the source of the contamination before mapping out a plan to treat the problem.


There are several potential sources of contamination, which Crawford said explains the length of time involved in pinpointing a specific cause.

It is unlikely that the source of contamination is the Nampa Fish Hatchery at 3101 S. Powerline Road, said Jami Delmore, Southwest District Health’s senior drinking water coordinator.

Aside from the fact that the hatchery pools are lined, the water pressure in the area goes the wrong direction because the hatchery is at a lower elevation.

 Also, Delmore said the aquifer under the hatchery and subdivisions, which is not under the same kind of pressure, flows away from the affected homes.

Crawford said additional and prolonged testing is needed to be certain, but there is no indication this is a long-term contamination. The water was likely contaminated from a recent occurrence or periodic event.


The major problem with figuring out how E. coli got into the water is the fact that those houses are built on highly porous, permeable volcanic rock, Crawford explained.

“With the lack of soil, there is minimal filtering of contaminants,” Crawford said. “Once the contaminated water hits the lava rock, there is no filtering, and it descends to the ground water.”

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