Experts disagree on Lemmon Valley flood water source

Published: Jun. 19, 2019 at 7:15 PM PDT
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Hydrologist Dave Thompson says he studied historical and current maps of the

area and determined 2017 was not a record year for precipitation.

The flooding, he said, was due to effluent from the Reno Stead Waste Water Treatment plant combined with development.

He testified the city gave no oversight as to what would happen to water at development sites except that it went into Swan Lake. He told the jury water increased the flood levels by more than 25%, or about one foot seven inches to the top of the lake.

Plaintiff attorney Roger Doyle asked, “On the properties based on your analysis, the flooding would have occurred earlier and deeper and would have lasted longer if the city's contribution had been part of the equation?”

“That's correct.” said Thompson.

Meteorologist Mike McMahon testified 2017 was the wettest year in the history of the basin. He based that on the total amount of rain falling in a short amount of time.

It all landed in a closed basin, he testified, where it had nowhere to go.

His findings came from analysis from NOAA and other atmospheric information going back decades. He told the jury there was more weather history as well.

“My second opinion is that the snowfall in the south range of 395 was also the highest amount recorded in that 40-year period,” McMahon.

Tuesday in court the plant manager of the Reno Stead Waste Treatment Plant testified from January 2017 to April 2017, the facility went over its capacity more than 76,000 minutes. That adds up to roughly 53 days.

That effluent all went into Swan Lake.

McMahon continues his testimony Thursday morning. He will be followed by a hydrologist who will testify on behalf of the city.

The jury could get this case as early as next Tuesday. In a civil case the decision does not have to be unanimous. 6 of the 8 jurors must be in agreement to reach a verdict.

Copyright KOLO-TV 2019