ITD Transporter

IDEQ completes review of
Mica Bay and Mica Creek study

The overall conclusions of the Mica Bay and Mica Creek Final Impact Assessment report are that, based on multiple lines of investigation, adverse impacts did not likely occur to Mica Bay, to fish resources or to recreational uses of the bay as a result of sediment from the U.S. 95 Bellgrove to Mica project.

Some Mica Bay property owners who use bay water did report problems with their intake systems.

It is likely that a portion of the sediment delivered to the South Fork Mica Creek from the project did deposit in low gradient reaches of the South Fork and mainstream Mica Creek.

The amount of sediment in the creek at this time does not indicate that the biological community or stream habitat were altered beyond the conditions found within the watershed. The findings from the multiple lines of investigation are discussed in detail in an April 2004 newsletter.

Primary study elements of the Mica Bay and Mica Creek assessment include:

•Hydrographic survey of Mica Bay
•Sediment coring and analysis
•Review of historical aerial photography
•Turbidity analysis
•Assessment of stream habitat and fish
•Evaluation of water intake systems
•Evaluation of recreation resource

Sediment from the construction of U.S. 95 from Bellgrove to Mica Creek in 2001-02 impacted Mica Creek, the South Fork of Mica Creek and fisheries, according to the Idaho Department of Environmental Quality (IDEQ).

The conclusions were based on a scientific study of the project and observations from the IDEQ staff.

During the 2001/02 winter, some construction problems were experienced related to storm water runoff issues on the project.

The Idaho Transportation Department and IDEQ formally agreed to study the possible impacts of the sediment in May 2003. A detailed methodology was approved by IDEQ to guide the comprehensive investigation.

The study included drilling sediment cores, underwater photography, analyzing fish resources and habitat, examining water turbidity and impacts to recreation and water intake systems.

The three-volume report was delivered to IDEQ in March and accepted in April.

The next step
IDEQ and the transportation department will jointly develop a draft corrective action plan for the identified impacts. The draft corrective action plan will be made available to the public for comment.

“We will use the plan to make the South Fork of Mica Creek a substantially better waterway,” Jim Ross, ITD chief engineer said. “It is our responsibility, when mistakes are made, to correct them quickly and to restore, and if possible, improve damaged areas.”

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