The water-retention ponds, sometimes referred to as ditches, along the sides of the newly constructed roadway of state Highway 75 south of Ketchum, performed as intended last winter and spring and the Idaho Transportation Department has decided they will not be altered.
“We have elected to leave them the way that they are,” Devin Rigby, district engineer for ITD District 4, said Thursday.
The Idaho Mountain Express has received a few inquiries from the public, mainly suggesting that the retention ponds were supposed to be removed and further suggesting that the ponds present a safety hazard in the event of a vehicle running or sliding off the highway. However, ITD never made a commitment to remove the ponds and announced as early as April that the ponds would remain.
Prior to making that decision, ITD had considered constructing a new system for storm-water retention along the new 3.25-mile section of highway, and as a second option considered adding fill material to lessen the slope and the depth of the ponds. However, building a new system would cost an estimated $1 million, taking away funding to build a new highway bridge across the Big Wood River near St. Luke’s Wood River hospital, a project currently in the developmental stages.
ITD officials discussed the situation with the Blaine County Regional Transportation Committee in January, and the general consensus among local officials who are members of the committee was to use the $1 million instead for the new bridge.
Rigby said Thursday that the second option of adding fill material to the retention ponds would lessen their effectiveness.
“We were able to review and see how they functioned last winter, and especially last spring, Rigby said. “We had at least half of the retention area completely full of water and the rest at least half full, so they did what they were supposed to do.
“Because of that, we are concerned about lessening any of the size with fill,” he said. “That would take away from their capacity to hold water, and it has to go somewhere.”
The retention ponds were constructed to hold highway storm-water runoff. ITD is required by federal law to retain storm water from the highway so that it does not contaminate nearby water resources.