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Notes on the construction of Boise’s Esther Simplot Park

After taking a tour of the Esther Simplot Park site Monday, I wanted to touch on a couple observations I had that didn’t fit into my Tuesday story on the debris and contamination crews found as they dug out the site.

First, workers are in full hustle mode over there. I don’t know that I’ve ever seen a construction site with so much happening in a relatively small space (55 acres, to be precise). Lots of earth moving equipment, trucks hauling dirt and debris from place to place, etc.

Please don’t take this to mean that McMillen, the general contractor on the job, is cutting safety corners. I’m not a heavy construction safety expert, but I saw no evidence that crews at the Esther Simplot site are taking risks in the name of getting work done fast.

Second, one of the complications with this park construction is the high water table. Because the park site is so close to the river, fresh water is seeping into areas with low elevations.

Here’s what McMillen has done to keep that water from flooding the whole site and to minimize contamination: They’re pumping the water from the spots where it’s springing up above ground into a series of pipes and a channel close to the northwest corner of the park site.

OK, so now you’ve got rid of the water. Where do you put it? The Boise River, of course. But how do you do that without contaminating the river? This is where it gets interesting – if you’re as fascinated with these processes as I am, anyhow.

A series of barriers have been placed along the surface of the water in the channel, which is probably a little less than 200 feet long. Those barriers slow down the current in the channel, turning the backwater of each one into a sort of pond. In each of these ponds, the solid particles suspended in the water settle out. The farther down the chain of ponds the water travels, the clearer it gets.

Here’s a quick video I took of the construction site and channel:

Before the water flows into the river, it empties into a pond just north of the channel. You’ll be familiar with this system if you’ve toured a sewer plant.

Boise Parks and Recreation spokeswoman Amy Stahl said experts have monitored the job site and found no contamination of the Boise River coming from it.

“The ponds address the sediment and any potential issues,” Boise environmental programs manager Catherine Chertudi said. “The water is continuously monitored by (McMillen). And (the Boise Department of) Public Works will regularly sample it as well. There are dense, compacted soils at depth, which help reduce any impacts to groundwater or the river.”