Don’t tell Sarah Hill-Nelson that hitting rock bottom is a bad thing.
Hill-Nelson, a co-owner of the Lawrence-based Bowersock Mills & Power Co., was so pleased with finding rock bottom that she hosted an event for city officials Friday to celebrate the fact. Construction crews have finished digging an approximately 50-foot-deep hole for the company’s new hydroelectric power plant on the north bank of the Kansas River.
“It feels good to finally be going up,” Hill-Nelson said.
About a dozen city officials from various departments, along with Commissioner Mike Dever, toured the construction site at the north end of Kansas River bridges in downtown Lawrence.
“How deep is the hole?” was the first question yelled by City Manager David Corliss over the sounds of rushing water and humming construction equipment.
Deep, is the simple answer. From the top of the levee, it is a little more than 50 feet. Another way to think of it, though, is that construction crews working on the recently poured concrete slab are about 43 feet below the surface level of the Kansas River.
“It is probably the only time you would want to be that far below the Kansas River,” Hill-Nelson said.
Hill-Nelson told city leaders the $25 million project is still scheduled to open by December 2012. The new plant will be in addition to the company’s existing hydroelectric plant on the south bank of the Kansas River. Bowersock will use the two plants to produce electricity that will be bought by the Kansas City Board of Public Utilities in Kansas City, Kan.
The construction project is shaping up to be one of the most unusual in Lawrence history. Crews with Kissick Construction have had to build a large coffer dam around the site to basically move the river away from the construction zone. And, yes, the process has involved a lot of mud.
“It has been a long, hard fight, but we’ve finally gotten to the bottom of it,” said Matt Rothermel, a project manager for Kissick.
About 700 gallons of water per minute are flowing through a temporary construction pipe that dumps into the Kansas River. The pipe is collecting both groundwater and river water that is entering the site. Crews on Friday were wrapping the pipe with heat tape to ensure that it doesn’t freeze shut during the winter.
Stephen Hill — an owner of the company that dates back to his great-grandfather Justin D. Bowersock — said the project is a feat of engineering.
“We have told our engineers that this building has to be here for a minimum of two centuries, and we really mean that,” Hill said.
“It definitely will be here that long,” Rothermel said.
Some interesting facts about the project include:
l Hill-Nelson said the completed building will stand a bit taller than the Kansas River bridges. Hill-Nelson said the building will be about as tall as a tower — the one that previously has been connected to a cable that runs across the river — at the north end of the bridge.
l If the Kansas River rises dramatically during the construction project, crews would be forced to flood their construction zone before the river topped the temporary coffer dam surrounding the site. A controlled flooding of the construction area — rather than the river suddenly topping the dam — would ensure the temporary dam would remain standing.
“We could pump it out and get back to work, but it is a delay we really don’t want to have,” Hill-Nelson said.
l Once crews hit the bedrock surface at the bottom of the hole, they drove anchors 18 feet deep into the shale. A 3-foot-thick layer of concrete — about 900 yards — will be poured on top of the anchors and serve as the foundation for the building.
“That will stop the building from twisting and turning and moving,” Rothermel told the crowd.
“For how long?” Hill yelled from the crowd.
“That’s what I wanted to hear,” Hill said.