Water Craft

Crews dive deep for Brighton’s Ken Mitchell Lakes Pump Station

The city of Brighton created a new lake storage system to help meet its water-rights obligations.

By Sheila Bacon

Laying 150 ft of pipe beneath the surface of a lake is not something most Colorado contractors do every day.

“We’re not the land of 10,000 lakes,” says Dawn Hessheimer, water resource specialist with the city of Brighton, where crews recently built river headgates, two wetwells and a control building to store surface water rights for the city.

Connell Resources of Fort Collins was one of six contractors involved in the construction of the $3-million Ken Mitchell Lakes Inlet/Outlet Facility. For its portion of the work, Connell crews laid the pipe in Ken Mitchell Lake using barges, excavators and divers – unique in a region with few bodies of water and even fewer contractors willing to attempt an underwater project.

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Connell crews used HDPE pipe, a more flexible type of pipe, instead of conventional PVC or ductile-iron pipe. That allowed crews to fuse the pipe together on land and pull it into place.

“Once the pipe is all put together, it’s like a snake,” says Dan Giesler, estimator and project manager with Connell Resources.

In addition to the 150 ft of pipe installed under water, 200 ft of pipe was placed at 22 ft deep on land. Instead of placing trench boxes and installing short lengths of pipe at a time, as is typical in most pipe-placing jobs, crews created an open cut and laid the pipe in long lengths. Without numerous connections, the risk of leaks was diminished.

Weights, fittings and a flared end-section were added to the underwaterportions of pipeline before it was submerged into the excavated ditch line.

Connell Resources placed excavators on an offshore barge to lay 150 ft of completed pipe onto the lake bottom. Divers checked grades, placed riprap, laid the pipe and assisted with backfill underneath the water. (Photo courtesy of Connell Resources)

Workers also dug a channel from the end of the underwater pipe 200 ft farther into the lake to connect the intake pipe to a deeper portion of the lake. Excavators were placed on an offshore barge, and divers were used to check grades, place riprap, lay pipe and assist in backfill beneath the water’s surface.

The project was completed in August.

Give and Take Brighton’s water comes from tributary groundwater wells, and because the city’s wells have fairly “junior” water rights, depletions from the well pumping must be augmented to the South Platte River to prevent injury to more “senior” water users. Primarily, the depletions from well pumping are replaced through wastewater return flows, water treatment plant concentrate, lawn irrigation return flows and system losses.

The city owns surface water rights to help meet the remaining obligation. During the summer, when excess surface water rights are not needed to meet the daily obligation, they are stored in one of two reservoirs. During the winter, when the ditch systems (surface waters) are not operating, the previously stored water is pumped to the river to meet those obligations.

Ken Mitchell Lake, formerly a mined-out gravel pit, was acquired by the city several years ago. The lake is the city’s second reservoir used to store surface water rights. A slurry wall was installed in 2006 as phase one of the project. The latest work was the job’s second and final phase.

Instead of placing trench boxes and installing short lengths of pipe one at a time, Connell crews made an open cut and laid 200 ft of pipe 22 ft deep on land. (Photo courtesy of Connell Resources)

Value Engineering The project was originally put out to bid as a single package, but its complexity seemed to confuse bidders, Hessheimer says. The city was adamant that the existing reservoir water not be drained, which meant any work would have to be performed underwater. In addition, the city requested that the work be done in the winter when the reservoir’s water level was at its lowest.

After receiving only three bids, the city reworked the project, dividing it into six separate contracts. The reworking extended the project’s timeframe, but drew bidders who were experts in their specialized fields.

Connell Resources, which held the project’s largest contract, offered the city a number of value-engineering options. Its suggestion to put a basement in the control building instead of routing pipe above ground eliminated more than a dozen 90-degree bends that would have required additional expensive fittings. This change, along with several material exchanges, saved the city $60,000.

But the change required a last-minute redesign of the control station. “It was a great idea that Dan (Giesler) presented to us, and we went with it,” Hessheimer says. “It shifted the size of our building, but it’s just as functional as it would have been before.”

Brighton’s decision to parse out the job to six different contractors meant it would be serving as the general contractor – a role previously unfamiliar to the city. The complex project was managed through weekly meetings of all participants.

“It was a hands-on job for us,” Hessheimer says.

Project Team
Brighton
Owner City of Brighton
Construction Manager/Design Engineer Industrial Facilities Engineering Inc., Morrison
Pipeline Contractor Connell Resources, Fort Collins
Site Work/Concrete Contractor J-2 Contracting Co., Greeley
Control Building Contractor W.M. Brown Construction, Denver
Electrical Contractor Kuchar Electric Co., Brighton
Mechanical Contractor Environmental Control Systems, Denver
Instrumentation and Controls Mountain Peak Controls Inc., Brighton
Pump Supplier Lee Mathews Equipment Inc., Denver