New Water Intake | City of Ashland | Ashland, WI

Project Data
​Owner: City of Ashland
Engineer: TYLin
Contract amount: $10 million
Category: Underwater Pipeline, Cofferdams, Diving, Water Treatment Plant
Year Completed: 2025

Roen Salvage was the prime contractor on a contract with the City of Ashland to install a 24” ductile iron water intake pipe starting from an onshore underground connection and finish 4,400 feet offshore in Lake Superior.

Prior to construction, Roen Salvage surveyors performed a hydrographic survey of the lakebed along the planned pipeline route.  This survey data was then used to plan the exact grade changes and fittings needed to complete the work. These planned grades were then imported into the RTK positioning system on Roen's barge. Guided by this positioning system, a trench was dredged to the varying target grades with a clamshell bucket. Bedding stone was transported by barge to the site and then placed in the trench.

With diver assistance, sections of pipe were laid in the trench and adjusted to the proper depth. Each pipe position setting was verified to the nearest tenth of a foot.

The pipe sections were incrementally covered with bedding stone, anchor stone, and lastly native dredged material to restore the lakebed back to the original grade. Final grades were verified by Roen's hydrographic surveyors.

Three underwater concrete manholes were installed along pipeline for maintenance access.

A 100,000 pound intake crib was prefabricated by Roen in Sturgeon Bay, Wisconsin and barged to the job site. The crib was set by Roen's crane and installed underwater at the end of the pipeline.

Two 1-1/4” HDPE pipes were pulled from onshore, through the pipeline, to the intake crib for the new pre-chlorination system.

A turbidity control system was designed, installed, and maintained throughout the project by Roen Salvage. Roen deployed real time turbidity monitors to verify the effectiveness of the control measures, and to monitor the water quality at the existing intake.

A temporary steel sheet pile cofferdam was designed and installed by Roen in order to connect to the on-shore pipeline.
 
The finished pipeline and underwater structures were inspected with an ROV.

Onshore subcontractor work installed new yard piping to connect the new offshore intake pipe to the existing water treatment plant system. This work included upgrades to the water treatment plant to integrate the new pre-chlorination system.