skip to Main Content

20 Feet Under the Lake: The Tale of a Floating Pipeline Inspection

As seen above: CONSOR Dive Team members Travis Becker, EIT—a certified SSA diving supervisor (left)—and inspector-diver Blake Fogle (right) conduct safety measures and equipment checks prior to the dive.

In one of our first project collaborations since joining forces, Murraysmith construction management and wastewater engineering team members have been working closely with CONSOR’s marine inspection and structural engineering groups during the last few months on the Lake Oswego Interceptor System (LOIS) inspection.

This project is taking place under the surface of Oswego Lake where a buoyant and pile-supported sanitary sewer pipe system with near-shore manholes is suspended. Our multi-talented team is partnering with the City of Lake Oswego to complete inspection of the pipeline and, using the findings, will develop a Capital Improvement Plan to rehabilitate any deficiencies during the next lake draw-down in 2023.

Inspection equipment rests atop a barge on Oswego Lake.

To minimize impact to residents and lake users, the team is using 3D SoNAR imaging and multisensor tools to expedite inspection of the pipeline’s interior and exterior areas. Additionally, divers performed a hands-on inspection of all assessible underwater components comprising the pipeline system.

Marine Structural Assessment

CONSOR’s experienced dive team and marine structural assessment engineers led the exterior inspection of all near-shore manholes as well as buoyant and pile-supported portions of the LOIS including associated tethers, anchors, and fittings. Divers were out on the lake for 14 days, conducting three to four dives a day, each between two to three hours long. Below the surface, curious bluegill and smallmouth bass made frequent visits.

CONSOR Dive Team Leader, Andrew Cronin, PE, and Diving Supervisor Christopher Ryder work together to survey the conditions from the cabin of the boat using two-way radio to communicate with the diver below while live streaming the dive footage.

Partnering with a specialized dive crew from Advanced American Construction Inc., the team is currently focused on interior pipe inspection. Barges are used to access near-shore and submerged manholes, and aluminum tubes (called caissons) are lowered by crane and securely attached by the divers to underwater manholes. Once the water is pumped out of the caisson, inspection personnel can safely enter, remove the manhole cover, and get to work.

Caissons—the watertight retaining structures pictured above—are used to reach manholes below the lake’s surface. Cranes floated in by barge are used to lower the caisson and the water is pumped out of the structure to allow crews access to the chamber.

Construction Management

Murraysmith’s construction management (CM) group provides daily onsite management services during lake operations to confirm that all regulations are followed and operations are performed in a safe manner, and to routinely communicate with the contractors on the lake. Close coordination is required between the Murraysmith design team and CM team to control quality of the data collected, while being cognizant of production/budget/schedule.

Public Outreach

Strategic Communications and Planning firm, Barney & Worth—who joined Murraysmith in early 2020—is also a key player, supporting the City’s outreach efforts to keep mariners, lakeshore residents, and customers informed of inspection progress and wherabouts on the lake. Their outreach efforts include placing a story in the Lake Oswego Review and developing project FAQs, to coordinating regular project website and social media updates with Lake Oswego Corporation and other stakeholders.

In total, the team will have externally inspected over 15,000 feet of sewerline and 14 manholes, and internally inspected over 18,000 feet of sewerline and 27 manholes. Operations on the lake are expected to be complete by early January of 2022—a whole month earlier than originally planned! This project has been an exciting opportunity to pull in expertise from across our larger organization to better serve our public agency clients, and we can’t wait to get the crew together again for the next challenge.