Washington Department of Transportation (WSDOT) I-90 Two-Way Transit and HOV Operations, Stage 3 Project

WSDOT and Sound Transit are adding HOV lanes to the outer roadways in both directions of I-90 between Seattle and Bellevue. This will preserve the existing general purpose lanes in each direction while improving traffic flow on I-90. The project also prepares the center roadway for Sound Transit’s 14-mile light rail extension.

Johansen Mechanical, Inc.’s Scope of Work for Stage 3 of this project, included the retrofitting of the Carbon Monoxide Monitoring Stations located in both directions I-90 Seattle-Mercer Island.

This involved the abandonment or removal of (15) fifteen existing CO monitoring stations along with the removal and modification of existing power and communication wire conductivity located at the roadbed’s level near along the Mount Baker and Mercer Island tunnels. As well as, installation of (9) nine NEW CO monitoring stations w/custom SS cover plates along the east and west bound utilidors along the 1,440 feet (440 m) tunnels.

The purpose of removing the existing CO stations and relocating the new stations to the utilidors are so that the service and maintenance of the equipment are accessible without shutting down the freeway systems and tunnels.

While most of the electrical conduits running to the existing CO systems were accessible and visible through the pan deck on this project. Tunnel Access to an MIT Sensor located approximately 50ft above the roadbed on the Westbound Mercer Island Tunnel was sealed off and inaccessible.

Access to this conduit was extremely important to determine whether or not the wiring was threaded via an LB electrical fitting or 90 degree sweeping elbow in the transition down to the roadbed. This would mean the difference between simply pulling the existing wiring through the 300ft conduit or if physical access to the conduit would be required.

In the event, physical access would be required. This would involve limited shut-down of the freeway, handling the logistics of transporting and installing scaffolding to access the above pan deck, and plasma cutting in order to gain access to the wiring transition.

However, an approximate 1ft opening in the pan deck was discovered 100ft across the tunnel from the existing conduit.

Johansen Mechanical’s Lead DDC Engineer, custom-built a robotic drone (known as Spidey) that was placed at the beginning of the opening and skillfully walked the customized drone across the pan deck to the conduit transition in question. This enabled visibility of an unforeseen wall, exposing the graceful sweeping elbow, just perfect for pulling wire. Use of this innovative technology saved days of labor and cost of materials to produce the same results.

What’s unique about this customized-drone is its ability to handle the long range without damage or abandonment. It’s (4) articulating legs made it less susceptible to the hazard of wheel wedging. Additionally, we installed a microprocessor to enable long-range transmission of data, obstacle avoidance capabilities and broaden the range of motion. Enhancements such as high-intensity LED lights and 3D camera for real-time visibility were mounted to the robot, to be used along with 3D goggles.