This design-build project consisted of replacing the original 15” VCP sanitary sewer mainline and underground service structures at Naval Station Great Lakes-Mainside. The work-site extended from the southwest corner of Ross Field to the far north end of Isherwood Avenue. The sanitary sewer serves the Training Support Center (TSC) on Naval Station Great Lakes.

Challenges Overcome

Many challenges were encountered over the course of project, including:

• This mainline sewer system served the vast majority of the mainside base. As such, no portion could be removed without immediate subsequent replacement and/or bypass. All santiary and stormwater sewer systems had to maintain 24/7/365 full functionality.

• Numerous existing underground structures, pipes, comms lines, and various obstructions were uncountered that were undocumented and unknown until identified during pot-holing and excavation.

• Several areas of unstable ground due to existing non-cohesive soils, and previosly installed fill materials which caused the ground outside of trench boxes to collapse.

• Presence of many conduits, piping, and structures left abandoned in-place, including asbestos wrapped steam lines, vaults, and tunnels that crossed directly above the sewer line to be replaced - occuring for over half the total distance of the project.

• The Covid-19 pandemic hit shortly after this project began, causing various challenges involving personnel availability and scheduling.

• Cross connections of existing sanitary and stormwater sewer lines.

• Several areas of existing durect bury communications lines and directionaly bored conduits.

In total, 3,618 LF of new SDR-26 sanitary sewer lines, over 200 service lateral connections consisting of 550 LF of SDR-26, 25 new pre-cast underground service structures, 260 LF of Cured-In-Place-Pipe (CIPP), and 290 LF of stormwater sewer lines were replaced and connected to the existing utility system. Over 65,500 SF of grounds were graded and topped with TACO Tier-1 top soil, seeded, and maintained until successfully established. Over 4,000 SF of new pedestrian concrete walkway, 180 LF of concrete road gutter and curbs, and 34,365 SF of new asphalt roads and parking lots were installed.