Gresham Smith Engineers Eight Miles of Sewer Improvements in Guam

September 17, 2020

Gresham Smith is proud to announce that the newly rehabilitated Route 3 Interceptor Sewer has restored integrity and added capacity in Guam, adequately supporting the northern district’s population growth, which includes 5,000 deployed U.S. Marines. Working as a sub-consultant to JV Core Tech-Hawaiian Dredging Construction Company (CT-HD) and local engineering firm Duenas, Camacho and Associates (DCA) as part of a progressive design-build effort funded by the U.S. Department of Defense (DoD), the Gresham Smith team designed trenchless improvements to approximately 45,000 linear feet – over eight miles – of large diameter gravity interceptor sewer line as part of the Guam Waterworks Authority (GWA) Refurbishment Project in the Northern District.

“Sewers are out of sight, out of mind underground assets that deteriorate over time and eventually fail if they’re not maintained. We understand how important wastewater conveyance is to keeping communities healthy and resilient, which is why Gresham Smith was so proud to work on this project for the people of Guam,” said Ken Stewart, P.E., Vice President at Gresham Smith. “Through our partnership with GWA and local design partner, our team was already familiar with the unique challenges of an island environment and the details of Guam’s infrastructure, and had experience integrating GWA’s goals into efficient and cost-effective design solutions, which helped us create an operationally efficient sewer system.”

The existing sewer infrastructure serves the northern part of Guam, including Andersen Air Force Base (AAFB) and Finegayan, and conveys wastewater to the Northern District Wastewater Treatment Plant. Due to its age, the system was experiencing failures and blockages that were causing groundwater infiltration and inflow and ultimately compromising the integrity of the sewer line. The rehabilitation was required correct those issues and to support DoD’s new Marine Corps base, Camp Blaz, which is currently under construction.

Leveraging extensive sewer rehabilitation design experience, the Gresham Smith team used a topographic survey of the project area, geographic information system (GIS) data, closed-circuit television video and software generated reports to provide comprehensive designs. The final design solution included epoxy coating the interior of manholes and rehabilitating 18- to 42-inch sewer lines using ultraviolet (UV) light cured-in-place-pipe (CIPP), a process that requires minimal water, which is a vital resource for Guam. The improvements restore the structural integrity of the sewer system, maintaining  conveyance and protecting Guam’s groundwater supply.

This project is a continuation of Gresham Smith’s partnership with Guam Waterworks Authority. The firm previously designed the Agat-Santa Rita Wastewater Treatment Plant which is completed and has been fully operational for over a year. Also, the firm served as the overall design manager as well as liquid processes for upgrade and expansion to the Northern District Wastewater Treatment Plant which is currently under construction. These projects are in partnership with the local Guam consulting firm, Duenas, Camacho and Associates.