LAREDO, TX — The City of Laredo is building a new sewer tunnel to divert wastewater flows from its existing Zacate Creek Wastewater Treatment Plant (WWTP).

The Zacate Creek WWTP receives and treats an average flow of 11 million gallons per day (MGD) from residential, commercial, and industrial areas. It is the city’s oldest plant and has high operational costs. The plant is also located in a flood plain. Consequently, the city is planning to phase out and decommission the plant.

The new 42-inch tunnel, which will span approximately 12,000 linear feet, will transfer approximately 7 MGD to the Southside WWTP. The tunnel will collect the wastewater flows coming into the Zacate WWTP plant and convey it to the 54-inch Chacon Creek interceptor. From the Chacon Creek interceptor, the wastewater flows will be conveyed to the city’s Southside WWTP for treatment. The capacity at the Southside WWTP is 18 MGD. Currently the city is only treating 7 MGD at the plant. When the tunnel project and the Manadas Creek WWTP, which is currently under construction, is completed, the Zacate Plant will be decommissioned.

“This tunnel is the most important part of closing the 60-plus-year-old Zacate Plant,” said Riazul Mia, Assistant City Manager at the City of Laredo.

The tunnel will be constructed under the Kansas South Railyard yard, around the city’s Slaughter Park, and over the Chacon Creek. The city wants to use alternative delivery methods to attract tunnel contractors who would implement innovative design and construction techniques that save costs and time. As the owner’s representative, Lockwood, Andrews & Newnam, Inc. (LAN) will provide technical concepts, oversee the project’s day-to-day operations, coordinate activities on-site, and resolve potential engineering issues. LAN will also help the city evaluate alternative delivery methods and develop a procurement plan that will address its near and long-term requirements.

“The tunnel project is a critical part of the city’s goals to implement an efficient wastewater system over the next decade,” said Tony Boyd, PE, LAN’s Senior Vice President. “The project will improve service to that region and significantly reduce operations and maintenance costs.”

The project’s contractor will be selected in fall 2021, and construction is scheduled to be completed in fall 2022.