WSP Water Solutions

Wastewater Conveyance 

Carolina Trunk Sewer Tunnel Rehabilitation City of Portland Bureau of Environmental Services (BES) | Portland, Oregon ■ Rehabilitation of stormwater and combined sewer pipelines ■ Hydraulic modeling and capacity upgrades ■ Abandonment of existing trunk infrastructure The Carolina Trunk Rehabilitation Project is a critical wastewater conveyance initiative led by the City of Portland’s Bureau of Environmental Services (BES) to upgrade aging sewer infrastructure and prevent tunnel collapse in a dense urban corridor. The project focuses on rehabilitating stormwater and combined sewer pipelines, improving hydraulic capacity and abandoning trenchless and open-cut methods beneath interstates, requiring careful coordination to minimize public disruption. WSP serves as the prime design consultant, delivering design phase documentation, special provisions, cost estimates and design reports aligned with BES standards. Our team assists the City with infrastructure planning through infrastructure site reviews, location of planned tunnel access shafts, and strategized risk mitigation to address unknown underground conditions and maintain public mobility. outdated trunk infrastructure. Construction work includes

Bay Park Conveyance Nassau County Department of Public Works | Long Island, New York

Lower Meramec Tunnel Combined Sewage Overflow and Construction Services Metropolitan St. Louis Sewer District | St. Louis, Missouri ■ Critical infrastructure upgrade ■ Geotechnical investigations and hydraulic modeling ■ Stakeholder collaboration The Lower Meramec Tunnel (LMT), Missouri’s largest State Revolving Fund project, is a critical part of the Metropolitan St. Louis Sewer District’s 28-year Project Clear program. Spanning 7 miles with a 12-foot diameter, the tunnel houses an 8-foot conveyance pipe to improve water quality in the Meramec River watershed by intercepting flows and reducing reliance on other facilities. WSP led design and provided construction-phase engineering, addressing challenges like groundwater inflow, hazardous gas and karst geology. The tunnel, built entirely in rock, required integration with Phase I infrastructure and connecting sewers. WSP performed deep geotechnical investigations, geophysical studies, and optimized drop shaft and ventilation designs to mitigate environmental impacts. Hydraulic modeling using XPSWMM supported sizing and emergency planning. Collaboration with stakeholders ensured solutions for urban shaft construction and environmental concerns.

■ Repurposing historic infrastructure ■ Use of trenchless technology to minimize disruptions ■ Addressing water quality violations

The New York Department of Environmental Conservation and Nassau County entered into an administrative order that addressed water quality violations caused by the Bay Park Sewage Treatment Plant (BPSTP). Under this order, a feasibility study was conducted to eliminate the existing outfall to Reynolds Channel. A new ocean outfall was deemed cost-prohibitive, prompting an evaluation of the Sunrise Highway Drinking Water Aqueduct for effluent conveyance. Originally constructed in 1909, the aqueduct includes 83,500 feet of 72 inch Lock-Bar steel pipe. A structural assessment confirmed that the aqueduct was viable to repurpose and still comply with American Water Works Association M28 Class IV standards. Rehabilitation includes approximately 38,000 feet of aqueduct, using segmented sliplining with 60-inch fiberglass reinforced polymer mortar or cement mortar lined steel pipe. To minimize public disruption, trenchless technologies are employed, including 10,664 feet of 72-inch microtunneling from BPSTP to Sunrise Highway, and 8,307 feet to the Cedar Creek Water Pollution Control Plant (CCWPCP). The goal of this conveyance solution is to make cost-effective updates by leveraging existing infrastructure to meet evolving water quality compliance requirements.

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