Custom-Built SRPE Storage System Handles Variety of Flows

July 7, 2020
Design for Washington lift station & welcome center overcomes system complexity, site constraints

Located in Pierce County, Wash., the city of Gig Harbor is a local mecca for tourism boasting an expansive history in the boat-building and commercial fishing community dating as far back as the 1800s, when its name was placed on the Wilkes 1841 map. While known for its fishing and boat-building, it is also an agricultural center, logging and lumber area, and Native American fishing ground.

The Problem

On September 6, 2016, the city began an extensive construction project to upgrade Lift Station 4 and build a new welcome plaza in Skansie Brothers Park. Lift Station 4 receives approximately a third of the city’s sewer flow, which is pumped to the nearby wastewater treatment plant. As part of the improvement to the welcome center and lift station, an expansion of the lift station was needed.

The Solution

The city selected Parametrix Inc. to be the consulting engineer for the project. Given the complexity of the system, tight site constraints and design requirements, Parametrix reached out to Contech Engineered Solutions for its assistance, as Parametrix was familiar with solutions provided by Contech and confident one that would meet the design requirements for this project easily could be identified.

Ultimately, a DuroMaxx steel-reinforced polyethylene (SRPE) storage system was selected. The system was designed so that the half round 16-in.-diameter low-flow channel at the invert of the 84-in. DuroMaxx SRPE storage system would handle the normal flow. The system was designed to provide excess storage in the event the main and backup pumping systems failed, such as during severe wet weather events. Should the flow rate exceed the capacity of the low-flow channel on those high-flow occasions, the 84-in DuroMaxx system then could manage the additional flow that the 16-in. pipe is not capable of conveying.

The low-flow channel is a unique aspect of this project. The half round pipe was pre-manufactured and installed into the 84-in. pipe at the plant to ensure the easy installation of the entire system upon arrival at the site. The DuroMaxx SRPE storage system was delivered in two pieces and welded together at the site by Stellar J Construction.

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“I enjoyed working with Contech staff to develop the design for this project,” said David Dinkuhn, P.E., senior consultant for Parametrix. “The problem was a bit unique and required a custom approach. The DuroMaxx pipe provided us with the storage volume we needed and fit within the tight confines of the project site. I’d say the project is a solid success.”

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