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Case Study

Pima County Plant Interconnect

Pima County Plant Interconnect

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Project Title

The Regional Optimization Master Plan Plant Interconnect Project

Project Scope

Lining - 60 mils (elevated lining thickness due to service environment - gravity fed wastewater) and Coating - 25 mils of 2,400 Lineal Feet of 42” Welded Steel Sewer Pipe with DuraShield 210

Owner

Pima County Regional Wastewater Reclamation Department

Date Completed

2010

Partnering on a Wastewater Regional Optimization Master Plan led to a serious analysis of options and stringent test requirements. Result: Innovative and more reliable approach earned Department of Environmental Quality approval and saved $320K with DuraShield lined and coated welded steel pipe.

AWWA C222 industry standard compliant for interior and exterior of steel water pipe and fittings.

Twin siphon 42” welded steel pipe with DuraShield 210 lining and coating

Twin siphon 42” welded steel pipe with DuraShield 210 lining and coating

The Pima County Regional Wastewater Reclamation Department was tasked with creating a Regional Optimization Master Plan (ROMP) to forecast wastewater needs of their system through 2030. A portion of the plan was the Plant Interconnect Project, a 5-mile pipeline, consisting of 60-inch and 72-inch pipe, which included a critical section of 42-inch pipe that crossed two washbasins.

Brown and Caldwell was the engineering firm, Sundt-Kiewit (joint venture) was the contractor. The procurement method for the project was Construction Manager at Risk. This encouraged a tightly coordinated effort between the Owner, Contractor and Engineer to quickly and efficiently explore and design the most cost effective alternative to install the plant interconnect pipeline. The Wash Crossing design selection aimed to accomplish 100-year life, meet all regulatory requirements, provide low maintenance and low risk of failure, due to the service environment.

The engineer conducted a thorough survey of coating and lining options for Ductile Iron Pipe and Welded Steel Pipe using existing standards. Additionally, independent testing for 50% sulfuric acid immersion was analyzed. Finally, a cost comparison of the pipe material and coatings and linings was conducted. In the end, considering LifeLast DuraShield’s testing performance, wastewater performance history and a realized savings of $320,000, Welded Steel Pipe with DuraShield 210 lining and coating was selected. The Northwest Pipe Company, Denver Facility constructed the 42-inch twin siphons and applied DuraShield 210 at 60 mils on the lining and 25 mils on the coating.

42” welded steel pipe installation

42” welded steel pipe installation

After the value engineering effort was completed – including a stringent due diligence research of other jurisdictions experience with several of the proposed combinations – the Steel Pipe/DuraShield coating combination was selected for installation. After close coordination between the Pima County Regional Wastewater Management Department and LifeLast, a State Rule compliant set of specifications was developed and successfully submitted for an AZ Department of Environmental Quality exception to the State Rule covering the allowable material/coatings combinations for Wash Crossings.

Substantial cost savings were achieved by the combination of the Steel Pipe with DuraShield coatings”. — Jaime R. Rivera, PE Project Manager, Pima County Regional Wastewater Reclamation Department

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