WSSC Adds Value, Mitigates Corrosion with Metallic Zinc-coated Ductile Iron


The Washington Suburban Sanitary Commission (WSSC) was established in 1918, the brainchild of public health officials and that era’s version of “civic activists.” A bond issue passed that year helped fund the system’s start and WSSC began acquiring existing water and sewerage systems within its service area – 95 square miles and 30,000 people.

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As the population grew, so did WSSC, with delivery of more water to meet its communities’ needs. Over the years, small existing community systems, some run by municipalities and others privately operated by land companies, were acquired and eventually integrated into the WSSC regional system. Reservoir facilities and dams were constructed, and new sections were added to the water supply distribution network to serve growing communities in the WSSC territory. Today, WSSC’s average daily potable water use in suburban Maryland is 167 million gallons.

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WSSC, which began with limited resources, has grown to a service area of approximately 1,000 sq-miles, housing a population of nearly 1.8 million residents.

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The Challenge

As WSSC’s beginnings date back nearly 100 years, the water and sanitary system had a great deal of pipe that was well past its useful life. Even predating WSSC’s foundation, some water and sewer lines in place in its territory were wooden pipe. Replacement was a necessity. The sheer amount of pipe required to do so meant that WSSC had to find a solution that would not burden its end users with inconvenience, and also provide a cost effective way for the system to reset the clock for its water infrastructure.

For such a solution, WSSC needed a partner that could meet both its specs, and also offer value added services to help with project analysis and management of the complex logistics needed to ensure a seamless delivery of products. Such a massive project also meant that WSSC needed to look beyond traditional practices in government procurement for cost effectiveness.

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For product, WSSC had some concerns about possible corrosion of the asphalt coated ductile iron pipe they had been using. Core & Main (formerly HD Supply Waterworks) had submitted – as a value added option – the use and pricing for metallic zinc coated ductile iron pipe. WSSC was interested in the benefits of zinc coatings and had seen results from the zinc coated pipes used in Great Britain and across Europe. WSSC wanted to extend the life of its new pipe, thus gaining as much as 50 years’ service life for the replacement pipe and helping to reduce both cost and inconvenience to residents for years to come.

The Solution

In 2014, WSSC requested proposals for a three year contract for its water system’s pipe replacement. The RFP went to ductile iron pipe manufacturers and waterworks distributors. Combined proposal packages were submitted. Prior to awarding the contract, WSSC had several meetings with the qualifying manufacturers and distributors to further review proposals.

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The final solution was a strategic partnership that combined WSSC’s innovative approach to both procurement and engineering of design, the dependable expertise and value added services offered by Core & Main, and the quality product provided by U.S. Pipe, whose manufacturing logistics and capability were just the edge to keep in step with WSSC’s needs.

WSSC’s ground breaking decision to move away from a government procurement practice of selecting vendors solely based on short term benefit and lowest price meant a more sustainable and long term cost savings for WSSC and its end users, in addition to gaining longer life for its system and benefitting generations to come.

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The distributor, Core & Main, has a national footprint that includes stocking locations with strategic proximity to WSSC’s service area. In addition to local distribution, Core & Main offered plan review, analysis, technical assistance and the logistical support of stocking and supplying materials, as needed, to the jobsites.

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WSSC made the decision to use metallic zinc coated ductile iron pipe, manufactured by U.S. Pipe, only a few months after giving Core & Main the contract and Notice to Proceed. The metallic zinc coating on the ductile iron pipe provides active corrosion control, and combined with a V BIO Enhanced Polyethylene Encasement, adds a level of active protection that works in concert with the zinc coating. It targets anaerobic bacteria activity and inhibits the formation of corrosion cells under the wrap. U.S. Pipe’s plan to zinc coat pipe at its Lynchburg Foundry added a second location for its zinc coating operation and improves the proximity to WSSC’s service area. This will allow for easier fulfillment of the 50 to 60 miles per year of water main replacement pipe.

Results & Benefits Cost Savings

Proactive, multi year agreement for long term replacement plan vs. a long expensive bidding process for each job by job need.

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Longer life of product/scale of economy purchasing the product, ductile iron zinc coated pipe with the V BIO poly wrap, has a longer life span than standard pipe. In addition, because a very large supply of the product is being purchased for a long term replacement schedule, the individual unit pricing is lower, thus resulting in an overall cost savings.

Product will be purchased directly from the distributor vs. purchasing on a job by job basis, thus driving operational efficiencies and reducing additional layers of handling costs, and as a government entity is the purchaser, there is no sales tax cost in WSSC’s territory.

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Supply and Logistical Ease

The manufacturer, U.S. Pipe, has three locations that supply zinc coated pipe, including the Lynchburg, Virginia plant (the location closest to WSSC’s territory), so that product demand can be easily met.

As ordering/distribution is being handled by Core & Main, the part numbers for the specific products that WSSC needs have been interchanged within HD Supply’s Online Advantage customer portal system. As jobs are scheduled, WSSC can use Online Advantage to easily locate their products online (by their own part numbers), and order what’s needed. Direct distribution is handled through local Core & Main sites conveniently located near potential job sites throughout WSSC’s service area.

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In addition to distributing pipe, Core & Main also stocks other products necessary for the WSSC job and will deliver those as well, such as fittings, repair clamps, hydrants, etc.

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Extended Life of Infrastructure

The service life of the pipe being used for replacement is extended due to the kind of pipe (metallic zinc coated ductile iron) used in conjunction with the V BIO polyethylene wrap. According to Mike Horton, U.S. Pipe corrosion expert, studies in Europe over the last few decades indicate that the combination of the metallic zinc coating of the pipe with the polyethylene wrap produces a synergistic corrosion protection system in that the zinc will protect the pipe if damage to the encasement is not repaired. The encasement will:

  1. Extend the life of the zinc;

  2. Enhance the development of zinc corrosion products as the zinc sacrifices itself;

  3. Create a homogeneous environment around the pipe with some biocidal characteristics; and

  4. Allow the zinc to be utilized in some severe environments where zinc coated pipe without polyethylene encasement may otherwise not be recommended.

Along with the durability of the zinc coated pipe, the V BIO polyethylene wrap has three layers of protection:

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  1. The outer layer, a light colored lower density material for UV resistance;

  2. The intermediate, thicker layer for toughness and enhancement of an inner biocide layer; and finally,

  3. The inner layer which is enhanced with a corrosion inhibitor and a biocide to address anaerobic bacteria associated with microbiologically influenced corrosion (MIC).

The V BIO wrap builds upon a proven method of corrosion control – polyethylene encasement – that has been protecting iron pipe from aggressive soils since it was first installed in 1958, making it a significant advancement in corrosion protection for ductile iron pipe. The technology provides for corrosion control of ductile iron pipe systems by creating a uniform environment where initial moisture will deoxygenate over time. As this deoxygenation occurs, the corrosion rates will migrate downward toward what is considered acceptable rates.

This article was contributed by the Washington Suburban Sanitary Commission, Core & Main and U.S. Pipe, a Forterra Company.

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