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Cabarrus County answers development questions with InfoWorks WS

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Courtesy of Innovyze

Untitled Document The Water and Sewer Authority of Cabarrus County in North Carolina (WSACC) supports five jurisdictions that lie within the same hydraulic basin: the county of Cabarrus, the cities of Concord and Kannapolis, and the towns of Harrisburg, Mount Pleasant and Midland. WSACC is the primary planning agent for water and sewer facilities in the area.


In 2004 WSACC started to use InfoWorks from Wallingford Software for modeling both its collection systems and water distribution networks. The first priority was the collection system, and a description of that work can be seen in the article WSACC gains the benefits of a common modeling platform with InfoWorks CS and WS.

Water distribution modeling became a top priority when a major new development was proposed for the town of Mount Pleasant. With an existing population of just over 1,200 people, a new development of 1,500 building lots would clearly cause a major impact on the water distribution system. Modeling was seen as the best way to answer the questions that were raised about water sources and the obvious issues of network capacity.

A water distribution model had been built for the WSACC 2000 Master Plan, using the company's previous modeling software. The AutoCAD data on which that model was based was imported into InfoWorks for the new model. However, there had been a number of changes to the network since the Master Plan, including the operations of valves and pumps, and how water was sourced. Operations engineers gave details of these changes to the modeler, checking that the new model was completely accurate and up-to-date. The demand figures were also re-calculated, using data on the changes in reservoir levels and population patterns.

The resulting new network model included all pipes of 6 inches and more, of which there were just over 200, plus all the pumps and valves together with their operational details. This model was then used for examining “what if” scenarios for the new development.

If the new development were to be built, it would clearly have a major impact on the network. Modeling results showed that in terms of pumping capacity, the second of two 500 gal/min pumps that was currently in standby mode would need to be deployed. Looking at all the options on increasing network capacity led to the decision that a new 12 inch main next to an existing main would be the optimal solution. At the same time a new mix of sources was identified for the new demand patterns. Finally, the model was used to examine fire hydrant capacities and identify where improvements would be required.

Since the first use of the model, it has been run for a number of analyses of new developments. Modeler Bhavana Sinha, EI, explained: “The model is now used whenever a new development is proposed, domestic or commercial. I can quickly look at the impacts and the options for addressing them, and I turn around each of these analyses in about a week of elapsed time. The InfoWorks modeling software is a powerful tool, which helps WSACC manage the cost of design and construction of additional infrastructure. This allows WSACC to keep its capital expenditures to a minimum providing a lower service rate for the customer.'

Bhavana also spoke of the benefits of using the same software suite for water distribution and wastewater modeling. “Although there are of course differences between the logic of water distribution and wastewater collection, it is immensely helpful having the same intuitive interface for both systems, both in terms of inputs and results. I can now undertake work that previously we had to contract out to consultants, and keeping it in-house delivers both financial and managerial benefits. InfoWorks is an essential part of WSACC now”.

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