What You Need to Know: Water Supplies for New Development

While seemingly a small part of the overall scope of a large development, accurate water testing and modeling of infrastructure to support new development is critical to ensuring adequate water supplies are available without excessive costs.

A complete water supply analysis for a new development consists of three critical parts, testing and analysis of the pubic supplies, accurate estimations of the water needs of the development, and proper modeling of the water infrastructure associated with the development.

Determining the capacity of the existing water system

The first step is to determine the capacity of the public supplies.  This generally begins with obtaining flow test data.  Performing a hydrant flow test is a relatively simple procedure, and many jurisdictions will provide this information for free or for a minimal charge, but often this low-cost option comes with a hidden expense.  Many of the public personnel that perform flow testing on their system fail to understand the importance of the flow test data, tests are performed on the incorrect hydrants, an inadequate amount of water is flowed compounding errors, and the accuracy of these tests is often of concern as low cost, or poorly calibrated gauges are commonly utilized.  Even seemingly minor rounding of the results can often skew test data significantly.  These factors can result in increased costs to meet the water needs of the development or can result in overly optimist results that can cause an inadequate water supply once the underground infrastructure is complete.  Just as important as obtaining accurate test
data, is to fully analyze the public water system’s design and operation.  Water systems are dynamic systems, with demand and pressure changes that can have a significant impact on the available supply depending on conditions.  Because of this the results of testing must be adjusted to account for these affects.

Determining the developments water needs

The water needs for a single building with a known tenant is generally straightforward, but in most cases, determine the water needs for a large development are much more complex.  Modern developments often consist of multiple buildings, outlots, flex-buildings, and commonly a mix of residential, retail and office space.  In many cases few of the tenants are known in the early stages and the water needs are generally not well established at the preliminary stage when water infrastructure must be planned.  In addition to these difficulties, large developments can have a significant impact on the water supply due to the additional demand on the system, which can impact the available supply for any single building.  To accurately estimate the fire protection and domestic water needs of a development requires extensive experience in both fire protection and building plumbing systems, as well as an understanding of water system planning, future growth, and developed methodology to account for these factors.

Modeling of water infrastructure

Once an accurate and complete test is performed and the water requirements are established, the next step is to properly model the underground infrastructure for the development.  While simplistic calculations are sometimes adequate for single buildings with minimal underground piping, to properly analysis most underground piping infrastructure, computer-based modeling is required, to obtain the most accurate results.  By modeling the system this way different scenarios can be ran, pipe sizes can be changed, pipes and connections can be removed or added to determine the impact on the system.  By exploring these options, the most cost-effective design can be realized, with pipe size, and locations optimized to meet the needs of the development without excessive costs.   It is also critical to know any jurisdictional requirements that may exists, which can have an impact on how the underground infrastructure should be designed.

For more information on the requirements of specific jurisdictions and for help in meeting those requirements, contact us today at 636-398-5288 or at engineering@aiefirestl.com.

Contributed by Chad Lueders; October 4, 2018.

Leave a Reply

Your email address will not be published. Required fields are marked *