Sewer System Master Planning – Tools in the Toolbox
Key reasons an infrastructure owner may need to perform a sewer system master plan are development within the service areas, customer reported deficiencies, or legislation (i.e. EPA Combined Sewer Overflow Long Term Control Plans). A sewer system master plan is often one of the first steps an owner takes so that the infrastructure upgrades can be budgeted appropriately for engineering design and construction.
While a master plan is not a small undertaking, with the help of a few tools the plan can be developed to convey complex information in a way that is easily digested by key stakeholders:
- Hydrologic and Hydraulic Modeling – Depending on the scope of the master plan, several software solutions exist ranging from simple (Microsoft Excel Spreadsheet) to more complex (XP-SWMM). These software solutions synthesize a wide range of user inputs to determine peak flow rates that are ultimately used to determine the size of the proposed infrastructure.
- Flow Metering – Having the feedback loop from sewer flow metering equipment is beneficial to compare to the sewer model, especially for areas that are difficult to project flow rates. When metering separate storm or combined sewers it is useful to capture at least three storms of 0.5-inch depth or greater to use in calibrating models. It’s also useful to capture metering data in separate sanitary sewers after rainfall events to determine if there is any unanticipated infiltration and inflow.
- Sewer Televising and Inspection – If one of the key drivers of your master plan is due to the age and condition of the infrastructure, sewer televising is often used to assess the operational and maintenance condition versus the structural condition. An owner may be able to save on infrastructure capital expenses if the televising shows that operational and maintenance procedures are the solution to restore integrity in the system. Owners may have their own equipment and personnel to inspect the sewers, or the owner may hire (either directly or through their consultant) a full-service sewer inspection contractor. Typically, operators are certified by the National Association of Sewer Service Companies (NASSCO). NASSCO has developed standard protocols for sewer infrastructure inspections which make the results more reliable.
These are just a few of the tools used to develop sewer master plans. If you have any questions or need help with a master plan, please contact Piper Tittle, PE, Chris Jeter, PE or Kevin Siedlecki, PE at (574) 234-3167.
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