Using Stormwater Compliance to Drive Better Sewer System Planning

Using Stormwater Compliance to Drive Better Sewer System Planning

Just below the surface, our streets are literally bubbling with activity.  Pipes cross under, over or even through each other—carrying our drinking water, wastewater and stormwater drainage from our homes and businesses, along curblines, down rooftop downspouts and through sump pump connections. Yet, these pipes and the essential services they provide are often forgotten or at best underappreciated. In New England, the average sewer collection system pipe is around 90 years old and when pipes get old, they leak, break and collapse.

In New England, the focus on sanitary sewer collection system management is increasing with enforcement and new regulations. Recent changes to Massachusetts Sewer Regulations (314 CMR 12.00) are pressuring communities to pick up the pace on sewer collection system evaluations and reduce or eliminate their sanitary sewer overflows. Following suit, EPA Region 1 recently reissued its long-awaited Municipal Separate Storm Sewer System General Permit, which makes finding and eliminating sewage in drainage systems a top priority. 

 sewer and stormwater pipes

Stormwater and sewer pipes cross under, over or even through each other to get to their intended destination.

While the objective of both of these regulations is to manage sanitary sewer collection systems more effectively, the management of stormwater compliance programs is often in a separate division, department or district from conventional sewer programs—creating the potential for inefficient planning and implementation. My colleague, Zach Henderson, and I have been working with our clients to bridge this gap by developing integrated strategies that incorporate an inclusive understanding of both sewer and stormwater system investigation and maintenance needs. 

A better way forward: using drains to evaluate sewers

There are many ways sewer and stormwater systems can, and should, be managed together. For example, the extensive network of drainage pipes in a community can be an excellent entry point to rapidly identify leaks, breaks and other defects in sanitary sewer systems.

As with other more established sanitary sewer system evaluation techniques, such as flow monitoring and isolation, an effective sewer assessment program relies on key indicators to target further investigation. This approach reduces the labor-intensive follow-up investigations in pipes that may not need assessment. Using the drain system to identify and isolate areas of leaking (or cross-connected) sewer is an inexpensive and rapid assessment approach to identify problem areas. Like flow isolation, these rapid surface investigations can then be followed by more labor intensive and costly internal sewer system investigations.

These drainage system investigations are now required under the MS4 General Permit and should be an integrated and early component of any sewer system investigation program because it functions as a lead indicator of problems.

 

How a New England city located sewer weaknesses from the outside in 

One New England community was able to detect a wide-spread sewer problem during an initial analytical screening at a drainage discharge location. Bacterial indicators (E.coli) and surfactant (soap) concentrations, which are two of three reliable and inexpensive indicators of sewage in a drainage system, were 2,800%, and 1,200% higher respectively than the EPA’s benchmark concentration standard. At these concentrations, the idea of car wash runoff or raccoons living in the drainage system was not a possibility.

In response, the city kicked off a stormwater drainage system investigation which focused on rapid, surface-based grab sampling of the base flow at key junction manholes within the drainage system.  The investigation revealed several residential sanitary services that were directly connected to the stormwater drainage infrastructure and several suspected areas where the nearby sewer line could have  been indirectly contributing to the drainage network through exfiltration. In-pipe sewer system televising of those targeted pipe segments revealed groundwater infiltration, broken pipes and partial blockages—recipes for exfiltration from the sewer. Dye testing the sewer line confirmed an indirect connection to the nearby stormwater drainage system. Four redirected house services and 325 LF of 12-inch cured-in-place pipe later brought indicator pollutant concentrations at the discharge point to below threshold levels, protecting the environment and public health.

The city benefited from pinpointing a problem area in the sewer system by using rapid visual inspections of the stormwater pipe network—saving thousands in assessment costs. Additionally, the city benefited from identifying a 98-year old sewer line that was allowing an estimated 10 gpm of groundwater infiltration into the system and rehabilitating the pipe using CIPP trenchless technology that saved time, money, and impact to the area residents and businesses.

Developing an integrated strategy that incorporates an inclusive understanding of both sewer and stormwater system investigation and maintenance needs will maximize compliance and cost-savings while increasing transparency and effective management across departments. If you have any questions about sewer and stormwater integration, please contact me at jdemello@woodardcurran.com or Zach Henderson at zhenderson@woodardcurran.com

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Project Manager
Municipal Wastewater

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Zach Henderson
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