Managing the Right Flow: Inflow + Infiltration 411

David Doxtad, PE
,
President
November 10, 2016

Picture this: You are a city leader responsible for assessing stormwater inflow and infiltration (I/I), and associated infrastructure costs and management. Do you push to implement disconnect programs that may come with added costs to homeowners or focus on increasing the capacity of the wastewater treatment plant? While this may seem like a silly question, older homes are having a large impact on the answer and cities are challenged to map the correct systems and solutions.

badhouse

Older homes are known for contributing I/I of stormwater to sanitary sewer systems through improper household foundation drains and/or sump pump drain connections. Leaky connections and manhole covers, cracked pipes, tree root intrusion, and other means also negatively impact their functionality. Essentially, I/I results in stormwater being treated as if it were sewage, when it could otherwise have been naturally absorbed into the ground in yards and gardens, or added to the storm sewer system that feeds ponds, rivers, and lakes.

Communities Burdened by Outdated Connections

While newer homes have sump pump and foundation drains that connect to sanitary sewer systems, most homes built before 1985 still have the old connections. Many people underestimate the impact of these outdated connections with the numbers telling the true story. Footing drains connected to sanitary sewer systems are suspected of being one of the leading causes of introducing excessive rainfall to sanitary sewer systems. Sump pump connections also cause significant and unnecessary flows and related costs. During a wet weather event, including substantial rain or snow melt, just ten sump pump connections can result in over 68,000 gallons extra flow per day, in addition to the usual daily flow. The increase in large rain events, combined with multiple improper connections, can overload systems resulting in failure and overflows.

Reducing I/I to Extend the Life of Infrastructure Systems

There have been a number of footing/foundation drain impact studies performed around the Midwest with relatively consistent results illustrating that these drains can contribute between one and five gallons per minute (gpm) during and following average rainfall events. This causes a significant strain on the wastewater system with increased quantity and costs for unnecessary treatment.

In response, updated building codes and city-run disconnect programs are achieving positive results by reducing the rate of unnecessary water from entering wastewater treatment plants. Roof, foundation, and sump pump drains that are properly connected from residential homes to the storm sewer system provide relief to sanitary sewer systems, city budgets, and ratepayers’ wallets.

Limiting stormwater from entering overloaded sanitary sewers can prevent raw sewage spills, reduce capacity requirements, and extend the life of the system.

What Can Communities Do?

A strategic and proactive community approach can save city staff and homeowners from burdensome and costly situations. By following these four simple steps, cities can support their communities and work toward managing a better flow and overall results.

  1. Develop a proactive approach by mapping the city’s sewer system with a Sewer System Evaluation Survey (SSES) and identify a lifecycle approach to address needs.
  2. Educate residents, property owners, city staff, and decision makers on the status and needs of the public infrastructure system.
  3. Implement and enforce drain disconnect programs.
  4. Develop a Capital Improvement Plan and budget for ongoing maintenance, replacement, and continual improvements.

Join the conversation #ISGCommunityPlanner  #CityInfrastructure #ISGPublicWorks

No items found.
David Doxtad, PE
President
More from
David Doxtad, PE

Related Articles

Drainage Water Recycling: Multi-Purpose Benefits for Producers, Crops, and the Areas They Impact

Throughout the Midwest, agricultural best management practices are ripe with opportunity and innovation, with new, targeted strategies to meet the evolving demands of modern farming while managing unpredictable weather.

Industry Insights

It's More Than A Vote

ISG believes the path to a successful yes vote doesn’t begin with a ballot. It begins with a story, a strategy, and the community.

Industry Insights

Ensuring Electrical Safety Through New Mandates: The Role of NFPA 70B Compliant Maintenance Programs

Maintaining, testing, and training are important elements of a successful electrical safety program for any facility. As of 2023, NFPA 70B, the Standard for Electrical Equipment Maintenance, has transitioned from a recommendation to an enforceable standard.

Industry Insights

Shared Waters, Shared Solutions: A Unified Approach to Stormwater in the City of Early, Iowa

When the City of Early reached out to ISG, they struggled with repeated failures in their stormwater system—challenges that weren’t confined to City limits.

Industry Insights

Market District: A Vision for Urban Living + Green Infrastructure

The Market District is redefining one downtown Des Moines neighborhood through a bold vision of mixed-use development that blends urban housing, green infrastructure, and vibrant public spaces.

Industry Insights

ISG’s Virtual Reality Technology

Virtual reality has increasingly become one of the most evolving technologies and is changing the way we perceive and interact with our world. To capitalize on this technology, ISG’s visualization team uses virtual reality to create computer generated environments that immerse users in a real-world interactive platform. This technology allows ISG’s clients to experience the design concept of their future space before shovels hit the ground.

Industry Insights