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Smarter Stormwater Collection

Turning your stormwater collection network into a smarter one - the ultimate guide


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CSO/SSO Application Note

Everything you need to start transforming your stormwater network into a smarter one.

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There are about 3.5 million miles of storm sewers in the U.S.

If you operate, own or regulate a stormwater collection network, you are well familiar with the challenges of ensuring the operational aspects of your network. The network is a combination of older and newer parts, with thousands of different parts that need to work together to ensure the efficiency, safety, and regulatory compliance of the stormwater collection operations.

And that's not all; the inherent complexity of the operation is supercharged by the aging infrastructure, the increased operational stress, changing weather patterns, and the dramatic development of the regulatory framework.

The combination of the above conditions, and the fact that many networks are still operated in almost the same way they were decades ago, gives rise to a systematic problem across the stormwater collection networks - the current way of doing things is not sufficient anymore. A more modern approach needs to be developed and implemented. And in its core, there is one major theme - to anchor all decisions with data. Make better decisions and increase operational efficiency by utilizing the power of data across your network.


Stormwater is rainwater plus anything the rain carries along with it. As rainwater runs across different surfaces, it can pick up various types of pollutants including:

  • sediment from exposed soil
  • oil and grease from driveways and roads
  • leaves and animal droppings that collect in gutters
  • chemicals from lawns and gardens.

Every time it rains, water runs off impermeable surfaces (that can't absorb water), such as roofs or driveways, collecting pollutants such as particles of dirt, fertilizer, chemicals, oil, garbage, and bacteria along the way. The pollutant-laden water enters storm drains untreated and flows directly to nearby streams and ponds. The US EPA estimates that pollutants carried by rainwater runoff account for 70% of all water pollution.

Impervious surfaces can cause several environmental problems:

  • Impervious surfaces can increase the amount and speed of stormwater runoff, which can alter natural stream flow and pollute aquatic habitats.
  • Impervious surfaces limit the amount of precipitation that can soak into the soil and replenish groundwater supplies, which are an important source of drinking water in some communities.
  • Impervious surfaces that replace soil and plants remove the environment’s natural ability to absorb and break down airborne pollutants.

According to the U.S. Environmental Protection Agency (EPA), the presence of roads, rooftops, and other impervious surfaces in urban areas means a typical city block generates more than five times more runoff than a forested area of the same size.


Stormwater is the only growing source of water pollution in many waterways across the US. With urban populations expected to grow to nearly 70 percent by 2050, and more frequent and intense storms occurring across the country, there is ever-increasing pressure on stormwater systems and water infrastructure.

Stormwater running over rural land or from our catchment towns can pick up a range of pollutants:

  • dissolved chemicals from various sources including pesticides and herbicides
  • waste from livestock and pets
  • sewerage and effluent from falling onsite wastewater treatment systems
  • soil from plowed paddocks, eroded land, or construction sites.

Stormwater can also:

  • alter river flows
  • change flooding patterns
  • increase flow velocity, turbidity, erosion
  • affect the availability of water for irrigation.

Even plant seeds can cause problems, particularly if the stormwater also contains high levels of nutrients. Weeds can be spread downstream to neighboring properties, bushland areas, and national parks in the drinking water catchment.

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Combined Sewer Overflow (CSO)--Combined sewer systems are sewer systems that collect both stormwater runoff and sanitary sewage in the same pipe to be carried to a wastewater treatment plant.

Wet weather events can sometimes cause these combined sewer systems to exceed their hydraulic capacity and result in a combined sewer overflow (CSO). A CSO can result in untreated human and industrial waste, toxic materials and debris being discharged to nearby streams, rivers, lakes or estuaries, impacting water quality and aquatic habitat. CSOs can cause beach closings, shellfishing restrictions and other water body impairments.


Of course, weather and climate are primary factors, but did you know that stormwater utilities are not distributed evenly across the US? Some states have many, while others have few or none. In some states, legislation can make it more difficult to establish a stormwater utility. Fee structure types follow a regional pattern where a fee structure dominates the region. 

The University of North Carolina has mapped Stormwater Utility Locations in the US.  Based on this map, it appears that stormwater utilities cluster around urban hubs in the continental US. This is unsurprising, as urbanization results in both water quality and quantity challenges that require stormwater management and likely benefit from a dedicated source of funding, like a stormwater enterprise fund. Additionally, stormwater utilities appear to be quite popular along the southeastern coast of the US, the Great Lakes region, and the Pacific Northwest but are far less common in the southwest, the Great Plains regions, or along the Gulf of Mexico. 

Stormwater is the only growing source of water pollution in many waterways across the country. With urban populations expected to grow to nearly 70 percent by 2050, and more frequent and intense storms occurring across the country, there is ever-increasing pressure on stormwater systems and water infrastructure.

See here - link 

What is a smart stormwater network?


Digital transformation

Ayyeka is leading the digital transformation for critical infrastructure clients seeking greater efficiency, sustainability and bottom-line performance. Data creation, management, and utilization underpin our cybersecure, strategic AI solutions. With our end-to-end digital solution we provide the data necessary to develop a clear understanding of the asset base’s constituent parts, how they perform individually and interact collectively. Digital transformation lets utilities turn their data into meaningful and actionable information to shape strategic asset management and proactive maintenance interventions on the ground.

We believe that the most effective digital transition is founded not just on digital tools and data, but on the deep institutional knowledge of people who understand the asset base across the infrastructure lifecycle. Sensors, monitoring and analytics are of limited use without the insights of the people who are intimate with how assets are designed, built and behave.

There is a cost to capturing, storing and accessing data. We excel in defining the data that best supports your organization’s goals – and focus on ensuring that data collected is of sufficient quality to deliver value.

Sensors gather data; but expertise from a cross-section of engineering, operations and maintenance disciplines will be necessary to interpret the data patterns and recognise what failure and optimum performance look like. Digital tools are incomplete unless embedded directly into a full solution developed by infrastructure experts – we help our clients achieve the right blend of machine learning and human learning to make this happen.

Client benefit from the fullest possible range of technology options. We can offer our own proprietary monitoring and analytics tools, as well as those offered by our numerous strategic technology partners, or we can support third-party alternatives. Our goal always remains the same, to add value and reduce client risk by identifying the technologies which offer real-world benefits and speed-to-value.

A recent analysis of needs of the U.S. stormwater sector shows an estimated $7.5 billion annual funding gap and revealed top priorities and challenges across the country.

The inaugural MS4 Needs Assessment Survey led by the Water Environment Federation's (WEF) Stormwater Institute, reflects an effort to learn more about the nature and needs of the MS4 sector at a scale that has never been attempted.

The survey generated some significant and surprising findings:

  • Phase I and II (municipal and non-traditional) permittees ranked regulatory compliance, local flooding, and water quality and habitat restoration issues as important program drivers.
  • The most significant challenges as identified are lack of funding, aging infrastructure, and evolving regulations.
  • Respondents indicated the greatest need for information and technical resources is related to funding and financing. In addition, there is a need for technical information and products on green infrastructure practices and innovative techniques/technologies, as well as information related to asset management.
  • An unexpected finding is the lack of priority by respondents regarding climate change, which points to the need to highlight how changing precipitation patterns will impact MS4s in the future.

The typical community’s stormwater system wasn’t designed with climate change in mind. Now that downpours are getting more frequent and intense, that’s a problem for the environment. Does your utility have a stormwater plan that scales up? How can both big and small utilities find the right solution with finite resources? First, a primer:

The benefits of a smart stormwater network

  1. Operational efficiency

    1. Easier to predict maintenance, reducing downtime of assets and inconvenience to utility and the greater community.

  2. Customer service

    1. Complaints from residents and commercial consumers will be addressed more easily.

    2. Example: Low water pressure in a downstream golf community in Florida caused complaints. With Ayyeka’s monitoring of flow and pressure, the utility found the source of the problem and took corrective action.

  3. Regulatory affairs

    1. In an increasingly complex regulatory environment, collecting accurate data in a timely manner is essential to avoid government fines.

  4. Improved design practices

    1. A well-designed system is more efficient and has lower operational costs. It is easier to anticipate downtime for repairs, reducing the length of service interruptions.

  5. Environmental impact

    1. Reduced pollution protects drinking water, rivers, lakes, gardens, and overall quality of life.

Regulatory Angles


Government agencies regulate utilities to ensure public health. In the US, there are Federal, state, and local regulations. The two most important pieces of legislation are the Clean Water Act and the National Pollutant Discharge Elimination System.

Clean Water Act

The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. The basis of the CWA was enacted in 1948 and was called the Federal Water Pollution Control Act, but the Act was significantly reorganized and expanded in 1972. "Clean Water Act" became the Act's common name with amendments in 1972.

Under the CWA, EPA has implemented pollution control programs such as setting wastewater standards for industry. EPA has also developed national water quality criteria recommendations for pollutants in surface waters.

The CWA made it unlawful to discharge any pollutant from a point source into navigable waters, unless a permit was obtained:

  • EPA's National Pollutant Discharge Elimination System (NPDES) permit program controls discharges.
  • Point sources are discrete conveyances such as pipes or man-made ditches.
    • Individual homes that are connected to a municipal system, use a septic system, or do not have a surface discharge do not need a NPDES permit;
    • Industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters.

National Pollutant Discharge Elimination System (NPDES)

The NPDES permit program, created in 1972 by the Clean Water Act (CWA), helps address water pollution by regulating point sources that discharge pollutants to waters of the United States. The permit provides two levels of control: technology-based limits and water quality-based limits (if technology-based limits are not sufficient to provide protection of the water body).

Other important US legislation on water includes the Endangered Species Act, the Safe Water Act, and the National Flood Insurance Act of 1968. More details here:

Also: America must rethink how it uses wastewater

Smart stormwater network best practices

  1. Start small and scale up

  2. Get management buy-in 

  3. Prefer end-to-end solutions. Most integrations cost more and run longer than expected

  4. Versatile solution - Make sure you can take advantage of different assets data in your network (level, flow, rainfall, tank levels, pumping stations, etc.)

  5. Cyber security 

  6. Interoperability on the SW side (connection of the field data to SCADA, modeling solutions, etc.)

  7. EPA Fact Sheet on BPs - see here 

Communities all over America are adopting smart growth strategies to reach environmental, community, and economic goals. The environmental goals include water benefits that accrue when development strategies use compact development forms, a mix of uses, better use of existing infrastructure, and preservation of critical environmental areas. While the water quality and stormwater benefits of smart growth are widely acknowledged, there has been little explicit regulatory recognition of these benefits to date.

Regulations under the National Pollutant Discharge Elimination System (NPDES) stormwater program offer a structure for considering the water quality benefits associated with smart growth techniques. Compliance with federal, state, and local stormwater programs revolves around the use of “best management practices'' (BMPs) to manage stormwater. Given the water benefits of smart growth at the site, neighborhood, and watershed levels, many smart growth techniques and policies are emerging as BMPs.

The goal is to help commu­nities that have adopted smart growth poli­cies and plans recognize the water benefits of those smart growth techniques and suggest ways to integrate those policies into stormwater planning and compliance. Taking credit for the work a community is already doing can be a low-cost and practical approach to meeting water quality goals and regulatory commitments. A detailed report on BMPs from the EPA appears here - link

The most contentious policy issue currently in the water sector is the Waters of the U.S. (or WOTUS) rulemaking, with its constant back-and-forth dynamics. While the 2015 version of the WOTUS regulations under the Obama administration expanded the jurisdictional universe of waters defined as a WOTUS, the 2020 version under the Trump administration reduced this coverage significantly, including eliminating ephemeral streams from inclusion under the legislation. In the stormwater sector, the most significant WOTUS issue is the exclusion of stormwater management infrastructure from being considered under the rule. 

The specific concern relates to scenarios where a stormwater practice — such as a stormwater pond — that was originally constructed to meet regulatory requirements may be viewed as a natural body of water to those unaware of the original intent of the practice. As such, further definition is required. Considering that there are well over a million stormwater control measures across the U.S. by one estimate, the burden to regulators to address confusion over these scenarios would be overwhelming and a strain on limited resources. Also, the focus on nature-based practices — namely green stormwater infrastructure — makes these scenarios all the more likely to arise. 

The currently proposed rule out for comment rolls the definition back to the pre-1986 WOTUS ruling — which does not include an exclusion for such stormwater control features. The National Municipal Stormwater Alliance (NMSA) and other groups have voiced the need for this exclusion, so it is hoped that this uncontentious issue is resolved in the final rulemaking. 

Another regulatory program that MS4s should keep their eye on is the Electronic Reporting (or E-Reporting) Rule. The first phase of this rule has been completed, so EPA is currently engaged in the second phase, which includes MS4s with the premise that all MS4 permit compliance documentation will be required to be provided in a digital format by December 21, 2025 (note that “digital format” means data in a spreadsheet or database as opposed to simply transitioning paper reports to PDF documents). While this is four years away, the process of shifting regulatory documentation for entire states or municipalities is not quickly or easily done, so this is a relatively short period of time in this context. Also, this date was initially set for December 21, 2020, so an additional extension is not likely. 

A final topic to consider tracking is the Clean Watersheds Needs Survey (CWNS), an effort led by EPA and state regulatory programs periodically to capture the capital investment needs in the Clean Water sector. 

EPA has developed a costing tool that enables a community to provide basic information about a stormwater practice (such as the size of the stormwater control measure (SCM) footprint and the type of SCM) to generate an estimated cost. 

Also, EPA has developed a list of accepted documents that can be used to estimate capital needs for stormwater, which include watershed plans, stormwater utility feasibility studies, capital improvement plans, climate resilience evaluations, and many other similar types of documents. EPA is also allowing states to develop their own approaches to estimating stormwater needs. Each state has an assigned state CWNS coordinator, who is the point of contact for communities and utilities in their state. This coordinator leads efforts to develop these “state approaches” along with other support in their state. This flexibility reflects EPA’s recognition that states vary in their approaches to tracking stormwater infrastructure needs. 

With the significant increases in funding authorized in the Infrastructure Investment and Jobs Act of 2021 for the SRF and OSG programs, the incentive for states and communities to report stormwater needs is more urgent than ever. NMSA is working with EPA staff to perform outreach and engagement with states and MS4s to ensure that stormwater needs are identified and captured in the CWNS. See here - link

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