Stormwater Management and Compliance: Issues, Data, Trends, and Updates

Stormwater Management

     Stormwater management is mostly but not always an urban issue where excess water runoff from storms can cause environmental damage and pollution. Good runoff management can include well-designed culvert and drain systems to keep runoff away from places where it can cause damage. Temporary water catchment systems can be utilized for construction. Storms can create pollution events via soil saturation, runoff, and flooding, which can collect and transport contaminants. Stormwater management involves several activities, including planning and measurement, monitoring and control, and pumping and treatment. “It includes infrastructure such as gutters, conduits and trenches, in addition to detention tanks, large and small pump stations and treatment plants.”

     Maureen Harris, P.E., Stormwater Team lead for AECOM noted in a LinkedIn post:

“A 2,000 square foot house with a 400 square foot driveway can generate up to 1,500 gallons of stormwater in a one-inch rainfall.”

     Most stormwater falls under the EPA’s National Pollutant Discharge Elimination System (NPDES) program under the Clean Water Act of 1972. 47 of the 50 U.S. states were given primacy by the EPA to regulate stormwater pollution. This means that different states may have slightly different regulations that companies that operate in multiple states must manage and integrate.

     Polluted stormwater runoff often makes its way through municipal storm sewer systems which commonly discharge without treatment into waterways. The nation’s municipalities must build, maintain, upgrade, and sometimes replace their stormwater infrastructure. EPA mentions watershed-based stormwater planning as a current need.

     Two major sources of stormwater are construction stormwater which makes up nearly half of all facilities regulated by EPA’s National Pollution Discharge Elimination System (NPDES), and industrial stormwater, which makes up almost a quarter.  

 

 

     Stormwater management is one way to reduce the occurrences and impacts of urban flooding events. Planning involves initiatives such as creating “sponge cities,” designed to reduce runoff by allowing more rainwater to infiltrate the soil below. According to Xylem’s Complete Guide to Stormwater Management, sponge cities apply:

 

“… ecological principles, landscape architecture approaches and key techniques of infiltration, pumping, storage, purification, utilization and discharge. These techniques are applied through best management practices (BMPs) and green stormwater infrastructures (GSI) with low impact, as decided by each municipality.”

 

     Storms can cause combined sewer overflows (CSOs) which overwhelm the local sewer systems. Combined sewers have been discouraged since the 1950s but older systems remain in use. This can result in raw sewage being released into the environment along with contaminants from stormwater runoff. In these cases, disinfecting stormwater runoff can be desirable if feasible. Chlorine may be used. According to Xylem, ozone and UV treatment are among the most efficient disinfection methods for water and better than traditional chlorine-based methods. They do not form disinfection by-products (DBPs) as chlorine does.

     Stormwater runoff flow can be modeled with the goal of optimizing its management. Overflow mitigation is one of the most serious issues to address. For cities, stormwater pump station design can be a big factor in preventing overflows and pollution events. The following graphics depict some of the hydraulics and sedimentation issues facing urban stormwater pumping systems. There are several pump sizes and designs that may be used for these pumping systems. Debris management is very important as well. This often involves screens of different sizes and in different places in the system. Sand management is important as well, since sand is abrasive and can damage pumps. Two ways of dealing with sand in stormwater sewers are pumping it away and sand traps. If the stormwater is pumped to a treatment plant that can deal with solids, then pumping it there is usually the best method. If not, then sand traps can be used to collect the sand. Pumping the sand to the treatment plant involves keeping flow rates high enough to keep the sand in suspension. Trapping involves lowering the flow rate below a settling velocity for the sand particles. After the sand is trapped it may be pumped off to a discharge area or it may be cleaned out manually. Pumping effluent with solids and sludge is more difficult and maintenance-intensive than pumping clear water. Detention systems such as underground infiltration tanks are often utilized in these urban runoff systems. Boring new larger and deeper tunnels to collect stormwater is a management solution as well, as shown below.

 

     There are several strategies for cleaning these detention tanks: manual cleaning, tipping buckets, flushing, bulk flow and flushing with submersible mixers, and ejectors of several types. These are shown and described below from Xylem’s Complete Guide to Stormwater Management. What methods are used for transporting and cleaning depend on the sediment and solids encountered in that specific local environment.

 

     Stormwater management grades into flood management as these pumping systems may also be designed to lower the impacts of flooding events.

     Stormwater management benefits from stormwater monitoring. According to Xylem’s guide:

 

“Stormwater monitoring sites encompass a broad range of parameters from simple rainfall and turbidity measurements, typically encountered during construction practices, to complex multiparameter sites including open channel flow, level, rainfall, pH, temperature, conductivity, dissolved oxygen, turbidity, and even nutrients.”

 

     Groundwater management is another aspect of stormwater management. Drainage and pumping systems can help as well with groundwater management.

 

     Roadside or highway drainage is another important stormwater management strategy as is airport drainage.

 

     Retention ponds are another strategy. These include wet retention ponds, dry detention ponds, and polder pumping stations, all shown below.

 

 

     Rain storage systems might be an option for some applications. The Rainstore3 systems “are described:

 

“… as a modular, stackable, underground water containment system. This innovative solution was designed by a landscape architect for subsurface detention basins, retention/harvesting systems, water/rain gardens, green roofs, and sports field drainage.”

 

   

 

Construction Stormwater Management

 

     Sediment, debris, and chemicals in the loose soils of construction sites are picked up by runoff water and conveyed to sewer systems, streams, rivers, lakes, or coastal waters. Construction operators are required to install stormwater controls onsite. Sediment, solid and sanitary wastes, phosphorus, nitrogen, pesticides, oil and grease, concrete truck washout, construction chemicals, and construction debris are pollutants common at construction sites. Sediment is the biggest component of stormwater pollution. Concrete waste, chemicals and paints, oils and grease, and anything spilled onsite are other components. Sediment can collect in water bodies, reducing their depth and may lead to a need for dredging. According to EPA:

 

“A Clean Water Act permit is required for stormwater discharges from any construction activity disturbing:

 

“1 acre or more of land, or

 

“Less than 1 acre of land, but that is part of a common plan of development or sale that will ultimately disturb 1 or more acres of land.”

 

“Construction activity includes earth-disturbing activities such as clearing, grading, and excavating land and other construction-related activities that could generate pollutants.”

 

The permit requirements for construction and development. Known as C & D permits are as follows:

 

1)        Design, install, and maintain effective erosion and sediment controls, and pollution prevention measures, to minimize the discharge of pollutants;

2)        Stabilize disturbed areas immediately when construction has  ceased and will not resume for more than 14 days;

3)        Prohibit the dewatering discharges unless managed by appropriate controls;

4)        Prohibit the discharge of:

A)       Wastewater from concrete washout (unless managed by appropriate control), or washout/cleanout of stucco, paint, form release oils, other wastewater materials;

B)       Fuels, oils, or other pollutants used for vehicles; and

C)      Soaps or solvents to wash vehicles and equipment.

 

 

 

Erosion and Sediment Control

 

     Erosion and sediment control (ESC) is very important at construction sites and stormwater management is key to that control. In Pennsylvania, timber harvesting and road maintenance activities involving 25 or more acres of earth disturbance require an erosion and sediment control permit instead of NPDES permits. Oil and gas activities in the state that disturb more than 5 scres require a general erosion and sediment control permit. Measures are required to minimize erosion and sedimentation such as physical barriers to slow erosion caused by runoff. Local regulatory authorities may also have ESC requirements. EPA recommends that construction managers monitor weather and have ESC contingency plans and are aware of issues and conduct inspections before and after rainy weather events. EPA notes:

“At large sites, the developers may hire a firm with ESC expertise to implement an inspection, maintenance and repair program for the site. Some permitting authorities require construction sites to undergo inspection by a certified inspector and/or offer inspector certification programs.”

     A stormwater pollution prevention plan (SWPPP) is common, including ESC maintenance. This may involve “removing sediment before it accumulates to half of the above-ground height of any silt fence or other perimeter control.” Some permits require site ESC inspections weekly or every two weeks and must be well documented. This is required for EPA audits which basically ensure compliance. Those construction workers responsible for site ESC should be adequately trained. Microsoft Copilot with data from EPA, safetyculture.com, and others lists the following common ESC measures:

1)        Silt Fences: These are temporary barriers made of geotextile fabric that help to trap sediment while allowing water to flow through.

2)        Sediment Basins: These are designed to capture and store sediment-laden runoff, allowing the sediment to settle before the water is discharged.

3)        Mulching: Applying a layer of mulch to exposed soil helps to protect it from erosion by wind and water.

4)        Seeding and Planting: Establishing vegetation on disturbed soil can stabilize the soil and reduce erosion.

5)        Erosion Control Blankets: These are mats made of natural or synthetic materials that cover the soil and protect it from erosion.

6)        Check Dams: Small barriers placed in drainage channels to slow down water flow and capture sediment.

7)        Diversion Channels: These channels redirect water away from disturbed areas to prevent erosion.

 

     Some firms specialize in stormwater management. They contract with construction developers to handle stormwater compliance issues. They may do planning, permitting, inspection scheduling, inspections, monitoring, and installation oversight. Both site compliance and overall corporate risk management are focuses of these efforts. Corporations may see good stormwater management as an important part of their environmental compliance and sustainability programs. Strategies for managing stormwater compliance include inspections, visual assessments, analytical testing, and planning.

 

 Agricultural Runoff

   Agriculture is another source of stormwater runoff, especially when crops are not planted on a plot during off-seasons. Exposed soil during any season supports more runoff. Solutions range from cover cropping to sediment catchment strategies and drainage. Many of the ESC measures listed above are used to control agricultural runoff as well. The goal is to keep excess sediment out of streams, rivers, lakes, and wetlands. Agricultural runoff also carries fertilizer into waterways which can lead to harmful algae blooms.

 

 

Industrial Stormwater Management

     Parts of industrial activity that are exposed to weather are covered under NPDES industrial stormwater rules. Covered facilities include heavy manufacturing (including paper mills, chemical plants, steel mills, refineries, and foundries); coal and mineral mining and oil & gas processing; hazardous waste treatment, storage, and disposal; landfills and dumps; scrapyards, salvage yards, automobile junkyards, and battery reclamation facilities; steam electric power plants; transportation facilities that have vehicle maintenance, equipment cleaning, or airport deicing operations; sewage treatment plants with a design flow greater than 1 million gal/day; and constructions sites that disturb five acres or more (require a separate permit).

     A current issue of industrial stormwater pollution is with waters adjacent to large coal ash slurry ponds stored at coal-fired power plants. These have been shown to pollute local waterways with high levels of toxic heavy metals. They also have been shown to very often pollute local groundwater aquifers. Regulation is being ratcheted up as I explain in my post about coal ash cleanup.

    

 

Better Filtration for Storm Drains: Can it Reduce Surface Water Pollution?

      As mentioned, an important component of stormwater management systems is screening or filtration. Filters must be cleaned out regularly, often with vacuum trucks, which is expensive. A Florida company believes they have a useful solution. They are installing 50 drainage filters that utilize an "upper flow of water through the screen, which will allow it to continue to flow even as debris is collected,” according to an article in The Cool Down. The goal is to maximize water flow through while trapping debris such as plastics, leaves, and twigs. Their filters even include a QR code that community members can use to report clogs. The effort is focused on cleaning up pollution that makes its way into Biscayne Bay, which is considered quite polluted. The excess debris can also lead to localized excess nitrogen and phosphorus that can lead to algae blooms and some deoxygenation. The company has several videos on their website that model stormwater flow and filtration. The filters use Eddie Lopez patented technologies.

 

Testing Eddie Lopez Technologies' patented curb drainage filters - YouTube

I think that one of the amazing things the video shows is that these filters are very difficult to clog. This is a result of the upward flow of water through the openings. 

References:

Stormwater Management. Sara Meyer. ERM. August 2023. (24) Post | Feed | LinkedIn

Company develops high-tech solution to prevent major waterways from getting polluted: 'It's way easier'. Rick Kazmer. The Cool Down. May 5, 2024. Company develops high-tech solution to prevent major waterways from getting polluted: 'It's way easier' (msn.com)

Autodesk InfoWorks ICM: Plan, design, and operate stormwater, sanitary sewer, and flood infrastructure. Autodesk. Autodesk InfoWorks ICM | Get Prices & Buy Official InfoWorks ICM 2025 | Autodesk

Rainstore3: A Better Way to Contain the Rain. Invisible Structures. Rainstore3: Efficient Underground Water Containment System (invisiblestructures.com)

What is Stormwater Management? | The Basics | Part 1. Tully Consulting Group. Youtube Video. Bing Videos

The Complete Guide to Stormwater Management. stormwater-handbook-us_interactive.pdf (xylem.com)

National Pollutant Discharge Elimination System (NPDES). National Menu of Best Management Practices (BMPs) for Stormwater. U.S. EPA. National Menu of Best Management Practices (BMPs) for Stormwater | US EPA

National Pollutant Discharge Elimination System (NPDES). Stormwater Maintenance. U.S. EPA. Stormwater Maintenance | US EPA

Stormwater Management. U.S.EPA. Stormwater Management | US EPA

National Pollutant Discharge Elimination System (NPDES): Stormwater Discharges from Construction Activities. U.S. EPA. Stormwater Discharges from Construction Activities | US EPA

National Pollutant Discharge Elimination System (NPDES): Stormwater Discharges from Industrial Activities. U.S. EPA. Stormwater Discharges from Industrial Activities | US EPA

Construction Stormwater. Pennsylvania Department of Protection. Construction Stormwater (pa.gov)

Stormwater Best Management Practice: Erosion and Sediment Control Inspection and Maintenance. U.S. EPA. November 2021. Erosion and Sediment Control Inspection and Maintenance (epa.gov)

Ohio helping farmers keep water sources clean. WCMH Columbus. July 30, 2024. Ohio helping farmers keep water sources clean (msn.com)

How do we help contractors? | The Basics | Part 2. Tully Consulting Group. Youtube. How do we help contractors? | The Basics | Part 2 (youtube.com)

National Pollutant Discharge Elimination System (NPDES). Municipal Wastewater. U.S. EPA. Municipal Wastewater | US EPA

Stop Ocean Pollution Technologies. Website. Stormwater drainage inlet filters / screens — SOP Technologies - Environmental Solutions (soptechint.com)

Testing Eddie Lopez Technologies' patented curb drainage filters. Stop Ocean Pollution Technologies.  Testing Eddie Lopez Technologies' patented curb drainage filters (youtube.com)