Stormwater Runoff

Stormwater runoff is generated when precipitation from rain and snowmelt events flows over land or impervious surfaces and does not percolate into the ground. As the runoff flows over the land or impervious surfaces (i.e. paved streets, parking lots, building rooftops, etc.), it accumulates debris, chemicals, sediment, and other pollutants that could adversely affect water quality if the runoff is discharged untreated. Storm sewers can be connected to sanitary sewers and is treated as wastewater when that is the case, so that when discharged it is better for the environment.

We have 554 resources (and counting) on Stormwater in our Documents Database that provide valuable information on this topic. You can search for documents on wet weather management strategies, how to verify the source of inappropriate discharges to storm drainage systems, how to develop a CSO Long-Term Control Plan, and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Stormwater within our database just select "CATEGORY" in the dropdown then choose "Stormwater." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.

Hurricane Season Resources

Peak hurricane season starts mid-August and typically lasts through October. Here are some resources to help your water utility to weather the storms as best as you can. 

According to the National Hurricane Center, there are five major hazards associated with hurricanes. These hazards include storm surge & storm tide, heavy rainfall & inland flooding, high winds, as well as rip currents and tornadoes. Storm surge can travel several miles inland and can cause dangerous saltwater intrusion in areas with estuaries and bayous. 

Use this Storm Surge Inundation Map from U.S. EPA to view your utility’s hurricane risk, mitigate flood damage, and get real-time coastal storm advisories. Rainfall amounts are not directly related to the strength of tropical cyclones but rather to the speed and size of the storm, as well as the geography of the area. This means that it is important to track the rise of water levels even after the storm has passed and to be prepared for flooding. 

U.S. EPA's Flood Resilience Guide is a helpful resource to know your flooding threat and identify practical mitigation options to protect your assets. Hurricane force winds (74 mph or more) can destroy buildings and cause power outages as debris flies around so emergency managers should plan on having their evacuations complete and their personnel sheltered before the onset of tropical storm-force winds, not hurricane-force winds. Access U.S. EPA's newly updated Power Resilience Guide to learn about strategies water and wastewater utilities can use to increase resilience to power outages.

Further Hurricane Season Resources:

• Hurricane Tracker | National Hurricane Center
  • Use this tool to view storm activity in your area to better prepare for potential landfall of a hurricane.
• Hurricane Incident Action Checklist | U.S. EPA
  • This checklist outlines key actions that can be taken immediately before, during, and after the event to mitigate impacts. 
• Climate Resilience Evaluation and Awareness Tool (CREAT) | U.S. EPA
  • CREAT is a tool that assists water sector utilities in assessing climate-related risks to utility assets and operations. Throughout CREAT’s five modules, users consider climate impacts and identify adaptation options to increase resilience.
• NHC Outreach Resources | National Hurricane Center
  • Find resources and information about the practical program of education and outreach on hazardous tropical weather offered by the National Hurricane Center.
• Federal Funding for Utilities in National Disasters (Fed FUNDS) | U.S. EPA
  • Fed FUNDS presents information tailored to water and wastewater utilities on federal disaster and mitigation funding programs from EPA, FEMA, HUD and SBA. 
• Emergency Response Tools | U.S. EPA
  • EPA has a variety of tools and guidance to support drinking water and wastewater utility preparedness and response.
     

Hurricane Preparedness for Wastewater Facilities

As Hurricane Ian left swaths of Florida without water and wastewater services at the end of September, the New York Times was already reporting on potential environmental impacts of the storm hitting South Carolina. Beyond the acute hazards of exposure to untreated wastewater, the biggest concern in hurricane-impacted areas is nutrient pollution and the potential for harmful algal blooms.

As extreme weather events impact larger stretches of the country, the water sector (including regional watershed protection entities) will need to anticipate greater consequences in the emergency response planning process. Florida DEP's Hurricane Preparedness for Domestic Wastewater Facilities and FEMA's Hurricane and Flood Mitigation Handbook for Public Facilities offer some helpful recommendations.

FEMA divides its recommended (primarily anticipatory) mitigation strategies into four categories: elevate or relocate, protect or divert, floodproof, provide redundant systems. The fact sheet identifies which of these strategies are appropriate for each major component of a wastewater facility. For example, installing "backflow prevention devices such as valves on lines that flow into the lift station and emergency overflow lines" is an option for floodproofing a lift station.

FEMA also provides a similar framework for drinking water systems.

Florida DEP's suggestions for before and after a hurricane can provide an update to an existing baseline checklist, particularly for minimizing these concerning downstream impacts. For example, it is recommended to "drain wastewater holding ponds as completely as practical after receiving a hurricane warning" as well as ensure that biosolids for land application have been "spread or stored in a secure manner."

With the frequency and severity of hurricanes and other extreme weather events increasing, facilities may need to adopt new strategies to prevent costly cleanup efforts and even legal battles.

Featured Video: Regional Collaboration for Clean Water in York County

Over 500 communities in the Chesapeake Bay watershed are working to meet NPDES permit standards for stormwater discharges from their municipal separate storm sewer systems (MS4s). MS4s that discharge to impaired surface waters or directly to the Bay are required to develop Pollutant Reduction or TMDL Plans. Meeting these requirements while also addressing important local issues such as increased flooding can be a challenge for any municipality, regardless of size.

However, Pennsylvania's York County has proven that there is strength in numbers. This video from MOST (Municipal Online Stormwater Training Center, an initiative of the University Of Maryland's Environmental Finance Center) features Felicia Dell, the director of the York County Planning Commission discussing how municipalities in her county banded together in a consortium to attract funding, and then distributed this funding in an equitable way to construct projects that would benefit all.

Featured Video: An Inflow and Infiltration Reduction Program in Missouri

Inflow and infiltration (I/I) can be very costly for small communities, especially those communities with outdated combined wastewater/stormwater systems or collection systems in poor repair. According to this classic National Small Flows Clearinghouse article, I/I problems place additional burdens on these older and/or fragile systems because the extra water that seeps or flows into them can be very damaging, and, in some cases, even cause contamination issues.

This week's featured video describes how the City of Columbia, Missouri is attempting to locate, identify, and correct improper connections and defects that cause these inflow and infiltration problems so that their system capacity improves, and sanitary sewer overflows and basement backups are eliminated.