What is Stormwater and Stormwater Runoff?

Editor’s note: Welcome to our series on Stormwater Management! We hope you find these PIG-exclusive articles to be helpful in explaining the basics of stormwater regulations and what you can do to help protect your storm drains.

Stormwater is precipitation that reaches the ground in the form of rain, hail, sleet and snowmelt. In a natural landscape, stormwater is largely absorbed into the ground where it replenishes the drinking and groundwater supplies, provides nourishment to plants and animals and helps maintain healthy ecosystems.

Unfortunately, when stormwater falls on impervious surfaces it can cause problems for facility management, public health and the environment. As water passes over asphalt and concrete, rooftops, or other hard surfaces, it is unable to infiltrate the ground and becomes stormwater runoff.

Why is Stormwater Runoff a Problem?

Stormwater runoff travels across the ground surface picking up anything and everything it encounters, often carrying pollutants to the closest storm drains or retention ponds. Stormwater systems are designed to carry away water as quickly as possible and rarely lead to wastewater treatment facilities. Instead, they transport the pollution directly to nearby streams, rivers, lakes or the ocean.

Polluted runoff can have significant negative consequences on the overall quality of the receiving waterway or waterbody. To minimize the potential for damages, the EPA, state and local governments put limits on how much pollution can enter a receiving water. Businesses that exceed these established limits can face EPA violations and the hassles and headaches that come with them. In addition to potential fines, lawsuits and shutdowns, your organization could earn a negative reputation in the eyes of customers, business partners and other stakeholders.

Common Stormwater Pollutants

Stormwater pollution is anything that is picked up and carried by stormwater runoff that can be harmful to rivers, lakes, streams and other natural resources. Some of the most common threats to water quality are:

• Oils, oil-based liquids and fuels
• Sediment
• Trash and debris
• Heavy metals (i.e. zinc, copper and lead)
• Chemicals

Each of these pollutants presents a unique challenge to manage. Identifying their sources and the locations where they are generated is a critical step toward developing and maintaining a successful Stormwater Pollution Prevention Plan (SWPPP).

What are the Sources of Stormwater Pollution?

From industrial plants and distribution centers to smaller operations that may or may not have production processes, most facilities can trace their stormwater pollution to the following culprits:

• Vehicles and outdoor equipment — oil, grease, fuel, antifreeze, copper, zinc, iron
• Waste collection areas (dumpsters and trash compactors) — trash, oils, grease, food waste, iron
• Stockpiles and raw material yards — sediment and debris, heavy metals, oil and grease
• Galvanized and painted exterior surfaces (rooftops and buildings) — zinc, lead
• Washdowns of processing equipment and vehicle fleets

Pollution from vehicles is a challenge to manage because it’s essentially a moving target. Not only do your own vehicles spread potential risks around your facility, but delivery trucks and visitors can bring outside pollutants on-site. Leaks from the vehicles themselves are a constant threat, so it’s important to protect drains in high-risk areas like loading docks, fuel transfer points and parking lots.

Other sources of pollution are typically stationary, such as dumpsters and outdoor storage areas, making them easier to target at the source. By containing the problem before it reaches a drain, you can further reduce the chance of pollutants ever reaching a waterbody.

Even when it’s not raining or snowing, your storm drains can still be at risk for pollution from chemical leaks and spills. Places like loading docks and hazardous liquid storage areas are common locations for dropped drums, tipped containers and other accidental spills.

Stormwater Management Solutions

There are a growing number of effective solutions for managing stormwater. Green solutions like detention ponds, rain gardens and other vegetated infiltration areas offer environmentally friendly ways to treat and manage polluted stormwater.

Another consideration is large-scale, underground vault-like systems that are more expensive but provide storage and treatment capabilities when space above-ground is at a premium.

For smaller budgets and facilities that don’t have the option of an infrastructure change, there are a wide range of affordable products designed specifically for stormwater management. For example: drain covers can temporarily seal off a drain; storm drain filters and filtration “socks” provide passive protection that still allows clean water to flow; and absorbent spill kits can be stored near storm drains for fast response to emergency spills. These product-level solutions can be incorporated into SWPPPs as Best Management Practices (BMPs) to help you meet and exceed stormwater discharge permit requirements.