Stormwater Management

1. Stormwater Management - Background

What is Stormwater?

storm water image

Image: Courtesy of City of Long Beach, CA

Stormwater is any precipitation (rain, sleet, snow, hail) that falls to the surface of the earth. In areas with natural, unaltered groundcover, about 10% of the precipitation runs over the land surface and about 50% infiltrates into the soil to replenish groundwater flow and base flow to streams.

Evapo-transpiration and uptake by plants account for the remaining percentage of precipitation. The precipitation that falls on the land drains from the higher areas over and through the soil and eventually reaches rivers, streams, lakes or the ocean.

But, when natural conditions change due to development and land use, this water cycle becomes altered. As the land becomes more covered with impervious surfaces, more of the precipitation runs over the land, carrying with it pollutants from the pavements to the waterways. In areas where there is development, less than 15% of the runoff makes it into the soil and over 55% of the precipitation runs off!

Why care about impervious surfaces?

The amount of impervious surfaces in the watershed is one factor in determining the amount of pollutants in our waterbodies. When impervious coverage is 10% or less of a watershed the water quality is very good. When impervious cover is between 10 - 25% of the watershed the water quality is impacted and deteriorating and over 25% coverage in the watershed results in badly deteriorated surface water quality in the watershed streams and lakes.

Water Cycle with 75%-100% impervious surfaces. Image: Courtesy of ANJEC

Water Cycle with natural groundcover. Image: Courtesy of ANJEC

Types of NPS Pollution

Non-point source pollution has no specific source but is caused by a variety of pollutants that are present in stormwater runoff. These include:

Nutrients
Pathogens
Sediment
Toxic Contaminants
Debris
Thermal Stress

Pollution. Image: Courtesy of County of Honolulu Department of Environmental Services

Why Care About Stormwater?

As water runoff travels across the land surfaces, it picks up pollutants that can be health risks to humans and cause serious damage to the water ecosystem. These include oil and grease, chemicals, nutrients, metals and bacteria. Over 60% of existing water quality problems are the result of non-point source pollution linked to stormwater runoff.

Because the Federal Government says so...

The U.S. Environmental Protection Agency (EPA) has identified nonpoint source (NPS) pollution as one of the most serious threats to water quality - stormwater being a major component. Under the National Pollutant Discharge Elimination System (NPDES) EPA controls both stormwater and sewer overflow discharges. NPDES provides guidance to municipalities, state and federal permitting authorities on how to meet stormwater pollution control goals.

Stormwater travels to the sea. Image: Courtesy of New Jersey Department of Environmental Protection

Phases of the National Pollutant Discharge Elimination System (NPDES) Stormwater Program

Phase I
In response to the 1987 Amendments to the Clean Water Act (CWA), the EPA developed Phase I of the NPDES Stormwater Program in 1990. Phase I addressed the sources of stormwater runoff that had the greatest potential to negatively impact water quality.

Under Phase I permits are required for stormwater discharges from:

Medium and large municipal separate storm sewer systems (MS4s) located in incorporated places or counties with populations of 100,000 or more, and
Eleven categories of industrial activities including construction activities that disturb 5 or more acres of land.

Phase II
The Phase II Final Rule, published in the Federal Register on December 8th, 1999 requires NPDES permit coverage for stormwater discharges from:

Certain regulated small municipal separate stormwater sewer systems (MS4s) and,
Construction activity distributing between 1 to 5 acres of land.

For more information on the NPDES program please visit the EPA Web site ( http://cfpub.epa.gov/npdes/stormwater/swphases.cfm).

Because the State Government says so...

Stormwater Management is not only a federal program, it is a NJ Department of Environmental Protection (NJ DEP) program as well. States were required to adopt the municipal stormwater rules by March of 2003. Because of the size of the program for NJ, innovative ways of permitting are being utilized to streamline the process and lower the costs of this environmental regulation.

It is important to note that New Jersey's Rules differ in some aspects from EPA's Phase II stormwater rules.

The NJ DEP has been working with a Stormwater Permitting Advisory group which has closely assisted the DEP in developing their policies.

There are 4 components to the Stormwater Management Rules:

Statewide requirements
- Nonstructural SWM Strategies
- Groundwater Recharge
- Quality Control
Municipal Stormwater Planning
Regional Stormwater Management Planning
Protections for Special Water Resources

To read more about NJ Stormwater Management program, please visit the NJ DEP stormwater Web site ( http://www.njstormwater.org).

Stormwater drain. Image: Courtesy NJ DEP Division Of Watershed

NJ DEP Stormwater Management Rules