Stormwater - AbsoluteAstronomy.com

Stormwater is water that originates during precipitation

Precipitation (meteorology)

In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system. Stormwater that does not soak into the ground becomes surface runoff

Surface runoff

Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

, which either flows directly into surface water

Surface water

Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....

ways or is channeled into storm sewers, which eventually discharge to surface waters.

Stormwater is of concern for two main issues: one related to the volume and timing of runoff water (flood

Flood

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

control and water supplies) and the other related to potential contaminants that the water is carrying, i.e. water pollution

Water pollution

Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....

.

Stormwater is also a resource and ever growing in importance as the world's human population demand exceeds the availability of readily available water. Techniques of stormwater harvesting

Stormwater harvesting

Stormwater harvesting is the collection, accumulation, treatment or purification, and storing of stormwater for its eventual reuse. It differs from rainwater harvesting as the runoff is collected from drains or creeks, rather than roofs...

with point source water management and purification that can potentially make urban environments self sustaining in terms of water.

History

Since humans began living in concentrated village or urban settings, stormwater runoff has been an issue. During the Bronze Age

Bronze Age

The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

, housing took a more concentrated form, and impervious surface

Impervious surface

Impervious surfaces are mainly artificial structures--such as pavements that are covered by impenetrable materials such as asphalt, concrete, brick, and stone--and rooftops...

s emerged as a factor in the design of early human settlements. Some of the early incorporation of stormwater engineering is evidenced in ancient Greece

Greece

Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

.

A specific example of an early stormwater runoff system design is found in the archaeological recovery at Minoan

Minoan civilization

The Minoan civilization was a Bronze Age civilization that arose on the island of Crete and flourished from approximately the 27th century BC to the 15th century BC. It was rediscovered at the beginning of the 20th century through the work of the British archaeologist Arthur Evans...

Phaistos

Phaistos , also transliterated as Phaestos, Festos and Phaestus is an ancient city on the island of Crete. Phaistos was located in the south-central portion of the island, about 5.6 kilometres from the Mediterranean Sea. It was inhabited from about 4000 BC. A palace, dating from the Middle Bronze...

on Crete

Crete

Crete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...

Stormwater pollution

Because impervious surfaces (parking lot

Parking lot

A parking lot , also known as car lot, is a cleared area that is intended for parking vehicles. Usually, the term refers to a dedicated area that has been provided with a durable or semi-durable surface....

s, road

Road

A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

s, building

Building

In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...

s, compacted soil

Soil compaction

In Geotechnical engineering, soil compaction is the process in which a stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water being displaced from between the soil grains then...

) do not allow rain to infiltrate

Infiltration (hydrology)

Infiltration is the process by which water on the ground surface enters the soil. Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour. The rate decreases as the soil becomes...

into the ground, more runoff is generated than in the undeveloped condition. This additional runoff can erode watercourses (streams

STREAMS

In computer networking, STREAMS is the native framework in Unix System V for implementing character devices.STREAMS was designed as a modular architecture for implementing full-duplex I/O between kernel or user space processes and device drivers. Its most frequent uses have been in developing...

and rivers) as well as cause flooding after the stormwater collection system is overwhelmed by the additional flow. Because the water is flushed out of the watershed

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

during the storm event, little infiltrates the soil, replenishes groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

, or supplies stream baseflow

Baseflow

Baseflow is the portion of streamflow that comes from "the sum of deep subsurface flow and delayed shallow subsurface flow"...

in dry weather.

Pollutants entering surface waters during precipitation events is termed polluted runoff. Daily human activities result in deposition of pollutants on road

Road

s, lawn

Lawn

A lawn is an area of aesthetic and recreational land planted with grasses or other durable plants, which usually are maintained at a low and consistent height. Low ornamental meadows in natural landscaping styles are a contemporary option of a lawn...

s, roof

Roof

A roof is the covering on the uppermost part of a building. A roof protects the building and its contents from the effects of weather. Structures that require roofs range from a letter box to a cathedral or stadium, dwellings being the most numerous....

s, farm

Farm

A farm is an area of land, or, for aquaculture, lake, river or sea, including various structures, devoted primarily to the practice of producing and managing food , fibres and, increasingly, fuel. It is the basic production facility in food production. Farms may be owned and operated by a single...

fields, etc. When it rains or there is irrigation

Irrigation

Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

, water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

runs off and ultimately makes its way to a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

, lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

, or the ocean

Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

. While there is some attenuation

Attenuation

In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...

of these pollutants before entering the receiving waters, the quantity of human

Human

Humans are the only living species in the Homo genus...

activity results in large enough quantities of pollutants to impair these receiving waters.

Stormwater runoff as a source of pollution

In addition to the pollutants carried in stormwater runoff

Surface runoff

, urban runoff is being recognized as a cause of pollution in its own right.
In natural catchments (watersheds

Drainage basin

) surface runoff entering waterways is a relatively rare event, occurring only a few times each year and generally after larger storm events. Before development occurred most rainfall soaked into the ground and contributed to groundwater recharge or was recycled into the atmosphere by vegetation through evapotranspiration

Evapotranspiration

Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...

.

Modern drainage systems which collect runoff from impervious surfaces (e.g., roofs and roads) ensure that water is efficiently conveyed to waterways through pipe networks, meaning that even small storm events result in increased waterway flows.

In addition to delivering higher pollutants from the urban catchment, increased stormwater flow can lead to stream erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

, encourage weed invasion, and alter natural flow regimes. Native species often rely on such flow regimes for spawning, juvenile development, and migration.

In some areas, especially along the U.S. coast, polluted runoff from roads and highways may be the largest source of water pollution. For example, about 75 percent of the toxic chemicals getting to Seattle, Washington's Puget Sound

Puget Sound

Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...

are carried by stormwater that runs off paved roads and driveways, rooftops, yards, and other developed land.

manage stormwater to control flooding and erosion;

manage and control hazardous materials to prevent release of pollutants into the environment (source control);

plan and construct stormwater systems so contaminants are removed before they pollute surface waters or groundwater resources;

acquire and protect natural waterways where they still exist or can be rehabilitated;

build "soft" structures such as ponds, swales

Bioswale

Bioswales are landscape elements designed to remove silt and pollution from surface runoff water. They consist of a swaled drainage course with gently sloped sides and filled with vegetation, compost and/or riprap...

or wetlands

Constructed wetland

A constructed wetland or wetpark is an artificial wetland, marsh or swamp created as a new or restored habitat for native and migratory wildlife, for anthropogenic discharge such as wastewater, stormwater runoff, or sewage treatment, for land reclamation after mining, refineries, or other...

to work with existing or "hard" drainage structures, such as pipes and concrete channels;

revise current stormwater regulations to address comprehensive stormwater needs;

enhance and enforce existing ordinances to make sure property owners consider the effects of stormwater before, during and after development of their land;

educate a community about how its actions affect water quality

Water quality

Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

, and about what it can do to improve water quality; and

plan carefully to create solutions before problems become too great.

Integrated water management

Integrated water management (IWM) of stormwater has the potential to address many of the issues affecting the health of waterways and water supply challenges facing the modern urban city.

Also known as low impact development

Low impact development

Low-impact development is a term used in the United States to describe a land planning and engineering design approach to managing stormwater runoff. LID emphasizes conservation and use of on-site natural features to protect water quality...

in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, or Water Sensitive Urban Design (WSUD) in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, IWM has the potential to improve runoff quality, reduce the risk and impact of flooding and deliver an additional water resource to augment potable supply.

The development of the modern city often results in increased demands for water supply due to population growth, while at the same time altered runoff predicted by climate change has the potential to increase the volume of stormwater that can contribute to drainage and flooding problems. IWM offers several techniques including stormwater harvest (to reduce the amount of water that can cause flooding), infiltration

Infiltration basin

An infiltration basin , is a type of best management practice that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...

(to restore the natural recharge of groundwater), biofiltration or bioretention

Bioretention

Bioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. Stormwater is collected into the treatment area which consists of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer, planting soil, and plants...

(e.g., rain gardens) to store and treat runoff and release it at a controlled rate to reduce impact on streams and wetland treatments (to store and control runoff rates and provide habitat in urban areas).

There are many ways of achieving low impact development (LID). The most popular is to incorporate land-based solutions to handle stormwater runoff through the use of retention ponds, bioswale

Bioswale

s, infiltration trenches, sustainable pavements (such as pervious concrete

Pervious concrete

Pervious concrete is a special type of concrete with a high porosity used for concrete flatwork applications that allows water from precipitation and other sources to pass directly through, thereby reducing the runoff from a site and allowing groundwater recharge. The high porosity is attained by a...

), and others noted above. LID can also be achieved by utilizing engineered, manufactured products to achieve similar, or potentially better, results as land-based systems (underground storage tanks, stormwater treatment systems, biofilter

Biofilter

Biofiltration is a pollution control technique using living material to capture and biologically degrade process pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and microbiotic oxidation of contaminants in air...

s, etc.). The proper LID solution is one that balances the desired results (controlling runoff and pollution) with the associated costs (loss of usable land for land-based systems versus capital cost of manufactured solution). Green (vegetated) roofs are also another low cost solution.

IWM as a movement can be regarded as being in its infancy and brings together elements of drainage science, ecology and a realization that traditional drainage solutions transfer problems further downstream to the detriment of our environment and precious water resources.

Federal requirements

In the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, the Environmental Protection Agency

United States Environmental Protection Agency

The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

(EPA) is charged with regulating

Regulation

Regulation is administrative legislation that constitutes or constrains rights and allocates responsibilities. It can be distinguished from primary legislation on the one hand and judge-made law on the other...

stormwater pursuant to the Clean Water Act

Clean Water Act

The Clean Water Act is the primary federal law in the United States governing water pollution. Commonly abbreviated as the CWA, the act established the goals of eliminating releases of high amounts of toxic substances into water, eliminating additional water pollution by 1985, and ensuring that...

(CWA). The goal of the CWA is to restore all "Waters of the United States" to their "fishable" and "swimmable" conditions. Point source discharges, which originate mostly from municipal wastewater

Wastewater

Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...

(sewage

Sewage

Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...

) and industrial wastewater discharges, have been regulated

Regulation

since enactment of the CWA in 1972. Pollutant loadings from these sources are tightly controlled and limited. However, despite these controls, thousands of water bodies in the U.S. remain classified as "impaired," meaning that they contain pollutants at levels higher than is considered safe by EPA for the intended beneficial use of the water. Much of this impairment is due to polluted runoff.

Under the CWA, point source discharges to "Waters of the United States" require National Pollution Discharge Elimination System (NPDES) permits. To address the nationwide problem of stormwater pollution, Congress

United States Congress

The United States Congress is the bicameral legislature of the federal government of the United States, consisting of the Senate and the House of Representatives. The Congress meets in the United States Capitol in Washington, D.C....

broadened the CWA definition of "point source" in 1987 to include industrial stormwater discharges and municipal separate storm sewer systems ("MS4"). These facilities were required to obtain NPDES permits. This 1987 expansion was promulgated in two phases: Phase I and Phase II. Phase I required that all municipalities

Municipality

A municipality is essentially an urban administrative division having corporate status and usually powers of self-government. It can also be used to mean the governing body of a municipality. A municipality is a general-purpose administrative subdivision, as opposed to a special-purpose district...

of 100,000 persons or more, industrial dischargers, and construction

Construction

In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...

sites of 5 acres (20,000 m²) or more have NPDES permits for their stormwater discharges. Phase I permits were issued in much of the U.S. in 1991. Phase II required that all municipalities

Municipality

, industrial dischargers, construction

Construction

sites of 1 acre (4,000 m²) or more, and other large property owners (such as school district

School district

School districts are a form of special-purpose district which serves to operate the local public primary and secondary schools.-United States:...

s) have NPDES permits for their stormwater discharges. Phase II rules came into effect in 2003.

EPA issued a new Construction General Permit (CGP) in July 2008. This permit expires in 2011 and continues the provisions of the previous permit. In December 2009 EPA issued new discharge standards, called effluent guidelines

Effluent guidelines

Effluent guidelines are U.S. national standards for wastewater discharges to surface waters and publicly owned treatment works . The United States Environmental Protection Agency issues effluent guidelines for categories of industrial sources of water pollution under Title III of the Clean Water...

, for construction sites. These requirements set a new national minimum standard for erosion control

Erosion control

Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development and construction. Effective erosion controls are important techniques in preventing water pollution and soil loss.-Introduction:...

s and sediment control

Sediment control

A sediment control is a practice or device designed to keep eroded soil on a construction site, so that it does not wash off and cause water pollution to a nearby stream, river, lake, or bay...

s, and pollution prevention

Pollution prevention

Pollution prevention ' describes activities that reduce the amount of pollution generated by a process, whether it is consumer consumption, driving, or industrial production...

measures. The effluent guideline provisions will be incorporated into the next round of EPA and state general permits.

In 2009 EPA also launched the website "Watershed Central

Watershed Central

Watershed Central is an Environmental Protection Agency website developed to organize information and tools relevant to watershed management from across the country....

" to allow concerned public to develop plans to protect local watersheds and combat stormwater pollution.

State and local requirements

EPA has authorized 46 states to issue NPDES permits. In addition to implementing the NPDES requirements, many states and local governments have enacted their own stormwater management laws and ordinances, and some have published stormwater treatment design manuals. Some of these state and local requirements have expanded coverage beyond the federal requirements. For example, the State of Maryland

Maryland

Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

requires erosion and sediment controls on construction sites of 5,000 sq ft (460 m²) or more.
It is not uncommon for state agencies to revise their requirements and impose them upon counties and cities; daily fines ranging as high as $25,000 can be imposed
for failure to modify their local stormwater permitting for construction sites, for instance.
REF:fines
REF: CASQ

Nonpoint source pollution management

Agricultural runoff (except for concentrated animal feeding operations, or "CAFO

CAFO

A Concentrated Animal Feeding Operation is a term that was first coined by the United States' Environmental Protection Agency to describe animal agricultural facilities that have a potential pollution profile...

") is considered by the CWA to be nonpoint source pollution

Nonpoint source pollution

Nonpoint source pollution refers to both water and air pollution from diffuse sources. Nonpoint source water pollution affects a water body from sources such as polluted runoff from agricultural areas draining into a river, or wind-borne debris blowing out to sea. Nonpoint source air pollution...

. It is not included in the CWA definition of "point source" and therefore not subject to NPDES permit requirements. The 1987 CWA amendments established a non-regulatory program at EPA for nonpoint source pollution management consisting of research and demonstration projects. Related programs are conducted by the Natural Resources Conservation Service

Natural Resources Conservation Service

The Natural Resources Conservation Service , formerly known as the Soil Conservation Service , is an agency of the United States Department of Agriculture that provides technical assistance to farmers and other private landowners and managers.Its name was changed in 1994 during the Presidency of...

(NRCS) in the U.S. Department of Agriculture

United States Department of Agriculture

The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

Public education campaigns

Education is a key component of stormwater management. A number of agencies and organizations have launched campaigns to teach the public about the problem, and how they can contribute to solving it.

The West Michigan Environmental Action Council (WMEAC) has coined the term Hydrofilth to describe stormwater pollution. This is part of their 15 to the River campaign. WMEAC has taken an active role in preventing Hydrofilth from striking again. They have created a rain barrel distribution program in which they teach people how to have and use a rain barrel in their backyard and educate them on the positive effects it has on combating storm water runoff. Also they have created a website teaching others about how to make their own rain garden

Rain garden

A rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted lawn areas the opportunity to be absorbed...

. WMEAC as well as many other organizations such as the United States Environmental Protection Agency

United States Environmental Protection Agency

and Clean Water Action

Clean Water Action

Clean Water Action, an organization of 1 million members, organizes grassroots groups and coalitions to protect America's waters, build healthy communities and support environmental legislation and political candidates. Created in 1972, Clean Water Action focuses on canvassing and gaining support...

are educating people and communities about the problems with storm water runoff and its effects and what they can do in order to prevent further pollution of their waterways from it.

External links

Center for Watershed Protection
EPA Stormwater Permit Program
Permit Requirements for Tribal Construction Projects
Homeowner's Guide to Rainfall - Toronto * Stormwater Best Management Practice Maintenance, Kansas State University
StormCon - World's Largest Stormwater Pollution Prevention Conference
Stormwater Magazine - a stormwater trade journal
Storm Water Solutions magazine - a stormwater trade publication
Pervious Concrete Blog - Discussion on the latest in Pervious Concrete Technology
Stormwater Harvesting Applications - Examples of Stormwater harvesting in large and small scale
International Stormwater Best Management Practices (BMP) Database

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