Water quality

The first flush of urban rushing liquid can be extremely dirty. Storm water possibly becomes contaminated as it runs down a road or other impervious surface, or from lawn chemicals dissolved in the runoff liquid, before entering the drain.

Water running off these impervious surfaces tends to pick up gasoline, lubricating oil, heavy metals, trash, and other contaminants from roads and parking lots, as well as fertilizers and pesticides from lawns. Roads and parking lots are important sources of nickel, copper, zinc, cadmium, lead and polycyclic aromatic hydrocarbons (PAHs), which are created as by-products of the combustion of gasoline and other fossil fuels. Rooftop runoff contributes high levels of synthetic organic compounds and zinc (from galvanized gutters). Fertilizer use on residential lawns, parks, and golf courses is a significant source of nitrates and phosphorus.

Reducing torrential water flows

Stormwater entering storm sewers can be minimized by including low-impact development practices within municipal plans. To reduce stormwater from roofs, stormwater flows may be infiltrated into the adjacent soil rather than discharged into the storm sewer. Stormwater streams can be directed into open ditches before flowing into storm sewers, again to allow the runoff to infiltrate into the ground. Permeable paving materials can be used in the construction of building sidewalks, driveways, and in some cases, parking lots, in order to infiltrate a portion of the stormwater volume. Detention tanks are required in many areas and are used to temporarily retain stormwater runoff during heavy rainfall and restrict outflow into public sewers. A higher flow outlet point may also be used which connects higher on the holding tank side of the outlet point. This higher flow would prevent the holding tank from filling completely to the brim. By restricting the flow of water in this way and temporarily retaining the water in a holding tank, public sewers are far less likely to become overloaded.

Contenido

Los drenajes para tormenta están separados y son distintos de las cloacas. Esta separación entre drenaje para tormenta y cloacas ayuda a prevenir que las plantas para tratamiento de aguas negras queden abrumadas por infiltración/flujo de entrada durante una tormenta pluvial, lo cual puede resultar en aguas negras siendo descargadas hacia el ambiente.

Muchos sistemas de drenaje para tormentas están diseñados para drenar el agua de tormenta, sin tratar, hacia ríos y arroyos. Muchos gobiernos locales conducen campañas de concientización pública, para evitar que desechos sean vertidos hacia el interior del desagüe para tormentas. En la ciudad de Cleveland, Ohio, por ejemplo, todas las nuevas bocas de tormenta tienen inscripciones en las mismas para que no se viertan desechos, y usualmente incluyen la impresión de un pez también. Trout Unlimited de Canadá recomienda que el símbolo de un pez amarillo sea pintado junto a las bocas de tormenta existentes.

Combined collectors

Cities that installed their sewage collection systems before the 1930s typically use single-pipe systems to transport both urban runoff and sewage. This type of collection system is known as combined collector system (CCS). The rationale when combined collectors were built was that it would be cheaper to simply build a unified system. In such systems, sudden, voluminous rainfall that exceeds the sewage treatment capacity will be allowed to flow over and over directly from the storm drains into the receiving waters via structures called combined sewer overflows.

Storm drains are typically at shallower depths than combined sewers; Therefore, while storm drains are designed to accept surface flow from streets, combined sewers were designed to also accept wastewater flows from buildings with basements.

New York City, Washington D.C., Seattle, and other cities with combined systems have this problem due to large flows of rushing water after each heavy rain. Some cities have dealt with this by adding bulky storage tanks or ponds to hold water until it can be treated. Chicago has a system of tunnels, collectively called the Deep Tunnel, beneath the city to store its rushing water. In many areas detention tanks or rooftop detention systems are required to be installed on a property and are used to temporarily retain the flow of stormwater during heavy rain from exiting into the public sanitation network. This reduces the risk of the public sanitation network being overloaded during a heavy rain. A higher flow outlet prevents the detention tank from filling completely to the brim, overflowing into the public sewer. By restricting water flow in this way and temporarily retaining the water in a detention tank or through terrace detention, public sewers are less likely to become overloaded.[3]​.

Building codes and local government ordinances vary greatly regarding management of storm drain flow. New developments in some cities may be required to build their own storm drainage capacity to return runoff to the water table, and bio-slots may be required in ecologically sensitive areas to protect the watershed.

In the United States, cities, suburban communities and towns with more than 10,000 residents under the Clean Water Act are required to obtain discharge permits for their own storm sewer systems. The Environmental Protection Agency (EPA) issued stormwater regulations for large cities in 1990 and other communities in 1999. The permits require local governments to operate stormwater management programs, covering both the construction of new buildings and facilities and the maintenance of their existing municipal sewer networks. Many municipalities have revised their local ordinances to include stormwater management. State government infrastructure, such as roads and highways, is also subject to stormwater management regulations.[3]​.

An international subculture has grown up around the exploration of storm drains. Societies such as the Cave Clan regularly explore the drainages that lie beneath cities. There are also groups like the "Club La Culebra", also called "Club de La Lagartija", who make maps of the tunnels and entrances to share them with other explorers. This is commonly known as "urban exploration", but also known as draining when specifically related to storm drains.

In a number of American cities, homeless people live in storm drains.

Archaeological studies have revealed the use of quite sophisticated drainage systems in ancient cultures. For example, in Minoan Crete approximately 4000 years before the present, cities such as Phaistos were designed to have storm drains and canals to collect the liquid flow of rains. In the Cretan Knossos, storm drains include stone-lined structures large enough for a person to crawl through. Other early civilizations with storm drainage features include early settlers of Mainland such as Gurness and the Brough of Birsay in Scotland.

Water quality

The first flush of urban rushing liquid can be extremely dirty. Storm water possibly becomes contaminated as it runs down a road or other impervious surface, or from lawn chemicals dissolved in the runoff liquid, before entering the drain.

Water running off these impervious surfaces tends to pick up gasoline, lubricating oil, heavy metals, trash, and other contaminants from roads and parking lots, as well as fertilizers and pesticides from lawns. Roads and parking lots are important sources of nickel, copper, zinc, cadmium, lead and polycyclic aromatic hydrocarbons (PAHs), which are created as by-products of the combustion of gasoline and other fossil fuels. Rooftop runoff contributes high levels of synthetic organic compounds and zinc (from galvanized gutters). Fertilizer use on residential lawns, parks, and golf courses is a significant source of nitrates and phosphorus.

Reducing torrential water flows

Stormwater entering storm sewers can be minimized by including low-impact development practices within municipal plans. To reduce stormwater from roofs, stormwater flows may be infiltrated into the adjacent soil rather than discharged into the storm sewer. Stormwater streams can be directed into open ditches before flowing into storm sewers, again to allow the runoff to infiltrate into the ground. Permeable paving materials can be used in the construction of building sidewalks, driveways, and in some cases, parking lots, in order to infiltrate a portion of the stormwater volume. Detention tanks are required in many areas and are used to temporarily retain stormwater runoff during heavy rainfall and restrict outflow into public sewers. A higher flow outlet point may also be used which connects higher on the holding tank side of the outlet point. This higher flow would prevent the holding tank from filling completely to the brim. By restricting the flow of water in this way and temporarily retaining the water in a holding tank, public sewers are far less likely to become overloaded.

Contenido

Los drenajes para tormenta están separados y son distintos de las cloacas. Esta separación entre drenaje para tormenta y cloacas ayuda a prevenir que las plantas para tratamiento de aguas negras queden abrumadas por infiltración/flujo de entrada durante una tormenta pluvial, lo cual puede resultar en aguas negras siendo descargadas hacia el ambiente.

Muchos sistemas de drenaje para tormentas están diseñados para drenar el agua de tormenta, sin tratar, hacia ríos y arroyos. Muchos gobiernos locales conducen campañas de concientización pública, para evitar que desechos sean vertidos hacia el interior del desagüe para tormentas. En la ciudad de Cleveland, Ohio, por ejemplo, todas las nuevas bocas de tormenta tienen inscripciones en las mismas para que no se viertan desechos, y usualmente incluyen la impresión de un pez también. Trout Unlimited de Canadá recomienda que el símbolo de un pez amarillo sea pintado junto a las bocas de tormenta existentes.

Combined collectors

Cities that installed their sewage collection systems before the 1930s typically use single-pipe systems to transport both urban runoff and sewage. This type of collection system is known as combined collector system (CCS). The rationale when combined collectors were built was that it would be cheaper to simply build a unified system. In such systems, sudden, voluminous rainfall that exceeds the sewage treatment capacity will be allowed to flow over and over directly from the storm drains into the receiving waters via structures called combined sewer overflows.

Storm drains are typically at shallower depths than combined sewers; Therefore, while storm drains are designed to accept surface flow from streets, combined sewers were designed to also accept wastewater flows from buildings with basements.

New York City, Washington D.C., Seattle, and other cities with combined systems have this problem due to large flows of rushing water after each heavy rain. Some cities have dealt with this by adding bulky storage tanks or ponds to hold water until it can be treated. Chicago has a system of tunnels, collectively called the Deep Tunnel, beneath the city to store its rushing water. In many areas detention tanks or rooftop detention systems are required to be installed on a property and are used to temporarily retain the flow of stormwater during heavy rain from exiting into the public sanitation network. This reduces the risk of the public sanitation network being overloaded during a heavy rain. A higher flow outlet prevents the detention tank from filling completely to the brim, overflowing into the public sewer. By restricting water flow in this way and temporarily retaining the water in a detention tank or through terrace detention, public sewers are less likely to become overloaded.[3]​.

Building codes and local government ordinances vary greatly regarding management of storm drain flow. New developments in some cities may be required to build their own storm drainage capacity to return runoff to the water table, and bio-slots may be required in ecologically sensitive areas to protect the watershed.

In the United States, cities, suburban communities and towns with more than 10,000 residents under the Clean Water Act are required to obtain discharge permits for their own storm sewer systems. The Environmental Protection Agency (EPA) issued stormwater regulations for large cities in 1990 and other communities in 1999. The permits require local governments to operate stormwater management programs, covering both the construction of new buildings and facilities and the maintenance of their existing municipal sewer networks. Many municipalities have revised their local ordinances to include stormwater management. State government infrastructure, such as roads and highways, is also subject to stormwater management regulations.[3]​.

An international subculture has grown up around the exploration of storm drains. Societies such as the Cave Clan regularly explore the drainages that lie beneath cities. There are also groups like the "Club La Culebra", also called "Club de La Lagartija", who make maps of the tunnels and entrances to share them with other explorers. This is commonly known as "urban exploration", but also known as draining when specifically related to storm drains.

In a number of American cities, homeless people live in storm drains.

Archaeological studies have revealed the use of quite sophisticated drainage systems in ancient cultures. For example, in Minoan Crete approximately 4000 years before the present, cities such as Phaistos were designed to have storm drains and canals to collect the liquid flow of rains. In the Cretan Knossos, storm drains include stone-lined structures large enough for a person to crawl through. Other early civilizations with storm drainage features include early settlers of Mainland such as Gurness and the Brough of Birsay in Scotland.