User:EcoWarrior22/Stormwater

Lead - (from editing - I'm not sure what is the intended text vs what is planned text. This is hard to read and assess.)

Storm water, typically referred to as stormwater, is water that originates from precipitation, specifically rain or snow and ice melt. Stormwater follows the routes described in the water cycle. After reaching land, it can soak into the soil (infiltrate), puddle, evaporate, or contribute to surface runoff. Most runoff is conveyed directly to nearby streams, rivers, or other water bodies (surface water) without treatment.

In natural landscapes, such as forests, soil absorbs much of the stormwater. Plants also reduce the quantity of stormwater by improving infiltration, intercepting precipitation as it falls, and by taking up water through their roots. Vegetation also serves a role in treating infiltrated runoff. In developed environments, unmanaged stormwater can contribute to flooding and pollution. one related to the volume and timing of runoff (flooding) and the other related to potential contaminants the water is carrying (water pollution). Increased impervious surface contributes to increased quantity of stormwater pooling during storm events, and increased exposure to antrhopogenic pollutants. Degradation of water quality due to stormwater is measurable by geochemistry.

Stormwater treatment has changed drastically over time. [Introduce relevant regulatory information such as clean water act, and a historical overview.] [Conclude with the current trajectory of integrated stormwater management and public outreach.] In recent years, hydrology plays a major in greater ecosystem processes (Wagner 2009, more sources, at least three sources). This has brought increased attention to the potential good and harm that urban stormwater management can do for ecological processes. There is increasing pressure on scientists, engineers, and city planners to determine the "best management practices" (BMP) for treating, slowing, and reducing urban water. (Wagner 2009)

Stormwater is also an important resource as human population and demand for water grow, particularly in arid and drought-prone climates. Stormwater harvesting techniques and purification could potentially make some urban environments self-sustaining in terms of water. {..no}

Implications of Urban Stormwater

Urbanization impacts water quality and quantity, which affects stream health, because of stormwater runoff on impervious surfaces (parking lots, roads, buildings, compacted soil). With less vegetation and more impervious surfaces, developed areas allow less rain to infiltrate into the ground, and more runoff is generated than if an area was undeveloped. Impervious cover creates a surface for contaminants and potential pollutants to accumulate, and stormwater runoff washes the contaminants from the surface into local waterways or groundwater. The contribution of stormwater contaminants increases the likelihood of nonpoint source pollution in urban areas. An urban environment's impact on stream hydrology can often be estimated by a measurement of impervious cover as a percentage. Modeling studies have shown that streams with a watershed that measures 10-25% impervious cover are impacted and show signs of declining stream health, but streams with a watershed of 24-60% impervious cover are unable to support natural hydrology or water quality, and watersheds with >60% impervious cover are not longer considered streams at all, and are effectively "urban drainage."

Conveyances, such as ditches and storm sewers, quickly transport runoff away from commercial and residential areas into nearby water bodies. 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. This practice increases the volume of water in waterways during storm events and the discharge of those waterways. These changes to water quantity lead to erosion and flooding. Because the water is flushed out of the watershed during the storm event, little infiltrates into the soil, which replenishes groundwater, or supplies stream baseflow in dry weather.

Pollution

Stormwater carrying street bound pollutants to a storm drain for coastal discharge. Daily human activities result in deposition of contaminants and potential pollutants on roads, lawns, roofs, farm fields, and other land surfaces. Such contaminants include solid trash, sediment, nutrients, bacteria, pesticides, metals, and petroleum byproducts. When it rains or there is excess irrigation, water runs off and ultimately makes its way to a river, lake, or the ocean. Although there is some attenuation of contaminants before entering receiving water bodies, the contaminated runoff can also impair receiving waters.

The first flush is the initial runoff of a rain storm. During this phase, contaminated water enters storm drains in areas with high proportions of impervious surfaces and typically has more concentrated levels of contaminants compared to the remainder of the runoff caused by a storm. Consequently, the high concentrations of urban runoff result in high levels of contaminants that discharge from storm sewers into surface waters.

Most Common Pollutants in Urban Stormwater

Constituent	Chemical Formula	Common Sources	Biological Impacts
Nitrogen Species (Nitrate, Nitrite, Ammonia, etc.)	NO3-, NO2-, NH4+	Fertilizers, human or animal waste	Excessive concentrations can cause nutrient loading, eutrophification
Heavy Metals (Lead, Cadmium, Mercury, Arsenic, Chromium, Thalium)	Pb, Cd, Hg, As, Cr, Tl	Industrial processing, Weathering, Mine drainage,	High concentrations of metals, metalloids, and associated toxic compounds can bioaccumulate in tissues
Total Dissolved Solids (TDS)	N.A.	Soils and sediments, asphalt weathering	High concentrations can become environmental contamination if they reach toxic levels
Hydrocarbons	CnHr	Oil and gas pollution on streats	Presence of some compounds can be toxic to plant and animal life

In some areas, especially along the United States coastlines, contaminated runoff from roads and highways may be the largest source of water contamination. For example, about 75% of toxic chemicals in the Puget Sound, Seattle, Washington, are carried by stormwater that runs off paved roads and driveways, rooftops, yards, and other developed land.

For Class V stormwater injection wells  the U.S. Environmental Protection Agency reports “the contaminants that have been observed above drinking water standards or health advisory limits in storm water drainage well injectate are aluminum, antimony, arsenic, beryllium, cadmium, chloride, chromium, color, copper, cyanide, iron, lead, manganese, mercury, nickel, nitrate, pH, selenium, TDS, turbidity, zinc, benzene, benzo(a)pyrene, bis(2-ethylhexyl) phtlalate, chlordane, dichloromethane, fecal coliforms, methyl-tertbutyl- ether, pentachlorophenol, tetrachloroethylene, and trichloroethylene.” The U.S. Geological Survey (USGS) reports “Many of the contaminants normally associated with runoff from the Nation's highways have the potential for biological effects. ... Highway-runoff contaminants of particular interest throughout the United States include deicers, nutrients, metals, industrial/urban-organic chemicals, sediment, and agricultural chemicals from industrial, commercial, residential, agricultural, and highway sources.”  In addition to the problem of chemical contaminants in stormwater, this USGS report also identifies problems of physical habitat disturbance that Best Management Practices (BMPs) do not eliminate, “Some of the most substantial biological changes caused by development are directly or indirectly related to altered hydrology. Despite efforts to use BMPs to attenuate the hydrologic effects of development, increased peak flows and more flashy runoff will cause physical modifications to the channel shape, bed substrate, and banks of receiving waters, with corresponding effects on aquatic habitat and biota. Loss of forest canopy, increases in paved area, and shallow and(or) muddy detention areas also may cause thermal pollution problems, which can exacerbate chemical stressors on aquatic organisms in receiving waters.”  U.S. Congress prohibits Class V stormwater wells to be authorized by permit or by rule where they endanger drinking water sources.

[I would really suggest removing this section about injection wells. It is cluttered, includes too long of quotes, uses too much jargon, and doesn't really have a clear point. Furthermore, much of the information discussed is covered more clearly in other sections of the paper.]

Stormwater Geochemistry

In addition the contaminants and potential pollutants being carried by stormwater runoff, urban runoff by itself is also recognized as a contaminant. In natural catchments (watersheds), surface runoff entering waterways is a relatively rare event, occurring only a few times each year and generally after larger storm events. {No source} Before development of a catchment, most rainfall soaked into the ground and contributed to groundwater recharge or was recycled into the atmosphere by vegetation through evapotranspiration. These processes naturally treat contaminated water. Without these interceptions, contaminated stormwater runoff contributes directly to nearby surface waters. The ions, elements, and minerals present in contaminated runoff results in a unique chemical composition that may interact with the chemistry of receiving waters. These environmental aspect makes stormwater interact in unique ways with other surface waters in respect to chemistry mechanisms.

One major aspect of stormwater that makes its interactions with surface water notable is its temperature. Because stormwater is typically washing over concrete surfaces, it is a higher temperature than "natural" surface waters. These temperature gradients can increase biological process rates, sometimes creating hypoxic or anoxic conditions in warm climates.

*include mechanism that creates hypoxic conditions?*

Stormwater also delivers increased nutrient loads to waterways, such as nitrate, total dissolved nitrogen, orthophosphate, and dissolved organic carbon. Nutrient loading can result in increased geochemical processing, as there is a greater concentration of limited reactants delivered to the stream. Nutrient loading also can contribute to mass export of nutrients, sometimes resulting in eutrophication of downstream waters. Export of nitrogen and phosphorus compounds, as well as dissolved organic carbon, is generally higher in urban stormwater. Nitrogen concentrations can increase in rivers for hundreds of kilometers downstream of urban centers. Efficient delivery of nutrients to streams due to impervious flowpaths can decrease retention times, and effectively eliminate the potential for biological removal before surface water discharge. Phosphorus enters urban catchments via wastewater and fertilizers applied to lawns. Phosphorus nutrient processes occur predominately is soils, and phosphorus stored in soils can be disrupted and mobilized by soil erosion, added more to phosphorus loading in urban streams.

Calcium, sodium, potassium, and magnesium are other ions common in stormwater. Road deicing can increase sodium concentrations in streams in colder climates where salt is added to the roads to enhance ice and snow melt. The combination of ions that are present in high concentrations in stormwater result in increased conductivity. Conductivity is often a geochemical indicator of highly reactive water, as it is a measurement of the concentration of ions in the water.

Land use is a major factor in the type of pollutants in stormwater. Catchments with >10% industrial land use will see an increase in metals and hydrocarbons in stormwater. Erosion due to stormwater implications on stream geomorphology results in increased sediment loading in urban streams. The quality of sediments in urban streams then depends on the catchment geology and the types of minerals found in these sediments.

The unique geochemical conditions of stormwater can sometimes result in unpleasant phenomenon in urban streams. In surface waters depleted in oxygen, which can be a common result of stormwater contamination, metals may precipitate with sulfide and stain the water black. Sulfate-reducing microorganisms may interact with excess sulfate in urban waste and form odorous H₂S. "Stinky" water can also occur due to the reduction of excess nitrogen compounds created by anaerobic conditions.

Implication on Downstream Processes

In addition to delivering higher contaminants from the urban catchment, increased stormwater flow can lead to stream erosion, encourage weed invasion, and alter natural flow regimes. Native species often rely on such flow regimes for spawning, juvenile development, and migration.

Excess nutrient loading resulting from stormwater is problematic for stream wildlife because microorganisms utilizing the available nutrients deplete dissolved oxygen in the water. This can lead to eutrophification of downstream ecosystems.

Stormwater Management

Managing the quantity and quality of stormwater is termed "Stormwater Management." Although stormwater management has played a role in societies since ancient times, the way stormwater management is addressed today has been greatly influenced by increasing knowledge of anthropogenic deterioration of downstream water quality. The development of "integrated stormwater management" inspires urban water systems to mimic the natural water cycle to reduce pollutant discharge.

The term Best Management Practice (BMP) or stormwater control measure (SCM) is often used to refer to both structural or engineered control devices and systems (e.g. retention ponds) to treat or store polluted stormwater, as well as operational or procedural practices (e.g. street sweeping). The development of stormwater management measures includes both technical and institutional aspects to guide design choices.

History

Historical goals of stormwater management included flood prevention, agriculture irrigation, and conveyance systems. Floodplain waters were diverted to agricultural fields as early as 6000 b.c.e. in ancient Egypt and Mesopotamia. Stormwater management in the form of urban drainage dates back to at least 3000 b.c.e. One of the first mentions of stormwater regulations was by King Hammurabi in Mesopotamia, 1760 b.c.e.^[1] The Code of Hummurabi requires citizens to properly maintain dams and to be mindful about flooding downstream neighbors. In ancient times, flooding was countered by man-made dams or detention basins. A specific example of an early stormwater runoff system design is found in the archaeological recovery at Minoan Phaistos on Crete.

Increasing urbanization and the industrial revolution led to more densely populated cities. Increased imperviousness paired with increased industrial waste and human sanitation pollution made stormwater and water quality a prevalent issue. For example, in London, inadequate sewage infrastructure seeped into the River Thames, polluting freshwater sources with human waste and industrial discharge. This time, known as the "Great Stink," encouraged upgraded sewer systems in the city which are still utilized today. It wasn't until the Clean Water Act in 1972, however, that legislation addressed water pollution in the United States. the law set water quality standards for industrial discharge, prohibited pollutant dumping, and set water quality standards for surface water contaminants.

Despite the Clean Water Act, water quality of urban stormwater runoff did not become a concern until the 1990s. Revisions to the Clean Water Act required municipalities to report the quantity of contamination discharged with their stormwater.^[1] The stormwater rule based on the 1987 Stormwater Amendments became effective on December 17, 1990. Under this amendment, cities with large populations were required to get NPDES permits for their stormwater drainage systems.^[1][3] New urgency for infrastructure that not only mitigated flooding but also contamination paved the way for the modern stormwater management practice of "Integrated Stormwater Management."

Objectives - THIS WHOLE SECTION NEEDS CITATIONS - Also, it's unclear whether this is "too much" information for this page or if a separate Stormwater Management page might be needed

Objectives of stormwater management are generally to reduce the quantity of pollutants and to mitigate flooding. More specific objectives may be outlined by a client commissioning a specific design. For example, it may be important for a design to be aesthetically landscaped and add to the curb appeal of a property. Some objectives may be based off of policy or bureaucratic requirements. General examples of both technical and policy aspects can be found below.

Technical Aspects

Technical aspects are criteria based on basic goal parameters. Technical aspects are probably outlined in the specs for an engineering design project and are kept in mind throughout the process. Some examples of these criteria are:

• control of flooding and erosion;
• control of hazardous materials to prevent release of pollutants into the environment (source control);
• planning and construction of stormwater systems so contaminants are removed before they pollute surface waters or groundwater resources;
• acquisition and protection of natural waterways or rehabilitation;
• building nature-based solutions such as ponds, swales, constructed wetlands or green infrastructure solutions to work with existing or "hard" drainage structures, such as pipes and concrete channels (constructed wetlands built for stormwater treatment can also serve as habitat for plants, amphibians and fish)

Institutional and policy aspects

Institutional and policy aspects may be desires for specific goals set by a municipality or agency. Some examples of these aspects are found below:

• development of funding approaches to stormwater programs potentially including stormwater user fees and the creation of a stormwater utility;
• development of long-term asset management programs to repair and replace aging infrastructure;
• revision of current stormwater regulations to address comprehensive stormwater needs;
• enhancement and enforcement of existing ordinances to make sure property owners consider the effects of stormwater before, during and after development of their land;
• education of a community about how its actions affect water quality, and about what it can do to improve water quality.

Integrated Stormwater Management

Integrated water management (IWM), goes by many names, including low impact development (LID) or "green infrastructure" in the United States, or Water Sensitive Urban Design (WSUD) in Australia. Integrated stormwater management has the potential to address many of the issues affecting the health of waterways and water supply challenges facing the modern urban city. Professionals in their fields related to water management, such as urban planners, architects, landscape architects, interior designers, and engineers, often consider integrated water management as a foundation of the design process.

IWM is aimed towards reducing impervious surfaces and increase the presence of aesthetically pleasing landscaped areas in urban settings. IWM is also used to improve runoff quality, reduce the risk and impact of flooding and deliver an additional water resource to augment potable supply. The methods are often designed to capture the "first flush" of stormwater carrying the bulk of pollutants, and pactices are often sized to carry the first 1 inch of precipitation from a storm event.

·        {might be nice to include a "first flush" example plot}

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 (to restore the natural recharge of groundwater), biofiltration or bioretention (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 LID. The most popular is to incorporate land-based solutions to reduce stormwater runoff through the use of retention ponds, bioswales, infiltration trenches, sustainable pavements (such as permeable paving), 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, biofilters, 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 the environment and water resources.

Affects on geochemistry

While scientific studies investigating the impact of green infrastructure practices on geochemistry of waters are still limited, there is evidence that BMPs can have a positive impact on the geochemistry and water quality of streams downstream of BMPs. The increased infiltration in bioremediation practices allow for microorganisms to process nutrients, which results in decreased concentrations of total nitrogen, phosphorus, and carbon. This improves biodiversity by increasing bioavailability of these nutrients. SCMs can also decrease total dissolved solids and overall polluted stormwater runoff.