Storm water is water that comes from a rain or snow event. It is created when rain falls or snow melts faster than the ground can absorb it. In the urban environment, many surfaces have been altered from their undeveloped state to a more hardened or impervious surface. This causes more runoff to be generated than there was prior to development. In addition to rain and snow events, our storm water system is also used to handle tail waters from flood irrigation, a watering technique used on some properties with sunken landscapes, orchards or gardens.
Why Worry About Storm Water?
Concerns about storm water generally are centered on two issues: quantity and quality.
Too much storm water runoff results in flooding. In order to deal with flooding, urban sites have traditionally relied on moving water as quickly as possible to underground pipes that discharge into lakes or rivers. An alternative approach is to direct surface water to drains that release water underground. Both of these can lead to highly concentrated flows that can negatively affect river banks or that can overtax underground discharge.
Research is now leading to the use of Low Impact Development (LID) strategies and Green Infrastructure. To learn more about these novel approaches, you can read A Guide to Low Impact Development within Utah published by the Utah Department of Environmental Quality.
As far as storm water quality, it is important to recognize that runoff carries whatever pollutants are found on streets, parking lots, sidewalks, rooftops and other hard surfaces to local water bodies without treatment. Storm drains do not lead to the sewer system that treats the water from inside homes and businesses. Storm water systems do not connect to the treatment plant at all.
The City has identified several pollutants of concern that can harm human health, degrade water quality, damage aquatic habitat, and seriously impair ecosystem functions.
- Sediment – Sediment is a common component of storm water. Sediment can aid in the transportation of pollutants such as attached oils, nutrients, chemical contamination, trace metals, and increase the risk of flooding. Sediment is also detrimental to aquatic habitat for fish and plants. Sediment is the primary component of total suspended solids (TSS), a common water quality analytical parameter.
- Nutrients – Nutrients are often found in storm water. These nutrients can result in excessive or accelerated growth of harmful algal blooms, reduced oxygen in the water, changes in water chemistry and pH. In addition, un-ionized ammonia (one of the nitrogen forms) can be toxic to fish. Chemicals like phosphorus, nitrogen, potassium and ammonia are found in fertilizers, pet waste, grass clippings, and decaying leaves.
- Hydrocarbons – Oil and grease include a wide array of hydrocarbon compounds, some of which are toxic to aquatic organisms at low concentrations. Some of these pollutants are toxic to humans and wildlife at very low levels. Hydrocarbons come from vehicle and equipment fluid leaks, pesticides, equipment cleaning, and parking lots.
- Heavy Metals – Metals including lead, zinc, cadmium, copper, chromium and nickel are commonly found in storm water. Heavy metals can be found in vehicle brakes and equipment, parking lot runoff, batteries, paint and wood preservatives, fuels and fuel additives, pesticides, and cleaning agents.
- Debris/Litter/Trash – Not only does trash have the potential of blocking off inlets, it contains pathogens and many of the other pollutants already discussed. It is important to follow proper solid waste handling procedures.
- Pathogens – Bacteria and viruses are contaminates in storm water and can cause adverse health reactions.
It is the City’s goal to reduce or minimize the presence of these pollutants in storm water runoff. There are some common ways that the City tries to minimize the potential impact of pollutants entering storm water runoff. All of this is important because Utah Lake, the Provo River, and Powell Slough are each listed as 303(d) water body. This means it is monitored regularly by the state of Utah for the presence of pollutants. The pollutants listed in the State’s report are Phosphorous, Dissolved Solids, PCB, and Algal Blooms. This monitoring is meant to ensure that these bodies of water are safe for recreational activities and for fish and other wildlife.