Dissolved oxygen in water is necessary for fish to live. Organic material from excess nutrients, effluent from sewage treatment plants, materials creating colors, and organic material from industrial plants or nature use up the dissolved oxygen, thereby causing an oxygen depleted water environment resulting in plants and fish dying. This is highly detrimental to water quality.
Best Practices for Low Dissolved Oxygen
(See Best Practices for Oxygen-Demanding Substances)
Non-Point Sources of Contamination
(See endnote 21)
A pollutant that comes from a non-point source of contamination is any pollutant that does not come from a specific and discrete source of contamination, such as a ship or factory, including stormwater and runoff from urban and agricultural areas. Stormwater from heavy rains falls on a variety of surfaces including sidewalks, yards, driveways, roofs, parking lots, etc., and carries pollutants from littering by individuals, trash and recyclables, pet waste, lawn fertilizers and pesticides, residue from washing cars, residue from motor oil and other contaminants from cars, and leftover hazardous chemicals and paint which are exposed to the rain. Industrial stormwater typically introduces into surface bodies of water substantial quantities of total suspended solids, oxygen-demanding materials, nutrients, metals, hazardous chemicals, and other common pollutants. Runoff is now the most common source of water pollution. Agriculture contributes almost half of the water quality contaminants to rivers and streams and over 40% to lakes, ponds, and reservoirs. Municipal point sources contribute about 37% to the contamination of estuaries. Hydrologic modifications contribute to 20% of the water quality problems in rivers and streams and 18% in lakes, ponds, and reservoirs. Urban runoff and contaminated storm sewer water contribute 32% of the water quality problems to estuaries, while contributing 18% to lakes, ponds, and reservoirs. Industrial discharges contribute 26% of the water quality problems of estuaries and atmospheric deposition 24%.
Runoff from golf courses which contains substantial amounts of fertilizer and pesticides can contaminate groundwater or surface water. Non-point source pollution intensifies with the amount of rain or melting snow in a given area and in a given period of time. The contaminants on the surface of the ground carried into bodies of water may include sediments, pathogens, fertilizers, nutrients, hydrocarbons, metals, oil, grease, toxic chemicals, and acid drainage.
Best Practices for Non-Point Sources of Contamination
- • Before digging up the land for any purpose, develop and implement an approved erosion and sediment control plan. Evaluate the plan as the construction proceeds to determine if the goals and objectives are being met and if not modify the plan to do so.
- • Identify and prioritize using sound scientific techniques and data, the potential threats to human and ecosystem health from non-point source contamination in a given area.
- • Reduce erosion in any type of construction or farming and retain sediment on site.
- • Avoid off-site transportation of waste material and chemicals where appropriate.
- • Minimize the use, storage, and disposal of all types of chemicals which may then become water pollutants.
- • Use small amounts of fertilizer on properties and sweep up driveways, sidewalks, and gutters.
- • Do not dump anything down storm drains or in streams.
- • Plant vegetation where there are bare spots in the yard.
- • Compost the yard waste.
- • Use the least toxic pesticides on the property.
- • Direct downspouts to grassy areas instead of paved areas.
- • Do not wash the car at home.
- • Check the car to make sure there are no types of leaks of oil or other substances.
- • Inspect the septic tank system on a regular basis and have the sludge and other substances removed by a registered sewage hauler before there is an overflow in the system onto the ground.
Some specific techniques for controlling stormwater flow, which at high levels promotes erosion and spread of pollutants, are bioretention cells, elimination of curbs and gutters, grassy swales, green parking lot design, infiltration trenches, inlet protection devices, permeable pavement, permeable pavers, rain barrels and cisterns, riparian buffers, sand and organic filters, soil amendments, stormwater planters, tree box filters, vegetated filter strips, and vegetated roofs. These are explained below.
- • A bioretention cell, also called a rain garden, is a depressed area in which forest material has been placed and is covered by a surface with vegetation. Underdrains are used in these areas to help with filtration and infiltration. The bioretention cell is useful in groundwater recharge, pollutant removal, and containing runoff. It is very useful in parking lots or urban sites where there are very few grassy areas.
- • The elimination of curbs and gutters helps reduce the speed of the flow of rainwater, and allows for infiltration into the ground and also the removal of pollutants.
- • Grassy swales are shallow indentations in the ground that help capture runoff water and increase infiltration into the soil.
- • A green parking lot design utilizes appropriate amounts of parking spaces and grassy areas to allow for infiltration of rainwater flowing off of the concrete or macadam surface.
- • Infiltration trenches are ditches filled with rocks that have no outlets. The runoff from the surface flows into the ditches and infiltrates the soil.
- • Inlet protection devices, also called hydrodynamic separators, are separation units utilized to remove sediments, oil, grease, trash, and other pollutants.
- • Permeable pavement is a porous surface over stone in a hole in the ground, instead of asphalt or concrete surfaces, to allow water to accumulate and disperse through the soil.
- • Permeable pavers are interlocking concrete blocks which have voids to allow water to penetrate the ground instead of running off.
- • Rain barrels and cisterns are containers which are used to capture rainwater to be utilized at another time for household purposes.
- • Riparian buffers are areas near shorelines, wetlands, or streams where development is either restricted or prohibited and the buffer helps manage stormwater.
- • Sand and organic filters are used to remove specific types of pollutants from water before the water penetrates to the groundwater supply or flows to a surface body.
- • Soil amendments, such as soil conditioners and fertilizers, are utilized to increase water retention capabilities in soil. The soil amendments change the physical, chemical, and biological characteristics of the soil and make the soil more suitable for growth of plants and water retention.
- • Stormwater planters are small devices which can be placed either above or below ground and increase the efficiency of the infiltration of stormwater and the filtering of contaminants.
- • In-ground tree box filters contain trees, vegetation, and soil that help filter runoff before it enters a catch basin. Aesthetically they are very pleasing.
- • Vegetated filter strips are bands of dense vegetation for treating runoff from roads and highways, parking lots, and other impervious surfaces before they get to a body of water.
- • Vegetated roofs or green roofs are impermeable roof membranes over which plantings are placed to reduce runoff volume and improve water quality.
Nutrients, including fertilizers, are needed by all vegetative matter for growth. However, excessive amounts enter bodies of water increasing the levels of organic and mineral nutrients allowing algae to grow rapidly and deplete the oxygen supply, causing organic matter to die and producing unpleasant odors. The major components of nutrients include nitrogen and phosphorus.
Nitrogen compounds can be dissipated by uptake by the plants, leaching into surface or groundwater, surface runoff, and losses to the atmosphere when the fertilizers are exposed to sunlight and air, or are stored in the soil. The nitrogen is replaced by humans and if the quantities are too large or if there is a problem of runoff, the nitrogen compounds can enter the bodies of water.
Phosphorus may be found in several different forms in the soil and can be transported by various means to surface bodies of water. Phosphorus may also be found in a variety of chemicals and fertilizers, animal wastes, food wastes, wood and sawdust waste, and anything else that can decompose. It is usually the amount of excess nutrients that controls algae growth in freshwater lakes and leads to oxygen depletion and then the accumulation of sediment as the algae die.
Although ammonia is not a nutrient, it is a nitrogen compound which can have an immediate and deadly effect on humans as well as various ecosystems. Ammonia-based compounds may be used to wash and rinse different types of equipment.
Best Practices for Nutrients (Also see Best Practices for Agriculture and endnote 9)
The use of nutrients for lawns, landscape, golf courses, etc. should be closely supervised by trained people to prevent substantial runoff into bodies of water. This can be accomplished by:
- • Conducting soil, nutrient, and plant tissue tests, to determine the best soil productivity, acidity, and the type and amount of nutrients available. The tests measure the amount of phosphorus and potassium available, the pH of the soil to determine acidity, and the soluble salts to determine the amount of fertilizer already present. With this information and knowledge of the weather conditions and the amount of soil moisture, it is possible to determine the nature, quantity, and type of fertilizer which should be used and how frequently to use it
- • Providing diverse healthy eco-friendly trees, grass, ornamentals, and groundcover for the area involved
- • Using the diversity of the eco-friendly plants to help prevent a specific disease from destroying the landscape, help prevent serious damage due to drought or poor weather conditions, and make the area more aesthetically pleasing