Creek Care

Pollution

Natural organisms are so attuned to their habitat that virtually any pollutants we add to the environment will have a detrimental effect. The more harmful pollutants are those that tend to remain unchanged in some damaging form, and those that are effective in low concentrations; some combinations of pollutants can also be unexpectedly lethal. On the other hand, if a specific pesticide is used by many people, it may be cumulatively more detrimental to wildlife than if a variety of pesticides are used. 

Categories of Pollutants

These categories of pollutants can be defined: 

• Substances that degrade the aquatic environment: Sediment covers spawning gravel and can reduce plant photosynthesis. Plant fertilizers and the phosphates in some detergents over-stimulate the growth of aquatic plants, that, on dying, deplete the oxygen supply available to fish. Decomposing garden clippings also consume dissolved oxygen. 

• Substances that quickly make life unsupportable: Oil and grease destroy the ability of fur and feathers to trap an insulating air layer, and they prevent insects from breathing. Fine particles eroded from tires washed into creeks are fatal to salmon and trout. Sediment can clog the gills of fish. 

• Substances that have a physiological effect: Saltwater intruding into freshwater habitats may alter the flow of liquid across body membranes. Lead and many pesticides affect the nervous systems of animals and insects. Detergents impact the gills of fish and can be harmful even at low concentrations. 

• Substances that upset animal metabolism: Chlorine from swimming pools is transformed in the environment into carcinogenic dioxin. Heavy metals from paint, car batteries, and brake pads accumulate in organisms low in the food chain and cause debilitating sickness in higher species. Some substances disrupt the immune system of animals. 

• Substances that undermine the reproductive system. Selenium deforms fetuses. DDT makes birds’ eggshells so fragile that they break in the nest. Medicinal hormones survive sewage treatment and can then disrupt fish reproduction. 

• A specific chemical, 6PPD-quinone is a chemical released from automotive tires that ends up in roadway dust and can run into streams where it is highly toxic to salmonids. The chemical is created when 6PPD, a preservative that helps tires last longer, reacts with ozone in the atmosphere.   

• Insecticides and herbicides (including swimming pool algaecides) may continue to be lethal when they reach the creek corridor. The elimination of microscopic organisms low in the food chain affects fish and animals that feed upon them. Pesticides survive sewage treatment operations, so they should not be poured down the sink. 

• Bacteria and pathogens from sewer leaks, malfunctioning septic systems, and animal waste can spread disease. 

In the creeks of our watershed, most of the pollutants come from non-point sources—surfaces exposed to stormwater runoff: roofs, streets, sidewalks, driveways, parking lots, business properties, lawns, and gardens, as opposed to point sources like the discharge from a factory. Non-point source pollution from these areas, which cover much of the residential and commercial area, flows into the storm-drain system’s network of gutters, catch basins, channels, culverts, and pipes. In some cases, for example at commercial car washes, collected water is treated. Unfortunately, in most case, storm water flows directly into local streams and on to San Francisco Bay without treatment to remove pollutants. The storm drain system is separate from the sanitary sewer system, which collects wastewater from households and commercial buildings and sends it to a wastewater treatment plant before discharging it into the Bay. 

Low Impact Development (LID), a sustainable practice that improves water quality and benefits water supply, is becoming more and more popular. Unlike traditional storm water management, which collects and conveys storm water runoff through storm drains, pipes, or other conveyances to either a centralized storm water facility or directly into creeks, LID takes a different approach. The goal of LID is to mimic a site’s predevelopment hydrology by using design techniques that infiltrate, filter, store, evaporate, and detain runoff close to the source of rainfall. Some common LID practices include: bioretention facilities or rain gardens, grass swales and channels, vegetated rooftops, rain barrels, cisterns, vegetated filter strips, and permeable pavements. The median in Red Hill Avenue, in San Anselmo, as you enter the Town from San Rafael is good example of a vegetated filter strip. The landscaped islands at the Village Shopping Center in Corte Madera are good examples of bioretention facilities. Both slow run-off and remove pollutants before they get to the creek or bay. 

Minimizing Pollutant Use 

We can minimize our impact on the watershed by minimizing the use of polluting substances, cleaning up spills immediately and disposing of them properly. Sweep up dry materials such as cement or fertilizer; don’t attempt to wash them away with water or bury them. Clean up liquid spills on paved surfaces by using absorbent materials like cat litter, sand or rags. Keep all paint wastes including solvents and paint-stripping residues, paint chips and dust, and sandblasting wastes away from gutters, streets, and storm drains. Dispose of these wastes appropriately, either in the garbage if they are not hazardous, or at a hazardous waste collection point. So-called biodegradable products may take months to break down, so such labeling is no assurance of the product’s safety. It is worth remembering that many of the chemicals we are in the habit of using have persistent effects on the environment, and that disposing of them merely passes on the problem to someone else’s watershed. 

For more detailed information on watershed pollution prevention visit the Marin County Stormwater Pollution Prevention Program web site, www.mcstoppp.org.