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FAQs - Stormwater


What is stormwater runoff?

Stormwater runoff is water from rain or melting snow that "runs off" across the land instead of seeping into the ground. This runoff usually flows into the nearest stream, creek, river, lake or ocean. The runoff is not treated in any way.


What is polluted runoff?

Water from rain and melting snow either seeps into the ground or "runs off" to lower areas, making its way into streams, lakes and other water bodies. On its way, runoff water can pick up and carry many substances that are left on the ground, near or in the gutters, these substances pollute waterbodies.

Pollutants like pesticides, fertilizers, oil and soap are harmful in any quantity. Other substances such as sediment from construction sites, bare soil, agricultural land, pet waste, grass clippings, and leaves can harm creeks, rivers, lakes, and ultimately the ocean in sufficient quantities.

In addition to rain and snowmelt, various human activities like over or excessive lawn watering, car washing, and malfunctioning septic tanks can also put water onto the land surface. Here, it can also create runoff that carries pollutants to creeks, rivers, lakes, and the ocean.

Polluted runoff generally happens anywhere people use or alter the land. For example, in developed areas, none of the water that falls on hard surfaces like roofs, driveways, parking lots or roads can seep into the ground. These impervious surfaces create large amounts of runoff that pick up pollutants. The runoff flows from gutters and storm drains to streams, ending at the ocean. Runoff not only pollutes' but erodes streambanks. The mix of pollution and eroded dirt muddies the water and causes problems downstream.

What causes polluted stormwater runoff?

Polluted stormwater runoff generally happens anywhere people use or alter the land. People going about their daily lives are the number one source of stormwater pollutants. Most people are unaware of how they impact water quality. Some common examples include over fertilizing lawns, excessive pesticide use, not picking up pet waste, letting oil drip out of their vehicles, and littering. Developed areas in general, with their increased runoff, concentrated numbers of people and animals, construction and other activities, are a major contributor to pollution, as are agricultural activities. Other contributors include forest harvesting activities, roadways, and malfunctioning septic systems.

Why do we need to manage stormwater and polluted runoff?

Polluted water hurts the wildlife in creeks, streams, rivers and lakes, as well as creates hazardous conditions for beach goers and recreational ocean users. Dirt from erosion, also called sediment, covers fish habitats and fertilizers can cause too much algae to grow, which also hurts wildlife by using up the oxygen they need to survive. Soaps hurt fish gills and fish skin, and other chemicals damage plants and animals, in addition to cause beach closures when they enter the water.

The quantity of stormwater is also a problem. When stormwater falls on hard surfaces like roads, roofs, driveways and parking lots, it cannot seep into the ground, so it runs off to lower elevation areas. To give you an idea of the difference a hard surface makes, consider the difference between one inch of rain falling onto a meadow and a parking lot. The parking lot sheds 16 times the amount of water that a meadow does!
Because more water runs off hard surfaces, developed areas can experience local flooding. The high volume of water also causes streams banks to erode and washes the wildlife that live there downstream.


How are stormwater and runoff "managed"?

"Best Management Practices (BMPs)" is a term used to describe different ways to keep pollutants out of runoff and to slow down high volumes of runoff.
Preventing pollution from entering water is much more affordable than cleaning polluted water! Educating residents about how to prevent pollution from entering waterways is considered a best management practice. Laws that require people and businesses involved in earth disturbing activities (such as construction and agriculture) to take steps to prevent erosion are another way to prevent stormwater pollution. There are also laws that prohibit littering and others that encourage cleaning up after pets and recycling used oil, paints, tires, and batteries; ultimately preventing substances from entering in to storm drains.

Another way of preventing stormwater pollution is the use of "structural BMPss" such as detention ponds. Detention ponds are built to temporarily hold water so it seeps away slowly; they fill up quickly after a rainstorm and allow solids like sediment and litter to settle at the pond bottom. Then, they release the water slowly. Other examples of "structural BMPs" include: Green roofs, storm drain grates, filter strips, sediment fences and permeable paving.

If it only affects streams and creeks, why should I care?

Streams and creeks feed into rivers, lakes and the ocean. We all drink water or go to the beach sometime, so we are all affected when our water is polluted. When water treatment costs rise, the price of drinking water goes up. If you like to fish, swim or boat, you may have heard or been affected by advisories warning you not to swim, fish or boat in a certain area because of unhealthy water or too much algae. Shellfish like clams and oysters cannot be harvested from polluted waters, so anyone that enjoys these foods or makes a living from the shellfish industry is affected. Money made from tourism and water recreation can also be impacted, as are businesses and homes flooded by stormwater runoff. When we pollute our water, everyone is affected!

What can I do to reduce the amount of stormwater pollution I contribute?

If you own a car, maintain it so it does not leak oil or other fluids. Be sure to wash it on the grass or at a car wash so the dirt and soap do not flow down the driveway and into the nearest storm drain.

If you own a yard, do not over fertilize your grass. Never apply fertilizers or pesticides if rain is forecasted within 48 hours. If fertilizer falls onto driveways or sidewalks, sweep it up instead of hosing it away. Mulch leaves and grass clippings and place leaves in the yard at the curb (in the greenwaste bin), not in the street. Doing this keeps leaves out of the gutter, where they can wash into the nearest storm drain. Turn your gutter downspouts away from hard surfaces, seed bare spots in your yard to avoid erosion and consider building a rain garden in low-lying areas of your lawn.

If you have a septic system, maintain it properly by having it pumped every three to five years. If it is an older system, be sure it can still handle the volume placed on it today. Never put chemicals down septic systems, they can harm the system and seep into the groundwater.

Pet owners should pick up after their pets and dispose of pet waste in the garbage. -- Keep lawn and household chemicals tightly sealed and in a place where rain cannot reach them. -- Dispose of old or unwanted chemicals at household hazardous waste collections sites or events. -- Never put anything in a storm drain.-- Don't litter.

How else can I help reduce stormwater pollution in my area?

Participate in the next community cleanup in your area. Help stencil storm drains at a storm drain stenciling event, these events are a fun way to let your neighbors know the storm drain is only for rain. Attend public hearings or meetings on the topic so you can express your concerns. Report stormwater violations to the San Dimas Department of Public Works at (909) 394-6240. Keep learning about polluted stormwater runoff and tell a friend!

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