The first major rain event of the year is often referred to as “first flush,” because it brings with it all the pollution that has built up on roads and other surfaces over the summer. First flush is a phenomenon brought on by our Mediterranean climate with it’s warm, dry summers where it doesn’t rain for as much as six months. It’s always hard to tell when we will get that first rain of the fall, but it’s usually sometime between September and November. First flush is a great time to test for pollutants in the stormwater, or in creeks (which is where the stormwater goes), as pollutant concentrations will likely be higher than they would be in subsequent rain events, when they will not have been building up for as long.
Last fall, volunteers all over Contra Costa County participated in The Watershed Project’s first flush monitoring effort, and used dip strips to test stormwater for metals, nitrates, pH, and more. You can see the results of their efforts here.
What we found is that higher-than-desired levels of copper and nitrates were present at many sites. Copper is mainly from the brake pads of cars; it is an essential trace nutrient for life in the creek, but in higher amounts it can be toxic. Nitrates are found in fertilizers and in human and animal waste, and like copper, it is essential to life in small amounts but in larger amounts it can lead to overgrowth of algae and subsequent low oxygen areas (referred to as “dead zones”).
This year we’re repeating the dip strip monitoring, and we’re also adding a test for detergents! Detergents are added to insecticides to increase their effectiveness by making the chemicals more soluble in water, and thus easier to spray and penetrate their intended targets. Detergents are much easier (and cheaper) to test for than insecticides, and can be used as a proxy. Some other sources of detergents can include washing cars and faulty greywater systems.
How can you get involved? Please contact Sarah Haselton if you are interested in participating in our first flush monitoring effort this year, and we will mail you supplies and instructions. Here are the options:
- Dip strips are easy and can be read on-site; they are perfect for students, or if you don’t want to drive to Richmond.
- Detergents samples must be delivered to The Watershed Project office in Richmond for analysis within 3 hours of collection, which will take more time and you’ll probably need access to a car.
- And of course, you’re welcome to do both!
