By The Watershed Project staff
California is having a wet winter, and the recent rains provide a chance for us to see how The Watershed Project’s newly constructed bioswales handle stormwater. TWP monitoring teams watch the weather and venture out to observe and document from the moment the rain begins. Our best site for monitoring is the Booker T Anderson Community Center, where water from the parking lot is intercepted by a large bioswale before draining into Baxter Creek. The plants and soil act as a natural filter that cleans the runoff from the pavement. This project was completed last September and it is gratifying to watch it in action so soon after construction.
Curb cuts allow water to flow from the parking lot into the swale. Once the water has filtered down through the swale, this cleaner water collects in an outlet pipe underneath the swale and then discharges to Baxter Creek. Our observational monitoring protocol documents whether water is entering the swale as predicted, whether trash or debris are collecting in the swale, whether sediment is accumulating at the discharge point, and tries to calculate the “hold time” of the swale (the time it takes for water to filter through).
On Friday, February 8 2019 rains were favorable and we collected samples from both the water entering the swale and the filtered water exiting through the drain to the creek. The photos below show the inflow sampling steps. We used a dustpan to collect sheet flow entering the swale through the curb cuts, taking multiple samples over time and mixing them to create one composite sample. This ensures we get a good representation of all the pollutants that are flushed down the watershed during a storm. The samples were then sent to a lab to be tested for a variety of pollutants, including nutrients, heavy metals, pesticides, pyrethroids, oil, and grease. We also took a composite sample from the swale outflow. During this rain event, the hold time in the bioswale before water began flowing into the outflow drain was about an hour and 20 minutes. Stay tuned for the results of our tests!
If you’re interested in participating in bioswale or creek monitoring events, please contact Helen at helen@thewatershedproject.org. Our creek monitors go out every 2nd Friday and we’re looking for volunteers to assist them. You can read more about our activities here under the Citizen Monitoring tab.
