Green sludge in drainage swale

Asked June 5, 2018, 2:06 PM EDT

We have a drainage swale that we had installed by a landscaper in our back yard in Junction City. Our home is new construction (we moved in January of 2017), and the builder didn't realize how soggy the backyard got. When we had the landscaper come out and evaluate it (late spring/early summer of 2017), he advised that since the area had been farmland, and was known to be in a gray area of the flood plain, he suspected that we were simply getting water run off from our neighbors yards. He designed a plan that allowed for a small indentation with rocks and sand to retain the water and allow it to drain naturally to the water table. We discussed putting in wetland grasses but did not at that time. Since then, a small amount grass has volunteered in the bottom. But since this spring has started, we've noticed a high volume of green sludgy stuff that blooms out. I'm wondering if it's "algae bloom" which I've read is really a type of bacteria, and if it's being fed from the fertilizers our neighbors might be using. Where would I bring a sample of this stuff to be sure? Would putting it in a zip lock bag be sufficient? Would adding sand and perhaps more grasses at the bottom of the swale help filter that out if it is bacteria or even a more benign algae? It doesn't stink, but it gets out of control and I've noticed it bumps our histamine reactions when we try to clean it out.

Lane County Oregon

6 Responses

OSU does not provide this type of testing, however I believe that the private lab in Eugene Delta Environmental may be able to test it - or link you with a lab that can provide that service Here is there contact information Address: 105 E Hilliard Ln, Eugene, OR 97404 Phone: (541) 689-3177

This number rings with no answer. Do you have any idea based on the pictures what this might be? Is there an alternate person locally I could ask for help?

Original poster here - I drove by that address, and Delta Environmental is no longer there. The building is available for rent, in fact. Are they any alternate resources you could recommend?

That plant looks like filamentous algae. All you need to grow it is a little surplus nutrients/fertility standing water and sunlight. It can grow anywhere in the US and beyond. A really good site to see more about it and how to manage it is AquaPlant at the Texas A&M website. https://aquaplant.tamu.edu/plant-identification/alphabetical-index/filamentous-algae/

I think after you read the information there, you will decide testing is not needed and management is all that is needed. Denser stand of grass in the waterway leading to you puddle will assist the management of nutrients flowing into your puddle.

Thank you very much! - Original Poster

If you can establish other aquatic plants that grow above the water to provide shade, they will help you limit the algae growth.

Filamentous algae are single algae cells that form long visible chains, threads, or filaments. These filaments intertwine forming a mat that resembles wet wool. Filamentous algae starts growing along the bottom in shallow water or attached to structures in the water (like rocks or other aquatic plants). Often filamentous algae floats to the surface forming large mats, which are commonly referred to as “Pond scums.” There are many species of filamentous algae and often more than one species will be present at the same time in the pond.Filamentous algae has no known direct food value to wildlife.