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Action Log


Nancy Gehman

What: Other - Greenish Water

Where: Bennington Tributary

When: the week of August 14th

Action Taken: Odd greenish water (and sometimes suds) in the Bennington Tributary of Sligo Creek was reported by Nancy Gehman via the Water WatchDog email to the County's water quality enforcement team the week of August 14.

In an impressive bit of detective work, Steve Martin and members of his team (Alex Torella and Susan Allen) at the County's Department of Environmental Protection (DEP) think they tracked down the cause of the green water - but not the suds:

"...Whiting Turner (WT) was dewatering the swimming pool in the new United Therapeutics Unisphere Building. The building contains a swimming pool that holds 58,000 gallons of water. The pool, which is currently exposed to the outside elements, was filled with water to check for leaks. The untreated water was in the pool long enough to grow green algae. Starting the (Monday) morning of August 14th, they began emptying the pool by using a pump to convey the water to their stormwater treatment device located on site. After the water runs through the treatment device it’s discharged into a storm drain at the corner of Colesville Road and Spring Street. The pumping continued on a continuous basis until around 10am on Tuesday, August 15th. The quantity of water pumped and the timing of when the green water was observed at the outfall leads me to believe this was the likely source.

According to WT, they will be performing some additional leak testing on the pool, so we may see a repeat of this. I asked them to let me know ahead of time so I can get the word out. WT offered to add chemicals to the water to prevent the algae growth and I told them no. The algae, while aesthetically unpleasing, is preferable to adding chemicals to the water that may be toxic to aquatic animals. Since the water was discharged through an approved stormwater treatment device, I would not consider this to be a violation of the water quality code."

Thanks to Nancy, Steve and his team for their remarkable and continuing commitments to protect the Creek.

Unfortunately the suds observation remains a mystery, as does the possible concrete wash out or latex paint pollution also spotted in the Tributary in the past week or so.

If anyone spots pollution in Sligo Creek, or entering a storm drain from the street or sidewalk (you might see it first downtown !), please send an email with the location, time of event, and if possible a photo, as soon as possible to: ReportSligoPollution@fosc.org. Thank you for supporting Sligo Creek and the Anacostia Watershed.