Potomac River - Thompson Boat Center

Thompson Boat Center is taken right off the dock at the boat house, located near Georgetown Waterfront Park and off the C&O canal.

**WARNING: SWIMMING IS PROHIBITED IN D.C. WATERS REGARDLESS OF THE CURRENT STATUS**

A “green” rating demonstrates that the level of E. coli at the time of sampling falls beneath the limit of 126 MPN/100 ml, the numeric standard used for this citizen science initiative to determine whether DC waters are safe and clean enough for primary contact recreation, e.g. kayaking and paddleboarding.

Water quality standards as well as the methods used to determine pass or fail status vary widely across jurisdictions and monitoring programs. We encourage users to explore the sample data in addition to checking the swim guide status. These data can be viewed through the Chesapeake Monitoring Collaborative Data Explorer, https://cmc.vims.edu/#/home

Despite its designation as a Class A Primary Contact waterway, the DC Department of Health (DOH) bans swimming in the Potomac River citing the risk of high bacteria levels after rainstorms as the only reason it is considered “unsafe” to swim. The activation of the Clean Rivers Project in DC is expected to reduce system wide combined sewage overflow by 96%, bringing the Potomac significantly closer to a swimmable river.

A red "special status" update indicates an abnormal situation such as a severe weather event, construction activity, or a combined sewage overflow (CSO) in the past 48 hours. This status means it is extremely likely there are unsafe levels of bacteria in the river, and it is recommended to be extra cautious if you are close to the river or come in contact with the water.

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WATER QUALITY

Passed water quality tests 60-95% of the time
Historical Status
This status is based on the latest sample, taken on September 11th, 2019. Potomac Riverkeeper updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on at

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MONITORING FREQUENCY

SOURCE INFORMATION

Monitoring in District of Columbia waters is supported by the DC Department of Energy and Environment through grant #RFA 2018-1805-WQD-VWQM Project #1 to Anacostia Riverkeeper.

Monitoring occurs every week from May through September. Parameters to be monitored include E.Coli, total coliform, pH, temperature, and turbidity. Detailed monitoring results can be found through the Chesapeake Monitoring Cooperative's Data Explorer, https://cmc.vims.edu/#/home

The primary parameter of concern is E. coli, a fecal coliform. E. coli is measured in terms of the Most Probable Number /100 ml water and are indicators of fecal contamination by warm-blooded animals including birds and mammals. Sampling sites along the Potomac fall within several jurisdictions and monitoring programs. Each jurisdiction has defined their own water quality standards and each program uses its own method for determining a pass or fail site status.

The DC Primary Contact Water Quality Standards are as follows:
• E. coli single sample value = 410 MPN/100mL
• E. coli geometric mean = 126 MPN/100mL

Potomac sites that are under DC jurisdiction are rated against these values. As requested by the DC Department of Energy and Environment, site ratings are determined by the geometric mean value, not the single sample value. This value can only be calculated after five consecutive weeks of sampling. Prior to June 5, site ratings were determined by comparing single sample values to the geometric mean value of 126 to rate sites conservatively. Beginning on June 5th, site ratings will be determined by calculating the actual geometric mean and comparing it to 126 MPN value.

The VA Primary Contact Water Quality Standards are as follows:
• E. coli single sample value = 235 MPN/100mL
• E. coli geometric mean = 126 MPN/100mL

Potomac sites that are under VA or MD jurisdiction are rated against the single sample standard of 235 MPN. After 5 consecutive weeks, the geometric mean will be calculated and recorded for internal analysis but is not used to determine a pass or fail status.

WATER QUALITY GRAPH