Citizen E. coli Monitoring on Four Mile Run


(Conservation Currents, Northern Virginia Soil and Water Conservation District)

Early on a chilly October Saturday, a hardy volunteer fills a small vial with cold stream water. The tiny allotment is a water quality sample, one of the first being taken as part of a new citizen bacterial monitoring program on Four Mile Run.

In twelve watersheds throughout the state, including Four Mile Run, the Virginia Department of Environmental Quality (DEQ) is training citizen volunteers like this one to conduct monthly bacterial sampling on some of Virginia’s more polluted streams. Specifically, these dedicated volunteers are sampling for the bacterium E. coli.

If you’ve heard of E. coli – probably in the context of improperly cooked meat or unpasteurized apple juice – you may be wondering how this organism relates to streams. E. coli (an abbreviation for Escherichia coli) belongs to the fecal coliform group of bacteria. These microscopic rod-shaped organisms utilize lactose (a major sugar of milk) and reside in the digestive tracts of warm-blooded animals – including humans. Since fecal coliforms occur in the lower intestines, they are found in the feces of the organisms they inhabit. Many fecal coliforms can also survive in external environments like water bodies, meat or mud. In urban streams, human sewage, pet waste and, less frequently, wildlife (particularly geese) are the primary sources of E. coli.

The presence of E. coli – and fecal coliform bacteria in general – in a waterbody indicates that fecal waste from warm blooded animals is contaminating that lake, pond or stream. Although E. coli is rarely pathenogenic (one exception being strain O157:H7, found in cattle), many other disease-causing organisms, including cholera and cold viruses, can be transmitted via fecal contaminated waterways. Scientists monitor E. coli because of the bacterium’s reliability as a water quality indicator; observations about E. coli levels can be used to determine if enough fecal contamination is occurring in a waterbody to make humans sick.

E. coli and Four Mile Run

Low levels of E. coli are found even in healthy, natural streams. Four Mile Run and its tributaries drain one of the most heavily urbanized basins in Northern Virginia. The 20 sq. mile Four Mile Run watershed includes portions of four localities (the counties of Arlington and Fairfax and the cities of Alexandria and Falls Church) and is home to over 160,000 people. Approximately 11,000 dogs generating up to 5,000 lbs. of waste a day live in this urban watershed.

In 1996 and again, in 1998, Four Mile Run was included on the Virginia Impaired Waters List for exceeding the fecal coliform water quality standard (currently 200 cells/100 mL water). With bacterial levels above the standard, Four Mile Run is not safe for swimming or fishing since contact with its water may cause human infection. In addition to indicating that the waterbody may pose a human health risk, elevated E. coli levels can correlate with excess concentrations of heavy metals and phosphates due to runoff. All of these sources can negatively impact the biological health of Four Mile Run and, by extension, the Potomac River and the Chesapeake Bay.

Federal Clean Water Act statutes require a state to develop a TMDL (Total Maximum Daily Load) allocation study, essentially a fecal coliform “pollution budget,” once a waterbody is listed as impaired. The TMDL must include a strategy for reducing pollutant loads to ensure that the water quality standard is achieved. Bacterial water quality monitoring is essential for identifying how and where fecal contamination is occurring, and for measuring TMDL-related improvements in water quality.

Citizen E. coli monitoring

Despite significant general interest in coliform contamination, involvement of the public in bacterial monitoring has previously been limited by the high cost of commercial methods and the need for specialized facilities. The development of the Coliscan® method (Micrology Laboratory; www.micrologylabs.com), the low-cost and simple sampling technology being used by DEQ as well as other agencies and organizations nationwide, has made citizen E. coli monitoring feasible.

Petri dish with incubated media and bacterial coloniesIn the Coliscan® method, volunteers mix liquid Coliscan® Easygel® growth medium with each stream water sample. When added to a chemically pre-treated petri dish, the mixture solidifies into a gel. Overnight, as the media incubates, small purple, red or blue bacterial colonies grow on its surface. Volunteers count the number of colonies and perform basic calculations to determine the E. coli concentration for each sample. Although only 80 percent as accurate as commercial laboratory techniques, the Coliscan® method is easy for volunteers to learn, requires simple equipment that can be stored at home, and is 10 times less expensive than commercial analyses.

Over the next year, a team of local volunteers will use the Coliscan® method to sample for E. coli at 10 locations along Four Mile Run. Joanna Cornell, NVSWCD’s volunteer stream monitoring coordinator, and Aileen Winquist, an environmental planner with Arlington County, are the local facilitators of the bacterial monitoring effort. “We had a lot of volunteers eager to do the E. coli monitoring, and it will be interesting to see if we find any bacterial hot spots in the watershed,” said Winquist. “The volunteers like the program because they can make a real contribution,” she adds. “The monitoring is easy to undertake and very rewarding.”

James Beckley, Water Quality Data Liaison for DEQ and the manager of the citizen bacterial monitoring initiative, is equally positive. “When a community monitors a stream themselves, they see first hand that there’s a problem. It’s a great opportunity to reach the community about water quality issues.” When people understand how fecal contamination occurs, they often make simple changes like picking up after a pet that can make a real difference for a stream.

Although the citizen monitoring program does have an educational component, DEQ is primarily interested in the observations being made by program volunteers. ”We are relying on volunteer monitoring to improve the level of information we have on these impaired streams. Instead of one or two samples per watershed,” Beckley notes, “we can sample each tributary.”

Citizen data is already being used by DEQ to identify fecal coliform hot spots in TMDL watersheds, and to prioritize and assess water quality improvement efforts. “This program is about obtaining real data that will allow DEQ to make real water quality determinations.” Adds Beckley, “We’re already starting to see some interesting trends.”


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