"If the water is moving, it's always going to rejuvenate a lot faster than something stagnant," said Oscar Flite, the research director at the Southeastern Natural Sciences Academy, which has monitored bacteria levels in the Savannah River for several years.
"You looked in a lot of places we didn't look -- like creeks and pipes that could have leaks," he said, noting that the academy's long-term averages for the river involve large volumes of fast-flowing water.
Those studies, he said, place fecal coliform values in the main river channel well under the 200 colony forming unit margin, when averaged over long periods of time.
Levels can also change overnight, he said. "Keep in mind that fecal coliform in sediment can be as much as 700 times higher than overlying water, so think about a heavy rain coming through and releasing a lot more."
The academy's Phinizy Swamp Nature Park uses a constructed wetlands complex to help clean up water from the city's wastewater plant before it flows down Butler Creek to the Savannah River. Although the city's plant is well-managed, and the wetlands capably filter waste, other factors can still create elevated fecal coliform levels.
As many as 16 million blackbirds have been counted at those wetlands in a single year, he said. Such a population can create ample volumes of droppings, both at the wetlands site and other areas where they might migrate.
"A lot of what we do in our own backyards is directly related to these levels," he said. "An organic gardener using cow manure could create runoff that gets in a stream. And how many people don't pick up pet waste? All those things can affect the numbers."
Development meant to preserve streams can also help inflate fecal coliform levels, he added.
"When we build a subdivision, we cut down all the vegetation and the only place that harbors a lot of wildlife is along stream corridors, which is right there along the streams."
Frank Carl, a retired Medical College of Georgia professor and former Savannah Riverkeeper director, said the numbers collected during The Chronicle's Aug. 12 sampling blitz likely represent a good cross-section of water quality in the area -- at least where fecal coliform is concerned.
"Except for the highest three or four numbers, the results are not surprising," he said "But that doesn't mean we can't do a better job keeping our water clean."
Carl said education goes a long way in encouraging people to think about water quality. Georgia's "Adopt-a-Stream" program is one such effort, and more and more regulatory agencies are creating similar efforts.
"I don't think that we need to be afraid of our waters," he said. "We can enjoy them, but respect them for what they are."
One of the biggest challenges in monitoring programs, Carl said, is to determine what levels of bacteria in water represent normal levels and which ones represent unacceptable exposure.
"With sufficient time and money we could almost always arrive at a scientifically valid conclusion, but we generally do not have those resources," he said. "So we choose the methods that we are using to arrive at quick approximations of scientifically valid results."
Georgia, along with many other states, continues to use the 200-cfu standard for all fecal coliform, but even the U.S. Environmental Protection Agency has acknowledged that such a standard is not as reliable as other methods.
The EPA, Carl said, is encouraging states to switch to a different standard in which levels of E. coli bacteria -- a component of total fecal coliform -- would be used to identify non-conforming waters.
The EPA's recommendation is to use 235 cfu of E. coli as the standard. Because E. coli is barely 60 percent of total fecal coliform counts, it would translate to a standard of 392 cfu of total coliform, or almost twice the current standard.
"Using the current method, we generally do not get too excited about counts less than 1,000 cfu unless those counts are from an area of surface water that has no direct exposure to potential sources of contamination," Carl said.
For example, a reading of 700 in the middle of a large river indicates a substantial contamination source upstream, while a similar reading at a wastewater outfall would represent a well-treated outfall.
Improving water quality, he added, will require major institutional efforts, and also personal awareness by residents.
"If we repair our wastewater and stormwater infrastructure so that the two never meet until after the former is adequately treated, if we keep our septic systems functional, if we pick up after our pets and keep our other domesticated animals away from the streams, and if we clean up our road kill and appropriately dress our hunting kill, we can lower the fecal contamination in our water bodies," Carl said.