As intense heat settles over Richmond for the summer, the murky, green waters of the James River look increasingly enticing.

Whether it's wise to swim in them, however, depends upon whom you ask. Some swear by refreshing dips off the shores of Belle Isle. Others tell stories of miserable rashes and other ailments brought on by river swims.

"It's one of the most common questions we get — whether it's safe to swim in the river," says Jamie Brunkow, the James River Association's keeper for the lower James. "Bacteria is certainly one of the concerns."

With a new program, James River Watch, the association hopes to provide answers. And, news flash: Pet and human feces are valid concerns.

Every Thursday, volunteers collect water samples at four popular swimming spots in the city. By Friday, they've posted the results at James River Watch, so weekend swimmers can enter the water with a better idea of exactly how many disease-causing bacteria they'll be up against.

The association committed to weekly testing last year, but the pattern is fairly predictable, Brunkow says. Bacteria counts rise after heavy rains and drop back to safe levels about 48 hours later.

That's in part because rain sweeps waste and other contaminants into the river. And because, in the city, about a quarter of an inch of rain is enough to overwhelm the city's combined storm-water and sewage system, which triggers an overflow.

In short, that means the city begins dumping untreated sewage and storm water directly into the river.

Recent results reflect the trend. E. coli bacteria counts at Rockett's Landing soared to more than 10,000 colonies per milliliter June 12. The Environmental Protection Agency sets a threshold of 235 for safe swimming. By the end of last week, following a dry spell, levels had dropped to 67.

Gordon Kellett and Michael Gillert, the volunteers who collected the samples that yielded those results, say that while the outcome predictably is tied to rainfall, they hope the data helps people understand the phenomenon.

While they're leaving the pipeline, one of the testing areas, with the long pole they use to collect water samples from the shore, a woman asks if they caught anything.

They explain that they're doing water-quality testing — not fishing.

"Oh, I hope it's not poisonous," the woman says.

On Friday, they had a definitive answer. Nope.