[rayiner]

Foul. Just foul.

> But when it rains hard—a quarter of an inch in an hour might do the trick—some four hundred sewer pipes around the city begin flushing untreated waste, using the rivers as municipal lavatories.

> For the statistically inclined, the figure to watch is the number of colony-forming units (of bacteria) per hundred millilitres. Beach advisories are often set at thirty-five.

> The skies opened. Grzybowski sampled again, and the C.F.U. count in the river exceeded 24,196, the highest possible measurement. “Pretty much raw sewage,” he reported. The would-be swimmer felt a wave of compassion for the seahorses. ♦

[ganeumann]

This is true of many riverfront municipalities. 771 cities in the US have combined sewer overflows [1]. My partner monitors the pollution level in the Hudson across from NYC (in Hoboken) and when it hasn't rained in a few days the water is clean enough to swim. But after a heavy rain, it is, indeed, foul.

That said, the Hudson is ridiculously cleaner than it was 20 years ago. So much so that the Marine Borer (a type of worm that eats wood) has made its return and is destroying the old piles that hold up parts of the landfill on the waterfront. Unintended consequences, but worth it.

[1] List here: http://water.epa.gov/polwaste/npdes/cso/

[js2]

Most of the time the water is safe for swimming.

http://www.nycswim.org/About/FAQ.aspx#1