- water samples were taken in the canals before they were actually pumped into Lake Pontchartrain,
- After 48 hours in the water, all of the fish survived. Only one of the 12 invertebrate test samples had more than a 50 percent mortality rate when exposed to a solution of 39 percent flood water,
- more recent testing came back with better results
AMY WOLD and MIKE DUNNE, Advocate staff writers
More testing on the flood water being pumped out of New Orleans seems to confirm earlier tests showing that the water isn't as toxic as was once feared, according to the Louisiana Department of Environmental Quality.
On Tuesday, DEQ released results of recent biotoxicity tests done in the wake of hurricanes Katrina and Rita. These tests involve placing aquatic invertebrates and fish in floodwater samples being pumped from New Orleans. The water samples were taken in the canals before they were actually pumped into Lake Pontchartrain, Chris Piehler, a senior environmental scientist at DEQ, said.
After 48 hours in the water, all of the fish survived. Only one of the 12 invertebrate test samples had more than a 50 percent mortality rate when exposed to a solution of 39 percent flood water, Piehler said.
Two additional samples showed a 50 percent mortality rate with a water sample that was 100 percent flood water, he said.
However, more recent testing came back with better results. "The ones we found problems with previously have been retested and came back OK," Piehler said.
These tests are part of ongoing sampling of the water in Lake Pontchartrain, including parts of the north shore and the south shore, which is closer to where the pump water is being placed.
On Tuesday, DEQ also announced plans for future testing of Lake Pontchartrain waters and aquatic life.
DEQ and other agencies will sample fish from Lake Pontchartrain to make sure contamination in the water and sediment pumped from flooded sections of the city have not make aquatic life inedible, Piehler said.
It may be two to three weeks before those tests results come back.
So far, chemical contamination has not been a widespread problem, he said.
There are some toxic hot spots, such as near Murphy Oil in Meraux, where a tank spilled, coating about 1,000 homes with oil-contaminated water and sediments, Piehler said.
In some spots, including Claiborne Avenue and Audubon Boulevard in New Orleans, pesticides were found in the sediment samples. Many of the pesticides found, such as chlordane, Dieldrin and DDT, are banned.
Piehler said pesticides at those levels are not a concern unless someone ingests them "for long periods of time."
But he said it's notable that the pesticides were found even though they have been banned.
Water in the area continues to test high for coliform bacteria, which indicates the presence of sewage or animal fecal matter.
Residents returning home should use "good hygiene" when exposed to the mud and water left behind the hurricanes.
"Don't get it on you, and if you do, just wash off very carefully," Piehler said.
Those cleaning up need to take plenty of clean drinking water, he added. Much of the water available in the once-flooded areas is still unsafe to drink, he said.