In the aftermath of Hurricane Irene, federal officials are actively sampling water from six East Coast rivers to check for E. coli, pesticides and other hazards that may have washed into waterways.

The U.S. Geological Survey announced Monday it has dispatched field crews to respond to the hurricane-turned-tropical storm, which, while less severe than predicted, still caused billions in damage in claimed at least 40 lives in 11 states, from North Carolina to Vermont. A key part of the USGS response is assessing water quality in the wake of widespread flooding.

The USGS Water Science Centers are collecting samples from the Charles River, Connecticut River, Delaware River, Hudson River, Raritan River, and the Susquehanna River, and testing them for nutrients, sediment, carbon, E. coli and pesticides.

“It is important for the USGS to monitor and document water quality after significant high-water events like Hurricane Irene. These events can cause changes in water quality that affect human health and the environment or affect commercial and recreational use of our Nation’s water resources,” said the agency in a statement.

Large storms, especially heavy rainfall, can flush nutrients, sewage, pesticides, and bacteria into rivers, and can result in higher concentrations of E.coli in surface water used for drinking.

“When looking at long-term water quality trends and year to year variation, this hurricane could be a defining event for 2011, and it’s important that USGS captures a complete picture of what happens this year,” said Charles Crawford, coordinator of the sampling effort at USGS.

Sampling results will be published on the USGS website here as they become available.