The waters are receding in Colorado after rains caused immense flooding last week. More than 12,000 people were evacuated, and hundreds are still stranded or missing.

As the water level comes down, people are getting a better view of the damage. However it's not only to homes: but to oil and gas wells, too

Now there is a concern by some that flood waters mixed with the chemicals used at fracking sites may have created a hazardous soup that's contaminating the landscape.

To explain is Mark Jaffe, energy reporter for the Denver Post.