Photographs used in the module were generated within EPA except where individual donations are credited. EPA wishes to thank the following entities for donating photographs for use in the module:
A | Brian Strohecker, Invitrogen Corporation |
B | George D. Di Giovanni, Texas Agricultural Experiment Station - El Paso, Texas A&M University |
For questions, contact EPA, Office of Ground Water and Drinking Water, Technical Support Center at miller.carrie@epa.gov.
This completes the module.

You need the latest free Flash Player Plugin to view this page.