The Cascades and Modoc Study Unit was sampled between 7/12/2010 and 10/14/2010; 90 wells were sampled.
The study unit consists of 6 study areas:
• Shasta Valley and Volcanic Area
• Honey Lake Valley
• Quaternary Volcanic Areas
• Tertiary Volcanic Areas
• Modoc-Cascades Low Use Basins
• Sacramento Valley Eastside
The study unit is within the Siskiyou, Modoc, Shasta, Lassen, Tehama, Plumas, and Butte counties.