The Sierran Regional Study Unit was sampled between 6/23/2008 and 10/22/2008; 84 wells were sampled.
• The study unit consists of 1 study area encompassing the entire Sierra Nevada (note: the Tahoe/Martis, Central Sierra, and Southern Sierra Study Units are included in the area of the Sierran Regional Study Unit).Portions of 23 of the 58 counties in the State of California are within the study unit (county boundaries indicated by dashed lines)