What are the risks of earthquake, landslide, or floods?
Tuolumne County has not experienced a significant earthquake in recorded history although a couple of minor faults run through the west county area. We occasionally feel the tremors of earthquakes from the San Francisco Bay Area or the Mammoth area of the Eastern Sierra. Groveland area soils and substrate are “solid” with lots of rock. Except on extremely steep slopes, the soil stability is generally excellent and no special foundations are needed. Flooding is a possibility as we discovered during the “100 year floods” of 1997 that also washed out major campgrounds in the Yosemite Valley. Structures and roadways that were affected were only those built very close to major rivers and streams, such as the Tuolumne River and its Middle and South Forks. Houses that front the lake must be built 50 feet back from the dam spillway elevation of 2550 feet. Properties below the dam on Big Creek have a slight chance of flooding if the dam is destroyed. The dam is 110 feet high, 385 feet long, and
