Draft Environmental Impact Report - California Off Highway Vehicle ...

3.7 Geology and Soils
Fault Zone maps provided by the CGS were consulted to determine the proximity of Clay Pit SVRA
to active earthquake faults, and Geotechnical Investigation, Clay Pit SVRA, Oroville, Butte County,
California (geotechnical investigation) (Geocon 2010; Appendix D of the General Plan) provided
the basis for analysis of geology and soils impacts.
General Plan Impact Analysis
IMPACT
3.7-1
Risk Related to Geologic Instability, Including Liquefaction, Subsidence, or Collapse
All regulatory requirements related to geologic stability and safety, such as those contained in the
CBC, would be adhered to when designing and constructing Clay Pit SVRA facilities. No major
excavation is anticipated for implementation of the General Plan. Minor excavation and trenching
for utilities or concrete foundations for structures within the SVRA would be required, but would
not be substantial or create geologic instability.
The site is approximately 1 mile from the Feather River and is underlain by the Laguna Formation,
a soil formation that generally consists of interbedded alluvial deposits comprising poorly graded
gravel with silt, clay, sand and cobbles, silty gravel, and clayey gravel. Consistency and relative
density of the Laguna Formation is generally stiff/dense to hard/very dense. Based on subsurface
conditions at the site, liquefaction is expected to be low during seismic events (Geocon 2010:2, 5;
Appendix D of the General Plan).
The Thermalito Afterbay ORV Project Inventory of Features (State Parks 1978) concluded that the
borrow pit presents no landslide danger to people or structures because the slopes are not very
high or steep, and the staff geologist noted no major landslide problems on the site.
Because all regulatory requirements related to geologic stability and safety would be adhered to,
construction activities would not induce geologic instability, and the site contains stable soils,
potential impacts related to geologic instability would be a less than significant.
Mitigation Measures: No mitigation is required.
IMPACT
3.7-2
Risks to People and Structures Caused by Strong Seismic Ground Shaking and Surface Fault
Rupture
The project site is not located within a known active fault trace or within an earthquake fault zone,
as delineated on the Alquist‐Priolo Earthquake Fault Zone maps. Therefore, the potential for
ground rupture resulting from on‐site active faulting is considered low (Geocon 2010; Appendix D
of the General Plan). In addition, the facilities proposed in the Clay Pit SVRA General Plan would be
Clay Pit State Vehicular Recreation Area
February 2012 3.7-6 Draft EIR