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

3.7 Geology and Soils
liquefiable soil can be found on the valley floor, especially near the Sacramento and Feather Rivers
and minor tributaries, including tributaries that are no longer active (Butte County 2010a: 4.6‐10).
The site is approximately one 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; Appendix D of the General Plan).
Landslides
The topography of the area surrounding the project site is generally level, as is the natural terrace
surrounding the excavated basin. The basin is approximately 30–40 feet below the surrounding
grade, and is surrounded by gently inclined slopes. In the Thermalito Afterbay ORV Project
Inventory of Features the staff geologist concluded that the borrow pit slopes are not very high or
steep and noted no major landslide problems on the site (State Parks 1978:19).
3.7.2 Regulatory Setting
This section describes additional planning and regulatory information related to geology and soils
to supplement information provided in Section 2.7, “Planning Influences,” of the Clay Pit SVRA
General Plan. In particular, Section 2.7.1, “Systemwide Planning,” includes a summary of the 2008
Soil Conservation Standard and Guidelines ) (State Parks 2008). Other state and regional plans,
policies, regulations, and laws related to geology and soils are summarized below.
Federal Plans, Policies, Regulations, and Laws
No federal plans, policies, regulations, or laws related to geology and soils are applicable to Clay
Pit SVRA. However, while not a regulatory agency, the U.S. Natural Resources Conservation Service
(NRCS) provides science‐based soil information in the National Cooperative Soil Survey, a
cooperative effort of federal and state agencies, universities, and professional societies. The NRCS
is a division of the U.S. Department of Agriculture.
State Plans, Policies, Regulations, and Laws
Alquist­Priolo Earthquake Fault Zoning Act
The Alquist‐Priolo Earthquake Fault Zoning Act (Alquist‐Priolo Act) was passed by the California
Legislature in 1972 to minimize the hazard of surface faulting to structures. The Alquist‐Priolo
Act’s main purpose is to prevent the construction of buildings used for human occupancy on the
surface trace of active faults. The act addresses only the hazard of surface fault rupture and is not
directed toward other earthquake hazards. According to the act, local agencies must regulate most
development in fault zones established by the State Geologist. Before a project can be permitted in
Clay Pit State Vehicular Recreation Area
February 2012 3.7-2 Draft EIR