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

3.2 Air Quality
human populations, especially children, seniors, or sick persons would have continuous exposure
to a TAC. Sensitive receptors typically include schools, daycare centers, hospitals, retirement
homes, convalescence facilities, and residences.
During project construction, the use of off‐highway diesel equipment (e.g., for grading, excavation,
paving) and on‐road diesel equipment (to bring materials to and from the project site) would
generate diesel particulate matter (PM) emissions. CARB identified diesel PM as a TAC in 1998
(CARB 2011c).
Diesel PM emitted during construction activities typically collects in a single area for a short
period. Although construction of facilities envisioned in the General Plan, including the
headquarters facilities, would occur over two different construction periods, diesel‐powered
construction equipment would likely be used for no more than a few months in any one area
within the SVRA, and use would cease when construction was completed in that area. The dose to
which receptors are exposed is the primary factor used to determine a health risk. Dose is the
concentration of a substance or substances in the environment and the extent of a person’s
exposure to the substance. Dose is positively correlated with time, meaning that a longer exposure
period would result in a higher dose. The risks estimated for a Maximally Exposed Individual (i.e.,
an individual exposed to the maximum dose of diesel PM expected during project construction)
are higher if a fixed exposure occurs over a longer period of time. According to the California
Office of Environmental Health Hazard Assessment, health risk assessments, which determine the
exposure of sensitive receptors to toxic emissions, should be based on a 70‐year exposure period;
however, such assessments should be limited to the period/duration of activities associated with
the project. Thus, if the duration of proposed construction activities near any sensitive receptor
were 9 months, the exposure would be approximately 1% of the total exposure period used for
health risk calculation. Therefore, the probability that the Maximally Exposed Individual would
contract cancer from diesel PM generated by project construction would be less than 1 in 1
million. In addition, the diesel PM would not generate ground‐level concentrations of
noncarcinogenic TACs that exceed a Hazard Index greater than 1 for the Maximally Exposed
Individual. Generally, a potential cancer risk greater than 1 in 1 million and a noncarcinogenic
Hazard Index greater than 1 would be considered to represent potential impacts to human
health/welfare. Furthermore, with ongoing implementation of EPA and CARB requirements for
cleaner fuels, diesel engine retrofits, and new, low‐emission diesel engine types, the diesel PM
emissions of individual equipment would be reduced over the years through the life of the General
Plan. Therefore, impacts from TAC emissions during project construction would be less than
significant.
Odors
Butte County AQMD does not have rules that specifically address odors; however, Rule 200,
“Nuisances,” apply to odor emissions generated by a project in the region.
Clay Pit State Vehicular Recreation Area
February 2012 3.2-12 Draft EIR