HomeMy WebLinkAboutStaff Report 5.A 01/28/2019 Attachment 20ATTACHMENT 20
Supplemental Health Risk Results Using Petaluma
Wind Data with AERMOD
November 30, 2018
Phyllis Fox, PhD, PE
and
Ray Kapahi, BSC, M. Eng.
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The health risk assessment described in our original report for the proposed Safeway fuel station
in Petaluma used the AERMOD dispersion model to determine the dispersion of toxic air
contaminants in the vicinity of the proposed gas station.
As noted in that report, AERMOD is the recommended dispersion model as it encapsulates the
most current dispersion algorithms and environmental parameters such as local wind, land use
parameters, and atmospheric stability. However, meteorological and land use data for Petaluma
were unavailable in a format consistent with AERMOD, and therefore our analysis relied on data
from Santa Rosa.
The report discussed the implications for using meteorological data from Santa Rosa and the
impact on predicted health risk in the vicinity of the proposed gas station. Specifically, the report
noted that winds in Petaluma were aligned more along the East-West direction and therefore,
the actual cancer risks would be higher than that predicted using data from Santa Rosa.
Following completion of our original report, we have obtained wind data from Petaluma that
was used by Safeway's consultant, and substituted that data in the AERMOD model for the
Santa Rosa data. The use of Petaluma wind data changes the risk profile in 3 ways:
1) The axis of the risk contours is shifted counter clockwise by about 45 degrees. This
means a larger proportion of emissions will be transported towards the daycare centers
and the school
2) The maximum residential risk increased by about 25%.
3) The number of residences affected with higher risk is increased. That is, the area within a
given risk contour is increased. A side -bye comparison of the 70 year cancer risk
using Santa Rosa vs Petaluma wind data is attached. Risks to children (9 -year exposure)
would also experience a higher risk.
Substituting 1990 to 1994 Petaluma wind data into 2013 to 2017 Santa Rosa AERMOD input
files is still not the ideal solution since we are relying on atmospheric stability data from
Santa Rosa. However, this approach captures the local wind patterns that are the primary
driver in transporting TACs to local homes, schools and businesses. As a result, it provides a
more refined risk analysis than use of wind data from Santa Rosa. As noted in our comments,
the use of Petaluma data would increase, not decrease, risks to the public.
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9Yr Cancer Risl< Petaluma Data
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