Soil ContaminationOverview and Case
Study
Christopher Lyles
ESS 315
How soil becomes
Contaminated
 Urban runoff
 Agricultural
runoff
 Mining
 Industrial
Operations
 Atmospheric
Deposition
 Contaminated
Groundwater
Sources of
Contamination
Gas Works Park
Gas Works Park
Previous site of coal and oil gasification (1900 to 1956)
Waste accmulations include: coal, tar, and oil
Polynuclear aromatic hydrocarbons (PAH’s )and
volatile organic compounds (VOC’s) are present in
groundwater
PCB’s, heavy metals, and cyanides also present
“Gas Works deposit” is as thick as 9 feet across the
park and overlies the Vashon Till- consists of waste
products from prior operations (
Developed by Seattle Parks and Recreation and
subsequently studies by USGS and UW
Borehole and Well
Sites- Contour Map
Water Table Contour
Map and Flow Paths
Geologic Cross
Sections
 Important to understand the “Gas
Works Deposit” as It’s interaction
with the Ground Water is the main
concern
Contamination
processes



Weathering of
Hydrocarbons in soil and
NAPL’s
Weathering- dissoultion,
volatilization,
biodegradation
These processes release
water-soluble, low
molecular weight
orgainc compunds into
water, leaving behind
stained soils containing
insoluble, high molecular
weight compounds
Not Quite Polluted
Enough…
…to become a superfund site (in 1980)
But polluted enough to cost tens of millions of
dollars to clean up…
Puget Sound Energy and City of Seattle still
continuing to monitor and clean the site
Main Concerns/
Remediation Techniques
 Benzene (toxic/
Carcinogenic)
 Naphthalene
(Toxic/ noncarcinogenic)
 PAHs (vary
depending on type
but can be both
Toxic and
Carcinogenic)
 Air sparging/ Soil
Vapor Extraction
(AS/SVE)
 Monitored Natural
Attenuation
(possible phytoremediation to be
used in future)
 Direct Soil
contact Remedy
Air Sparging
Air Sparging/ Soil
Vapor Extraction
(AS/SVE)
Phytoremediation
References
http://www.ecy.wa.gov/programs/tcp/sites/gaswkspk/Gas
%20Works%20Agreed%20Order%20DE%202008.pdf
http://www.seattlepi.com/local/331605_gasworks14.html
https://info.ngwa.org/GWOL/pdf/901878014.PDF
http://www.ecy.wa.gov/pubs/0709080.pdf
http://www.epa.gov/superfund/about.htm
http://www.ecy.wa.gov/programs/TCP/sites/gaswkspk/gas
wks.htm
http://www.ecy.wa.gov/programs/tcp/sites/gaswkspk/Five
%20Year%20Review.pdf