United Stales Office of July .1990
Environmental Air Quality Planning EPA-450/4-90-014
v CT13A Protection Agency and Standards
DEVELOPMENT OF EXAMPLE PROCEDURES FOR
EVALUATING THE AIR IMPACTS OF SOIL EXCAVATION
cognation Program ASSOCIATED WITH SUPERFUND REMEDIAL ACTIONS
PURPOSE
The purpose of this project was to identify and define the computational requirements for estimating the air impacts
from the remediation of Superfund sites. Two example sites employing soil excavation were selected for investigation.
The estimation of air impacts from these sites depend on such factors as source type (point, area, or volume), location,
and movement of the sources.
GENERAL APPROACH FOR CONDUCTING AIR IMPACT ASSESSMENTS
Sit6 Characterization
The nature and extent of the contamination at the sites was defined. This included the identification of the
contaminants, their concentration, and their physical characteristics.
Selection of Remedial Alternative
Excavation was selected as an option to be examined. The excavation alternative included excavating the soil cap,
dumping the soil into a truck, excavating the highly contaminated soil zone, dumping it into a truck, transporting the
contaminated soil, and providing temporary storage of the soil prior to its ultimate disposal.
Estimation of Disposal Rates
Emission rates for each of the contaminants were estimated for the remedial activities. The emission calculations
for excavation were based on the use of the Research Triangle Institute's (RTI) Landtreatment equations modified to
accommodate the various activities associated with excavation. The ratio of each chemical to the total VOC emissions
was examined for each excavation activity, as well as its contribution to overall VOC emissions. These emission rates
served as an input to the dispersion modeling analysis for determining ambient concentration estimates.
Dispersion Modeling
The locations of remedial activities and their emission characteristics were input Mo the selected air dispersion
models to estimate both long-term and short-term ambient concentrations at numerous offstte receptor locations. The
SCREEN model was used to estimate 1-hour ambient contributions from individual sources. Long-term concentrations
were computed using the ISCLT model.
Risk Assessment
The dispersion model results for the site remediation activities were used to compute risks associated with the
alternatives selected. Both short-term and long-term ambient concentrations of VOCs were used in the evaluation of the
risks. Short-term values were used in evaluating acute effects, whereas the long-term values were used in evaluating
chronic effects. Both carcinogenic and noncarcinogentc effects were considered in the analysis. The purpose of this effort,
however, was not to produce a risk assessment at each site. Rather, it was to outline a set of procedures that could be
used, with existing tools, to assist in the evaluation of air pathway effects.
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201.2m
SI* Canter
SITE A
Site A is a 10-acre site on which the contaminated soil zone is
located near the center of the site. Soil in this area was contaminated by
leakage from drums stored above ground. The contaminated zone is an
area approximately 91 meters (300 ft) by 23 meters (75 ft), where the
contamination extended to approximately 2 meters (6.8 ft) below the
surface. This zone is considered homogeneous in soil type and contami-
nant concentration.
The initial remediation steps include removing all the stored drums
and stopping the addition of more contamination to the site. Aclay soil cap
approximately OS meters deep was placed on top of the contaminated soil
to minimize rainwater penetration and infiltration through the soil.
The remedial alternative selected for Site A was soil excavation.
The soil excavation would occur on an 8 hour/day, 6 day/week schedule. The average removal rate would be 885 cm3/
s (24-hour average) during the 2 month remediation period. Based on its characteristics, the soil was treated as being
in two distinct zones. The soil cap was treated as a relatively clean, tow-moisture, and moderately compact soil. The
contaminated soil was treated as a tow-moisture compact subsoil.
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H*iH Ro*i Length: 100.6m
SITE A CONFIGURATION
I
Conuunlnasd Zona 2
245m
ZOMI
SITE B
Site B is a 15-acre site with two separate contaminated zones.
Each zone has a distinct chemical composition, but each is considered
homogeneous within itself.
Zone 1 of Stte B encompasses an area of approximately 930 m2
(10,000 ft2) in which contamination reaches an average depth of 4.11 m
(13.5 ft). The contaminated soil volume totals approximately 3823 m3
(5,000 yd3).
Zone 2, the larger of the two zones, encompasses an area and
includes a volume of contaminated soil twice as large as those in Zone 1.
The approximate area is 1860 m* (20,000 ft2), and contamination reaches
an average depth of 4.11 m (13.5ft). The total contaminated soil volume
is approximately 7646m3 (10,000yd3). The contaminant level within Zone
2 is considered homogeneous.
The remediation alternative investigated for this site includes
excavation. The two contaminated zones will be removed sequentially,
not simultaneously starting with Zone 1. The total time for soil remediation is estimated to be approximately 6 months -
• 2 months for Zone 1 and 4 months for Zone 2. The excavation would call for excavation 8 hours/day, 6 days/week. The
average soil removal rate would be 885 crrrVs (24-hour average).
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2an*£ 01.4 mx 45.7m
SITE B CONFIGURATION
PROJECT OFFICER
James Durham
U.S. Environmental Protection Agency
MD-13
Research Triangle Park, North Carolina 27711
(919) 541-5672
WHERE CAN I OBTAIN COPIES OF
THIS REPORT?
Office of Air Quality Planning and Standards
Joseph Padgett
(919) 541-5589 (FTS 629-5589)
or
National Technical Information Service
5285 Port Royal Road
Springfield, Virginia 22161
(703) 487-4650
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