2007-11-20_REVISION - M1982015 ‎(12)‎

• Permit No: M1982015
• IBM Index Class Name: REVISION
• Doc Date: 11/20/2007
• Doc Name: Integrated Corrective Action Plan
• From: E-21 Engineering, Inc.
• To: DRMS
• Type & Sequence: TR3
• Media Type: D
• Archive: No

' - A list and map defining all source areas, areas of contamination or
contaminant discharge areas. These areas need to be defined to indicate
' the proximity of contaminants with respect to receptors and sampling
efforts.
n

Table IV B6 - Source Area Evaluation
Source Area Immediate Receptors Nearby Receptors
SHT contains very high BTEX Wain River levee is <10 ft
St
levels; .
to the south;
Slurry Holding Trench Soils and groundwater
Quarry pond is -75 ft to the
beneath the SHT have been north.
impacted.
Limited subsurface soil
impacts are present beyond St. Wain River is -100 ft to
the SHT and incomplete slurry the south;
Subsurface Soil wall;
Groundwater is impacted by ft to the
Quarry pond is - 100
gasoline in the area of the .
northwest.
spill.
St. Wain River is -100 ft to
Groundwater is impacted by the south;
Groundwater gasoline in the area of the Quarry pond is --100 ft to the
spill. northwest.
Surface Water The St. Wain River is not a
Not applicable
(St. Vrain River)
source area.
Surface Water The quarry ponds are not
Not applicable
(Quarry Ponds) considered a source area.
See Figure 4 for source area locations.
' - A discussion of contaminant mobilities, including estimates of
contaminants to be transported by wind, volatilization, or dissolution in
' water. For those contaminants that are determined to be mobile and have
the potential to migrate and contaminate the underlying groundwater
resources, the applicant should also evaluate the leachability and mobility
of the contaminants. This evaluation should consider, but not be limited to
' the following: leachability/mobility of the contamination; health-based
groundwater standards for the contamination; geological characteristics of
the vadose zone that would enhance or restrict contaminant migration to
1 groundwater, including but not limited to grain size, fractures and carbon
content; and depth to groundwater. This evaluation, and any supporting
documentation, should be included in the plan submitted.
Contaminant Mobility Throuqh Soils in Contact with the Slurry Holdinq Trench
The chief contaminant is gasoline. The contaminants of concern are benzene,
' toluene, ethyl benzene and total xylenes. The gasoline in the SHT is suspended
in a mixture of mostly bentonite and some silt and sand. The bentonite slurry is
relatively immobile and will not leach to a significant extent even into sandy and
' gravelly deposits. It is designed to be an aquitard with a very low permeability (1
X 10-7 to 10"9). The SHT is located in the clayey surficial soils along the bank of
the quarry ponds with a fairly high permeability as well. Although benzene has a
' relatively high mobility rate, it is being contained by the slurry and clay of the
17