FAHRENTHOLD &___________rr«i) 5io-933-484s; (Fax) 510.933-423*
ASSOCIATES, IWC."——————————————
2866 Mitchell Dr., Suite 230
Walnut Creek, CA 94688
MEMORANDUM
TO: Mr. Rich Smith 
^TE: 11/2/94
Law Office of John K. Dema
FROM: P. Fahrenthold
Fahrenthold & Associates, Inc
SUBJECT: Evaluation of Geraghty & Miller Remedial
Investigation Report
I received a copy of selected pages from the Geraghty &
Miller Report identified above. I have review the report for
technical validity of the observations presented therein.
I placed particular emphasis on Section 5.0, addressing
comments on Pages 5-18 and 5-19. The results of oiy review
are provided in the following discussion.
General Comments
This Section of the report is devoted to the **Nature
and Extent of Contamination". In reality, it attempts to
explain the transport of contaminants from the sources
identified in Section 5.L and known to exist, to the
groundwater and soils in the area.
It is my opinion, supported by the calculations
provided in this memo, that the document is seriously flawed
in its presentation and has no technical foundation for the
statements made. The portions of the document with which I
find flawed are identified below.
Paragraph 1, last 7 lines: "......One exception noted for
this indication of contaminant release is the detection of
low levels (less than 10 ppb) of chlorinated VOCs in soil.
Due to the presence of chlorinated VOCs in groundwater
throughout most of the site, these low concentrations are
attributed to volatilization and adsorption from the
contaminated groundwater. This has been shown to occur in
areas that are not suspected source areas (as discussed
below), so low values of chlorinated VOCs (less than 10 ppb)
in soil are not indicative of a release near the sampling
source."
TUT OO6 0641
*64637*
64637
This paragraph is apparently written to remove from
consideration all soil samples which contain less than 10
ppb of a Voc .
The above statement is supplemented by the first
sentence of the second paragraph. It states that u....If
impacted soils are identified and a corresponding
groundwater impact originates in the same area, then a
source of groundwater contamination has been identified."
This statement appears to be rather obvious and
potentially contradictory to the previous statement that
soil contamination less than 10 ug/kg does not indicate a
source of contamination.
Both of these statements are necessary to set up the
interpretative comments on Page 5-18. The discussion on
that page, using the foundation previously laid which would
prove that VOCs can only originate from soils to groundwater
if the soils contain greater than 10 ppb of VOCs, is the
grounds for stating that low level soil contamination due to
VOCs north of the oil/water separator originated from
contaminated groundwater.
The problem with all of this is that it's wrong, full
of half truths, etc. The real story is far more complicated
but easily demonstrated. The remainder of this nemo is a
scientific explanation of what the data in the report and
simple engineering calculations say and how they should have
been combined for interpretation of the data in the report.
Background
First some background. Like most technical discussions
there is an element of truth in many of the statements made
in the G & M document. They are not the entire truth,
however. The real situation is like this: all VOCs near
the ESSO Tutu station exist in three phases, oil, water and
gaseous. There are two constants which describe the
mathematical relationships among the contaminant
concentrations in all of the phases: Henry's Law constant
and the octanol-water partition coefficient. The
relationship between the VOCs in oil and VOCs in air is
The implication of this statement ie not clear in the portion of the
text I have reviewed. The authors of the document are eliminating from
consideration as a potential source any areas which contain lees than 1O
ug/kg of PCE in soil. The text of this memo will ahow that to be an
invalid criterion for selection of potential contaminant sources.
A
SOCIATES. INC.'
TUT OO6 0642
given by Raoult's Law, using vapor pressure of the compound
to calculate the vapor composition of the VOC above the oil
phase.
Henry's Law constant describes the relationship between
the concentration of VOCs in water and their concentration
in air (vapor). The octanol-water partition coefficient
provides the relationship between VOCs in oil and water.
As a result of the property of VOCs to distribute
themselves between water and the air space above the water
(vadose zone), and between an oil phase and a water phase,
we have the situation where VOCs dissolved in oil in an
oil/water separator will be simultaneously dissolved in the
water in the separator. If that water leaks into the soil
it will contaminate the soil, allow the VOCs to volatilize
into the vadose zone and also percolate to the ground water
and contaminate the groundwater.
Similarly, if groundwater is contaminated with VOCs,
from whatever source, the soil vapor above the groundwater
will contain some level of VOC contamination. If there is
an oil phase around the area, some of the VOCs will also be
transported to the oil phase and dissolve in it.
The extent to which any of this occurs depends on the
concentration of VOCs in any of the media. The following
tables should help calibrate your thinking on the matter.
First, lets look at the relationship between VOCs in
oil and VOCs in water. The tables below provide the basic
data. The term KO/W represents the logarithm of the ratio
of concentrations of a VOC in oil to that "in water.
Table 1. Log K0/w for VOCs
Compound 
Log KO/W
TCE 
2.29
TCA 
2.17
1,2-DCE 
1.48
PCE 
2.88
Using the values for K0/w and making calculations, we
can produce the following table containing the correct
relationships.
H K B M T M O I _ n A
ES. IMC.
TUT OO6 O643
TCE
2.06
1.03
0.515
0.0515
0.00515
TCA
2.72
1.36
0.68
0.068
0.0068
1,2-DCE
13.24
6.62
3.31
0.331
0.0331
PCE
0.527
0.263
0. 132
0.0132
0.0013
Table 2. Concentration of VOCs in Water and oil
Cone, of voc in water, ppro
Cone, of voc in Oil
400 ppm
200
1GO
10
1
The way to read the table is as follows: for PCE
(perchloroethylene or tetrachloroethylene) when the
concentration of PCE in oil is 400 ppm the concentration in
water is 527 ppb. For comparison purposes you will note
that 1,2-DCE (l,2-dichloroethylene) is distributed much
greater to the water than is PCE. This result is due to its
much greater volatility than PCE.
I did not calculate values higher than 400 ppm for any
of the compounds in oil. You can do it by ratio of the
values in the table.
Similarly, we can look at the relationship between the
VOCs in water and the vapor space above groundwater (the
vadose zone). The following table provides the basic data,
calculated using a Henry's Law constant of 567 atm/mole
fraction at 25°C (the EPA published value).
Table 3. Vapor Concentrations of PCE Above Water
ppb PCE 
ppb PCE in
in Water 
Vadose Zone Air
1 
134
2 
269
4 
538
3 
1077
12 
1615
30 
4039
50 
6732
100 
13,465
300 
40,397
The table shows that for a groundwater concentration of
300 ppb in water there will be a vapor concentration of PCE
of 40.4 ppm(v) in equilibrium with it.
Similarly, the values for the vapor concentrations for
VOCs in the vapor phase above oil with the VOCs dissolved in
it are provided in the following table.
'AHRCNTHOI-O A
ASSOCIATES, INC.
TUT O06 0644
Table 4. PCE and DCE Concentrations in Air Above Oil
1,2-DCE, 
PCE,
Oil Cone, ppm 
Cone, ppm 
Cone, ppm
10 
22.63 
0.669
30 
67.89 
2.00
50 
113.15 
3.34
100 
226.3 
6.69
300 
6778.9 
20.07
700 
1584 
46.87
You will see from the table that the concentration of
1,2-DCE is very much larger than that of PCE due to its
greater volatility.
Interpretation of the Data
Based on the information provided above we can
interpret the data in the vicinity of the Four winds Center
and the Esso Tutu station to determine if there is a source
or sources in the area.
Lets start with groundwater. The ground-water
concentration of PCE in MW-8 is approximately 40 ppb,
indicating that if its source was the water in the north
oil/water separator, the oil in the separator would have
contained about 40 ppm (40,000 ppb) of PCE. If you have
concentration values for the other VOCs in the oil phase of
the separator (particularly 1,2-DCE which is found in rather
high concentration in MW-8), you can make the appropriate
comparisons with the groundwater data in the Geraghty &
Miller tables.
At the low end of the concentration range we can easily
determine that the concentration in the soil will be
approximately 3 to 42 ug/kg if the concentration of PCE in
the water from the separator is between 13.2 and 263 ppb
(corresponds to 10 and 200 ppm PCE in the oil phase in the
separator). This calculation assumes that we take 1
kilogram of soil which is saturated with water from the
separator (20% of the soil volume) as the basis of the
calculation .
It is clear from the monitoring data that there is a
potential relationship between the measured concentration of
PCE in groundwater at MW-8 and the possible concentation of
This calculation is based on a material balance which considers the
only source of concaminati.cn. to be the contaminated water in the poraa
of 1 kilogram of soil of 20% porosity.
PAHMBM THOI-D A
ASSOCIATES. INC."
TUT 
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O645
PCE in the oil phase of the separator which would have been
in equilibrium with the water leaJced from it. To further
elaborate on this statement; if the oil in the separator
contained 400 ppm of PCE the water would have contained 527
ppb (see Table 2). This separator water could have been
diluted by water migrating to the Four Winds wells from the
east and west to provide the dilution to about 40 ppb as
observed in the groundwater at MW-8. [This analysis relies,
in part, on my recollections that the groundwater under the
Esso station migrated to the Four Winds wells during
pumping.J
Similarly, if the oil in the separator contained low
concentrations of PCE (less than 10 ppm, for example), it
would be reasonable to expect that concentrations in soil
around the area where water leaJced from the separator could
have migrated, could contain concentrations of PCE in the 10
ug/kg range. This is clear from the data in Table 2.
In conclusion, the monitoring data and the calculations
strongly suggest that the north oil/water separator at the
Esso Tutu was a potential direct source of PCE to
groundwater in the area through the distribution of PCE
between the aqueous and oil phases present in the device and
migration of the aqueous phase directly to groundwater.
Further, the soil analysis data indicate that there could
have been saturation of soils with water from the separator,
diluted or undiluted, which produced concentrations of 10
ug/kg PCE in the soils in the area.
The above analysis relied upon the migration of water
containing PCE from the separator into the^pore spaces of
the soil in the area. The other possibility for
distribution of contamination is volatilization of PCE from
groundwater or the oil phase from the separator into the
pores of the soil and resulting detection and quantification
in soil analyses.
The following table provides all of the relevant
information to evaluate transport from either oil or water
to the vadose zone and the resulting concentration of PCE in
a soil sample.
FAHMEHTHOt-D A
ABttOCIATMt*. INC."
TUT 
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0646
Tai>le 5. Concentrations of PCE in Soil Derived from
Volatilization from Oil or Water
PCE in Water 
PCE in oil 
PCE in Air 
PCE in Soil
in ppb 
in ppm 
in ppm 
in ug/kg
0.496 
1 
0.0669 
0.0707
14.9 
30 
2.00 2.12
24.84 
50 
3.34 3.53
49.68 
100 
6.69 7,07
198.73 
400 
26.78 
28.28
347.7 
700 
46.78 
49.49
As can be seen from the table, values of 10 ug/kg in
soil could be observed as the result of vapor phase
migration of PCE from oil, at approximately 250 ppa PCE
concentration, or of PCE from water at approximately 150 ppb
PCE concentration.
Conclusions
The major flaw in the Report is its reliance on
qualitative information to reach quantitative conclusions.
Unfortunately, logic and reason alone are not adequate to
assess the extent to which transport pathways are available
and have been operating in an environment. This erroneous
approach renders any interpretative comments contained in
the report subjeer to serious question.
First, the values provided in the table above as well
as in tables previously presented in the text indicate that
values of PCE in the range identified by Geraghty and Miller
of 3.1 to 3,200 ug/kg could be derived from the various
products in the north separator at the Ess'o Tutu station
(Geraghty and Miller, Page 5-18).
It follows from the calculations and discussions
provided in this memo that the 10 ug/kg value is without any
scientific and engineering foundation as a criterion for
selection of sources of contamination and is invalid for
elimination of the north oil/water separator as a source.
There is another instance of a conclusion without a
scientific basis in the document which is worth noting.
The values in this Table are also baaed on a material balance assuming
the porosity of the soil is 20% and that the pores are filled with air
at the VOC concentrations indicated. The mass of VOC in the air ie
considered to be quantified in the analysis of the soil sample.
FAHHBNTMO1.D A
ASSOCIATES. INC.*
TUT 
O06 
0647
The statement "....This is confirmed by soil samples
collected by BB&L (see Figure 5-10). The deepest soil
sample collected by BB&L, SS-1 from 9.0 feet bis, had no
detections of chlorinated vocs." is made on Page 5-18 of the
document supporting the hypothesis that there is limited
migration of VOCs from the north oil/water separator.
This statement alone is inadequate to support the
hypothesis proposed. There are numerous factors, primarily
the geologic conditions and sampling technique which could
have impacted the detection of chlorinated VOCs in the
sample. A responsible technical presentation would describe
the validity of the sample, its geologic tentativeness, and
sampling and analytical representativeness prior to making
such a sweeping conclusion.
PAHRPMTHOL.D 4_
ASSOCIATE*. IHC.
TUT
OO6 
O648