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2.5 Program Implementation
2.5.1 Sampling Schedule
Ground-water sampling for the detection program is
scheduled in two phases:
- initial background sampling for a period of one year
for:
0 measurement of the ground-water surface elevation
for each sampling event;
0 parameters characterizing the suitability of the
ground water as a drinking water supply;
0 parameters establishing ground-water quality; and
0 parameters used as indicators of ground-water
contamination (four replicates for each upgradient
well).
- sampling after the first year for:
0 measurement of the ground-water surface elevation
each time a sample is obtained;
0 parameters establishing ground-water quality;
0 parameters used as indicators of ground water
contamination (four replicates for each upgradient
and downgradient well).
Initial background sampling should be performed during
the period of November 19, 1981 through November 18, 1982
for interim status facilities. The overall schedule for the
detection program is summarized in Figure 2-15. Detection
program sampling after the first year should continue until
final closure of the facility (and for disposal facilities
until the end of the post-closure care period) or until a
ground-water quality assessment program is begun (see
Section 3).
There are certain situations in which it would be
advisable to sample more frequently than the required minimum
or to amend the sampling schedule in order to detect significant
effects upon the ground-water quality. Such situations
include:
69
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Figure 2-15
Minimum Sampling Frequency Required
for the Detection Program
First Year
Month
8
10 11 12
test
parameter
drinking
water
suitability X
groundwater
quality X
contamination
indicators X
groundwater
surface
elevation X
X
X
X
X
After the
X
X
X
X
First Year
X
X
X
X
Month
test
parameter
8
10 11 12
groundwater
quality X
contamination
indicators X
groundwater
surface
elevation X
70
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high ground-water flow rate situations. The ground-
water flow rate is a major factor influencing the
rate at which contaminants may migrate in the subsurface
environment. The higher the ground-water flow rate
the more frequently sampling is recommended (e.g.,
turbulent flow in fractures or solution cavities).
Flow rates in different types of aquifers can range
from a few meters per year to tens of meters per day.
(See Section 3.2 for information on measurement of
ground-water flow rate and evaluation of subsurface
factors influencing flow rates);
changes in ground-water flow direction. Changes in
flow direction can affect the ability of "upgradient"
and "downgradient" wells to adequately determine the
facility's effect on ground-water quality in the
uppermost aquifer. If such changes in flow direction
occur, then the monitoring system must be re-evaluated
and, if necessary, redesigned such that it meets the
monitoring performance standard in §265.90(a);
significant climatic changes. Characteristics of the
climate (e.g., precipitation or evapotranspiration)
will influence leachate generation, which would be
expected to accelerate during ground-water recharge
periods. Ground-water monitoring can be most effective
if it responds to these recharge periods. Due to
this consideration, the sampling schedule might be
altered with respect to frequency (e.g., instituting
monthly sampling as opposed to semi-annual) and/or
periodicity (e.g., sampling once in March, April, May
and June, then in October in addition to regular
frequency sampling). A situation in which more frequent
sampling should be considered is after an extended
period of above average precipitation during which
leachate generation would be expected to accelerate
or to become more dilute;
gradual changes in monitoring data. A noticeable
trend (as opposed to a statistically "significant
change") in monitoring results may warrant more frequent
sampling in order to keep abreast of the apparently
changing condition of the ground water;
waste type influences. Waste that is highly soluble
in water and/or mobile in soil may travel quickly in
the subsurface environment. A facility owner or
operator managing such waste should consider sampling
more frequently than the minimum; and
71
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- an "unusual" event at the facility (e.g., improper dumping
of a large amount of liquids or a visible spill or discharge
may indicate the need for more frequent monitoring).
2.5.2 Statistical Analysis
The owner or operator of a facility must perform a statistical
analysis of the concentrations or values of the indicator parameters,
as determined from the sampling and analysis of the required
monitoring wells. If the analytical results for Total Organic
Carbon and TOX are reported by the laboratory as below detection
limits, then the owner or operator should use values of one
milligram per liter for Total Organic Carbon and five micrograms
per liter for TOX in the statistical analysis.
Section 265.92(c)(2) on sampling and analysis requires that
the initial background mean and variance for each indicator
parameter be determined by pooling the replicate measurements
for the respective parameter concentrations in samples obtained
from the upgradient well(s) during the first year. Replicate
analyses are not required for downgradient wells during the
first year.
After the first year of monitoring, §265.92(d)(2) on sampling
and analysis and §265.93(b) on preparation, evaluation, and
response require the owner or operator to analyze for and calculate
the mean and variance of each indicator parameter (i.e., pH,
Specific Conductance, Total Organic Carbon, and Total Organic
Halogen), .based on at least four replicate measurements on eacjj
sample, for each well in the monitoring system. Results for"
each indicator parameter from each sampling event (for each and
every well in the monitoring system) must be compared with the
initial background mean (i.e., that established for the upgradient
well(s) during the first year). The student's t-test at the
0.01 level of significance must be used to determine statistically
significant increases (or decreases also, in the case of pH)
over the initial background values.
First Year Statistical Analysis
During the first year, the initial background mean and
variance for each indicator parameter must be determined for
samples from upgradient wells.
Arithmetic Mean
In order to perform the t-test, the raw data from the background
and monitoring wells must be reduced to specific summary measures.
These measures are the mean (an average) and the variance (a
measure_ of variability of the data). For any set of data the
mean (X) is equal to the sum of the measurements divided by
the number of measurements (n).
72
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The indicator parameter values for all four quarters of the
first year are used to calculate the mean. If more than one
upgradient veil is being used, the owner or operator must
calculate the overall mean value (of each indicator parameter)
for all of the upgradient wells. This can be accomplished
by summing the data from all of the upgradient wells and
dividing this sum by the total number of measurements for
each parameter. These first-year upgradient mean values are
important since they establish the initial background
concentrations to which all subsequent upgradient and
downgradient concentrations or values will be compared.
Variance
The variance is an average of the squares of the
differences between the actual value and the mean, and is a
measure of variability. The mean and variance are used in
the Student's t-test to determine whether any changes in the
concentration of the indicator parameters are statistically
significant. In this context, the variance may be defined
as: the sum of the squares of the differences of the individual
measurements and the mean, divided by one less than the number
of measurements. Symbolically, the sample variance is
calculated as follows:
where
n
s^ =
Tl
s
i = 1 (
Xj_ - X)2
n - 1
= sample variance;
= value of each measurement;
= mean of the measurements;
= "the sum of" a set of numbers from the
first value (where i = 1 ) to the last value
(where i = n). In this case, the squared
differences of the measurements and the
mean are added; and
= the number of measurements.
For example, in determining the sample variance of the
background value of the pH of an upgradient well for the
first year, the owner or operator would proceed in the following
manner:
- Substract the mean pH value (e.g., 6.4) from each pH
measurement, square this value, and sum the squared
differences as follows:
73
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Measurement
Mean
Difference
Squared
Difference
1st Quarter
2nd Quarter
3rd Quarter
4th Quarter
5.7
6.3
6.8
4.8
7.5
8.2
6.9
6.1
5.7
4.3
5.5
6.2
4.7
8.6
8.9
6.0
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
6.4
-0
•0
0.4
1.6
1.1
1.8
0.5
0.3
.07
2.1
0.9
0.2
1.7
2.2
2.5
0.4
0.49
0.01
0.16
2.56
1.21
3.24
0.24
0.09
0.49
4.41
0.81
0.04
2.89
4.84
6.25
0.16
Total
27.90;
- Divide the sura of the squared differences by the number
of measurements minus one, as follows:
Sample Variance = s2 = 27.9 = 27.9 = 1.86; and
n-1 16-1
- Keep at least two decimal places for accuracy in
calculations.
The variance for specific conductance, total organic
carbon, and total organic halogen can be calculated in a
similar manner. If more than one upgradient well is being
used, the sample variance can be calculated by pooling all
the measurements (for each indicator parameter) to determine
the mean, subtracting the mean from each measurement, squaring
and summing the differences as in the first step above, and
dividing this sum by the number of measurements minus one,
as in the second step above.
Subsequent Statistical Analysis (after the first year)
After determi. nj.ng initial background val_ues during the
first~~year7the~bwner or operator must, at least semi-anjTua_lly_j___
c a 1 c u rate~~~ttre~"s mSpTeTlife a n and sample variance" for four replicate
74
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measures (necessitating four al_.Lquots f rom_Jt]ie__ same sample for any _
destructive analyses) of pH, specific conductance, total
organic carbon, and total organic halqge_n_,___for each upgradient
and_ dpjwngr~a'c[ient g r o u hcf-wa t e r monitoring well. (The regulations
alj.ow for __a_.jg£.eater sampling and analysts^requency than the
minimum, hence providing an opportunity to Tesse'n" "€'he p~fospecV
~6T~fal.se positive indications of facilityr"impact~on ground" water.)
"rlTese" values should be determined in the manner described
previously. The mean of each of these indicator parameters
for each upgradient and downgradient well must be individually
compared to the initial background mean for each indicator
parameter by using the Student's t-test at the 0.01 level of
significance. This provides a determination of statistically
significant increases (or decreases also for pH) over the
initial background level.
Student's t-test
[Note: The methodology for application of the Student's t-test
presented in this guidance document differs from that offered
in the May 2, 1980, background document for ground-water
monitoring. Although both methods could be appropriate, the
one recommended in this guidance document is preferred.]
The Student's t-test is a statistical method used to
determine the significance of a change between initial
background and subsequent parameter values and must be
calculated at least semi-annually for each well for each
indicator parameter. Using all the available background data
(n^, readings), calculate the background mean (X^) and background
variance (s^). For the single monitoring well under investigation
b
(nm readings), calculate the monitoring mean (X^) and monitoring
variance (s2 ) .
m
The t-test uses these data summary measures to calculate
a t-statistic (t*) and a comparison t-statistic (tc). The t*
value is compared to the tc value and a conclusion reached as
to whether there has been a statistically significant change
in the indicator parameter value.
The t-test for the difference of two groups is given by:
xm ~ xb
75
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If the t* is negative (except for pH), then there is no
significant difference between the monitoring data and
background data.
The t-statistic (tc) against which t* will be compared,
necessitates finding tb and tm from Table 2-4 where,
tb = Table 2-4 with (nb-l) degrees of freedom, 0.01 level
of significance; and
tm = Table 2-4 with (nm-l) degrees of freedom, 0.01 level
of significance.
[NB: if pH is being examined, use 0.005 as the level of
significance]. Finally, the special weightings Wb and Wm
are defined as:
2 2
sb sm
^ = and Wm =
nb nm
and so the comparison t-statistic is
wbfcb + wmtm
wb + wm
The t-statistic (t*) is now compared with the comparison
t-statistic (tc) using the following decision-rule:
If t* is equal to or larger that tr, then conclude that
there mostlikely has been an increase in indicator
parameter. [In the case for pH, Tt Fs" decrease if the
t* as originally calculated was negative, and increase
if the original t* was positive.1~
If t*is less than tn, then conclude that most likely
there has not been a change in indicator parameter.
The procedure described above is known as Cochrans'
Approximation to the Behrens-Fisher solution of the comparison
of two independent samples with unequal population variances.
For further information, see Snedecor and Cochran (1967) or
Steel and Torrie (1960).
Example of the t-test
These readings represent TOC values collected from a
hazardous waste disposal facility. Background well samples
76
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Table 2-4
The Critical t-values at the 0.01 and 0.005 Levels
Degrees of
Freedom
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
40
60
120
Adapted from
Agricultural
of Significance
Level of Significance Level
= 0.01
31.821
6.965
4.541
3.747
3.365
3.143
2.998
2.896
2.821
2.764
2.718
2.681
2.650
2.624
2.602
2.583
2.567
2.552
2.539
2.528
2.518
2.508
2.500
2.492
2.485
2.479
2.473
2.467
2.462
2.457
2.423
2.390
2.358
2.326
Table III, Statistical Tables for
and Medical Research, Fisher and
of Significance
= 0.005
63.657
9.925
5.841
4.604
4.032
3.707
3.499
3.355
3.250
3.169
3.106
3.055
3.012
2.977
2.947
2.921
2.898
2.878
2.861
2.845
2.831
2.819
2.807
2.797
2.787
2.779
2.771
2.763
2.756
2.750
2.704
2.660
2.617
2.576
Biological ,
Yates , 1963.
77
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were collected quarterly and four determinations made on
each quarterly sample. For the purposes of this example,
only one monitoring well will be considered.
BACKGROUND WELL MONITORING
1st Quarter 2nd Quarter 3rd Quarter 4th Quarter WELL
20
15
15
19
For the
12
12
13
13
background
15
16
14
15
data the mean
20 -i- 12 + 15
6
9
10
9
(X~b) is,
. . . + 9
42
43
38
36
16 , or
)Cb = 13.31
2
and the background variance (sj-,) is,
(20-13.31)2 + (12-13.31)2 ... + (9-13.31)2
sb = 16-1
or
55 = 13.43
For the monitoring data, the mean (X~m) is,
— 42 + 43 + 38 + 36
Xm = 4 , or
Xm = 39.75
and the monitoring variance ( sm ) is
(42-39.75)2 + (43-39. 75)2 + (38-39. 75)2 + (36-39.75)2
2 _
sm = 4-1
sm = 10.92
xm ~ xb
, and for this example,
t* =
nb
78
or
-------
39.75 - 13.31
t* =
'10.92 + 13.43 , or
4 16
t* = 13.99
Now, from Table 2-4
tb = Table 2-4 with 15 degree of freedom, significance
level = 0.01,
tb = 2.602,
tm = Table 2-4 with 3 degree of freedom,
significance level = 0.01,
tm = 4.541.
The weights are:
sm 10.92
Wm = = ... = 2.7300,
nm 4
and
2
Wb = sb
~
Therefore,
Wbtb + Wmtm
tc = , and for this example ,
wb + wm
tc = (0.8394 x 2.602) + (2.7300 x 4.541) ,
(0.8394 + 2.7300)
giving tc = 4.085.
As t* (=13.99) is larger than tc (=4.085), the conclusion is
that there has been a statistically significant increase
in TOC level. In this particular example the procedure of
§265.93(c)(2) concerning obtaining, splitting and analyzing
additional samples would then be followed.
79
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Owner or Operator Response to the Statistical Analysis
Student's t-Test Results for Upgradient Wells
A student's t-test for an upgradient well that shows a
significant increase in the concentration or value of an
indicator parameter (or decrease also in pH value) may mean
that sources other than the facility may be affecting ground-
water quality. If comparisons of the concentrations of
indicator parameters for the upgradient wells show a
significant increase (or also pH decrease), the owner or
operator must submit this information in accordance with
§265.94(a)(2)(ii) (see Section 2.5.3).
Possible conditions that could cause an indication of
ground-water contamination in upgradient wells include:
- error in sampling and/or analysis of ground-water;
- actual contamination of ground water (e.g., due to a
discharge, spill or other incidents upgradient of the
facility) ;
- actual contamination due to a facility discharge and
a mounding effect of contaminated ground-water beneath
the facility; and
- actual contamination of ground water due to a facility
discharge and a change in hydraulic gradient, so that
the originally upgradient wells are now downgradient
relative to the facility. This condition should be
reflected by data on the ground-water surface
elevations.
Student's t-Test Results for Downgradient Wells
A student's t-test for any downgradient well that shows
a significant increase in the concentration or value of an
indicator parameter (or decrease also for pH) signals possible
ground-water contamination and is the first indication of
a possible facility discharge. Section 265.93(c)(2) requires
that if the comparisons for downgradient wells made under
§265.93(b) show a significant increase (or also a pH decrease),
the owner or operator must then immediately obtain additional
ground-water samples from those downgradient wells where a
significant difference was detected, split the samples in
two, and obtain analyses of all additional samples to determine
whether the significant difference was a result of human
error. If the previous results are refuted and no significant
change has occurred, the detection program can be resumed per
the original schedule.
80
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If the additional analyses performed under §265.93(c)(2)
confirm the significant increase (or pH decrease), the owner
or operator must provide written notice to the Regional
Administrator - within seven days of the date of such confirmation
- that the facility may be affecting ground-water quality.
The written notice should include the relevant calculation(s)
performed according to §265.93(b). The owner or operator
must then develop and submit to the EPA Regional Administrator
a ground-water quality assessment program plan within 15 days
of the written notice (see Section 3).
2.5.3 Recordkeeping and Reporting
Recordkeeping
Owners or operators are advised to keep records of all
professionally certified designs and analyses performed in
accordance with the preceding parts of this section. These
records should be maintained in an orderly fashion, possibly
part of the sampling and analysis plan if appropriate, and
be made available to Agency personnel during facility inspections.
The outline in the Table of Contents may provide a convenient
format for most facilities, but as mentioned in Section 1.3,
Program Implementation, the Agency has decided not to prescribe
a rigid format for the on-site documentation. Since lab
reports, well logs, consultant reports and other components
are not readily adjustable to a fixed format, it would be
counter-productive to suggest one.
The detection monitoring system capability should be
demonstrated first by showing the rationale for sampling
points, second by defense of the frequency (whether minimum,
additional or alternate), and third by discussion of the
adequacy of the indicator parameters to assure detection.
The system compliance with casing and sealing requirements
may take the form of a geologist's certification of inspection.
Lab reports should be clipped or inserted directly into the
records in looseleaf.
Detection program records will serve as a history of
whether the facility has affected ground-water quality of
the underlying aquifer (i.e., through statistically significant
changes in indicator parameter values). Section 265.94(a)
requires that, unless the ground water is monitored to satisfy
the requirements of §265.93(d)(4) (assessment program
monitoring), the owner or operator must keep records of the
analyses required in §265.92(c) and (d), the associated
ground-water surface elevations required in §265.92(e) and
evaluations in §265.93(b) until final closure of the facility,
and, for disposal facilities, throughout the post-closure
care period as well. Such records include:
81
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- measurements of the ground-water surface elevation at
each monitoring well for each sampling event;
- analytical results for:
0 drinking water suitability parameters;
0 ground-water quality parameters;
0 contamination indicator parameters; and
- calculated results for the contamination indicator
parameter data:
0 arithmetic mean
0 variance
0 Student's t-test.
The records of these data should be organized in such a
way as to clearly show: any relevant statistically significant
difference(s), the exact location(s) and date(s) of any such
significant difference(s), and a chronology of events of
potential contamination according to well location since the
start of ground-water monitoring at the facility. In addition,
since changes in the ground-water conditions may occur very
slowly, the values and concentrations of all the indicator
parameters should be recorded so that any gradual changes
over time and space are readily observable and can be studied.
These records will be valuable in determining the significance
of increases and decreases in indicator parameters. Since
this information may help to identify the type and extent of
any ground-water contamination, it could also aid in the
successful implementation of a ground-water quality assessment
program.
Reporting
As previously discussed, the owner or operator must
submit a report identifying parameters listed in §265.92(b)(1)
whose values exceed the maximum contaminant levels for those
parameters of 40 CFR 265 listed in Appendix III (see Appendix
C of this document). The report axust be submitted within
15 days of the analysis, and separately identify the background
well and downgradient wells, the parameter exceeding, and
the concentration.
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After the first year's sampling and establishment of
background values for the indicator parameters of §265.92(b)(3)
downgradient values statistically differing from background
must be reported within 7 days. Upgradient values statistically
differing must be reported annually, along with recommendations
for revising the background values.
If the evaluation of ground-water surface elevations
under §265.93(f) indicates a gradient change which affects
the system capability, a description of the response to that
evaluation, where applicable, must be reported. Reports of
the above information are to be submitted to the Regional
Administrator until final closure of the facility, and for
disposal facilities, throughout the post-closure care period
as well.
[Note; Annual reporting of ground-water monitoring
information under §265.94 is due by March 1 of each year,
along with the annual report under §265.75, or independently,
if §265.75 is modified].
2.6 Waiver Demonstration
The waiver demonstration, as provided in §265.90(c), is a
variance mechanism by which owners and operators design and
defend any reduction in the monitoring programs required by
Subpart F. The reader is referred to Section 1.2, above, for
discussion of the rationale of waiver provisions. While the
reduction or elimination applies to either or both the detec-
tion and assessment program, it is discussed in Section 2 of
this manual because of the similarity of the approaches in
detection monitoring and demonstrating a waiver. That is,
similar hydrogeological investigative techniques (e.g., use
of boreholes and remote geophysics) will likely be necessary
for each.
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On January 11, 1981 the regulations were amended, by
addition of §265.90(e), to extend the waiver provisions to
apply to neutralization surface impoundments. Those facilities
shown to rapidly neutralize corrosive wastes, and to contain
no wastes exhibiting other hazardous characteristics, are now
eligible to waive the ground-water monitoring requirements.
Owners and operators of such facilities must prepare a written
demonstration showing that there is no potential for migration
of hazardous wastes out of the facility. The demonstration
would have to show, based on consideration of the corrosive
wastes and the impoundment, that the corrosive wastes will be
neutralized before they migrate out of the facility. The
demonstration must be certified by a professional qualified
to make this type of technical demonstration (e.g., a chemist),
rather than necessarily by a geologist or geotechnical engineer
(as required in §265.90(c)).
Under §265.90(c) a written demonstration of a low
potential for ground-water contamination is necessary in
order to substantiate a waiver. This demonstration must be
based upon the site hydrogeology and certified by a qualified
geologist or geotechnical engineer. The certifying geologist
or geotechnical engineer should be present during any field
testing so that he may supervise and gain first-hand knowledge
of the site hydrogeology.
This discussion is intented to explain the criteria for
a waiver demonstration under §265.90(c) to provide guidance
in obtaining the necessary hydrologic data, and subsequently
to guide readers in the preparation of the written demonstration,
Determining the potential for ground-water contamination
involves an evaluation of the hydrogeologic factors in a
water balance, characteristics of the unsaturated and saturated
zones, and the pathway between the facility and water supply
wells or surface water. The water balance determination is
important because it will indicate the quantity of leachate
that could be discharged by a facility. Evaluation of
unsaturated and saturated zone characteristics will provide
information in the rate at which contaminants will migrate
and the extent to which contaminants may be attenuated in the
subsurface environment. Determining the location and proximity
of water supply wells and surface waters and the existence of
an interconnection or pathway is necessary for establishing
the likelihood of ground-water contaminants reaching and
impacting these receptors.
The waiver demonstration requires a thorough evaluation
of criteria for determining the potential for contamination
of ground-water supplies and surface water. In order to
protect human health and the environment, ground-water
84
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monitoring requirements are not to be waived for reasons such
as:
unsuitability of the uppermost aquifer for drinking
water;
- expense of complying with ground-water monitoring
requirements; and
facility design.
The waiver mechanism allows varying degrees of deviation
from the ground-water monitoring requirements. The lower the
demonstrated potential for contaminant migration, the waiving
of more requirements may be justified. For instance, if the
unsaturated zone consists of a thick formation of very low-
hydraulic conductivity and the ground water moves at a slow
rate, the potential for contaminant migration is low and may
warrant a reduced frequency of sampling of ground-water
monitoring wells. A complete waiver from the ground-water
monitoring requirements would be very difficult to demonstrate
since it must be established that there will be no potential
for migration of hazardous waste or hazardous waste constituents
through the uppermost and any interconnected aquifers to
water supply wells or surface water without regard to time.
The Regional Administrator can request, at any time, to
examine the written waiver demonstration, prepared by the
owner or operator, to evaluate the supportability of the
waiver. Also, waiver demonstrations will be routinely examined
as part of facility inspections. Appropriate data and
investigatory techniques for a waiver demonstration are
described below.
2.6.1 Determining Potential for Contaminant Migration from
Facility to the Uppermost Aquifer
In order to establish the potential for migration of
hazardous waste or hazardous waste constituents from the
facility to the uppermost aquifer, the owner or operator is
required to evaluate a site water balance and unsaturated
zone characteristics. The following discussions explain
these components.
Determining the Water Balance
The infiltration fraction of precipitation is the
principal contributor to leachate generation from a hazardous
waste management facility. Infiltration into cover material
(if present) and any subsequent percolation down to the waste
material, to the unsaturated zone, and eventually to ground
water will be determined by surface conditions of the facility
and by the hydrogeologic characteristics of the facility's
location.
85
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The water balance, as developed in the soil and water
conservation literature, is based upon the relationship among
precipitation, evapotranspiration, surface runoff and soil
moisture storage. Precipitation represents that amount of
water added. Evapotranspiration, the combined evaporation
from plant and soil surfaces and tranpiration from plants,
represents the transport of water from the earth back to the
atmosphere, the reverse of precipitation. Surface runoff
represents water which flows directly off the area of concern.
Soil moisture storage represents water which can be held in
the soil. Water balance calculations, employing the above
parameters, can be solved to determine the percolation to
ground water. Knowledge of the volume and placement of waste
material can, further, provide an estimate of the
potential amount of leachate which could be discharged from
the facility. The water balance can be expressed as:
P - R = I;
I - AET = Perc;
where P = precipitation;
R = runoff;
I = infiltration;
AET = actual evapotranspiration; and
Perc = percolation.
If I minus AET is positive, over a given time interval,
then soil moisture storage will increase. After the soil
moisture storage reaches its maximum, any excess infiltration
becomes percolation through the cover soil (if any) and waste
materials, eventually reaching ground water. Therefore,
significant percolation will occur during those time intervals
when I exceeds AET and the soil moisture storage exceeds its
maximum. For most humid areas, this will occur during the
wet season. For dry areas, significant percolation may occur
only in very short episodes if at all. For methods of
determining the water balance, see Fenn, et al (1975) and
Thornthwaite and Mather (1955, 1957).
The following discussion provides further information on
the water balance factors and also provides methods of
obtaining the needed data.
Precipitation
Precipitation data is tabulated in the form of mean
monthly values for 30-year periods for each National Weather
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Service station across the country. This information can be
requested from the National Climatic Center, Federal Building,
Asheville, NC 28801, 704/258-2850 (see Figure 2-16). Other
possible sources for monthly precipitation data include State
Departments of Agriculture, local universities, and associated
technical publications. On-site field measurements should be
used to validate regional data for the site; an onsite survey
will be needed if suitable data is not available.
The owner or operator should obtain mean monthly
precipitation values for the weather station closest in
location and geographic characteristics to his facility (e.g.,
a coastal station often does not accurately reflect the
precipitation characteristics of an inland location, despite
close proximity). In the case where the station does not
accurately reflect the precipitation at the facility site or
the data is incomplete (e.g., missing records) or of questionable
reliablility (e.g., discrepancies in values), the owner or
operator should obtain more accurate data from alternate
sources. Available on-site or nearby determinations are highly
desirable. Consistent relationships may be entered into a
calculated P-value. Once precipitation data has been obtained,
the mean monthly values should be tabulated for each month
and retained for later use in these calculations. Recorded
anomalies should also be tabulated when significant and
available.
Evapotranspiration
Evapotranspiration is the amount of water returned to
the atmosphere as vapor through the combined action of
evaporation and transpiration. If, as is often the case, the
overall amount of evaporation cannot reliably be measured
separately from transpiration, the two effects are considered
together as "evapotranspiration".
Several techniques are available for calculating potential
evapotranspiration. Well-known methods include: Thornthwaite
(1948), Blaney-Criddle (1962) and Penman (1948). Conversion
from potential to actual evapotranspiration is generally
performed using a soil moisture budget approach (e.g., Holmes
and Robertson, 1959).
Evapotranspiration values obtained should be tabulated
by month, as with the precipitation data. It should be noted
that no completely successful technique for estimating
evapotranspiration has been devised to date. Therefore, the
above-listed methods should be evaluated for their applicability
to site-specific conditions. Where soil temperatures, solar
loading due to slope, ground cover, etc., or wind velocity
and humidity may significantly affect AET, these should be
separately introduced into the calculation.
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Figure 2-16
ample of Monthly pFecipltation
Records
PRECIPITflTION NORtlflLS
MCMTMt ) ISC
CUMATOGBAPHY Of THE UHIIED STATES NO. II (8T STATE) '
Monthly Normals of Temperature,
Precipitation, and Heating and
Cooling Degree Days 1941-70
•MM* =
'*«?s-s$2^^^^&2£raw5 sr&s—'" —
""k^-— " '•• V*~^--'"g»y<«. «.c-ii o~
88
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Runoff
Runoff is the amount of incident precipitation that becomes
overland flow before it has a chance to infiltrate. The amount
of actual surface runoff varies with the intensity and duration
of the storm, the antecedent soil moisture condition, the
permeability and infiltration capacity of the soil, the
slopes, and the amount and type of vegetation cover. Although
it is difficult to account for all these factors in estimating
runoff, most available methods account for at least some of
the above-mentioned factors.
There are several methods for estimating the runoff
fraction of incident precipitation. Although it will, in
most cases, underestimate surface runoff, the "Rational
Runoff" formula is presented here as one of the more convenient
methods. The "mean monthly surface runoff" (R) can be
calculated as follows:
R = P x CR;
where P = mean monthly precipitation; and
CR = empirical runoff coefficient (see
Chow, 1964).
The runoff coefficient CR provides the means of estimating
surface runoff quantities for given site conditions. The
coefficients take into account a variety of vegetation types,
soil types and slope steepness, and have been tabulated (e.g.,
by Chow, 1964). The owner or operator should match his site
characteristics against those listed in the tables (e.g.,
Chow, 1964) and select the coefficient for the site
characteristics which most nearly approximate his own site.
The owner or operator should tabulate the mean surface
runoff values by month.
Infiltration
Infiltration is the amount of precipitation that enters
the surface of the soil. It represents a source of moisture
that may eventually percolate through the facility and
unsaturated zone into the ground water.
Infiltration can be calculated using the values derived
in the preceding discussions as follows:
I = P - R.
This calculation should be performed for each month unless
anomalies indicate otherwise. A negative value for I indicates
that the amount of infiltration is not sufficient to exceed
soil moisture storage capacity (i.e., no percolation is likely
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to occur). A positive value for I indicates soil moisture
storage recharge and potential percolation.
Percolation
Percolation is calculated as follows:
Perc = I - AET.
By determining the percolation rate, the area and depth
of the waste, and waste/soil moisture storage capacity, the
owner or operator can derive a rough estimate of potential
leachate volume (see Fenn, et al, 1977, pp. 212-214 for
further details).
Facility Site-specificity
The water balance method is a useful tool for evaluating
the potential for contaminants to migrate through the unsaturated
zone. However, it must be recognized that certain site-specific
assumptions are necessary to tailor the method to a particular
site. These assumptions are incorporated into the choice of
precipitation data, and the choice of methods for determining
evapotranspiration and surface runoff. In addition, conditions
such as bare soil/lack of vegetation, irrigation (e.g., by
land treatment), frozen ground and snow-melt must be accounted
for where they affect the site (Fenn et. al., 1975).
The water balance method can be used to calculate
infiltration at land treatment facilities. In this approach,
the applied liquid waste and precipitation are volumetrically
summed as the input, and infiltration is computed as the
difference between this input and evapotranspiration. Applied
liquid waste volumes can be determined from operating records.
Precipitation volumes can usually be extrapolated from rainfall
gaging stations in nearby areas. Monthly rainfall determinations
are often suitable; however, in areas with highly variable
precipitation, such as in Southwestern States, onsite
measurements may be necessary.
Evapotranspiration from areas where land treatment is
practiced can be determined by a number of methods (Gruff
and Thompson, 1967; Blaney and Griddle, 1962; Lowry and
Johnson, 1942; Penman, 1948; and Thornthwaite, 1948). These
methods are generally based on different groupings of
climatological parameters. For example, the Blaney-Criddle
method depends primarily on temperature and percentage of
daylight hours. In general the Penman and Thornthwaite
methods are more applicable to humid areas, where the
BlaneyCriddle method is more applicable to semiarid areas.
Different values of evapotranspiration and consumptive use
are usually obtained for different vegetation and soil
conditions. Thus, the vegetation pattern must be known.
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Sufficient field tests have been conducted in many areas so
that evapotranspiration and consumptive use are well
established. In some areas, data may have to be extrapolated
from similar areas. Evapotranspiration rates will generally
be needed on at least a monthly basis, and sometimes weekly.
In the water balance for land treatment, the infiltrating
component is divided into two portions. A portion of this
component is diverted into soil moisture storage. This soil
moisture component will be gradually depleted by transpiration
during periods of zero recharge. It should be noted that
evapotranspiration calculations which continue to indicate
evapotranspiration during depleted periods give distorted,
unacceptable results. When the field capacity requirements
have been satisfied the remaining portion will percolate to '
the zone of saturation.
The water balance method can also be used to calculate
discharge from surface impoundments. Waste discharge and
precipitation are volumetrically summed as the input, and
discharge is calculated as the difference between input and
evaporation. Storage changes in the impoundment must also be
taken into account. Evaporation from free-water surfaces
can be determined from measurements using land pans or floating
pans (Harbeck et al, 1958; Kohler et al, 1955; Follansbee,
1933; and Rohwer, 1933). Monthly values will often suffice;
however, in some cases weekly or daily values are necessary.
Factors such as salinity of waste liquid can affect the
evaporation rate. In general, with increasing salinity the
vapor pressure of water decreases, resulting in a lower
evaporation rate. In considering evaporation from free-water
surfaces from impoundments of different sizes, consideration
should be given to edge effects. That is, evaporation rates
depend on the characteristics of the surrounding land, for
example, whether it is cultivated or undeveloped.
When applying the water balance to landfills, precipitation
volumes must be obtained and the portion that infiltrates the
landfill determined. This portion will first go into meeting
the moisture storage requirements of the waste and cover
material. For this reason the moisture content of the waste must
be estimated. When the waste reaches field capacity percolation
will result.
The results of water balance calculations do not represent
absolute values of potential for contaminant migration.
Instead, the resulting values will be used in concert with
all other factors provided by the waiver demonstration in
evaluating the relative potential for contamination.
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Determining Unsaturated Zone Characteristics
The topsoil and materials of the unsaturated zone may
have a significant but sometimes temporary capacity to remove
a limited quantity of contaminants from downward-percolating
waters. The extent of ground-water contamination due to
waste percolation from the land surface depends strongly on
the rate and volume of recharged water. In a semiarid or
arid climate, contaminants may be retained above the water
table in a nearly permanent fashion. On the other hand, in
humid areas contaminants may be rapidly carried downward from
the land surface to the water table. Generally, in a
homogeneous porous media, percolating water will pass vertically
through the unsaturated zone. However, in a heterogeneous,
stratified material (e.g., most of the alluvial deposits of
the western U.S.), percolating water may become perched above
layers of low hydraulic conductivity. In this situation,
lateral movement for substantial distances can occur above
the water table.
The capacity for attentuation of many potential contaminants
is greatly affected by the amount and characteristics of the
geologic materials present in the unsaturated zone. This is
especially true for the sorption capacity of many organic
chemicals and trace elements. This limited capacity for
removal of some contaminants is in sharp contrast to the
almost unlimited ability of many unconsolidated materials to
remove bacteriological contaminants. The existence of many
documented case histories of ground-water contamination
indicates that the unsaturated zone may often not provide
complete protection. Problems can occur when attenuation
capacity is exceeded due to high waste loadings.
Identify Geologic Materials
The owner or operator should begin to investigate the
characteristics of the unsaturated zone by collecting available
information about the geology underlying the facility area
prior to any field testing. Background information will
provide initial identification of materials, indicate areas
where data is lacking, indicate which field tests should be
performed, and later may serve to verify field data or indicate
what further testing is needed.
Information abour reginal and site-specific geology
should include:
- topography, surface relief;
geologic structure, locations and patterns
of major fractures, joints and solution
cavities;
- characteristics, thicknesses and areal
distribution of soils;
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thicknesses of formations, stratigraphy,
lithology, and formation homogeneity and
continuity; and
- hydraulic conductivity.
Some sources for this information are listed in Table 2.1.
This information should be evaluated to determine existing
descriptions of geologic materials in the facility area.
Once data gaps have been identified, field techniques should
be used for verification and to supply additional information
on the identity of on-slte geologic materials. For example,
boreholes are one method of direct investigation of the
subsurface, and are particularly necessary in support of
direct methods. Formation samples collected from boreholes
can provide data on the identity of geologic materials in the
unsaturated zone and on the thicknesses of formations.
Samples that have been collected from boreholes or preliminarily
identified in the field should be sent to a qualified soils
laboratory for identification confirmation and other appropriate
tests.
Indirect geophysical techniques, such as geophysical
logging, surface electrical resistivity and seismic surveys
can provide augmentation to the information about site geologic
materials. They are particularly useful in demonstrating
continuity between direct sampling points.
Discussions of procedures, applicability, advantages and
disadvantages of direct and indirect field methods of subsurface
investigation are presented in Sections 2.2.1, 2.2.2 and 3.3.
Determining Physical Properties and Depth to Ground
Water in the Unsaturated Zone
The hydraulic conductivity (K) of materials within the
unsaturated zone is an important factor in determining
contaminant pathways and the potential and/or time needed for
contaminants to reach ground water. Low K values (e.g.,
10"~8 cm/sec) may be used in support of a waiver demonstration.
Such values can be found in earth materials such as unfractured
clays and shales. (Methods for determining K are presented
in Section 3.2). When gathering data concerning K values,
the owner or operator should evaluate and document, at least,
the following:
variations in K areally and with depth; and
- continuity and thicknesses of materials with given K
values.
Thick unsaturated zones (e.g., 100 meters), in conjunction
with low K values, can be supportive of a waiver demonstration.
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Thickness data should be established through reliable methods
(e.g., borehole logging). Such information should not be
obtained by boring through the waste management area, as this
could provide a direct conduit for hazardous wastes to reach
the ground water.
Depth to ground water should be accurately determined
within the facility area (see Sections 2.2.1 and 2.2.2
concerning historical records, piezometers and water table
wells, and water-level measurement techniques). Water level
elevation data should be used to construct flow nets which
indicate hydraulic gradients and ground-water flow directions
(see Section 2.2.2 for a discussion on flow net construction).
Water elevation and unsaturated zone thickness data are needed
to determine the distance contaminants must travel to reach
the uppermost aquifer.
Evaluating Attenuation Capabilities of the Unsaturated
Zone (adapted from Todd, et al, 1976)
Various factors and processes affect the mobility of
contaminants moving through the unsaturated zone. Close
examination and documentation of the effects of these factors
and processes may lend credence to a waiver demonstration.
Contaminant attenuation in the subsurface commonly occurs
due to the following processes: dilution, filtration,
sorption, buffering, precipitation, oxidation and reduction,
volatilization, biological degradation and assimilation.
Dilution
One of the mechanisms of attenuation frequently mentioned
in the literature is dilution. The obvious limitations for
use of dilution to substantiate a waiver preclude its use as
a primary basis at landfills and surface impoundments.
Continuous sources of contaminants in laminar flow situations
cannot be shown to be so dilute that they meet the "no or low
probability" criterion for a waiver. Dilution as discussed in
this section is of course a factor in attenuation. It may
have applicability in waiver demonstrations in unusual cases
unforeseen by the Agency, and of course, it is a necessary
consideration in design of detection programs. Therefore, it
is included here primarily for sake of completeness.
Dilution above the water table can be substantial in
humid areas and almost nonexistent in arid areas. Sources
of water for dilution include precipitation, seepage from
streams, lakes and canals, and artificial recharge. The
quality of water from each source of recharge should be
estimated if, in the judgement of the geologist or geotechnical
engineer, it might be a significant factor. A comparison of
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the respective quantities of water and constituent concentrations
in a waste discharge at the land surface can indicate the
extent of subsequent dilution of contaminants.
An example is presented in the following discussion.
Assume an agricultural area in the West where irrigation is
practiced in the dry summer months and rainfall occurs in the
wet winter months. Return flow over the area averages 18
inches per year and the salinity of this water is 300 parts
per million (ppm). Rainfall is 12 inches per year and its
salinity is 10 ppm. Consideration of the water balance
analysis at the land surface indicates that 9 of the 12 inches
of rainfall percolates to the water table. The maximum
subsequent dilution, presuming thorough mixing, can be
calculated by the equation:
AVA + BVB = C;
where V^ and VQ are respective percentages of water
from return flow and precipitation. A, B, and C
are the respective salinities of the return flow,
precipitation, and the mixture of the two. In this
example:
C = 300(18/27) + 10(9/27)
C = 200 + 3 = 203 ppm.
This dilution theoretically reduced the salinity by about one-
third of the original value. This simple concept can be
expanded to encompass dilution from a number of sources of
contamination. The resultant concentrations of contaminants
of concern is reduced. Technically, attenuation has occurred.
As noted, however, the contaminants are no less likely to
enter ground water, and no support is foreseen for waiver
demonstration.
Filtration
Filtration can remove many of the suspended materials
that would be of concern. However, this process is generally
not effective for dissolved and other liquid phase materials
except as precipitates form due to chemical reactions. Since
most leachate of concern is not filterable except as precipitants
too complicated to predict, no guidance is available from the
Agency on filtration as a factor.
Sorption
Sorption is probably one of the most effective but most
unpredictable processes for attenuating ground-water
contaminants. Clays, metallic oxides and hydroxides, and
organic matter can all be suitable materials for sorption of
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various contaminants. Many contaminants can be sorbed and
removed to some extent under favorable conditions. Under
other circumstances, however, the contaminants can move freely
through the porous media. The pH and oxidation potential
often govern the extent of sorption for specific constituents.
The sorption process depends on the type of contaminant and
the physical and chemical properties of both solution and the
containing materials.
When a contaminant in ionic form is sorbed, some other
changes must occur to compensate for loss of the ion from
solution. In ion-exchange processes, a different ion is
released by the solid to the water. However, this release is
not required if the contaminants are sorbed or electrically
neutral, such as most organics and neutral complexes of
various metals.
The sorptive capacity can be estimated based on the
density, clay content, and cation exchange capacity of the
soil and geologic materials above the water table. Values
for these parameters can be calculated from available data in
soils and ground-water reports on the area of interest. In
exceptional cases, these parameters can be determined from
detailed onsite measurements. For calculation purposes, the
thickness of the unsaturated zone is known or determined from
water level data. For simplicity, the vertical path of
contaminated water from the land surface beneath the waste
management area to the water table can be assumed to be the
distance traveled.
As an example, assume the average density of materials
in the unsaturated zone is 1.6 grams per cubic centimeter,
the clay content is 20 percent by weight, and the clay has
a cation exchange capacity of 70 milliequivalents per 100
grams. Each gram of clay will have the ability to remove 0.70
milliequivalents of the constituent of interest. For example,
for potassium (equivalent weight of 39), each gram
of clay will have the ability to remove 27.3 (0.70x39)
milligrams of potassium from the percolated waste water.
Each gram of solid material will have the ability to remove
5.5 (0.20x27.3) milligrams of potassium from the percolated
waste water. With a density of soil of 1.6 grams per cubic
centimeter, one acre-foot (1.2335xl09 cubic centimeters) of
soil would contain 1.97xl09 grams of solid material. This
soil could sorb 23,900 pounds of potassium. For an unsaturated
zone 50 feet thick, one acre of the unsaturated zone could
sorb ov/er one million pounds of potassium, presuming uniform
applications in adsorbable doses, and no interference from
other constituents.
To determine the actual extent of adsorption, laboratory
tests can be performed utilizing soils and geologic materials
typical of the waste management site. The actual waste
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discharge can be used or a similar synthetic solution prepared.
Hajek (1969) summarizes laboratory procedures for such tests.
It should be noted that the percolating fluids may
subsequently remobilize species that have been sorbed. The
sorptive capacity of soils and geologic materials is finite
for most inorganic substances which cannot be biodegraded.
However, for substances which are biodegradable, such as many
bacteriological constituents and nitrogen, the sorptive
capacity may be renewed indefinitely.
Buffering
The pH is a critical factor in many reactions involving
contaminants. Buffering is the resistance to a pH change of
the soil solution. The basis of buffer capacity lies in the
adsorbed cations on the exchange complex of the soil. The
higher the exchange capacity, the greater will be the buffer
capacity. The portion of the cation exchange capacity occupied
by exchangeable bases is termed base saturation. There is
a correlation between base saturation and pH, with higher
base saturation for higher pH. The degree of buffering is
lowest at the extremes of base saturation, and highest at
intermediate base saturation values.
The extent of buffering in most cases will be relatively
unimportant if the pH of the waste discharge is between 6 and
9. These pH values correspond to those commonly found in
natural ground water. Wastes with a pH in this range will
generally be buffered to an extent that the percolating waste
water will present no unusual problem. Consideration of
buffering is thus of foremost importance in cases of disposal
of very acidic or basic wastes. Detailed considerations are
presented in Buckman and Brady (1969).
Chemical Precipitation
It is theoretically possible to precipitate almost any
dissolved species from solution. However, in soil-groundwater
systems, the necessary species often are not present in
sufficient quantities to precipitate potential contaminants.
Certain constituents are normally present and available for
reaction in most ground water, soil, and geologic materials.
Calcium, magnesium, sodium, potassium, bicarbonate, sulfate,
chloride, and silica are usually the major species in ground
water. Iron, aluminum, nitrogen, and carbonate, in addition
to the previous constituents, may be found in soil and geologic
materials.
Due to the extreme complexity, this manual is not an
appropriate vehicle for guidance on chemical precipitation.
However, references such as Hem (1970), Stumm and Morgan
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(1970), Faust and Hunter (1967), and Gould (1967), detail
thermodynamic calculations which may be used to evaluate this
phenomenon. In many field situations data are commonly
lacking on some parameters of importance, thus judgement is
often necessary.
Oxidation and Reduction
The oxidation of organic matter in the topsoil is one of
the most important contaminant attenuation mechanisms.
Oxidation and reduction reactions often work in conjunction
with other mechanisms for contaminant attenuation. Besides
those reactions causing precipitation, reducing conditions
can also theoretically cause the formation of native elements
which are quite insoluble. Sulfides can react with certain
metals to produce highly insoluble precipitates, such as
sulfides of arsenic, cadmium, mercury, and silver.
Volatilization
Volatilization and release as a gas can be effective for
attenuating some ground-water contamination. For example,
mercury in solution can be volatilized in anaerobic environments
or by reactions with dissolved humic acids. Several organic
compounds of arsenic are volatile, and the escape of arsenic
as a gas has been demonstrated for both aerobic and anaerobic
soils. Selenium may be subject to volatilization because of
its chemical similarity to sulfur. The microbial reduction
of nitrate to gaseous forms of nitrogen is well documented.
No quantitative procedure is proposed to evaluate the extent
of this phenomenon. It is important to be aware of the
contaminants that may be affected.
Biological Degradation and Assimilation
These processes are very important in the removal of
organic and biologic contaminants. Many organic chemicals
can be attenuated or removed by biological activity in the
unsaturated zone. Nitrate, arsenic, cyanide, mercury, and
selenium are likely candidates for biologic fixation or
volatilization.
2.6.2 Determining Potential For Contaminant Migration Through
Uppermost Aquifer to Water Supply Wells or Surface Water
It is essential in protecting human health and the
environment to establish the potential for contaminants to
migrate through the uppermost aquifer, and any interconnected
aquifers, to water supply wells or surface water. The
Agency recognizes the potential interconnections between
aquifers at different depths. The potential for contamination
of relatively deeper aquifers may be low if, for example,
the two aquifers are separated by thick strata with low K
value and no effective hydrologic interconnections exist
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(e.g., fractures; abandoned, poorly sealed wells). Characterizing
the saturated zone by determining the geologic materials,
physical properties and velocity of ground-water flow will
indicate the potential rate and extent of contaminant migration
in the saturated zone. Continuity of the hydraulic pathway
from the facility to wells and surface water is of particular
concern. The distances, the ground-water flow velocity and
the flow direction are factors influencing contaminant entry
into wells and the surface water environment. The regulation
does not introduce time as a criterion; low probability in
terms of geologic time includes millenia.
Determining Saturated Zone Characteristics
Identify Geologic Materials
The geologic materials of the saturated zone are identified
by the same methods as previously described for the unsaturated
zone.
Determining Physical Properties and Rate of Ground~Water
Flow in the Saturated Zone
Field determination of K values within the saturated
zone is needed to identify probable contaminant pathways
(see Section 3.2 for methods of determining K). K can also
be determined in the laboratory and estimated from values
given in the literature for comparison to to field-obtained
values. Hydraulic conductivity data along with information
on porosity and hydraulic gradient can be used to compute
ground-water flow rates (see Section 3.2). Tracer techniques
can also be used to compute flow rates (see Section 3.2).
Flow rates should be determined in appropriate aquifer flow
zones in order to indicate directions of potential contaminant
migration and to calculate the time it would take contaminants
to reach any nearby water supply wells and/or surface waters.
This process should include flow net analysis as described in
the previous discussion of the unsaturated zone and Section
2.2.2.
Computer simulation and prediction models use a set of
mathematical equations that attempt to describe and quantify
the physical processes in an aquifer. These models can also
be used to estimate ground-water flow rate. In order to
determine where and when a ground-water flow model can be
applied, it is necessary to have a detailed understanding of
the aquifer's physical processes and the corresponding
mathematical model. Not all simulation models are appropriate
for all ground-water systems, and not all aquifers are amenable
to or necessarily require such modeling. For instance, those
aquifers involving a small area or a low level of hydrogeologic
complexity may have the most efficient solution to ground-
water flow rate via flow net analysis or analytical methods,
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such as application of the Darcy-based equation (see Section
3.2). A qualified person, such as the geologist or geotechnical
engineer required to certify the waiver demonstration, can
provide the expertise to judge the necessity of a modeling
study, the appropriateness of the model selected, the need
for any modifications to the model and accurate interpretation
of the results.
Hydrogeological data which should be considered for use
of a predictive ground-water model are listed in Table 2-5.
General sources of data for ground-water flow modeling include:
geologic and hydrogeologic reports and maps;
well log data;
water level measurements; and
pumping test data.
The Holcomb Research Institute at Butler University,
Indianapolis, Indiana maintains a computerized clearinghouse
for ground-water models that can provide model users with an
annotated list of models. Additional information on groundwater
models is available from the' U.S. Geological Survey, modeling
researchers, and the technical literature.
Evaluating Attenuation of Contaminants in the Saturated
Zone (adapted from Todd, et al, 1976)
Many of the attenuation processes which occur in the
unsaturated zone can also occur below the water table, but in
a modified manner. For example, the lower oxygen content
below the water table reduces the possibility of oxidation of
organic matter even when mixing does occur. Some contaminants
may be more mobile in the reduced state. Reducing conditions
are favorable, however, in some cases for contaminant removal
from water (e.g., nitrate). Another major consideration is
that organic matter, common in the topsoil, is virtually
absent in many types of geologic materials comprising the
aquifer. This would ordinarily decrease the extent of sorption
as well as reactions such as denitrification. In addition,
certain geologic materials, such as granite and limestone,
may lack many of the common substrates for sorption. The
dilution process below the water table differs greatly from
that operative in the unsaturated zone.
Processes Other Than Dilution
The attenuation processes do not generally have to be
considered in detail if the waiver demonstration is based
upon a low potential for any infiltration or leachate to
reach the saturated zone. In cases where the demonstration
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Table 2-5
Data Requirements to be Considered for a Predictive
Ground-Water Flow Model
Physical Framework
- Hydrogeologic map showing areal extent, boundaries,
and boundary conditions of all aquifers
- Topographic map showing surface-water bodies
- Water-table, bedrock-configuration, and saturated-
thickness maps
- Transmissivity map showing aquifer and boundaries
- Transmissivity and specific storage map of
confining bed
- Map showing variation in storage coefficient of
aquifer
- Relation of saturated thickness to transmissivity
- Relation of stream and aquifer (hydraulic connection)
Stresses on System
- Type and extent of recharge areas (irrigated areas,
recharge basins, recharge wells, etc.)
- Surface-water diversions
- Ground-water pumpage (distributed in time and space)
- Stream flow (distributed in time and space)
- Precipitation
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depends on saturated zone attenuation, detailed consideration
of these processes is necessary. Filtration and sorption
were treated in the unsaturated zone discussion. In saturated
flow, contaminant movement is generally horizontal and,
instead of utilizing a thickness of unsaturated zone beneath
a waste management site, a volume of the aquifer will indicate
the maximum attainable dilution. Generally, this will
correspond to the projected, aggregate pore space volume and
location of a discharged waste plume at a specific time.
This volume can be estimated by utilizing flow net analysis
to determine the vertical and horizontal direction of
groundwater movement from beneath the waste management site.
Specific distances from the waste discharge site, such as 100
feet, 500 feet, and 1000 feet, can be chosen and volumes of
materials calculated for each.
Laminar flow and other ground-water phenomena result in
incomplete mixing within the maximum potential mixing volume.
Consideration must also be given to contaminants which do not
readily mix with ground water (e.g., contaminants which
migrate along the top of the water table and those which
migrate along the bottom of the aquifer).
Buffering can be handled as discussed for the unsaturated
zone. Generally, this is not of great concern unless extremely
acidic or alkaline wastes are discharged directly to the
saturated zone. Chemical precipitation can be handled as
described for the unsaturated zone, but evapotranspiration is
not a factor in concentrating solutions. In addition, the
materials are continuously saturated below the water table
and are usually not exposed to drying. Oxidation and reduction
can be handled as for the unsaturated zone. However, in the
saturated case, oxidation is generally less important and
reduction is more important than in the unsaturated zone.
Dilution and Related Factors
Once percolating wastes reach the saturated zone, in
most dynamic ground-water systems there will be some physical
attenuation of contaminant concentrations with distance from
the intersection with the water table. The attenuation
occurring in most cases is determined by the following factors:
the volume of a waste discharge reaching the water table;
the waste loading (i.e., the mass per unit area of
contaminant reaching the water table);
areal hydraulic head distribution, as indicated by
water-level elevation contour maps;
transmissivity of aquifer materials;
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vertical hydraulic head gradients and vertical hydraulic
conductivities through confining beds which are present;
quantity and quality of native ground water available
for mixing;
quantity of recharge reaching the water table from
other sources at the land surface; and
- chemical characteristics of recharge reaching the
water table from other sources.
The first two factors determine the concentration of
contaminants reaching the water table. The next several
factors, along with hydraulic conductivity, determine the
direction and magnitude of ground-water flow in the area and
the quality of native ground water with which the discharged
waste will mix. The last two factors determine the effect of
recharge from other sources on contaminant concentration.
A first approximation of dilution can be obtained by
assuming that the waste discharge enters a certain part of
the aquifer; for example, the upper 10 feet, 50 feet, or 100
feet, over a certain area. Knowledge of the extent of ground-
water contamination in historical situations in the area or a
comparable area can be used to make this evalulation.
Secondly, water reaching the water table from other sources
of recharge and ground-water inflow from nearby areas usually
tends to dilute the waste discharge. The dilution can be
calculated if the volume and quality of the various sources
of water are known. Conservative constituents, such as
chloride, can be used for a first approximation of dilution.
In most cases, the contaminant of interest will be less mobile
and thus occupy a smaller plume than a mobile constituent
such as chloride. Ground-water outflow tends to carry
contaminants away from the waste management site.
Water level elevation maps and flow nets can be used to
consider whether the waste discharge is in an area of converging
or diverging ground-water flow, which affects dilution.
Vertical head gradients indicate whether wastes could move to
deeper levels of the aquifer or whether deeper aquifer water
could move up and dilute the wastes. Both cases tend to
accentuate mixing or dilution. Aquifer transmisivity can be
used to calculate ground-water flow rates into and out of an
area. The quality of sources other than the waste discharge
and native ground water will obviously affect dilution as the
lower concentration waters will exert relatively more dilution.
The foregoing factors can be integrated into a mass balance
analysis, both for the waste discharge and for the individual
contaminants.
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Wells affect dilution in several ways:
Gravel packs or perforations if improperly designed
can act to short-circuit confining beds and allow
vertical movement of contaminants near the well.
Well pumping can drastically alter flow patterns,
both horizontally and vertically.
Well pumping can remove contaminants from ground
water and expose them to subsequent loss at the land
surface or in the topsoil, by processes such as
volatilization, crop uptake, and precipitation.
Most of the above-described factors are significant for
all types of contaminants that reach the water table, whether
they are inorganic chemical, physical, organic chemical, or
bacteriological. In some cases, certain factors do not
attenuate the contaminant, but rather redirect it. An example
is the development of a large depression cone in an agricultural
area, whereby contaminants are drawn into the area from many
directions but are effectively prohibited from leaving by the
depression.
Plumes or zones of contaminated ground water may behave
as a slow moving viscous mass, but they may also be quite
erratic, especially where influenced by recharge and/or well
pumping.
Evaluation of contaminant attenuation mechanisms in the
saturated zone requires a considerable knowledge of fluid
dynamics, geochemistry, and hydrogeologic judgement. Such an
evaluation is essential in order to adequately substantiate a
waiver demonstration. Eminently qualified professionals
known for their hydrogeologic judgement combined with experience
gained from case histories are recommended for performing
this task.
Determining Proximity of Facility to Water Supply Wells
or Surface Water
The distance from the facility to water supply wells and
surface water has a bearing on how contaminants reach
receptors. As potential transmitters of contaminanted water,
wells and surface water can expose these contaminants to the
surface environment. All types of water supply wells and
surface waters must be identified within a reasonable distance
of the facility. Wells used for drinking, irrigation or any
other purposes should be located and classified, and the type
of usage should be noted. Pumping wells are of particular
concern since they will accelerate the migration of any
contaminants present in the water, and increase the likelihood
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that contaminants will reach receptors at the surface.
Surface waters, including lakes, ponds, rivers, streams,
wetlands (swamps, marshes, bogs), springs and salt-water
bodies should also be identified.
When determining the effect of the proximity of the
facility to these water supply wells and surface waters, a
reasonable area should be considered. Many site-specific
factors affect the size that a reasonable area should be,
including:
watershed or drainage basin boundaries;
saturated zone characteristics (e.g., fractures,
solution cavities, attenuating properties);
direction of ground water flow; and
rate of ground water flow.
A situation in which the attenuating capacity of the
saturated zone is high and the rate of ground water flow is
low, may warrant a lesser area for consideration. In some
situations, (e.g., when the aquifer underlying the facility
flows into a river located several miles from the facility),
the area considered should include the river in order to
identify this major discharge point. Another factor which
might affect the size of the area for consideration is the
number of wells and surface water bodies present in the region
of the facility.
Sources of information which can provide the location of
nearby water supply wells and surface waters include:
Existing Maps. Topographic and hydrogeologic maps have been
prepared for many areas of the United States. Each map is
drawn for a certain watershed or geologic region. Among
other things, these maps show the location of wells and
surface waters. Topographic and hydrogeologic maps may be
obtained from the United States Geological Survey, State
Geological Surveys, River Basin Commissions, and some
universities. Other Federal and State agencies identified
in Table 2-1 may also have these maps.
Prepared Map of the Area. A map of the area around the
facility which indicates the location of water supply wells
and surface waters can be prepared from review of the existing
maps and other information sources previously described.
The map should cover at least the area of the drainage basin(s)
which could be affected by the facility. The map should
include all water supply wells and surface waters currently
located within the area being considered. The map should be
comprehensive and current.
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Other sources of information should be consulted to
verify and supplement the information about the location of
wells and surface waters, especially if existing maps are old
or not available. The other information sources include
local town engineers, state well-drilling records and published
reports/ surveys. Drilling records and reports might be
obtained from State Departments of Environmental Protection,
State Geological Surveys or Public Health Departments.
If the owner or operator cannot otherwise document
completeness, the map should be verified by performing a
field survey. Depending upon the geology and property
ownership in the area, the following tasks might be included
in the field survey:
contact other property owners to learn if any new
wells have been drilled (or old ones overlooked by
the previous research) and inquire about surface
waters present on their property;
drive/walk through the area (where permitted) to spot
check portions of the map; and
check state/locality files where drilling or extracting
is regulated; consult local water-well contractors.
2.6.3 Documentation
Section 265.90(c) waiver demonstrations must be in
writing, must be certified by a qualified geologist or
geotechnical engineer, and must be kept at the facility;
Section 265.90(e) waiver demonstrations must be certified by
an appropriately qualified professional (e.g., a chemist)
verifying the occurrence of the documented neutralization
reaction(s). During interim status, the written waiver
demonstration must be made available to the Regional
Administrator upon his request.
The format of the waiver demonstration under §265.90(c)
should correspond to the requirements of the regulation by
documenting the evaluations of the water balance, unsaturated
and saturated zone characteristics, and the facility's
proximity to water supply wells or surface waters, upon which
the contaminant migration potentials are estimated. The
methods used to obtain these hydrogeologic data should also
be included in the demonstration. Supplementary information
should include:
water balance calculation and how all values were
obtained;
the investigatory methods and how data were evaluated
in determining the unsaturated and saturated zone
characteristics; and
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- the site-specific map and descriptions of field
surveys used to determine the proximity of the
facility to water supply wells and surface water.
In addition to the final written waiver demonstration,
under §265.90(c) or (e), reproduceable copies of all supporting
information (e.g., reports, records of field investigations and
calculations) must be kept at the facility so that the demonstration
is soundly documented at all times.
3.0 Assessment Program and Description
The ground-water quality assessment program must be capable
of determining presence, concentrations, rate and extent of
migration of hazardous waste or hazardous waste constituents in
the ground water coming from a discharging facility. The owner
or operator is responsible for preparing and implementing an
assessment plan under §265.93(d) when there are significant
indicator parameter changes in downgradient wells. (See Section
1.3 for a discussion of the level of detail for assessment plans.)
The detection program was designed as a screening mechanism
in the determination of whether hazardous waste or hazardous
waste constituents have entered the ground water from facility
discharges. The data-evaluation procedures, including the
Student's t-test, specified in §265.93(b) were chosen to make
such determinations. In some cases the owner or operator may
believe that the Student's t-test does not provide a reliable
indication of whether hazardous waste or hazardous waste constituents
have entered ground water. (For example, he may be able to
demonstrate that the indicator parameter data collected at his
facility violate the assumptions of the Student's t-test.) An
owner or operator who believes that is the case may, in the
first phase of his assessment program, attempt to show that the
specified procedures are not appropriate for the facility. The
owner or operator must document why he believes the specified
procedures are inappropriate in his assessment plan and in the
first assessment report submitted to the Agency. As part of
this documentation the owner or operator should also submit the
analytical results for the parameters establishing ground-water
quality, listed in §265.92(b)(2).
It is also possible that the data collected might not properly
reflect the actual quality of the ground water. This would most
likely result from sampling or testing errors (e.g., sample
contamination; poorly standardized instrumentation, etc.). If
this is suspected of being the case, the owner or operator may,
as a first step in his assessment program, conduct additional
sampling and testing. In so doing, he must identify why he
believes the original data to be faulty and what steps are being
taken to prevent a reoccurrence.
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If the detection program indicates that the facility is
significantly affecting ground-water quality (see statistical
analysis discussion; Section 2.5.2), a sequential response
procedure must be followed. This procedure requires the owner
or operator to respond to possible ground-water contamination
according to the following sequence:
- Confirm sampling/analytical results by taking
additional (split) samples (§265.93(c)(2));
- Notify the Regional Administrator within 7 days of
confirmation that the facility may be affecting
ground-water quality (§265.93(d ) (1) ) ;
- Submit a specific plan for a ground-water quality
assessment program to the Regional Administrator
within 15 days of the above notification (§265.93(d ) (2 ) ),
including the following:
0 A description of the procedures that the owner or operator
will use to track the rate and extent of migration of
hazardous waste or hazardous waste constituents.
0 (Optional) an explanation of the procedures the owner
or operator will use to demonstrate that the results of
the indicator monitoring did not provide reliable evidence
that hazardous waste or hazardous waste constituents
have entered ground water and an explanation, where
possible, of more appropriate procedures for evaluating
the data.
0 (Optional) the raw data collected in the indicator
monitoring program, a general explanation of why the
owner or operator believes the results do not indicate
the presence of hazardous waste or hazardous waste
constituents in ground water, and a request for assistance
from the RA.
- Implement the assessment plan as soon as technically
feasible (§§265.93(d)(4 ) and (5));
- Submit an assessment report to the Regional Administrator
within 15 days of the first determination (§265.93(d ) (5 ) ) ;
- Follow-on actions:
0 If the assessment indicates that ground water is being
contaminated, continue the ground-water quality assessments
on a quarterly basis until final closure of the facility
(§265.93(d)(7)(i)). If contamination is first detected
during post-closure, only one assessment is required
(§265.93(d)(7)(ii)).
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oIf the assessment indicates no ground-water contam-
ination, the detection program may be reinstated and
the Regional Administrator must be so notified
(§265.93(d)(6));
If the assessment indicates no ground-water contamination
and the owner or operator believes that some set of detection
monitoring procedures other than those specified in the regu-
lations is appropriate, a demonstration of this may be
presented to the Regional Administrator. Those owners or
operators choosing to challenge the appropriateness of the
Student's t-test are encouraged to suggest an alternate method
of comparison and submit the rationale by which the method
was selected. At a minimum the owner or operator should
submit to the Regional Administrator the raw data from each
well, each replicate, each parameter (including the ground-
water quality data (§265.92(b)(2)), and each sampling
event.
Challenging the appropriateness of the Student's t-test
will not be considered just cause for delay in completing
a necessary assessment plan. Similarly, an assessment
program's implementation including identification of subsequent
action in the event contamination is confirmed, cannot be
delayed due to a challenge of the appropriateness of the Student's
t-test.
The plan for the assessment program must be certified
by a qualified geologist or geotechnical engineer who should
serve the lead role in implementing the plan. The plan must
specify:
- the number, location, and depth of wells;
- any geophysical techniques to be employed;
- sampling and analytical methods for those hazardous
wastes or hazardous waste constituents in the facility;
- evaluation procedures, including any use of previously
gathered ground-water quality information; and
- a schedule of implementation.
The plan must be based upon site-specific conditions to ensure
adequate assessment in the event that ground-water is being
contaminated. Guidance for determining the appropriate number,
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location and depth of wells is provided in the examples given
later in this Section and in Sections 2.2.3 and 2.2.4. Sampling
and analytical methods for determining the concentration of
hazardous waste and hazardous waste constituents are discussed
in Section 3.4. The evaluation procedures include use of any
previously gathered ground-water quality information (e.g.,
data collected from the detection program). Data evaluation
procedures can also be used to indicate that ground-water
quality is being affected by a source other than the facility.
The first ground-water quality assessment must be performed
as soon as technically feasible since a discharge to ground
water may be presenting a serious risk to human health and the
environment. If the evaluation of the results of the assessment
indicates no ground-water contamination, the owner or operator
may reinstate the detection program. The Regional Administrator
must be notified of this program change so he will be aware of
which program is in progress and which facilities are introducing
hazardous waste or hazardous waste contituents to ground water.
If the assessment shows that hazardous waste from the facility
has entered the ground water, assessments must be continued on a
quarterly basis. Any assessment which is initiated prior to
facility closure must be completed and reported to the Regional
Administrator.
The assessment program plan and implementation are required
if the detection program has shown that the facility may be
affecting ground-water quality. However, the owner or operator
may have chosen to use an alternate program (see §265.9U(d)),
rather than the detection program, because he assumed or knew
that the detection program would show that the facility is affecting
ground-water quality. In this case the alternate program, which
is essentially equivalent to the assessment program, must be
employed and the owner or operator was required to prepare and
implement the plan by November 19, 1981 in lieu of the detection
program.
3.1 Determining Whether Hazardous Waste or Hazardous Waste
Constituents Have Entered the Ground Water
Determining the actual presence of hazardous waste or
hazardous waste constituents in ground water due to a facility
discharge is a first necessary step after detecting via the
Student's t-test a significant result for an indicator parameter.
This determination should include, at a minimum, sampling of
those existing monitoring wells exhibiting the change in indicators.
It should reasonably include all wells likely to be in the flow
path. These samples should be analyzed for all hazardous waste
or hazardous waste constituents managed by the facility. The
data comparisons in the assessment program are not necessarily
restricted to the Student's t-test.
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If the absence of hazardous waste or hazardous waste
constituents is demonstrated, the owner or operator may wish to
challenge the use of the statistical procedures required in the
detection program. Such a challenge should include an explanation,
using indicator parameter data collected for detection monitoring,
of why the prescribed statistical procedures are not appropriate
for his facility. For example, he may contend that the background
data vary from a normal distribution to such an extent as to
violate the assumptions of the Student's t-test. The owner or
operator may submit alternate data-evaluation procedures (e.g.,
Mann-Whitney test for non-normally distributed data) with a
rationale for their use. It the Student's t-test is challenged
and if alternate procedures are suggested, the owner or operator
should submit to the Regional Administrator the raw data from
each well as discussed in Section 3.0.
3.2 Determining Rate of Contaminant Migration
Rate is primarily influenced by the hydraulic conductivity
(K) of the medium; the porosity (n) of the medium; and the
hydraulic gradient (i), a ratio of the difference in hydraulic
head and the horizontal distance between two points. This
discussion assumes that contaminants migrate at the same rate
as ground water. If the owner or operator contends that the
contaminant is migrating at a slower or faster rate than the
ground water, methods capable of quantifying such a rate must
be employed. The selected method(s) should be best suited to
the specific conditions at the facility site.
Methods for determining rate are either theoretical, such
as techniques dependent on use of a Darcy-based equation, or
they are empirical such as techniques employing tracers.
3.2.1 Use of Darcy-Based Equation
The rate at which contaminants from a facility may migrate
in the ground water can be calculated through the solution of a
modified form of the Darcy equation:
v = -Ki; where v is the average linear velocity ground water,
n
K is the hydraulic conductivity of the medium, i is the hydraulic
gradient, and n is the porosity of the medium.
In determining v", it is important to realize and account
for factors which contribute to variabilities in K, i, and n.
Hydraulic conductivity will often vary with the direction of
measurement (e.g., horizontal K is often greater than vertical
K in unfractured, stratified earth materials). In ground-
water monitoring, it is imperative to determine the flow zone(s)
with high K values because it is within these zones that the
rate of contaminant flow will likely be the greatest. These
flow patterns can greatly affect patterns of dilution and
other attenuation factors. Hydraulic gradient between the
source of contamination and the detection point (e.g., well)
can be affected by land use as well as hydrogeologic causes.
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Seasonal fluctuations of water levels may alter the gradient.
Caution should be given to determining gradient in situations
where there are perched water bodies, since comparison of
water levels from perched aquifers, whose retarding formations
are at different depths, will result in an invalid gradient
calculation. Also, gradient determination (as well as velocity)
can be influenced by nearby constant or periodic ground-water
supply pumping or clogged wells. Such influences should be
accounted for by the owner or operator when conducting an
assessment.
The hydraulic gradient (i) is the change in hydraulic
head (h) over a given distance (i.e., the vertical difference
in water level elevation (h^-h2) of two wells separated by
a horizontal distance (1) in the direction of maximum slope).
For example, the water level in Well A is five feet above
mean sea level and the level in Well B, 100 feet away and on
the same flowline, is four feet above mean sea level. The
maximum hydraulic gradient in this case is computed as follows:
hl " h2 5-4 1
= ___ = = 0.01.
1 ~TOl5100
This means that for every 100 feet horizontal distance, the
water level drops 1 foot.
An important procedure in most ground water investigations
is to identify the gradient over a specific area. The
groundwater flow net shown in Figure 2-3, can be used to
illustrate hydraulic gradient. Lines of equal "head" (equipotential
lines) are used to define slope and perpendicular flowlines
show the direction of ground-water flow between points on the
same flowline.
Water level data from at least three piezometers and/or
water table wells is necessary in establishing the maximum
hydraulic gradient (i.e., the gradient in the direction of
maximum slope). For a large facility or a facility with
complex hydrogeology, more than three piezometers will likely
be needed to establish the pattern of gradients in the area.
Porosity (total) of an earth material is its property of
containing voids or interstices and may be expressed as the
ratio of the volume of its interstices to its total volume
(Lohman, et al, 1972). A method for determining porosity is
given by Freeze and Cherry (1979, p. 237).
Effective porosity of a rock or soil refers to the amount
of interconnected pore space available for fluid transmission;
it is expressed as a percentage of the total volume occupied
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by interconnecting intersticies (Lohman, et al, 1972). When
determining n for calculating the flow rate, the Agency
recommends the use of effective porosity instead of total
porosity, since effective porosity provides a more accurate
measure of the true flow conditions. A method for determining
effective porosity is described by Fetter, 1980. Effective
porosity often varies with direction. Therefore, several
effective porosity determinations of earth material samples
in the appropriate flow zone(s) should be made so that a
range of v values can be obtained.
Hydraulic conductivity of a medium is the volume of
water at the existing kinematic viscosity that will move in a
unit time under a unit hydraulic gradient through a unit area
measured at right angles to the direction of flow (Lohman, et
al; 1972). It depends primarily on the nature of the pore
space (i.e., continuity of pore inter-connections), the type
of liquid occupying it, and the strength of the gravitational
field.
Hydraulic conductivity can be determined by laboratory
and field methods. The Agency recommends that the owner or
operator employ field methods whenever possible since they
test the aquifer materials under in situ conditions. In
general, field methods can usually provide more representative
values than laboratory methods because they test a larger
volume of material, thus integrating the effects of macrostructure
and heterogeneities. Laboratory tests may be useful for
comparison purposes with field test results. For a range of
K values for different earth materials, see Freeze and Cherry
(1979, p. 29).
Laboratory Methods for Determining K
Permeameters
The saturated hydraulic conductivity of an earth material
sample can be measured in the laboratory using a constant-head
permeameter or a falling-head permeameter. (For a more
complete discussion of the apparatus and procedures, see
American Society of Testing Materials; 1967 and 1978; and
Freeze and Cherry, 1979). Klute (1965) believes that the
constant-head system is better suited to samples with
conductivities greater than 0.01 cm/min (or 1.66 x 10~4
cm/sec) while the falling-head system is more appropriate for
samples with lower conductivity. The methods described above
are applicable to common granular aquifer materials and not
clayey materials. These tests provide more accurate K values
when the sample is undisturbed. The heterogeneity common in
earth materials will be reflected in the various K values
determined for different samples. It should be recognized
that permeameter tests provide K values from only sampled
parts of an aquifer and may not be representative of the
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entire aquifer. Also, disturbance of samples during collection
and handling at the laboratory can lead to inaccurate
determinations.
Grain - Size Analysis
Grain-size analysis (as developed by Hazen, 1911) involves
sieving of granular earth material in the fine sand to gravel
range to establish the proportions of the various grain-size
diameters in the sample. A representative grain-size diameter
(e.g., average or median) is chosen and used in established
mathematical formulae to estimate saturated hydraulic conductivity
(Freeze and Cherry, 1979; pp. 350-352). Use of the median
grain-size diameter for such estimates is more powerful since
it considers the spread of the various grain-size diameters.
In concert with mathematical calculations, curves have been
developed from which K values may be read (Masch and Denny,
1966).
Grain-size analysis for estimating K is best applied to
homogeneous, unconsolidated aquifers, especially when undisturbed
earth material samples are obtained. Sample locations for
grain-size analysis should be carefully selected since only
small sample volumes are used to give an estimate of K for a
larger portion of an aquifer. The greater the heterogeneity
of grain-size distributions in an aquifer, the less precise is
this method of determining K. This technique of estimating K
is the least accurate of the techniques described in this
document.
Field Methods for Determining K (For further details, see
Freeze & Cherry, 1979, pp. 339-350).
Piezometer Tests
In situ K may be determined in tests using a single
piezometer. These tests involve the sudden introduction or
removal of a known volume of water to or from a piezometer.
Observation of the recovery of the water level in the piezometer
is then made. "Bail tests" involve removal of water, whereas
"slug tests" involve adding of water. Interpretation of
water level versus time data is dependent on the test
configuration used. Methods described by Freeze and Cherry
(1979), along with related mathematics, include one method
for a point piezometer and another for a confined aquifer.
A major limitation on slug and bail tests is their heavy
dependence on a high-quality piezometer intake. Corroded or
clogged well points or screens lead to highly inaccurate
calculated K values. Also, development of the piezometer by
surging or backwashing prior to testing may reflect the
increased K values attributed to the artificially induced
gravel pack around the intake.
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Piezometer tests are not useful for determining K if
water level recovery is too rapid to allow measurement,
especially if the volume of water added or removed is small.
Accurate piezometer tests provide in situ K values representative
only of the small volume of porous media in the immediate
vicinity of the piezometer tip. The greater the number of
piezometers used, the better the characterization of the K
distribution within the aquifer.
Pumping Tests
Pumping tests (also properly called aquifer tests)
provide in situ measurements of aquifer coefficients (e.g.,
transmissivity) which can be used to calculate K over a large
aquifer volume. K is computed as follows:
K = T/b;
where T is the transmissivity of the aquifer, and b is the
saturated thickness of the aquifer. Pumping tests to determine
K generally consist of:
the drilling of a test well with one or more
observational piezometers;
- a pumping test to determine the value of T; and
calculation of K.
Methodology for examining pumping test data from unconfined
and confined aquifers and references for pumping test
configurations are discussed by Freeze and Cherry (1979, pp.
343-349). A disadvantage of pumping test data can be attributed
to the nonuniqueness of its interpretation. Predicting the
effects of any proposed pumping test configuration is highly
dependent on a clear understanding of the geology involved.
Even if pumping test data matches a theoretical curve, it
does not prove that the aquifer fits the assumptions of that
curve (e.g., leakage effects if present, but not accounted
for, could lead to an erroneous K value for the aquifer of
interest). These methods generally test larger portions of
aquifers than piezometer tests. The large possibility for
non-uniqueness in interpretation, problems involved in pumping
contaminated fluids, and the expense of conducting such tests
generally preclude their use in problems of contaminant
hydrogeology.
Example of the Use of the Darcy-Based Equation
The following information was gathered for an aquifer
comprised mainly of sand:
K = 10-3 cm/s
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i = .01
n = .30.
Using the equation:
v = - Ki/n,
v is calculated to be 3.3 x 10~^ cm/s or 10.6 m/yr.
Limitations on the Use of the Darcy-Based Equation
The Darcy-based equation used in the preceding example
applies to many, but not all, ground-water flow situations.
For flow through granular materials there are at least two
situations where valid use of this equation is in question
(for more details, see Freeze and Cherry, 1979, pp. 72-75).
The first deals with flow through sediments with low K values
under very low gradients and the second deals with flow
through sediments with very high K values. This suggests
that the modified form of Darcy's equation may have both a
lower and upper limit to its range of validity. Darcian-derived
flow rates are rarely exceeded in nonindurated (i.e., not
hardened) rocks and granular materials. However, Darcian
flow rates are commonly exceeded in such important rock
formations as karstic limestones and dolomites, and cavernous
volcanics, Where the Darcy-based equation cannot be validly
used to determine flow rate, another method (e.g., use of
tracers) should be employed.
3.2.2 Use of Tracers for Determining Flow Rate
The advantage of using tracers is obvious. If the test
is large enough, and for a long enough time, the actual flow
path is measured rather than theoretical surrogates estimated.
Generally, however, the required time will not be available.
The following discussion of tracers is based mainly on
Freeze and Cherry (1979, pp. 427-430), who also provide
additional references on tracers. The use of a tracer is a
direct method for determining flow velocity. After introducing
a tracer at one point in the flow field and observing its
arrival at other points (and after making adjustments for the
effect of dispersion), velocity can be computed from the
travel time and distance data (i.e., v = d/t). Several types
of nonradioactive and radioactive tracers have been used,
including simple tracers such as salt (NaCl or CaCl2)/ which
can be monitored by measurement of electrical conductance, to
radioisotopes such as 3H, 131jf 29Br-f an<3 51cr_EDTA (an
organic complex with 51cr), which can be monitored using
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radioactive detectors. Radioisotopes are subject to government
licensing requirements for their use and can be hazardous
when used by careless workers. Fluorescent dyes (fluoroscein
and rhodamine compounds), used by many investigators, have
sometimes yielded adequate results based on visual detection.
When necessary, dye concentrations can also be measured
quantitatively to very low concentrations. Recent work
suggests that Freon (C13CF) may be a very good artificial
tracer, since it is nonreactive with geologic materials and
can be used in extremely small concentrations that are not
harmful to public waters.
Factors which should be used in selecting and using
tracers include:
ease of detection, uniqueness;
solubility in ground water (ideally moves with water
at same velocity, including direction);
- stability in ground water for desired length of time;
- type of emitted radiation, if any;
- background levels of tracer or interfering substances
in ground water;
- chemical reactions among water, tracer and contaminant;
and
- interactions of tracer with earth materials (e.g.,
filtration, adsorption).
The advantage of properly performed tracer studies is
that they are indisputable. The major disadvantages of the
direct tracer method include:
because ground water moves slowly, long periods of
time are normally required for tracers to move
representative, meaningful distances through the flow
system;
variegated hydrogeological settings require numerous
observation points (e.g., piezometers, wells, or
other sampling devices) to adequately monitor the
passage of the tracer through the portion of the flow
field under investigation;
if small aquifer segments are studied in order to
overcome time restraints, there is less assurance
that a representative sample of the flow field is
tested; and
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because of the common heterogeneity of earth materials
encountered, the flow field may be significantly
distorted by the measuring devices.
Due to the above disadvantages, tracer experiments of
this type commonly require considerable effort over extended
time periods. One limited-objective technique that avoids
some of these disadvantages is known as the "borehole dilution"
or "point-dilution" method. This test can be performed in
relatively short periods of time in a single well or piezometer
and provides an estimate of the hori,atpsr slhiage flow velocity
of the ground water in the formation near the well screen. In
this test, a tracer is quickly introduced into a segment of
a well screen isolated by packers and is then subjected to
continual mixing as lateral ground-water flow gradually removes
the tracer from the well bore. The combined effect of ground-
water through-flow and mixing within the isolated well segment
produces a dilution versus time relation from which the
average horizontal velocity of ground water in the formation
beyond the sand or gravel pack, but close to the well screen,
is computed. This method is best suited for velocity
determination in steady-state lateral flow regimes.
Borehole dilution tests can be performed at various
intervals within a well screen to identify zones of highest
ground-water velocity. These zones are of prime interest
since contaminants can move through them at velocities much
higher than in other parts of the system. Identification of
such high-velocity zones, which may occur in only a thin
segment of the aquifer system, will aid in the design of a
more efficient monitoring network.
Most borehole dilution tests described in the literature
employed radioactive tracers. However, the recent advent of
commercially available electrodes for use with portable pH
meters for rapid downhole measurement of Cl~ or P~ has made
it feasible to conduct these tests with readily available
tracers in a more convenient manner. An even simpler approach
uses salt as the tracer with down-hole measurement of electrical
conductance as the salt is flushed from the well screen.
3.3 Determining Extent of Contamination
This section describes methods to determine the extent
of contamination. The owner or operator must determine which
method(s) will be best suited to the hydrogeologic controls
at his specific site.
"Extent" refers to the spatial distribution (length,
width and depth) of hazardous wastes or hazardous waste
constituents within the ground water environment. When a
facility discharges into the subsurface, mobile constituents
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will migrate downward to the water table where they can
migrate within the ground-water system. Contaminants in
ground water often tend to travel as a "slug" or "plume", the
geometry of which depends on local heterogeneities in the
subsurface and contaminant properties. Ground-water
contamination patterns (i.e., plume configurations) are most
predictable under uniform flow conditions; however, these
conditions are rarely encountered in the field. A comprehensive
investigation is needed to delineate the characteristic shape
or configuration of the contaminant plume(s).
Due to the variety of waste types and the complex
hydrogeologic factors at many facility sites (e.g., perched
water tables, local supply well pumping effects, etc.), a
field investigation is the most effective method for determining
the extent of contaminant migration. Several direct and
indirect techniques can be utilized individually or in
combination to detect and verify the configuration (i.e.,
extent) of a contaminant plume. Data from field investigations
should be translated to site base maps and subsurface cross
sections for correlation and interpretation of the results
(see Section 2.2.2 for discussions of base maps and cross-
sections). Information from a detailed field investigation
should provide a graphic representation of the boundary or
extent of the contaminated zone (e.g., by mapping isopleths
of contaminant concentrations). Choice of investigative
techniques should be based upon the kind and amount of waste(s)
managed at the facility, the hydrogeology of the site, the
size of the facility, etc. Some of the more versatile and
reliable assessment techniques include:
Indirect Techniques (i.e., remote sensing)
- aerial photography;
electromagnetic conductivity;
- electrical resistivity;
- specific conductance-temperature probe; and
- geophysical logging;
Direct Techniques include:
- boreholes with formation sampling; and
- water sampling from monitoring wells.
Not all of the above techniques need be applied to
determine the extent of contaminant migration at any one
site. The selection of the most effective technique(s) for
a particular situation can be determined by the geologist or
geotechnical engineer supervising the investigation. Although,
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each technique can aid in detecting contaminants in the
subsurface, not every technique (especially indirect) will
work satisfactorily at every site. Often, techniques work
best in conjunction with one another. In some cases, it may
be necessary to conduct preliminary field testing to determine
the suitability of a specific technique at a given site.
Information from boreholes and monitoring wells is
necessary in a ground-water quality assessment. Data obtained
from other methods is often useful in supplementing the
information from and determining locations of boreholes and
monitoring wells. Indirect techniques can be used to reduce
costs by limiting the total number of boreholes and monitoring
wells necessary to define the plume.
3.3.1 Indirect Techniques
Aerial Photography
Aerial photography can serve as an initial detection
mechanism to aid in determining the extent of contamination.
This method provides wide surficial coverage, but is limited
by the relatively poor resolution of local details. Photographic
interpretation provides no subsurface data other than that
which is implied, but may indicate surface responses to
subsurface conditions (Benson and Glaccum, 1979). For example,
vegetative stress may indicate leachate and gas migration
where the water table is shallow or in discharge areas. The
investigator may obtain some information on the extent of
contamination by outlining the boundary of stressed vegetation.
Different types of aerial photography (e.g., black and white,
normal color or infrared) can detect vegetation stress which
may not be evident during a field inspection. Infrared
photography can be useful in determining the early effects of
less advanced stresses.
Geologic features (e.g., bedrock fractures, fault zones,
etc.) that affect ground-water flow patterns can be identified
from aerial photos. Fractures at shallow depths in consolidated
rock can serve as conduits for rapid infiltration of surface
runoff. Regions where bedrock outcrops at the surface, or is
overlain only by thin alluvium, are particularly susceptible
to contamination. Aerial photos provide a means to detect
potential avenues of contamination in areas characterized by
outcropping fractured bedrock.
Contamination of surface water bodies may be detected by
discoloration or shading in aerial photography. This
information may enable the investigator to make a quick,
rough assessment of the extent of potential contamination of
such surface water.
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Land surface elevation determinations and contour maps
(photogrammetry) can be compiled from information in aerial
photographs and ground-water flow direction in shallow systems
can be estimated using this information.
Federal and other offices serve as repositories of aerial
photographs especially for historical or pre-discharge
imagery. Photos may be purchased or information on photos
obtained from the sources identified in Section 2.2.2.
It may be necessary to retain a contractor to fly aerial
surveys of a particular area to achieve the timeliness and
level of detail desired in the area to be assessed. Enlargements
of photos can be made, but at a loss of resolution.
Conclusions drawn from the interpretation of aerial
photographs should be substantiated by surface inspection.
Aerial photography serves primarily as an aid for designing a
more detailed assessment strategy that should include other
field methods.
Advantages and Limitations of Aerial Photography
Advantages include:
- it is relatively inexpensive;
- it is an easily accessible technique which provides
information on a large area;
it may indicate the effects of the contamination as
well; and
it serves as a good preliminary step in evaluating an
affected area.
Limitations include:
it provides relatively poor resolution of local
details; and
it offers no direct information on subsurface
characteristics.
Example of the Use of Aerial Photography
Low levels of some organic chemicals (trichlor^Pthylene,
toluene and benezene) were detected in several farmers wells
in a sparsely developed, limestone valley. The suspected
source of the contaminants was a waste impoundment which was
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located approximately 1/4 mile away. There were no detailed
maps of the area; however, aerial photos taken by the U.S.
Soil Conservation Service in the winter of 1957 were available
in stereo pairs. It was apparent from the photos that the
shallow limestone bedrock had a very definite control on the
topography and other surface features. There were numerous
springs, sink holes and streams in the area that seemed to be
aligned in a general rectangular pattern.
Aerial photography was used to obtain more recent color
photos on a larger scale plus false color infra red (IR).
The IR photos were helpful in identifying springs and other
points of ground-water discharges. Areas of stressed vegetation
were identified. Two ponds and a drainage ditch in the area
also appeared to be a darker tone of color than other ponds
in the vicinity, indicating possible contaminant migration.
From the larger scale aerial photos, pertinent information
was added to a base map. The impoundment, contaminated wells
and wells yet to be sampled were located on the map. Also
included were springs, ponds, sink holes, streams, stressed
vegetation areas, stained drainage ditches and other areas of
suspected contamination. The above observations required
verification by field inspection, including groundwater sampling
and analysis. After employing these techniques, the confirmed
contaminated areas were plotted on the base map. The map
indicated that the extent of the contaminated zone reflected
the same general rectangular pattern described in the aerial
photos. The contaminants were most likely migrating through
solution cavities that were developed along joints in the
limestone bedrock.
Electromagnetic Conductivity
Electromagnetic conductivity (EM) is a geophysical
technique capable of obtaining data on subsurface conditions.
EM can detect subsurface features capable of conducting an
electric current and is especially useful in defining shallow
ground-water zones characterized by high dissolved solids
(e.g.contamination plumes).
EM operates in the following manner: The transmitting
coil generates alternating magnetic fields which result in
the flow of alternating currents that are detected by the
receiving coil. The intensity of alternating currents is
greater in areas of high conductivity and, conversely, lower
in areas of low conductivity (Griffiths and King, 1966).
Electromagnetic conductive properties are a function of the
basic soil/rock matrix (e.g., grain size, porosity, and
permeability) and also of the fluids which permeate the
matrix. Contamination often increases the free ionic content
of the ground water, hence increasing its conductivity. EM
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techniques comprise a composite measure of these properties
which, like aerial photography, supplement other data in a
contamination assessment (Benson and Glaccum, 1979, 1980).
EM equipment does not require ground connections, is
very mobile and can be operated over a variety of terrains.
The data is recorded in a series of profiles, which indicate
shape and trends of anomalous subsurface conditions.
Advantages and Limitations of EM
Advantages include:
instrumentation is fairly easy to operate;
surveys can be completed in a relatively short
period of time since ground connections are not
necessary;
- it can provide a quick preliminary assessment of
shallow contamination; and
- it is relatively inexpensive.
Limitations include:
data is limited to shallow depths;
instrumentation is sensitive to interference from
conducting bodies at or above the surface (e.g.,
transmission wires);
it provides qualitative information which requires
substantiation by direct techniques; and
results must be compared to background information,
including local geology and ambient ground-water
chemistry.
Example of the Use of EM
Monitoring wells detected a discharge from an impoundment
containing pickeling liquors in a valley comprised of alluvial
deposits. Because a municipal well field was nearby, the
ground-water around the impoundment was carefully monitored.
Due to the presence of highly permeable, shallow, but
discontinuous channel deposits, there was concern that the
contaminants would be difficult to trace along an irregular
ground-water flow pathway.
EM was selected as an assessment method because the
contaminant was highly conductive within the shallow channel
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sand deposits. Numerous traverses of the area downgradient
from the impoundment were made in order to account for the
variability of the subsurface deposits. The responses of the
equipment were continually recorded on a portable strip chart
recorder as shown on Figure 3-1. Station points (i.e.,
flagged stakes) surveyed in for field control provided quick
references for locations, and facilitated the transfer of
data to a base map of the area. Interpretation of the results
involved primarily the recognition of significant anomalies,
the outline of which indicated the extent of the contaminated
zone. The extent of migration was verified by drilling
additional boreholes with monitoring well sampling and
analysis.
Electrical Resistivity
Owners and operators are encouraged to explore the
utility of electrical resistivity (ER) in defining the plume
of contamination. The procedure is based on transmission of
an electric current into the subsurface materials and
measurement of the materials' resistance to the flow of that
current. Low resistivity values can indicate a concentration
of free or mobile ions, such as are often found in contaminated
ground water. ER is particularly useful for facilities
receiving inorganic wastes at sites characterized by homogeneous
geological conditions.
Resistivity surveys at established plumes are in general
the cheapest and most reliable technique for defining the
edge of the plume and the rate of migration. Established
grids re-surveyed quarterly with knowledge of water table
fluctuations can provide a convincing demonstration of these
two factors.
The most commonly used approach in conducting an ER
survey utilizes the Wenner electrode configuration in which
four electrodes (copper coated steel rods) are pushed or
hammered several inches into the ground along a straight
line. The electrodes are spaced at equal intervals ("A-
spacings") determined by the depth of interest. Under uniform
conditions, the A-spacing is roughly equivalent to
the depth of interest. An electric current (I) from a battery
is applied by conduction into the ground through the outer
two electrodes. The current distributes itself throughout
the volume of earth materials in between. The resulting
voltage drop (V) is measured across the inner two electrodes.
The "apparent resistivity", Ra, is then determined for graphing
purposes. Some ER instruments can automatically compute the
apparent resistivity; otherwise it can be computed as follows:
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Figure 3-1
Electromagnetic Conductivit
sponses Recorded on a Portable
Strip Chart Recorder '
f.
LJ
o:
<
CO
§
CO
to
o
cr
o:
o
UJ
>
fc
h-
O
O
O
o
o
-------
Ra = 2 A V/I;
where Ra = apparent resistivity;
A = spacing between electrodes;
V = voltage; and
I = electric current.
Apparent resistivity values of subsurface materials
obtained by ER measurements made at the surface are the
composite or average values of the materials through which
the electric current travels. Irregularities (e.g., variations
in composition of earth materials) in resistivity below the
surface alter the pattern of current distribution of potential
differences.
In order to conduct an ER survey, control points,
baselines and/or grids should be established by measuring,
staking and flagging benchmarks at appropriate intervals.
The depth of interest can be determined from vertical soundings,
from which the lateral extent of the contaminated ground-
water body can then be estimated by constant-depth surveying.
ER values are plotted on a grid or base map and then contours
can be drawn between points of equal apparent resistivity.
There is no theoretical limit to the depth of an electrical
resistivity investigation. However, at depths exceeding 100-
200 feet results become more difficult to interpret (e.g.,
small anomalies are masked) because of the large volume of
earth material through which the electric current must flow.
The success of ER in contamination assessment is also dependent
on the particular contaminant's ability to affect detectable
decreases in resistivity (i.e., not all contaminants cause a
decrease in resistivity).
ER surveys can lower drilling costs (see Figure 3-2).
Wells drilled only around the perimeter of a contaminant
plume are by themselves inadequate in defining the extent of
the plume as it contracts and expands. ER can be used to
supplement the information from wells to aid in monitoring
changes in plume configuration at relatively low cost.
Advantages and Limitations of ER
Advantages include:
it aids in defining subsurface geology and contamination;
- a survey can be re-run periodically to provide updated
monitoring data;
it is relatively inexpensive; and
it aids considerably in defining the application of
direct techniques (e.g., boreholes and monitoring wells).
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jVigure 3-2
Electrical Resistivity
(A.)
I
IN THIS HYPOTHETICAL
SITUATION, ELEVEN
MONITORING WELLS
ARE INITIALLY
INSTALLED.
Drilling Costs
CONTAMINATION
SOURCE
(B.)
THIRTY MORE
WELLS ARE
INSTALLED
AFTER TWO
CHANGES IN •
PLUME
CONFIGURATION.
CONTAMINATION
SOURCE
(C.)
AN ALTERNATIVE TO
A and 3 ABOVE»
INITIALLY, TriREE
MONITORINS WELL
PLUS RESISTIVITY.
AFTER TWO ,
CHANGES IN '
PLUME CON-
FIGURATION, TEN
MONITORING
WELLS PLUS '\
RESISTIVITY.
_^^.,
',&Z^.-'i'^QHtaiN&C:^^
CONTAMINATION
SOURCE
FIRST GROUP OF
MONITORING WELLS'
SECOND OROUP OF
-MONITORIN9 WELLS
A THIRD OROUP OF
m MONITORIN3 WELLS
RESISTIVITY
MEASURING POINT
127
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Limitations include:
the greater the depth of interest, the less accurate
are interpretations concerning contaminant migration;
variations in geology (e.g., clay lenses) can mask
the effects attributable to contamination;
not all contaminants result in lower EF values;
background data on natural quality of ground water and
geology is a necessary prerequisite; and
potential interferences due to conducting bodies (e.g.
metal pipes and fences) at or below the land surface
can hinder interpretation of data.
Example of the Use of ER
Leachate from a landfill situated in a coastal plain was
determined to be contaminating several wells in the vicinity.
The contaminants consisted primarily of arsenic and various
heavy metals.
The detection of leachate by ER is a function of the
leachate's electrolytic properties. Many leachates are high
in dissolved ions and are considered good conductors (or have
low resistivity) when compared to background levels of the
natural eirth materials. For this reason and because of the
relatively shallow depth of interest (i.e., depth to water
table < 100 feet), ER was selected as a technique for
determining the extent of contaminant migration.
In order to estimate the depths of investigation and
thus the electrode A-spacing, ER soundings (i.e., multi-depth
readings) were conducted at various locations downgradient
from the landfill. Once the most effective A-spacing was
determined, baselines were established and the entire area
was profiled (i.e., constant A-spacing was used) with
approximately 200 electrical resistivity measurements. The
apparent resistivity values obtained from these measurements
were plotted on a base map of the area and compared to other
sources of information. Contours of these values indicated
the areal extent of the contaminated zone (see Figure 3-3).
This information provided a basis for locating sites for
boreholes and monitoring wells for verifying the results of
the ER survey. The boreholes and wells were also needed to
determine the depth component of extent, which could not be
determined adequately by indirect techniques.
For further information on ER concerning equipment,
procedures,data interpretation and case studies; see Roux
(1978).
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* 1 i
* f - r ;
a S * £ * *
° 5 * 3 5 "•
5" ~? * 5 * «
! III!
Figure 3-3
Isoresistivity~Map of
Contaminated Zone
§•
tc
Q
o
§5o
129
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Specific Conductance and Temperature Probes
Since a facility discharge (i.e., leachate) may have
substantially higher temperature and specific conductance
than natural ground water, the presence of such leachate can
be detected by these two characteristics. Measurements of
these characteristics can be made by lowering a remote sensing
device into a well and recording results from surface
instrumentation. In areas with a high water table, however,
the measurements can be made without installing a well. The
method involves the use of a self-contained conductance-
temperature probe which can be pushed into soft ground or
inserted into a hand-augered hole to reach the saturated
zone. (For further information on this method see Fenn, et
al, 1977, pp 119-121.)
Geophysical Borehole Logging
Geophysical logging methods can greatly enhance the
amount of information gained from a borehole. Each method is
designed to operate in specific borehole conditions, involves
lowering a sensing device into the borehole and can be
interpreted to determine lithology, geometry, resistivity,
bulk density, porosity, permeability, moisture content and to
define the source, movement, chemical and physical
characteristics of ground water. Logs produced by geophysical
methods include: spontaneous potential, normal resistivity,
natural gamma, gamma-gamma, caliper, temperature and fluid
conductivity. Specific functions of these logs are discussed
by Scalf et al.(1981; pp. 34-36) and Keys and MacCary (1971).
Geophysical well logging is applicable only to those
subsurface investigations which include test drilling and is
therefore not an independent tool. Interpretation of well
logs is most reliable when several techniques are used and
the resulting logs are placed side by side to allow
crosschecking. Such cross-checking with the driller's/geologist's
log is also recommended. Detailed interpretation of well
logs can be used to evaluate ground-water characteristics.
Correlation is often difficult and should be done by a specialist.
Advantages and Limitations of Geophysical Borehole Logging
Advantages include:
• - it can determine formation changes which aid in
determining contamination pathways; and
- it can aid in locating the vertical limits of a plume
of contamination through definition of ground-water
characteristics.
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Limitations include:
- it necessitates the use of special, relatively
expensive equipment and trained operators;
its requires drilling of boreholes; and
results are qualitative (i.e., concentrations of
specific contaminants are not determined).
3.3.2 Direct Techniques
Direct assessment techniques involve collection,
observation and analysis of earth materials, including water
samples.
Direct methods (e.g., boreholes and monitoring wells)
which entail excavation or drilling necessitate careful and
prompt recording of all data, such as:
location of the borehole on a base map;
assignment of an identification number;
elevation of the ground surface (accurately determined
elevation of the top of casing of the well; - drilling
method;
- hole diameter;
- depth of samples;
- method of subsurface sample collection;
description of field materials; - if borehole is
completed as a well — length, diameter and type of
casing;
- length, diameter, type and setting of screen, if
used;
- gravel pack (size), backfill and grouting
materials and related depths;
- date, time, weather conditions; and
name of supervising geologist.
Boreholes and Monitoring Wells
Purposes for drilling boreholes are discussed in
Section 2.2.1. Locations and depths of boreholes and monitoring
wells may be based, in part, on the findings of indirect
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methods (e.g., ER and EM) and spaced so as to provide sufficient
coverage of the areas most likely to be affected by contaminants.
Since results of indirect methods are not conclusive, the
initial boreholes should be drilled close to the probable
source of contamination. Subsequent boreholes should be
located radially outward increasing with distance until the
contaminant front is delineated.
Figure 3-4 illustrates an example of a systematic approach
for spacing which may be used in determining locations for
boreholes and monitoring wells when information on the
distribution of contaminants at a given site is limited.
(For further information on well location, number, design and
installation, see Sections 2.2 and 2.3). If well M-3 is
found to be contaminated, it may be appropriate to drill a
series of wells downgradient of the facility along a line
parallel to the direction of ground-water flow. For example,
well A-l is drilled at a location twice the distance between
M-3 and the facility. If this well is found to be contaminated,
a second well (A-2) is drilled along the same axis twice the
distance between A-l and the facility, and so on, always
doubling the spacing between wells until contaminants are not
detected in the most distant well. A-4 is then drilled
halfway between A-3 (clean) and A-2 (contaminated), A-5
between A-3 (clean) and A-4 (contaminated), etc., until the
distance the plume has traveled has been located with reasonable
accuracy.
Likewise, in delineating the width of a plume, on a line
perpendicular to the direction of ground-water flow, through
well A-2 (thought to be near the center of the plume), well B-
1 is drilled at a distance from A-2 equal to that between A-2
and the facility. If this well is free of contaminants, well
B-2 is drilled halfway between B-l and A-2, B-3 between A-2
and B-2 and so on. The same procedure is used in locating
wells between A-2 and C-l. This example approach defines the
extent of the plume with a minimum of drilling effort and
expense, since wells are clustered close to the boundaries of
the contaminated area. These wells can be used to detect
any further expansion or contraction of the plume. Plume
thickness should also be determined by using methods such as
well clustering or employing wells which enable discreet,
multiple depth sampling within a single borehole.
Boreholes and monitoring wells can be installed by a
variety of drilling techniques (see Section 2.3.2). Regardless
of the type of drilling method selected, extreme care must be
taken to insure against creating a conduit for contaminants
to flow from contaminated to uncontaminated aquifers or
aquifer zones. The geologist or geotechnical engineer
directing the assessment should work with the driller to
prevent this from occurring.
132
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Figure 3-4
Borehole/
mitonng Well
Plan for Determining Extent
of Contamination
133
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Boreholes, completed as piezometers and/or monitoring
wells, can provide information on composition of earth material
formations, contaminant concentrations, water elevations,
flow directions, etc. (see Sections 2.2 and 2.3). Drilling
data should be recorded in a format which allows comparison
with published geological maps and available well-log records.
Example of the Use of Boreholes and Monitoring Wells
Contaminants from an impoundment are known to be migrating
toward a municipal well field in which wells are screened at
various depths (100 ft. to 500 ft.) within an alluvial fan
deposit. Trace levels of contaminants have been detected in a
few scattered monitoring wells, but the distribution of
contaminants within the multi-level aquifer is unknown due to
the complexity of the subsurface flow system.
To determine the extent of contamination at various
depths within this multi-level aquifer, boreholes were drilled
to obtain formation samples and to perform geophysical
logging. Monitoring wells were installed in some of the
boreholes and sampled for the indicator parameters, described
in Section 2.4.5, to screen for more specific contaminants.
Detecting low levels of contaminants requires special care
in drilling and obtaining representative solid and water
samples. The boreholes were fully cased so as to reduce caving
and contamination of samples by near-surface materials. The
drilling fluid consisted only of pure bentonite (no additives)
and clean tap water. A non-reactive tracer was added so that
the presence of drilling fluid within a sample could be
detected readily. Also the drilling fluid was periodically
tested for contamination.
Split spoon samples were obtained at least every five
feet. Geophysical logging aided in determining the depths of
the contaminated zones and for correlating strata between
boreholes.In selecting the optimum intake location, consideration
was given to the spatial distibution of the suspected
contaminant zones and the intake locations in surrounding
wells. The objective was to assure as complete a coverage as
possible of the contaminant front.
Monitoring for the indicator parameters also provided
valuable information concerning the extent of contamination
within this ground-water system. Specific conductance and
pH were measured in the field by lowering sensing devices
down wells or immersing these devices in samples of water
obtained at the site.
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Safety
Safety is an important consideration when using field
methods to define contamination. Appropriate protective
clothing, such as gloves and boots, should be worn. if the
contaminants are suspected of causing respiratory damage,
special breathing apparatus (e.g., ultra-twin respirators or
self contained breathing apparatus) will be needed. When
toxic contaminants are suspected, field testing should be
performed only by personnel trained to work with hazardous
waste and samples should be analyzed by a qualified laboratory.
3.4 Determining Concentrations of Contaminants
The term "concentration" in this discussion refers to
the mass of solute (i.e., hazardous waste or hazardous waste
constituent) present in a known volume of ground water.
Concentration is commonly expressed in milligrams per liter
(mg/1) or micrograms per liter ( g/1). Accurate determination
of the concentration of hazardous waste or hazardous waste
constituents present at each sampling location provides the
owner or operator and the Regional Administrator with
information necessary to evaluate the severity of contamination
in the ground water.
Sampling points (e.g., monitoring wells) should be
located in relation to defining the contaminant plume(s).
Information on "uncontaminated" ground-water quality upgradient
of the facility is useful in determining the severity of any
downgradient contamination and can also help to account for
any upgradient contamination sources. Contaminant concentrations
within the plume will vary (e.g., due to dilution and
attenuation effects, there may be gradation in contaminant
concentrations from high levels nearest the facility through
the middle of the plume, to lower levels near the outer limits
of the plume). Therefore, the owner or operator should obtain
ground-water samples which will reveal a range of concentrations
that exist within the plume. The concentration values obtained
from these samples should be evaluated in the context of
their location within the plume and their relationship to any
background and other sample values obtained. Concentration
isopleth maps should be prepared for parameters of concern.
Such maps should depict the lateral and vertical extent of
plume migration.
The following discussions present general procedures and
methods for obtaining accurate concentration values for
hazardous waste or hazardous waste constituents in ground
water underlying a facility. Scenarios for "simple cases"
and "complex cases" are presented.
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3.4.1 Simple Case Determinations
In a simple case, accurate information on the identity,
composition, and location of past and present wastes at the
facility is readily available through existing records. This
information is necessary for determining concentrations since
knowledge of the types of waste will aid in selecting specific
compounds and elements to be analyzed for in groundwater
samples.
Compile a List of Potential Contaminants
The first step in determining concentrations is to
compile a list of those hazardous wastes or hazardous waste
constituents to be analyzed in ground-water samples. "Hazardous
waste constituent", as defined in 40 CFR §260.10(a)(8) means
a constituent which caused the Administrator to list the
hazardous waste in 40 CFR Part 261, Subpart D, or a constituent
listed in Table 1 of 40 CFR §261.24. In addition to wastes
managed in current operations, wastes handled in the past
should be included in the sampling and analysis scheme because
of the potential persistence of ground-water contamination
over long time periods. Older wastes may have migrated
through past or recent facility discharges.
The types of information which should be used in compiling
the list of hazardous wastes and hazardous waste constituents
include:
General Waste Analysis — The facility owner or operator
is required by 40 CFR 265.13 to obtain a detailed chemical
and physical analysis of a representative sample of the
waste. This analysis must contain all the information
which must be known to treat, store or dispose of the
waste. The analysis may include data developed under 40
CFR Part 261 of the RCRA regulations for identifying
hazardous wastes, and existing published or documented
data on the hazardous waste or on waste generated from
similar processes. Applicable wastes include those
identified according to characteristics in 40 CFR Part
261, Subpart C and those listed in 40 CFR Part 261, Subpart
D. A detailed analysis will identify many different waste
properties (e.g., pH, density and viscosity), including
the composition of the waste and relative quantity of each
component. The extent to which the waste composition will
be described depends upon the complexity of the waste and
the information needed for proper waste management.
Generator Manifests — The manifest required under 40 CFR
Part 262 to accompany the shipment of hazardous waste
contains information from the waste generator describing
the wastes and the quantities of eaqh waste by weight or
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volume. The facility owner or operator should have obtained
this manifest information from the waste transporter upon
acceptance of the waste at his facility.
Facility Operating Records — Operating records maintained
at the facility may provide additional information on
waste composition and the identity of hazardous substances
that should be analyzed for, especially for wastes handled
in the past. When reviewing these records, the owner or
operator should pay particular attention to data on the
identity of the waste, the management processes used, the
identity of material recycled or recovered, and the identity
of generators from which waste was accepted. These types
of information will aid the owner or operator in determining
what hazardous wastes have been or are being managed at
the facility.
Additional information sources — For those periods in
which facility operating or other records are incomplete,
"historical records" may provide supplemental information.
Records such as old aerial photographs and records of
previous ownership of the facility may be used to deduce
generally what types of wastes have been managed in the
past and where they were treated, stored and/or disposed
of. In some cases, interviews with former employees may be
helpful.
Sampling Procedures
The next step in determining concentrations is to select
and implement sampling procedures appropriate for the substances
on the compiled list. In general, the sampling procedures
and methods described for the detection program in Section
2,4 should be employed. The assessment may involve specific
analyses of a variety of complex substances and mixtures in
ground water. Sampling procedures, as in detection program
monitoring, should be selected so as to have the least effect
on the quality of the monitored parameters (see Scalf, et al;
1"81; pp. 43-71, 87-93).
It is strongly recommended that the owner or operator
consult with the laboratory personnel to whom he will be
submitting samples on the hazardous parameters for analysis
(refer to comprehensive list) and receive recommendations for
any specialized sample collection and/or handling procedures
necessary.
Analytical Procedures
After determining the appropriate sampling procedures,
the owner or operator must determine appropriate analytical
procedures (see Section 2.4). Acceptable procedures can be
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found in the references in Table 2-3 or from comparable analytical
references. The owner or operator should select appropriate
analytical methods in consultation with the laboratory, taking
into account the parameters to be analyzed, appropriate (i.e.,
state of the art) concentration detection limits and
instrumentation required.
After analysis, the owner or operator should receive
from the laboratory a report documenting the analyzed substances
and their respective concentrations or values found in each
sample. The owner or operator should examine the report to
ensure that all samples sent to the laboratory were analyzed
and that all requested concentration determinations have been
made. In addition, the owner or operator should note any
high or low concentration values for a particular parameter,
relative to determinations for all other samples, Anomalous
concentration values may indicate possible human error or
unusual site conditions that warrant closer scrutiny during
future assessments.
3.4.2 Complex Case Determinations
In a complex case, it is assumed that existing facility
records do not provide sufficient information for completing
a list of all hazardous wastes managed by the facility.
Other methods for identifying these substances must be employed
in order to compile a list.
Compiling a list
All records that do exist for waste handled during past
and present facility operations should be utilized to compile
a preliminary list of hazardous wastes. The sources described
in the preceding simple case discussion should provide any
available records on waste composition. The owner or operator
should also review the indicator parameter data for the
affected downgradient well(s) generated during the detection
program (if implemented). The data for pH, specific conductance,
total organic carbon (TOO, and total organic halogen (TOX) ,
can provide a general qualitative assessment of the ground
water, indicating the types of substances present. An increase
in specific conductance or a change in pH value would indicate
the presence of inorganic compounds. An increase in TOC and
TOX would indicate that organic substances had entered the
ground water.
Another step in identifying components of the waste is
to screen the potential contaminants in the waste management
area by collecting representative samples of the waste if
this can be done safely (e.g., at various levels of a surface
impoundment, or at different locations at a landfill). These
samples should then be analyzed by a laboratory using procedures
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similar to those for a general waste analysis (see simple
case discussion). Procedures for sample collection and analysis
nuiy be those specified by the facility's written waste analysis
plan required by 40 CFR Part 265.13(b). This screening method
will provide information concerning waste composition (e.g.,
chemical classes and individual compounds). Any waste
components identified by screening of the waste management
area should be added to the list for analysis of ground-water
s tuples.
Data collected from on-site investigations should be
compared against the list of substances compiled from existing
records to determine if the results verify the existing list
and/or identify additional hazardous parameters that should
be analyzed. The use of both existing records and field
screening techniques aid in compiling a more comprehensive
list of contaminants. If the owner or operator does not view
the "final" list of hazardous wastes as sufficient, despite
the on-site surveys, he should request that the laboratory
scan the samples (e.g., using gas chromatography/ mass
spectrometry) to determine other specific parameters.
Sampling and Analysis Procedures
The general procedures for sampling and analysis remain
the same as for simple case determinations described earlier.
3 . 5 Case Studies
Two simplified case studies are presented below to
illustrate methods for conducting a ground-water quality
Si- sessment.
Glacial Aquifer
Introduction
Wastes containing chromium have been disposed in a
surface impoundment located in a formation composed of glacial
outwash sediments. The disposal site is bounded to the south
by a small creek that may serve as a discharge area. Data
from water quality analyses (downgradient private supply
wells) indicate that chromium-containing leachate has percolated
clown through the unsaturated zone, contaminating the ground-
water supply. Ground-water quality assessment efforts include
tracking the extent of the leachate plume, determining the
rate of plume migration and determining concentrations of the
parameters of interest.
Hydrogeologic Framework
Information from available literature indicates that the
impoundment is located in an aquifer composed of glacial
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outwash material with a saturated thickness of 25-43 meters.
The aquifer consists of beds and lenses of fine to coarse sand
and gravel, with thin lenses and beds of fine to medium sand
and silt interbedded with the coarser material.
Assessment Methodology
In the assessment strategy, surface geophysical techniques
can be utilized to aid in determining the extent of
contamination. Information to aid in determining the lateral
and vertical extent of the plume can be acquired by conducting
an electrical resistivity survey. Assuming there is no
interference from transmission lines or underground pipes,
etc., an unconsolidated aquifer (e.g. glacial) with a relatively
shallow water table may provide a satisfactory setting for
conducting such a survey.
The nature of the contamination indicates an apparent
resistivity 5 to 10 times lower than that of the regional
ground water. Since contaminated ground water in this
particular discharge had a high free ion content, the
resistivity values obtained were well-defined on a resistivity
contour map. Significant changes in the contours may aid in
identifying the extent of the plume. In addition, an
electromagnetic conductivity survey can corroborate the
resistivity findings and assist in planning borehole/monitoring
well locations.
On the basis of results obtained from the above surveys,
boreholes and monitoring wells were installed. The location
of boreholes/wells should provide data on background water
quality and the rate and extent of ground-water contamination.
Formation samples should be obtained at appropriate intervals
during the drilling of boreholes. The installation of
boreholes/wells should continue until the limits of contamination
can be ascertained.
Determination of hydraulic conductivity should be made
by field methods. In addition, water level elevations obtained
from the monitoring wells can be used to construct a flow net
to indicate the hydraulic gradient(s). Then, the Darcy-based
equation (v = Ki/n) can be applied to determine the average
velocity (v) of movement.
Concentrations of the parameters of interest should be
determined for each sampling point. Contaminant concentration
isopleth maps should be drawn for parameters of interest to
depict lateral and vertical spread.
Limestone Aquifer Introduction
Significant ground-water contamination was suspected in
the vicinity of a plant site consisting of a number of surface
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impoundments which are used to settle effluent from the
industry's waste-water treatment facility. Organic solvents
(including benzene) are known to be components of the plant
waste stream.
Hydrogeologic Framework
Available historical data and field observations indicate
that the area is underlain by approximately 6 to 12 m of clay
over fractured limestone bedrock. This clay has a very low
hydraulic conductivity and may act as a confining layer for
the underlying limestone aquifer. Faults in the limestone
act as ground-water conduits, with broken and brecciated
material having a high porosity and high hydraulic conductivity.
Assessment Methodology
The water level in this area is at the limestone and
clay interface. Production wells in this area are cased in
the limestone aquifer. One downgradient production well in
the area exhibited high concentrations of benzene and other
organic solvents.
The techniques of electrical resistivity and electomagnetic
conductivity would likely be inappropriate in this setting as
the clay content of the overburden material would mask low
resistive or high conductive values commonly found in
contaminated ground water. Also, these methods would not be
appropriate to detect these contaminants. However, aerial
photography is a useful technique in this geologic setting.
The photographs may indicate surface manifestations of
fractures in the limestone formation which will be of value
in discerning the ground-water flow within the aquifer.
These fracture traces can also delineate areas where high
concentrations of contaminants are suspected. The production
well exhibiting high concentrations of benzene and other
organic solvents is 200 feet downgradient from an impoundment
excavated down to the limestone interface. Migration of
contaminants occurs along the top of the limestone formation
and through solution joints.
Considerations for determining the location of monitoring
wells should include the concentration of benzene and other
organic solvents in the production well (200 feet downgradient
from the source) and the location of fracture traces in the
limestone formation. Particular attention should be payed to
intersections of these fractures. Such monitoring wells,
cased at different intervals within the limestone formation,
can provide data concerning the movement of contaminants
through solution joints.
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Once the length, breadth and depth of the plume of
contamination have been identified, it is essential to
determine the rate of movement. This will enable rough
predictions to be made of when contaminants will reach
downgradient water supplies. The Darcy-based equation may be
applied to determine the flow rate if the suspected rate
falls within the equation's useful limits (see Freeze and
Cherry, 1979, pp. 72-73). If not within these limits, other
rate-determining methods (e.g., use of tracers) should be
used.
3.6 Recordkeeping and Reporting
Recordkeeping
The owner or operator is required by §265.94(b)(1) to
keep records of all analyses and evaluations specified in his
ground-water quality assessment plan. In this way, the most
current information on the rate and extent of contaminant
migration and the concentration of contaminants in the ground
water is readily available. These records must satisfy the
requirements of §265.93(d)(3) and must be kept until final
closure of the facility; and, for disposal facilities,
throughout the post-closure care period as well. The recorded
information must include:
the number, location, and depth of wells; the number
and location of any other sampling locations;
sampling and analytical methods (e.g., field screening
techniques) for those hazardous wastes or hazardous
waste constituents in the facility;
evaluation procedures, including any use of
previouslygathered ground-water quality information;
and
- the schedule (i.e., chronology) of implementation.
The content and organization of these records must
clearly reflect the results of the ground-water quality
assessment program according to the objectives of defining
the rate and extent of contaminant migration and the concentration
of contaminants in the ground water. Relevant site-specific
conditions should be highlighted. Records should be readily
accessible to both the owner or operator and the Regional
Administrator at all times. Data should be maintained in an
organized manner and be reproducible.
Reporting
Section 265.93(d)(5) requires reporting assessment
results to the Regional Administrator within fifteen days of
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the first determination. Subsequent assessment reports must
be submitted annually. See the "Note" in Section 2.5.3
concerning annual reports under §265.75. Assessment reports
should include:
the calculated (or measured) rate of migration of
contaminants;
- the extent of migration of contaminants (i.e., distance
traveled from source and approximate spatial
configuration of ground water affected); and
the concentration of hazardous waste or hazardous
waste constituents in the ground water.
The first assessment report will give the Agency
information about the nature of the contamination (if it has
been determined that a facility discharge entered the ground
water). This report will supplement the written notice from
the detection program (if it was implemented) that the facility
may be affecting ground-water quality. Thus, the Agency is
informed as soon as possible of the status of contaminated
aquifers.
Subsequent assessment reporting assures that the Agency
has updated information on the ground-water contamination
problem. Knowing the concentration, migration rate and extent
of hazardous waste or hazardous waste constituents in ground
water will aid the Agency in determining any potential threat
which may be posed to human health or the environment in the
vicinity of the facility and in determining any appropriate
action needed. The format of these reports should provide
a clear identification of the information given and employ
a logical order of discussion.
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(EPA/530/SW-611) . U.S. EPA, Office of Solid Waste,
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Appendix A - Interim Status
Ground-Water Monitoring Regulations
Subpart F—Ground-Water Monitoring
SM5.M AppUeaWttty.
(a) Within one year after the effective
date of these regulations, the owner or
operator of a surface impoundment,
landfill, or land treatment facility which
is used to manage hazardous waste
must implement a ground-water
monitoring program capable of
determining the facility's impact on the
quality of ground water in the
uppermost aquifer underlying the
facility, except as § 265.1 and paragraph
(c) of this Section provide otherwise.
(b) Except as paragraphs (c) and (d) of
this Section provide otherwise, the
owner or operator must install, operate,
and maintain a ground-water monitoring
system.which meets the requirements of
S 265.91, and must comply with
SS 265.92-265.94. This ground-water
monitoring program must be carried out
during the active life of the facility, and
for disposal facilities, during the post-
closure care period as well.
(c) All or part of the ground-water
monitoring requirements of this Subpart
may be waived if the owner or operator
can demonstrate that there is a low
potential for migration of hazardous
waste or hazardous waste constituents
from the facility via the uppermost
aquifer to water supply wells (domestic,
industrial, or agricultural) or to surface
water. This demonstration must be in
writing, and must be kept at the facility.
This demonstration must be certified by
a qualified geologist or geotechnical
engineer and must establish the
following:
(1) The potential for migration of
hazardous waste or hazardous waste
constituents from the facility to the
uppermost aquifer, by an evaluation of:
(i) A water balance of precipitation,
evapotranspiration, runoff, and
infiltration; and
(ii) Unsaturated zone characteristics
(i.e., geologic materials, physical
properties, and depth to ground water);
and
(2) The potential for hazardous waste
or hazardous waste constituents which
enter the uppermost aquifer to migrate
to a water supply well or surface water,
by an evaluation of:
(i) Saturated zone characteristics (i.e.,
geologic materials, physical properties,
and rate of ground-water flow); and
(ii) The proximity of the facility to
water supply wells or surface water.
(d) If an owner or operator assumes
(or knows) that ground-water monitoring
of indicator parameters in accordance
with. §§265.91 and 265.92 would show
statistically significant increases (or
decreases in the case of pH) when
evaluated under § 265.93(b), he may,
install, operate, and maintain an
alternate ground-water monitoring
system (other than the one described in
§§ 265.91 and 265.92). If the owner or
operator decides to use an alternate
33240
Federal Register / Vol. 45, No, 98
! Monday, May 19, 1980 / Rules and Regulations
ground-water monitoring system he
must:
(1) Within one year after the effective
date of these regulations, submit to the
Regional Administrator a specific plan,
certified by a qualified geologist or
geotechnical engineer, which satisfies
the requirements of § 265.93(d)(3), for an
alternate ground-water monitoring
system;
(2) Not later than one year after the
effective date of these regulations,
initiate the determinations specified in
§ 265.93(d)(4);
(3) Prepare and submit a written
report in accordance with § 265.93(d)(5);
(4) Continue to make the
determinations specified in
§ 265.93(d)(4) on a quarterly basis until
final closure of the facility; and
(5) Comply with the recordkeeping
and reporting requirements in
§ 265.94(b).
§ 265.91 Ground-water monitoring
system.
(a) A ground-water monitoring system
must be capable of yielding ground-
water samples for analysis and must
consist of:
(1) Monitoring wells (at least one)
installed hydraulically upgradient (i.e.,
in the direction of increasing static
head) from the limit of the waste
management area. Their number,
locations, and depths must be sufficient
to yield ground-water samples that are:
(i) Representative of background
ground-water quality in the uppermost
aquifer near the facility; and
(ii) Not affected by the facility; and
(2) Monitoring wells (at least three)
installed hydraulically downgradient
(i.e., in the direction of decreasing static
head) at the limit of the waste
management area. Their number,
locations, and depths must ensure that
they immediately detect any statistically
significant amounts of hazardous waste
or hazardous waste constituents that
migrate from the waste management
area to the uppermost aquifer.
(b) Separate monitoring systems for
each waste management component of a
facility are not required provided that
provisions for sampling upgradient and
downgradient water quality will detect
any discharge from the waste
management area.
(1) In the case of a facility consisting
of only one surface impoundment,
landfill, or land treatment area, the
waste management area is described by
the waste boundary (perimeter).
(2) In the case of a facility consisting
of more than one surface impoundment,
landfill, or land treatment area, the
waste management area is described by
an imaginary boundary line which '
circumscribes the several waste
management components.
(c) All monitoring wells must be cased
in a manner that maintains the integrity
of the monitoring well bore hole. This
casing must be screened or perforated,
and packed with gravel or sand where
necessary, to enable sample collection
at depths where appropriate aquifer
flow zones exist. The annular space (i.e.,
the space between the bore hole and
well casing) above the sampling depth
must be sealed with a suitable material
(e.g., cement grout or bentonite slurry) to
prevent contamination of samples and
the ground water.
§ 265.92 Sampling and analysis.
(a) The owner or operator must obtain
and analyze samples from the installed
grouncWater monitoring system. The
owner of operator must develop and
follow a grotind-water sampling and
analysis plan. He must keep this plan at
the facility. The plan must include
procedures and techniques for:
(1) Sample collection;
(2) Sample preservation and shipment;
(3) Analytical procedures; and
(4) Chain of custody control.
[Comment: See "Procedures Manual For
Ground-water Monitoring At Solid
Waste Disposal Facilities," EPA-530/
SW-611, August 1977 and "Methods for
Chemical Analysis of Water and
Wastes," EPA-600/4-79-020, March
1979 for discussions of sampling and
analysis procedures.]
(b) The owner or operator must
determine the concentration or value of
the following parameters in ground-
water samples in accordance with
paragraphs (c) and (d) of this section:
(1) Parameters characterizing the
suitability of the ground water as a
drinking water supply, as specified in
Appendix III.
(2) Parameters establishing ground-
water quality:
(i) Chloride
(ii) Iron
{iii) Manganese
(iv) Phenols
(v) Sodium
(vi) Sulfate
[Comment: These parameters are to be
used as a basis for comparison in the
event a ground-water quality
assessment is required under
§ 265.93(d).]
(3) Parameters used as indicators of
ground-water contamination:
(i)PH
(ii) Specific Conductance
(iii) Total Organic Carbon
(iv) Total Organic Halogen
(c)(l)fFor all monitoring wells, the
owner or operator must establish initial
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Federal Register / Vol. 45, No. 98 / Monday, May 19, 1980 / Rules and Regulations 33241
background concentrations or values of
ail parameters specified in paragraph (b)
of this Section. He must do this
quarterly for one year.
(2) For each of the indicator
parameters specified in paragraph (b)(3j
of this Section, at least four replicate
measurements must be obtained for
each sample and the initial background
arithmetic mean and variance must be
determined by pooling the replicate
measurements for the respective
parameter concentrations or values in
samples obtained from upgradient wells
during the first year.
(d) After the first year, all monitoring
wells must be sampled and the samples
analyzed with the following frequencies:
(1) Samples collected to establish
ground-water quality must be obtained
and analyzed for the parameters
specified in paragraph (b)(2) of this
Section at least annually.
(2) Samples collected to indicate
ground-water contamination must be
obtained and analyzed for the
parameters specified in paragraph (b){3)
of this Section at least semi-annually.
(e) Elevation of the ground-water
surface at each monitoring well must be
determined each time a sample is
obtained.
§ 265.93 Preparation, evaluation, and
response.
(a) Within one year after the effective
date of these regulations, the owner or
operator must prepare an outline of a
ground-water quality assessment
program. The outline must describe a
more comprehensive ground-water
monitoring program (than that described
in §§ 265.91 and 265.92) capable of
determining:
(1) Whether hazardous waste or
hazardous waste constituents have
entered the ground water;
(2) The rate and extent of migration of
hazardous waste or hazardous waste
constituents in the ground water; and
(3) The concentrations of hazardous
waste or hazardous waste constituents
in the ground water.
(b) For each indicator parameter
specified in § 265.92(b)(3), the owner or
operator must calculate the arithmetic
mean and variance, based on at least
four replicate measurements on each
sample, for each well monitored in
accordance with § 265.92(d)(2), and
compare these results with its initial
background arithmetic mean. The
comparison must consider individually
each of the wells in the monitoring
system, and must use the Student's t-test
at the 0.01 level of significance (see
Appendix IV) to determine statistically
significant increases (and decreases, in
the case of pH) over initial background.
(c)(l) If the comparisons for the
upgradient wells made under paragraph
(b) of this Section show a significant
increase (or pH decrease), the owner or
operator must submit this information in
accordance with § 265.94{a)(2)(ii).
(2.) If the comparisons for
downgradient wells made under
paragraph (b) of this Section show a
significant increase (or pH decrease),
the owner or operator must then
immediately obtain additional ground-
wafer samples from those downgradient
wells where a significant difference was
delected, split the samples in two, and
obtain analyses of all additional
samples to determine whether the
significant difference was a result of
laboratory error.
(<1)(1) If the analyses performed under
paragraph (c)(2) of this Section confirm
the significant increase (or pH
decrease), the owner or operator must
provide written notice to the Regional
Administrator—within seven days of the
date of such confirmation—that the
fac:lity may be affecting ground-water
quality.
(2) Within 15 days after the
notification under paragraph (d)(l) of
this Section, the owner or operator must
develop and submit to the Regional
Administrator a specific plan, based on
the outline required under paragraph (a)
of this Section and certified by a
qualified geologist or geotechnical
engineer, for a ground-water quality
assessment program at the facility.
(3) The plan to be submitted under
§ 2i)5.90(d)(l) or paragraph (d)(2) of this
Section must specify:
(i) The number, location, and depth of
wells;
(ii) Sampling and analytical methods
for those hazardous wastes or
hazardous waste constituents in the
facility;
(lii) Evaluation procedures, including
any use of previously-gathered ground-
water quality information; and
(iv) A schedule of implementation.
(4) The owner or operator must
implement the ground-water quality
assessment plan which satisfies the
requirements of paragraph (d)(3) of this
Section, and, at a minimum, determine:
(i) The rate and extent of migration of
the hazardous waste or hazardous
waste constituents in the ground water;
and
(ii) The concentrations of the
hazardous waste or hazardous waste
constituents in the ground water.
(5) The owner or operator must make
his first determination under paragraph
(d)(4) of this Section as soon as
technically feasible, and, within 15 days
after that determination, submit to the
Regional Administrate! a written report
containing an assessment of the ground-
water quality.
(6) If the owners or operator
determines, based on the results of the
first determination under paragraph
(d)(4) of this Section, that no hazardous
waste or hazardous waste constituents
from the facility have entered the
ground water, then he may reinstate the
indicator evaluation program described
in § 265.92 and paragraph (b) of this
Section. If the owner or operator
reinstates the indicator evaluation
program, he must so notify the Regional
Administrator in the report submitted
under paragraph (d)(5) of this Section.
(7j If the owner or operator
determines, based on the first
determination under paragraph (d)(4) of
this Section, that hazardous waste or
hazardous waste constituents from the
facility have entered the ground water,
then he:
(i) Must continue to make the
determinations required under
paragraph (d)(4) of this Section on a
quarterly basis until final closure of the
facility, if the ground-water quality
assessment plan was implemented prior
to final closure of the facility; or
(ii) May cease to make the
determinations required under
paragraph (d)(4) of this Section, if the
ground-water quality assessment plan
was implemented during the post-
closure care period.
(e) Notwithstanding any other
provision of this Subpart, any ground-
water quality assessment to satisfy the
requirements of § 265.93(d)(4) which is
initiated prior to final closure of the
facility must be completed and reported
in accordance with § 265.93(d)(5).
(f) Unless the ground water is
monitored to satisfy the requirements of
§ 265.93(d)(4), at least annually the
owner or operator must evaluate the
data on ground-water surface elevations
obtained under § 265.92(e) to determine
whether the requirements under
§ 265.91(a) for locating the monitoring
wells continues to be satisfied. If the
evaluation shows that § 265.91[a) is no
longer satisfied, the owner ur operator
must immediately modify the number,
location, or depth of the monitoring
wells to bring the ground-water
monitoring system into compliancu widi
this requirement.
§ 265.94 Recordkeeping and reporting.
(a) Unless the ground water is
monitored to satisfy the requirements of
§ 265 33(d)(4). the owner or operator
must:
(1) Keep records of the analyses
U'quned in § 265.'J2(<;) i,nd (dl. the
iibiiivuiti d gioimd-v..ner si:.I
''!'•*""" i.. ii'uui. rd MI § _i/,i :i i>] i,nd
149
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33242 Federal Register / Vol. 45, No. 98 / Monday, May 19, 1980 / Rules and Regulations
the evaluations required in § 265.93(b)
throughout the active life of the facility.
and, for disposal facilities, throughout
the post-closure care period as well; and
(2) Report the following ground-water
monitoring information to the Regional
Administrator:
(i) During the first year when initial
background concentrations are being
established for the facility:
concentrations or values of the
parameters listed in § 265.92(b)(l) for
each ground-water monitoring well
within 15 days after completing each
quarterly analysis. The owner or
operator must separately identify for
each monitoring well any parameters
whose concentration or value has been
found to exceed the maximum
contaminant levels listed in Appendix
III.
(ii) Annually: concentrations or values
of the parameters listed in § 265.92(b)(3]
for each ground-water monitoring well,
along with the required evaluations for
these parameters under § 265.93(b). The
owner or operator must separately
identify any significant differences from
initial background found in the
upgradient wells, in accordance with
§ 265.93(c)(l). During the active life of
the facility, this information must be
submitted as part of the annual report
required under § 265.75.
(iii) As a part of the annual report
required under § 265.75: results of the
evaluation of ground-water surface
elevations under § 265.93(f)- and a
description of the response to that
j valuation, where applicable.
(b) If the ground water is monitored to
satisfy the requirements of
j 265.93(d)(4), the owner or operator
must:
(1) Keep records of the analyses and
evaluations specified in the plan, which
satisfies the requirements of
§ 265.93(d)(3), throughout the active life
uf the facility, and, for disposal
facilities, throughout the post-closure
care period as well; and
(2) Annually, until final closure of the
facility, submit to the Regional
Administrator a report containing the
results of his ground-water quality
assessment program which includes, but
is not limited to, the calculated (or
measured) rate of migration of
hazardous waste or hazardous waste
constituents in the ground water during
the reporting period. This report must be
submitted as part of the annual report
required under § 265.75.
150
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1254 Federal Register / Vol. 47, No. 6 / Monday, January 11, 1982 / Rules and Regulations
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Part 265
[SW-FRL 1999-2]
Standards for Owners and Operators
of Hazardous Waste Disposal
Facilities; Interim Rule
AGENCY: Environmental Protection
Agency,
ACTION: Interim final amendments to
rule.
SUMMARY: EPA is today promulgating, in
interim final form, amendments to the
ground-water monitoring standards for
certain hazardous waste surface
impoundments used to neutralize
corrosive wastes. The amendments
provide for a waiver of these standards
for any surface impoundment that (1)
Contains wastes which are hazardous
only because they exhibit the corrosivity
characteristic and contains no other
hazardous wastes, and (2) is
demonstrated to rapidly neutralize the
wastes so that there is no potential for
migration of any hazardous waste out of
the impoundment.
The purpose of today's amendment is
to relieve owners and operators of
neutralization surface impoundments
from having to monitor ground water in
cases where such monitoring is not
necessary to protect human health and
the environment. Since the compliance
date for the ground-water monitoring
requirements is November 19,1981,
today's limited exception to those
requirements is being made effective
immediately.
DATE: Today's interim final amendments
are effective January 11,1982.
EPA will accept public comments on
the proposed amendments until March 9,
1982.
ADDRESSES: Comments on the interim
final amendments should be sent to
Deneen Shrader, Docket Clerk, Office of
Solid Waste (WH-562), U.S.
Environmental Protection Agency, 401 M
Street, SW., Washington, D.C. 20460.
Comments should identify the regulatory
docket as follows: "Docket No. 3004,
Amendment of § 265.90(c)". Requests for
a hearing should be addressed to John P.
Lehman, Director, Hazardous and
Industrial Waste Division, Office of
Solid Waste (WH-565), U.S.
Environmental Protection Agency,
Washington, D.C. 20460.
The official docket for this regulation
is located in Room 2636, U.S.
Environmental Protection Agency, 401 M
Street, SW., Washington, D.C. 20460 ard
is available for viewing from 9:00 a.m to
4:00 p.m., Monday through Friday,
excluding holidays.
FOR FURTHER INFORMATION CONTACT:
The RCRA hazardous waste hotline,
Office of Solid Waste (WH-565), U.S.
Environmental Protection Agency, 401 M
Street, SW, Washington, D.C. 20460,
800/424-9346 (382-3000 in Washington,
D.C.). For specific information on this
amendment, contact Barry Stoll, Office
of Solid Waste (WH-564), U.S.
Environmental Protection Agency, 401 M
Street, SW, Washington, D.C. 20460,
(202) 755-9116.
SUPPLEMENTARY INFORMATION:
I. Purpose and Content of the
Amendment
On May 19,1980, EPA promulgated
hazardous waste regulations in 40 CFR
Parts 260-265 (45 FR 33066 et seq.} which
established, in conjunction with earlier
regulations promulgated on February 26,
1980 (45 FR 12721 et seq.), the principal
elements of the hazardous waste
management program under Subtitle C
of the Resource Conservation and
Recovery Act of 1976, as amended (42
U.S.C. 6921, et seq.). Part 265 of the May
19 regulations set forth standards
applicable to owners and operators of
hazardous waste treatment, storage, and
disposal facilities during the "interim
status" period. Subpart F (§§ 265.90-
265.94) of those regulations established
ground-water monitoring interim status
standards applicable to land disposal
facilities.
Section 265.90(c) provides that all or
part of the groundwater monitoring
requirements of Subpart F may be
waived if the owner or operator
demonstrates that there is a low
potential for migration of hazardous
waste or hazardous waste constituents
from the facility via the uppermost
aquifer to water supply wells or to
surface water. The demonstration must
be in writing and must be certified by a
qualified geologist or geotechnical
engineer and must establish the
potential for migration of the hazardous
waste or hazardous waste constituents
from the facility to the uppermost
aquifer and from that aquifer to water
supply wells or surface water. This
demonstration must be based on an
evaluation of several hydrogeological
factors set forth in the regulation.
As presently written, this self-
implementing waiver provision is.
available only when hydrogeological
factors reduce the migration potential to
a low probability.'The regulation does
1 As explained in the preamble to § 265.90(c) (45
FR 33192, May 19,1980), a complete waiver of all
Sabpart F monitoring requirements is available only
when the owner or operator can demonstrate that
151
not allow consideration of the disposed
wastes' characteristics and the facility
design to be used as a basis for reducing
monitoring requirements. At the time
that the regulation was promulgated,
EPA was concerned that the state of
knowledge about hazardous wastes and
facility designs was not sufficiently
certain to justify reductions in the basic
monitoring system during interim status.
(See 45 FR 33192, May 19,1980.)
Since the time it promulgated
§ 265.90(c), EPA has become aware of
one situation where it is appropriate to
allow a waiver of ground-water
monitoring requirements to be based
upon consideration of the facility and
the wastes disposed in the facility.
Several industries operate surface
impoundments which contain no
hazardous wastes except corrosive
wastes which themselves are hazardous
only due to their corrosivity. In some
cases, these wastes may be placed in
the impoundment together with large
volumes of non-hazardous wastes. In
some of these cases, particularly where
active mechanical mixing is performed
in the impoundment, it may be reliably
demonstrated that the corrosive wastes
are neutralized shortly after being
placed in the inpoundment. In such
cases, there may be no potential for any
hazardous wastes to migrate out of the
impoundment.
For the neutralization surface
impoundments described above, EPA
believes that it makes little sense to
monitor the ground water beneath the
facilities. Therefore, EPA is amending
§ 265.90 to provide a waiver of Subpart
F requirements for these types of
facilities upon a demonstration that
there is no potential for migration of
hazardous wastes out of the facility. The
demonstration would have to show,
based on consideration of the corrosive
wastes and the impoundment, that the
corrosive wastes will be neutralized
before they migrate out of the facility.
The demonstration must be certified by
a professional qualified to make this
type of technical demonstration, rather
than necessarily by a geologist or
geotechnical engineer (as required in
§ 265.90(c)).
It may be that there are types of
facilities other than neutralization
surface impoundments for which
reliable demonstrations can in some
instances be made, based upon
consideration of the nature of the
wastes and of the facility, to show that
there is no potential for migration of
hazardous waste or hazardous waste
there is no potential for migration to water supply
wells or surface water.
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Federal Register / Vol. 47. No. 6- / Monday. January 11. 1982 / Rule? and Regulations 1255
constituents from the facility. EPA
welcomes information (including
detailed data) on such facilities.
II. Promulgation of Today's Amendment
in Interim Final Form
The compliance date for the existing
Subpart F ground-water monitoring
requirements is November 19,1981.
Unless today's amendment is
promulgated and takes effect
immediately, owners or operators of
neutralization surface impoundments ,
would be required to comply
immediately with the Subpart F
requirements even when they can
demonstrate that those requirements are
unnecessary to protect human health
and the environment. Such a result
would be contrary to the public interest.
Therefore, EPA believes that good cause
exists to promulgate today's amendment
in interim final form without prior notice
and comment
EPA invites public comment on
today's interim final rule: Consistent
with its duty to fully consider all
comments, EPA will promulgate a final ~
rule as soon as possible after the close '
of the public comment period.
m. Effective date <
Section 3010(b) of RCRA provides that
EPA's hazardous waste regulations take
effect six months after their
promulgation. The purpose of this
statutory requirement is to allow
persons affected by the regulations
sufficient lead time to comply with
major new regulatory requirements.
Today's amendment, however, does not
impose a new requirement but rather
relaxes an existing requirement.
Therefore, the Agency believes it is
consistent with the intent of Section
3010(b) to make today's amendment
immediately effective.
IV. Regulatory Analysis
Section 3(b) of Executive Order 12291.
40 FR13193 (February 19,1981), requires
EPA to initially determine whether a
rule that it intends to propose or issue is"
a majorrule and to prepare regulatory
impact analyses for all major rules.
EPA has determined that the
amendment being promulgated today is
not a major rule. As discussed above,
this amendment will allow a waiver of
ground-water monitoring requirements
under a limited set of circumstances.
Accordingly, a Regulatory Impact
Analysis is not being prepared for this .
amendment.
This regulation was submitted to the
Office of Management and Budget for
review as required by Executive Order
12291.
The information collection
requirements in this interim final rule
will be submitted to the Office of
Management and'Budget for clearance
under the Paperwork Reduction Act of
1980. The information requirements or
recordkeeping in this interim final rule
will not take place until it has been
cleared by the Office of Management
and Budget If OMB approves, the
information collection requirements will
take effect as set forth in this interim
final rule. If not, EPA will revise the
information requirements (and this rule
if appropriate) to comply with OMB's
determination.
Under the Regulatory Flexibility Act 5
U.S.C. 601 etseq., EPA is required to
determine whether a regulation will
have a significant impact on a
substantial number of small entities so
as: to require a regulatory analysis. The
additional waiver opportunity created
by this amendment should, if anything,
reduce the burden of compliance with
the hazardous waste disposal
regulations for small entities. Therefore,
pursuant to 5 U.S.C. 605(b), I hereby
certify that this rule will not have a
significant adverse impact on a
substantial number of small entities.
Dated: December 28,1981.
Anne M. Gorsuch,
Administrator.
PART 265—INTERIM STATUS
STANDARDS FOR OWNER AND
OPERATORS OF HAZARDOUS WASTE
TREATMENT, STORAGE, AND
DISPOSAL FACILITIES
For the reasons set out in the
preamble, Title 40 of the Code of Federal
Regulations is amended as follows:
1. The authority citation for Part 265
reads as follows:
Authority: Sees. 1000, 2002(a), and 3004.
Solid Waste Disposal Act as amended by the
Resource Conservation and Recovery Act of
1978, as amended (42 U.S.C. 8905, 6912{a),
and 6924).
2. Section 265.90 is amended by
adding paragraph (e) to read as follows:
§265.90 Applicability.
*•*•-*
(e) The ground-water monitoring
requirements of this Subpart may be
waived with respect to any surface
impoundment that (1) Is used to
neutralize wastes which are hazardous
solely because they exhibit the
corrosivity characteristic under § 261.22
of this Chapter or are listed as
hazardous wastes in Subpart D of Part
261 of this Chapter only for this reason,
and (2) contains no other hazardous
wastes, if the owner or operator can
demonstrate that there is no potential
for migration of hazardous wastes from
the impoundment; The demonstration
must establish,-based upon
consideration of the characteristics of
the wastes .and the impoundment that
the corrosive wastes will be neutralized
to the extent that they ho longer meet
the corrosivity characteristic before they
can migrate out of the impoundment.
The demonstration must be in writing
and must be certified by a qualified
professional.
[FR Doe. 82-823 Filed 1-8-32 8:45 am)
BILLING CODE 6060-30-11
152
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Appendix B
USGS Information Contacts
wra
Water
Resources
Division
information
guide
November 1980
U.S. Geological Survey
153
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HGRDQURRTGR5
U.S. GEOLOGICAL SURVEY
WATER RESOURCES DIVISION
(Mailstop no.) NATIONAL CENTER
12201 SUNRISE VALLEY DRIVE
RESIGN, VIRGINIA 22092
Telephone: (703) 860 + 4-digit extension
FTS 928 + 4-digit extension
Switchboard: ext. 7000
Personnel locator: ext. 6118
Office hours: 7:45 a.m. to 4:15 p.m. Eastern Time
CHIEF HYDROLOGIST
Mail stop: 409
Room: 5A-402
Telephone: ext. 6921
ASSOCIATE CHIEF HYDROLOGIST
Mail stop: 408
Room: 5A-324
Telephone: ext. 6921
OFFICE OF INTERNATIONAL HYDROLOGY
Mail stop: 470
Room: 3B-410
Telephone: ext. 6548
OFFICE OF WATER DATA COORDINATION
Mail stop: 417
Room: 5A-116
Telephone: ext. 6931
ASSISTANT CHIEF HYDROLOGIST FOR OPERATIONS
Mail stop: 441 Room: 5A-302 Telephone: ext. 6801
ASSISTANT CHIEF HYDROLOGIST FOR SCIENTIFIC PUBLICATIONS & DATA MANAGEMENT
Mail stop: 440 Room: 5A-216 Telephone: ext. 6877
WATSTORE
(Automatic Data Section)
Mail stop: 437
Room: 5B-332
Telephone: ext. 6879
NAWDEX PROGRAM
OFFICE
Mail stop: 421
Room: 5A-130
Telephone: ext. 6031
NATIONAL WATER-USE
INFORMATION PROGRAM
Mail stop: 440
Room: 5A-213
Telephone: ext. 6877
SCIENTIFIC PUBLICATIONS
SECTION
Mail stop: 439
Room: 5A-210
Telephone: ext. 6881
ASSISTANT CHIEF HYDROLOGIST FOR RESEARCH & TECHNICAL COORDINATION
Mail stop: 414 Room: 5A-102 Telephone: ext. 6971
DEPUTY ASSISTANT CHIEF
HYDROLOGIST FOR RESEARCH
Mail stop: 413
Room: 5A-422
Telephone: ext. 6971
GROUND WATER
BRANCH
Mail stop: 411
Room: 5A-414
Telephone: ext. 6904
SURFACE WATER
BRANCH
Mail stop: 415
Room: 5A-104
Telephone: ext. 6837
QUALITY OF WATER
BRANCH
Mail stop: 41 2
Room: 5A-420
Telephone: ext. 6834
154
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NORTH€flST€RN R63ION
Connecticut, Delaware, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire,
New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, Virginia, Washington, D.C., West Virginia,
Wisconsin
OFFICE OF THE REGIONAL HYDROLOGIST
Address:
Regional Hydrologist
U.S. Geological Survey
National Center, Mail Stop 433
12201 Sunrise Valley Drive
Reston, VA 22092
Telephone: (703) 860-6985; FTS 928-6985
Office hours: 7:45 a.m. to 4:1 5 p.m. Eastern Time
DISTRICT OFFICES
CONNECTICUT
Address:
District Chief, WRD
U.S. Geological Survey
135 High Street, Rm. 235
Hartford, CT 06103
Telephone: (203) 244-2528; FTS 244-2528
Off ice hours: 8:00 a.m. to 4:30 p.m. Eastern Time
DELAWARE See also Maryland
Address:
Hydrologist-m-Charge
Subdistrict Office, WRD
U.S. Geological Survey
Federal Bldg., Rm. 1201
300 S. New Street
Dover, DE 19901
Telephone: (302) 734-2506; FTS 487-91 28
Office hours: 8:00 a.m. to 4:30 p.m. Eastern Time
DISTRICT OF COLUMBIA See Maryland
ILLINOIS
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 1026
Champaign, IL 61820
Office address:
605 N. Neil Street
Champaign
Telephone: (217) 398-5353; FTS 958-5353
Office hours: 8:00 a.m. to 4:30 p.m. Central Time
INDIANA
Address:
District Chief, WRD
U.S. Geological Survey
1819 North Meridian Street ]_
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MICHIGAN—Continued
Telephone: (517) 377-1608; FTS 374-1608
Office hours: 7 45 a.m. to 4.15 p.m. Eastern Time
MINNESOTA
Address:
District Chief, WRD
U.S. Geological Survey
Post Office Bldg., Rm. 702
St. Paul, MN 55101
Telephone: (612) 725-7841; FTS 725-7841
Office hours: 7:45 a.m. to 4:30 p.m. Central Time
NEW HAMPSHIRE See also Massachusetts
Mailing address:
Hydrologist-m-Charge
Subdistrict Office, WRD
U.S. Geological Survey
RFD 2, Box 352A
Concord, NH 03301
Office address:
Country Hills Professional Park
Bow
Telephone: (603) 224-7273, FTS 834-4739
Office hours: 7J45 a.m. to 4:1 5 p.m. Eastern Time
NEW JERSEY
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 1238
Trenton, NJ 08607
Office address:
Federal Bldg., Rm. 436
402 East State Street
Trenton
Telephone: (609) 989-2162; FTS 483-2162
Office hours: 8.00 a.m. to 4 30 p.m. Eastern Time
NEW YORK
Mai/ing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 1350
Albany, NY 12201
Office address:
U.S. Post Office and Courthouse, Rm. 236
Albany
Telephone: (51 8) 472-3107, FTS 562-3107
Office hours' 7 45 a.m. to 4 30 p.m Eastern Time
OHIO
Address:
District Chief, WRD
U.S. Geological Survey
975 West Third Avenue
Coiumbus, Oh 43212
OHIO—Continued
Telephone: (614) 469-5553; FTS 943-5553
Office hours: 7:45 a.m. to 4:30 p.m. Eastern Time
PENNSYLVANIA
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 1107
Harrisburg, PA 17108
Office address:
Federal Bldg., 4th Floor
228 Walnut Street
Harrisburg
Telephone: (71 7) 782-4514, FTS 590-4514
Office hours: 8:00 a.m. to 4 30 p.m. Eastern Time
RHODE ISLAND See a/so Massachusetts
Address:
Hydrologist-in-Charge
Subdistrict Office, WRD
U.S. Geological Survey
Federal Bldg. and U.S. Post Office, Rm. 224
Providence, Rl 02903
Telephone: (401) 528-4655; FTS 838-4655
Office hours: 8:00 a.m. to 4:30 p.m. Eastern Time
VERMONT See Massachusetts
VIRGINIA
Address:
District Chief, WRD
U.S. Geological Survey
200 West Grace Street, Rm. 304
Richmond, VA 23220
Telephone: (804) 771-2427; FTS 925-2427
Office hours: 8 00 a.m. to 4 45 p.m. Eastern Time
WEST VIRGINIA
Address:
District Chief, WRD
U.S. Geological Survey
Federal Bldg. and U.S. Courthouse, Rm. 3017
500 Quarner Street, East
Charleston, WV 25301
Telephone (304) 343-6181, ext 310, FTS 924-1310
Office hours: 1 45 a.m. to 4 30 p.m. Eastern Time
WISCONSIN
Address.
District Chief, WRD
U.S. Geological Survey
1815 University Avenue, Rm. 200
Madison, Wl 53706
Telephone: (608) 262-2488; FTS 262-2488
Office hours' SOOa.m to-I 30 p.m. Central Time
156
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SOUTH£flST€RN R83ION
Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, Puerto Rico, South Carolina, Tennessee,
Virgin Islands
OFFICE OF THE REGIONAL HYDROLOGIST
Address:
Regional Hydrologist
U.S. Geological Survey
Richard B. Russell Federal Bldg.
75 Spring Street, SW, Rm. 772
Atlanta, GA 30303
Telephone: (404) 221-5174; FTS 242-5174
Office hours: 7:30 a.m. to 4:15 p.m. Eastern Time
DISTRICT OFFICES
ALABAMA
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box V
University, AL 35486
Office address:
Oil and Gas Board Bldg., Rm. 202
University of Alabama
Tuscaloosa
Telephone: (205) 752-8104; FTS 229-2957
Off ice hours: 7:30 a.m. to 4:00 p.m. Central Time
FLORIDA
Address:
District Chief, WRD
U.S. Geological Survey
325 John Knox Road, Suite F-240
Tallahassee, FL 32303
Telephone: (904) 386-1118; FTS 946-4251
Office hours: 7:45 a.m. to 4:30 p.m. Eastern Time
GEORGIA
Address:
District Chief, WRD
U.S. Geological Survey
6481 Peachtree Industrial Blvd., Suite B
Doraville, GA 30360
Telephone: (404) 221-4858; FTS 242-4858
Office hours: 7:45 a.m. to 4:30 p.m. Eastern Time
KENTUCKY
A ddress:
District Chief, WRD
U.S. Geological Survey
Federal Bldg., Rm. 572
600 Federal Place
Louisville, KY 40202 157
KENTUCKY—Continued
Telephone: (502) 582-5241; FTS 352-5241
Office hours: 8:00 a.m. to 4.45 p.m. Eastern Time
MISSISSIPPI
Address:
District Chief, WRD
U.S. Geological Survey
Federal Office Bldg., Suite 710
100 West Capitol Street
Jackson, MS 39201
Telephone: (601) 969-4600; FTS 490-4600
Office hours: 7:45 a.m. to 4:30 p.m. Central Time
NORTH CAROLINA
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 2857
Raleigh, NC 27602
Office address:
Century Station, Post Office Bldg., Rm. 436
Raleigh
Telephone: (919) 755-4510; FTS 672-4510
Off ice hours: 8:00 a.m. to 4:45 p.m. Eastern Time
PUERTO RICO Caribbean District (Puerto Rico and U.S.
Virgin Islands)
Mailing Address:
District Chief, WRD
U.S. Geological Survey
GPO Box 4424
San Juan, PR 00934
Office address:
Building 652
Ft. Buchanan
Telephone: (809) 783-4660; FTS 967-1221,
ask operator for 753-4414
Office hours: 7'45 a.m. to 4:30 p.m. Atlantic Time
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SOUTH CAROLINA TENNESSEE
Address: Address:
District Chief, WRD District Chief, WRD
U.S. Geological Survey U-S- Geological Survey
c- -r^ _i c ., i n,_, o • ^rro Federal Bldg. and U.S. Court House,
Strom Thurmond Federal Bldg., Suite 658 Rm ^.413
1 835 Assembly Street Nashville, TN 37203
Columbia, SC 29210 Telephone: (615) 251-5424; FTS 852-5424
Telephone: (803) 765-5966; FTS 677-5966 Office hours: 7:45 a.m. to 4:30 p.m. Central Time
Off ice hours: 7'45 a.m. to 4:30 p.m. Eastern Time VIRGIN ISLANDS See Puerto Rico
158
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C(ENTRRl RG3ION
Arkansas, Colorado, Iowa, Kansas, Louisiana, Missouri, Montana, Nebraska, New Mexico, North Dakota, Oklahoma,
South Dakota, Texas, Utah, Wyoming
OFFICE OF THE REGIONAL HYDROLOGIST
Mailing address:
Regional Hydrologist
U.S. Geological Survey
Mail Stop 406, Box 25046
Denver Federal Center
Lakewood, CO 80225
Office address:
Denver Federal Center, Bldg. 25
Lakewood
Telephone: (303) 234-3661; FTS 234-3661
Office hours: 8:00 a.m. to 4:30 p.m. Mountain Time
DISTRICT OFFICES
ARKANSAS
Address:
District Chief, WRD
U.S. Geological Survey
Federal Office Bldg., Rm. 2301
700 West Capitol Avenue
Little Rock, AR 72201
Telephone: (501) 378-6391; FTS 740-6391
Office hours: 7:30 a.m. to 4:00 p.m. Central Time
COLORADO
Mailing address:
District Chief, WRD
U.S. Geological Survey
Mail Stop 41 5, Box 25046
Denver Federal Center
Lakewood, CO 80225
Office address:
Denver Federal Center, Bldg. 53
Lakewood
Telephone: (303) 234-5092; FTS 234-5092
Office hours: 8:00 a.m. to 4:30 p.m. Mountain Time
IOWA
Mai/ing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 1230
Iowa City, IA 52244
Office address:
Federal Bldg., Rm. 269
400 South Clinton Street
Iowa City
Telephone: (319) 337-4191; FTS 863-6521
Office hours: 7:30 a.m. to 4:15 p.m. Central Time
KANSAS
Address:
District Chief, WRD
U.S. Geological Survey
1950 Avenue "A"-Campus West
University of Kansas
Lawrence, KS 66045
Telephone: (913) 864-4321; FTS 752-2300
Office hours: 8:00 a.m. to 4:30 p.m. Central Time
LOUISIANA
Mai/ing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 66492
Baton Rouge, LA 70896
Office address:
6554 Florida Boulevard
Baton Rouge
Telephone: (504) 389-0281; FTS 687-0281
Office hours: 7:30 a.m. to 4:30 p.m. Central Time
MISSOURI
Address:
District Chief, WRD
U.S. Geological Survey
1400 Independence Road, Mail Stop 200
Rolla, MO 65401
Telephone: (314)341-0824; FTS 277-0824
Office hours: 7:45 a.m. to 4:15 p.m. Central Time
MONTANA
Address:
District Chief, WRD
U.S. Geological Survey
Federal Bldg., Rm. 428
301 South Park Avenue
Drawer 10076
Helena, MT 59601
159
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MONTANA—Continued
Telephone: (406) 559-5263; FTS 585-5263
Office hours: 7:45 a.m. to 4:30 p.m. Mountain Time
NEBRASKA
Address:
District Chief, WRD
U.S. Geological Survey
Federal Bldg. and U.S. Court House, Rm. 406
100 Centennial Mall N.
Lincoln, NE 68508
Telephone: (402) 471-5082; FTS 541-5082
Office hours: 7:45 a.m. to 4.30 p.m. Central Time
NEW MEXICO
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 26659
Albuquerque, NM 87125
Office address:
Western Bank Bldg., Rm. 815
505 Marquette, NW
Albuquerque
Telephone: (505) 766-2246; FTS 474-2246
Office hours: 7:45 a.m. to 4:45 p.m. Mountain Time
NORTH DAKOTA
Address:
District Chief, WRD
U.S. Geological Survey
821 East Interstate Avenue
Bismarck, ND 58501
Telephone: (701) 255-4011, ext. 601; FTS 783-4601
Off ice hours: 8:00 a.m. to 5:00 p.m. Central Time
OKLAHOMA
Address: »
District Chief, WRD
U.S. Geological Survey
215 NW 3d Street, Rm. 621
Oklahoma City, OK 73102
Telephone: (405) 231-4256; FTS 736-4256
Off ice hours: 8:00 a.m. to 4'45 p.m. Central Time
SOUTH DAKOTA
Address:
District Chief, WRD
U.S. Geological Survey
Federal Bldg., Rm. 317
200 4th Street, SW
Huron, SD 57350
Telephone: (605) 352-8651,
ext. 258, FTS 782-2258
Office hours: 8:00 a.m. to 5.00 p.m. Central Time
TEXAS
Address:
District Chief, WRD
U.S. Geological Survey
Federal Bldg., Rm. 649
300 East 8th Street
Austin, TX 78701
Telephone: (512) 397-5766; FTS 734-5766
Office hours: 7:45 a.m. to 4:30 p.m. Central Time
UTAH
Address:
District Chief, WRD
U.S. Geological Survey
Administration Bldg., Rm. 1016
1745 West 1700 South
Salt Lake City, UT 84104
Telephone: (801) 524-5663; FTS 588-5663
Office hours: 8:00 a.m. to 4.30 p.m. Mountain Time
WYOMING
Mailing address:
District Chief, WRD
U.S. Geological Survey
P.O. Box 1125
Cheyenne, WY 82001
Office address:
J.C. O'Mahoney Federal Center, Rm. 5017
2120 Capitol Avenue
Cheyenne
Telephone: (307) 778-2220, ext. 21 53; FTS 328-21 53
Office hours: 8:00 a.m. to 4.30 p.m. Mountain Time
160
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REGION
Alaska, Arizona, California, Guam, Hawaii, Idaho, Nevada, Oregon, Washington
OFFICE OF THE REGIONAL HYDROLOGIST
Address:
Regional Hydrologist
U.S. Geological Survey
345 Middlefield Road, Mail Stop 66
Menlo Park, CA 94025
Telephone: (415) 323-8111, ext. 2337; FTS 467-2337
Office hours: 7:45 a.m. to 4:1 5 p.m. Pacific Time
DISTRICT OFFICES
ALASKA HAWAII—Continued
Address: Telephone: (808) 546-8331; FTS 556-0220,
District Chief, WRD ask gtor f 546.333,
U.S. Geological Survey K
733 West 4th Avenue, Suite 400 Office hours: 7:45 a.m. to 4:1 5 p.m. Alaska-Hawaii Time
Anchorage, AK 99501 ,P»AIJ«
Telephone: (907) 271-4138; FTS 399-0150, IDAHO
ask operator for 271 -4138 Address:
Office hours: 7:45 a.m. to 4:15 p.m. Alaska-Hawaii Time District Chief, WRD
ARIZONA U.S. Geological Survey
Address: Box 036, Federal Bldg., Rm. 365
District Chief, WRD 550 West Fort Street
U.S. Geological Survey
Federal Bldg., 301 West Congress Street Boise' ID 83724
Tucson, AZ 85701 Telephone: (208) 334-1750; FTS 554-1 750
Telephone: (602) 792-6671; FTS 762-6671 Office hours: 7.45 a.m. to 4:15 p.m. Mountain Time
Office hours: 8:00 a.m. to 4:30 p.m. Mountain Time
CALIFORNIA NEVADA
Address: Address:
District Chief, WRD District Chief, WRD
U'S- Geol°9'cal SurveV
94025 Federal Bld9- Rm- 227- 705 North Plaza Street
Telephone: (415) 323-8111, ext. 2326; FTS 467-2326 Carson City, NV 89701
Off ice hours: 7:45 a.m. to 4:15 p.m. Pacific Time Telephone: (702) 882-1388; FTS 470-5911,
_..,.._ , ,. .. ask operator for 882-1388
GUAM See also Hawaii ; „,.,..
Mailing address' Office hours: 7:45 a.m. to 4:45 p.m. Pacific Time
Hydrologist-ln-Charge OREGON
Subdistrict Office, WRD ..... ,.
,, o ,- , • ,o Mailing address:
U.S. Geological Survey y
P.O. Box188 District Chief, WRD
FPO San Francisco, CA 96630 U-S- Geological Survey
Office address: P.O. Box 3202
U.S. Navy Public Works Center, Bldg. 104 Portland, OR 97208
Agana, GU 96910 Office address:
Telephone: 339-9123 (commercial operator for overseas 830 N.E. Holladay Street
call) Portland, OR 97232
Office hours: 7:45 a.m. to 4:15 p.m. Kilo Time Telephone: (503) 231-2009, FTS 429-2009
_ _. . Off ice hours: 7:30 a.m. to 4:15 p.m. Pacific Time
HAWAII Hawaii—Guam District
Mailingaddress: WASHINGTON
Disf Met Chief, WRD Address:
U.S. Geological Survey District Chief, WRD
P.O. Box 50166 U.S. Geological Survey
Honolulu, HI 96850 1201 Pacific Avenue, Suite 600
Office address: Tacoma, WA 98402
300 Ala Moana Boulevard, Rm. 6110 Telephone: (206) 593-6510; FTS 390-6510
Honolulu Office hours: 7:45 a.m. to 4:30 p.m. Pacific Time
161
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•O
162
* U.S. GOVERNMENT PRINTING OFFICE 1980 O- 34I-6U'I75
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APPENDIX C
EPA Interim Primary Drinking Water Standards
Parameter Maximum level (mg/1)
Arsenic 0.05
Barium 1.0
Cadmium 0.01
Chromium 0.05
Fluoride 1.4-2.4
Lead 0.05
Mercury 0.002
Nitrate (as N) 10
Selenium 0.01
Silver 0.05
Endrin 0.0002
Lindane 0.004
Methoxychlor 0.1
Toxaphene 0.005
2,4-D 0.1
2,4,5-TP Silvex 0.01
Radium 5 pCi/1
Gross Alpha 15 pCi/1
Gross Beta 4 millirem/yr
Turbidity 1/TU
Coliform Bacteria 1/100 ml
(Comment; Turbidity is applicable only to surface water supplies)
163
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Appendix D EPA 600/4-81-056
TOTAL ORGANIC HALIDE(TOX)
Adapted From
Method 450.1
Interim
U S. Environmental Protection Agency
Office of Research and Development
Environmental Monitoring and Support Laboratory
Physical and Chemical Methods Branch
Cincinnati, Ohio 45268
November 1980
165
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TOTAL ORGANIC HALIDE (TOX)
Method 450.1
1. Scope and Application
1.1 This method for the determination of Tbtal Organic Halides as Cl~
by carbon adsorption specifies that all samples be run at least
in duplicate. Under conditions of duplicate analysis, the reliable
limit of sensitivity is 5 jag/L. Organic halides as used in this
method are defined as all organic species containing chlorine,
bromine and iodine that are adsorbed by granular activated carbon
under the conditions of the method. Fluorine containing species
are not determined by this method.
1.2 This is a microcoulometric-titration detection method applicable
to the determination of the compound class listed above in drinking
and ground waters.
1.3 This method is provided as a recommended procedure. It may be
used as a reference for comparing the suitability of other methods
thought to be appropriate for measurement of TOX (i.e., by
comparison of sensitivity, accuracy and precision data).
1.4 This method should be used or supervised by analysts experienced
in the operation of a pyrolysis/microcoulometer and in the
interpretation of the results.
2. Summary of Method
2.1 A sample of water that has been protected against the loss of
volatiles by the elimination of headspace in the sampling container,
and is free of undissolved solids, is passed through a column
containing 40 mg of activated carbon. The column is washed
166
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to remove any trapped inorganic halides, and is then pyrolyzed to
convert the adsorbed organohalides to a titratable species that can
be measured by a microcoulometric detector.
Interferences
3.1 Method interferences may be caused by contaminants, reagents,
glassware, and other sample processing hardware. All of these
materials must be routinely demonstrated to be free from
interferences under the conditions of the analysis by running
method blanks.
3.1.1 Glassware must be scrupulously cleaned. Clean all glassware
as soon as possible after use by treating with chromate
cleaning solution. This should be followed by detergent
washing in hot water. Rinse with tap water and distilled
water, drain dry, and heat in a muffle furnace at 400°C
for 15 to 30 minutes. Volumetric ware should not be heated
in a muffle furnace. Glassware should be sealed and stored
in a clean environment after drying and cooling, to prevent
any accumulation of dust or other contaminants.
3.1.2 The use of high purity reagents and gases help to minimize
interference problems.
3.2 Purity of the activated carbon must be verified before use. Only
carbon samples which register less than 1000 ng/40 mg should be
used. The stock of activated carbon should be stored in its
granular form in a glass container with a Teflon seal. Exposure to
the air must be minimized, especially during and after milling and
sieving the activated carbon. No more than a two-week supply
167
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should be prepared in advance. Protect carbon at all times from
all sources of halogenated organic vapors. Store prepared carbon
and packed columns in glass containers with Teflon seals.
3.3 This method is applicable to samples whose inorganic-halide
concentration does not exceed the organic-halide concentration by
more than 20,000 times.
X
4. Safety
The toxicity or carcinogenicity of each reagent in this method has not
been precisely defined; however, each chemical compound should be
treated as a potential health hazard. From this viewpoint, exposure to
these chemicals must be reduced to the lowest possible level by whatever
means available. The laboratory is responsible for maintaining a
current-awareness file of OSHA regulations regarding the safe handling
of the chemicals specified in this method. A reference file of
material-handling data sheets should also be made available to all
personnel involved in the chemical analysis.
5. Apparatus and Materials (All specifications are suggested. Catalog
numbers are included for illustration only).
5.1 Sampling equipment, for discrete or composite sampling
5.1.1 Grab-sample bottle - Amber glass, 250-mL, fitted with
Teflon-lined caps. Foil may be substituted for Teflon if
the sample is not corrosive. If amber bottles are not
available, protect samples from light. The container must
be washed and muffled at 400°C before use, to minimize
contamination.
168
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5.2 Adsorption System
5.2.1 Dohrmann Adsorption Module (AD-2), or equivalent,
pressurized, sample and nitrate-wash reservoirs.
5.2.2 Adsorption columns - pyrex, 5 cm long X 6-mm OD X 2-mm ID.
5.2.3 Granular Activated Carbon (GAC) - Filtrasorb-400,
Calgon-APC, or equivalent, ground or milled, and screened to
a 100/200 mesh range. Upon combustion of 40 mg of GAC, the
apparent-halide background should be 1000-mg Cl~
equivalent or less.
5.2.4 Cerafelt (available from Johns-Manville), or equivalent -
Form this material into plugs using a 2-mm ID
stainless-steel borer with ejection rod (available from
Dohrmann) to hold 40 mg of GAC in the adsorption columns.
CAUTION: Do not touch this material with your fingers.
5.2.5 Column holders (available from Dohrman).
5.2.6 Volumetric flasks - 100-mL, 50-mL.
A general schematic of the adsorption system is shown in
Figure 1.
5.3 Dohrmann microcoulometric-titration system (MCTS-20 or DX-20), or
equivalent, containing the following components:
5.3.1 Boat sampler.
5.3.2 Pyrolysis furnace.
5.3.3 Microcoulometer with integrator.
5.3.4 Titration cell.
A general description of the analytical system is shown in
Figure 2.
5.4 Strip-Chart Recorder.
169
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6. Reagents
6.1 Sodium sulfite - 0.1 M, ACS reagent grade (12.6 g/L).
6.2 Nitric acid - concentrated.
6.3 Nitrate-Wash Solution (5000 mg NO^/L) - Prepare a nitrate-wash
solution by transferring approximately 8.2 gm of potassium nitrate
into a 1-litre volumetric flask and diluting to volume with reagent
water.
6.4 Carbon dioxide - gas, 99.956 purity.
6.5 Oxygen - 99.9% purity.
6.6 Nitrogen - prepurified.
6.7 70% Acetic acid in water - Dilute 7 volumes of acetic acid with 3
volumes of water.
6.8 Trichlorophenol solution, stock (1 uL = 10 ug Cl") - Prepare a
stock solution by weighing accurately 1.856 gm of trichlorophenol
into a 100-mL volumetric flask. Dilute to volume with methanol.
6.9 Trichlorophenol solution, calibration (1 uL = 500 ng Cl~) -
Dilute 5 mL of the trichlorophenol stock solution to 100 ml with
methanol.
6.10 Trichlorophenol standard, instrument-calibration - First, nitrate
wash a single column packed with 40 mg of activated carbon as
instructed for sample analysis, and then inject the column with
10 uL of the calibration solution.
6.11 Trichlorophenol standard, adsorption-efficiency (100 yg C1~/L) -
Prepare a adsorption-efficiency standard by injecting 10 yL of
stock solution into 1 liter of reagent water.
6.12 Reagent water - Reagent water is defined as a water in which an
170
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interferent is not observed at the method detection limit of each
parameter of interest.
6.13 Blank standard - The reagent water used to prepare the calibration
standard should be used as the blank standard.
7. Calibration
7.1 Check the adsorption efficiency of each newly-prepared batch of
carbon by analyzing 100 ml of the adsorption-efficiency standard,
in duplicate, along with duplicates of the blank standard. The net
recovery should be within 5% of the standard value,
7.2 Nitrate-wash blanks (Method Blanks) - Establish the repeatability
of the method background each day by first analyzing several
nitrate-wash blanks. Monitor this background by spacing nitrate-
wash blanks between each group of eight pyrolysls determinations.
7.2.1 The nitrate-wash blank values are obtained on single columns
packed with 40 mg of activated carbon. Wash with the
• 9 r" .
• nitrate solution as instructed for sample analysis, and then
pyrolyze the carbon.
7.3 Pyrolyze duplicate instrument-calibration standards and the blank
standard each day before beginning sample analysis. The net
response to the calibration-standard should be within 3% of the
calibration-standard value. Repeat analysis of the
instrument-calibration standard after each group of eight pyrolysis
determinations, and before resuming sample analysis after cleaning
or reconditioning the titration cell or pyrolysis system.
8. Sample Preparation
8.1 Special care should be taken in the handling of the sample to
171
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minimize the loss of volatile organohalides. The adsorption
procedure should be performed simultaneously on ail replicates
8.2 Reduce residual chlorine by the addition of sulfite (1 ml of 0.1 M
per liter of sample). Addition of sulfite should be done at the
time of sampling if the analysis is meant to determine the TOX
concentration at the time of sampling. It should be recognized
that TOX may increase on storage of the sample. Samples should be
stored at 4°C without headspace.
8.3 Adjust pH of the sample to approximately 2 with concentrated HNOj
just prior to adding the sample to the reservoir.
9. Adsorption Procedure
9.1 Connect two columns in series, each containing 40 mg of
100/200-mesh activated carbon.
9.2 Fill the sample reservoir, and pass a metered amount of sample
through the activated-carbon columns at a rate of approximately
3 mL/min. NOTE: 100 ml of sample is the preferred volume for
concentrations of TOX between 5 and 500 ug/L; 50 ml for 501 to 1000
ug/L, and 25 ml for 1001 to 2000 ug/L.
9.3 Wash the columns-in-series with 2 ml of the 5000-mg/L nitrate
solution at a rate of approximately 2 mL/min to displace inorganic
chloride ions.
10. Pyrolysis Procedure
10.1 The contents of each column is pyrolyzed separately. After rinsing
with the nitrate solution, the columns should be protected from the
atmosphere and other sources of contamination until ready for
further analysis.
172
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10.2 Pyrolysis of the sample is accomplished in two stages. The
volatile components are pyrolyzed in a C02-rich atmosphere at a
low temperature to assure the conversion of brominated
trihalomethanes to a titratable species. The less volatile
components are then pyrolyzed at a high temperature in an (L-rich
atmosphere.
NOTE: The quartz sampling boat should have been previously muffled
at 800°C for at least 2 to 4 minutes as in a previous analysis,
and should be cleaned of any residue by vacuuming.
10.3 Transfer the contents of each column to the quartz boat for
individual analysis.
10.4 If the Dohrmann MC-1 is used for pyrolysis, manual instructions are
followed for gas flow regulation. If the MCT-20 is used, the
information on the diagram in Figure 3 is used for gas flow
regulation.
"' '* n
10.5 Position the sample for 2 minutes-in the 200 C zone of the
pyrolysis tube. For, the MCTS-20, the boat is positioned just
outside the furnace entrance.
10.6 After 2 minutes, advance the boat into the 800°C zone (center) of
the pyrolysis furnace. This second and final stage of pyrolysis
may require from 6 to 10 minutes to complete.
11. Detection
The effluent gases are directly analyzed in the microcoulometric-titra-
tion cell. Carefully follow manual instructions for optimizing cell
performance.
173
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12. Breakthrough
Because the background bias can be of such an unpredictable nature, it
can be especially difficult to recognize the extent of breakthrough of
organohalides from one column to another. All second-column
measurements for a properly operating system should not exceed
10-percent of the two-column total measurement. If the 10-percent
figure is exceeded, one of three events can have happened. Either the
first column was overloaded and a legitimate measure of breakthrough was
obtained - in which case taking a smaller sample may be necessary; or
channeling or some other failure occurred - in which case the sample may
need to be rerun; or a high, random, bias occurred and the result should
be rejected and the sample rerun. Because knowing which event has
occurred may not be possible, a sample analysis should be repeated often
enough to gain confidence in results. As a general rule, any analyses
that is rejected should be repeated whenever sample is available. In
the event that the second-column measurement is equal to or less than
the nitrate-wash blank value, the second-column value should be
disregarded.
13. Quality Control
13.1 Before performing any analyses, the analyst must demonstrate the
ability to generate acceptable accuracy and precision with this
procedure by the analysis of appropriate quality-control check
samples.
13.2 The laboratory must develop and maintain a statement of method
accuracy for their laboratory. The laboratory should update the
accuracy statement regularly as new recovery measurements are made.
174
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13.3 It is recommended that the laboratory adopt additional
quality-assurance practices for use with this method. The specific
practices that would be most productive will depend upon the needs
of the laboratory and the nature of the samples. Field duplicates
may be analyzed to monitor the precision of the sampling
technique. Whenever possible, the laboratory should perform
analysis of standard reference materials and participate in
relevant performance-evaluation studies.
14. Calculations
OX as Cl" is calculated using the following formula:
(cr c3) + (c2 - c3 ) m vg/l Total Organ1c Halide
where:
C-, = ug Cl" on the first column in series
Cg = ug Cl" on the second column in series
C3 = predetermined, daily, average, method-blank value
(nitrate-wash blank for a 40-mg carbon column)
V = the sample volume in L
15. Accuracy and Precision
These procedures have been applied to a large number of drinking-water
samples. The results of these analysis are summarized in Tables I and
II.
16. Reference
Dressman, R., Najar, 6., Redzikowski, R., paper presented at the
Proceedings of the American Water Works Association Water Quality
Technology Conference, Philadelphia, Dec. 1979.
175
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TABLE I
PRECISION AND ACCURACY DATA FOR MODEL COMPOUNDS
Model
Compound
CHC13
CHBrCl2
CHBr2Cl
CHBr3
Pentachlorophenol
Dose Dose
jug/L as ;ug/L Cl
98 88
160 106
155 79
160 67
120 80
Average Standard
% Recovery Deviation
89 Ifc
98 9
86 11
111 8
93 9
No. of
Replicates
10
11
13
11
7
TABLE II
Sanple
A
B
C
PRECISION DATA
Avg. halide
ug Cl/L
71
9U
191
ON TAP WATER ANALYSIS
Standard
Deviation
fc-3
7.0
6.1
No. of
Replicates
8
6
U
179
-------
TABLE I
PRECISION AND ACCURACY DATA FOR MODEL COMPOUNDS
Model
Compound
CHC13
CHBrCl2
CHBr2Cl
CHBr3
Pe ntachl orophenol
Dose Dose
Aig/L asjag/L Cl %
98 88
160 106
155 79
160 67
120 80
TABLE
Average Standard
Recovery Deviation
89 Ik
98 9
86 11
111 8
93 9
II
No. of
Replicates
10
11
13
11
7
PRECISION DATA ON TAP WATER ANALYSIS
Sample
A
B
C
Avg. halide
ug Cl/L
71
9^
191
Standard
Deviation
k.3
7.0
6.1
No. of
Replicates
8
6
k
179
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