Presentation of the New Mexico Environment Department (NMED)
TECHNICAL TESTIMONY OF DAVID MARTIN WALKER; March 22, 1999.
Mr. Walker received a B. S. in Geological Engineering, University of
Missouri-Rolla. Mr. Walker is a registered professional engineer. He has
over 15 years of expertise in RCRA permitting, emphasizing facility
engineering and corrective action. Mr. Walker has conducted RCRA Part B
permit review and analyses, RCRA Closure and Post-Closure Plan reviews, and
RCRA Facility Investigation workplans and report reviews for numerous
facilities, and has managed the implementation and oversight of all phases
of field activities related to these reviews. Mr. Walker currently manages
several large-scale RCRA Corrective Action projects. He has presented
Corrective Action training to several EPA Regions. With respect to WIPP,
Mr. Walker has supported the EPA Office of Solid Waste (OSW) on both the
WIPP Test and Disposal Phase No Migration Variance Petitions, the EPA
Office of Radiation and Indoor Air (ORIA) on the WIPP Compliance
Certification Application review, and the NMED on the WIPP Test Phase and
Disposal Phase permits applications.
Currently, Mr. Walker is a member of the NMED WIPP Support Program for
Techlaw. Techlaw is the technical consultant for the NMED on the Applicant's Permit.
CONFIRMATORY VOC MONITORING PROGRAM
The purpose of the Confirmatory VOC Monitoring Program is to measure the
concentrations of 9 VOCs of concern that could be released into the air
from the operations at WIPP. [The 9 VOCs of concern are carbon
tetrachloride; chlorobenzene; chloroform; 1, 1-dichloroethene; 1,
2-dichloroethane; methylene chloride; 1, 1 ,2, 2-tetrachloroethane;
toluene; and 1, 1, 1-trichloroethane.]
Thirty days after the final Permit is issued, the Confirmatory VOC
Monitoring Program must start. The Program will continue through the
operational phase. Typically VOCs are cleaning solvents or carrier
chemicals for compounds like paint. VOCs volatilize easily, allowing for
The total individual risk due to VOC exposure should not exceed certain
acceptable risk levels. The NMED calculated the risk for both carcinogenic
and non-carcinogenic VOCs for 2 receptors: a resident who lives at the
site boundary and a WIPP non-waste surface worker.
The carcinogenic total individual excess cancer risk should not exceed 1 x
10-6 [0.000001] for the resident, and 1 x 10-5 [0.00001] for the non-waste
surface worker. Non-carcinogenic acceptable risk level for both is the
same and should not exceed 1.0 according to the hazard index.
The source of the VOC gases in the waste drums will probably be rags,
soils, etc. contaminated by cleaning solvents or carrier chemicals for
compounds like paint. The contaminants evaporate and become VOCs. The
VOCs concentrate in the headspace of the drum.
VOCs get entrained into the air in open and closed rooms. Open rooms have
mine ventilation airflow. Most of the time workers are upstream of the
airflow. VOCs in the open rooms will also flow out into the exhaust drift.
In closed rooms there will be no ventilation. The pressure of the VOCs
will equalize to that of the average headspace gases in the closed room.
The "creep" of the salt will reduce the volume of the closed room, thus
increasing the pressure. This will lead to an "effective" gas generation
rate. In the closed rooms, the pressure will push the gases through the
ventilation barriers, and eventually the gases will end up in the exhaust
drift. Closed Panels are similar to closed rooms. The VOC concentrations
will equalize to the average headspace gases in the whole panel. Again,
the pressure will push the gases through the panel closure systems. Gases
from the Closed Panels will enter into the E-300 or Exhaust Drift
The average measured gas concentration limits in all of the containers in
the room or panel are established through risk assessment. For the
maximally exposed individual, the maximum concentrations should not exceed
the acceptable risks described above. Worker risk is one order of
magnitude greater than public risk because the NMED balanced occupational
exposure of employees with the fact that workers during normal operations
are covered under Occupational Safety and Health Administration (OSHA) and
Mining Safety and Health Administration (MSHA) regulations. Usually
occupational exposure is not taken into consideration under RCRA.
The non-waste surface workers would get the greatest chronic dose because
they could be in the vicinity of the exhaust shaft outlet. The NMED may
also include employees at greater risk because of health, age, etc. than
the standards set by OSHA. [Such standards are usually based on the
results of studies of young, healthy, white, male medical students.]
However, the potential of underground workers to get a large acute dose
during a roof-fall cannot be discounted. The NMED used equations,
assumptions and models from Appendix D9 of the 6.3 revision of the
Application to calculate potential doses from a roof-fall. However, the
NMED lowered the DOE's assumed mine ventilation rate to better replicate
actual conditions and changed the reference for 1, 1, 1-trichloroethylene.
Limitations must be set for total risk for all carcinogenic and
non-carcinogenic VOCs. Once the risk is set, back-calculations reveal how
high the limits could be without exceeding the environmental performance
levels. The initial set of concentration limits was changed in the second
1. Chlorobenzene and tuolene: The initial limits had to be reduced to
ensure a closed room limit would not exceed lower explosive limits (LEL).
A roof-fall, a spark, or static electricity could cause an explosion or
fire. LELs are set for 6 of the 9 VOCs.
2. Methylene chloride: The limit was raised in the second draft
Permit. The first draft Permit had set the concentration limits below the
risk and LEL limits.
3. 1, 1, 1-trichloroethylene and 1, 1-dichloroethylene: The first
draft Permit [?] set the concentration below the limits to ensure that the
IDLH (Immediately Dangerous to Life and Health) limits would not be
exceeded in an open room under a roof fall scenario. The DOE's Application
said the potential for a roof-fall in Panel 1 prior to or during waste
emplacement was 1/100 to 1/1000 [1 x 10 2 or 1 x 10 3].
OPEN ROOM ROOF-FALL
In the open room roof-fall scenario, the biggest problem is the roof
falling onto the waste drums resulting in crushed and broken waste drums.
This scenario would render the assumption that VOCs diffuse through filter
vents invalid. However, the increased concentration of VOCs under this
scenario would not last long because the fresh air in the ventilation
system would flush them out.
CLOSED ROOM ROOF-FALL.
The VOC concentrations in the closed room air are the averages of all the
drum headspace gases. Ninety percent will flow into the void of the roof
fall. Ten percent will blow through the ventilation barriers--5% on each
side, so a worker would get a 5% dose. The release of VOCs from a closed
room roof-fall is the limiting case. This is the reasoning behind why the
limits for 1,1,1 trichloroethylene were lowered.
An error was made in worker exposure calculations, and the concentration
for carbon tetrachloride went from long-term risk to the IDLH limit which
is why the limit was reduced (though not by much). Limits for all are
based on apportioning the carcinogenic and non-carcinogenic risks equally
to keep from exceeding all risk limits.
CONFIRMATORY MONITORING PROGRAM
There are no specific RCRA regulations addressing this. The groundwater
compliance analysis program seemed the most similar, since both regulate
known releases from miscellaneous units to the environment. There are 2
monitoring locations (stations), Station VOC A and Station VOC B. Both
will be in the E-300 exhaust ventilation drift. Station VOC A stays in the
same place. It is upstream of Panel 1, and its location changes in such a
way that it is always upstream of the active panel. It monitors the
The monitoring program will operate during the entire Operational Phase.
Samples are taken twice a week and limits are based on the long-term risk.
Minor changes over the short term will not cause problems. Several
assumptions are used when calculating risks. The gas generation rate in a
closed room is a key assumption. There are other assumptions, too. Without
a continuous monitoring program, you could not comply with the limitations
in the Permit. The monitoring program confirms that the assumptions used
Samples are analyzed using gas chromatography mass spectrometry (GCMS) and
are analyzed at EPA contract labs. Grab samples and integrated samples can
be taken over time. The contract labs allow the detection of low levels of
DATA EVALUATION AND REPORTING
Certain conditions were assumed when the concentration limits were set.
These assumptions are:
1. The ventilation was assumed to be 260,000 standard cubic
2. The ventilation at Station VOC A in the E-300 Drift was
assumed to be 130,000 standard cubic feet/minute; and
3. The VOC concentrations at Station VOC B are subtracted from
those at Station VOC A.
This data evaluation and reporting process yields the VOC emission
concentrations from the Hazardous Waste Disposal Units (HWDUs) themselves.
Atypical conditions are expected to occur and do not necessarily indicate
there is a problem. But changes in mine ventilation rates, for instance,
can affect the calculations. A much higher ventilation rate can dilute the
concentrations. The overall ventilation rate, the rate in the E-300 drift,
as well as the temperature and pressure must be measured. The data must be
normalized to standard conditions. There is an equation in Appendix N of
the Draft Permit that will be applied to data gathered from Station VOC A
and Station VOC B. The normalized concentrations are taken as Station VOC
B and subtracted from the normalized concentrations from Station VOC A.
This calculation reveals the VOC emissions coming from the HWDUs.
These concentrations are compared to the concentration of concern, which is
calculated to limits at the top of the exhaust shaft and is also related to
Station VOC A concentrations. When the concentration limits are set, the
assumptions are that there are 9 closed panels full of waste and 1 open
panel full of waste and that the headspace gas concentrations in each
container are equal to the concentration limits found in Table IV.D.1. You
then take the exhaust shaft calculation and back-calculate to the Station
VOC A concentrations of concern.
If VOC emissions exceed the concentrations of concern, the DOE must notify
the NMED within 5 days. If the VOC emissions exceed the concentrations of
concern, a running annual average (the average for the previous 12 months)
is calculated. If the running annual average exceeds the concentration of
concern once disposal has ceased, the room is closed and ventilation
barriers are installed in the room. If the running annual average exceeds
the concentration of concern for 6 months, the entire panel is closed, and
the panel closure system is then installed.
HIGHLIGHTS OF CROSS-EXAMINATION OF DAVID WALKER
There are no specific OSHA standards for waste and non-waste surface
workers, but the standards are specific for hazardous waste workers. OSHA
standards are not necessarily the only standards that apply.
The assumption that the roof will fall even with roof supports is
conservative. An extra margin of safety beyond conservative assumptions is
The non-waste surface worker is the human receptor with the largest
potential chronic dose. There are no occupied buildings within 120 feet
from the exhaust shaft outlet, so using that location is a conservative
assumption. This is based on air modeling, which determined that the
highest air dispersion factor was at the location where the VOCs are least
Mr. Walker was not aware that all workers at WIPP have to pass a fitness
The NMED wants language in the Permit to require the DOE to require hourly
reporting of ventilation rates. This is a new condition and is not
included in the revised draft Permit now. This condition addresses
comments by the DOE to the effect that they want more flexibility for the
mine ventilation rate. It is possible that reporting only changes instead
of the hourly log might be sufficient and the NMED concurs that there is a
need for flexibility here. But there is not enough information in the
Application on how the DOE would measure and record the ventilation rate.
The revised draft Permit does not prohibit non-workers from being
underground or on the surface. Exposures for non-workers (visitors) are
not included in the draft permit and they are not included in the risk
assessment. If certain OSHA and MSHA requirements that apply to WIPP are
changed, the revised draft Permit requirements do not necessarily change
too. The concentration limits, especially for the underground workers, are
based on not exceeding the Immediately Dangerous to Life and Health (IDLH)
limits, which is a National Institute of Occupational Safety and Health
In the open room roof-collapse scenario, the assumption is that 21 drums
will fall and breach. There have not been any studies to determine how
many drums would actually be breached. Appendix D-9, which refers to the
1995 Safety Analysis Report, is the basis for the 21-drum assumption. In
an open room there could actually be up to 11,000 drums. The roof-fall
scenarios also assume that backfill will be used.
Another assumption is that each drum will be vented. However, there are no
studies on how often vents fail to function normally. If a drum is visible
and the vent is clogged, the drum would appear to be bulging. But most
drums will not be visible in the underground due to stacking and the lack
of aisle space. Mr. Walker would not be surprised to find out that there
have been occasions when drum vents have failed to work or were blocked.
In an open room roof-fall containing waste drums, hazardous as well as
radioactive gases and particles would be released. In a closed room
roof-fall, however, Mr. Walker is not as convinced that a non-gaseous
release would occur due to the ventilation barrier. The waste drums in a
closed room are assumed to be breached already.
The test phase Permit (1993) required supplementary roof supports, but the
revised draft Permit does not. The roof supports were necessary for the
test phase so that the rooms would remain open.
The VOC risk at the Land Withdrawal Act boundary should be 1 part per
million. Emissions from WIPP would be both radioactive and VOCs. The
radioactive component of that release would come under a different set of
regulations. Any radioactive exposures to the boundary resident are in
addition to what the NMED has calculated. The NMED did not consider the
carcinogenic risk from the radioactive releases for the boundary resident.
In order to account for background concentrations of hazardous
constituents, the EPA has set acceptable limits for total additive
exposures to individual compounds that are targets. The rates are set at
conservative limits already (1 x 10-6). The limits account for all sources
to which the receptor might be exposed. However, the cumulative and
possible synergistic effects of radioactive exposures are not included in
these total additive exposure limits.
The underground waste workers are not the limiting case for long-term
exposure. It is assumed that the underground waste workers are downstream
for only 33 hours/year. The non-waste surface workers are assumed to be
downstream from the exhaust air from the WIPP underground for 1,920
hours/year. This is not a conservative assessment, but it is appropriate.
A more detailed explanation of the rationalization for this will be given
in reply to the comments later. Also, no long-term risk assessment was
done for the underground worker because the OSHA standards cover this
worker during normal operations.
The NMED did a deterministic risk assessment analysis, but not a
probabilistic risk assessment analysis. A roof-fall was assumed to occur
and the RCRA consequences were analyzed. A one in one hundred (1/100)
chance of a roof-fall is a high probability. However, the risk assessment
was based on assumptions for long term releases and effects. A roof-fall
would increase VOC concentrations, but this would not be a problem over the
long term. The NMED used the assumptions in Attachment 1 of Appendix D-9
of the DOE's Application, including the assumptions about the total dynamic
loading on the drums and the type of drum used. However, the robustness of
the drums is only a factor in an open room because, in a closed room it is
assumed that the VOCs are already equalized to the headspace concentrations
of the drums. The NMED did not take into account the irregularities of the
salt and the hundreds of roof bolts supporting the roof. It was assumed
that there would be no breaching of containers behind the face of the waste
stack. It is possible that up to 60 waste drums could be breached and the
performance standard could still be met. Beyond that, it would be
necessary to reanalyze. Appendix D-9 of the DOE's Application also assumes
the waste is arranged in 7-packs, stacked three high and does not take into
account a different container, such as a standard waste box in the
analyses. [A 7-pack is a circular arrangement of 6 drums around a center
Bulging drums are not taken into account in the accident scenarios. Out of
11,000 drums arranged in 7-packs, it would be impossible to see which ones
are bulging. [It is estimated that there will be 11,000 waste drums in
each room.] There is no requirement in the Permit to inspect the waste
drums once they are emplaced. Scenarios in which either the ventilation
bulkheads or the ventilation barriers are crushed by roof-falls have not
The overall purpose of the VOC monitoring program is to determine if the
assumptions in the risk assessment are correct. If the assumptions change,
the limits could change also.
Volatile radioactive off-gassings are not considered in the calculations
because such off-gassings are not regulated by RCRA. The VOC lower
explosive limits (LEL) are based on hazardous constituents in a closed room
and on another set of regulations relating to the potential for fire and
explosion in the underground.
A roof-fall accident leading to a short-term increase in VOC emissions is
not likely to have an acute effect at the ground surface, though this
accident was not analyzed. VOCs will be diluted once they exit the exhaust
shaft. There will not be any aboveground VOC monitoring.
VOC samples are analyzed at the WIPP on-site lab and or at a suitable
contract lab. If the on-site lab is used, duplicate samples from each
station will be collected and 10% of those samples will also be analyzed at
an off-site lab.
Workers do not use any masks or breathing apparatus. This is an OSHA issue.
The NMED never calculated how many roof-falls there could be during the
life of the Permit. Effects are calculated only for a single short-term
event. The NMED is considering a re-evaluation of the number of drums that
could be breached in an open room roof-fall since there are 11,000 drums in
a room. All the calculations are based on theoretical modeling, not on
experiments based on the actual conditions at WIPP.
The effects of particulate hazardous metals are not addressed in any of the
calculations. If waste drums were burning and mercury (and possibly lead)
vapors were generated, these vapors would not be monitored.
If a room had to be closed because the VOC concentrations had exceeded the
running annual average and a new active room was opened, a situation could
occur where the new room would also exceed the running annual average. It
is unclear in the revised draft Permit, if during the 6-month period of
potential violation of the running annual average that could lead to the
closure of a Panel, how a succession of rooms might have to be closed.