United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R08-90/039
February 1990
SEPA
Superfund
Record of Decision
Rocky Mountain Arsenal
-------
REPORT DOCUMENTATION 11. REPORT NO. 2. 3. Reclplen1'8 Acceeeion No.
PAGE EPA/ROD/R08-90/039
l TlUe end SubdUe .'. 5. Reporl Dete
SUPERFUND RECORD OF DECISION 2/26/90
Rocky Mountain 'Arsenal (Operable Unit 19), CO
6.
Fourth Remedial Action .
7. Author(e) 8. Perlonnlng Orgeniz8tion Rep'- No.
8. "-'fonnlng Orgelniz8tion Name end Addreee 10. ProjecVTeeklWork Unit No.
11. Conlr8ct(C) or Grent(G) No.
IC)
(G)
12. Sp_oring Orgenize1Jon Name end Addreee 13. Type 01 Report & Period Covered
U,S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
1 S. Supplementery Notee
16. Abetrect (Umlt: 200 worde)
The Rocky Mountain Arsenal (RMA) (Operable Unit 19) site comprises part of the
l7,000-acre RMA site, which is a former U.S. Army chemical warfare and incendiary
munitions manufacturing and assembly plant in Adams County, Colorado. From the 1950s
until late 1969, the U.S. Army used the RMA facility to produce the nerve agent GB
(isopropylmethyl phosphonofluoridate). In addition, between 1947 and 1982, private
industries leased major portions of the plant facilities to manufacture various
insecticides and herbicides. Since 1970, facility operations primarily have involved
the destruction of chemical warfare materials. Because final remediation of the RMA
site will take many years to complete, thirteen Other Contamination Sources Interim
Response Actions (IRAs) were determined necessary prior to implementing the Final Onpost
Record of Decision (ROD). Operable Unit 19 (Rail Classification Yard) is one of the
areas included in the IRAs. In 1980, the pesticide 1,2-dibromo-3-chloropropane (DBCP)
was detected in the alluvial ground water near the Rail Classification Yard of RMA. To
prevent off-post migration of DBCP in the ground water, the Irondale Control System
(ICS) was installed in the Rail Classification yard in 1981. This system, which has
been effective in preventing off-post migration, involves pumping and treatment of
(See Attached Page)
17. Document Analyele L eelcrlptore
Record of Decision - Rocky Mountain Arsenal (Operable Unit 19), CO
Fourth Remedial Action
Contaminated Medium: gw
Key Contaminants: organics (pesticides)
II. IdentilierelOpen-Ended TerrM
c. COSA TI Reid/Group
18. Avellebilty Statement 18. Security CI..e (Thll Report) 21. No. of Pegee
None 106
20. Security CI..e (Thie Pege) ~ PrIce
Nnnp
NSI- .18 ~ \4-71)
50272.101
,
.
(See A
Z3g )
See InsuucUons on Reverse
(Formerty NTl5-35)
-------
EPA/ROD/R08-90/039
Rocky Mountain Arsenal
Fourth Remedial Action
(Operable Unit 19), CO
Abstract (Continued)
contaminated ground water followed by reinjection. Site investigations by the U.S. Army
indicate DBCP contamination in unsaturated soil and sediment, possibly from leaking rail
cars, to be potential sources of ground water contamination. This ROD addresses interim
management of migration of the contaminatectground water plume. The primary contaminant
of concern affecting the ground water is DBCP.
-
-
The selected interim remedial action for this site includes installing aground water
interception/containment system parallel to the contaminant flowpath: increasing the
treatment capacity of the ICS and constructing pipelines to convey extracted ground
water to the ICS: ground water pumping and treatment using carbon adsorption at the ICS
followed by reinjection: and conducting ground water monitoring. This interim remedial
action will be implemented jointly with the RMA motor pool area IRA. The estimated
present worth cost of this interim remedial action is $2,662,000, which includes an
annual O&M cost of $183,000 for five years.
PERFORMANCE STANDARDS OR GOALS: The chemical-specific goal for ground water treatment
of DBCP is 0.2 ug/1 based on the proposed MCL. Chemical-specific goals for other
potential contaminants are based on MCLs and Colorado Basic Standards for Ground Water
(CBSG) and include benzene 5 ug/l (MCL), toluene 2,420 ug/l (CBSG), and TCE 5 ug/l
-------
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FINAL DECISION DOCUMENT
FOR OTHER CONTAMINATION SOURCES
INTERIM RESPONSE ACTION
RAIL CLASSIFICATION YARD, RMA
Prepared by
MK-Environmental Services
Denver, Colorado 80203
Prepared for
Shell Oil/Holme Roberts & Owen
Denver, Colorado 80203
March 1990
,
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Mr. Connally Mears
U.S. Environmental Protection Agency
Region VITI
One Denver Place
Suite 801
999-18th Street
Denver, Colorado 80202-2405
Dear Mr. Mears:
Enclosed for your review are the Draft Final Decision Documents for the Motor
Pool and Railyard Interim Response Actions at Rocky Mountain Arsenal in accordance
with paragraph 22.9 of the Federal Facility Agreement (FF A).
oL..;
Following consideration of all comments received during the public comment period
from November 27, 1989 through December 27, 1989, the Army has revised the Decision
Documents for the Motor Pool and Railyard where appropriate.
In accordance with paragraph 22.10 of the FF A, Organizations with standing to
invoke the Dispute Resolution process should advise me and my counsel in writing by
the close of business February 26, 1990, if they wish to invoke the procedures for
Dispute Resolution. .
In accordance with paragraph 22.11 of the FF A, after the close of the period for
invoking Dispute Resolution, if Dispute Resolution is not invoked, or after completion
of Dispute Resolution, if invoked, the Army shall issue a final IRA Decision Document
to the other Organizations and Department of Interior. Unless Dispute Resolution is
invoked on or before February 26, 1990, the Army will consider the decisions in the
Draft. Final Decision Documents the final decision for the Motor Pool and/or the
Railyard Interim Response Action.
,;.~
~
Dj ~ J~
Donald L Campbell
Deputy Program Manager
-------
Copies Furnished:
Major Lawrence E. Rouse, Headquarters, Department of the Army,
ATfN: DAJA-ELL, Pentagon, Room lC480, Washington, D.C. 20310-2210
(wjencl)
Mr. Bradley Bridgewater, Acumenics Research and Technology, Inc., DOJ Litigation
Support, 999-18th Street, Suite 501, North Tower, Denver, Colorado 80202
(wjencl)
~. Mr. Bruce Ray, Assistant Regional Counsel, U.S. Environmental
Protection Agency, One Denver Place, Suite 500, 999-18th Street,
Denver, Colorado 80202-2405 (wjencl)
Mr. Chuck Schick, Camp Dresser and McKee, 2300-15th Street, Suite 400, Denver,
Colorado 80202 (wjencl)
Mr. John Moscato, Acumenics Research and Technology, Inc., 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202 (wjencl)
Acumenics Research and Technology, Inc., Room 132, Building 111 .
Rocky Mountain Arsenal, Commerce City, Colorado 80022 (wjencl)
-------
1.0
2.0
3.0
. .
4.0
5.0
6.0
7.0
. .
TABLE OF CONTENTS
INTRODUCTION. . .
. . .
. . . .
. . . . . . .
. . . .
SITE DESCRIPTION
2.1
2.2
2.3
. . . . .
. . .
. . .
. . . . .
. . .
LOCATION AND HISTORY. . . . . . . . . . . . . .
GEOLOGY AND HYDROLOGY. . . . . . . . . . . . . .
EXTENT OF CONTAMINATION. . . . . . . . . . . . .
INTERIM RESPONSE ACTION OBJECTIVE
. . .
. . . . . . .
4.1
INTERIM RESPONSE ACTION ALTERNATIVES.
. . . .
4.2
4.3
. . . .
ALTERNATIVE STRATEGIES. . . . . . . . . . . . .
4.1.1 No Action. . . . . . . . . . . . . . . .
4.1.2 Groundwater Interception/Containment. . .
4.1.3 In-Situ Remediation. . . . . . . . . . .
4.1.4 Cappinq . . . . . . . . . . . . . . . . .
4.1.5 Excavation and Treatment. . . . . . . . .
ALTERNATIVE TECHNOLOGIES FOR THE SELECTED STRATEGY
. . .
. . . . . . . . . . . .
. . . . . . .
. . .
4.2.1 Groundwater Extraction. . . . . . . . . .
4.2.2 Groundwater Recharge. . . . . . . . . . .
4.2.3 Groundwater Barriers. . . . . . . . . . .
4.2.4 Groundwater Treatment. . . . . . . . . .
ALTERNATIVE SYSTEMS FOR SELECTED STRATEGY. . . .
4.3.1 Encircling DBCP Sources with a Physical
Ba r r i e r ... . . . . . . . . . . . . . .
4.3.2 Interception System Perpendicular to
Contaminant Flowpath Without a Physical
Ba r r i e r . . . . . . . . . . . . . . . . .
4.3.3 Interception System Perpendicular to
Contaminant Flowpath with a Physical
Sa r r i e r . . . . . . . . . . . . . . . . .
4.3.4 Interception System Parallel to Contaminant
Flowpath Without a Physical Barrier. . .
4.3.5 Interception System Parallel to Contaminant
Flowpath with a Physi~al Barrier and
Recharge Near the ICS . . . . . . . . . .
CHRONOLOGY OF EVENTS
.......
. . . . . .
. . . .
IRA PROCESS
. . . . .
. . . . .
. . . . . . .
. . . .
DESCRIPTION OF THE RAIL CLASSIFICATION YARD
INTERIM RESPONSE ACTION. . . . . . . . . .
. . . . .
-i-
Page
1
4
4
5
9
14
15
15
16
16
17
18
19
20
20
21
23
24
25
26
30
32
38
38
44
47
-------
. 0
TABLE OF CONTENTS (Continued)
~
8.0
APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS FOR
THE REMEDIATION OF OTHER CONTAMINATION SOURCES (RAIL
CLASSIFICATION YARD) INTERIM RESPONSE ACTION. . . . .
8.1
8.2
8.3
8.4
8.5
INTRODUCTION. . . . . . . . . . . . . . . . . .
AMBIENT OR CHEMICAL-SPECIFIC ARARs ...... .
LOCATION-SPECIFIC ARARs . . . . . . . . . . . . .
ACTION-SPECIFIC ARARs . . . . . . . . . .0 . . . .
COMPLIANCE WITH THE OTHER ENVIRONMENTAL LAWS
52
52
52
56
57
66
9.0 SCHEDULE
. . . . . . . . . . . .
. . . .
. . . . . . .
67
10.0
11.0
CONSISTENCY WITH FINAL RESPONSE ACTION
. . . . . . .
REFERENCES
. . . . . . . . . .
. . . .
. . . .
. . .
68
69
1-
APPENDICES
("..,
APPENDIX A - COMMENTS AND RESPONSES ON THE DRAFT ARARS
APPENDIX B - RESPONSES TO EPA COMMENTS ON THE PROPOSED DECISION
DOCUMENT OTHER CONTAMINATION SOURCES, IRA
RAIL CLASSIFICATION YARD, RMA
-ii-
-------
Figure 1-1
Figure 2-1
Figure 2-2
Figure 2-3
Figure 2-4
Figure 2-5
Figure 4-1
Figure 4-2
Figure 4-3
Figure 4-4
Figure 4-5
Table 4-1
Table 4-2
Table 4-3
. . . 10
. . . 11
. . . 26
LIST OF FIGURES
Location Map of Rail Classification Yard. . .
Bedrock Surface Elevation. . . . . .
. . . .
Thickness of Saturated Alluvium, July 1989. .
Contour Map of the Water Table, July 1989 . .
DBCP Plume in the Alluvial Aquifer,
Ap r i 1 1989. . . . . . . . . . . . . . .
Distribution of Dibromochloropropane in
Groundwater, April and July 1989. . . .
Encircling DBCP Sources with a Physical
Sa r r i e r . . . . . . . . . . . . . . . .
Interception System Perpendicular to Con-
taminant Flowpath Without a Physical Barrier.
Page
2
6
7
8
30
Interception System Perpendicular to Con- taminant
Flowpath With a Physical Barrier. . . . . .. 33
Interception System Parallel to Contaminant
Flowpath Without a Physical Barrier. . . . .
Interception System Parallel to Contaminant
Flowpath With a Physical Barrier. . . . . . .
LIST OF TABLES
Estimated Costs of Encircling DBCP Sources
With a Physical Barrier. . . . . . . . . . .
Estimated Costs of an Interception System
Perpendicular to Contaminant Flowpath Withou~
a Physical Barrier~ . . . . . . . . . . . . .
Estimated Costs of an Interception System
Perpendicular to Contaminant Flowpath With a
Physical Barrier. . . . . . . . . . . . . . .
-iii-
36
39
Page
28
32
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LIST OF TABLES (Continued)
~
Table 4-4
Estimated Costs of an Interception System Parallel
to Contaminant, Flowpath Without a Physical
Ba r r i e r . . . . . . . . . . . . . . . . . .. 37
J
Table 4-5
Estimated Costs of an Interception System Parallel
to Contaminant Flowpath With a Physical
Ba r r i e r . . . . . . . . . . . . . . . . . .. 40
~.,
~
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1.0
INTRODUCTION
.~
The Interim Response Action (IRA) for the Rail Classification
Yard is being conducted under the "Remediation of Other
Contamination Sources" IRA sites under the Final Technical
Program Plan FY88-FY92 and the Federal Facility Agreement (1989).
The Rail Classification Yard is located in Section 3 of the Rocky
Mountain Arsenal (RMA) (Figure 1-1).
As specified in the Federal Facility Agreement, the purpose of
proposed Decision Documents for IRAs is to: (a) state the
objective of the IRA; (b) discuss [interim response action]
alternatives, if any, that were considered; (c) provide the
rationale for the alternative selected; (d) present the Army's
final ARAR decision; (e) summarize the significant comments
received regarding the Alternatives Assessment for this IRA and
the Army's response to those comments; and (f) establish an IRA
Deadline for completion of the IRA, if appropriate.
~~
Each of the above issues is addressed in this document. Comments
regarding the Draft Final Alternatives Assessment for Other
Contamination Sources Interim Response Action, Rail
Classification Yard, (Shell 1989a) were addressed in written
responses previously sent to the parties and are substantively
incorporated into this document, where appropriate.
For this report, the term "strategy" refers to fundamental
conceptual schemes of general response actions (e.g., no action,
groundwater interception/containment, in-situ remediation,
capping, and excavation and tr~atment). A "system" is a specific
conceptual design that achieves the selected strategy (e.g., an
intercept system achieves the strategy of containment of
&-
. .
-------
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Irondale OBCP
Control
System
33
27
Basin E
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RAIL CLAS$IFICATION
YARD I .
3 Lake
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-------
.
groundwater). A system is composed of one or more technologies
(e.g., a line of pumping wells may form an intercept system).
In this document, alternative strategies are assessed, and a
preferred strategy selected, using criteria outlined in the
Federal Facility Agreement (1919). Based on this assessment a
preferred strategy is selected in Section 4.0. Alternative
technologies and their impacts on cost analyses of specific
systems are also briefly discussed in Section 4.0. Since
engineering quality data are needed to assess them, some specific
technologies are not selected in this document. Instead, they
will be selected in the Preliminary Engineering and Implementa-
tion Plan documents that will be produced subsequent to this
report.
""r -
Technologies are combined into systems which are believed to be
capable of achieving the IRA objective. These systems are also
presented and evaluated in Section 4.0. A chronology of events
regarding the railyard IRA is presented in Section 5.0. The IRA
Process is described in Section 6.0. A summary of the selected
IRA alternative is contained in Section 7.0. The Applicable or
Relevant and Appropriate Requirements (ARARs) for this IRA are
contained in Section 8.0. The IRA schedule is presented in
Section 9.0. The consistency with the final response action is
stated in Section 10.0.
The Final Alternative Assessment for the Motor Pool Area IRA
(Woodward-Clyde 1989) proposes that a groundwater interception
system be constructed to i~tercept trichloroethylene (TCE) north
of the motor pool area. The document also proposes that the
interception system be impleme?ted in conjunction with the Rail
Classification Yard IRA. The reasons for this proposal are
discussed in Section 7.0.
. -
-3- .
-------
2.0
SITE DESCRIPTION
, .
Section 2.0 provides a summary of the physical setting of the.
Rail Classificati~n Yard. Additional information on site
characteristics are provided in Ebasco (1988a, 1989). The site
characterization was improved significantly by information
obtained from field investigations associated with the
preparation of the Alternatives Assessment for this IRA. This
information is presented in Shell (1989b).
~
2.1
LOCATION AND HISTORY
~
The Rocky Mountain Arsenal, located northeast of Denver Colorado,
became a site of milita~y chemical agent manufacturing by the
u.S. Army in 1942. Pesticides were manufactured at the site by
lessees beginning in 1946. The compound 1,2-dibromo-3-
chloropropane (DeCp), a pesticide manufactured by Shell Chemical
Company, has been found in alluvial groundwater near the Rail
Classification Yard in Section 3 of the RMA. The contaminated
groundwater forms a plume extending approximately from the
railyard area to the Irondale Control System (rCS) near the
northwest corner of Section 33 (Figure 2-4).
To prevent off-post migration of Decp in the alluvial
groundwater, the Irondale Control System was installed by Shell
and became operational in 1981. Since its startup, the rrondale
Control System has been effective in preventing off-post
migration of Decp (Shell 1989c).
&-
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2.2
GEOLOGY AND HYDROLOGY
..
Regional geologic and hydrologic conditions at the RMA have been
discussed in detail in previous reports (May 1982, Morrison-
Knudsen Engineers [MKE] 1987, and Ebasco 1989) and are not
repeated here. The two pertinent stratigraphic units underlying
the railyard are the Quaternary Alluvium and Denver Formation.
The alluvium underlying the railyard thickens from 65 to 110 feet
from south to north and is comprised primarily of well-graded
sand and gravelly sand, with minor lenses of gravel and less
permeable clayey sand and clay. The alluvium is underlain by
relatively impermeable claystone and shale of the Denver
Formation. Figure 2-1 is a contour map of the top of the Denver
Formation in the railyard area.
.~.
.~
The water table in the alluvium beneath the railyard varies from
about 55 to 75 feet below the ground surface. The saturated
alluvial thickness varies from about 15 feet beneath the southern
portion of the railyard to about 40 feet beneath the northern
portion of the railyard as shown in Figure 2-2. Data collected
since 1981 have shown that, except for a rise of about 2 feet in
1984, groundwater levels have remained fairly stable, with
seasonal variations being generally less than one foot.
As indicated by the map of the water table (Figure 2-3),
groundwater flow in the area is from the south to the north-
northwest. Lateral hydraulic gradients range from about 0.02
ft/ft in the southern portion of the railyard as shown in Figure
2-3 to about 0.006 ft/ft in the northern portion. A long-term
injection test conducted in th~ railyard area produced a
hydraulic conductivity estimate for the alluvial aquifer of
approximately 1.6 x 10-3 ft/sec, or 5 x 10-2 em/sec. The location
of the injection test well is shown in Figure 2-3. The
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underlylng claystones and shales of the Denver Formation probably
have hydraulic conductivities a few orders of magnitude lower
than those of the alluvium. Based on an estimated effective.
porosity of 0.35 and the estimated hydraulic conductivity and
gradients listed above, estimated average alluvial groundwater
velocities (i.e., particle velocities) range from 2.4 to 8.1
ft/day.
. .
Groundwater recharge in the railyard area is limited to
infiltration and percolation of precipitation. Although
difficult to quantify, recharge in the railyard area is enhanced
by the existence of cobble ballast beneath the tracks, which
allows for rapid infiltration and reduces evapotranspiration by
shading the soils and inhibiting vegetative growth. This- was
evidenced by the presence of moist soils beneath the ballast
during the winter and summer of 1989. Pore pressure data from
cone penetration testing also showed a high moisture content in
the vadose zone beneath the ballast.
2.3
EXTENT OF CONTAMINATION
Soil and water quality data collected in the railyard area were
compiled and presented in the Western Study Area Report (Ebasco
1989). Additional water quality and soiis data were collected by
MK-Environmental Services and presented in the Alternatives
Assessment for this IRA (Shell 1989b). Collectively, these
reports present extensive data from alluvial water quality
monitoring wells, soil gas studies, and cone penetrometer
investigations (cone penetration testing [CPT] and groundwater
sampling and analysis). These ~ata have documented the presence
of Decp and other compounds in the soil and groundwater
underlying the railyard area. Although other compounds exist in
alluvial groundwater beneath the railyard area, Decp is the only
-------
. -
compound that has been consistently found in the groundwater in
concentrations greater than ARARs. A brief summary of the
conclusions from these reports is contained in this section of
the Decision Document. For a more ~etailed presentation and
analyses of these data, refer to the referenced documents.
Groundwater quality data have shown a plume of Dacp extending
northward from the railyard toward the Irondale Control System
(Figure 2-4). Figure 2-5 shows the distribution of Dacp in
groundwater collected from wells and CPT holes near the railyard.
As documented in Shell (1989b), soil gas investigations have
shown Dacp in the surficial soils beneath the northern portions
of tracks 1 through 6 (the westernmost six tracks) in the
railyard. Concentrations were as high as 2 ug/g. Various spills
or leaks of Dacp in the railyard are thought to have migrated
either in the liquid or vapor phase through the vadose zone to
the alluvial aquifer, thus acting as sources ~f the Dacp plume.
As shown in Figure 2-5, the eastern and western limits of the
Dacp plume in the railyard area define a plume that is almost 500
feet wide. aased on the estimates of aquifer properties in the
northern portion of the railyard (i.e., saturated alluvial
thickness of 37.5 feet, hydraulic gradient of 0.0074 ft/ft, and
hydraulic conductivity of 5 x 10-2 em/see), the estimated
alluvial flow within the Dacp plume is approximately 100 gpm.
The estimated average groundwater flow velocity varies from about
2.4 to 8.1 ft/day in the alluvial aquifer underlying the
railyard. The configuration of the upgradient end of the plume
is interpreted to have fingers .of contamination emanating from
several small sources of Dacp in the railyard.
-------
l
.
to
Quebec Slreel
- ---------
Roil Classification yo.d
Sludy A.eo
RMA BOUNDARY
.
.
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SECTION 28
SECTION n
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-------
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,
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BulidinQ
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.1..... ..+- Railroad
-.- Sanitary Siwer
. - "'.100 "'.100-
--- -- OralnoQI
. Previoully Ealslln/) Alluvial MonItorln/) Well.
$ Newly Installed Alluvial MonitorinQ Well
e Newly Installed Alluvial Cluster Well
. Cone Penetrometer Tlst BorlnQ
. Connnl,a lion In Mlcrog,am Per liler
' ",. 16.11 D8 CP, Apr II 1989
. .. . . D8CP, Jul, 1989
" 0"
-- "',000 )J .".000- irS Nol Sampled
~
; , ,' Conlou, a' Wale, Table. Ju I, 1989
I ,.!)I'O
, I
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I I I
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I I " Mop Area
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,
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I
i In Groundwater . April and Jul y 1989
(rl I
.
. irs. t hepared by:
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"8.UuU .. nl "I.OQO. . ~ IlK -ENVIRONMENTAL SERVICES
..
~ I A DMSIOH Of _-f"(HGt.tiOH
-------
.
Concentrations of Dacp in the alluvial groundwater consistently
decrease with depth (Shell 1989b). This decrease may indicate
that the sources of Dacp contamination are either restricted to
the uppermost portion of the a~luvial aquifer or located above
the water table in overlying unsaturated sediments. Concentra-
tions of Dacp in the groundwater beneath the railyard have also
been decreasing with time since peaking in 1984 (Shell 1989b).
It is not known whether this trend will continue.
.-
Investigations have led to the conclusion .that the sources of
Dacp in groundwater are unsaturated soils and sediments
contaminated with DBCP, possibly by leakage from railcars (Shell
1989b). Existence of a large mass of residual Dacp in the
aquifer seems unlikely since the solubility of Dacp is 1,200,000
ug/l, and the highest concentration most recently detected in the
railyard aquifer was only 12.1 ug/l.
.~
Based on results from a soil gas survey, numerous sites of soil
contamination probably exist in the railyard area. A good
correlation between surface soil contamination and alluvial
aquifer contamination has not been demonstrated. This could be
the effect of intricate flow pathways from the surface soils to
the alluvial aquifer caused by the complex stratigraphy (e.g.,
example, multiple lenses of clay and clayey sand) and thick
vadose zone beneath the railyard.
. .
-13- .
-------
.- .
r~
3.0
INTERIM RESPONSE ACTION OBJECTIVE
The objective of the Rail Classification Yard IRA is to limit .the
migration of Decp near the railyard source areas as soon as
practicable. The IRA will concentrate on DBCP since it is the
only contaminant found in the aquifer underlying the railyard
which consistently exceeds standards identified in ARARs.
Although implementing this IRA may also limit the migration of
other contaminants and/or reduce the time period over which the
Irondale Control System must operate, these potential effects are
not included in the IRA objective.
-J
-------
4.0
INTERIM RESPONSE ACTION ALTERNATIVES
4.1
ALTERNATIVE STRATEGIES
The strategies considered for implementation in the Rail
Classification Yard IRA are:
No Action;
Groundwater Interception/Containment;
In-Situ Remediation;
Capping; and
Excavation and Treatment.
As specified in the Federal Facilities Agreement (1989), the
criteria used to assess alternative strategies are:
-J
Protection of Human Health and the Environment;
Mitigation of the Threat to Human Health;
Reasonableness of Cost;
Timeliness;
Attain Applicable or
Requirements (ARARs)
and
Relevant and Appropriate
to the Maximum Extent Practicable;
Be Consistent with and Contribute to the Efficient
Performance of Final Response Actions to the Maximum
Extent Practicable.
Each strategy listed above has been evaluated based upon its
ability to meet these criteria.
-------
4.1.1
No Action
Investigations have shown that DBCP is migrating away from the
railyard area in the underlying alluvial aquifer. The No Action
alternative has been eliminated as'a preferred strategy for this
IRA because it does not meet the specific IRA objective for this
site of limiting migration of DBCP near the source area as soon
as practicable.
4.1.2
Groundwater InterceDtion/Containment
The groundwater interception/containment strategy would inhibit
the movement of DBCP-contaminated groundwater away from the
railyard area. By.definition, it meets the IRA objective and the
criterion of reducing waste mobility.
A groundwater interception/containment strategy protects human
health and the environment, and mitigates the threat to human
health by inhibiting migration of DBCP. The strategy is expected
to be implementable in a timely manner (three years or less)
using proven technologies. Implementation of the groundwater
interception/containment strategy is expected to cost
approximately $3,000,000 or less (see Section 4.3 for cost
estimates) which is much more reasonable than the implementation
costs of the other strategy that meets the IRA objective (see
Section 4.1.5). It is expected that a groundwater
interception/containment strategy can be implemented in the
railyard area to achieve substantive compliance with ARARs
(presented in Section 8.0). It is not unreasonable to assume
that groundwater interception/conta~nment is consistent with and
contributes to the efficient performance of Final Response
Actions by containing migration closer to the source and away
from the boundaries of the RMA (see Section 10.0).
-------
In summary, a groundwater interception/containment strategy
fulfills all the assessment criteria for Interim Response Actions
and has been selected as the preferred strategy for the Rail
Classification Yard IRA.
4.1.3
In-Situ Remediation
Three types of in-situ remediation have been considered for
implementation as the Rail Classification Yard IRA. These types
are biodegradation, hydrolysis, and flushing/leaching.
Effectively implementing any of the in-situ remediation
strategies in this IRA would require considerably better source
delineation." Considerable effort was made to define the oacp
Source areas during the assessment phase of this IRA. However,
the information from these investigations indicates that the in-
situ IRA strategies may not be effective. The numerous, low-
level sources of oacp found in the vadose zone beneath the
railyard, coupled with the lithologic complexities (i.e., clay
and clayey sand lenses) pose problems for effective
implementation of in-situ technologies. Even a better
understanding of the locations of oacp source areas beneath the
railyard would be necessary before leaching could be considered a
reliable strategy. Each of the in-situ remediation strategies
would also require laboratory studies and possibly field tests to
optimize their design. These investigations would be time-
consuming and could delay implementation of the IRA for up to a
few years. Consequently, these strategies do not meet the
criterion of timeliness. The ability of in-situ strategies to
meet any of the remaining criteria cannot be determined until the
laboratory and/or field test programs are conducted. For these
reasons, the in-situ remediation strategies have not been
-------
retained for further consideration for the Rail Classification
Yard IRA.
Having a soil organic carbon normalized partitioning coefficient
(Roc) of 129 1/kg, Decp could be eventually flushed from some of
the sand and gravel zones underlying the railyard area. If a
leaching solution having an elevated pH is used, the combined
effects of hydrolysis and flushing may provide some notable
effect on vadose zone contamination. However, the presence of
some clayey sand and clay lenses and the lack of definition of
the Decp sources would complicate any attempts to flush the
vadose zone. One of the problems caused by these clay lenses is
the undetermined effect on flow pathways of any added leaching
water. If flushing is increased significantly above historical
levels, it is impossible with existing lithological information
on the clay lenses, to predict the flow paths of the increased
leachate. Loss of control of the leachate would be very
undesirable. Consequently, without a more detailed understanding
of the lithology, implementation of an enhanced flushing/leaching
strategy would need to be combined with some kind of a
containment strategy similar to that discussed in Section 4.3.1.
4.1.4
Caccing
Capping may reduce the mobility and migration rates of Decp in
the unsaturated zone by reducing or eliminating recharge from
precipitation. However, if vapor-phase transport is the
principal mechanism of transport into the aquifer, capping would
have a negligible effect on the migration of Decp into
groundwater and away from the railyard area. A significant
amount of groundwater would continue to flow through the alluvial
aquifer beneath the railyard regardless of whether a cap is
constructed. This flow would continue to transport Decp from the
-------
site. ~or these reasons, an IRA consisting solely of
constructing a cap over the railyard area is not acceptable.
.
Capping could be used in conjunction with another strategy. For
example, a cap could be used in conjunction with the groundwater
interception/containment strategy discussed in Section 4.1.2.
However, the effectiveness of a groundwater interception system
would not be improved with the addition of a cap. In fact,
adding a cap would reduce the rate at which the vadose zone would
be cleansed by natural flushing toward the interception system.
The apparent trend of decreasing concentrations of Decp in
groundwater may be evidence that such flushing is beneficial.
Eliminating this flushing seems undesirable if an effective
groundwater interception/containment system is constructed near
the Decp sources.
.
, ,
Since capping by itself would be ineffective, and when used in
conjunction with the preferred strategy of groundwater
interception/containment appears to be counterproductive, it has
been eliminated from further consideration for implementation
under this IRA.
4.1.5
Excavation and Treatment
Excavation and treatment of contaminated materials may meet the
objective of the Rail Classification Yard IRA. However, based on
evaluations of existing data, a large amount of potentially
contaminated saturated and unsaturated materials (approximately
2.8 million cubic yards) exist in the railyard area. Excavating
and treating this large volume of material would be very costly,
and is estimated at $90-95 million. Also, because of lack of
known point sources, excavating and treating a larger volume of
soil than necessary would be required unless the areal and
-19-
-------
verticaI extent of the Decp source areas are more reliably
defined. This would require establishment of action levels and
extensive, highly detailed investigations, which would delay
implementation of this IRA. Implementing an excavation and
treatment strategy for this IRA would likely take at least three
to four years or more because of the required investigations and
the large amount of potentially contaminated soil involved. The
strategy would probably be protective of human health and the
environment, mitigate the threat to human health, attain ARARs,
and contribute to the Final Remedial Actions. However, when
compared to the groundwater interception/containment strategy
which also meets these criteria, excavation and treatment is less
timely and cannot be implemented for a reasonable cost. For
these reasons, excavation and treatment has been removed from
further consideration for this IRA.
,~
4.2
ALTERNATIVE TECHNOLOGIES FOR THE SELECTED STRATEGY
As described in Section 4.1, groundwater interception/contain-
ment is the only strategy which meets the IRA objective and which
best complies with the IRA guidelines as set forth in the Federal
Facility Agreement (i.e., timeliness, reasonableness of cost,
etc.). This section of the Decision Document discusses
potentially useful technologies for this strategy. Specifically,
groundwater extraction, recharge, barriers, and treatment are
discussed. Since engineering quality data are sometimes required
to choose between these technologies, specific technologies
cannot always be selected in this document. Instead, they will
be selected in the Preliminary Engineering and Implementation
Plan documents that will be produced subsequent to this report.
4.2.1
Groundwater Extraction
-------
< ..
The high hydraulic conductivity of the alluvial aquifer and
relatively thick saturated alluvium are conducive to efficient
groundwater extraction with wells. Extraction wells are a proven
technology on the RMA, and can be installed readily in the
railyard area. Other extraction methods considered (e.g., well
points and extraction drains) are not as cost-effective as
extraction wells in the railyard area because of the significant
depths to the aquifer. These other methods will not be
considered further. The remaining sections of this report
reflect the selection of extraction wells as the preferred
extraction technology for this IRA.
.. ,
.
4.2.2
Groundwater Recharge
A variety of recharge options are potentially viable for use in a
groundwater interception/containment system for this IRA.
Recharge could be accomplished by use of wells, trenches, pits,
or shallow leach fields. The generally high permeability of the
alluvial sediments in the railyard area is conducive to efficient
recharge operations.
Recharging water in alluvial wells is a feasible option in the
railyard area. Recharge wells are most effective in more
permeable aquifers where a large contact area with the aquifer is
not required. When practical, other recharge methods are
generally preferred over recharge wells because of the high cost,
tendency for plugging, and relatively high maintenance costs of
recharge wells. Wells are often best suited when the depth to
the recharge zone is great, resulting in relatively high costs
for other recharge technologies. Recharge wells have been
successfully used in boundary systems on the RMA.
. -
-21-
-------
Rechargi~g water in gravel-filled trenches is a relatively
effective technique. The large contact area between trenches and
the adjacent aquifer helps to minimize plugging problems and may
consequently minimize maintenance costs. However, because of the
costs of constructing trenches to great depths, they may not be
cost-effective when it is necessary to recharge directly into
deep zones. This may be a limitation in the railyard area where
the alluvial aquifer reaches depths over 100 feet. Shallow
trenches could be feasible in the railyard area. The performance
of shallow trenches is largely related to the vertical
permeability of the soils between the bottom of the recharge
trench and the zone into which recharge is necessary. If shallow
recharge is found to be acceptable in this IRA, the use of
recharge trenches in the permeable materials underlying the
railyard area may be cost-effective.
r~
Recharge pits are essentially a smaller version of recha~ge
trenches and have most of the same advantages and disadvantages.
They may be preferable if the extra cost of constructing larger
trenches is not warranted by their extra recharge capacity.
-~
A final alternative for recharging water in the railyard area is
the use of shallow leach fields. If geologic conditions are
favorable, shallow leach fields could be the least expensive
recharge method.
If recharging directly into the saturated alluvial zone
underlying the railyard area is considered necessary, the only
practical method of accomplishing this recharge is with the use
of alluvial wells. In the gene7ally permeable materials of the
alluvial aquifer, recharge wells are expected to be more
effective and much less costly than constructing deep trenches or
pits. If the flowpath that recharge water follows is not
'.. .
-22-
-------
r'
important, shallow trenches, pits, or leach fields would probably
be the most cost-effective recharge technologies available for
this IRA.
4.2.3
Groundwater Barriers
.
Groundwater barriers can be used to stop or inhibit the flow of
groundwater. Two general types of barriers have relevance to
this IRA: physical barriers and hydraulic barriers. In order to
intercept or contain the contaminated groundwater flowing from
the railyard area, at least one of these types of barriers is
needed.
,...
Physical barriers placed below ground to inhibit and/or redirect
groundwater flow can be made of a variety of materials. Soil-
bentonite slurry walls are commonly used and have been used
successfully on the RMA. Other types of slurry walls are
sometimes used in conditions requiring special materials, usually
at a greater cost than that of a simple soil-bentonite wall.
Slurry walls can be constructed economically at depths down to
about 70 feet. At greater depths, the cost of constructing
slurry walls increases disproportionately with the increase in
depth. Even with these increases, slurry walls may still be more
cost-effective than other alternatives. Sheet piles can also be
driven into place to create a groundwater flow barrier. In large
installations and at depths such as those in the railyard area,
sheet piles are generally not as cost-effective as a simple soil-
bentonite slurry wall. Deep soil mixing (DSM) is another
technology that can be used to construct a physical groundwater
barrier. DSM is a soil improv~ment technique that does not
require excavation or soil removal. Hydraulically driven mixing
paddles and augers are drilled into the ground. The augers and
paddles mix the native soils with stabilizing agents or other
'.
. .
-------
. .
fluids which are fed through the center of each shaft. The
resulting column of mixed soil has a low permeability. A row of
overlapping columns can be constructed to form a barrier wall.
The cost of DSM is generally greater than that of a soil-
bentonite slurry wall.
, -
A hydraulic barrier is created by manipulating the water table
such that no flowpaths extend through the desired barrier. By
strategically extracting and/or injecting groundwater, the water
table beneath the railyard area could be configured so that all
contaminated groundwater in the DBCP plume is intercepted by an
extraction system. Such a hydraulic barrier can result in an
effective groundwater barrier as has been demonstrated by the
Irondale Control System which uses thi~ technique. One
disadvantage of this technique is that a significantly greater
amount of water must generally be extracted, treated, and
reinjected than exists in the contaminated plume. In order to
reduce this recirculation, a physical barrier may be placed
between the extraction and recharge facilities. In such cases,
the slurry wall cost may be partly or wholely offset by the
savings incurred by reducing or eliminating recirculation in the
hydraulic barrier.
"..
4.2.4
Groundwater Treatment
Operating experience with the Irondale Control System and other
boundary control systems on the RMA demonstrates that carbon
adsorption can cost-effectively remove Decp in the concentrations
present beneath the railyard to undetectable levels. utilizing
other treatment processes would require considerable laboratory
treatability studies and pilot testing to demonstrate their
feasibility and effectiveness. Consequently, the consideration
and evaluation of other groundwater treatment processes is
-24-
-------
, .
neither-necessary nor consistent with the criterion of timely
implementation of this IRA. The remaining sections of this
report were prepared based upon the selection of carbon
adsorption as the preferred groundwater treatment technology for
this IRA.
. . .
4.3
ALTERNATIVE SYSTEMS FOR SELECTED STRATEGY
.. .
Within the groundwater interception/containment strategy selected
in Section 4.0 of this report, five alternative systems and
system configurations have been considered for implementation as
the Rail Classification Yard IRA. Each of these systems is
composed of technologies discussed in Section 4.2 of this report.
Descriptions and evaluations of these five systems are summarized
in this section of the Decision Document.
The estimated flowrates required for successfully operating the
various systems presented in this section are based on
preliminary numerical simulations using the hydraulic
conductivity estimate (5.0 x 10-2 cm/sec) from the long-term
injection test conducted adjacent to the contaminated plume that
was discussed previously. As future investigations improve the
aquifer parameter estimates, new flow estimates will be
developed. If estimated aquifer parameters change significantly,
the groundwater interception/containment system recommended in
this document may need to be reconsidered. Nevertheless, the
relative differences between estimated flowrates presented in
this document are probably quite realistic.
Each of the five alternative systems discussed in this section
requires the treatment of contaminated groundwater. As stated in
Section 4.2.4, the selected treatment technology is carbon
adsorption. Preliminary investigations into the Irondale Control
-------
..,
, ~
System creatment plant (which utilizes carbon adsorption)
indicate it may be able to treat up to 300 gpm or more from the
Rail Classification Yard IRA, with some relatively economical
modifications. Construction of a new carbon adsorption system
capable of handling the range of flows expected from the railyard
I.RA (approximately 50 to 300 gpm for the various alternatives
discussed below) is estimated to cost between $800,000 and
$2,300,000. Cost analyses show that for the estimated flowrates
from the various alternative systems, modifying and using the ICS
treatment plant is more cost-effective than constructing and
operating new facilities in the railyard vicinity. Additionally,
use of a centralized treatment facility has an inherent benefit
over constructing and operating a new, completely separate
facility. For these reasons, it is assumed throughout the rest
of this document (including the system cost estimates) that the
Irondale Control System will be used for treating any
contaminated groundwater produced from the Rail Classification
Yard IRA. If further investigations 'show the ICS treatment plant
to be incapable of handling the groundwater from the railyard
IRA, the selection of the preferred groundwater
interception/containment system may need to be reconsidered.
Cost estimates developed for the five system alternatives
evaluated in this section are intended to be useful for
comparative purposes. For the purpose of cost comparisons,
year operating life has been assumed for the IRA.
a 5-
4.3.1
Encirclinq DBCP Sources with a Phvsical Barrier
A conceptually simple containment system considered for the Rail
Classification Yard IRA consists of constructing a physical
barrier completely around the DBCP source areas as depicted in
Figure 4-1. Groundwater within the enclosure would be pumped to
-26- .
-------
j
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Legend
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~ Building
Rood
'!.
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Railroad
Sanitary Sewer
Drainage
E.llllng Alluvial Monitoring Well
Propolld E.'ractlon Well
Proposed Recharge Well
DBCP Plume Outline July 1989 (0 I pg/l Con.our)
Dashed Whele In'efled
-.-
----
.
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Map Area ~
200 0 100 200 400
.... 1ft '.1
figUf8: 4-1
EncirCling DBCP Sources with a
Physical Barrier
Prepared b~:
~ MK-ENVIRONIIENTAL SERVICES
-------
keep wa~er levels from rising due to aquifer recharge or
stabilization after hydraulic separation from the surrounding
aquifer.
An advantage of completely encircling the railyard area with a
physical barrier is that the amount of groundwater that must be
pumped and treated due to leakage or recharge would be reduced.
Although difficult to quantify, a pumping rate of 50 gpm from
within the enclosure should be more than adequate, and much less
than the pumping rates required to effectively operate the
groundwater interception systems discussed subsequently in this
document. Minimizing the amount of pumped and treated water
minimizes the associated costs. Additionally, there would
probably be no need to pump the treated water back to the
railyard area, but it could be recharged to the aquifer in
existing or expanded ICS recharge facilities.
.
,
. .
A potentially significant advantage of encircling the railyard
with a physical barrier is the potential for contributing to the
Final Response Action for the site. Although the final action
has not been determined, some of the potential remediation
schemes would benefit from the installation of a physical barrier
surrounding the site. For example, flushing/leaching or in-situ
treatment of the sources of Decp may require that the site be
isolated from the adjacent aquifer with a physical barrier.
As shown in Table 4-1, the construction costs for a physical
barrier to the depths of up to approximately 110 feet required
for this site are substantial. For the reasons discussed in
Section 4.2.3, either a soil-bentonite slurry wall or deep soil
mixing would appear to be the most cost-effective physical
barrier for this installation. For the purposes of the cost
estimate shown in Table 4-1, it is assumed that a soil-bentonite
-------
. -,
. TABLE: 4-1
ESTIMATED COSTS OF ENCIRCLING DBCP SOURCES
WITH A PHYSICAL BARRIER
.'.
ASSUMPTIONS:
1) Design flowrate of pumping system is 50 gpm.
2) Soil bentonite slur~ wall is used for physical barrier.
3) Extracted water is treated and recharged in the Irondale Control System.
4) Cost of capital for determining present value of annual costs is 5 percent per
annum. Annual costs are assumed to begin at the beginning of the year.
..
CAPITAL COSTS
. .
Item Description
1) Soil-Bentonite Slur~ Wall
Unit Unit Cost Quantity Cost
-
SF $ 6.00 310,000 $1,860,000
LF $ 50.00 3,450 172,500
FA $ 17,000 2 $ 34,000
LF $ 10.00 9,500 $ 95,000
FA $ 5,000 15 $ 75,000
Subtotal $ 2,236,500
$ 447,000
$ 671,000
2) Remove and Replace Railroad Tracks
3) Groundwater Extraction Wells
4) Transmission Piping (3-inch PVC)
5) Monitoring Wells
.,
I
6) Engineering Design (20%)
7) SupervisionlGeneral Expense/OVerhead/
Health and Safety (30%)
8) General Admdnistration (10%)
$
$
224,000
559,000
9) Contingency and Fee (25%)
ANNUAL OPERATIONS AND MAINTENANCE COSTS
Total Capital Cost $ 4,137,500
1) Power 'costs to pump 50 gpm to Irondale Control System
$
$
1,000
5,500
2) Incremental treatment costs at Irondale Control System
3) Quarterly sampling of 10 monitoring wells, at $1,500 per sample
$
60,000
Total Annual O&M Cost $
66,500
Present Value of Capital Costs and 5 years of O&M costs is estimated
to be $4,440,000.
-------
""-
slurry wall would prove to be the most cost-effective physical
barrier, and that the treated water could be recharged in
existing ICS facilities. Unlike the other interception/contain-
ment sy~tems discussed in this document, constructing a soil-
bentonite slurry wall would also require significant, although
temporary, disturbance of surface facilities (e.g., railyard
tracks, local roads and utilities, loading docks, etc.) iri the
vicinity of the construction.
,
. -
Another effect of enclosing the railyard area with a physical
barrier is that the currently sloping water table will tend to
become level, -resulting in a rising water table in the northern
end of the enclosure. If this effect is unacceptable because of
. .
the resulting potential for leakage of contaminated water from
the enclosure, the pumping rate must be capable of reducing or
eliminating the water table rise. Simultaneously, the resultant
decline in the water levels in the southern portion of the
.enclosure would result in a hydraulic gradient from the
surrounding aquifer into the enclosure. If the physical barrier
has no major imperfections, the amount of this leakage would
probably be only a few gallons per minute or less. However, if
large, permeable imperfections exist in the barrier or its Denver
Formation key, the resulting leakage could significantly increase
the required pumping and treating rate. In spite of these
potential effe~ts, a pumping rate of 50 gpm is expected to be
adequate for this system.
. .
4.3.2
InterceDtion Svstem peroendicular to Contaminant Flowpath
Without a Physical Barrier
A groundwater interception system conceptually similar to the rcs
could be constructed slightly north of the DBCP sources found in
the railyard area. A typical configuration for such a system
(illustrated in Figure 4-2) is a row{s) of extraction wells
-------
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- Rood
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-.-
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Propolld E.'raellon Well
Proposed Recharge Well
DSCP Plume Oulllne July 1989 (0-' pg/L Con.our)
Dashed Where In'erred
~
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---
north
~
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200
400
200
a
100
..... '-I 4000'
".. In ....
figure: 4-2
Interception System Perpendicular
to Contaminant Flowpath
Without a Physical Barrier
1"I.pared by:
~ MK-ENYIROtAlENTAL SERVICES
-------
-
r,
ex~ending across the DBCP groundwater plume, a groundwater
treatment system, and a line of recharge wells north of the
extraction system. When operated properly, the system could
maintain higher water levels along the recharge wells than along
the extraction system, thus providing a hydraulic barrier to the
contaminated groundwater. As demonstrated by the ICS, such
systems can provide effective groundwater interception. Because
of the necessity for the recharge water to enter the aquifer at
the proper locations, it would be necessary to inject the
recharge water directly into the aquifer. . Consequently, recharge
wells would be recommended for this recharge system. The use of
shallow recharge trenches, pits, or leach fields would not be
adequate.
,
.-,
..
t-
Based on preliminary numerical simulations of the interception
system shown in Figure 4-2, pumping, treatment, and recharge
rates of approximately 300 gpm appear to be required to provide
an adequate margin of safety against contaminant bypass. This
relatively high flowrate, caused by the large amount of recycling
between the recharge and extraction systems, is one of the more
significant disadvantages of this type of system configuration.
The estimated costs of this interception system are shown in
Table 4-2.
4.3.3
Interce9tion System peroendicular to Contaminant Flowoath
with a Physical Barrier
. -
Due to the costs of the large amount of recycling in the system,
inclusion of a physical barrier between the recharge and
extraction systems is sometimes cost effective. Such a system,
illustrated in Figure 4-3, is incorporated in the northern
portion of the existing Northwest Boundary System on the Arsenal.
Because of the horizontal extent of the alluvial aquifer
underlying the railyard area, there would be some recycling of
-------
TABLE 4-2
ESTIMATED COSTS OF AN INTERCEPTION SYSTEM
PERPENDIaJLAR oro CONTAMINANT FLC:X-lPATH
WITHOUT A PHYSICAL BARRIER
ASSUMPTIONS:
1) Design flowrate is 300 gpm.
2) Extracted water is treated in the'Irondale Control System.
3) Cost of capital for determining present value of annual costs is 5 percent per
annum. Annual costs are assumed to ocur at the beginning of the year.
'-.
.
J
CAPITAL COSTS
Uni t Unit Cost
Quantity
Cost
, .
Item Description
1) Groundwater Extraction Wells
2) Grounqwater Recharge Wells
3) Distribution Piping (3-inch PVC)
4) Transmission Piping (two, 6-inch PVC lines) LF
5) Construction of Additional Monitoring Wells EA
r
) Modifications to Irondale Control System
,
,
7) Engineering Design (20%)
8) Supervision/General ExpensejOverhead/
Health and Safety (30%)
9) General Admdnistration (10%)
10) Contingency and Fee (25%)
ANNUAL OPERATIONS AND MAINTENANCE COSTS
EA
$ 17,000 8 $ 136,000
$ 15,000 12 $ 180,000
$ 10.00 1,500 $ 15,000
$ 27.00 9,000 $ 243,000
$ 5,000 25 $ 125,000
$ 510,000 1 $ 510,000
Subtotal $1,209,000
$ 242,000
$ 363,000
EA
LF
LS
$ 121,000
$ 302,000
Total Capital Cost $2,237,000
1) Power costs to pump 300 gpm to and from Irondale Control System
$
. $
12,500
2) Incremental treatment costs at Irondale Control System
37,000
3) Quarterly sampling of 25 monitoring wells at $1,500 per sample
$ 150,000
Total Annual O&M Cost $ 199,500
resent Value of Capital Costs and 5 years of O&M costs is estimated
to be $3,143,927.
-------
,...
water a~ound the ends of a physical barrier if a proper reverse
hydraulic gradient is maintained. Nevertheless, simulations have
shown that a physical barrier would allow reduction of the system
flowrate to roughly 200 gpm, while maintaining an adequate
reverse hydraulic gradient. A~ with the system described in
Section 4.3.2, this reverse hydraulic gradient, not the physical
barrier, would provide .the barrier to the migration of
contaminated water. The physical barrier would primarily be
intended to restrict the flow of clean water from the recharge
system to the extraction system.
i.
/"
. ~
. .
, .
f""
Whether a physical barrier is included in the groundwater
interception system described above is largely an econ~mic
decision. If the barrier costs are offset by the reduced costs
of extracting, treating, and recharging the smaller flows, then
installing a physical barrier would be cost-effective. Possible
additional considerations could include whether the presence of a
physical barrier would be expected to be undesirable during or
following final remediation, or whether the presence of a
physical barrier would add some margin of safety to the operation
of the groundwater interception system. Both of these
considerations are believed to be minor for this IRA.
1""'1
For this system alternative, a soil-bentonite slurry wall appears
to be the most cost-effective type of physical barrier, and its
use has been assumed in preparing the cost estimates for this IRA
as presented in Table 4-3. A comparison of estimated project
c'osts contained in Tables 4-2 and 4-3 do not show a large
difference between the costs of the two systems. Further
refinement of the designs and costs of these two systems would be
needed before the most cost~effective system could be chosen.
-------
.,
..
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Bulldinfj
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Railroad
, - - 5011- ben'onll.
Siurr W Wall Sonilary Sewer
Drainage
8 E xislinQ Alluvlul Moniloring Well
,r '.~.I,. ~ Proposed Extraction wen
"'.'''"''
(,1 Proposed Rechorfje Well
~ ---- DeCp Plume Ouliine July 1989 (0 1 Jlgll. Conlour)
~ \ Doshed Where In' erred
'----- \' \
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~ ",. I I "..8uo Interception System Perpendicular
I lil9 '
I I I
I I i 10 Contaminant Flowpath with
I I
I a Physica I Barr ier
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-------
....
4.3.4
Interception Svstem Parallel to Contaminant Flowpath
without a Phvsical Barrier
A variation of the groundwater interception system described in
Section 4.3.2 would be to alig~ the system parallel to the
direction of groundwater flow as illustrated in Figure 4-4. An
effective groundwater interception system would be achieved when
all of the contaminated plume converges on the extraction wells.
preliminary simulations have shown that the pumping rate of such
an intercept system in the railyard area could be reduced to
about 150 gpm. The smaller required flowrate would be due to the
fact that recirculation of treated water would occur principally
at the northernmost extraction well, whereas extensive recircula-
tion in the system outlined in Section 4.3.2 would occur in all
of the extraction wells.
..
'\
~ .
The reduced pumping rate is the primary advantage of this
modification. The estimated costs of this interception system
are tabulated in Table 4-4. A comparison of the costs in Tables
4-2 and 4-4 indicates that, for this IRA, an interception syste~
aligned along the axis of the contaminated plume would probably
be more cost-effective than one aligned perpendicular to the
flowpaths.
4.3.5
Interception Svstem Parallel to Contaminant Flow9ath with
a Physical Barrier and Recharae Near the lCS
A physical barrier could be added to the interception system
described in Section 4.3.4, (Figure 4-5). Including a physical
barrier would add some margin of safety to the system. During
periods when the system may be gut of operation, the water table
within the V-shaped physical barrier must rise significantly
before any contaminated water could get around the barrier.
-------
,....
. .
. TABLE: 4-3
!:S'1'IMAT!:D COSTS or AN INTERCEPTION SYSTEM
PE:RPEH>ICUIAR 'ro CONTAMINANT FLCWPA'I'H
WITH A PHYSICAL BARRIER
.
ASSUMPTIONS:
1) Design flowrate is 200 gpD.
2) Extracted water is treated in the Irondale Control System.
3) Cost of capital for determining present value of annual costs
annum. Annual costs are assumed to occur at the beginning of
is 5 percent per
the year.
CAPITAL COSTS
.
Item Description
1) Groundwater Extraction Wells
unit unit Cost
-
F.A $ 17,000
F.A $ 15,000
LF $ 10.00
$ 19.00
$ 5,000
Quanti tv
Cost
2) Groundwater Recharge Wells
3) Distribution Piping (3-inch PVC)
5 $
85,000
8 $ 120,000
4) Transmission Piping (two, 4-inch PVC lines) LF
5) Construction of Additional Monitoring Wells F.A
1,500 $
15,000
9,000 $ 171,000
,- ,
6) Modifications to Irondale Control System
LS . $ 510,000
25 $ 125,000
1 $ 510,000
7) Soil-Bentonite Slurry Wall (500 LF)
SF
$
5.00
62,000 $ 310,000
8) Engineering Design (20%)
Subtotal $1,336,000
9) Supe~ision/General Expense/OVerhead/
Health and Safety (30%)
10) General Admdnistration (10%)
$ 267,000
$ 401,000
11) Contingency and Fee (25%)
$ 134,000
$ 334,000
Total Capital Cost $2,472,000
ANNUAL OPERATIONS AND MAINTENANCE COSTS
1) Power costs to pump 200 gpm to and from Irondale Control System
$
$
18,000
29,000
2) Incremental treatment costs at Irondale Control System
3) Quarterly sampling of 2S monitoring wells at $1,500 per sample
$ 150,000
esent Value of Capital Costs and 5 years of O&M costs is estimated
to be $3,368,000.
.
Total Annual O&M Cost $
197,000
-------
,...
TABLE 4-4
ESTIMATED COSTS OF AN INTERCEPTION SYSTEM
',' PARALLEL TO CONTAMINANT FLOWPATH
WITHOUT A PHYSICAL BARRIER
. -
ASSUMPTIONS:
1) Design flowrate is 150 gpm.
2) Extracted water is treated in the Irondale Control System.
3) Cost of capital for determdninq present value of annual costs
annum. Annual costs are assumed to occur at the beqinninq of
CAPITAL COSTS
, ,
Item Description
Unit Unit Cost
1) Grcnmdwater Extraction Wells
E:A
$ 17,000
$ 15,000
$ 10.00
$ 19.00
$ 5,000
2) Groundwater Recharqe Wells
3) Distribution Pipinq (3-inch PVC)
E:A
LF
4) Transmission Pipinq (two, 4-inch PVC lines) LF
5) Construction of Additional Monitorinq Wells E:A
, 6) Modifications to Irondale Control System
LS
$ 510,000
7) Enqineerinq Design (20%)
, 1
8) Supervision;General ExpensejOverhead/
Heal th and Safety (30%)
9) General Administration (10%)
10) Con~inqency and Fee (25%)
is 5 percent per
the year.
.
Quantity Cost
4 $ 68,000
6 $ 90,000
2,500 $ 25,000
9,000 $ 171,000
25 $ 125,000
1 $ 510,000
Subtotal $ 989,000
$ 198,000
$ 297,000
$
99,000
$ 247,000
Total Capital Cost $1,830,000
ANNUAL OPERATIONS AND MAINTENANCE COSTS
1) Power costs to pump 150 gpm to and from Irondale Control System
. 2) Incremental treatment costs at Irondale Control System
3) Quarterly sampling of 25 monitoring wells' at $1,500 per sample
$
$
9,000
24,000
$
150,000
Total Annual O&M Cost $ 183,000
Present Value of Capital Costs and 5 years of O&M costs is estimated
to be $2,662,000.
-.
-------
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- . ",': Road
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Sani'ory Sewer
.
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E aislinQ Alluvial MonltorinQ Well
Proposed Ea'racllon Well
Proposed RechorQe Well
1--
-----..
Decp Plume Oulline July 1989 (01 JlQIl Conlowl
Doshed Where In'erred
north
Map Area ~
200 0 100 200 400
.:... .-14000.
Kale In ...-
figure: 4-4
Interception System Parallel to
Contaminant Flowpath Without
a Physical Barrier
Prepared b~:
~ IlK-ENVIRONMENTAL SERVICES
-------
.-.
,
Unlike the interception systems considered in Sections 4.3.2,
4.3.3, and 4.3.4, preliminary numerical simulations have shown
that, with the addition of the physical barrier to the system
described in Section 4.3.4, a reverse hydraulic gradient could be
maintained without recharging treated water nearby. Instead, the
treated water could be recharged in either existing or expanded
facilities of the ICS, thus saving the costs of pumping and
pipeline construction.
.
A drawback of including the physical barrier is its cost.
Estimated costs of the complete interception system illustrated
in Figure 4-5 are shown in Table 4-5. A comparison of Tables 4-4
and 4-5 indicates that the added costs of a slurry wall would
probably not be completely offset by the cost savings resulting
from recharging the treated water near the ICS.
-------
nor th
"','..1" ~
I
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I 200 0 100 200 400
I I ,,"
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,. ~"I' I I Interception System Parallel
1'.,01" to
(j18 I I (;19
I I i
I I i / Contaminant Flowpath with a
I I I
I I Physical Barrier
I
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" 0 ..
~ :: , g :: l'I'epored br'
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\ ,
;/ /1 ,. OMSIOH or - fUIGUiON
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~ole~ L~~e I~CS~
Soil- benlonile
Slurrr Wall--
,
''''-.
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t
~
1._,OI.n
--..----
L_f.,y J
BuiletinQ
, Road
..-.
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. . .
Railroad
Sunilarr Sewer
-.-
.
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OroinaQe
EaislinQ Alluvial MonilorinC) Well
Proposed Ealraclion Well
Proposed Recharge Well
DBCP Plume Oulllne Julr 1989 (0 I pg/l Conlow I
Dashed Where Interred
t",'"''
{
(01
\
\
---.. -- -
-------
. TABLE 4-5
ESTIMA'l'ED COSTS OF AN INTERCEPTION SYSTEM
p.M~r.r.v.r. 'ro CCNrAMINANT rt..CWPA'I'H
WI'l'H A PHYSICAL BARRIER
"
. .
ASSUMPTICNS:
1) Design flowrate is 150 gpn.
2) Extracted water is treated and recharged in expanded Irondale Control System
Facilities.
3) Cost of capital for deter.mining p~esent value of annual costs is 5 percent per
annum. Annual costs are assumed to occur at the beginning of the year.
4) . Recharge is assumed to occur in new recharge wells installed near the ICS. If
recharge trenches, pits, or leach fields are utilized, the costs may decrease.
CAPITAL COSTS
uni t uni t Cost
Item Description
1) Groundwater Extraction Wells
2) Groundwater Recharge Wells
3) Distribution Piping (3-inch PVC)
4) Transmission Piping (4-inch PVC)
5) Construction of Additional Monitoring Wells EA
; 6) Modifications to Irondale Control System
-~ 7) Soil-Bentonite Slurry Wall (700 LF)
8) Engineering Design (20%)
9) Supervision/General ExpensejOverhead/
Health and Safety (30%)
10) General Administration (10%)
11) Contingency and Fee (25%)
ANNUAL OPERATIONS AND MAINTENANCE COSTS
EA
$ 17,000
$ 15,000
$ 10.00
$ 11.00
$ 5,000
$ 510,000
$ 5.00
.
Quanti ty Cost
4 $ 68,000
6 $ 90,000
2,500 $ 25,000
9,000 $ 99,000
20 $ 100,000
1 $ 510,000
78,000 $ 390,000
Subtotal $1,282,000
$ 256,000
$ 385,000
$ 128,000
$ 321,000
Total capital Cost $2,372,000
2) Incremental treatment costs at Irondale Control System
EA
LF
LF
LS
SF
$
$
3,500
1) Power costs to pump 150 gpm to and from Irondale Control System
24,000
$ 120,000
3) Quarterly sampling of 20 monitoring wells at $1,500 per sample
Total Annual O&M Cost $ 149,500
Present value of Capital Costs and 5 years of O&M costs is estimated
to be $3,052,000.
-------
,-
5.0
CHRONOLOGY OF EVENTS
~-
The significant events leading to the decision to select
groundwater interception/containment as the preferred alternative
in the Rail Classification Yard'IRA are presented below.
Date
Event
1980
In early 1980, Decp was detected in
groundwater in the alluvial aquifer
beneath the Irondale comm~nity, located
to the northwest of RMA.
December 1981
The Irondale Decp control system (ICS)
was placed into operation to prevent
DeCP-contaminated groundwater from
migrating offpost. The ICS pumps
groundwater from the alluvial aquifer,
treats the groundwater to remove
contaminants, and injects the treated
water back into the alluvial aquifer.
September 1982
The U.S. Army completed Assessment of
Contaminant Mi9ration from Potential
Contamination Sources (Geraghty & Miller
1982). Decp detected in railyard soil
borings indicated this area is a
potential source of the Decp plume.
September 1984
The U.S. Army completed Dibromo-
Chlor09r09ane Source Definition. Roc~
Mountain Arsenal. Colorado (Whitten and
Shamburger 1984). Installation and
sampling of additional monitoring wells
indicated that a continuous Decp plume
probably emanates from the railyard in
Section 3 and flows northwest through
Sections 4 and 33 to the ICS.
June 1987
The State of Colorado, Shell Oil
Company, U.S. EPA, and U.S. Army agreed
that 13 Interim Response Actions
(including the Rail Classification Yard)
would be conducted.
February 1, 1988
proposed Consent Decree lodged in the
case of U.S. v. Shell Oil Companv with
the U.S. District Court in Denver,
-------
,-
Colorado. The Consent Decree specified
13 Interim Response Actions (including
the Rail Classification Yard) to
facilitate remediation activities.
March 1988
The U.S. Army completed Final
Contamination Assessment Re90rt. Site 3-
4. Nemaaon S9il1 Area. Version 3.2
(Ebasco 1988a). Locating DeCp sources
proved to be very difficult; Decp was
detected at only one soil sampling
location within the holding tracks in
the railyard.
The U.S. Army completed Final Phase II
Data Addendum. Site 3-4. Nemagon Seill
Area. Version 3.1 (Ebasco 1988b).
Additional soil sampling confirmed the
presence of Decp in shallow soil near
the sampling location mentioned above.
October 1988
February 1989
The Federal Facilitv Aareement (1989)
specified that the Rail Classification
Yard is one of several sites where
Interim Response Actions are proposed.
,~
August 18, 1989
Shell Oil Company submitted Draft Final
Alternatives Assessment for Other
Contamination Sources. Interim Reseonse
Action. Rail Classification Yard. RMA
(Shell 1989a) to the U.S. Army to be
issued to the Organizations and the
State. Results of field investigations
and proposed alternative technologies
for the implementation of the IRA were
presented. Groundwater intercep-
tion/containment was recommended as-the
preferred strategy.
-,
September 20, 1989
Received comments from the U.S. EPA
concerning Draft Final Alternatives
Assessment for Other Contamination
Sources. Interim Reseonse Action. Rail
Classification Yard. RMA.
-------
,"-
October'25, 1989
Shell Oil Company submitted Final
Alternatives Assessment (or Other
Contamination Sources. Interim ReSDonse
Action. Rail Classification Yard. RMA
(Shell 1989b) to the U.S. Army to be
issued to ~he Organizations and the
State.'
" .
-..,
-------
,...
6.0
IRA PROCESS
With respect to this IRA for the Rail Classification Yard, the
IRA process is as follows:
- -
2.
3 .
1.
As Lead Party, Shell prepared a Draft Final
Alternatives Assessment for Other Contamination
Sources, Interim Response Action, Rail Classification
Yard, RMA including a draft of the ARARs (prepared by
the U.S. Army). This was submitted to the U.S. Army
for issuance to the Department of Interior (DOI) and
the other Organizations for review and comment.
Comments were submitted solely by the U.S. EPA within
30 days after receipt of the draft assessment. After
the close of the comment period, and in consideration
of the comments received, Shell prepared and
transmitted the final assessment to the U.S. Army, for
issuance to the DOI and the other Organizations.
Shell, the DO I, and the other Organizations were
afforded the opportunity to participate, at the RMA
Committee level, in the identification and selection of
ARARs pertinent to this IRA.
As Lead Party, Shell submitted this Proposed Decision
Document for the Rail Classification Yard IRA to the
U.S. Army for issuance to the DOI and the other
Organizations. It included the Army's final ARAR
decision. The Proposed Decision Document was subject
to a 30-day public co~ment period during which the
other Organizations, the DOI, and any other person
could comment on the Proposed IRA Decision Document.
The Army held a public meeting during the comment
-------
.'
," .
, -
period to inform the
Arsenal of this IRA.
will be supported by
community in the vicinity of the
The proposed Decision Document
an administrative record.
4.
promptly after close 'of the comment period, Shell
submitted the Draft Final Decision Document for the
Rail Classification Yard IRA to the U.S. Army for
transmittal to the DOl and the other organizations.
5.
Within 20 days after issuance of the Draft Final
Decision Document for the Rail Classification Yard IRA,
an Organization (including the State if it has agreed
to be bound by the Dispute Resolution process, as
required by the Consent Decree, or DOl under the
circumstances set forth in the Consent Decree) may
invoke Dispute Resolution. Dispute Resolution may
concern either the proposed IRA or the Army's ARAR
decision.
6.
After the close of the period for invoking Dispute
Resolution (if Dispute Resolution is not invoked) or
after the completion of Dispute Resolution (if
invoked), Shell shall submit a Final Decision Document
for the Rail Classification Yard IRA to the Army. The
supporting administrative record will be included. The
Army shall then issue a Final Decision Document to the
other Organizations and the DOl. Thereafter, the
Decision Document will be subject to judicial review in
accordance with Sections 113 and 121 of the
Comprehensive
Liability Act
9613, 9621.
Environmental Response, Compensation, and
of 1980, as amended, 42 U.S.C. Sections
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8.
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.~
7;
Following issuance of the Final IRA Decision Document,
Shell shall be the Lead Party responsible for designing
and implementing the IRA in conformance with the
Decision Document. Shell shall issue a Draft IRA
Implementation Document to the DOI and the other
Organizations for review and comment. This Draft
Implementation Document shall include final drawings
and specifications, final design analyses, a cost
estimate, and a schedule for implementation of the IRA.
As Lead Party for design and implementation of this
IRA, Shell will issue the Final Implementation
Document, as described above, and will be responsible
for implementing the IRA in accordance with the IRA
Implementation Document.
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. 7 . 0
DESCRIPTION OF THE RAIL CLASSIFICATION YARD
INTERIM RESPONSE ACTION
The selected strategy for the Rail Classification Yard IRA is
groundwater interception/containment. Each of the five
groundwater interception/containment system alternatives
described in Section 4.3 appears to be a viable option that meets
the objectives of the IRA and could be implemented on a timely
basis. On a cost basis, each appears to be reasonable and
effective (see Tables 4-1 through 4-5). The differences between
the estimated costs for the four groundwater interception systems
may be within estimating error (e.g., assumptions on
acceptability of using the ICS treatment plant and the hydraulic
conductivity estimate of 5.0 x 10-2 em/see).
Based on its suitability and the cost estimates presented, an
interception system installed parallel to the contaminant
flowpath without a physical barrier is selected for
implementation (Figure 4-4 and Table 4-4). The selected
alternative will consist of a row of alluvial extraction wells
located along the center axis of the DBCP plume, one or more rows
of recharge wells located near the downstream end of the
interception system, modifications to the ICS to provide
sufficient treatment capacity for the pumped water from the
railyard IRA, and pipelines for conveying the water to and from
the ICS. A system of all~vial monitoring wells will also be
installed in the vicinity of the interception system.
partly in response to a comment received from the EPA that
consideration be given to addressing other contaminants in this
IRA, the Final Alternative Assessment for the Motor Pool Area IRA
(Woodward-Clyde 1989) proposes that a motor pool groundwater
interception system be implemented jointly with the railyard IRA
interception system. This decision is desirable because of the
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proximity of these sites, the suitability of carbon adsorption
for treating both DBCP and TCE, and the potential hydraulic
interferences between the separate interception systems. The
Draft Final Decision Document for the Motor Pool Area includes a
groundwater containment/treatment component, which may be
implemented in conjunction with the railyard IRA, depending upon
the results of further studies.
r
The major assumptions upon which the selection of this
interception system is based will be checked during the
preparation of the Implementation Document for this IRA. If
differences between the assumed and actual conditions are
significant, or if deemed appropriate after assessing the effects
of jointly implementing the Motor .Pool and railyard IRA
interception systems, reconsideration of the selected system
could occur.
.~
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8.0
AP~LICABLE OR RELEVANT AND APPROPRIATE REOUIREMENTS FOR THE
REMEDIATION OF OTHER CONTAMINATION SOURCE~ (RAIL
CLASSIFICATION YARD) INTERIM RESPONSE ACTION
8.1
INTRODUCTION
.
These draft Applicable or Relevant and Appropriate Requirements
(ARARs) address a specific area, the rail classification yard,
identified for remediation prior to the issuance of a Record of
Decision (ROD) for the Onpost Operable Unit of the Rocky Mountain
Arsenal. This interim response action is intended to provide
remediation on an interim basis for this designated area and is
not intended to be a final response action. Further response
actions, as necessary, will be determined in the Onpost ROD.
8.2
AMBIENT OR CHEMICAL-SPECIFIC ARARs
Ambient or chemical-specific requirements set concentration
limits or ranges in various environmental media for specific
hazardous substances, pollutants, or contaminants. Such ARARs
either set protective cleanup levels for the chemicals of concern
in the designated media or indicate an appropriate level of
discharge based on technological considerations.
The objectives of this IRA are discussed elsewhere in the Draft
Final Decision Document. This IRA will be implemented prior to
the final remediation to be undertaken in the context of the
Onpost Operable Unit ROD. The list of specific contaminants has
been completed based upon the field data concerning this specific
source. The media of concern here are the water which may be
removed and treated from this source area and the soils, which
may contain contaminants. However, no ambient or chemical-
specific ARARs were identified concerning levels of contaminants
for soils. The chemical-specific ARARs listed below will apply
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.
at the point of discharge of treated water from the selected
treatment system, the Irondale Boundary System (IBS). The water
treatment to be provided by the IBS is limited to activated
carbon adsorption, which treats organic contaminants. ARARs were
identified for those organic contaminants expected to be
contained in the influent received by the IBS, including influent
received from the Motor Pool Area, as discussed in the Decision
Document for that specific area.
Because the IBS does not provide drinking water and is not a
public water system, the standards established under the Safe
Drinking Water Act (SDWA) and the Clean Water Act (CWA) for
drinking water are not applicable to this IRA.
The standards contained in 40 CFR Section 264.94 were not
considered applicable to this treatment system because the
constituents in the influent are not from regulated units. Since
the standards promulgated pursuant to this regulation are
identical to those promulgated under the National Primary
Drinking Water Regulations (NPDW) pursuant to the SDWA, further'
discussed below, for the same 14 compounds these standards are
not considered further.
Consistent with the most recent EPA guidance, the Proposed
National Contingency Plan, 53 Fed. Reg. 51441, Maximum
Contaminant Level Goals contained in the NPDW are not considered
either applicable or relevant and appropriate to apply in the
context of this treatment system. EPA's Tolerances for Pesticide
Chemicals on or in Raw Agricultural Commodities (TPCRAC), 40 CFR
Part 180 and the Food and Drug .Administration's Tolerances for
Pesticides in Food, administered by EPA (TPF), are not relevant
and appropriate to apply in the context of this IRA. These
standards were developed for particular items (e.g., food and
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, -
crops) 'which are not subject to watering with the effluent from
this treatment system.
. .
The Colorado Basic Standards for Groundwater (CBSG), 3.11.0 (5
CCR 1002-8), are not applicable, consistent with current EPA
guidance as contained in the proposed NCP, 53 Fed. Reg. 51394,
51475, but are considered relevant and appropriate to apply to
the selected compounds at the point of reinjection of the treated
effluent from the IBS. Some of these standards a~e more
stringent than the NPDW MCLs, discussed b~1ow, for the
contaminants to be treated by this IRA and were therefore
selected as relevant and appropriate to apply. Where the CBSG
standard was identical to the MCL, the MCL is identified as the
.. '
ARAR .
Federal Water Quality Criteria (FWQC) were reviewed and
considered not applicable to this IRA since they are non-
enforceable" guidelines and not enforceable limitations. Aquatic
life is not believed to be a concern regarding treated water.
MCLs and other selected standards, discussed below, are
considered to be sufficiently protective of human health. Under
these circumstances, FWQC were not considered relevant and
appropriate to apply in the context of this IRA.
In order to provide adequate protection of public health and the
environment, the Army has determined that Maximum Contaminant
Levels (MCLs) established under the Safe Drinking Water Act are
relevant and appropriate to apply within the context of this IRA.
The Army believes that these limitations will result in an
effluent which does not represent a potential risk to human
health and the environment.
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. -.
1'"
Some compounds, at present, only have MCLs proposed. These,
while not ARARs, are considered in the design of the system.
These compounds are listed separately as "to be considered" (TBC)
standards, consistent with the ,proposed NCP, 53 Fed. Reg. 51394,
51436.
The chemical-specific ARARs determined relevant and appropriate
to apply in the context of this IRA are:
Compound ARAR Level Source
Benzene 5 ug/l 40 CFR S 141.61(a)
1,1-dichloroethylene 7 ug/l CBSG
1,2-dichloroethylene 70 ug/l CBSG
T-1,2-dichloroethylene 7 ug/l 40 CFR S 141.61(a)
Toluene 2,420 ug/l CBSG
1,1,1-trichloroethane 200 ug/1 40 CFR S 141.61(a)
1,1,2-trichloroethane 28 ug/l CBSG
Trichloroethylene 5 ug/l 40 CFR S 141.61(a)
The following standards are TBCs and will be considered in the
design of this treatment system and sought to be attained, if
practicable:
1,1-dichloroethylene
TBC Level
0.2 ug/1
0.06 ug/l
Source
Comoound
DBCP
54 FR 22093
EPA Health
Toluene
1,1,2-trichloroethane
2,000 ug/l
0.6 ug/l
Assessment Sum.
54 FR 22093
EPA Health
Assessment Sum.
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8.3
LOCATION-SPECIFIC ARARs
. .
Location-specific requirements set restrictions on activities,
depending on the characteristi~sof. the site or the immediate
environment, and function like action-specific requirements.
Alternative remedial actions may be restricted or precluded,
depending on the location or characteristics of the site and the
requirements that apply to it.
. . : .
It should be noted that Paragraph 44.2 of the Federal Facility
Agreement provides that "wildlife habitat(s) shall be preserved
and managed as necessary to protect endangered species of
wildlife to the extent required by the Endangered Species Act (16
U.S.C. 1531 et seq.), migratory birds to the extent required by
the Migratory Bird Treaty Act (16 U.S.C. 703 et seq.), and bald
eagles to the extent required by the Bald Eagle Protection Act,
16 U.S.C. 688 et seq."
--,
While this provision is not an ARAR, the statutory requirements
are ARARs and will be complied with for purposes of this IRA.
Based on the location of the IBS and the new piping and other
construction that is contemplated by this IRA, the Army believes
that this IRA will have no adverse impact on any endangered
species or migratory birds or on the protection of wildlife
habitats. Coordination will be maintained with the U.S. Fish and
Wildlife Service to ensure that no such adverse impact arises
from implementation of this IRA.
The Army has identified as relevant and appropriate and will
comply with 40 CFR 6.302(a) and (b) concerning the location of
any treatment system additions, avoiding the construction of such
additions in a manner the would have an adverse impact on
wetlands or be within a flood plain.
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The regulations at 40 CFR 230 were reviewed and determined not to
be applicable within the context of this IRA because no discharge
of dredged or fill material into waters of the United States will
occur. Because these regulations address only the disposal of
such materials into the waters of the United States, which is not
contemplated, they are not considered to be relevant and
appropriate to apply in the context of this IRA.
.
The regulations at 33 CFR 320-330 were reviewed and determined to
be neither applicable nor relevant and appropriate because they
address actions affecting the waters of the United States. No
such actions are contemplated within the context of this IRA.
8.4
ACTION-SPECIFIC ARARs
DescriDtion
Performance, design, or other action-specific requirements set
controls or restrictions on activities related to the management
of hazardous substances, pollutants, or contaminants. These
action-specific requirements may specify particular performance
levels, actions, or technologies as well as specific levels (or a
methodology for setting specific levels) for discharged or
residual chemicals.
Construction of Treatment System
Air Emissions
On the remote possibility that there may be air emissions during
the course of the construction of this treatment system, the Army
has reviewed all potential ambient or chemical-specific air
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. .
emission requirements. As a result of this review, the Army
found that there are, at present, no National or State ambient
air quality standards currently applicable or relevant and
appropriate to any of the volatile or semivolatiles chemicals in
the ground water found in the area in which construction is
contemplated.
".,.
I
In the context of this IRA, there is only a very remote chance of
any release of volatiles or semivolatiles and, even if such a
release did occur, it would only be intermittent and of very
brief duration (because the activity that produced the release
would be stopped and modified appropriately if a significant air
emission was detected by the contractor's air monitoring
specialist). The Army has significant experience with the
construction of extraction and reinjection wells and has not
experienced any problems from air emissions during construction
of such facilities. The site-specific Health and Safety plan
will adequately address these concerns. This plan to be
developed for use in the IRA will detail operational
modifications to be implemented in the event monitoring detects
specific levels, defined in this plan, of such emissions.
.
r'"
The National Emissions Standards for Hazardous Air Pollutants
(NESHAPS) were evaluated to determined whether they were
applicable or relevant and appropriate to apply in the context of
construction of this IRA. These standards were not considered
applicable because they apply to stationary sources of these
pollutants, not to construction activity. These standards were
not considered relevant and appropriate because they were
developed for manufacturing processes, which are significantly
dissimilar to the short-term construction activity contemplated
by this IRA.
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The provisions of 40 CFR 50.6 will be considered relevant and
appropriate. This standard is not applicable because it
addresses Air Quality Control Regions, which are areas
significantly larger than and different from the area of concern
in this IRA. Pursuant to this 'regulation, there will be no
particulate matter transported by air from the site that is in
excess of 75 micrograms per cubic meter (annual geometric mean)
and 260 micrograms per cubic meter (maximum 24-hour
concentration) will be exceeded more than once per. year.
.
Worker Protection
r '
The provisions of 29 CFR 1901.120 are applicable to workers at
the site because these provisions specifically address hazardous
substance response operations under CERCLA. It should be noted
that these activities are presently governed by the interim rule
found at 29 CFR 1910.120 but that by the time IRA activity
commences at the site, the final rule found at 54 FR 9294 (March
6, 1989) will be operative. (The final rule becomes effective on
March 6, 1990.)
7'~
General Construction Activities
The following performance, design, or other action-specific State
ARARs have been preliminarily identified by the Army as relevant
and appropriate to this portion of the IRA and more stringent
than any applicable or relevant and appropriate federal standard,
requirement, criterion, or limitation. These standards are not
applicable because they specifically do not address a remedial
action or circumstance under CERCLA:
Colorado Air Pollution Control Commission Regulation No.1, 5 CCR
1001-3, Part III(D)(2)(b), Construction Activities:
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.
. '."
c.
d.
a.
Applicability - Attainment and Nonattainment Areas
b.
General Requirement,
Any owner or operator engaged in clearing or leveling
of land or owner or operator of land that has been
cleated of greater than one (1) acre in nonattainment
areas for which fugitive particulate emissions will be
emitted shall be required to use all available and
practical methods which are technologically feasible
and economically reasonable in order to minimize such
emissions, in accordance with the requirements of
Section III.D. of this regulation.
Applicable Emission Limitation Guideline
Both the 20% opacity and the no off-property transport
emission limitation guidelines shall apply to
construction activities; except that with respect to
sources or activities associated with construction for
which there are separate requirements set forth in this
regulation, the emission limitation guidelines there
specified as applicable to such sources and activities
shall be evaluated for compliance with the requirements
of Section III.D. of this regulation. (Cross
Reference: Subsections e. and f. of Section III.D.2 of
this regulation).
Control Measures and Operating Procedures
Control Measures or operational procedures to be
employed may include but are not necessarily limited to
planting vegetation cover, providing synthetic cover,
watering, chemical stabilization, furrows, compacting,
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minimizing disturbed area in the winter, wind breaks,
and other methods or techniques.
Colorado Ambient Air Quality Standa~ds, 5 CCR 1001-14, Air
Quality Regulation A, Diesel-Powered Vehicle Emission Standards
for Visible Pollutants:
,-
, ,
a.
, .
c.
d.
.
No person shall emit or cause to be emitted into the
atmosphere from any diesel-powered vehicle any air
contaminant, for a period greater than 10 consecutive
seconds, which is of such a shade or density as to
obscure an observer's vision to a degree in excess of
40% opacity, with the exception of Subpart 8 below.
.
b.
No person shall emit or cause to be emit~ed into the
atmosphere from any naturally aspirated diesel-powered
vehicle of over 8,500 lbs gross vehicle weight rating
operated above 7,000 feet (mean sea level), any air
contaminant for a period of 10 consecutive seconds,
which is of a shade or density as to obscure an
observer's vision to a degree in excess of 50% opacity.
Diesel-powered vehicles exceeding these requirements
shall be exempt for a period of 10 minutes, if the
emissions are a direct result of a cold engine start-
up and provided the vehicle is in a stationary
position.
This standard shall apply to motor vehicles intended,
designed, and manufactured primarily for use in
carrying passengers or cargo on roads, streets, and
highways.
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The following performance, design, or action-specific State ARAR
is applicable to this portion of the IRA and is more stringent
than any applicable or relevant and appropriate Federal standard,
requirement, criterion or limitation:
."
Colorado Noise Abatement Statute, C.R.S. Section 25-12-103:
~.
a.
....., .
\
Zone
Residential
Each activity to which this article is applicable shall
be conducted in a manner so that any noise produced is
not objectionable due to intermittence, beat frequency,
or shrillness. Sound levels of noise radiating from a
property line at a distance of twenty-five feet or more
there from in excess of the db(A) established for the
following time periods and zones shall constitute prima
facie evidence that such noise is a public nuisance:
7:00 a.m. to
next 7:00 p.m.
55 db(A)
60 db(A)
70 db(A)
80 db(A)
7:00 p.m. to
next 7:00 a.m.
50 db(A)
55 db(A)
65 db(A)
75 db(A)
Commercial
Light Industrial
Industrial
b.
c.
In the hours between 7:00 a.m. and the next 7:00 p.m.,
the noise levels permitted in subsection (1) of this
section may be increased by ten db(A) for a period
of not to exceed fifteen minutes in anyone-hour
period.
Periodic, impulsive, or shrill noises shall be
considered a public nuisance when such noises are at a
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e.
.~
f.
....
sound level of five db(A) less than those listed in
Subpart (a) of this section.
d.
Construction projects shall be subject to the maximum
permissible noise levels specified for industrial zones
for the period within which construction is to be
completed pursuant to any applicable construction
permit issued by proper authority or, if no time
limitation is imposed, for a reasonable period of time
for completion of the project.
~
.
For the purpose of this article, measurements with
sound level meters shall be made when the wind velocity
at the time and place of such measurement is not more
than five miles per hour.
In all sound level measurements, consideration shall be
given to the effect of the ambient noise level created
by the encompassing noise of the environment from all
Sources at the time and place of such sound level
measurements.
In substantive fulfillment of Colorado Air Pollution Control
Commission Regulation No.1, this IRA will employ the specified
methods for minimizing emission from fuel burning equipment and
construction activities. In substantive fulfillment of
Colorado's Diesel-Powered Vehicle Emission Standards, no diesel
motor vehicles associated with the construction shall be operated
in manner that will produce emissions in excess of those
specified in these standards.
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The noise levels pertinent for construction activity provided in
C.R.S. Section 25-12-103 will be attained in accordance with this
applicable Colorado statute.
wetlands Im9lications
.
Through estimation of the general area where any system additions
will be located, the Army does not believe that any wetlands
could be adversely affected. However, until a final design is
selected and a final siting decision made, .it cannot be
definitively determined that no impact on wetlands will occur.
If the final site selection and/or design results in an impact on
wetlands, the Army will review the regulatory provisions
concerning wetlands impact and other approp~iate guidance, and
will proceed in a manner consistent with those provisions.
Coordination will be maintained with the u.s. Fish and Wildlife
Service concerning any potential impacts on wetlands.
Land DisDosal Restrictions and Removal of Soil
There are no action-specific ARARs that pertain to the excavation
of soil during the construction of this treatment system.
EPA is currently developing guidance concerning the Land Disposal
Restrictions (LDR). While guidance is limited, the Army has not
determined that any listed waste subject to LDR will be present
in the influent treated or soil removed by this IRA. More
listings are scheduled to be completed prior to the
implementation of this IRA and the Army will review these as they
are released. If it is determined that a listed waste subject to
LDR is present, the Army will act in a manner consistent with EPA
guidance for the management of such within the context of CERCLA
actions. Spent granulated activated carbon may be sent for
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. .
," .
regeneration, if possible, or may be disposed of consistent with
EPA guidance if unable to be regenerated due to the presence of
certain constituents. Any offsite transport or disposal will be
consistent with the management requirements of 40 CFR Parts 262
and 263 and any more stringent State requirements for offsite.
-r-
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Although removal of soil from the area where any treatment system
additions will be located is a TBC, not an ARAR, it will be
performed in accordance with the procedures set forth in the Task
No. 32 Technical Plan, 'Sampling Waste Handling (November 1987),
and EPA's July 12, 1985, memorandum regarding "EPA Region VIII
Procedure for Handling of Materials from Drilling, Trench
Excavation and Decontamination during CERCLA RI/FS Operations at
the Rocky Mountain Arsenal." Soils generated by ~xcavation
during the course of this IRA, either at surface or subsurface,
may be returned to the location from which they originated (i.e.,
last out, first in). Any materials remaining after completion of
backfilling that are suspected of being contaminated (based on
field screening techniques) will be properly stored, sampled,
analyzed, and ultimately disposed as CERCLA hazardous wastes
consistent with the EPA guidance then in effect, as appropriate.
For material determined to be hazardous waste resulting from
construction activities, substantive RCRA provisions are
applicable to their management. These substantive provisions
include but are not limited to: 40 crR Part 262 (Subpart C, Pre-
Transport Requirements), 40 CFR part 263 (Transporter Standards),
and 40 CFR Part 264 (Subpart I, Container Storage and Subpart L,
Waste Piles). The specific substantive standards applied will be
determined by the factual circumstances of the accumulation,
storage or disposal techniques actually applied to any such
material.
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8.5
COMPLIANCE WITH THE OTHER ENVIRONMENTAL LAWS
AS is evident from the various portions of
IRA was prepared in substantive compliance
(the regulations implementing the National
Act of 1969).
.
I ...
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this document, this
with 40 CFR 1502.16
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9.0 SCHEDULE
, '
Consistent with the Federal Facility Agreement (1989) and the
Final Technical Program Plan FY88-FY92, the Milestone for
completing the Draft Implementation Document for the Rail
Classification Yard IRA is August 24, 199'0. The deadline for
completing the IRA will be established in the Implementation
Document for this IRA but is presently set as for November 25,
1992.
.
. .
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...,
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10.0
CONSISTENCY WITH FINAL RESPONSE ACTION
.'"
This IRA will be. consistent with the final response
intercepting and treating cont~minated groundwater,
the spread of contamination.
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action by
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11.0
REFERENCES
RIC 88076R04
Ebasco Services Inc., 1988a. Final Phase I Contamination
Assessment Report, Site 3-4, Nemagon Spill Area, Version 3.2.
. .
Ebasco Services Inc., 1988b. Final phase II Data Addendum, Site
3-4, Nemagon Spill Area, Version 3.1. October.
.
Ebasco Services Inc., 1989. Final Remedial Investigation Report,
Western Study Area, Version 3.2.
Federal Facility Agreement Between the United States and Shell
Oil Company. February, 1989.
RIC 81342R06
Geraghty & Miller, Inc., 1982. Assessment of Contaminant
Migration from Potential Contamination Sources. September.
. .
RIC 82295R01.
May, J.B., 1982. Regional Groundwater Study of Rocky Mountain
Arsenal, Denver, Colorado: U.S. Army Engineer Waterways
Experiment Station.
Morrison-Knudsen Engineers, Inc. 1987.
County, Colorado.
Shell'Oil Company, 1989a. Draft Final Alternatives Assessment
For Other Contamination Sources, Interim Response Action,
Rail Classification Yard, RMA. August. Prepared by MK-
Environmental Services.
Geology of the RMA, Adams
Shell Oil Company, 1989b. Final Alternatives Assessment For
Other Contamination Sources, Interim Response Action, Rail
Classification Yard, RMA. October. Prepared by MK-
Environmental Services.
Shell Oil Company, 1989c. Irondale DBCP Control System, Rocky
Mountain Arsenal, Review of 1987/1988 Operations. September.
RIC 85133R03
Whitten, C.B. and Shamburger, J.R., 1984. Dibromo-chloropropane
Source Definition, Rocky Mountain Arsenal, Colorado. Phase
I. September.
Woodward-Clyde
of Interim
Motor Pool
Command.
Consultants, 1989. Final Alternative Assessment
Response Actions For Other Contamination Sources,
Area. November. Prepared for U.S. Army Materiel
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. .
APPENDIX A
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Response to Comments from the Environmental Protection Agency
on the Draft Applicable or Relevant and Appropriate Requirements
for the Remediation of Other Contamination Sources
(Railyard and Lime Settling Basins) Interim Response Action
r .
1. Contaminants present in the lime settling basins soils or
groundwater (refer to pages 2-8, 2-9, 2-11, and 2-12 of the
Assessment Document) include the following:
- ,
A. aldrin
B. dieldrin
C. endrin
D. isodrin
E. chlorophenyl
F. chlorophenyl
G. chlorophenyl
H. DCPD
I . DDE
J . DDT
K. DBCP
L. chloroform
M. methylene chloride
N. benzene
o. chlorobenzene
P. fluoroacetic acid
Q. methylphosphonic acid
R. arsenic
S. mercury
T. coppe r
u. lead
V. zinc
w. cadmium
x. chromium
Y. tetrachloroethene
z. toluene
AA. xylene
bb. dichlorobenzene
cc. trichlorobenzene
dd. tetrachlorobenzene
ee. endrin intermediates: not specified
ff. PAHs
1. anthracene
2. pyrene
3. fluoranthene
4. bycycloheptadiene
5. hexachlorobutadiene
6. trichlorobenzenamine
7. methylsulfonyl dinitro-n
8. n-dipropyl-benzenamine
methyl sulfide
methyl sulfoxide
methyl sulfone
01/31/90
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gg.
hh.
ii.
j j .
DIMP
DMMP
dithiane
arsine
Of the above compounds, ARARs were established for only the
following contaminants:
1.
2.
3.
4.
5.
6.
arsenic
benzene
cadmium
chromium
lead
mercury
while TBCs were listed for only cadmium, DBCP, and leac.
In addition to these compounds, ARARs (either MCLs or AWQC) exist
for at least the following compounds:
l.
2.
3.
4.
5.
6.
7.
8.
9.
aldrin
dieldrin
endrin
DDT
chloroform
copper
zinc
toluene
dichlorobenzene
Additionally, a health advisory of 600 ppb exists for DIMP.
Please expand the ARARs analysis to include health-based levels
for those compounds for which no ARARs were identified. These
levels must be considered in the final alternative selection.
Response: This discussion has been revised. The Lime Settling
Basins Proposed Decision Document does not include groundwater
treatment within the selected treatment alternative. The Rail
Classification Yard Proposed Decision Document does address some
groundwater treatment, but this treatment is specifically focused
and not intended to be comprehensive groundwater remediation,
which is beyond the scope of this IRA.
2. Page 2, second paragraph, the Colorado groundwater
standards, promulgated in August 1989, need to be examined to see
if they are ARARs for any of the compounds of concern (refer to
Comment 1, above).
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..."
r'O
Response: These standards have been considered, as reflected by
the discussion in the Proposed Decision Document for the Rail
Classification Yard.
3. Page 3, list of "to-be-co'nsidered", the only contaminant for
which an ARAR is identified for the Rail Yard IRA is for DeCp;
here, the language states that the level for Decp will be
attained "if practicable". This is not a satisfactory approach.
A commitment to achieve these levels to the maximum extent
practicable is necessary.
Response: This section has been revised. However, the Army is
aware of no guidance in the proposed NCP or the Federal Facility
Agreement which directs that Tecs be achieved to the maximum
extent practicable. The proposed NCP, in discussing this matter,
states "[TeCs] may assist in determining, for example, health-
based levels for a particular contaminant for which there are no
ARARs or the appropriate method for conducting an action."
Proposed NCP at 54 Fed. Reg. 51436.
4. Page 3, Air Emissions, first paragraph, and page 5, last
paragraph, check the AQCR language used previously for other IRA
ARARs analyses.
Response:
This language has been revised.
S. Page 4, paragraphs three and four, and page 9, top
paragraph, if the wildlife protection and wetlands are
considerations for these IRAs, please identify them as ARARs.
Response:
This language has been revised.
6. If the Irondale Boundary Containment System (IBCS) or any
treatment plant is used to treat the railyard plume (DeCp Plume),
drinking water standards would be ARARs.
Response: The Iecs is considered as a water treatment system as
part of the interim response selected for the railyard. '
Treatment ARARs are identified in the Proposed Decision Document
for the Rail Classification Yard.
7. Land Disposal Restrictions and Removal of Soils. There is no
mention of the spent activated carbon (GAC) in this section.
Spent GAC could be classified as a hazardous waste and would have
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.
.....
to be handled as such. Spent GAC containing Decp might not be
accepted for reactivation and would need to be properly disposed
of in a RCRA standard landfill.
. -
Response: The proposed Decision Document includes a discussion
of this matter.
."
.
8. On page 5, if contaminants
quantities contemplated by this
regulation should be considered
included as an ARAR.
subject to NESHAPS are emitted in
regulation, the NESHAPS
relevant and appropriate and be
Response: The selected treatment approaches for the Lime
settling Basins and Rail Classification Yard do not involve
treatment systems which are sources of air emissions, such as
strippers, so no further response is provided.
air
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, .
Responses to Comments from Shell Oil Company
Draft Applicable or Relevant and Appropriate Requirements
for the Remediation of Other Contamination Sources
(Rail Classification Yard and Lime Settling Basins)
on the
-...,
Shell disagrees with the ~election of Maximum Contaminant
Levels (MCLS) as relevant and appropriate to this IRA. The
preferred alternatives for addressing treatment of contaminated
soils for the lime basins may involve discharge of the water to
percolation beds. This treatment is not designed to provide
drinking water. In the Army ARARs document, the Army itself
states that "this IRA will not provide drinking water and not be
a public water system." Shell, therefore, objects to selection
of MCLs as relevant and appropriate. Similarly, if the preferred
alternatives for treatment of the DBCP plume from the rail yard
are immediately downgradient of the source areas and the
reinjected groundwater will be treated again at the Irondale
system, MCLs should apply only at the point where humans could be
exposed to the groundwater. This point would be downgradient of
the Irondale boundary, not at the point of discharge of treated
water from any treatment system. In spite of Shell's objection
to selection of MCLs as ARARs, Shell does not object to the
selection of the concentration levels identified as ARAR Levels
as operational criteria.
Response: The Army believes that the use of MCLs as relevant and
appropriate ARARs at the point of reinjection of treated
groundwater and other identified standards as TBCs is consistent
with EPA guidance concerning ARARs for aquifers which are
potentia~ drinking water sources, proposed NCP, 54 Fed. Reg. at
51441.
Shell disagrees that proposed MCLs can be selected as the
TBCs. The concept of TBCs is not mandated by section 121(d) of
CERCLA. Proposed standards are particularly- suspect since the
purpose of proposed rulemaking is to receive comments prior to
finalization of standards. Shell also disagrees with the
proposed standards for DBCP and lead because they are based on
CAG methodology. It incorporates the attached comments on the
proposed MCL for DBCP.
Response: The Army is aware of Shell's position concerning CAG
methodology and considers this .an issue which Shell, if they
desire, should pursue with the appropriate divisions within EPA
headquarters which have responsibility for developing methodology
for standard setting. The Army will continue to follow the
standards developed by EPA and apply EPA guidance in developing
approaches to the Arsenal cleanup. The Army believes that use of
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proposed MCLs as TBCs is consistent with current EPA guidance, as
reflected in the proposed NCP.
~.
Shell supports the selection of 40 C.F.R. S 6.302(a) and (b)
concerning the location of any tr~a~ment system to avoid the
construction of such system in'a manner that would have an
adverse impact on wetlands or be within a flood plain.
Response:
No response necessary.
The Assessment Documents are unclear regarding how any of
the preferred alternatives will generate particulates that would
not be controlled by the requirements of Regulation 1, 5 CCR 100-
3, Part III (D) (2) (b), Construction activities, which is also
selected as an ARAR. While Shell does not disagree with
compliance with the particulate air standard set forth in 40
C.F.R. S 50.6, it fails to understand how the standard .is
relevant and appropriate.
~
Response: The cited state regulation addresses construction
activities in general while the cited federal regulation
establishes specific requirements for particulates, a concern in
the general area in which this site is located. Under these
circumstances the Army believes it is appropriate to comply with
both regulations.
r~
Shell agrees that the requirements of 29 C.F.R. S 1909.120
apply to workers, whether or not those requirements are ARARs.
Response:
No response necessary.
The Colorado Ambient Air Quality Standards, Air Quality
Regulation A, "Diesel-Powered Vehicle Emission Standards for
Visible Pollutants," is only an ARAR to the extent that motor
vehicles may carry passengers or cargo on roads, streets and
hIghways offpost.
Response:
The Army agrees with this comment.
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.-
Shell supports the proposal of C.R.S. S 25-12-103, Noise
Abatement, as an ARAR.
Response:
No response necessa~y.
r .
. ,
Shell further supports the decision to review regulatory
provisions concerning wetlands impact and other appropriate
guidance if the final site selection and/or design results in an
impact on wetlands. Shell reserves the right to comment on those
regulatory provisions and guidance at the time that they are
proposed.
..
Response:
No response necessary.
Shell reserves the right to comment on how any substantive
RCRA standards may be applied to the accumulation, storage or
disposal techniques of materials determined to be hazardous waste
resulting from construction activities.
Response:
No response necessary.
Shell further reserves the right to comment on any
provisions of parts 264, 241, or 262 that are considered as
ARARs. Until the preferred alternatives are described in more
detail, it is impossible to determine which, if any, of the above
regulations may be applicable or relevant and appropriate.
Response:
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..
.-
..
APPENDIX B
COMMENTS AND RESPONSES
-------
,-.
RESPONSES TO EPA COMMENTS ON THE
PROPOSED DECISION DOCUMENT
OTHER CONTAMINATION SOURCES IRA.
RAIL CLASSIFICATION YARD. RMA
.
RESPONSES TO GENERAL COMMENTS
..
1.
COMMENT:
The text states that ARARs will be achieved "to the maximum
extent practicable." A Decision Document must select ARARs
and identify how they will be achieved or why they are not
practicable. Until such a selection is made, we reserve the
right to comment further.
...,
RESPONSE:
-
No comment required.
2.
COMMENT:
The preferred alternative is a line of extraction wells
(four in the diagram, page 36), approximately 200 feet
apart, and parallel to the groundwater flow direction
combined with a line of recharge wells (six in the diagram,
page 36), approximately 100 feet apart, and perpendicular to
the apparent groundwater flow direction, installed without a
subsurface physical barrier.
The design of the selected alternative may need to be
modified based on field observations following installation
of initial wells. The recharge wells must effectively
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~..
M .
provide a "line-recharge-to-a-linear-sink" (upgradient);
thus, a hydraulic barrier and the extraction wells must
effectively provide a "double-line-source-to-slot" such th~t
the double line source extends to the northeast and the
southwest beyond the limits of the plume and the sources.
It is questionable whether 4 wells, 200 feet apart, can
accomplish this effect, particularly to the northeast of the
well alignment shown on Figure 4-4, with the wells being
pumped at less than 40 gpm each. .
. ...
., .
" .
RESPONSE:
Appropriate analyses will be performed during the design
phase of the IRA in order to determine an effective design
for the interception system. The number and location of the
required extraction and recharge wells will be determined
during the design phase. Included in the design analyses
will be consideration of the effects of integrating the
proposed Motor Pool IRA groundwater interception system.
The number and location of the extraction wells shown in the
Proposed Decision Document were intended to be illustrative
of the general concept and for cost comparison purposes, and
were not to be considered the final design.
RESPONSES TO SPECIFIC COMMENTS
1.
COMMENT:
On page 2, second paragraph, the statement "Applicable
Relevant and Appropriate Regulations (ARARs)" should read
Applicable Q£ Relevant and Appropriate Reauirements.
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. .
Th~ text Ilsts six criteria used to assess alternative
strategies which are not the same as those presented in the
Assessment Document. Criteria should be the same at both
the Assessment and Decision Document stages.
RESPONSE:
.,
The wording in the text has been corrected to read
Applicable or Relevant and Appropriate Requirements.
...,
It is felt that the appropriate assessment criteria for use
in the Decision Document are those listed in Sections 22.5,
22.6, and 22.7 of the Federal Facility Agreement. .The six
criteria listed in the Proposed Decision Document are taken
from the$e sections of the FFA. Unfortunately, the criteria
listed in the Alternatives Assessment were slightly
different. Nevertheless, the differences in criteria are
not felt to have effected the choice of the selected
alternative.
2.
COMMENT:
The text appears to favor allowing natural forces to move
contaminants from contaminated soils into the groundwater
where the contaminants can be captured and dealt with.
Without further definition of the degree of soil
contamination, a pump and treat program could go on
indefinitely. Because the IRA plans to use the groundwater
as a means to capture contaminants, an alternative that
would facilitate flushing of contaminated soils should be
considered. The proposed alternative has reinjection of
treated water downgradient of the extraction wells.
Reinjection upgradient or into the contaminated soils has
01/31/90 - EPA
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7-
r ..
the potential of flushing the contaminants and decreasing
the remediation time. EPA requests the evaluation and
discussion of these options in the Draft Final Decision
Document. Additionally, we request information on the
partitioning coefficient which may effect the success of
this suggested reinjection option.
.. .
.
RESPONSE:
Section 4.1.3 of the text has been expanded to include
additional discussion of the option of flushing contaminants
from the railyard soils. For the reasons discussed in the
text, soil flushing is not a preferred alternative for the
Rail Classification Area IRA.
3 .
COMMENT:
-.
Concerning pages 23 and 24, Groundwater Treatment, the only
technology considered for treatment of extracted groundwater
is GAC at the Irondale Control System (ICS). No other
treatment measure is mentioned due to the assumption that
"other treatment processes would require considerable
laboratory treatability studies. . ." This statement is
not substantiated and questionable given the numerous other
proven water treatment technologies (e.g., UV light, ozone,
etc.). Neither the Alternatives Assessment nor the Decision
Document address the issue of whether the Irondale system
can adequately treat the volume or concentrations expected
from the extraction system. The basis for such conclusions
should be documented in the record.
On page 24, last paragraph, the text indicates that the ICS
"may be able to treat up to 300 gpm." Use of the rcs is
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.-
,~
in~e9ral to the selected alternative. We request further
details of the anticipated contaminant concentration levels
to be treated at the ICS and assurance that the ICS has
sufficient capacity.
r- -
RESPONSE:
~.
,
The estimated flow of groundwater within the limits of the
identified Decp plume is slightly over 100 gpm. eased on
the available data, the average concentrations of Decp
within this plume are expected to probably be between 1 and
5 ug/l. The actual concentration of Decp that will be
pumped by the interception system will be influenced by the
amount of dilution from treated water that recirculates
between the recharge and extraction systems. System design
and operation will effect the amount of this recirculation.
The proposed Motor Pool IRA interception system is expected
to produce a waste stream of roughly 100 to 150 gpm, with
average TCE levels of probably less than 5 ug/l. Additional
data are currently being obtained in both the Railyard and
Motor Pool areas to allow a more accurate determination of
the waste stream concentrations and flows.
.~
AS discussed in the Decision Document, treatment by carbon
adsorption of waters contaminated by Decp at the levels
expected from the Railyard groundwater interception system
has been proven effective at other treatment systems on the
RMA. Activated carbon adsorption is also very effective in
removing TCE. Designing either UV light or ozone treatment
systems with similar reliability to that already existing in
the ICS treatment system would require additional time for
analytical work and testing. The extra time required to
design and test another treatment technology (e.g., UV
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.~
, .
light, ozone, etc.) does not seem warranted in light of the
experience treating similar waste streams on the RMA with
carbon adsorption, especially considering the fact that an
existing activated carbon adsorption system (the IeS) can
probably be utilized with relatively minor modifications.
Use of the Ies treatment plant will also reduce the needless
proliferation of treatment plants on the Arsenal.
... .
. .
"
During the design phase of the Railyard IRA, careful
attention will be given to determining the available
capacity at the IeS treatment plant and the anticipated
waste streams from both the Railyard and Motor Pool IRA
groundwater interception systems. If these design-level
evaluations show the ICS treatment plant to be unsuitable
for treating the waste streams from the two IRAs, it is
anticipated that adequate capacity can be cost-effectively
obtained with appropriate modifications to the treatment
plant (estimated costs for such improvements were factored
into the analyses presented in the Proposed Decision
Document). If not, as the State of Colorado suggested in a
comment, the plan to use the Ies treatment plant could be
altered.
4 .
COMMENT:
The Endangered Species Act is a location-specific ARAR (see
page 52).
RESPONSE:
The Endangered Species Act is considered as a location-
specific ARAR and is listed in the Draft Final Decision
Document.
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.. ",
"..
or-
5.
COMMENT:
J .
NESHAPS should be considered as relevant and appropriate to
this activity (see page 541.
. .
RESPONSE:
~
. .
The Army disagrees with this comment. NESHAPS are not
considered to be relevant and appropriate because they are
developed for specific manufacturing processes which are
substantially dissimilar to the short-term construction
process for this IRA. The contemplated treatment system
does not include an air emission source, such as an air
stripping system, so NESHAPS were not considered relevant
and appropriate to apply to the treatment system.
6.
COMMENT:
Wetlands are a location-specific ARAR, not an action-
specific ARAR (see page 59).
RESPONSE:
Wetlands considerations are identified as a location-
specific ARAR in the Draft Decision Document. They are
discussed as an action-specific ARAR because wetlands
considerations could affect actions taken during
also
construction.
01/31/90 - EPA
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r~
RESPONSES TO STATE COMMENTS ON THE
PROPOSED DECISION DOCUMENT
OTHER CONTAMINATION SOURCES IRA.
RAIL CLASSIFICATION YARD. RMA
..
1 .
COMMENT:
. .
An intercept and recharge system (one or more) for both the
Railyard and Motor Pool should be evaluated and designed in
concert. Therefore, the specific approach and configuration
of the intercept system seems somewhat premature at this
point.
RESPONSE:
,-
Originally, it was felt that evaluations of some alternative
groundwater interception system configurations would be
meaningful in the Alternatives Assessment for this IRA. As
this IRA has progressed, it has become apparent that the
value of these preliminary evaluations has been primarily
limited to comparing groundwater containment with
groundwater interception. The value of evaluating varying
groundwater interception system configurations has been
minimal. During the design phase of this IRA, some of the
conclusions based on these evaluations of alternative
groundwater interception system configurations will require
reassessment. As mentioned in the Proposed Decision
Document,. if any of the preliminary conclusions do not hold
up under further scrutiny using design-level information and
analyses, appropriate configuration changes will be
proposed.
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..~
.,..-
2 .
COMMENT:
. -
The decision to choose the Irondale Containment System (ICS)
for treatment, with or without, modification, must be based
on the consideration of the waste stream (volume and flux)
for both the Railyard and the Motor Pool Areas. Shell
looked only at the requirements for the Railyard Intercept
System. The Army failed to look at Ies requirements or
capacities for the Motor Pool Intercept System. The
decision to use the Ies (with or without modification) for
the treatment component of the IRA may need to be altered
based on considering requirements of both sites.
~
, '
.
RESPONSE:
.'.
During the design phase of the Railyard IRA, careful
attention will be given to determining the available
capacity at the ICS treatment plant and tne anticipated
waste streams from both the Railyard and Motor Pool IRA
groundwater interception systems. If these design-level
evaluations show the Ies treatment plant to be unsuitable
for treating waste streams from the two IRAs, it is
anticipated that adequate modifications to the treatment
plant (estimated costs of such improvements were factored
into the analyses presented in the Proposed Decision
Document). If not, as the State suggests, the plan to use
the res treatment plant could be altered.
O. .
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..
T-
ARAR RESPONSES
1 .
COMMENT:
. .
~.
Paqe 49. Dara. 1 (8.2). Shell states that the ARARs
identified were for organic contaminants "expected to be
contained in the influent received by the IBS, including
influent received from the Motor Pool Area. . . ."
However, the list of contaminants set out in the Shell
document contain few of the contaminants found in the Motor
Pool groundwater. The ARARs analysis should be expanded to
include those contaminants.
~
RESPONSE:
The ARARs listed for the organic compounds contained in the
influent expected to be treated by the Irondale Boundary
Containment System, including influent which originates from
the motor pool area, are consistent with Table 2-2 of the
Final Alternatives Assessment for the Motor Pool Area,
except for chloroform which is not addressed at this time
and which is also listed in the Final Alternatives
Assessment as ranging only up to 6.0 ug/l which is far below
the standard established in the NPDW regulations.
2 .
COMMENT:
Paqe 49. cara. 4 (8.2). Shell states that, consistent with
the Proposed National Contingency Plan, Maximum Containment
Level Goals contained in the National Primary Water
Regulations are not considered either applicable or relevant
and appropriate.
01/31/90 - STATE
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y .
, .
However, CERCLA itself, which is more authoritative than a
proposed regulation, requires that remedial actions at leave
[sic] achieve MCLGs. Moreover, even the proposed NCP does
not categorically dismiss MCLGs as ARARs.
The Congressional conferees who drafted 5 121 of CERCLA
(which was part of the 1986 CERCLA amendments) have been
emphatic that CERCLA remedial actions are to achieve MCLGs
as distinguished from MCLs. A March 27, 1987 letter from
United States Representative James Florio (and other
committee conferees) to Lee Thomas, former EPA
Administrator, states:
~
.
In any circumstances in which MCLs are relevant and
appropriate, MCLGs are equally relevant and
appropriate. Section 121(d)(2)(A) states:
Such remedial action shall require a level or
standard of c'ontrol which at least attains Maximum
Contaminant Level Goals established under the Safe
Drinking Water Act and water quality criteria
established under S 304 or 303 of the Clean Water
Act, where such goals or criteria are relevant and
appropriate under the circumstances of the release
or threatened release.
The specific reference to MCLGs in the law
makes it clear that these particular
standards, where they are more stringent that
the comparable MCLs, are the primary
standards that must be attained by Superfund
cleanups of groundwater.
The reason the Congress chose to specify MCLGs is that
under the Safe Drinking Water Act, the difference
between the two requirements can be significant. In
formulating MCLs the Agency considers feasibility (and
especially cost) as well as health-based factors. MCLs
consequently may offer significantly less protection of
human health and the environment than MCLGs.
01/31/90 - STATE
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.
y-
RESPONSE:
...
As the cited statutory language reflects, MCLGs are to be
attained where they are determined relevant and accrocriate
(emphasis added). EPA, as the federal agency responsible
for implementing the statute, has issued the proposed NCP in
order to implement the statute. EPA's stated policy, as
cited in the proposed NCP, is that MCLs are generally
relevant and appropriate as cleanup standards. While
individual members of the federal legislature may have
expressed disagreement with EPA'S interpretation of the
statutory provision, this does not affect the validity of
EPA'S regulatory guidance. Individual federal and state
legislators do sometimes disagree with the implementation by
federal and state agencies of particular statutes. If the
federal or state legislature, as a body, determines that the
implementation by the agency is not what was intended by the
legislature, they may enact further legislation to clarify
the statute or redirect the agency. The cited E~A policy
has been in effect for several years and no legislative
action has been taken to require change.
T~
..
.
The State also appears to overlook the fact that this is an
interim response action, not the final response action.
There is no legislative or EPA guidance which implies MCLGs
should be applied to such interim actions which are
conducted in advance of final response actions. As the
proposed NCP makes clear, site specific determinations can
be made that establish different cleanup criteria for the
specific site. The extensive RI/EA/FS process is designed
to provide the basis for determining site specific criteria
for final response actions and that process is underway at
the Arsenal. Final cleanup criteria based upon the RI/EA/FS
01/31/90 - STATE
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p~ocess, will be established for the Arsenal consistent with
the CERCLA guidance developed by EPA.
3 .
COMMENT:
paae 50. Dara. 3: (8.2). Although the Army considers MCLs
"sufficiently protective of human health" this conclusion is
unsupported by an risk analysis. Many MCLs, arsenic for
example, represent excess cancer risks significantly greater
than 10E-6. The Congress acknowledged this fact and for
this reason provided that CERCLA cleanups should meet MCLGs
which are statutorily required to be truly protective.
~
.
RESPONSE:
See response to comments #2.
4 .
COMMENT:
Paae 51. Dara. 2 (8.2). Shell states that TBC's will be met
"if practicable." In response to an EPA comment on the
Alternative Assessment calling the language an
unsatisfactory approach, the Army stated that the section
had been revised. Shell should therefore revise the
language. Once a standard is selected, it should be met to
the maximum extent practicable.
RESPONSE:
The EPA comment cited was broader than the single matter
reflected in the State's comment and the section was revised
in response to that comment. However, the Army does not
believe that there is a requirement to attain TBCs to the
maximum extent practicable. The Army is aware of no
01/31/90 - STATE
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. ".
1".
.,.-
gufrtance in the proposed NCP or the Federal Facility
Agreement which directs that Tecs be achieved to the maximum
extent practicable. The proposed NCP, in discussing this
matter, states "[TeCs] may assist in determining, for
example, health-based levels for a particular contaminant
for which there are no ARARs or the appropriate method for
conducting an action." proposed NCP at 54 Fed. Reg. 51436.
T-
i
y
.
, .
s.
COMMENT:
paae 53. cara. 3 (8.4). Shell states that the Army found no
potential ambient air quality standards currently applicable
or relevant and appropriate to any of the volatile .or
semivolatile chemicals found in the ground water in the area
of contemplated construction. Yet, Shell states that the
selected alternative will consist of a row of alluvial
extraction wells located along the center axis of the Decp
plume. Therefore, Shell should do an ARARs analysis of
possible emissions from the R~il Yard soils, such as
trichloroethylene.
RESPONSE:
As stated in the Draft Final Decision Document, in the
context of this IRA, there is only a very remote chance of
any release of volatiles or semi-volatiles and, even if such
a release did occur, it wou~d only be intermittent and of a
very brief duration (because the activity that produced the
release would be stopped and/or modified appropriately if a
significant air emission was detected by the contractor's
air monitoring specialist). The Army and Shell have
significant experience with the construction or extraction
and reinjection wells and has not experienced any problems
from air emissions during construction of such facilities.
01/31/90 - STATE
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,-
f "
The Army is not aware of any promulgated standards that
address the emission of compounds such as TCE to the air
from activities which are similar to well construction. The
site-specific Health and Safety Plan will adequately address
these concerns. This plan"to be developed for use in the
IRA will detail operational modifications to be implemented
" in the event monitoring detects specific levels of such
emissions.
~
.
6.
COMMENT:
paae 53. cara. 4 (8.4). Shell states that any release of
volatiles orsemivolatiles during construction would be of a
brief duration since the activity causing the emission would
be stopped if a significant air emission was detected
through monitoring. Shell needs to define "significant."
RESPONSE:
The specific determination will be based upon
Safety plan for construction of this project.
Final Decision Document reflects this.
the Health and
The Draft
7 .
COMMENT:
paae 54. cara. 2 (8.4). Shell does not consider NESHAPS
relevant or appropriate because they consider the standards
inapplicable to construction activity. Shell should
consider NESHAPS relevant and appropriate if the
contaminants subject to NESHAPS are emitted in quantities
contemplated by the regulation.
01/31/90 - STATE
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~.
. ,
RgSPONSE:
.
NESHAPS are process specific standards, developed for a
narrow range of activity and based upon the specifics of the
identified process. The 'construction activity contemplated
by this IRA is so dissimilar to the processes identified in
the NESHAPS that these standards are not appropriate or
relevant to apply in the context of this IRA.
.~
8 .
COMMENT:
, -
paae 54. cara. 3 (8.4). Shell states that the provisions of
40 C.F.R. S 50.6 are considered relevant and appropriate.
However, Shell should also consider Colorado Regulation 1,
. .
which is stricter than the federal standard. The Army has
also misstated the federal standard. The correct federal
standard is that no particulate matter exceed 50 micrograms
per cubic meter, not 75, as Shell states. Also the federal
standards ~ists particulate emission for a 24 hour average
at 150 micrograms per cubic meter.
RESPONSE:
Fugitive particulate emissions requirements of Colorado
Regulation 1 were considered. The Army recognizes this
requirement and will use best practical control technology
to minimize such emissions. This section has been revised
to reflect the current standard in 40 CFR part 50.6. The
document also includes the State's specific standard in
Regulation No.1 for construction activity.
01/31/90 - STATE
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r~
T..
. -
, .
10.
9 .
CO..MMENT:
Paqe 59. cara. 3. Shell states that spent granulated
activated carbon "may" be disposed of consistent with EPA
guidance if unable to be regenerated. The spent granulated
activated carbon is a hazardous waste subject to the rules
and regulations under CHWMA/RCRA.
~
i
RESPONSE:
This language has been clarified. The spent granulated
active carbon, if sent for off-site disposal will be managed
in accordance with appropriate requirements. If it is
considered a hazardous waste it w~ll be properly manifested
and disposed of.
COMMENT:
Paqe 60. cara. 3. The Army states that the IRA was prepared
in substantive compliance with 40 C.F.R.S 1502.16, the
regulations implementing the National Environmental Policy
Act of 1969. The Army must also be in compliance with 32
C.F.R. pt. 65 which are Department of Army regulations
dealing specifically with NEPA requirements at CERCLA sites.
RESPONSE:
The Army is proceeding in accordance with the regulations
contained in 32 eFR Part 651.
01/31/90 - STATE
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RESPONSES TO COMMENT FROM SHELL OIL COMPANY
ON THE APPLICABLE OR RELEVANT AND APPROPRIATE
REOUIREMENTS FOR THE REMEDIATION OF OTHER
CONTAMINATION SOURCES (RAIL CLASSIFICATION YARD)
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1.
CO~1MENT :
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Shell agrees that certain MCLs should apply at the point of
discharge of treated water from the selected treatment
system, the Irondale Boundary System (IBS). Shell disagrees
that proposed MCLs can be selected as TBCs. The concept of
TBCs is not mandated by section 121(d) of CERCLA. Proposed
standards are particularly suspect since the purpose of
.proposed rulemaking is to receive comments prior to
finalization of standards. In addition, Shell disagrees
with the standards for benzene, T-1, 2-DCE, TCE, DBCP, 1,1-
DCE, and 1,1,2-TCA because they are driven by CAG
methodology. Further, the TBC levels for 1,1-DCE and 1,1,2-
TCA are below the GC/MS detection levels. Shell has the
same comments regarding the land disposal restrictions and
the RCRA provisions as it made for the M-1 settling basins.
!;
RESPONSE:
The Army is aware of Shell's position concerning CAG
methodology and considers this an issue which Shell, if they
desire, should pursue with the appropriate divisions within
EPA headquarters which have responsibility for developing
methodology for standard setting. The Army will continue to
follow the standards developed by EPA and apply EPA guidance
in developing approaches t~ the Arsenal cleanup. The Army
believes that use of proposed MCLs as TBCs is consistent
with current EPA guidance, as reflected in the proposed NCP.
The compounds about which Shell expresses concerns regarding
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det~ction, both have selected ARAR levels, which the system
is expected to attain. The Army appreciates Shell's
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provision of the comments they provided to EPA concerning
the applicability of land disposal restrictions to CERCLA
re~ponse actions. As Shell is ~ware, guidance in this area
is under development. The Army will act consistently with
the guidance issued by EPA concerning this issue.
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01/31/90 - SHELL
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