United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R08-90/040
March 1990
EPA Superfund
Record of Decision:
Rocky Mountain Arsenal
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50272-101
REPORT DOCUMENTATION 11. REPORT NO.
PAGE EPA/ROD/R08-90/040
2.
3. Recipient'a Acce..ion No.
i
4. TltIe.nd Subtitle
SUPERFUND RECORD OF DECISION
Rocky Mountain Arsenal (Operable
Fifth Remedial Action
7. Author(a)
5. Report Dlte
03/20/90
Unit 20), CO
6.
6. P8rformlng Orglnlzatlon Rept. No.
.. P8rfonnlng OrgalnlZltlon Heme Ind Addre..
10. ProjecllTl8klWork Unit No.
11. Conlr8cl(C) or Grlnt(G) No.
(C)
(G)
12. SponeorIng OrglniutJon Heme Ind Addreu
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type 01 Report & Period Covered
Agency
800/000
14.
15. Supplementary Note.
16. Abetrlct (Umlt: 200 worda)
The 17,000-acre Rocky Mountain Arsenal (Operable Unit 20) site 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 (isopropylmethylphosphonofluoridate). From 1947 to 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 Interim Response Actions (IRAs) were
determined necessary prior to implementing the final On-Post Record of Decision (ROD).
Operable Unit 20 (OU20), the Lime Settling Basins area, is one of several areas being
addressed as part of the Other Contaminated Sources IRA. The unlined Lime Settling
Basins occupy approximately 5 acres, and were used in the 1940s and 1950s to treat
chemical production wastewater using a precipitation process to remove metals and to
accept wastewater from pesticide production. The wastewater discharge produced lime
sludge contaminated with metals and pesticides within the basins. Sludge also was
removed from the basins for drying in an adjacent area. Investigations by the Army in
(See Attached Page)
17. Document Analyala L Deacriptol'8
Record of Decision - Rocky
Fifth Remedial Action
Contaminated Media: soil,
Key Contaminants: organics
Mountain Arsenal (Operable Unit 20), CO
sludge, gw
(pesticides), metals (arsenic, chromium, lead)
b. IcIentilier8lOpen-Ended Terme
Co COSA TI ReIdIGroup
16. AVIII.bllty Stltement
1'. Security CI... (lhil Report)
None
20. Security ClI.. (lhla Pege)
Non<=>
21. No. 01 Plge.
60
22. PrIce
(See ANSl-Z3t.1a)
See InalrucUona on Revef/Jf1
"_n~~ t'UHM 272 (4.77)
(Formerty NTIS-35)
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,
EPA/ROD/R08-90/040
Rocky Mountain Arsenal (Operable Unit 20), CO
Fifth Remedial Action
Abstract (Continued)
1987 and 1989 have characterized the nature and extent of contamination at the Lime
Settling Basins Area. The primary contaminants of concern affecting the soil, sludge,
and ground water are organics including pesticides; and metals including arsenic,
chromium, and lead.
The selected Interim Response Action for this site in~ludes consolidating 26,000 cubic
yards of contaminated sludge located adjacent to the basins with 80,000 cubic yards of
sludge located in the basins, and containing the sludge and any excavated contaminated
soil with a vegetative soil cover; hydraulically containing ground water with a slurry
wall or sheet pilings constructed around the perimeter Of the basin area; pumping ground
water to maintain an inward hydraulic gradient across the slurry wall; treating ground
water onsite, either at the CERCLA Wastewater Treatment System or at a separate onsite
treatment facility to remove organic and inorganic contaminants; and ground water
monitoring. No' cost information was provided for this interim remedial action.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific ARARs for ground water treatment will
be contained in the ROD for the CERCLA Wastewater Treatment System IRA. No
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Denver, Colorado 80237
(303) 694.2770
REQUESTS FOR COPIES OF THIS DOCUMENT
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(303) 694-2770
REQUESTS FOR COPIES OF THIS DOCUMENT
SHOULD BE REFERRED TO THE PROGRAM MANAGER
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FOR THE ROCKY MOUNTAIN ARSENAL CONTAMINATION CLEANUP,
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DEPARTMENT OF THE ARMY
PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL
COMMERCE c:rrv.~ 8C022-218O
February 28, 1990
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Interim Response Division
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Mr. Connally Mears
U :S. Environmental Protection Agency
Region VIII
One Denver Place
Suite 801
999-18th Street
Denver, Colorado 80202-2405
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Dear Mr. Mears:
Enclosed for your review are the Draft Final Decision Documents for the M-1
Settling Basins and Lime Settling Basins Interim Response Actions (IRAs) at Rocky
Mountain Arsenal in accordance with paragraph 22.9 of the Federal Facility Agreement
(FFA).
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 M-1 Settling Basins and the Lime Settling Basins where
appropriate.
In accordance with paragraph 22.10 of the FFA, Orgaruzations with standing to
invoke the dispute resolution process should advise me and my counsel in writing within
twenty days of issuance of these documents, 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 Dispution Resolution, if invoked, the Army shall issue a final IRA Decision
Document to the other Orgaruzations and Department of Interior. Unless Dispute
Resolution is invoked within the twenty day dispute period, the Army will consider the
decisions in the Draft Final Decision Documents the final decision for the M-1 Settling
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PINAL DECISION DOCUMENT
FOR THE INfERIM RESPONSE AcnON
AT THE
UME SE'ITUNG BASINS
ROCKY MOUNTAIN ARSENAL
MARCH 1990
CONTRACf NO. DAAAJ5..88...~/(XX)2
VERSION 4.0
Prepared by:
WOODWARD-CLYDE CONSULTANTS
Prepared for:
PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL
THE INFORMATION AND CONa..USIONS PRESENTED IN THIS REPORT REPRESENT THE
OFF1CIAL POSmON OF THE DEPARTMENT OF THE ARMY UNLESS EXPRESSLY MODIF1ED BY
A SUBSEQUENT DOCUMENT. THIS REPORT CONSTITUTES THE RElEVANT PORTION OF THE
ADMINISTRATIVE RECORD FOR THIS CERClA OPERABLE UNIT.
THE USE OF TRADE NAMES IN THIS REPORT DOES NOT CONSTITUTE AN OFF1CIAL
ENDORSEMENT ORAPPROV ALOFTHE USE OF SUCH COMMERClALPRODUcrs. THIS REPORT
MAY NOT BE UJIID FOR PURPOSES OF ADVERTISEMENT.
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. ."
If the Organizations or State would like to meet prior to the end of the dispute
period to discuss any concerns you may have, please contact Mr. J.D. Smith at (303) .
289-0201.
Sincerely,
eo~ ~~L~~
Deputy Program Manager
Enclosures
Copies Furnished:
Major Lawrence E. Rouse, Headquarters, Department of the Army,
ATfN: DAJA-ELL, Pentagon, Room 1C480, Washington, D.C. 20310-2210
(w/encl)
Mr. Bradley Bridgewater, Acumenics Research and Technology, Inc., DOJ Litigation
Support, 999-18th Street, Suite 501, North Tower, Denver, Colorado 80202
(w/encl)
Mr. Bruce Ray, Assistant Regional Counsel, U.S. Environmental
j' Protection Agency, One Denver Place, Suite 500, 999-18th Street,
Denver, Colorado 80202-2405 (w/encl)
Mr. Chuck Schick, Camp Dresser and McKee, 2300-15th Street, Suite 400, Denver,
Colorado 80202 (w/encl)
Mr. John Moscato, Acumenics Research and Technology, Inc., 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202 (w/encl)
Acumenics Research and Technology, Inc., Room 132, Building 111
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Interim Response Division
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Copies Furnished:
Major Lawrence E. Rouse, Headquarters, Department of the Army,
ATfN: DAJA-ELL, Pentagon, Room 1C480, Washington, D.C. 20310-2210
(w/encl)
Mr. Bradley Bridgewater, Acumenics Research and Technology, Inc., DOJ Litigation
Support, 999-18th Street, Suite 501, North Tower, Denver, Colorado 80202
(w/encl)
Mr. John Barth, Assistant Regional Counsel, U.S. Environmental
Protection Agency, One Denver Place, Suite 500, 999-18th Street,
Denver, Colorado 80202.2405 (w/encl)
Mr. Chuck Schick, Camp Dresser and McKee, 2300-15th Street, Suite 400, Denver,
Colorado 80202 (w/encl) .
Acumenics Research and Technology, Inc., Room 132, Building 111
Rocky Mountain Arsenal, Commerce City, Colorado 80022 (w/encl)
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TABLE OF roNTENTS
Section
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1.0 INTR.ODUCI'ION
2.D HISTORY OF TIlE UME SETlUNG BASINS
I-I
3.0 INTERIM RESPONSE ACI'ION OBJECl1VE
4.0 INTERIM RESPONSE ACI'ION ALTERNATIVES
2-1
3-1
4-1
4.1 NO AcrION
4.2 MONITORING
4.3 INSTITUTIONAL CONTROLS
4.4 SUBSURFACE BARRIER
4.5 SUBSURFACE BARRIER WITH GROUNDWATER EXTRAcrION AND
TREATMENT
4.6 MUL TII.A YERED CAP
4.7 EXCAVATION AND ONSITE TEMPORARY STORAGE
4.8 CONCLUSIONS . .
S.o CHRONOLOGY OF EVENTS
4-1
4-2
4-2
4-2
4-3
4-4
4-4
4-5
5-1
J
6.0 SUMMARY OF TIlE INTERIM RESPONSE ACI'ION
6.1 HEALTH & SAFETY PLAN
6-1
7.0 INTERIM RESPONSE ACI'ION PROCESS
8.0 APPUCABLE OR RElEVANT AND APPROPRIATE REQUIREMENTS FOR
TIlE REMEDIATION OF OTHER roNTAMlNATION SOURCES -
UME SETlUNG BASINS. INTERIM RESPONSE ACI'ION
6-1 .
7-1
8.1 INTRODUcrION
8.2 AMBIENT OR CHEMICAL-SPECIF1C ARARS
8.3 LOCA TION-SPECIF1C ARARS
8.4 ACI'ION-SPECIF1C ARARS
8.S COMPUANCE WITH THE OTHER ENVIRONMENTAL LAWS
9.0 samDUI..E
8-1
8-1
8-1
8-1
8-2
8-8
10.0 OONSISTENCY WITH TIlE FINAL REMEDIAL ACI'ION
11.0 REFERENCES
9-1
10-1
11-1
APPENDIX A - roMMENTS AND RESPONSES
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F1GURES
1-1 Decision F10w Chart for Other Contamination Sources IRAs
2-1 Location Map - Rocky Mountain Arsenal
2-2 M-l Settling Basins and Lime Settling Basins Area Map
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1-2
2-2
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LO
INTRODUcnON
The Interim Response Action (IRA) alternative asseument and decision process for the Lime Settling Basins
at the Rocky Mountain Arsenal (RMA) is being conducted as part of the IRA process for RMA in aca>rdance
with the Federal Facility Agreement and Technical Program Plan.
Determinations concerning the implementation of this IRA have been reached through a consideration of the
objectives of Sections 2.3 (a), 22.5, and 22.6 of the Federal Facility Agreement and by application of the Decision
Flow Chart for Other Contamination Sources mAs adopted by the Organizations and the State in the June 7,
1989 subcommittee meeting (Figure 1-1).
,
....
Alternatives have been reviewed based on their overall protectiveness of human health and the environment;
compliance to the maximum extent practicable with Applicable or Relevant and Appropriate Requirements
(ARARs); reduction in mobility, toxicity, or volume; short-term and long-term effectiveness; implementability;
and cost-effectiveness. The preferred IRA consists of relocation of sludge material, which had been deposited
around the Lime Settling Basins, to the Lime Settling Basins area; construction of a 360-degree subsurface
barrier around the basins; construction of a soil and vegetative cover over the material; and installation of a
groundwater extraction system.
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SITE CHARACTERIZAilON
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INTERIM RESPONSE
ACTION SELECTION
NO
OR DATA
INADEQUATE
NO
Job No. : 22238-4300
Prepored by: K.A.S.
Dote: 12/18/89
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MONITORINGI MAINTENANC E
NO
YES
DECISION FLOW CHART FOR OTHER
CONTAMINATION SOURCES IRAs
Figure 1-1
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2.0
HISTORY OF TIlE LIME SE'lTUNG BASINS
Roclcy Mountain Arsenal (RMA) occupies more than 17,000 aaes (approximately 27 square miles) in Adams
County, directly northeast of metropolitan Denver, Colorado (FJgW'e 2-1). The property was purchased by the
U.S. government in 1942 for use in World War n to manufacture and assemble chemical warfare materials, such
as mustard and lewisite, and incendiary munitions. Starting in the 195Os, RMA produced the nerve agent GB
(isopropyl methylpbospbonofluoridate) until late 1969. A significant amount of chemical warfare materials
destruction took place during the 19505 and 1960s. After 1970, RMA was primarily involved with the destruction
of chemical warfare materials. The last military operations at RMA ended in the early 19805. In November
1988, the RMA was reduced to inactive military status reflecting the fact that the only remaining mission at the
Arsenal is contamination cleanup. In addition to these military activities, major portions of the plant facilities
were leased to private industries, including Shell Oil Company, for the manufacture of various insecticides and
herbicides, between 1947 and 1982.
.
,
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During the 19405 and 19505, wastewater from the production of Army agents was routinely treated prior to
discharge to unlined evaporation ponds. This treatment involved the addition of lime to the wastewater to
precipitate metals and reduce the arsenic concentration. Wastewaters produced in the Soutb Plants were
channelled through the Lime Settling Basins prior to gravity disclwge to Basin A The precipitation process
produced a lime sludge that contained elevated levels of beavy metals, arsenic, and mercury. Subsequent
discharges of pesticide production wastewater resulted in the addition of pesticides to the Lime Settling Basins
sludge. The Lime Settling Basins were taken out of service in 1957. F'JgW'e 2-2 shows the location of the Lime
Settling Basins.
.~
A number of studies have been completed to characterize the nature and extent of contamination in the soil,
sludge, and groundwater in the vicinity of the Lime Settling Basins (ESE 1987a and 1987b; Ebasco 1989; wee
1989). Results of these studies are consistent with the site history. The soil and sludge contain elevated levels
of organochlorine pesticides, organosulfur compounds, arsenic, mercury, and ICP metals (cadmi~ chromium,
copper, lead, and zinc). The Lime Settling Basins occupy about 5 aacs. For the purpose of the alternatives
as~cclQent, it was estimated that approximately 80,000 cubic yards of sludge withiD the basins, pJus approximately
. 26,000 cubic yards of sludge that had been placed adjacent to the basins for drying, would be addressed by this
IRA.
(~3P) (LS8.URA) (tZllrtf'JO) eRMA)
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December 7th Avenue
/ 2~ 24 19 20
/ 21 26 25 30 29
33 34 35 .M 3. 52
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ROCKY MOUNTAIN ARSENAL.
KEY MAP
Job No. : 22238-4300
Prepa,..d by: K.A.S
DOle: 12/18/89
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LIME SETTLING BASINS
M-1 SETTLING BASINS
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0 100 200 400
SCALE IN FEET
M-1 SETTLING BASINS AND
LIME SETTliNG BASINS AREA MAP
F"IQure 2-2.
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On February 1, 1988, a proposed Consent Decree was lodged in the c.ase of United States v. Shell Oil Company
with the U.S. District Court in Denver, Colorado. The proposed Consent Decree was revised after publi~
comments were received, and a modified proposed Consent Deaee was lodged with the Court on June 7, 1988.
In February 1989, a Federal Facility Agreement was entered into between five federal agencies: the
Environmental Protection Agency, the Army, the Department of the Interior, the Department of Health and
Human Services, and the Department of Justice, which established procedures for implementing the Arsenal
cleanup program as specified in the Technical Program Plan, and incorporated many provisions of the modified
proposed consent deaee. The Army and Shell Oil Company agreed to share certain costs of the remediation
to be developed and performed under the oversight of the U.S. Environmental Protection Agency, with
opportunities for participation by the State of Colorado. The long-term remediation is a complex task that will
take several years to complete. The Federal Facility Agreement specifies 13 Interim Response Actions (IRAs)
determined to be necessary and appropriate. The -Remediation of Other Contamination Sources. is one of the
13 IRAs. The Lime Settling Basins is one of several sites. being addressed by the remediation of other
contamination sources IRA. The action at this site consists of assessment and, as necessary, the selection and
implementation of an interim action.
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3.0
INTERIM RESPONSE ACI10N OBJECI1VE
The objective of the Interim Response Action (IRA) Alternatives Assessment for the Lime Settling Basins is to
assess whether immediate action at this site is appropriate and to recommend, if necessary, an IRA alternative
to mitigate the threat of release from the Lime Settling Basins on an interim basis, pending determination of the
final remedy in the Onpost Record of Decision (ROD).
The IRA ahernatives have been evaluated based on the following criteria:
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Overall protectiveness of human health and the environment
Compliance with Applicable or Relevant and Appropriate Requirements (ARARs) to the maximum
extent practicable
L..
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Reduction of mobility, toxicity, or volume
L
.
Short-term and long-term effectiveness
.
Implementability
, .
.
Cost
. ..
This F"maJ Decision Document prOYides a summary of the alternative technologies considered, a chronology of
the significant events leading to the initiation of the ~ a summary of the preferred alternative for this IRA
project, and a summary of the ARARs (legal and regulatory standards, aiteria, or limitations) associated with
the program.
As specified in the Federal Facility Agreement, this IRA will, by containment of a contamination source, to the
maximum extent practicable, be consistent with and contnoute to the efficient performance of the F"maJ Response
Action.
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4.0
INTERIM RESPONSE AcnON ALTERNATIVES
This section desaibes the interim response action (IRA) alternatives developed in the IRA Alternatives
Assessment for the Lime Settling Basins (WCC 1989a). These alternatives included:
.
No action
Monitoring
Institutional controls
Subsurface barrier with cap
Subsurface barrier with groundwater extraction and treatment
Multilayered cap
Excavation and onsite temporary storage
.
.
.
.
.
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All of these alternatives were subject to an evaluation in the IRA Alternatives Assessment. The IRA Alternatives
Assessment for the Lime Settling Basins concludes that there may be some long-term benefit in performing an
IRA now. Treatment after the arsenic has spread in the groundwater becomes both more complex and costly
insofar as a larger area must be addressed.
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.
Following is a description and a brief summary of the evaluation of each alternative. All of the alternatives can
be designed and implemented to meet Applicable or Relevant and Appropriate Requirements (ARARs) to the
maximum extent practicable. Details of the evaluation can be found in the IRA Alternatives ~c.cment for this
site (WCC 1989a).
4.1 NO AcnON
~
This alternative consists of taking no action to contain or treat contaminated soil and sludge at the Lime Settling
Basins. This alternative is not considered protective of human health and the environment It would Dot reduce
contaminant mobility, toxicity, or volume. This alternative has no short-term impacts., however, it also has DO
long-term effectiveness. It can be easily implemented at DO cost. The DO actioD alternative would Dot be
inconsistent with any final remedy at the site.
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4.2 MONITORING
This alternative consists of conducting upgradient and downgradient groundwater sampling and analysis.
Monitoring would allow continued tracking of cont~min~nt movement, thereby providing additional information
which can be used to continue to evaluate the protection of human health and the environment. Monitoring
would not reduce contaminant mobility, toxicity, or volume. It would have minimal short-term impacts on
workers during monitoring well installation, which could be mitigated through the use of personal protective
equipment. The long-term effectiveness of this alternative is limited to its use as an indicator of future impact
at sensitive receptors. It can be easily implemented at relatively low cost. The monitoring alternative would not
be inconsistent with any final remedy at the site. Groundwater monitoring would also be included in all following
alternatives.
4.3 INSTITlmONAL roNTROLS
.
.A
. This alternative consists of constructing a chain-link fence with controlled aa:ess points around the Lime Settling
Basins. In addition, groundwater monitoring would be conducted. The monitoring aspect of this alternative
would allow continued tracking of cont3min~nt movement, thereby providing additional information which can
be used to continue to evaluate the protection of human health and the environment. Monitoring would not
reduce contaminant mobility, toxicity, or volume. This alternative would have minimal short-term impacts during
fence construction, which could be easily mitigated through the use of personal protective equipment. Since .
RMA currently has limited access maintained by physical barriers and security personnel, additional site
restrictions would be of limited effectiveness. It can be easily implemented at relatively low cost. These
institutional controls would not be inconsistent with any final remedy at the site. .
4.4 SUBSURFACE BARRIER WITH CAP
This alternative consists of constructing a subswface barrier, such as a slurry wall or sheet pilings, around the
Lime Settling Basins. ID addition, groundwater monitoring would be conducted. The subswface barrier would
be anchored a minimum of S feet into the Denver Formation, which would provide a relatively impermeable base
for the contained area. This would limit horizontal migration of contamination as a result of the alluvial
groundwater flow that is in contact with the Lime Settling Basins.
Lime sludge, currently stockpiled in areas adjacent to the basins, would be relocated back into the settling basins
area. A multilayered cap would then be constructed over the Lime Settling Basins. For the purposes of this
study only, it has been assumed that the cap would consist of, from the base upwards, an 18-inch-thick layer of
low permeabiliry clay, a flexible membrane liner, a synthetic drainage net, a geotextile filter fabric, and a 1-foot
4-2
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Woodward. Clyde Consultants
thick protective soil layer. The cap would be sloped from the center of the basins to facilitate runoff. The cap
would reduce infiltration of precipitation and surface water.
This alternative is considered protective of human health and the environment, since the waste material is
isolated from the surrounding environment. Both vertical and horizontal contaminant migration would be greatly
inhibited. However, this alternative does not affect the toxicity of the material and may actually inaease the
volume of material that may ultimately require remediation, since some of the containment materials may come
in contact with the sludge. Any minimal short-term impacts to workers or the community could be addressed
through the use of personal protective equipment and engineering controls.. The long-term effectiveness of this
alternative is limited since this is a containment technology which does not actually remove or treat the source
of contamination. This alternative could be readily implemented at a relatively moderate cost. Containment
would be consistent with the final remedy because it would reduce potential contaminant migration.
4.5 SUBSURFACE BARRIER wmI GROUNDWATER EXTRAcnON AND TREATMENT
~
This alternative consists of constructing a subsurface barrier, such as a slurry wall or sheet pilings. around the
Lime Settling Basins. Lime sludge, currently stockpiled in areas adjacent to the basins, would be relocated back
into the Lime Settling Basins area. The subsurface barrier would be anchored a minimum of S feet into the
Denver Formation, which would provide a relatively impermeable base for the contained area. This would limit
horizontal migration of contamination as a result of alluvial groundwater flow through the area. A soil and
vegetative cover would be constructed over the area to reduce infiltration. In addition, groundwater monitoring
would be conducted.
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A groundwater extraction trench or wells would be constructed within the subsurface barrier. Sufficient
groundwater would be periodically extracted from within the barrier, as necessary, to maintain an inward
hydraulic: gradient aaoss the barrier. This would help limit the continued migration of contaminated alluvial
groundwater, that might aa:umulate as a result of infiltration, aaoss the barrier, and inaease the efficiency of
the barrier.
Any extracted groundwater would be treated to remove organic: and inorganic: contaminants. Treatment would
be performed either at the CERa.A Wastewater Treatment System, or at a separate treatment system
implemented and opererated for this IRA.
This alternative is considered protective of human health and the environment. The subsurface barrier would
isolate the sludge from the alluvial aquifer, while the groundwater extraction and treatment would remove
contaminants from the aquifer. Therefore, the mobility of contaminants would be reduced. The toxicity and
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volume of contaminants may also be reduced through treatment of extracted groundwater. The implementation
of this alternative could be accomplished with minimal short-term impacts that could be mitigated through the
use of personal protective equipment and engineering controls. Since this is a containment alternative, its long-
term effectiveness is limited. It could be readily implemented with standard construction techniques at a
relatively moderate cost. This containment alternative would be consistent with the final remedy because it would
reduce potential contaminallt migration.
4.6 MUL1"IlA YERED CAP
This alternative would consist of constructing a multilayered cap over the Lime Settling Basins as described in
subsection 4.4. In addition, groundwater monitoring would be conducted. Lime sludge currently stockpiled in
areas adjacent to the Lime Settling Basins would be returned to the basins area. The cap would inhibit
infUtration of precipitation and surface water. However, a cap would not address the horizontal flow of the
alluvial aquifer through the Lime Settling Basins, which is probably a more significant migration pathway in this
area than downward migration by inflltration. .
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This alternative is considered protective of human health and the environment. The cap would limit the
downward mobility of the contaminants. However, it would have no effect on the toxicity of the sludge and may
actually increase the volume of contaminated material" that would ultimately havc to be treated, since some of
the cap materials would come in contact with the sludge. There would be minimal short-term impacts associated
with the implementation of this alternativc, which could be addressed through the use of personal protective
equipment and engineering controls. Since this is a containment alternative, the long-term effectiveness is
limited. This alternative could be implemented with straightforward construction techniques at a relatively low
cost. Containment would be consistent with the final remedy because it would reduce potential contaminant
migration.
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4_7 EXCAVATION AND ONSlI'E TEMPORARY STORAGE
This alternative consists of ezcavating the conhnninated soil and sludge in the Lime Settling Basins and placing
the material in an onsite temporary waste pile. In addition, groundwater monitoring would be conducted. The
temporary waste pile would be constructed with a clay liner and cap, IS well as a synthetic: liner, and leachate
monitoring and collection sump. This alternative would isolate the contaminated material from the environment
until a final remedy is selected.
" This alternative is considered protective of human health and the environment, ~ce the contaminated soil and
sludge would be effectively isolated from the environment. The mobility of the contamination would be reduced.
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.
However, the toxicity of the material would remain unchanged and the volume of material that would ultimately
require treatment would increase, since some of the waste pile construction materials would require subsequent
remediation. This alternative would have some short-term imp~cts that could be addressed through the use of
personal protective equipment for construction persoDDe~ and engineering controls for odor and dust control.
Since this is a containment alternative, the long-term effectiveness is limited. A final remedy would probably
require the treatment and possibly rehandling of the contaminated material. This alternative would preclude the
use of an in situ treatment alternative for the final response action at this site. The operation could be
implemented at a relatively high cost. Excavation with onsite temporary storage would be consistent with the
Cmal remedy insofar as it would reduce potential contaminAnt migration. However, this alternative would
preclude the use of an in situ treatment technology for the final response action at this site.
. .
4.8 CONa..USIONS
..
The preferred alternative is construction of a subsurface barrier, such as a slurry wall or sheet pilings. and
vegetative cover around the Lime Settling Basins. Groundwater will be extracted and treated, as necessary, to
maintain an inward hydraulic gradient across the subsurface barrier. This containment alternative reduces the
vertical and horizontal migration of contaminants. This alternative can be easily implemented since it is based
on demonstrated technology that has been widely used. The long-tcrm effectivencss of this altcrnative is
somcwhat limited because it is a containment technology that does not actually remove or treat the souce of
contamination. Periodic reevaluation would be necessary to assess the continued cffectiveness of this containment
system. This reevaluation would be based, in part, on the groundwater monitoring program that will be part of
this altcrnative.
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Containmcnt is an appropriate IRA for the Limc Settling Basins because it will inhibit further migration of
contaminants. In addition, the treatment technologies that may be feasible for the types and concentrations of
contaminants at this site eithcr have not been well demonstrated or are not cost-effective as an interim action.
Containment is consistent with the final remedy because it will reduce potential contAminAnt migration and, if
treatment is selected for the final response, the COf'tAminAted material will have already been contained and
isolated. In addition, containment will not preclude the possible use of an in situ treatment alternative for the
final response action at this site.
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s.o
CHRONOLOGY OF EVENTS
The significant events leading to the proposed decision to contain soils in the Lime Settling Basins, as descn"bed
in Section 6.0 of this report, are presented below.
Date
June 1987 .
E~
State of Colorado, Shell Oil Co.. EP A, and the Army develop and agree in a June 1987
report to the court to a prospcctjve hot spot list which identifies candidate interim
response actions (IRAs) to be conducted. The hot spot list consists of five areas (the
Section 36 Trenches, the Section 36 Lime Pits, the M-1 Settling Basins, the Motor Pool
Area, and the Railroad Housing Track in the Rail Classification Yard) referred to as
.Other Contamination Sources. in the proposed Consent Deaee (Section 9.1, paragraph
I), and in the Federal Facility Agreement, paragraph 22.1 (1).
January 31, 1989
The Army instructs Woodward-Clyde Consultants (Wee) to develop plans for interim
response investigation work in response to the hot spOt list. Interim action investiga-
tion work includes the Lime Settling Basins.
.J
April 13, 1989
A draft final Task Plan, which includes the Lime Settling Basins, is submitted by the
Army to the Organizations and the State for comment.
April 17, 1989
Field investigations begin for the other contamination sources IRA. Work includes
investigation of contaminant source(s) within the Lime Settling Basins.
June 29, 1989
A final Task Plan is issued by the Army with comments incorporated.
August 15, 1989
Draft F'mal Alternatives As~umeDt of Interim Response Actions for Other
Contamination Sources. Lime Settling Basins and draft ARARs arc distn'buted by the
Army to the Organizations and the State for commeDt.
September 18, 1989
Field investigation completed.
November 3, 1989
F'mal Alternatives ~ument of Interim RespoliSC Actions for Other Contamination
Sources. Lime Settling Basins is distn'buted by the Army to the Organizations and the
State with comments incorporated.
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November 27,1989
December 7,1989
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February 28, 1990
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Draft rmal Results of Field and Laboratory Investigations Conducted for the
Remediation of Other Contamination Sources Interim Response Action is distributed
by the Army to the Organizations and the State.
Proposed Decision Document for the InterUp Response Action at. the Lime Settling
Basins at the Rocky Mountain Arsenal is distributed by the Army to the Organizations
and the State for commenL
Public meeting on the proposed Decision Document for the Interim Response Action
at the Lime Settling Basins at the Rocky Mountain Arsenal.
Draft rmal Decision Document for the Interim Response Action at the Lime Settling
Basins at the Rocky Mountain Arsenal is distributed by the Army to the Organizations
and the State with comments incorporated.
The Decision Document for the Interim Response Action at the Lime Settling Basins
at the Rocky Mountain Arsenal is finalized and distnDuted by the Army to the
Organizations and the State.
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6.0
SUMMARy OF TIm INTERIM RESPONSE ACI10N
The preferred alternative is COnstruction of a subsurface barrier, such as a slurry wall or sheet pilings, with a soil
and vegetative cover at the Lime Settling Basins. Groundwater will be extracted and treated, as necessary, to
maintain an inward hydraulic gradient aa-ass the barrier. This containment alternative reduces the vertical and
horizontal migration of contaminants. This alternative can be easily implemented because it is based on
demonstrated technology that has been widely used. The long-term effectiveness of this alternative is somewhat
limited because it is a containment technology that does not ac:rually remove or treat the source of contamination.
This alternative consists of constructing a 360-degree subsurface barrier around the Lime Settling Basins. The
barrier will be anchored a minimum of 5 feet into the Denver Formation. Because the Denver Formation is
relatively impermeable in this area, anchoring the barrier into the Denver Formation, together with a soil and
vegetative cover, will inhibit potential downward and lateral contaminant migration. This will limit horizontal
migration of contamination as a result of alluvial groundwater flow through the area. Lime sludge, currently
stockpiled in areas adjacent to the basins, will be relocated back into the settling basins area prior to barrier
construction. Soils excavated during barrier construction will be placed within the boundaries of the barrier and
covered with the soil and vegetative cover.
A soil and vegetative cover will then be constructed over the Lime Settling Basins. The cover will be sloped from
the center to facilitate runoff. The cover will inhibit continued downward migration of contaminants to the
groundwater through surface infIltration.
A groundwater extraction trench or wells will be constructed within the subsurface barrier. Sufficient
groundwater will be periodic:aJ.]y extracted from within the barrier, as necessary, to maintain an inward hydraulic
gradient aa-oss the barrier. This will help limit the continued migration o( contaminated alluvia) groundwater,
that might accumulate as a result o( infiltration, aa-ass the barrier, and ina-ease the efficiency o( the barrier.
AzJy extracted groundwater will be treated to remove organic and inorganic cont~lII"inAnts. Treatment will be
performed either at the CERClA Wastewater Treatment System or at a separate treatment facility implemented
and operated (or this IRA.
6.1 HEALm ct. SAFETY PlAN
A Health & Safety Plan has been developed (or the prevention of occupational injuries and illnesses during field
activities at RMA. This plan addresses health and safety requirements of contractors and their authorized
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subcontractors. Compliance with this plan will be compulsory and the contractors will be responsible for self.
enforcement and compliance with this plan. The Health & Safety Plan was developed takmg into considerauon
known hazards as well as potential risks. Comprehensive environmental monitoring and site-specific personal
protection are combined in an effort to best protect workers.
A site-specific Health & Safety Plan for work to be performed in the Lime Settling Basins Area will be
developed. .
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7.0
INTERIM RESPONSE AcnON PROCESS
With respect to the Interim Response Action (IRA) for the remediation of other contamination sources for the
Lime Settling Basins at Rocky Mountain Arsenal (RMA), the IRA process is as follows:
1.
The scope of the IRA is described in the June 5, 1987 report to the Court of the United States (the
Army and EPA), SheU. and the State in United States v. Shell Oil Co. A similar description is included
in the proposed Consent Decree, paragraph 9.1 (l), and the Federal Facility Agreement (FFA),
paragraph 22.1 (I).
2.
The Organizations and DOl shall have the opportunity to participate, at the RMA Committee leve~ in
the identification and selection of Applicable or Relevant and Appropriate Requirements (ARARs) that
may be applicable to lRAs.
The Army issues the proposed Decision Document for the IRA for the interim remediation of other
contamination sources, Lime Settling Basins, for a 3O-day public comment period. During the 3O-day
comment period, the Army will hold one public meeting addressing the IRA decision. The proposed
Decision Document is supported by an administrative record.
Promptly after the close of the comment period, the Army shall transmit to the other Organizations,
Department of Interior (DOl), and the State, a Draft rlOallRA Decision Document for the remediation
of other contamination sources, Lime Settling Basins.
5.
Within 20 days after the issuance of a Draft rlOallRA Decision Document for the interim remediation
of other contamination sources, Lime Settling Basins, an Organization (including the State if it has
agreed to be bound by the Dispute Resolution process, as required by the FFA or DOl under the
provisions set forth in the FFA) may invoke Dispute Resolution.
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, the Army shall issue a rmal IRA Decision
Document to the other Organizations, 001, aDd the State. The Army shall also notify the public of the
availability of the rlOal IRA Decision Document with the supporting. administrative record. Only
preliminary .dcsign work for the IRA may be conducted prior to the issuance of the rlOallRA Decision
Document.
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7.
The IRA Decision Document for the remediation activity at the Lime Settling Basins will be subject to
judicial review in accordance with Section XXXIX of the Federal Facility Agreement except where such
review is barred by Sections 113 and 121 of the Comprehensive Environmental Response, Compensation
and Liability Act of 1980 (CERCLA), as amended, 42 U.S.C. Sections 6913 and 9621.
8.
Following issuance of the rmal IRA Decision Document, the Army shall be the lead party responsible
for designing and implementing the IRA in conformance with the Decision Document. The Army shall
issue a draft IRA Implementation Document to the DOl, the State, and the other Organizations for
review and comment. The draft implementation document shall include final dra'!vings and specifications,
fmal design analysis, a cost estimate, and IRA deadlines for implementation of the IRA.
9.
If any organization (including the State) or the DOl, believes that the IRA is being designed or
implemented in a manner that will not meet the objectives for the IRA set forth in the rmal IRA
Decision Document, or is otherwise not being properly implemented, it may so advise the others and
shall recommend how the IRA should be properly designed or implemented. Any organization
(including the State, if it has agreed to be bound by the process of Dispute Resolution, as required by
the FFA, or the DOl under the circumstances deCmed in the FFA) may invoke Dispute Resolution to
resolve the disagreement.
10.
As Lead Party for the design and implementation of this IRA, the Army will issue the Cmal
implementation document, as described above, and will be responsible for implementing the IRA in
accordance with the IRA Implementation Document.
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8.0
APPUCABLE OR RELEVANT AND APPROPRIATE REQUIREMENTs
FOR TIlE REMEDIATION OF OTHER CONTAMINATION SOURCES-
l.JME SE1TUNG BASINS, INTERIM RESPONSE ACI10N
8.1INTR.ODUcnON
i -
These Applicable or Relevant aDd Appropriate Requirements (ARARs) address a specific area identified
for interim remediation prior to the issuance of I Record of Decision (ROD) for the Onpost Operable Unit
of the Rocky Mountain Arsenal The Lime Settling Basins will be surrounded by a 360 degree subsurface
barrier and covered with a low permeability layer to inhibit infiltration and provide containment during the
interim period. Further remedial action will be addressed in the ROD for the On post Operable Unit of the
Rocky Mountain Arsenal. .
8.2 AMBIENT OR CHEMICAL-SPECIF1C 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 chemic:aIs of concern in the designated media or indicate an appropriate level of
discharge based on technological considerations. .
~
The objectives of this IRA are discussed in the rmaJ Assessment Document and the rmal Decision
Document. This IRA will be implemented prior to the final remediation to be undertaken in the context
of the Onpost Operable Unit ROD. This IRA will not involve an interim remediation of soils or
groundwater, but will utilize a containment approach to control the contaminants during the interim pcriod,
leaving further remediation to be determined in the Onpost ROD. Dewatering may be conducted pursuant
to this IRA. Any liquids generated through dewatering are intended to be treated at the CERCLA
Wastewater. Treatmcnt System and chemical-specific ARARs for liquid treatment will be reflected in the
Decision Document concerning that IRA. No ambient or chemical-specific ARARs were identified
concerning levels of contaminants for soils which are placed in such containment struc::turcs.
. 8.3 LOCA110N-SPECFIC ARARS
Location-specific requirements set ,restrictions on activities, depending on the characteristics of the site or
the immediate environment, and function like action-specific requirements. Alternative remedial actions may
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be restricted or precluded, depending on the location or characteristic of the site and the requirements that
apply to it.
Paragraph 44.2 of the Federal Facility Agreement provides that -wildlife habitat(s) shaD be preserved and
managed as necessary to protect endangered species of wildlife "to the ~ent required by the Endangered
Species Act (16 U.s.C. 1531 ~.), migratory birds to the ~ent required by the Migratory Bird Treaty
Act (16 U.s.C. 703 ~.), and bald eagles to the ~eDt required by the Bald Eagle Protection Act, 16
U.s.C. 688 ~..
While this provision is not an ARAR, the statutes reflected in it are. ARARs, applicable to this interim
action, and must be complied with. Based on where this containment system is to be located 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.
L..
. The Army considers relevant and appropriate and will comply with 40 CFR 6.302(a) and (b) concerning the
location of this containment system, avoiding the construction of this system in a manner that would have
an adverse impact on wetlands or be within a flood plain, where possible.
v
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 is included in this IRA.
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 cont~ of this IRA.
8.4 AC110N-SPEaFIC ARARS
8.4.1 DescrintiQn
Performance, design, or other action-specific requirements set controls or restrictions On activities related
to the management of hazardous substances, poUutants, or contaminants. These action-specific requirements
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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.
8.4.2 Construction Qf Containment SYStem
8.4.2.1 Air Emissions
On the limited possibility that there may be air emissions during the course of the construction of this
containment system, the Army has reviewed all potential ambient or chemical-specific air 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 soils or groundwater found in the area in which construction is contemplated.
J
In the context of this IRA, there is only a limited 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 sigDificant air emission was detected
by the contractor's air monitoring specialist). The Army has significant experience with the construction of
extraction wells, reinjection wells, and slurry walls which are similar to the construction of the subsurface
barrier which is included in this IRA, 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 of such emissions.
i.";
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,
Dot to construction activity. These staDdards were not considered relevant and appropriate because they
were developed for manufacturing proc~~s. which are significantly tliccimi12f' to the shon-term construction
activity contemplated by this IRA.
The provisions of 40 CPR 50.6 will be considered relevant and appropriate. This standard is not applicable
because it addresses Air Quality Control Regions, which arc areas significantly larger than and different from
the area of concern in this IRA. Pursuant to this regulation, there will be no particulate matter transponed
by air from the site that is in excess of 50 miaograms per cubic meter (annual geometric mean) and 150
miaograms per cubic meter (maximum 24-hour concentration) will not be exceeded more than once per
year.
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8.4.2.2 Worker Protection
The provisions of 29 CFR 1901.120 are applicable to worke~s 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.)
8.4.2.3 General Construction Activities
The following performance, design, or other action-specific State ARARs have been preliminarily identified
by the Army as applicable to this portion of the IRA and more stringent than any applicable or relevant and
appropriate federal standard, requirement, aiterioD, or limitation:
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. Colorado Air Pollution Control Commission Regulation No.1, 5 CCR 1001-3, Part m(D)(2)(b),
Construction Activities:
a.
Applicability - Attainment and Nonanainment Areas
b.
General Requirement - Any owner or operator engaged in clearing or leveling of land or owner
or operator of land that has been cleared 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 m.D. of this regulation.
c.
Applicable Emission l.imitation Guideline - Both the 20% opacity and the no off-property
transport emission limitation guidelines shall apply to COnstruction activities; cxccpt 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 mD. of this regulation. (Cross Reference: Subsections e. and f. of Section mD.2
of this regulation).
d.
Control Measures and Operating Procedures - Control Measures or operational procedures to
be employed may include but are not necessari1y limited to planting vegetation cover, providing
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synthetic cover, watering, chemical stabilization, furrows, compacting, minimizing disturbed area
in the winter, wind breaks, and other methods or techniques.
. Colorado Ambient Air ~uality Standards, S CCR 1001-14, Air ~uality Regulation A, Diesel-Powered
Vehicle Emission Standards for VISible Pollutants:
a.
No person shall emit or cause to be emitted into the atmosphere from any diesel-powered vehicle
any air contamin::lnt, for a period greater than 10 coDSealtive 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 B below.
b.
No person shall emit or cause to be emitted 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 de~ty as to obscure an observer's vision to a degree in excess of 50% opacity.
Co
Diesel-powered vehicles excee.tfing these requirements shall be exempt for a period of 10 minutes,
if the emissions are a dired result of a cold engine start-up and provided the vehicle is in a
stationary position.
d.
This standard shall apply to motor vehicles intended, designed, and manufactured primarily for
use in carrying passengers or cargo on roads, streets, and highways.
. Colorado Noise Abatement Statute. C.R.S. Section 25-12-103:
I)
a.
Each activity to which this article is applicable shall be conduded 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 shaII constitute prima facie
evidence that such noise is a public auisance:
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7:00 a.m. to
next 7:00 p.m.
7:00 p.m. to
next 7:00 a.m.
Residential 55 db(A)
Commercial 60 db(A)
Light Industrial 70 db(A)
Industrial 80 db(A)
50 db(A)
55 db(A)
65 db(A)
75 db(A)
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b.
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 any
one-hour period.
c:.
Periodic:, impulsive, or shrill noises shall be considered a public: nuisance when such noises are at
a 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.
e.
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.
f.
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.!. this IRA will .
employ the specified methods for minimi7ing 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 a manner that will produce emissions
in excess of those specified in these standards.
The noise levels pertinent for COnstruction activity provided in C.R.S. Section 25-U-I03 will be attained in
accordance with this applicable Colorado statute.
8.4.2.4 Wetlands ImDlications
Through estimation of the area where the containment system will be located, the Army does not believe
that any wetlands couJd be adversely affected. However, until. final design is selected and . final sitting
decision made, it c:azmot be definitively determined that DO impact on wetlands will oa:ur. If the final site
selection and/or design resuJts in an impact OD wetlands, the Army will review the regulatory provisions
concerning wetlands impact and other appropriate guidance, and will proc:ccd in a manner consistent with
~1~3P) (UNJRA) (rtll'r1/9(J)
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Woodward-Clyde Consultants
those provisions. Coordination will be maintained with the U.S. Fish and Wildlife Service concerning any
potential impacts on wetlands.
8.4.2.5 Land Disposal Restrictions and Removal of Soil and Debris
There are no action-specific ARARs that pertain to the excavation and relocation of soil to the Lime Settling
Basins area during the construction of this containment system which can be specific:a1ly identified at this
time. The relocation of lime sludges to the Lime Settling Basins will occur within the -area of
contamination", as defined in current EPA guidance. The Army will act consistent with the EPA guidance
in effect for CERCLA actions at the time that construction and soil relocation occur. Construction debris
will be managed consistent with the EP A guidance then in effect at the time it is generated.
EPA is currently developing guidance concerning the Land Disposal Restrictions (LDR), particularly the
applicability of these to CERCLA actions. While guidance is limited, the Army has not determined that any
waste subject to LDR will be present in the 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 restricted disposal waste is present, the Army will act in a manner consistent with
EP A guidance in effect at the time of the action for the management of such materials within the context
of CERCLA actions.
Although removal of soil from the area where the containment system will be located, without returning that
soil to the area, 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 VA Region vm Procedure for Handling of Materials from DriIIiog, Trench
Excavation and Decontamination during CERCLA RIfFS Operations at the Rocky Mountain Arsenal:
Soils generated by excavation during the course of this IRA, either at surface or subsurface, may be returned
to the location &:om which they originated (i.e., last out, first in). Any materials remaining after completion
ofbackf'illing that are suspected ofbeiDg contAminAted (based on field screening tedmiques) will be properly
stored, sampled, analyzed, and ultimately disposed as CERCLA hazardous wastes, as appropriate.
Throughout the construction of this containment system, the Army will comply with EP A guidance then in
effect concerning the management of CERCLA hazardous substaDces during CERClA remedial actions.
For material determined to be hazardous waste resulting uom construction activities, substantive RCRA
provisions are applicable to their management. These substantive provisions include but are not limited to:
40 CFR Part 262 (Subpart C, Pre-Transport Requirements), 40 CFR part 263 (Transporter Standards), 40
8-7
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Woodward-Clyde Consultants
.
.
CFR Part 264 (Subpart I, Container Storage and Subpart 1.., Waste Piles) and any more stringent substantive
provisions of comparable state regulations contained in 6 CCR 1007-3. The specific substantive standards
applied will be determined by the factual circumstances of the acalIDulation, storage or disposal techniques
actually applied to any such material.
'"
8.4.2.6 Soil Treatment and Disposal
These proposed remedial actions do not include the possibility for onsite or offsite disposal of soils or
contaminated material excavated pursuant. to this IRA, except during construction activities which are
discussed above.
8.4.2.7 Construction of Slum' Wall and Cover
1
i.
U
The cover to be constructed pursuant to this IRA is not intended to be a permanent cover of the same type
as utilized for the closure of landfills. This cover will minimi7.e infiltration and promote drainage away from
the Lime Settling Basins. The substantive standards contained in 40 CFR t 264310, specifically those
requirements contained in subsections a(2)-(4) and b(l) and (4), which describe necessary standards and
actions concerning landfill covers, are considered relevant ~d appropriate to apply to the construction and
continued operation of the cover constructed pursuant to this IRA.
8.5 COMPUANCE WITH TIm OTHER ENVIRONMENTAL LAWS
As is evident from the various portions of this document, this IRA was prepared in substantive compliance
with 40 CFR 1502.16 (the regulations implementing the National Environmental Policy Act of 1969).
. .
8-8
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Woodward. Clyde Consultants
9.0
SCHEDULE
The Draft Implementation Document is scheduled for completion on November 1, 1990. The construction
schedule will be contained in the Draft Implementation Document for this Interim Response Action (IRA). This
milestone has been developed based upon the F'mal AsseumeDt Document and the assumption that no dispute
resolution will occur. If events that necessitate a schedule change or extension occur, the change will be
incorporated in accordance with the Federal Facility Agreement.
.
.,
...,
9-1
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10.0
CONSISTENCY WI11I THE FINAL REMEDIAL ACI10N
The FederafFacility Agreement states that all Interim ResponSe Actions (IRAs) shall 8to the maximum extent
practicable, be consistent with and contnDute to the efficient performance of Fmal Response Actions8 (paragraph
22.5).
The alternative assessment aiteria (yVCC 1989) were used to evaluate the interim response action alternatives.
The selected alternative, by providing significant control of a source of contamination for the period during which
fmal response actions are being developed, will be consistent with any Fmal Response Action.
10-1
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Woodward-Clyde Consultants
11.0
REFERENCES
Ebasco Services, Ine. 1989. June. Proposed Fmal Remedial Investigation Report, Volume XI, North Central
Study'Area, Version 3.2. RIC 89166R07. .
. ~
Environmental Science and Engineering, Ine. 1987a. June. Fmal Phase I Contamination Assesc:ment Report, Site
36-4, Lime Settling Basins, Version 3.3, Task No.1. RIC 87203R02.
Environmental Sciences and Engineering, Ine. 1987b. September. Fmal Phase n Data Addendum, Site 36-4,
Lime Settling Basins, Version 3.1. RIC 87203R02A
- Woodward-Clyde Consultants. 1989a. Fmal Alternatives Assessment of Interim Response Actions for Other
Contamination Sources - Lime Settling Basins.
Woodward-Clyde Consultants. 1989b. Results of Field and Laboratory Investigations Conducted for the
Remediation of Other Contamination Sources Interim Response Action, Version 2.0.
. ..
0\,;.1
,
4.J
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'..
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11-1
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APPENDIX A
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. ,
Ref:
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
AE GION vm
999 18th STREET - SLRTE 500
DENVER, COLORADO 80202-2405
DEC ;Z 7 .jC~:]
.......
I~
).. c; £Ju. ~ '1
I: ~o
~
o
8HWM-SR
Mr. Donald L. Campbell
Office of the Program Manager
Rocky Mountain Arsenal
ATTN: AMXRM-PM
Commerce City, Colorado 80022-2180
Re: Rocky Mountain Arsenal (RMA)
Proposed Decision Document for
the Interim Response Action at
the Lime Settling Basins,
November 1989.
Dear Mr. Campbell:
. .
We have reviewed the above referenced report and have the
enclosed comments. We particularly wish" to emphasize our
concerns in the following areas:
~_.J
1 .
the lack of adequate definition of the extent of
contamination upgradient, within, and downgradient of
the basins; "
2.
the lack of adequately assessing the benefits of a
groundwater extraction and treatment system;
3.
th~ lack of establishment of ARARs to enable the
effective monitoring of the efficiency of the IRA.
Extensive revisions to address our concerns may result in a need
to reissue the Proposed Decision Document or otherwise modify the
schedule for the Draft Final Decision Document. "
Comments on the revised Assessment Document are being sent
in a separate letter. Please contact Linda Jacobson at (303)
"294-7093, if you have questions on this matter.
Sincerely,
"~~ J~J
Connall! Hears
EPA Coordinator for
RMA Cleanup
Enclosure
-fill> ~... ~
Q,-,
{-I""" "
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cc:
Col. Dan Voss, RMA-PMO
J. D. Smith, RMA-PMO
Jeff Edson, CDH
David Shelton, CDH
Vicky Peters, CAGO
Lt. Col. Scott Isaacson
Chris Hahn, Shell
R. D. Lundahl, Shell
Robert Foster, DOJ
-~
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Comment 1:
Response:
'-'
.
LJ
Comment 2:
Response:
Comment 3:
RESPONSE TO COMMENTS ~OM THE EPA
ON THE PROPOSED DECISION DOCUMENT
FOR THE INTERIM RESPONSE ACTION
AT THE LIME SE'ITLING BASINS
NOVEMBER 1989
Page 1-1, please clarify whether the .relocation of sludge material.. . to the Lime Settling Basins"
is occurring within the area of contamination and if it constitutes a new placement for purposes
of the LDRs.
Based On the AC.~Ument of the Phase I and Phase n soil sampling programs and additional
observations from the IRA field investigation, it appears that some of the sludges from the central
area of the Lime Settling Basins were removed at some time and spread out adjacent to the
basins. In the North Central Study Area Repon (Ebasco 1989), the Lime Settling Basins area
is expanded to include areas to the north, south. and west of the basins because these areas have
materials that are characteristic of the Lime Settling Basins.
It is assumed, for the purpose of evaluation, that material previously placed adjacent to the Lime
Settling Basins would be replaced, to the extent practicable, in the area of the basins before
construction of the subsurface barrier and cover. This will reduce the area that must be
encompassed within the subsurface barrier and cover, and will reduce the amount of fill materiai
required to regrade the site. Replacement of this material does not constitute a new placement
for purposes of the land disposal restrictions.
Neither the Alternative Assessment nor the Decision Document discuss the lateral extent of
contamination. Further, both documents fail to discuss the contaminant migration rate and the
extent and magnitude of the existing plume emanating from the Lime Settling Basins. The Army
should develop and document further information On the existing extent of the contamination and
the migration rate from existing releases. The provision of this information will assist in the
determination of the adequacy of the proposed remedial action, its scope and design, and/or the
need for another IRA to address past releases. Section 2.0 should be expanded or another section
should be added to summarize the magnitude of contamination upgradient, within, and
downgradient of the basins.
Details of the nature and extent of contamination in the Lime Settling Basins area can be found
in the final IRA alternatives assessment for this site (WCC 1989a) and the Phase I and Phase
n Contamination Assessment Reports (ESE 1987a and 1987b). The objective of this IRA is to
mitigate the threat of releases from the Lime Settling Basins On an interim basis. The subsurface
barrier and cover with groundwater extraction and treatment alternative is based On proven
tec:hnology that is adequate to meet this objective. Aquifer remediation will be addressed in the
final Record of Decision (ROD).
Pages 4-2 and 4-3, does this alternative require periodic dewatering of the contained sludges?
As stated in Section 4-5, .Sufficient groundwater. . . extracted periodically from within the slurry
wall . . . (would) maintain a reverse hydraulic gradient across the wall. This would help limit the
(2m.C».39) (aJl)Af'JO) (EPA.1Dl)
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Response:
Comment 4:
continued migration of contaminated alluvial groundwater across the wall that might accumulate
as a result of inf1ltratioD..
The construction of a slurry wall should mitigate groundwater transport from the Lime Settling
Basins. However, we believe that an effective utilization of a slurry trench should include
groundwater extraction from the contained alluvium. Groundwater extraction would accomplish
the following: a) assure an inward hydraulic gradient across the slurry trench barrier towards
. the basins, thus better assuring horizontal containment, b) reduce the hydraulic head on the
Denver formation, thus reducing the chances of vertical permeation of contaminants into the
Denver formation, and c) contribute to reduction of contaminants within the basins utilizing
existing treatment facilities.
The wastes generated from such periodic groundwater extraction and treatment would eventually
be generated during onpost groundwater remediation anyway. Their treatment should not
represent an exceptional added cost to the IRA, but does represent an opportunity to further
pursue the IRA objectives.
Further, establishment of a slurry wall within this area would impact groundwater flow patterns,
potentially redirecting contaminated groundwater into less contaminated areas. Assessment of
that potential problem should be done before the Decision Document is finalized.
In response to cOmments from the Organizations and the State, the Army has reconsidered the.
preferred IRA Alternative for the Lime Settling Basins. The subsurface barrier with the soil and
vegetative cover alternative will include periodic dewatering of the contained sludges, as necessary,
to maintain an inward hydraulic gradient across the barrier. The cover will help minimize
inf1ltration into the contained area, thereby further reducing the potential for an outWard
hydraulic gradient across the barrier.
The hydraulic head within the subsurface barrier will be reduced only to the extent necessary to
maintain an inward gradient. Reducing the hydraulic head on the Denver Formation to this
extent, over only a 5-acre site, would have an inconsequential effect on vertical permeation of
contaminants into the Denver Formation in the area.
The extracted groundwater will be treated at the CERClA Liquid Waste treatment facility if that
facility is in operation, otherwise, it will be treated at a separate treatment facility implemented
and operated for this IRA.
Since the aquifer in Section 36 is contaminated from the South Plants Area, it is not anticipated
that impacts on groundwater flow patterns from establishment of a subsurface barrier around the
Lime Settling Basins area would likely redirect contaminated groundwater into less contaminated
areas.
Page 4-4, monitoring should be done to ensure the efficiency of the containment system in
.mitigating further releases.. Without levels of existing contamination being established, please
state what will serve as the baseline to denote further releases. Please state whether sufficient
~') (fIJf)A/'lO) (EPA.UM)
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Response:
Comment 5:
-l
Response:
Comment 6:
Response:
Comment 7:
(
monitoring wells exist in close proximity to the Lime Settling Basins to allow early detection of
significant releases.
Please incorporate an operational monitoring program into the Decision Document. The
program should be designed to monitor the effectiveness of the selected remedy in mitigating
contaminant transport in both the surficial alluvium and the Denver formation.
The operational monitoring program will be developed during the design of this IRA. The
Decessity for additional monitoring wells to allow early detection of significant releases will be
determined at that time. The baseline used to denote further releases will also be determined
during design. However, this IRA is Dot intended to specifically address the Denver Formation.
As stated in the response to EP A's comment No.3, the groundwater extraction system will do
little to prevent vertical permeation of the groundwater into the Denver Formation within the
subsurface barrier.
As an exercise to illuminate the issue, we made calculations that show that even if a porosity ~
high as 50% is assumed for the alluvium beneath the basins, the total recharge from rainfall in
the absence of a cap would only be about 2,000,000 gallons per year less evaporation or a head
increase within the alluvium of about 2 to 3 feet. In the absence of a cap, the inflltration of
precipitation would continue to transport contaminants to the alluvium, anod thus periodically to
a treatment system through new extraction wells. Periodic extraction of less than 200,000 gallons
per month would maintain the inward gradient towards the basins, unless the slurry trench leaks
excessively.
The benefits of eliminating the cap, and extracting and treating 200,000 gallons per month of
infiltration, plus leakage through the slurry trench, while assuring an inward gradient, should be
evaluated before the final decision is proposed.
A groundwater extraction and treatment system has been reevaluated for this site in response to
comments from the Organizations and the State. The preferred alternative in the rlDal Decision
Document for this site is to construct a subsurface barrier with a soil and vegetative cover.
Groundwater will be extracted, as necessary, to maintain an inward hydraulic gradient across the
barrier. The extracted water will be treated either at the CERCLA Wastewater Treatment
System or at a separate facility implemented and operated for this IRA.
The Decision Document needs to more fully evaluate for each alternative the IRA's consistency
with and contribution to the efficient performance of the Fmal Response Action. More detail
addressing this important aspect of the IRA is needed than the single sentence at the end of
paragraph 4.8, Conclusion.
The alternative evaluation summary has been expanded to include discussion of consistency with
the final remedy for each alternative (SectiOD 4.0).
On page 3-1, Evaluation Criteria, the document states that seven aiteria were used; however,
on page 4-1, the text states that 8{a)lternatives that reduced contaminant mobility, toxicity, or
8.
(2XI2-4»o3P) (fD/JA/9O) (EP.uJM)
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Response:
Comment 8:
4.-1
.
.
--
Response:
Comment 9:
Response:
~
volume (MTV) are preferred. One of the evaluation aiteria that showed the greatest variability
betwccn alternatives was the ability of an alternative to reduce contaminant mobility, toxicity, or
volume: The slurry wall with cap, slurry wall with groundwater extraction and treatment, and
the excavation and onsite temporary storage alternatives, if properly implemented, offer essentially
the same mobility reduction benefits. Only the slurry wall with groundwater extraction and
treatment alternative has a potential to reduce toxicity and volume (through treatment and
destruction of contaminants). The other Six alternatives do not reduce toxicity or volume and
are identical in this respect. This further supports our earlier contention (see Comment 3) that
the slurry wall with groundwater extraction and treatment should be reevaluated.
In response to comments from the Organizations and the State, the preferred alternative in this
Fmal Decision Document is construction of a subsurface barrier and vegetative cover at the Lime
Settling Basins, with groundwater extraction, as necessary, to maintain an inward hydraulic
gradient across the barrier. The Army agrees that contaminant toxicity and volume may be
reduced if it is necessary to extract and treat groundwater to maintain the inward hydraulic
gradient.
On page 4-3, Slurry Wall with Groundwater Extraction and Treatment, the Decision Document
states that "(t)he treatment process would generate a waste sludge for subsequent treatment and
disposal. Therefore the total volume of waste material to be treated would increase: A waste
treatment system would destroy organic materials and concentrate the heavy metals, thus
decreasing the overall volume of both contaminants and contaminated material. Through
extraction and treatment there would also be fewer contaminants in contact with groundwater.
Total contaminated material in the ground would decrease, and total mass would decrease
because contaminants are being removed and bandIed properly. We do not agree wi.th your
statements to the contrary.
This is the only alternative presented that includes treatment as a means of addressing the
problem.. No discussion is presented on the SARA preference for treatment as the principal
remedy. The remedy proposed needs careful reanalysis.
This statement has been deleted from the text. The preferred alternative in this Fmal Decision
Document is a subsurface barrier with soil aDd vegetative cover, with groundwater extraction, as
necessary, to maintain an inward hydraulic gradient aaoss the barrier. It should be Doted,
however, that this interim action is not intended or designed to be the final remedy as the EP A
eludes to with reference to SARA preference. This interim action Collows the guidelines
established in the Federal Facility Agrccment.
In reference to page 8-2, the Endangered Species Act is a location-specific ARAR, per EP A
guidance (CERQ.A Compliance with Other Laws Manual).
The Endangered Species Act is listed as a location-specific ARAR in the Fmal Decision
Document.
(:IJCIa.GO.39) (tD/~/90) (EJ'A.IJM)
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Comment 10:
Response:
On page 8-4, the text states that Colorado construction air quality regulations "are not applicable
because they specifically do not address a remedial action or circumstance under CERCLA:
Construction regulations regardless of location or statute under which they are performed should
be considered relevant and appropriate. Please reassess the validity of this statement.
These regulations are identified as applicable iD the rmal Decision Document.
Comment 11: Wetlands are a location specific ARAR, not an action specific ARAR (see page 8-7).
Response:
Comment U:
Response: .
.....:
Comment 13:
Response:
Wetlands considerations are identified as a location-specific ARAR in the Draft rmal Decision
Document. They are also discussed as an action-specific ARAR because wetlands considerations
could affect actions taken during construction.
The document on page 8-7, Land Disposal Restrictions and Removal of Soil, states that "There
are no action-specific ARARs that pertain to the excavation and relocation of soil to the Lime
Settling Basins during construction of this treatment system: Containment without groundwater
extraction and discharge is not "treatment". The IRA involves handling and disposal of RCRA
regulated substances, hence, RCRA is applicable.
The rmal Decision Document reflects that the Army will proceed consistent with EP A guidance
concerning the handling of soils during construction of the facilities related to this IRA. The cited
language has been modified in response to this comment.
On page 8-1, Ambient or Chemical-Specific ARARS, the document states that "No ambient or
chemical-specific ARARs were identified concerning level of contaminants for soils that are
placed in such containment structures: MCLs for groundwater protection exist and should be
selected as ARARs, if a pump and treat System is incorporated into this IRA. Further, the IRA
will produce construction debris, decontamination liquids, and other fluids containing RCRA
regulated wastes. RCRA is applicable for their handling and disposal.
Any liquids generated through dewatering are intended to be treated at the CERCLA Wastewater
Treatment System and chemical-specific ARARs for liquid treatment will be reflected in the
decision document concerning that IRA. The Draft rmal Decision Document discusses the
management o( materials generated during IRA construction.
Comment 14: We reserve the right to further select the ARARs for this IRA, after response to our comments
and as the decision, design, and implementation proceed.
Response:
The Draft rmal Decision Document identifies ARARs (or this IRA. Some ARARs are identified
in general terms where the future design determinations will affect the identification of specific
requirements which will apply. The Implementation Document will reflect greater detail
concerning the specific design of this IRA. The Implementation Document is provided to EP A,
the other Organizations and the State for review and comment. Further defmition of specific
ARARs should occur in the context of this document.
~:J9) (rrJ/)A/fJO) (EPA.1JM)
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'.
. .
Shell Oil Company
December 19, 1989
Office of the Program Manager for Rocky Mountain Arsenal
ATTN: AMXRM-PM: Mr. Donald l. Campbell
Rocky Mountain Arsenal, Building 111
Commerce City, Colorado 80022-2180
Dear Mr. Campbell:
@
~
). / $-Q 29
(0'. ~~
~
\j
One Shell Plaza
po. 80x 4320
Houston. Texas 77210
Enclosed herewith are Shell Oil's comments on the Proposed Decision
Document for the Interim Response Action at the lime Settling Basins,
November, 1989, Version 2.0. Shell's comments on ARAR's are being
sent under separate cover.
L...
ee~#I
R. ~~~
Manager Technical
Denver Site Project
/ajg
Enclosure
cc:
(w/enc10sure)
Office of the Program Manager for Rocky Mountain
ATTN: AMXRM-PM: Col. Daniel R. Voss
Bldg. E-4460
Aberdeen Proving Ground, MD 21010-5401
Office of the Program Manager for Rocky Mountain Arsenal
ATTN: AMXRM-RP: Mr. ~evin T. Blose
Rocky Mountain Arsenal, Building 111
Commerce City, CO 80022-2180
Arsenal
Office of the Program Manager for Rocky
ATTN: AMXRr.-IA: Mr. Bruce M. Huenefe1d
Rocky Mountain Arsenal, Building 111
Commerce City, CO 80022-2180
Mountain Arsenal
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cc: Mr. Bradley S. Bridgewater
Department of Justice
c/o Acumenics Research & Technology
999 18th Street
. Suite 501, North Tower
Denver, CO 80202
Department of the Army
Environmental Litigation Branch
Pentagon Room IC480 .
ATTN: DAJA-ELL: Major Lawrence E.
Washington, DC 20310-2210
Rouse
Victoria L. Peters, Esq.
Assistant Attorney General
CERCLA Litigation Section
1560 Broadway, Suite 250
Denver, CO 80202
Mr. Robert L. Duprey
Director, Hazardous Waste Management Division
U.S. Environmental Protection Agency, Region VrrI
One Denver Place
999 18th Street, Suite 500
Denver, CO 80202-2405
Mr. Connally Mears, 8HWM-SR
EPA Coordinator for Rocky Mountain Arsenal
US EPA, Region vrrr, Superfund
999 18th Street, Denver Place, Suite'SOO
Denver, CO 80202-2405
Mr. Thomas P. Looby
Assistant Director
Colorado Department of Health
4210 East 11th Avenue
Denver, CO 80220
Mr. Jeff Edson
Hazardous Materials and Waste Management Division
Colorado Department of Health
4210 East 11th Avenue
Denver, CO 80220
nnllunn..,~..,I'\'"
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RESPONSE TO COMMENTs PROM SHFJ J On. COMPANY
ON PROPOSED DECISION DOCIJMFNT
FOR TIm OOERIM RESPONSES ACTION
AT THE UME SE'ITUNG BASINS
VERSION 2.0
NOVEMBER 1989
GENERAL COMMENT
Comment 1:
In Shell's opinion, data presented in the recently issued reportl describing 1989 laboratory
and field investigations of the Lime Settling Basins fail to validate the undocumented
conclusion used by the Army in preparing the Alternative Assessment that this site is an
active source of arsenic contamination I. Although elevated concentrations of arsenic were
detected in weUs immediately downgradient of both the M-1 and Lime Settling Basins,
arsenic concentrations decline very rapidly short distances downgradient of these weUs.
Since these basins have existed since 1942, the data suggest that arsenic in the form present
in the basins is relatively immobile. Studies2 in the literature on arsenic mobility support
that certain inorganic species of arsenic are essentially immobile in soil.
I.~
Even if the Lime Settling Basins are considered an active source, beause of the very slow
movement of arsenic it seems unlikely that a long term technical or cost benefit would be
gained by conducting an interim response action at this site. Shell urges the Army to
reconsider whether any action other than Monitoring/Maintenance would be appropriate,
i.e., is the site an active source and, if so, speci.ficaJ1y what benefit( s) would be expected from
an interim response action? Pursuant to the Decision F10w Chart (FJgUre 1-1),
Monitoring/Maintenance is the appropriate action if either the site is not an active primary
source, data are inadequate to determine whether it is an active source, or there is no clear
identifiable benefit from conducting an interim response action.
Response:
Based on available data, the Lime Settling Basins appear to be an active source of arsenic
contamination to the groundwater. The Army agrees that the arsenic appears to attenuate
rapidly. However, the Army believes there is a benefit in containing this source by
implementing a subsurface barrier and cap at the Lime Settling Basins, with groundwater
extraction, as necessary, to maintain an inward hydraulic gradient aaoss the barrier. The
groundwater intersects the sludge in the Lime Settling Basins during part of the year. The
subsurface barrier will inhibit the lateral migration of contaminants with the groundwater
1 WResults of Field and Laboratory Investigations Conducted for the Remediation of Other Contamination
Sources Interim Response Action November, 1989, Version 2.0. This report, which was issued concurrently
(November '1:1, 1989) with the Proposed Decision Document, presents studies on which the Army concluded
in the Alternative Assessment document that this site is an active source.
2 See Shell's comments, dated December 19, 1989 to D.L Campbell, on the report listed in footnote No.1.
(20Q204J0.J9) C&be!l.allll) C=/rT /'10)
-------
that appears to be taking place. Also, a minimal cap and site grading may be appropriate
. because of the low infiltration rate in this area. This alternative would not be inconsistent
with any final remedy.
SPECIFIC COMMENTS
Comment 1:
Response:
Comment 2:
Response:
JJ
Comment 3:
~
Response:
P~e 2- L first paragraph.
Put between 1947 and 1982 at the end of the last sentence. This time period relates to
manufac:twiDg, not lease.
The text has been changed.
Palle 2-1. second paragraph.
Would aaueous rather than ~ better describe Army wastes discharged to unlined
evaporation ponds?
The text has ~n changed. to describe the wastes as "wastewater:
Pa~e 2-4. last paragraph.
Shell Oil Company is a signatory of the Federal Facility Agreement.
"The Federal Facility Agreement specifies 13 Interim Response Actions (IRA's)'
determined to be necessary and appropriate..
However, for the Remediation of Other- Contamination Sources IRA, the Federal Facility
Agreement states that "This action consists of assessment and, as necessary. the selection
and implementation of an IRA for the . . . Section 36 Lime Pits . . : (Article 22.1(1);
emphasis added).
The Army interprets the FFA's definition of an IRA to be the process which consists of
as.seccment and, as nec:cssary, the implementation of an interim action. Therefore,
~ccment of the 131RAs is nec:cssary, but implementation of an interim action mayor may
not be nec:cssary, as determined by the as~ccment for this site.
The Army conducted the IRA Alternatives Asseccment of the Lime Settling Basins and has
determined that the interim action alternatives chosen for implementation is nec:cssary and
appropriate.
(~39) (~) (02/rt/90)
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Commcnt 4:
Rcsponse:
Commcnt 5:
Rcsponse:
Commcnt 6:
.J
Response:
Commcnt 7:
Pa~c 4-1. 4.0 Intcrim Rcsponsc Action Altcrnativcs.
Although long-tcrm cffectiveness is less important for an intcrim response action than for
a final response action, this aiterion seems to receivc major emphasis in thcsc summaries,
whcreas short-term effectiveness (c.g., impact On workcrs and thc community) is hardly
mcntioned.
Thc text has been changed to provide a more balanced summary of thc detailed evaluation
prcscnted in thc IRA Alternatives .A~cc"'ent for the Lime Settling Basins (WCC 1989).
P~e 4-2. 4.4 Slum Wall with a.p and 4.6 Multilavcred Cap.
The multilayered cap described for inhibiting surface infiltration is far more complex than
is necessary for short-term use. A contoured, low-permeability layer of clay plus a vegetative
.cover would substantially reduce infiltration.
The cap design presented is for purposes of evaluation. The final cap design will be
determined during the design of this IRA. The Army agrees that, given the low rate of
infUtration in this area, a cap similar to the one described in this comment may be more
appropriate. This detcrmination would be made during design.
Paic 4-4. 4.8 Conclusions.
As discussed undcr GcncralComments, on the basis of rcsults of thc 1989 field and
laboratory invcstigations, the Army should reconsidcr the Monitoring/Maintcnance
alternative.
See response to SheD's General Commcnt.
Palle 5- L 5.0 Chronoloov of Events.
Refercnce to the report issued on 1989 field and laboratory invcstigations should be included
in tbis chronology.
The entry for February 1988 should be deleted, because it is outside the process prescribed
by the FFA. See paragraph 22.7 of the FFA. If the entry is to be retained, a date should
be provided for the request, so that the Organizations may verify that such a request was
in fact made. The March 7, 1988 letter from David 1. Anderson to Edward J. McGrath
includes a summary of the status of various requests for ARAR identifications, but does not
mention any request in connection with this IRA.
C~39) CWII.cDm) (=/77/90)
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Response:
Comment 8:
Response:
Comment 9:
Response:
...
The text has been changed to include reference to the field and laboratory report. The
February 1988 entry has been deleted.
P3ie 7.1.
Paragraphs 2. and 3. should be eliminated, because they do not apply to the Lime Settling
Basins portion of the "Hot Spots8 IRA.
These paragraphs have been deleted.
Pa~e 7.1. paragraph 4.
To conform to paragraph n7 of the FFA, replace -ne Army, Shell, and State are given
the opportunity to identify, on a preliminary basis,8 with -ne Organizations and DOl shall
have the opportunity to participate, at the RMA Committee level, in the identification and
selection of:
The text has been changed.
(~:J9) (1ile1LallD) (02/71/90)
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Comment 1:
Response:
. ..
. ,
.-...
RESPONSES TO COMMENTS PROM SHEil.. OIL COMPANY
ON THE APPUCABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS FOR THE REMEDIATION OF OTHER
CONTAMINATION SOUR~ - UME SE'ITUNG BASINS
INTERIM RESPONSE ACI'ION
Shell incorporates the same comments regarding the land disposal restrictions and RCRA
provisions as it had for the M-1 Settling Basins.
As Shell is aware, guidance in this area is under development. The Army will act
consistently with EP A guidance concerning this issue.
(2Da2.4»39) (.belLcDm) (02/71/90)
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STATE OF COLORADCY
COLORADO DEPARTMENT OF HEALTH
4210 East 11t1'1 Avenue
Denver. Colorado 80220
Pnone (303) 320-8333
December 27, 1989
Roy Romer
Covernor
. Mr. Donald Campbell
Deputy Program Manager
Rocky Mountain Arsenal
AMXRM-PM, Bldg. 111
Commerce City, Colorado
Thomu M. Vernon. M.D.
hecutrve DireCtor
80022-2180
Re:
state Comments on Proposed Decision Documents for Other Con-
tamination Sources - M-1 Settling Basins and Li~e Settling
Basins
Dear Mr. Campbell:
..01
Enclosed are the State's comments on the above-referenced
documents. In-situ vitrification (ISV) appears to be a. good'
choice for the remediation of the M-1 Settling Basins. It should
effectively reduce the toxicity, mobility, and volume of the con-
taminants and treat the organics and inorganics simultaneously.
According to the M-1 Settling Basins Alternative Assessment docu-
ment, the treatment can be implemented quickly to minimize fur-
ther contamination of the groundwater.
The Lime Settling Basins may also be suitable for ISV. . Al-
though the Army has chosen to cap and build a slurry wall around
the Lime Settling Basins as the Interim Response Action (IRA),
this will not preclude the use of ISV (or other treatment
methods) as the final treatment for these basins. Because ISV is
a relatively unproven technology we approve of the Army's
cautious approach in using the process at a small site (the M-l
Settling Basins), with the possibility of scaling up to the
larger Lime Settling Basins, if shown to be successful.
A major concern not addressed in these Proposed Decision
Documents is the arsenic and mercury contamination in the
groundwater in the area of the M-l and Lime Settling Basins. As
the State has commented previously, the Army should explore
treatment of inorganics in the groundwater prior to the final
remedy, at the sources or at the Basin A neck groundw~ter
intercept/treatment system.
Some of the comments being provided at this time are more
relevant to the design and implementation stage of the IRAs. The
State feels that by submitting these comments at this time, the
Army may be better able to utilize them.
!1/Y11l
"10- 000 ~
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Mr. Campbell
Rocky Mountain Arsenal
December 27, 1989
Page 2
If you have questions or wish to discuss these
please feel free to call me.
issues,
eff Edson
RMA Project Manager
Hazardous Materials and
Waste Management Division
JTE: jmb
C:\WS2000\RMA\CAMPBEL3.LTR
Enclosures
cc:
Michael Hope, Esq.
John Moscato, Esq.
Chris Hahn, Shell
Edward J. McGrath, Esq.
Connally Mears, EPA
Bruce Ray, EPA
Major Lawrence E. Rouse
Tony Truschel, GeoTrans
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'"
RESPONSE. TO COMMENTs PROM 1HE STATE OF COLORADO
. ON THE PROPOSED DECISION DOCUMF:NT
FOR 0TIiER CONTAMINATION SOURCES IRA
LIME SE'ITLING BASINS
GENERAL COMMENTS
Comment 1:
Response:
..
Comment 2:
Response:
Comment 3:
In the FmaJ Alternative .As~c.c.ment of Interim Response Actions for Other ContaminAtion
Sources, Lime Settling Basins (Alternative .A~ument document), the Army states that
Alternative 2, Monitoring. will also be incorporated in any of the remaining Alternatives 3
through 7 selected for the IRA (page 4-2). Therefore, the proposed Alternative (#4)
prcscnted in the Decision Document should include alluvial aquifer and ambient air
monitoring. Nowhere in the Proposed Decision Document is this stated, We assume that
this is an oversight by the Army, and that the Monitoring Program prcscnted in Section 4.1.2
of the Assessment Document will be included as part of the Lime Settling Basins IRA.
Monitoring should consist of quarterly sampling of groundwater from upgradient alluvial wells
36001, 36054, 36058 and 36193, and downgradient wells 36076, 36167, and 36194 and analysis
for the following target compounds: 1) volatile halogenated organics; 2) volatile aromatic
organics; 3) semi-volatile halogenated organics; 4) total and dissolved arseniC; 5) total and
dissolved mercury; 6) ICP metals; and 7) pH. The air monitoring program should consist
of quarterly sampling from four air monitoring stations to be set up around the perimeter
. of the slurry wall. Air samples should be analyzed for TSP, metals, pesticides, and semi-
volatile organic compounds.
Groundwater monitoring will be included as part of the preferred alternative. The text has
been changed to clarify this. The groundwater monitoring program prcscnted in the IRA
Alternatives Assessment is a suggested program used for evaluation purposes. Details of the
groundwater monitoring program would be determined during the design of this IRA, and
the State's recommendations will be taken into consideration at that time.
Additional air monitoring may be implemented during COnstruction operations, if determined
to be necessary during design. However, the Army does not anticipate that air monitoring
specifically for the Lime Settling Basins area will be necessary following completion of
implementation of this interim action, other than the air monitoring conducted under the
CMP for the entire Arsenal.
The State requests further assurances by the Army that the multi-layered cap will not become
the final remedy (without treatment of the sludge and contaminated soils).
The preferred IRA alternative for this site is COnstruction of a subsurface barrier with cover,
and groundwater extraction and treatment, as necessary, to maintain an inward gradient. This
alternative is not intended to be the 6nal remedy. Further remedial actions will be evaluated
in determining the 6nal remedial action in the Onpost Record of Decision (ROD).
Locations of the three Lime Settling Basins and the proposed slurry wall should be clearly
shown with respect to the central section of Site 36-4 presented in F1gW'e 2-1 of the
(2DQ24).]9) (02/rI/9(J) (STA11!.UW)
-------
s
Response:
Comment 4:
. .....
~ .
Response:
Comment 5:
Response:
Alternative ~s~""~ent Document. The Army has stated that the slurry wall will be
constructed around the three basins and associated berms. Docs this correspond to the
perimeter of the central section or do the basins and resultant slurry wall only cover a subarea
o( this section?
For the purpose of the IRA Alternative ~S5e'''.''''ent, it was assumed that the subsurface
barrier would be located approximately 20 feet outside the Lime Settling Basins boundary.
The exact location of the barrier will be determined during design. Some of the cont:aminated
material adjacent to the Lime Settling Basins, which appears to be sludge from the basins
removed {or drying, will also be placed within the subsurface barrier before construction o(
the soil and vegetative cover.
It appears that an area to the DOrth of the Lime Settling Basins (phase U expanded Site 36-
4) was used (or land application and drying of lime sludge (Decision Document, page 2.1).
The Army states on page 2.'Z7 of the Alternative ~""~ent Document that the top 2.5 feet
of this sludge/soil will be removed and placed in the central section (or subsequent capping.
However, review o(FlgUJ'e 36-4-0.1 in the Site 36-4 Phase 0 Contaminant Asse....ment Report
(CAR) indicates that two o( the six Phase 0 borings, and one of the three Phase I borings
in the northern section have high organochJorme pesticide (OCP), arsenic, and mercury
concentrations in the 4 to 5 (oot interval. This indicates that sludge or sludge soils are present
to a depth of five feet, and that excavation of only 2.5 feet of sludge could ac:tuallyexpose soils
with higher OCP, arsenic, and mercury concentrations than present in the current topsoil.
How docs the Army plan to address the 2.5 to 5 foot cont:aminJ\ot interval in the northern
section? The State strongly recommends excavation to a depth oC five Ceet in this area.
The depth of 2.5 Ceet was used (or evaluation purposes. The exact depth (or excavation will
be determined during design, and the State's recommendation will be taken into
consideration. The depth oC removal will be based on the presence o( sludge materials, and
the results of field investigations.
The Army also intends to remove the top 1 foot oC soils from the western and southern
sections of Site 36-4 (Alternative ~ument Document, page 2.27). However, the Army has
not indicated that these areas were used Cor land application oC lime sludge. Review oC
figures 36-4-0.1 (Site 36-4 Phase 0 CAR) supports the observation that sludge was Dot
applied to these areas, and indicates that the low levels of OCPs present in the 0 to 1 Coot
interval (maximum concentration oC 1 ug/g dieldrin in Boring 3163 of the western section)
are possibly due to wind transport of contamin:ants. Comparison of the low OCP levels in
the western and southern sections with the much higher concentrations prcscnt in the
northern section raises the question of why the Army finds it necessary to excavate topsoils
in the former two scctiODS, while not addressing obvious lime sludges present to 5 foot depths
in the northern section.
See response to the State's General Comment No.4.
(3IQ2~J9) C=/rI/90) CSTA'IEJJM)
-------
Comment 6:
Response:
. ,
~
The Army should coDed sufficient samples of the soils and sludges from the Lime Settling
Basins prior to capping, so that lab treatability studies can be performed to allow the selection
of the best final remedy.
Agreed. This will be considered during design and implementation of this IRA.
(~J9) (02/rI/9fJ) ($TA11!J.DoC)
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. .
f.
RESPONSE TO COMMENTs FROM THE STATE OF COLORADO
ON DRAFT APPUCABLE OR RFJ PVANT AND APPRopRiAm-;;;;~
FOR THE UME SE1TUNG BASINS
INTERIM R.E..C;PONSE ACI10N
GENERAL roMMENTS
Comment 1:
Response:
Comment 2:
,.J
Response:
The Proposed Decision Document states that lime sludge adjacent to the basins wil1 be moved
ODto the basins prior to construction of the slurry wall. However, the ARARs contain no
standards regarding the excavation and transportation of the hazardous materials. The
composition of these materials should be described in the decision document and applicable
air emissions and hazardous waste management regulations dec;g1':ated as ARARs.
The proposed Decision Document onJy mentions that the lime sludge adjacent to the basins
wil1 be moved onto the basins. The Health and Safety Plan covers detection and appropriate
actions to be taken in case of emissions.
To the extent that this document repeats text contained in previous Army draft ARARs
documents without acknowledging prior comments offered by the Parties. the State refers the
Army to previous State ARARs comments On those documents.
Please see the Armys previous response to the State's comments.
,-4
SPECIFIC COMMENTs
Comment 1:
Response:
P. 8-3, para. 1: The Army Mites that it has reviewed all potentia] ambient or chemical-
specific air emissions and found no federal or state ambient air quality standards applicable.
However, the lime settling basins soils and groundwater contain VOCs as well as lead and
mercury. The Army should therefore list ARARs for the possible emissions from the
construction of the slurry wall including Colorado regulations 7 and 8, in addition to standards
for removal of lime sludge into the lime basins. .
In the context of this IRA, there is onJy a limited chance of any release of volatiles or
semivolatiles. and C\'Cn if such a release did occur, it would onJy be interminent 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
sprri:al;st). The Army has significant experience with the construction of extraction and
reinjection wells, and with the COnstruction of subsurface barriers. such as is included in this
IRA, and has not experienced any problems from air emissions during construction of such
facilities. The site specific Health and Safety Plan wil1 adequately address these COncerns.
This plan. to be developed for use in the IRA, wil1 detail operational modifications to be
implemented in the C\'Cnt that monitoring detects specific levels of such emissions. The Army
has not identified any promulgated standards which address possible emissions from this type
of COnstruction actMty.
(:IIQ2.GI.:JP) (02/r'I/'1O) (STA 11UJW)
-------
Comment 2:
Response:
Comment 3:
Response:
.-'
~ :
u!
Comment 4:
Response:
Comment 5:
Response:
.
~
P. 8-3, para. 2: The Army states that construction for lime settling basins IRA does not
involve significant excavation with therefore little potential for air emissions during
construction. However, the proposed d~on document states that the system will include
the construction of a slurry wall, which requires excavation. Therefore, the construction
clearly has the potential for release of air emissions during Construction. The Army should
expand its ARARs analysis to include standards for air emissions from the construction of
the slurry wall.
The narrow excavation involved in the construction of a subsurface barrier is not likely to
.result in significant air emissions, since it does not involve exposing large amounts of soil.
No promulgated standards were identified which address possible emissions from this type
of construction activity.
P. 8-3, para. 3: The Army states that National. Emissions Standards for Hazardous Air
Pollutants (NESHAPS) were not considered relevant and appropriate in the context of this
IRA because the standards were developed for manufacturing processes which are
significantly dissimilar to the short-term . construction activities. The Army, however, should
consider NESHAPS relevant and appropriate if the contaminants subject to NESHAPS are
emitted in quantities contemplated by the regulation and at the minimum meet these.
standards.
NESHAPS are process specific and are not considered relevant and appropriate to apply to
any treatment system unless such system is similar to the specific process for which that
standard was developed.
P. 8-3, para. 4: The Army states that the provisions of 40 C.F.R. ~ 50.06 are considered
relevant and appropriate. However, the Army must also consider Colorado Regulation 1,.
which includes all total suspended particulates (TSP) and it (sic) therefore stricter than the .
federal standard. The Army has also misstated the federal standard. The correct federal
standard is that the particulate matter must not exceed 50 micrograms per cubic meter, not
75, as the Army states. The federal standard also lists particulate emission for a 24 hour
average at 1SO micrograms per cubic meter.
Fugitive particulate emissions requirements of Colorado Regulation 1 were considered. The
Army recognizes this requirement and will use aU available and practical 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.
P. 8-8, para. 2: The Army lists a number of RCRA provisions it considers applicable to the
management of hazardous wastes. Under CHWMA, a number of other regulations are
relevant such as 6 CCR 1007-3 pL 264.
The Final D~on Document includes reference to State regulations.
(DI2.C»39) (tlJl)Af90) (STA'IUJM)
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