United States Office of
Envirbnmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R09-92/082
August 1992
Superfund
Record of Decision:
Hassayampa Landfill, AZ
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NOTICE
The appendices listed in the index that 818 not found in this dOcument have been removed at the request of
the issuing agency. They contain material which supplement. but adds no fur1her ~ iriformation to
the content of the document. AU supptementai material is, howIIer. contain8d in the adm8Ii8IrarMt record
for this site.
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REPORT DOCUMENTATION 11. REPORTNo. I ~ 3. Recipient's Acce88ion No.
PAGE . EPA/ROD/R09-92/082
4. TItle and Subtitle 5. Report Da'"
SUPERFUND RECORD OF DECISION 08/06/92
Hassayampa Landfill, AZ
First Remedial Action- Final 6.
7. Author(s) 8. Perlorming Orgsniz.tion RepL No'
.. FIIrfonnlng Orgalnlzatlon Name and Addre.. 10. ProjecVT..klWork Unh No.
11. Contract(C) or Grant(G) No.
(e)
(G)
1~ Sponsoring Organization Nal1'II and Add.... 13. Type 01 Report & Period Coverad
U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
15. Supplementary Notea
PB93-964505
16. - (UmIt: 200 worda)
The Hassayampa Landfill site is a 10-acre area of a 47-acre municipal landfill that was
previously used for hazardous waste disposal. Land use in the area is predominantly
desert and is sparsely cultivated. The Hassayampa Landfill lies within the Hassayampa
River drainage area, but outside of the 100-year floodplain. The estimated
1,100 people who reside within a 3-mile radius of the site use the aquifer underlying
the site for their drinking water. From 1961 to the present, the Maricopa County
Landfill Department owned and operated the site. Waste disposed Of at the landfill
consisted chiefly of municipal garbaget tree trimmings, and other plant refuse. In
1979, the state requested that Hassayarnpa Landfill accept hazardous waste as an
alternate waste disposal site during a prohibition at City of Phoenix landfills. In
the 18 months that the landfill accepted hazardous waste, up to 3.28 million tons of
liquid waste and approximately 4,150 tons of solid waste were deposited. The Hazardous
Waste Area consisted of several unlined pits (pits 1-5) for disposal of heavy meta1st
(See Attached Page)
17. Docurnont Analyaia L Deacrlptora
Record of Decision - Hassayarnpa Landfill, AZ
First Remedial Action - Final
Contaminated Media: soil, debrist gw
Key Contaminants: VOCs, metals (chromium, lead)
b. IdantlllaralOpen.Ended Terms
c. COSAlI FiaIdiGlOup
10. Aveilabilhy Statement 19. Security Cloas (This Report) 21. No. 01 Poges
None 60
20. Security Cloas (Thla Page) 22. Price
None
ANSI-Z3$. 18 SfHJ In ru on. on Reverse 272 (4-77)
50272-101
(See
., ell
(Fonnelly N11S-35)
Deportment 01 Commerce
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EPA/ROD/R09-92/082
Hassayampa Landfill, AZ
First Remedial Action - Final
Abstract (Continued)
solvents, petroleum distillates, oil, pesticides, acids, bases, and non-hazardous septic
wastes. In 1981, under EPA guidance, a number of investigations were conducted that
revealed VOC contamination in the soil and ground water. This ROD addresses the soil,
debris, and ground water as the final action for the site~ The primary contaminants of
concern affecting the soil, debris, and ground water are VOCs and metals, including
chromium and lead.
The selected remedial action for this site includes treating contamination in the vadose
zone using vapor extraction at all locations where soil vapors exceed clean up levels;
controlling emissions from the treatment system using either vapor phase carbon
adsorption or catalytic oxidation as determined during the RD phase; installing a 10-acre
cap over the soil and waste in the Hazardous Waste Area; extracting and treating
contaminated ground water onsite using air stripping and, as necessary, vapor phase
carbon adsorption, and reinjecting the treated water onsite or in the immediate vicinity;
monitoring ground water; and implementing institutional controls including deed and
ground water use restrictions, and site access restrictions such as fencing. The
estimated present worth cost for this remedial action is $6,100,000, which includes an
annual O&M cost of $2,213,100 for 30 years.
PERFORMANCE STANDARDS OR GOALS:
The selected remedy will comply with the federal and more stringent state standards.
Soil vapor clean-up levels will be calculated based on levels that will be protective of
ground-water quality. The design of the cap will be in compliance with RCRA
requirements. Chemical-specific ground water clean-up goals are based on SDWA MCLs and
include l,l-DCE 7 ug/l; 1,2-DCA Sug/l; PCE 5 ug/l; TCE 5 ug/l; 1,2-DCE (trans) 100 ug/l;
1,2-DCE (cis) 70 ug/l; and l,l,l-TCA 200 ug/l.
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RECORD OF DECXSXOB
BASSAYAKPA LAHDFXLL
SUPERFmID SXTE
July 1992
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A.
B.
C.
TABLE OF COII'rBIITS
1.
DECLARATION. . . . . . . '. . . . . . . . . . . . . . . .
A. SITE NAME AND LOCATION. . . . . . . . . . . . . . .
B. STATEMENT OF BASIS AND PURPOSE . ~ . . . . . .
C. ASSESSMENT OF THE SITE. . . . . .
D. DESCRIPTION OF THE SELECTED REMEDY. . . . . . . . .
E. STATUTORY DETERMINATIONS. . . . . . . . . . . . . .
1
1
1
1
1
2
II.
DECISION SUMMARY. . . . . . . . . . . . . . . . . . . .
A. SITE NAME, LOCATION AND DESCRIPTION. . . . . . . .
B. SITE HISTORY AND ENFORCEMENT ACTIVITIES
C. HIGHLIGHTS OF COMMUNITY PARTICIPATION
D. SCOPE AND ROLE OF THIS DECISION DOCUMENT
WITHIN THE SITE STRATEGY. . . . .
E. SUMMARY OF SITE CHARACTERISTICS. . . . . . . . . .
F.. SUMMARY OF SITE RISKS. . . . . . . . . . . . . . .
G. DESCRIPTION OF ALTERNATIVES. . . . . . . . . . . .
H. SUMMARY OF THE COMPARATIVE
ANALYSIS OF ALTERNATIVES. . . . . . . .
THE SELECTED REMEDY. . . . . . . . . . . . . . . .
STATUTORY DETERMINATIONS. . . . . . . . . . . . . .
SIGNIFICANT CHANGES. . . . . . . . . .
3
3
6
14
. . . .
14
14
21
30
34
38
42
44
I.
J.
K.
LIST OF FIGURES
1-
2.
3.
4.
5.
6.
7.
Hassayampa Landfill Site Location Map. . . . 4
Hydrogeologic Cross-Section Landfill Vicinity 7
Water Level Contours for Unit A . . . . . . . 8
Potentiometric Contours for unit B . . . . . . . . . . . 9
Map of the Hazardous Waste Area and Sampling Locations. 11
Soil Vapor contamination Map. . . . . . . .'. . . . . . 18
Target Area for Groundwater Remediation. . . . . . . . . 20
LIST OF TABLES
1-
2.
3.
4.
Waste TypeSD1sposed at the Hassayampa Landfill site. . 12
Summary of Enforcement Activities. . . . . . . . . . . . 15
Summary of community Relations Activities. . . . . . . . 15
Comparison of Waste and Soil Contamina~t Concentrations
from Pit 1 to Health Based Guidance Levels. . . . . . . 17
Air COntaminant Concentrations. . . . . . . . . . . . . 22
Chemicals of Potential Concern' . . . . . . . . . . . . . 24
Risk Assessment Summary. . . . . . . . . . . . . . . . . 28
Comparison of Costs of the Remedial Alternatives . 31
Estimated Cost of the Selected Remedy. . . . . . . . . . 39
5.
6.
7.
B.
9.
LIST OF APPENDICES
Applicable or Relevant and Appropriate Requirements (ARARs)
Responsiveness Summary
Index of the Administrative Record
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Record of Decision
Hassayampa Landfill Superfund Site
Concurrence -- Assistant Reqional Administrator
-;; '} (/'~ (
I J...c.. I'.... r / l~,-
Nor~ McGee
Assistant Reqional
-;-. / j- - 7" '-
Date
Administrator
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Record of Decision
Hassayampa Landfill Superfund Site
Concurrence — Water Management Division
'Harry Serayadarian, Director Date
I) Water Management Division
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Record of Decision
Hassayampa Landfill superfund site
Concurrence -- Office of Regional Counsel
. { ,
{\,\ J \,JM~"- L/\.
Nancy J. . arvel ,
Regional. Counsel. ...
.J
_=J)'i ~ z..-,
Date
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"
Record of Decision
Hassayampa Landfill Superfund Site
Concurrence -- Waste Programs
La~puty
Waste Programs
Director
1 (If'/ f Z-
Da e
c,
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Record of Decision
Hassayampa Landfill Superfund site
Concurrence -- Hazardous Waste Management Division
r:e~ K2rbA /---L-
~/Jeff Zelikson, Director
1VVHazardous Waste Management
Z5 -tf-qL
Date
Division
..
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I.
DBCLARATIOIJ
A.
SITB DME AJID LOCATION
This Record of Decision (ROD) is written for the Hassayampa
Landfill Superfund site (the Hassayampa Landfill Site, the Site),
which is located in Maricopa County, Arizona, approximately 40
miles west of Phoenix, Arizona. For purposes of this ROD, the
site shall be defined as the 10-acre area of the 47-acre
municipal landfill where hazardous wastes are known to have been
disposed, as well as any areas where site-related contaminants
have come to be located.
B.
STATBHBII'l' OF BASIS AIJD PURPOSB
This decision document presents the selected remedial action for
contaminated soil and groundwater at the Hassayampa Landfill
Site, chosen in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA) as amended by
the Superfund Amendments and Reauthorization Act (SARA), and, to
the extent practicable, the National oil and Hazardous Substances
contingency Plan (NCP). This decision document is based on the
Administrative Record for the Site, the index of which is
attached as Appendix C.
c.
ASSBSSKBBT OF THE SITB
Actual or threatened releases of hazardous substances from this
site, if not addressed by implementing the response action
selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
D.
DBSCRIPTIO. OF THE SELBCTED REKBDY
The selected remedy for the Hassayampa Landfill site includes
remediation of groundwater and vadose zone (including soil and
soil vapor above the water table) contamination. The groundwater
component of the remedy includes extraction of contaminated
groundwater, treatment of the water using air stripping
technology (vapor phase carbon adsorption will be performed as
necessary to meet Federal, State, and County regulations
pertaining to air emissions), reinjection of the treated water,
and continued groundwater monitoring to measure the effectiveness
of the remedy. Federal Maximum contaminant Levels (MCLs) have
been chosen as groundwater cleanup standards. For those.
contaminants detected on Site for which no MCLs exist, Health-
Based Guidance Levels proposed by the State of Arizona have been
selected as groundwater cleanup standards. The groundwater
cleanup standards shall be met at all points within the
contaminated aquifer. .
1
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The vadose zone component of the remedy includes capping the 10-
acre Hazardous Waste Area of the landfill using a cap that
complies with the substantive capping and maintenance
requirements for Resource Conservation and Recovery Act (RCRA)
Interim status facilities as described in 40 CFR Parts 265.310
and 265.117, and as described in the "EPA Technical Guidance
Document: Final Covers on Hazardous Waste Landfills and Surface
Impoundments." In addition, the vadose zone component of the
selected remedy includes performing soil vapor extraction at all
locations at the Site where soil vapor levels exceed cleanup
standards, treating the soil vapor using vapor phase carbon
adsorption or catalytic oxidation technology (to be determined
during remedial design), and implementing access and deed
restrictions. The soil vapor cleanup standards shall be levels
that are protective of groundwater quality (meaning that the
migration of contaminants from the vadose zone to groundwater
will not result in groundwater contamination that exceeds the
groundwater cleanup standards). The soil vapor cleanup standards
will be determined through site-specific analytical modeling
conducted during the remedial design stage. Additional
investigation will also be performed during the remedial design
stage in order to determine the extent of groundwater and soil
vapor contamination.
E.
STATUTORY DETERHIDTIOBS
The selected remedy is protective of human health and the
environment, complies with Federal and state requirements
are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. This remedy uses
permanent solutions and alternative treatment technologies
maximum extent practicable, and satisfies the statutory
preference for remedies that employ treatment that reduces
toxicity, mobility, or volume as a principal element.
that
to the
Because the selected remedial action allows contaminated soil to
remain onsite in excess of health-based levels, a review will be
conducted within five years of commencement of remedial actions
to ensure that the remedy continues to provide' adequate
protection of human health and the environment.
(~.
~
Date
Daniel W. McGovern
Regional Administrator
u.s. EPA Region 9
2
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xx.
DBCXSXOB SmomRY
A.
SXTB DIm, LOCA'1'XOB un DBSCRXP'1'XOB
1.
LOCATXOB
The Hassayampa Landfill Site is located in a rural desert area
approximately 40 miles west of Phoenix, Arizona. The Site is
approximately three-fourths of a mile west of the Hassayampa
River, one and a half miles northwest of the town of Hassayampa,
three miles north of the town of Arlington, and five miles east
of the Palo Verde Nuclear Generating station. Figure 1 depicts
the location of the Hassayampa Landfill site.
The Hassayampa Landfill occupies a fenced 47-acre area located on
a 77-acre parcel owned by Maricopa County. The hazardous waste
area (HWA) of the landfill occupies a 10-acre area within the
northeast section of the landfill. For purposes of this ROD, the
site shall be defined as the 10-acre area of the landfill where.
hazardous wastes are known to have been disposed, as well as any
areas where site-related contaminants have come to be located.
2.
LAND USB
The non-hazardous portion of the Hassayampa Landfill is still
operated as a municipal landfill. Maricopa County personnel have
indicated that the expected life of the non-hazardous portion of
the landfill at the current rate of use is an additional ten
years. The HWA is fenced and is no longer being used for
landfill purposes. Approximately one-sixth of the land
surrounding the landfill is cultivated, while the remaining areas
are desert. Most of the cultivated land is located east of the
Hassayampa River and south of the Arlington Mesa. The immediate
vicinity of the landfill is sparsely vegetated. Vegetation
consists mainly of creosote bush and salt bush.
3.
POPULA'1'XOB
~..
Presently, the nearest residents live approximately 1,000 meters
south of the HWA. Communities located within a three mile radius
of the landfill include Hassayampa and Arlington. The combined
1985 census population for these two communities was 1,100
people. A growth rate of one to two percent was used to
calculate a current population of 1,120 people. According to the
Maricopa county Human Resources Department, a population growth
of 10 to 15 percent is expected to occur over the next 20 ye~rs
within a five mile radius of the site. Several workers are
employed at the non-hazardous portion of the Hassayampa Landfill.
3
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,
I
.l:-
I
~@
MARICOP A
COUNTY
SALT RIVER
~
-1
~k ~
~-$> ~
.(V
PHOENIX
INT'l
AIRPORT
I'IGUU 1
-------
-I.
CLDm'rB
The site is characterized by a dry desert climate. The average
precipitation at the Buckeye meteorological station (about nine
miles to the east) was 7.08 inches per year, most of which
occurred during a few days each year. Precipitation of 0.10
inches or more occurs on an average of 20 days per year. Records
from the Buckeye station indicate the average daily maximum
temperature is approximately 87° F, and the average daily minimum
temperature is approximately 52° F. The average pan evaporation
measured at the Salt River Valley station in Mesa (about 54 miles
to, the east) was about 106 inches per year.
5.
TOPOGRAPHY
The site is located on the broad southward-sloping alluvial plain
of the Hassayampa River basin. The basin is bounded on the east
by the White Tank Mountains, on the south by the Buckeye Hills,
and on the west by the Palo Verde Hills. The surface of the
alluvial plain occupied by the site is generally flat; however,
approximately one half mile south of the Si~e, the plain is
broken by the Arlington Mesa. The HWA is currently overlain by a
graded soil cover. The altitude of the land surface at the HWA
is approximately 910 to 915 feet above mean sea level.
6.
SURFACB WATER
The Hassayampa Landfill site lies within the Hassayampa River
drainage area, but outside of the 100-year floodplain of the
river. The site is located about three-quarters of a mile west
of the Hassayampa River, which flows to the south. The site is
near a north-trending surface water drainage divide between the
Hassayampa River and an unnamed wash to the west, which is a
tributary of the Luke Wash. The Hassayampa River and the Luke
Wash are ephemeral desert washes that are tributaries of the
westward flowing Gila River. Presently the Gila River is
perennial at its confluence with the Hassayampa River.
7.
GROUHDWATBR
"
Regional hydrogeologic units in the area of the site include in
order of increasing depth: Recent alluvial deposits, basin-fill
deposits, and the bedrock complex. Groundwater levels in the
vicinity of the site generally lie below the base of the Recent
alluvial deposits. However, where saturated, the Recent alluvial
deposits may yield moderate quantities of groundwater to wells.
The thickness of the basin-fill deposits appears to exceed 1,200
feet in the vicinity of the landfill. The basin-fill deposits
comprise the principal source of groundwater to wells in the area
of the Site, and are generally referred to as the regional
aquifer. Within a three mile radius of the Site, 349 groundwater
wells have been identified~ 172 of which potentially service
5
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individual residences. These wells yield groundwater from the
regional basin-fill deposits aquifer. The reported depths range
from 5 feet below land surface to 250 below land surface. The
nearest downgradient domestic well is about 2,500 feet south of
the site. .
The basin-fill deposits have been classified in order of
increasing depth into the Upper, Middle, and Lower Alluvium
units. The Upper Alluvium unit beneath the site was the target
of the hydrogeologic investigations conducted at the site. For
purposes of the Remedial Investigation (RI), the Upper Alluvium
unit was subdivided in order of increasing depth into the upper
alluvial deposits unit, basaltic lava-flow unit, unit A, and unit
B (Figure 2).
The upper alluvial deposits unit consists of a coarse-grained
part and a fine-grained part. The average depth to the base of
the coarse-grained part is about 34 feet; while the average depth
to the base of the fine-grained part is about 58 feet. The
basaltic lava-flow unit consists of vesicular, basaltic rock and
is part of the Arlington Mesa basalt flows. This unit appears to
thin and dip towards the north. The presence of contaminated
groundwater in unit A indicates that the basaltic lava-flow unit
is not an impermeable unit.
The part of the Upper Alluvium unit from the base of the basaltic
. lava-flow unit to the top of the Middle Alluvium unit is the
uppermost water-bearing part of the regional aquifer, and has
been subdivided into units A and B. There is no confining unit
separating units A and B, and units A and B are considered to be
water-bearing zones within the same aquifer. Unit A comprises
the uppermost fine-grained water-bearing unit, while unit B is
the uppermost coarse-grained water bearing unit. unit B is
underlain by a silty clay. This clay has tentatively been
classified as the Palo Verde Clay, and appears to comprise the
basal confining unit for Unit B.
The direction of groundwater flow in Units A and B is generally
to the south, although local variations in the flow direction may
occur. The average depth to the water table beneath the site is
73 feet. Water level contours and potentiometric contours for
units A and B are presented in Figures 3 and 4.
B.
SITB HISTORY AIm BHFORCBHBH'l' ACT:IVJ:TIBS
1.
HISTORICAL ACTrvITIBS
The Hassayarnpa Landfill is presently owned by Maricopa County and
is operated by the Maricopa County Landfill Department. Maricopa
County had signed a 20-year lease on the 77-acre parcel from the
U.s. Federal Aviation Agency, and after the lease expired in 1963
the parcel was transferred to Maricopa County by quitclaim deed.
6
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.- 'tt:RACE
DEPTH
(m) (ft)
0 0
10 JJ
'7 58
22 13 ..
IDa.
33 107
I
"-J
I
82
288
CRA
2141-28/11/11-10-0
11Ii;"il~lli'I'I.':I:i:~i::~:ii:~:'i:!;!~';:!!f~!111111!::I!:ii~.I,!ftll
PALO VERDE CiA y~
-
.umR
- SILTY SAND. GRAVEU.Y SAND
COBBlES AND SILtsTONE
INTERBEDS
.umm
- a.A 'fEy SIt T. SIt TY a.A Y
- 1EA1HERED HEAR TOP
AND \f:SlCUlAR
- 1N1tR8EDDm a.AVEY SILT
AND SANDY Sft.. T
- Sl.1Y QAy AND aAYEY SIt. T
IN1ER9EDDED WITH SAND AND
GRA\f:l
- SIl1Y a.AY
.XCJfJRB :,
SCHEMA~C HYDROGEOlOQC CROSS-SEC~ON
HASSAYAMPA LANDFILL
Maricopa Count.H Arizona
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Figure 3
Water-Level Contours for Unit A
a
V,
, .,6"-; ,%,..
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EXPLANATION
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Figure 4
Potentiometric
for Unit B
Contours
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-------
Disposal of municipal and domestic waste began at the landfill in
1961 and has continued to the present. According to a 1977
report prepared for the Arizona Department of Health Services
(ADHS), the types of waste disposed at the landfill were
unrestricted but consisted chiefly of garbage, rubbish, tree
trimmings, and other plant refuse. In that report, it was stated
that the Hassayampa Landfill was not suitable for the disposal of
hazardous waste. Based on this report, Maricopa County
prohibited the disposal of hazardous waste at the landfill.
On February 15, 1979, ADHS prohibited disposal of industrial
waste at the City of Phoenix's landfills. Because no alternate
waste disposal sites were available in Arizona, ADHS -
characterized the situation as an "extreme emergency."
Consequently, ADHS requested that Maricopa County accept
hazardous waste at the Hassayampa Landfill for a 30-day period
beginning on April 20, 1979. After the initial 30-day period,
several time extensions for hazardous waste disposal at the
landfill were granted. On October 28, 1980, the disposal of
hazardous waste at the Hassayampa Landfill was prohibited.
During the 18-month period from April 20, 1979 to October 28,
1980, disposal of hazardous waste at the landfill was conducted
under a manifest program operated by ADHS. An inventory
performed by ADHS indicated that a wide range of hazardous wastes
consisting of up to 3.28 million gallons of liquid waste and up
to 4,150 tons of solid waste were approved by ADHS for disposal
at the landfill. However, an inventory conducted by consultants
for the potentially responsible parties (PRPs), indicated that
the amount of hazardous waste approved by ADHS for disposal
consisted of up to 3.44 million gallons of liquid waste and up to
3,710 tons of solid waste.
The hazardous waste area was composed of several unlined pits
that were designated for disposal of hazardous or nonhazardous
wastes. pits 1, 2, 3 (including 3a, 3b, and 3c), 4 (including
4a, 4b, and 4c), and the Special pits were designated for
disposal of hazardous waste (Figure 5). The waste types varied
greatly and included heavy metals, solvents, petroleum
distillates, oil, pesticides, acids, and bases. specific pits
were designated to receive certain types of waste, but it is not
clear that this practice was always followed. The designated
waste types, the actual received waste types, and the quantities
for each pit, as reported in the RI report, are presented in
Table 1.
"J
....:.
pits A and B were ~esignated for the disposal of non-hazardous
waste. Although pit A was intended for cesspool and septic tank
wastes, other substances (whitish grey sludge, black oily liquid,
and pesticide containers) were also disposed (Ecology and
Environment, 1981). The contents of pit B were not well defined.
It should be noted that the wastes disposed in pits A and B were
10
-------
.S9-5
0MW-5UA
LEGEND
E] Dl5POSM. PIT: LoeeUeM 11M! tItIurMIIwf88 ,..
PIT 1 Pit. t. 2. 3e, :Ib, 4b, and 4e -.. d8term"ed
appro.lmot.., boe8d 8ft trtndtln9 operotlon..
Loco II.... ..." ,-"ertee far 0'"'' 4I8p""" S9-7
pll. or. II...." ... ....,. eI .. .IaIoucIt, 78. '181, .
oerlal pIIoto 0I"Id en report.. L-t.... ..d
IIoundorte8 ar.. '"'0''''' .." appr.."""'"
SB-7. '011C1IL SOIlIIORIfIO MW-1UO.'
AB-2A-M AHIUD SOIlIIORINO MW-1UA .
VB-'
. VAOO5f; ZONE MOIII1UR 80IIINC
EX-1a £ICPlORA11ON IIORINO
.....IUA0 UNIT A U0NI1'ORINC .u. "., a:M1IFI£R
....., U9 ED UNIT 8 MONItORINO tnL "., 1DDt11Ftm
. SOIl 0A5 SllM:Y LOCAtION
Jft AeANOONm MOft1OlllNC wnL AND IIJOI1IF1[R:
H5-1 \Jf COHSmUCItO BY ARIZONA OfJ'ARnl£NT
or HEAl. 1tf S(R~S: A8ANDOtItD .AJNF: 10M.
I
.....
.....
I
REFERENcE:
INFORMATION FOR OASE MAP
FROM ERROL L. MONTGOMERY
AND ASSOCIATES INC.
CRA
. SPE~Al
PITS AREA
'980 9-1 AD-1
SPECIAL 59-16 l0MW-4UA
IT AREA t= .59-10
. .
-7UA
MW-4U9
. . . PIT 3a
S~CI~ . ~PIT4b 0
PITS 59-13
AREA. .S9-11 (\
~979 . PIT 4c . \}PlT 40
. . .
SPEC1AL SPEC1Al
PITS 58-1
AREA" PITS
0.
MW-JUA MW-3U9 AREA'
&59-12
PIT A
.
.
.
.
.
)(-1
. .
.
.
HASSAYAMPA
LANDFILL
.
.
59-4
.
.
&59-9
.
FENCE
PRESENT HAZARDOOS
WASTE AREA FENCE UNE
o
50
150ft
.;
FlOURS 5
RI MONITORING lOCATIONS
. HASSA Y AMP A LANDFILL
Maricopa County, Arizona
-------
TABLE 1
SUMMARY OF WASTES APPROVED FOR DISPOSAL
HAS SA Y AMP A FEASIlSIUTY STUDY
QIIIJ"tity RqorUl in tile Quantity Rqtort~l by
UlJllil Wau Eoalilation Rlport Ari:D1la DqtIJrtmmt 0/
(CRA AND M&~ 1991) H~alth Seroiu.
,,~
l.iqvil Solil Litfllil Solil
Wat~ TY1'~ Wa.t~ Walf~ W4Ist~ Wa.t~
pm.) D,.ipat~l (gallo",) (tOft.) (galloft.) (toru)
Special Incompatible
Pit Hazardous Waste 174,183 2.123 134.578 308.64
Pit 1 Organics & Oils 373,755 5.0 360,805 0
Pit 2 Acids & Acid Sludges 110.930 0.1 125,597 0.1
Pits 3a, Alkaline & Metallic
band c Sludges 1.368,991 7.3 1.362,636 24.5
Pits 4a, Pesticides & Akaline
band c Sludges 1.40;'.467 ~ 1.295022.2 3.816.46
Total 3.435.326 3.735.4 3,278.638.2 4.149.7
~:
The waste amounts are determined from an analysis of ADHS approved waste manifests.
The difference between these estimates is explained in the Liquid Waste Evaluation Report
(M&A and CRA, 1991). These differences are attributed to the different solid waste volume reported
by ADHS. This solid waste difference, if converted to liquid waste, would reduce the difference in
liquid volumes to three percent.
-12-
-------
not recorded under the manifest system.
2.
SXTB DXSCOVBRY
In 1981, under the Resource Conservation and Recovery Act (RCRA)
Open Dump Inventory Program, ADHS installed three groundwater
monitoring wells at the Hassayampa Landfill. Groundwater samples
collected from one of these wells was found to be contaminated
with volatile organic compounds (VOCs). Also in 1981, Ecology
and Environment prepared a site inspection report for the u.s.
Environmental Protection Agency (EPA). In 1984, ADHS conducted
site inspections of the landfill. The Site was added to EPA
National Priorities List in July 1987.
3.
SXTB r.BVBSTXGATIOHS
The major preliminary investigation reports prepared for the
Site are summarized below:
Hydrogeologic Conditions and Waste Disposal at the
Hassayampa, Casa Grande, and Somerton Landfills,
Arizona (Schmidt and Scott, 1977);
The Hassayampa Landfill Hazardous Waste Disposal site:
Disposal Analysis (April 20, 1979 - October 28, 1980)
(ADHS, 1980);
Site Inspection Report on Hassayampa Landfill,
Hassayampa, Arizona (Ecology and Environment, 1981);
Geotechnical Evaluation of the Influence of Hassayampa
Landfill Hazardous Wastes on the PVNGS Conveyance
Pipeline (Ertec Western, 1982);
Open Dump Inventory of Hassayampa Landfill, Groundwater
Criterion (ADHS, 1982);
Hassayampa Landfill Site Inspection Report (ADHS,
1985);
Results of Preliminary Hydrogeological Investigations,
Hassayampa Landfill, Maricopa county, Arizona
(Montgomery and Associates, 1987).
l.'-.
"..:-
The Remedial Investigation for the site was conducted by the
PRPs, with oversight provided by EPA and the Arizona Department
of Environmental Quality (ADEQ). The Remedial Investigation was
initiated in 1988, and the Remedial Investigation report was
approved by EPA on April 4, 1991. A Risk Assessment report was
completed by EPA on September 12, 1991. The Feasibility study
report, which was completed by the PRPs, was approved by EPA on
May 20, 1992.
13
-------
4.
DiFORCBIIBR'l' ACTIVXTI:BS
Significant enforcement activities conducted at the Site are
summarized in Table 2.
C.
BI:GHLI:GIITS 01' COIlKUJfI:TY PARTI:CI:PATI:OB
As described below, EPA has satisfied the public participation
requirements of CERCLA section 113(k) (2) (B) and 117. EPA
currently maintains Hassayampa Landfill site information
repositories at the Buckeye Library in Buckeye, Arizona and at
the EPA Region 9 office in San Francisco. The EPA Region 9
office and the Buckeye Library maintain copies of the entire
Administrative Record File. EPA also maintains a computerized
Hassayampa Landfill site mailing list, currently with over 500
addresses. Furthermore, EPA conducted a public meeting and
accepted comments on the Proposed Plan and RIfFS. EPA has
prepared a Responsiveness Summary (Appendix B) which summarizes
EPA's responses to public comments received on the RIfFS and
Proposed Plan.
A chronological list of community relations activities conducted
by EPA for the Hassayampa Landfill site is provided in Table 3.
D.
SCOPB AIID ROLB 01' 'l'BI:S DBCI:SI:OB DOCUJIBIIT
WI:'l'BI:B THE SI:TB STRATEGY
This ROD selects remedial measures for vadose zone contamination
(including soil and soil vapor above the water table) and
groundwater contamination at the Hassayampa Landfill site. The
remedial measures selected under this ROD constitute a final
remedy for the site.
Sufficient information currently exists to select a remedy for
the site. However, additional investigation will be conducted
during the remedial design phase in order to define the extent of
groundwater and soil vapor contamination. This additional
investigation is not expected to affect the r~medy selected for
the site. As necessary, the remedial design will be modified to
reflect the additional data collected.
E.
S1JHMARY 01' SI:TB CDRACTBRI:STI:CS
1.
COIITAKXImNTS 01' COlfCBRB
Waste and Soil contamination
site-related contaminants have been detected in soil, soil vapor,
groundwater, and air at the Site.
Soil borings drilled through the disposal pits indicate that the
base of these pits (which have since been filled) range in depth
from 6 to 20 feet below land surface. Consolidated, moist,
14
-------
TABLE 2
ENFORCEMENT ACTIVITIES - BASSAYAMPA LANDFILL S.ITE
DATE ACTIVITY
1/87 EPA completes Potentially Responsible Party (PRP) Search
2/2/87 General Notice/Information Request letters sent to 8 PRPs
4/17/87 General Notice/Information Request letters sent to 78
PRPs
5/7 /87 General Notice/Information Request letters sent to 20
PRPs
6/24/87 Special Notice letters sent to all previously identified
PRPs
1/11/88 Remedial Investigation/Feasibility (RI/FS) Consent Order
signed by EPA and PRPs
11/19/91 General Notice letter sent to one previously
unidentified PRP
TABLE 3
COMMUNITY RELATIONS ACTIVITIES
BASSAYAMPA LANDFILL SITE
1987 Community Relations Plan for the site was completed
1/92 EPA issued a Fact Sheet summarizing results of the
Remedial Investigation and Risk Assessment and outlining
future site activities.
5/29/92 The Administrative Record for the Site was sent to the
Buckeye Library.
6/1/92 A public notice was published in the Buckeye Valley News
announcing the availability of the Proposed Planand the
Administrative Record and announcing the dates of the
public comment period and public meeting.
6/28/92 EPA issued the Proposed Plan Fact Sheet which explained
the results of the RI/FS, described EPA's preferred plan
for cleaning up the Site, and announced the dates of the
public comment period and public meeting.
6/1/92-6/30/92 Public comment period for the RI/FS and Proposed Plan
6/11/92 EPA conducted a public meeting during which the Proposed
Plan was presented and comments were accepted.
~
","
-15-
-------
colored material encountered within the pits is referred to
herein as waste material. Waste samples were collected from pits
1, 2, 3a, 3c, 4b, and 4c. Soil samples were also collected from
beneath pits 1, 2, 3b, 3c, 4b, 4c. No waste or soil samples were
collected from the Special Pits area due to the scattered nature
of these pits. Instead soil vapor sampling was performed in the
Special pits area. Vadose zone monitoring borings were also
installed at several locations and soil vapor samples were
obtained. Figure 5 shows the location of soil borings, vadose
zone monitoring borings, and soil vapor samples taken at the
site.
Volatile organic compounds (VOCs) and semi-volatile organic
compounds (SVOCs) have been detected in waste and soil within the
hazardous waste area. The concentrations of contaminants in
waste and soil were compared with Health-Based Guidelines Levels
(HBGLs) for surface soil developed by ADHS. The HBGLs are
derived from calculations based on ingestion of soil. The HBGLs
have not been promulgated. The only pit which contains waste
contaminants at concentrations in excess of their HBGLs is pit 1,
which contains tetrachloroethane and trichloroethene at levels in
excess of their respective HBGLs (Table 4). Similarly, the only
pit which is underlain by soil contaminants at concentrations in
excess of their HBGLs is Pit 1, which has 1,1-dichloroethene,
dichloromethane, 1,2-dichloropropane, tetrachloroethene, 1,1,1-
trichloroethane, and trichloroethene present at levels in excess
of their HBGLs (Table 4). It should be noted that the highest
level of soil contamination was detected in the deepest sample
taken beneath pit l(about 60 feet). This sample was taken
immediately above the basaltic lava-flow unit.
Waste and soil contaminant concentrations were also compared to
Toxicity Characteristic Leaching Procedure (TCLP) levels and
Extraction Procedure Toxicity (EP Tox) levels. The TCLP test was
designed to determine the mobility of organic and inorganic
analytes, and is one of the criteria used to determine whether a
material is a hazardous waste. The EP Tox test preceded the TCLP
test and has since been replaced by the TCLP test. The TCLP
levels for organics were exceeded only by waste from pit 1, where
levels of 1,1-dichloroethene, trichloroethene, and
tetrachloroethene exceeded the TCLP levels. All inorganic waste
and soil concentrations were below the TCLP and EP Tox levels
with the exception of two compounds. Chromium was detected in
waste from pit 2 at a concentration of 9.9 mg{l (compared to EP
Tox level of 5 mg{l) and lead was detected in waste from pit 3c
at a concentration of 11. 5 mg{l (compared to EP Tox level of 5
mg{l).
<",
soil Vapor Contamination
Based on the results of soil vapor surveys, several areas of soil
vapor contamination have been identified (Figure 6). The soil
,
16
-------
., -
TABLE ..
Comparison of Waste and Soil Concentrations for pit 1 to Bealtb-
Based Guidance Levels
CHEMICAL
ben%.ene
0, -dichlorobenzene
1,1-dichloroethane
1,I-dichloroethene
dichloromethane
1,2-dichloro ro ane
dimethylbenzenes (total
xylenes)
ac:etone
ethylbenzene
toluene
methyl ethyl ketone
tetrachloroethene
1,1,1-tric:h1oroethane
l,1,2-trich1oroethane
tric:h1oroethene
tric:hlorotrif1uoroethane
PIT I-MAXIMUM
WASTE CONCEN-
TRATION (PPM)
ND
97
ND
30
16
ND
ii
ND
ND
25
PIT I-MAXIMUM
SOIL CONCEN-
TRATION (PPM)
I
22
47
:lrf':~::1:;:r1::'::::\m!:::im:*::!::ili1~~ffi::!:i:: 140
94
HEALTH-BASED
GUIDANCE LEVEL
(PPM)
1,500-
12
350 200,000
2540 14,000
57 14,000
510 20,000
405 3,400
14
4,000
60
64
.4,200, ODD
-17-
~
","
-------
--.. -.-..-. - -- -_.. . ---,.
."
0°
~~
Qo
~~
~
". . ..
~
.'"
.1)
A
-X.
o C n I
...... -------.-. - -. -
. .
II 'w .;, .~." ,.... -,-" ~" '7~"'" I
I
I
I eRA ._. ,'n. .
''''I{lII} J"'''' '11/'1] UI V'
,. - - h..'
It1,,.,,-Q.. '
'- /
--'- -0__- -- ---. -- --.----. -----___-__0
- ----------1
I
I
8M'"
'tll II
R\.0\\ @
\J \J \j-PII ~
)\~ - 9'fClA'
Ptr~
. - --~_. /'''''''
I.~
. -
-.-- )11-
. M - .-.. .- ...
. -- --------
'<"{CIA,
\
\
\
Plr.;
AR( A f
--M
B
l. ---'
r-1
-
P"IIJI
~
o ~ 100"
~U ---1
'-[GEND
OISPOSAl PIT : locot'on8 and bOUhCklrt88 for "It.
I 7 .Ia, 4b ...d 4<: .... chI.....",.., ~>rim.'oIy
~ on \t'ed\'"-, ...",ttar.. locftu(Jn" ~
:"~"I:; ::-- ..:::- dt2Too~8~.":.:;r; :~= :d
0" ,C'-Mb. l-ti:1. ond eOU"doru.. orA ....10"",
and QE»OI'1Iw"'ote.
...
tOTAl COMCU<"'AI1OM (U91\.)
,DtJt1 - .~
!IOOO - Pf1f19
10. 000 - ~q-qqq
>'f7f1. non
FIGURE 6
T01 AL SOIL GAS CONCENlRA 1l0NS
HASSAYAMPA LANDFIlL
Maricopa Counfy. Arizona
. _._-_.--------- -_. ---
-------
vapor contaminants consist of volatile organic compounds (VOCs)
including 1,1-dichlorethene, tetrachlorethene, 1,1,1-
trichloroethane, trichloroethene, and trichlorotrifluoroethane.
The area in the vicinity of pit 1 contains the highest levels of
soil vapor contamination. Soil vapor contamination also exists
in an area north of Pit 1, extending beyond the boundaries of the
HWA. Investigation of the extent of soil vapor contamination
north of pit 1 is ongoing and will continue during the remedial
design phase. Elevated levels of soil vapor contamination have
also been identified in the central and southwest portions of the
Special pits area.
Groundwater
As mentioned previously, two water-bearing units beneath the site
were identified and investigated. The direction of groundwater
flow in both units is generally to the south, although local
variations in the flow direction may occur. Water level contours
and potentiometric contours for units A and B are presented in
Figures 3 and 4), while hydraulic parameters for both units are
identified below.
UNIT GRADIENT TRANSMISSIVITY CONDUCTIVITY
qpd/ft (qpd/ft2)
unit A 0.005 2,000 100
unit B 0.008 5,000 140
Analytical results for routine constituents indicate that the
chemical quality of groundwater in Unit A is consistent with
chemical quality of groundwater in shallow aquifers in the
landfill area, and that chemical quality of groundwater in unit B
is generally better than that of unit A.
Volatile organic compounds were detected and confirmed in
groundwater samples obtained from unit A monitor wells MW-1UA,
MW-4UA, MW-5UA, MW-6UA, MW-7UA, and from abandoned ADHS well HS-1
(see Figure 3 for well locations). The compounds detected in
groundwater from unit A are presented in Table A-1. Eight of
these chemicals have been detected at levels in excess of the
selected cleanup standards (see section I - The Selected Remedy
for a discussion of cleanup standards). The approximate target
zone for groundwater remedial action is presented in Figure 7.
It must be stressed that this target zone does not correspond to
a groundwater plume, but merely represents a contiguous area
within which are located the monitoring wells that have yielded
contaminated groundwater from unit A. The boundaries of the
contaminant plume will be further defined during the remedial
design phase. To date, no significant contamination has been
detected in groundwater from unit B.
19
-------
. .. .
"'.::,:.::.:.::.:.::.:.::, '::.:.::.: ':':.: ':.::':'::.:'::':'::':':: ,::.:.::,:,::,:,::,:,::" r\. "
:..::::::6fW \}i::ii:i?i\.i::\i:: Iir:\:.... 0U \\
OI!I'OSM. PI1\ l-''''' ... ...... fw ,:.'. .:,', ':' ,:.'. .:,', ,:,', :,', ':' ,.,', '.' ",,' "
Pile '. I, ~ a. .. ... .. ... ..-** '.', .',...' ",'.",',', ,', " ' , , ' , " , " ,',
............., ..... .. .......... .......... ' ,',' ,', ,'",'",'"'",'",',,,"
Locot.... .... IIeuncI8rt88 .. .... ...... ' , . ',',' ",,',',.'. ':' ',', , " ' , " '
plte - ..... .. ....,. ef . ....... 28. tilt. . , '."','
..... pttet. .... .. ........ --,UIM ...
lioii"-- .. 'III''''' ... .",.......
I
N
o
I
LEGEND
D
em,,',,','
. ',':":':.".':.
..". .
, ,
o
50
t 50ft
MW-3t)A
e
MW-2UA
,
o
TMan zaMr FaR UIIT A CIIIOUIIOIM1IIt NMUIIA1ICIII
1.'" - 811811'-- . -ut.. .... .....
vetotl. .... ..... 11M "'" ....,..
... C8II!hIM. 1""''''' "- 1M """!Me
. .,.",... .... .... . ~.. h ..... ....
.. "'- .. --- wI8th ..... .,.,.....,A'"
UOM'TWtO tIU FaR ...1 A.
IfDICAl£S RElAmt: CONHaJt1M1ICJII
f6 \IOU11l£ OROMIC COIFOUNDS
Of:1[C1tD IIfD COHnIIIoIm ..
Gll00HDWA1Ot'SMIPlLS
f) MW-JUA 8IOHI'~""
. MW-tUA
---..
IX1UIf tI1 fMan lib NIIIttM fIf H
fD'(( tit[ IS 1IIJf1II1[
HASSAYAUPA
LANDFILL
neORB 7
REf'EREHa::
1Nf00MA liON FOR BASE MAP
FROM ERROL L MONTGOMERY
AND ASsoaA1£S !HCo
TARGETED AREA FOR REMEDIATION
HASSAYAMPA LANDALL
ManCoptJ County, Arizona
" ,;;
-------
Air
Air sampling using Tenax tubes was conducted to determine the
impact of Site conditions on air quality. The results of this
sampling event are presented in Table 5. Generally, only
relatively low levels of VOCs were detected in the air samples.
Exposure by workers to VOCs in air is regulated under the
Permissible Exposure Levels (PELs) established by the
Occupational Safety and Health Administration (OSHA). The levels
of VOCs detected in air at the site are well below the PELs.
caution should be used in interpreting the sampling results as
being representative of annual average conditions, because these
results may vary with different meteorological conditions.
Soil cover in the HWA consists of a
sand which ranges from two to eight
cover appears to effectively retard
buried waste materials in the pits.
Surface Sediment
Surface sediment samples were collected from drainage channels in
the vicinity of the site. Low levels of pesticides were detected
in several samples; however, pesticides were also detected in a
background sample at similar concentrations suggesting that the
site is not the source of this contamination. The presence of
these pesticides may be the residual effect of past agricultural
activities.
reddish-brown to brown silty
feet in thickness. The soil
the release of gas from
F.
SUKKARY OF SITE RISKS
1.
IItJHA1I HEALTH RISKS
The human health assessment consists of several steps including
identification of contaminants of Potential Concern (COPCs),
exposure assessment, toxicity assessment, and risk
characterization.
a.
Chemicals of Potential Concern
For the most part, all chemicals found to be present at the Site
during the RI were identified as COPCs in the Risk Assessment
report. However, the list of COPCs was narrowed down based on
the following criteria:
".
. Common laboratory contaminants were removed from
further evaluation if the site 'sample concentrations
were less than ten times the maximum amount detected in
any blank. For all other chemicals, if the Site
contaminant concentrations were less than five times
the maximum amount detected in any blank, the chemlcals
were removed from further evaluation;
Chemicals that were judged to be present at background
21
-------
TABLE 5
SUMMARY 0' MONrrORlNG DATA FOR AIR COre. (............ 1811f/83)
D8CII ",.ocA ....oca II.I-OCI' IIUIJI
---
.. 1.l1li-
aI8rM8
STA110N
A88I8 -- C8M8 0lIII8o
f.1 TetndII. .......
AI
1210
111
1.210
,.... 4.58
4.11
81
CJ
1!2
n
02
5..f J
H2
4.'"
12
2.89
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n
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-0 (b) Ari~ - fW -... 'CIIIthdr........... - awnpdGIItJ. 0a0-UIf cIdIe """IIIII8I.I,.....1iIIit (SQL) f. -..... - 8118""'"
o (c) SluDpIe II8Dd8nI de¥I8tIoL
Q 0 (d) o-.IdaI"" 8W-..nos-.... - (-.e) + (Zel t.9S or 1.64S11(1888d8nI""')I <-a* -)"'1/111, .... ..... -....... potNrcll..
t1"J ;0 ,
Q,o
Zc:
»»
r- r-
:1
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Tel!: TddIIorodIac8e
.,2-DCr: .,2-I..Iar~.n...
TCfN:T~
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(
-------
.. ~.
concentrations were eliminated from further evaluation; and
with the exception of trichlorofluoroethane (Freon
113), tentatively identified compounds (TICs) were not
considered COPCs. Freon 113 was retained due to the
large volumes (approximately 10,384 gallons) thought to
have been disposed at the site.
COPCs were identified by environmental medium - subsurface soil
(including waste material), groundwater, and air. Onsite surface
soil is not considered a medium of concern because the HWA has
been covered with clean soil. No COPCs were identified in
surface sediments in the vicinity of the landfill. -
The specific COPCs identified for subsurface soil, groundwater,
and air are presented in Table 6. Vinyl chloride was identified
as a COPC even though it was not detected in groundwater at the
site. This decision was based on the fact that vinyl chloride is
a potent carcinogen, and is a potential breakdown product of VOCs
that were identified at the site.
b.
Exposure Assessment
The objective of exposure assessment is to estimate the types and
magnitudes of exposure to COPCs associated with the site. As
part of this process, pathways of current and future exposure are
identified. There are several pathways by which individuals
could be exposed to contaminants disposed in the HWA. These
pathways were evaluated under current land-use and future land-
use scenarios.
Under the current land-use scenario, the nearest offsite
residence is about 1,000 meters south of the HWA. If
contaminated groundwater is allowed to continue to migrate,
residents at this location could be exposed to site-related
contaminants through the use of domestic wells. Since the
prevailing wind direction is from the northeast about 50 percent
of the time, the residents at this location could also be exposed
to site-related contaminants via inhalation. Exposure of workers
to VOCs at the landfill was not evaluated by the Risk Assessment.
However, the concentrations of VOCs to which landfill workers are
expected to be exposed are well below Permissible Exposure Levels
(PELs) established by the Occupational Safety and Health
Administration (OSHA). The following exposure routes were
evaluated under the current-use scenario:
Ingestion of VOCs in contaminated groundwater migrating
offsite;
Inhalation of VOCs
migrating offsite;
Inhalation of VOCs
"
in contaminated groundwater
and
released from the site to air.
23
-------
..
CBEKICAL OF POTEN'l':IAL KBDIOM OF POTEN'l':IAL COHCBRN:,
COHCERN
SO:IL GROtJHDOTBR A:IR - ..
acetone X
benzene X
carbon tetrachloride X
chloromethane X
chromium X
copper X
dibromochloromethane X
1,2-dichlorobenzene X
1,4-dichlorobenzene X
1,1-dichloroethane X X
1,1-dichlorothene X X X
1,2-dichloroethene X .
1,2-dichloropropane X X
ethylbenezene X
lead X
methylene chloride X
tetrachloroethene X X X
toluene X X X
1, 1, 1-trichloroethane X X X
trichloroethene X X
Freon 11 X X
Freon 113 X X
xylene X X
vinyl chloride X
. '1'ABLB ,
CBEKICALS OF POTEN'l':IALOOHCERN .BY KBD:IUM
":
".e'
-24-
-------
Under the future-use scenario, exposed populations are assumed to
be present onsite and domestic wells are assumed to be installed
onsite. Potentially exposed populations evaluated included both
residential and industrial users. Although residential and
industrial use of the landfill seems unlikely in the near future,
it is not unrealistic to assume that such use could occur in the
more distant future. The following exposure routes were
evaluated under the future use scenario for both onsite
residential and onsite industrial populations:
Ingestion of contaminated soil;
Ingestion of VOCs in groundwater;
Inhalation of VOCs in groundwater, particularly via
showering (residential only); and
Inhalation of VOCs released from the Site to air.
Exposure intake parameter values were based on standard
assumptions and best professional judgement. It should be noted
that under all scenarios, it was assumed that the exposed
individuals were .adults. The only scenario under which children
would demonstrate significantly different behavioral patterns
which would affect their exposure was onsite residential
(ingestion of soil). However, as explained later, this exposure'
pathway was not evaluated quantitatively.
c.
Toxicity Assessment
Both carcinogenic and non-carcinogenic chemicals have been
identified in soil and groundwater at the Hassayampa Landfill
site. Reference doses (RfDs) have been developed by EPA for
indicating the potential for adverse health effects from exposure
to chemicals exhibiting non-carcinogenic effects. The RfD is an
estimate, with- an uncertainty of approximately an order of
magnitude, of a lifetime daily exposure for the entire population
(including sensitive individuals) that is expected to be without
appreciable risk of deleterious effects. Estimated intake of
chemicals from environmental media (e.g. the amount of a chemical
ingested from contaminated drinking water) can be compared to
RfDs. RfDs are derived from human epidemiological studies or
animal studies to which uncertainty factors have been applied
(e.g. to account for the use of animal data to predict effects on
humans). These uncertainty factors help ensure that the RfDs
will not underestimate the potential for'adverse non-carcinogenic
effects to occur. .
For chemicals classified by EPA as proven or probable human
carcinogens, risk was evaluated using cancer potency factors
(CPFs) which have been developed by EPA's carcinogenic Assessment
Group for estimating excess lifetime cancer risks associated with
exposure to potentially carcinogenic chemicals. CPFs were
multiplied by the estimated intake of the potential carcinogen to
provide an upper-bound estimate of the excess lifetime cancer
25
-------
risk associated with exposure at that intake level. The term
upper-bound reflects the conservative estimate of the risks
calculated from the CPF. Use of this approach makes
underestimation of the actual cancer risks highly unlikely.
EPA's Region 9 office has generated guidance for calculating
toxicity values for chemicals considered to be "possible human
carcinogens," such as 1,1-dichlorothene (l,l-DCE). EPA Region 9
has proposed developing a modified RfD for 1,1-DCE rather than
using its CPF. The modified'RfD is calculated by dividing its
oral RfD by a safety factor of 10.
d.
Risk Characterization
The risk characterization step of the risk assessment process
combines the information from the previous steps to determine if
an excess health risk is present at the site. Excess lifetime
cancer risks are determined by multiplying the intake levels by
the CPFs. These risks are probabilities that are generally
expressed in scientific notation (e.g. 1 X 10-6). An excess
lifetime cancer risk of 1 X 10-6 indicates that, as a plausible
upper-bound, an individual has a one in one million chance of
developing cancer as a result of a site exposure to a carcinogen
over a seventy year lifetime under the specific exposure.
conditions at a site. As is stated in the National Contingency
Plan (NCP) (40 C.F.R. section 300.430 (e», "For known or
suspected carcinogens, acceptable exposure levels are generally
concentration levels that represent an excess upper-bound
lifetime cancer risk to an individual of between 10-4 and
10-6.11
Potential concern for the non-carcinogenic effect of a single
contaminant in a single medium is expressed as a hazard quotient
(HQ), which is the ratio of the estimated intake derived from the
contaminant concentrations in a given medium to the contaminant's
reference dose. By adding the HQs for all contaminants within a
medium or across all media to which a given population is
exposed, the hazard index (HI) can be generated. The HI provides
a useful reference point for gauging the potential significance
of multiple contaminant exposures within a single medium or
across media. An HI in excess of one is generally regarded by
EPA as representing an unacceptable lifetime, non-carcinogenic
human health risk. .
As discussed previously, 1,1-DCE is classified as a "possible
human carcinogen," reflecting the fact that there is only limited
evidence available suggesting that this substance is a human
carcinogen. Thus, in accordance with EPA Region 9 guidance,
carcinogenic risk for 1,1-DCE was evaluated differently than for
other carcinogens. The evaluation of 1,1-DCE's carcinogenicity
is analogous to the calculation for the non-carcinogenic
contaminants described above. A cancer hazard index (CHI) in
26
-------
excess of one is regarded by EPA Region 9 as representing an
unacceptable lifetime human health risk.
The results of the risk characterization step are summarized in
Table 7. This table presents both typical and reasonable maximum
exposure (RME) risks calculated for the current offsite
residential, future onsite residential, and future onsite
commercial or industrial scenarios. The typical (or average)
exposure risk is based on exposure to mean contaminant levels and
mean values for contact and intake. variables, including exposure
frequency and duration. The RME risk is based on exposure to a
concentration defined as the 95 percent upper confidence limit of
the arithmetic mean concentration and 90 to 95 percent percentile
values for contact and intake variables.
For a current offsite receptor located at a distance of a
thousand meters downwind and downgradient from the site, the risk
associated with VOCs in air does not appear significant (HI and
CHI are less than one and carcinogenic risk is less than 10-6).
For the groundwater pathways, the carcinogenic and non-
carcinogenic risk levels are below the benchmarks of 10-6 and
one, suggesting there is no significant health threat. However,
the CHI for 1,1-DCE is nearly four times the acceptable level of
one (under both average and RME conditions), suggesting that
continued migration of contaminated groundwater could result in
unacceptable health risks.*
Under the future onsite residential scenario, the risk associated
with ingestion and contact with onsite waste and soil was not
evaluated quantitatively and was not summed with the other
pathways evaluated, since only limited data from the pits was
available at the time of writing the Risk Assessment. However,
due to the presence of chromium, lead, and copper and high levels
of VOCs and SVOCs in several of the pits, it was assumed that
exposure to waste and soil would result in unacceptable health
risks for onsite residents (termed significant risk in Table 7).
Risk associated with inhalation of ambient air exceeded the
acceptable benchmarks of 10-6 (average and RME conditions) and 1
(RME conditions only) for carcinogenic risk and CHI, suggesting
unacceptable health risks for onsite residents. Finally, the CHI
associated with ingestion of groundwater and inhalation of VOCs
in groundwater also exceeded 1 (average and RME conditions),
again suggesting unacceptable health risks for onsite residents.*
Since the total risk calculated for the future onsite residential
scenario does not include exposure to waste and soil within the
*
If carcinogenic risk for l,l-DCE had been evaluated using the traditional
approach, the RME risk due to ingestion of groundwater and inhalation of
VOCs in groundw~ter under the current offsite residential scenario would
have been lX10' excess cancers. Similarly, under the future onsite
residential scenario, the RME risk would have been 2X10-3 excess cancers.
Thus, carcinogenic risk under both of these scenarios exceeds the
acceptable risk range of 10-4 to 10-6 excess cancers, suggesting that
continued migration of contaminated groundwater could result in
unacceptable health risks. 27
-------
TABLE 7
SUMMARY OP ES11MATED RISKS - CURREHr AND FU'IURE lAND uses
Exposure Scenario
I. CURRENT OFF.SITE RESIDEN11AL
-&war
L
lahalatioa of Ambient Air
Toeal
Potential
a.
b.
Co
IngesaiOD or Ground Wlter
Inhalatioa of VOCs ia Ground Water
Inhalation of Ambient Air
Toeal
II. PlTI'URE OH-SITE RESIDENTIAL
I
N
00
I
. Potcntial
I.
b.
Co
d.
Ingestioca of Ground Water
Inhalation of VOCs in Ground Water
Inhalatioll of Ambient Air
Exposure 10 Wastes Below Soil ~r
Avera~e Exoosurc
Excess
Cancer
Illik
.8E-oB
8fl:!m
IE-01
7E-OR
8E-oa
m:m
CHI for Noncarcinogenic
I.I-DCE ill
2.9E-OJ
~
1.9
1.9
2.9E-OJ
JJI
2.4E-OJ
:Lm:OJ
2..0E-0I
1.9E-OI
2.4E-OJ
J.2E:m
Reasonable MlPimum E~ure
Exuu
Cancer CHI for Noawdqcaic
Ria H.OCE HI
3E41 4.sE-83 3,OE-40
JE:m UE:03 3Jm:fQ
4E-0'7 1.9 2.0E-01
2E-07 1.9 1.9£-01
JE.o1 4..5£-83 3.0£.0)
~ J.8 J.2.WI1
2E-01 1.8 1.9E-01 7£.01 3.1 3.2£.01
1E-01 1.8 1.9E-01 4E-01 3.2 3.2E-01
2E-OS 7.0E-01 S.9E-01 8E-OS 1.1 '1.3E.()l
Significant Risk SigniflWll Risk
Z~ ~ 9.'1E-OI- mot IS J.t
III. FtJI'URE ON-SITE COMMERCIAL/INDUSTRIAL
Total
Potential
a.
b.
Co
Ingestion of Ground Water.
Inhalation of Ambient Air
Exposure 10 Wastes Below SoU Cover
Total
Notes:
.
7E-OR .6.5E-Ot
IE.OS S.OE-ot
Significant Risk
~
.Lt
6.7F.-02
4.2E-01
~-
2E-07 I.t
SE-OS 7.9EoOt
SignirlCaJlt Risk
1.2E-ol
S.2C-OI
~
J1t
6.4B-oI"
It
-Acluar rercnto currendy complete exposure pathways. Risk numbers are estimates.
Risk Vollues presented do not ac:c:ount for aposure 10 wasles below the soil awer. Risks associated with CIpOIIIre 10 lhese WIlles are deemed
unaueptable since the soil meets the criteria of harardous was'e. ..
-. ,'\
-------
pits (for reasons described above), the total risk values
presented in Table 7 for this scenario represent minimum
valuesand are expected to be significantly higher. still, the
total 1risk exceeded the 10-6 benchmark (average and RME), CHI of
1 (average and RME), and HI of 1 (RME).
Similarly, under the future onsite commercial or industrial
scenario the risk associated with exposure to waste and soil was
not evaluated quantitatively, but was assumed to be significant
and indicative of unacceptable health risks for future workers in
the HWA. The carcinogenic risk associated with inhalation of
ambient air (average and RME) also exceeded the benchmark of 10-
6, indicating unacceptable health risks for future workers in the
HWA. Again, as described above, the total risk calculated for
the future onsite commercial/industrial scenario does not include
exposure to waste and soil within the pits, and the total risk
values presented in Table 7 for this scenario represent a minimum
value and are expected to be significantly higher. still, the
total risk exceeded the 10-6 benchmark (average and RME) and CHI
of 1 (average and RME).
Due to the threat of exposure to groundwater contaminants as a
result of future offsite migration of contaminated groundwater,
and the threat of exposure to contaminated waste and soil under
the residential and commercial/industrial scenarios; actual or
threatened releases of hazardous substances from this site may
present an imminent and substantial endangerment to public health
or welfare.
2.
EHVXROlOlEHTAL BVALl1ATIOB
The ephemeral Hassayampa river (which drains to the south) and
associated riparian habitat, is located about 3/4 mile east of
the landfill. Although the Hassayampa Landfill is located within
the drainage area of this river, the landfill is located outside
of the projected lOa-year floodplain of the river.
The Arizona Game and Fish Department (AGFD) identified the
Gambel's Quail, Mourning Dove, and Jack Rabbit as the most likely
game species in the area and noted that interspersed stands of .
larger trees may be used by migratory birds. The U.S. Fish and
Wildlife Service (USFWS) indicated that no listed or proposed
threatened or endangered species or biological resources would
likely be affected by contamination at the Site. USFWS did
indicate that a candidate category 1 species, the Lowland Leopard
Frog, may be found in the vicinity of the site.
Under current site conditions, there is no information to suggest
that ecological receptors may presently be exposed to site
contamination. The HWA is covered by clean soil and the
perimeter is bermed to prevent erosion and offsite drainage.
Although contaminated groundwater appears to be migrating south,
29
-------
,':
the nearest perennial surface water body where groundwater might
discharge is the Gila River, which is more than 2 miles from the
Site.
With the understanding that the HWA is covered with soil, AGFD
concludes that the likelihood of exposure to wildlife seems low.
AGFD did identify wetland and riparian habitat and associated
species along the Gila River that might be affected if
groundwater contamination were to migrate that distance.
Groundwater modeling performed in the Risk Assessment indicates
that this scenario is unlikely. There are no wetlands or
riparian habitat within the boundaries of the site.
G.
DESCRIPTION 01' ALTERD.TIVES
EPA initially considered a wide range of technologies and
alternatives for remediation of the vadose zone (including soil
and soil vapor above the water table) and for remediation of
groundwater. The alternatives which survived the screening
process and were evaluated in the detailed analysis are described
below. For all of the alternatives except for the No Action
Alternative, two groundwater options were evaluated. Since these
two groundwater options are common to all of the alternatives
except No Action, the groundwater options will be discussed
first.
The cost of each of the alternatives evaluated is presented in
Table 8.
1.
GROUNDWATER
EPA evaluated two groundwater options for the site. These two
options were identical with the exception that the treatment
systems differed. Both options consisted of groundwater
extraction, groundwater treatment, reinjection of the treated
water, and continued groundwater monitoring. The two treatment
options considered were air stripping and ultra-violet (UV)
oxidation. .
Under these options, groundwater would be extracted from unit A
using several extraction wells. Calculations performed in the
Feasibility study suggest that four to five extraction wells
operating at five gallons per minute would achieve ARARs in unit
A within a maximum of 20 to 30 years. However, the exact number
of extraction wells, well locations, and pumping rates would be
.-,
30
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ALTERNATIVE
I
w
.....
I
Alternative 1
No Action
Alternative 2
Access/Deed Restrictions
Cap
Groundwater Extraction/
Treatment/Reinjection
. .
''''.. .... ..... ..... '..' .... .. . . -... ...."...
". . . n' ...... . .... n. """......."'''''''.........
Aitijfnat£y~~......
!!!i!!!lillfllifi::
.......M 06 ~:€.q]:!'i:hg{.................... ...i.........
Alternative 4
Access/Deed Restrictions
Cap
Soil Vapor Extraction/
Treatment
Removal/Soil Washing
pit 1
Groundwater Extraction/
Treatment/Reinjection/
Monitoring
opt~on A refers
option B refers
* Present worth
TABLE 8
COST OF REMEDIAL ALTERNATIVES
ESTIMATED COST
CAPITAL COST
ANNUAL COST
PRESENT
WORTH OF
ANNUAL COST*
TOTAL
PRESENT
WORTH*
$0
$0
$0
$0
Option A
$1,531,300
Option B
$2,012,300
$2,213,100
$347,500
$3,744,000
option A
$4,980,300
$347,500
$2,213,100
$7,193,000
Option B
5,461,300
$485,500
$4,865,100
$10,325,000
to a groundwater treatment system us~ng a~r str~pp~ng.
to a groundwater treatment system using UV oxidation.
costs are estimated based on a 30-year operating period.
-------
determined during remedial design.
The extracted groundwater would be treated through air stripping
or UV oxidation. Air stripping involves the transfer of VOCs
dissolved in water to a stream of air flowing counter-current to
a stream of water over a bed of packing material.
Contaminants which have been transferred to the air stream, can
be discharged directly to the atmosphere or treated prior to
discharge. Calculations performed in the Feasibility Study
suggest that uncontrolled VOC air emissions from the air stripper
would be 1.3 lbsfday, which is substantially below the Maricopa
County guideline of 3 lbsfday and the EPA guideline of 15
lbsjday. Nevertheless, vapor phase carbon adsorption would be
required to treat air emissions from the air stripper if total
VOC emissions at the site exceed the Maricopa County guideline.
UV oxidation uses ultraviolet light and an oxidant (typically
hydrogen peroxide or ozone) to destroy organic contaminants.
Water and a small amount of chloride salts and carbon dioxide are
produced as by-products, but there are no substantial air
emissions from the process.
The treated groundwater would be reinjected, either onsite or in
the immediate vicinity of the site. The Feasibility study
indicated that one injection well screened in unit B and located
to the west of the hazardous waste area would be the most
advantageous scenario. However, the number of injection wells,
the location of the injection wells, depth of the injection
wells, and injection rates would be determined during remedial
design.
continued groundwater monitoring would be performed to monitor
and ensure the effectiveness of the remedy. The number of
monitoring wells and frequency of sampling would have to be
sufficient to monitor the effectiveness of the remedy.
Additional investigation would be performed during remedial
design to characterize the extent of groundwater and soil vapor
contamination. .
2.
VADOSE zon
Co.;,
The following alternatives were evaluated .for remediation of the
vadose zone (including soil and soil vapor above the water
table).
Alternative 1 - No Action.
Under this alternative no additional action would be taken at the
site following the RIfFS. continued monitoring would be required
at the Site, although the cost estimate for this alternative does
not reflect the cost of performing such monitoring. EPA is
required to carry a No Action alternative through the final
32
-------
detailed analyses.
Alternative 2 - Access & Deed Restrictions. Cap. Groundwater
Extraction/Treatment/Rein;ection/Monitorirta. ...
Under this alternative the perimeter fence would be upgraded and
maintained to restrict unauthorized access to the site. Long-
term deed restrictions would also be imposed, thereby restricting
future use of the site. These restrictions would include (1)
access limitations (including a requirement that a fence be
maintained around the site) and (2) use limitations restricting
future use of the Site and restricting use of groundwater beneath
the site.
This alternative would also include the construction of a cap
over the hazardous waste area. The purpose of this cap would be
to prevent direct contact with contaminated waste and soil left
in place, to reduce infiltration of water, and to reduce the
release of VOC vapors to the atmosphere. At a minimum, this cap
would have to meet the substantive requirements of a RCRA cap for
Interim Status facilities as described in 40 CFR Parts 265.310 .
and 265.117 and as described in the "EPA Technical Guidance
Document: Final Covers on Hazardous Waste Landfills and Surface
Impoundments" (EPA/530-SW-S9-047). The construction details and
design requirements of this cap would be determined during
remedial design.
As described previously, this alternative would also include
groundwater extraction, groundwater treatment, reinjection of
treated water, and continued groundwater monitoring to ensure the
effectiveness of the remedy.
Alternative 3 - Access & Deed Restrictions. Cap. Soil Vapor
Extraction/Treatment. Groundwater Extraction/Treatmentl
Rein;ection/Monitoring.
This alternative is identical to Alternative 2 with the exception
that it also includes soil vapor extraction and treatment of the
extracted soil vapors. Soil vapor extraction would involve the
installation of extraction vents in order to remove VOCs and
SVOCs from the vadose zone. These vents would be installed
within waste and soil in areas where waste and soil contamination
has been demonstrated to be a threat to groundwater and where
soil vapor has been identified as being present in excess of the
soil vapor cleanup standards (see section I - The Selected Remedy
for a discussion of soil vapor cleanup standards). A vacuum
system would be applied to the vents in order to induce air flow
through the soil, causing the VOCs and SVOCs present in the waste
and soil to volatilize into the air stream. Water in the air
stream would be condensed, separated from the air stream, and
transferred to a water treatment system. The contaminated air
stream would then flow through an air and vapor treatment system
33
-------
consisting of either a vapor phase carbon adsorption unit or a
catalytic oxidation system (catalytic oxidation is essentially a
thermal incinerator which uses a catalyst to promote the
oxidation of VOCs). The specific soil vapor treatment system
would be selected during remedial design.
Alternative 4 - Access & Deed Restrictions. Cap. Soil Vapor
Extraction/Treatment. Excavation/Soil Washing. Groundwater..
Extraction/Treatment/Reiniection/Monitoriria.
This alternative is identical to Alternative 3, except that it
also includes excavation of approximately 1,400 cubic ya~ds of
waste from pit 1, soil washing, and replacement of the treated
material. Waste that is present at levels in excess of the
Arizona Health-Based Guidance Levels for surface soil would be
excavated using standard excavation equipment. The excavated
waste would then be treated using a soil washing process. Soil
washing involves contacting the waste with water to partition the
contaminants from the solid phase to the liquid phase. Excavated
wastes would be slurried with water to remove contaminants from
the wastes and pumped through a filter press to separate the
solids from the wastes. The contaminated water would then be
collected for treatment, while the decontaminated soils would be
backfilled into pit 1.
B.
StJllMARY OF THE COMPARAT:IVB
ANALYSIS OF ALTEIUmT:IVBS
Each of the alternatives described in the preceding section was
evaluated according to the nine criteria defined below. Each
criterion is discussed in detail on the pages that follow this
. list.
Threshold Criteria
Overall protection of human health and the environment.
Addresses whether the alternative can adequately protect human
health and the environment, in both the short and long-term, from
contaminants present at the site.
compliance with ARARs. Addresses whether the alternative will
meet all Federal and State environmental" laws that are applicable
or relevant and appropriate requirements (ARARs) or provide
grounds for invoking a waiver of the ARAR.
t:';
Primarv Balancina criteria
Long-term effectiveness and permanence. Refers to the long-term
effectiveness and permanence afforded by the alternative along
with the degree of certainty that the alternative will prove
successful.
34
-------
Reduction of toxicity, mobility, or volume through treatment.
Refers to the degree to which the alternative reduces toxicity,
mobility, or volume of the Site contaminants through treatment
and reduces inherent hazards posed by the Site.
Short-term effectiveness. Refers to the short-term risks posed
to the community, the potential impact on workers, and the
potential environmental impact during implementation of the
alternative.
Implementability. Refers to the ease or difficulty of
implementing the alternative by considering technical
feasibility, administrative feasibility, and availability of
materials and services.
Cost. Includes capital costs, annual operating and maintenance
costs (O & M costs), and net present value of 0 & M costs.
Modifvinq criteria
State acceptance. Indicates whether the State concurs with,
opposes, or has no comment on the preferred alternative.
Community acceptance. Indicates whether the community agrees
with, opposes, or has no comment on the preferred alternative.
COJIPARAT:tVE ANALYSIS
Overall Protection of Human Health and the Environment
Alternative 1 is not protective of human health and the
environment since no action is taken to prevent future exposure
to contaminated groundwater. In addition, future land use could
result in direct exposure to waste material and contaminated
soil.
Alternatives 2, 3, and 4 attain similar levels of protection of
human health and the environment by preventing exposure to
contaminated groundwater through groundwater extraction and
treatment. In addition, these alternatives prevent contact with
waste material and contaminated soil through the use of a cap and
access and deed restrictions.
Alternatives 3 and 4 attain a slightly greater level of
protection as compared to Alternative 2, since they use soil
vapor extraction to reduce soil vapor contamination to levels
that are protective of groundwater quality. This reduces the
chances of exposure to the soil vapor contaminants through
exposure to groundwater. similarly, Alternative 4 attains a
slightly greater level of protection as compared to
Alternative 3, since contaminated waste from pit 1 would be
35
-------
excavated and treated. This provides additional protection in
the unlikely event that deed and access restrictions and the cap
fail to prevent direct contact with the waste material. The two
groundwater treatment options considered, air stripping and UV
oxidation, attain similar levels of protection of human health
and the environment.
Compliance with ARARs
Alternative 1 does not comply with ARARs since it would not meet
the groundwater cleanup standards. Alternatives 2, 3, and 4 all
meet ARARs. Under these alternatives, it is estimated that
groundwater cleanup standards would be met in a maximum of 20-30
years. However, since Alternatives 3 and 4 use soil vapor
extraction to prevent vadose zone contaminants from continuing to
contaminate groundwater, it is possible that these two
alternatives could attain the groundwater cleanup standards more
quickly than Alternative 2.
The two groundwater treatment options considered would both meet
the groundwater cleanup standards. It is expected that emissions
from the air stripper and the soil vapor extraction system would
meet Federal and County guidelines. In the event that these
guidelines are exceeded, vapor-phase carbon will be required in
order to comply with these standards.
ADEQ Health-Based Guidance Levels for surface soil have been
identified as TBCs for Alternative 4, which involves excavation
and treatment of contaminated waste and soil. Under this
alternative, contaminated waste and soil would be excavated and
treated to the ADEQ HBGLS. Alternatives 2 and 3 meet the ADEQ
HBGLS for surface soil indirectly by preventing exposure to
contaminated waste and soil through the use of access and deed
restrictions and a cap. .
Long-Term Effectiveness and Permanence
since Alternative 1 does not involve remediation at the Site, it
does not provide long-term protection.
Alternatives 2, 3, and 4 provide similar long-term effectiveness
with respect to groundwater by extracting and treating
contaminated groundwater. However, Alternatives 3 and 4 provide
greater long-term effectiveness with respect to groundwater as
compared to Alternative 2, because Alternatives 3 and 4 use soil
vapor extraction to prevent vadose zone contamination from being
a continuing source of groundwater contamination. Both of the
groundwater treatment options, air stripping and UV oxidation,
are considered permanent remedies.
4'-":
Alternatives 2, 3, and 4 use a cap and access and deed
restrictions to attain long-term effectiveness and permanence
36
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with respect to soil contamination. Through the use of soil
vapor extraction, Alternative 3 attains a greater level of long-
term effectiveness than Alternative 2. Alternative 4 provides a
slightly greater level of long-term effectiveness since it also
includes excavation and soil washing. However, since the volume
of soil to be excavated and treated is relatively small (1,400
cubic yards), the added long-term effectiveness is limited.
Reduction of Toxicity, MObility, or Volume Through Treatment
Alternative 1 does not involve any treatment and would not result
in a reduction of toxicity, mobility, or volume.
Alternatives 2, 3, and 4 all attain a significant reduction in
mobility and volume of groundwater contaminants through the use
of groundwater extraction and treatment. Alternatives 2, 3, and
4 would also result in a reduction in mobility of vadose zone
contamination through the use of a cap. The cap would limit the
amount of infiltration, and would thereby reduce migration of
vadose contamination to groundwater. Of the two groundwater
treatment options considered, UV oxidation attains a greater
reduction of toxicity, mobility and volume as compared to air
stripping.
Alternatives 3 and 4 attain a greater reduction in mobility and
volume of vadose zone contamination as compared to Alternative 2,
since Alternatives 3 and 4 include the use of soil vapor
extraction to treat vadose zone contamination. Alternative 4
attains a slightly greater reduction in mobility and volume as
compared to Alternative 3, since Alternative 4 includes soil
. washing of waste material in pit 1.
Short-Term Effectiveness'
since water supply wells in the vicinity of the site have not yet
been impacted by site-related chemicals and since access to the
site is currently restricted, there are few short-term risks
associated'with the site. Alternative 4, which includes removal
of contaminated waste, could potentially pose some short-term
risk to remedial workers during implementation; however, this
risk could be eliminated through proper engineering, safety, and
management practices.
Imp lementabil ity
All of the alternatives are readily implementable. Alternative 1
is the most readily implementable since it involves no action.
Alternatives 2, 3, and 4 rely on demonstrated technologies and
proven and effective methods and equipment. Of the groundwater
treatment technologies evaluated (which are identical for
Alternatives 2, 3, and 4), air stripping would be easier to
implement than UV oxidation, since UV oxidation would require a
37
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treatability study prior to implementation.
Cost
Table 8 presents a cost comparison of the four alternatives.
Alternative 1 has no additional costs since there would be no
action taken at the site. The costs of Alternatives 2, 3, and 4
increase progressively. A cost sensitivity analysis performed in
the feasibility study indicated that the net present worth of
Alternative 4 remains significantly higher than the other
alternatives irrespective of operating life. Although the
groundwater component of the remedy is identical for Alternatives
2, 3, and 4, the cost of the two groundwater treatment
technologies considered for these alternatives differs
substantially. The cost of UV oxidation is significantly more
expensive than the cost of air stripping.
state Acceptance
The state of Arizona, through both the Department of
Environmental Quality and the Department of Water Resources, has
participated in the RIfFS process. Both agencies have assisted
in the development of ARARs and the remedy selection process.
since Alternative 1 is not protective of human health and the
environment, this alternative would not be acceptable to either
agency. since Alternative 2 does not include soil vapor
extraction and there is potential for continuing contamination of
groundwater by soil vapor, this alternative would not be
acceptable to either agency. Both Alternatives 3 and 4 would be
acceptable to the two agencies.
Community Acceptance
since Alternative 1 is not protective of human health and the
environment, this alternative would not be acceptable to the
community. Several community members have expressed a preference
for treatment of contaminated soil gas, and as a result it is
unlikely that Alternative 2 would be acceptable to the community.
Alternatives 3 and 4 generally appear acceptable to the
community; although several community members have expressed a
preference for Alternative 4 since this alternative includes
excavation and treatment of contaminated soil. Finally, several
community members expressed a concern over the time required to
reach the groundwater cleanup standards under Alternatives 2, 3,
and 4.
:I.
THE SELECTED REMEDY
Alternative 3 is the selected remedy for the Hassayampa Landfill
Superfund site. The selected remedy includes vadose zone
(including soil and soil vapor above the water table) remediation
and groundwater remediation. Table 9 provides an estimate of the
38
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TABLE 9
ESTIMATED COST OF THE SELECTED REMEDY
HASSAYAMPA LANDFILL SUPERFUND SITE
Estimated Cost
Remedial
Component
Bl
B2
B8&B9
B10,B11
&B12
Description
Deed and Access
Restrictions
Cap
Soil Vapor Extraction
Groundwater extraction,
treatment, reinjection and
Capital
Cost
$ 7300
466,000
2,347,000
Annual
Cost
$ 500
5,000
Nil
Present Worth
of Annual Cost
$ 9,600
97300
Nil
Total
Present Worth
$ 17,000
563,000
2,347,000
monitoring
a) air stripping treatment
b) UV oxidation treatment
TOTAL
1,058,000
1339,000
342,000
480,000
2,106,000
4,758,000
3,164,000
6,297,000
a) 3,878300
347300
2,213,100
6,091,400
b) 4,359300 490300
4,865,100
9,224,400
TOTAL IMPLEMENTATION' COST
a)
6,091,400
(S 6,100,000
rounded)
b)
S 9,224300
($ 9,200,000
rounded)
-39-
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cost of the selected remedy with respect to the vadose zone and
groundwater components.
GROmmnTBR
The groundwater component of the remedy includes extraction of
contaminated groundwater, treatment of the water using air
stripping, reinjection of the treated water, and continued
groundwater monitoring to measure the effectiveness of the
remedy. The number, location, and pumping rates of the
extraction wells will be determined during the remedial design
stage. To date, groundwater contamination has been restricted to
Unit A, so it is anticipated that contaminated groundwater will
only be extracted from this unit. In the event that groundwater
contamination is identified in unit B, then groundwater will also
be extracted from unit B.
Air stripping, rather than UV oxidation, was selected as the
groundwater treatment technology. Both technologies are capable
of attaining the selected cleanup standards; however, air
stripping is significantly less expensive. It is anticipated
that combined air emissions from the air stripper and SVE system
at the site will meet the Federal VOC guideline of 15 pounds per
day and the Maricopa County VOC guideline of 3 pounds per day.
In the event that these guidelines are exceeded, vapor phase
carbon adsorption will be added to the air stripper (the selected
remedy already calls for emissions controls to be placed on the
SVE system). The treated water meeting the groundwater cleanup
standards will be reinjected onsite or in the immediate vicinity
of the site. The number, location, depth, and injection rates of
the reinjection welles) will be determined during remedial.
design.
continued groundwater monitoring will be performed to ensure the
effectiveness of the remedy. The number of monitoring wells and
frequency of sampling will have to be sufficient to measure the
effectiveness of the remedy.
Federal MCLs have been selected as groundwater cleanup standards
for the site (Appendix A). The groundwater cleanup standards
shall be met at all points within the contaminated aquifer. For
the chemicals detected at the site, the ADEQ MCLs and non-zero
MCLGs are identical to the Federal MCLs,.and, therefore, were not
selected as cleanup standards. For those chemicals for which
MCLs do not exist, ADEQ HBGLs have been selected as cleanup
standards. There was one chemical, 1,1-dichloroethane, for which
no ARARs or TBCs exist; however, this chemical is present at
concentrations below risk-based levels. As a result, no
groundwater cleanup standard was selected for this chemical.
40
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VADOSB SOlIE
The vadose zone component of the remedy includes installation of
a cap over the 10-acre Hazardous Waste Area, soil vapor.
extraction and treatment, and access and deed restrictions. The
purpose of the cap is to prevent direct contact with contaminated
waste and soil left in place, to reduce infiltration of water, to
reduce the release of VOC vapors to the atmosphere, and to
improve the efficiency of the soil vapor extraction system. The
design and construction details of the cap will be determined
during remedial design; however, at a minimum the cap must meet
the substantive capping and maintenance requirements for Resource
Conservation and Recovery Act (RCRA) interim status facilities as
described in 40 CPR Parts 265.310 and 265.117 and as described in
the IIEPA Technical Guidance Document: Final Covers on Hazardous
Waste Landfills and Surface Impoundments" (EPA/530-SW-S9-047).
The vadose zone component of the remedy also includes performing
soil vapor extraction at all locations at the Site where soil
vapor levels exceed cleanup standards, and where waste and soil
contamination has been demonstrated to be a threat to groundwater
quality. While the specific areas of the site which require soil
vapor extraction will be determined by EPA during the remedial
design, EPA presently expects these areas to include pit 1, the
area of soil vapor contamination north of pit 1, and several
portions of the Special pits area. The location, number, and
construction details of the soil vapor extraction vents will be
determined during remedial design. The soil vapors will be
treated using vapor phase carbon adsorption or catalytic
oxidation, as determined during remedial design. The soil vapor
cleanup standards will be levels, established by EPA, that are
protective of groundwater quality (meaning that the migration of
contaminants from the vadose zone to groundwater will not result
in groundwater contamination that exceeds the groundwater cleanup
standards), as determined by site-specific analytical modeling.
The selected remedy also includes implementation of access and
deed restrictions at the Site. The perimeter fence will be
upgraded and maintained to restrict unauthorized access to the
site. Long-term deed restrictions will also be imposed, thereby
restricting future use of the site. These restrictions will
include (1) access limitations (including.a requirement that a
fence be maintained around the Site) and (2) use limitations
(restricting future use of the site and restricting use of
groundwater beneath the Site).
Additional investigation will be performed during remedial design
to define the extent of groundwater and soil vapor contamination
at and in the vicinity of the site.
The selected remedy for the site allows contaminated waste and
soil to remain onsite. As described in section II-E of this ROD,
41
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,--~ -- --"- -.-
", , .
"Summary of site Characteristics," Pit 1 was the only location
where contaminants in waste or soil exceeded ADEQs proposed HBGLs
or EPA's TCLP or EP Tox levels for organic chemicals. There were
two pits which had minor exceedences of EP Tox levels for
inorganic chemicals. It should be noted that the HBGLs have not
been promulgated and that the TCLP levels were not necessarily
intended to be used as cleanup standards. Through the use of
access and deed restrictions and a cap, the selected remedy will
prevent direct contact with contaminated waste and soil. Through
the use of soil vapor extraction, the selected remedy will limit
the migration of vadose zone contaminants to groundwater.
EPA believes that the selected remedy provides the best balance
of tradeoffs with respect to the nine criteria. While
Alternative 4 may provide a slight increase in protection of
human health and the environment and reduction of toxicity,
mobility or volume through treatment; EPA does not believe that
these marginal benefits are necessary or justify the additional
costs. .
J.
STATUTORY DBTBRK:IImT:IOIfS
Under its legal authorities, EPA's primary responsibility at
Superfund sites is to undertake remedial actions that achieve
adequate protection of human health and the environment. In
addition, Section 121 of CERCLA establishes several other
statutory requirements and preferences that EPA must consider
when evaluating remedial alternatives for a Superfund site.
section 121 of CERCLA specifies that when complete, a selected
remedial action must comply with ARARs established under Federal
and State environmental laws unless a statutory waiver is
justified. The selected remedy also must be cost effective and
utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable. Finally, Section 121 of CERCLA includes a
preference for remedies that employ treatment that permanently
and significantly reduces the volume, toxicity, or mobility of
hazardous wastes as their principal element. The following
sections discuss how the selected remedy meets these statutory
requirements.
..,
1.
PROTBCT:IOIf OP JIUXAIf HEALTH AIm THE BNV:IROHKBIfT
Threats to human health and the environment posed by the site
include ingestion of contaminated groundwater, inhalation of VOCs
in groundwater, and ingestion and contact with contaminated waste
and soil. The selected remedy addresses the threat of exposure
to contaminated groundwater through the extraction of
contaminated groundwater and treatment to Federal and State
regulatory levels. The selected remedy requires that these
levels be met throughout the contaminated aquifer. The
implementation of deed restrictions will provide further
42
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protection by ensuring that drinking water wells are not
installed onsite.
By requiring soil vapor extraction to levels that are protective
of groundwater quality, the selected remedy ensures that vadose
zone contaminants (soil and soil vapor) will not migrate to
groundwater. The selected remedy addresses the threat of
ingestion and contact with contaminated waste and soil through
the use of access and deed restrictions and a cap. The cap will
also minimize infiltration and limit the migration of vadose zone
contamination to groundwater.
2.
COJIPLXUCB nTH ARARS
The selected remedy will comply with all Federal and more
stringent state ARARs identified in Appendix A. In addition, the
selected remedy will comply with TBCs identified in Appendix A.
3.
COST-BFFBCTrvEHBSS
The selected remedy is cost-effective in addressing the risks
posed by the site. Section 300.430(f) (ii) (D) of the NCP states
that once a remedial action satisfies the threshold criteria
(overall protection of human health and the environment and
compliance with ARARs), cost-effectiveness is determined by
evaluating the following three balancing criteria: long-term
effectiveness and permanence; reduction of toxicity, mobility or
volume through treatment; and short-term effectiveness.
The selected remedy provides the best overall effectiveness at
the lowest cost. Alternatives 3 and 4 attain a similarly high
level of overall protection of human health and the environment;
compliance with ARARs; long-term effectiveness and permanence;
and short-term effectiveness. Alternative 4 would provide a
slightly greater reduction of toxicity, mobility or volume
through treatment; however, EPA does not believe this slight
reduction ~erits the significant increase in cost.
The groundwater treatment technology selected for the Site also
provides the best overall effectiveness at the lowest cost.
Two groundwater treatment technologies, air stripping and UV
oxidation, were evaluated as'part of Alternatives 2, 3, and 4.
Air stripping (which is a component of the selected remedy)
provides a similar level of protection and treatment at
substantially less cost than UV oxidation.
... UT:IL:IZAT:IOIl 01' PBRMA1IEIr.r SOL1JT:IOHS ABD~TBRBAT~T:RBATIQmT
TECBHOLOG:IBS OR RESOURCE RECOVERY TECBHOLOG:IES TO THE nxnmK
EX'l'BHT PRACTICABLB
EPA has determined that the selected remedy represents the
maximum extent to which permanent solutions and treatment
43
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. .;'1, '..':.~
--:jl~~~C;[r,:q~l~ ;;?~-'!. '
'. : '. ,',' ':'
, .
, ,. I. ,
, ,
.', '.,'J
1
technologies can be used at the site in a practicable manner.
The selected remedy provides the best balance of trade-offs in
terms of long-term effectiveness and permanence, reduction in
toxicity, mobility or volume through treatment, short-term
effectiveness, implementability, and cost, while also considering
state and community acceptance.
The selected remedy will result in a reduction in the volume and
mobility of groundwater contaminants through groundwater
extraction, treatment, and reinjection. continued groundwater
monitoring will be performed to ensure that the remedy is
protective of human health and the environment. The selected
remedy uses soil vapor extraction and treatment to prevent vadose
zone contamination from continuing to contaminate groundwater.
Additionally, a cap will be used to prevent contact with
contaminated waste and soil and to further limit the migration of
vadose zone contamination to groundwater.
5.
PREFERElfCE FOR TREATKEIfT AS A PR:tRCIPAL ELEMDT
The selected remedy satisfies the statutory preference for
remedies that employ treatment as a principal element. By
treating the contaminated groundwater using air stripping, the
treated water can be returned to its beneficial use through
reinjection. By performing soil vapor extraction and treatment,
vadose zone contamination will be prevented from continuing to
contaminate groundwater.
The selected remedy does allow a relatively small volume of
contaminated soil (1,400 cubic yards) which exceeds ADEQ Health-
Based Guidance Levels to remain onsite. By requiring access and
deed restrictions and a cap, the selected remedy will prevent
exposure to these contaminants. EPA does not believe that
treatment of this contaminated soil is necessary or worth the
additional cost.
It.
SIGR:tFICAHT CHARGES
There are no significant differences between the remedy
identified in the Proposed Plan and the remedy selected in the
Record of Decision.
r.':,
44
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APPDDZX A
ARARs AIm 0'1'lIER CRZTERZA FOR THE SELECTED RBIIBDY.
AT THE IlASSAYAMPA LABDFZLL SZTB
This appendix identifies ARARs and other criteria to be
considered (TBCs) for the selected remedy for the Hassayampa
Landfill site. The selected remedy shall meet the requirements
of the ARARs identified below. Furthermore, unless otherwise
indicated, the selected remedy shall also meet the requirements
of the TBCs identified below.
CHEMICAL-SPECIFIC ARARs AND TBCs
Table A-I presents chemical-specific ARARs and TBCs for water
arranged by chemical compound. The Safe Drinking Water Act
(SDWA) Maximum contaminant Levels (MCLs) are based on human
consumption of water for drinking, cooking, bathing, etc.
Economic considerations and technical feasibility of treatment
processes are included in the justification for these levels.
MCLs are applicable to drinking water at the tap pursuant to the
SDWA, and are ARAR for treated water when the end use is drinking
water. Pursuant to 40 C.F.R. section 300.430(e) (2) (i) (B), MCLs
and non-zero Maximum Contaminant Level Goals (MCLGs) are relevant
and appropriate as in-situ aquifer standards for groundwater that
is or may be used as drinking water.
ADEQ Aquifer Water Quality Standards (ADEQ MCLs), established
pursuant to A.R.S. section 49-223 are identical to SDWA MCLs for
the compounds detected in groundwater at the Hassayampa Landfill
site. Since ADEQ MCLs are not more stringent than the SDWA MCLs,
these ADEQ standards are not ARARs and are not included in Table
A-I.
ADEQ HBGLs for groundwater are TBCs for the site. The HBGLs are
derived from calculations based on ingestion of groundwater. The
HBGLs have not been promulgated. ADEQ HGBLs were selected as
cleanup standards only for chemicals for which no SDWA MCL or
MCLGs existed.
Federal Health Advisories, which are criteria developed by either
EPA's Office of Drinking Water Health Advisory Program or the
National Academy of Sciences (NAS), were considered at the site.
The Federal Health Advisories are based on NAS-suggested Non-
Adverse Response Levels (SNARLs) at which no known or anticipated
adverse human health effects would occur, given an adequate
margin of safety. These Federal Health Advisories were not
selected as cleanup standards, since they were less stringent
than the SDWA MCLs and ADEQ Health-Based Guidance Levels (HBGLs).
"
I
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LOCATION-SPECIFIC ARARs
Table A-2 identifies location-specific ARARs and TBCs for the
Hassayampa Landfill site. Location-specific ARARs are concerned
with the area in which the site is located. Actions may be
required to preserve or protect aspects of the environment or
cultural resources of the area that may be threatened by the
existence of the Site, or by remedial actions to be undertaken at
the'Site.
ACTION-SPECIFIC ARARs
Table A-3 identifies action-specific ARARs for the Hassayampa
Landfill Site. The actions included in Table A-3 are components
of the selected remedy.
ADDITIONAL STATE ARARs and TBCs
Arizona Revised Statute section 49-224 is applicable or relevant
and appropriate at the Hassayampa Landfill Site. A.R.S. section
49-224 classifies all Arizona aquifers as drinking water
aquifers. section 45-454.01 of the Arizona Groundwater
Management Act (GMA) (A.R.S. sections 45-454.01), is also
applicable or relevant and appropriate to the site. All offsite
uses of treated groundwater are subject to state law outside the
context of the Superfund action. However, for activities
conducted onsite, the substantive portions of the provisions
referenced within Section 45-454.01 of the GMA shall be
applicable or relevant and appropriate.
While the State of Arizona has cited 49 A.R.S. section 282(0) (2)
as an ARAR, EPA has not identified this Arizona law as an ARAR
since it does not establish groundwater cleanup standards that
are more stringent than the federal cleanup standards selected
for the Hassayampa Landfill site. Like section 300.430(a) (iii)
of the National Contingency Plan, 49 A.R.S. Section 282(0) (2)
evinces an intent that remedial actions shall, to the extent
practicable, provide for the control, management, or cleanup of
hazardous substances so as to allow the maximum beneficial use of
the waters of the State. The maximum beneficial use of
groundwater in Arizona appears to be "drinking water protected
use," which is defined as the protection and maintenance of
aquifer quality for human consumption. See Ariz. Admin. Compo R.
18-11-501; 49 A.R.S. Section 224 (which classifies all aquifers
in Arizona as drinking water aquifers). Under 49 A.R.S. section
223, aquifer water quality standards are established as primary
maximum contaminant levels, which are the groundwater cleanup
standards selected in this ROD in accordance with CERCLA section
121(d).
2
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TABLE A-l - HASSAYAKPA LANDFILL SITE
GROUNDWATER CLEANUP STANDARDS, CHEMICAL SPECIFIC ARARS AND REQUIREMENTS TO BE CONSIDERED
CONCENTRATIONS III PARTS PER BILLION Ippb)
compou"d(A) KaxiawD selectee! Applicable Ot.ber Crit.eria S'o Be CoDaid..red
CoDC8D- C188.Dup or ael."ant.
t.rati.oD n-..rd aDd
Det.ect.ed Appropriat.e
SDWA SDWA SDWA SDWJ. 1-4., 10- lODger longer life- ADEll
1Iet. IIC:LG Propo..d Propo.. 10 109 day ~e". U". t.i.ae IIBGL
IICL d IICLG 10k9 10 109 70 109 70 k9
benzene .6 5 5 0 200 200 IiA IiA IiA
dichlorodif luoromethane .35 1400 IiA IiA IiA IiA 40000 40000 9000 30000 1000 1400
1.1-dichloroethene "2000 7 7 7 2000 1000 1000 4000 7 7
l.l-dichloroe~hane 27 N/A NA IiA IiA IiA IiA NA IiA IiA IiA
1, l.l-trichloroethane ','1500 200 200 200 100000 40000 40000 100000 200 200
1,2-dichloroethane 'BOO' 5 5 0 700 700 700 2600 N/A .38
1,2-dichlorothene(cis) '160 70 70 70 4000 3000 3000 11000 70
1, 2-dichloro&thene 160' 100 100 100 20000 2000 2000 6000 100 100.
trans
1. 2-dichloro~ro~ane 4 5 5 0 NA 90 IiA NA IiA .56
acetone 19 700 NA NA NA NA NA NA NA NA NA 700
chlorobenzene 13 100 100 100 2000 2000 2000 7000 100 100
tr ichlorof luoromethane 190 2100 NA NA NA NA 7000 7000 3000 10000 200 2100
(Freer. 11)
tr ic:hlorotr if 1 uoroet hane 610 210000 NA NA NA NA NA NA IiA NA NA 210000
(Freon 113)
methv1 ethv1 ketene 40 170 NA NA NA NA 80000 8000 3000 9000 200 170
dichloromethar.e "15 5 NA NA 5 0 10000 2000 NA NA NA
tetrachloroethene '25 5 5 0 2000 2000 1000 5000 N/A .67
toluene 15 1000 1000 1000 20000 2000 2000 7000 1000 2000
trihalcmethanes (B) 63 100 100 IiA
trichloroethene .115 5 5 0 NA NA NA NA NA
chromium(total) 40 50 100 100 1400: 1400 240 840 170 100
xylenes (total) 1 10000 10000 10000 40000 40000 10000 100000 10000
vinyl chloride(C) ND 2 2 0 3000 3000 10 50 NA
I!sa..U
Shaded Areas-Chemicals for which the maximum concentration exceeds the cleanup standard.
(A) Compounds listed were detected and confirmec in groundwater samples taken during the itI and
supplemen-:ary field investigations
(B) The awn of trihalomethanes KCL-l00 (includes chloroform, bromodichloromethane, dibromochloromethane, and
tr i):)romomethane
(C) Vi.nyl Chloride haa never been detectec1 in qroundwater samples 88 the aite, but has been detected in soil
gas samples
KCLoMaximum Contaminant Level
KCI.C-Max ir.nJ.m Contaminant Level Coal
SDft'AaSafe Drinking Water Act
N/A-t:o Standard Available
U.5. I:PA Bealth Ad...iaor.i.e&
l-day /lOkgaConcentration of compound in drinking water that could pose a risk if consume" by a 10 kg
child fer 1 day
JO-dAY/lOJc:9-Concen~rAtion of compound in drinking water that could. pose a ri8k if conswnec1 by a 10 k9
child. for 10 daya
Longer Tem/10kg-Concentration Clf canpounc1 in drinking water that could pose a risk if consumed by a 10 kg
ct,ild for more than 10 clays
Longer Term/'Okg-COncentration of c~pound in drinking water that could. pose a riek if consumed by a 70 kg
ad1J.lt for more than 70 days
Lifetime/10kg-Concentration of compound in drinking vater that could pose a risk if consumed by a 70 kg
adult for a lifetime
o.
-
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Tahle 1\.2
toca.ioIh<;pccifoc ARAR. aod O.her erileria for Ihc 'lassayampa l.aodfill Sile
l.ocalioa R£quiremcnl P"r
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Table A-J
Ac.1ion....~r8C AMARI: .nd Other Criteria lor the lluupmpa I~ndrdl Site
Shee. I or J
/\dion Requirements rreRquGilai UralMNI ARAR O,,,,,,,.n..
Containe: r Storage Containers of hazardous waste mUI' be: RCM h17.1rdouS waste (listed or charac- 40 CI'R 2104-17' (RI8-IR- ARAR The~c requirements an: applicable or relevant and
(Onsile) tenslit) held ror a tempuary period before 264.110. el seq.) appropriate for any rontaminated soil or ground waler
. Maintained in good condition treatmenl, di~posal. or slord~c elsewhere, or treatment ')'Stem waste: that mir.t\t be ron'aineri,_cd
(40 CI'R 264.10) in a container (i.e., any 40 CI'R 2104.172 AIUlR and stored onsite prior to trealment or rinal disposal.
. Compatible with hazardous waste to he ~Iorcd fM)Ttahlc device in which a malerial is
"Iured, lransported, disposed of, or
. OO$cd during 'Ionge (CICCI" to add or remove handled). 40 CI'R 2"'.173 AIUlR
waste)
Insrect container 'Iorage Breas weekly ror 40 CFR 2M.174 AIUIR
deleritJration.
1)lace ronlainers on B ,loped, crack-free base, and 40 CFIl2M.17~ AIUlR
proleel from contact with accumulated liquid.
frcwide containment ')"item with a capacity of
10 percent of the woIume of ronlaineR or rree
liquids.
Remove 'rilled or leated waste in a timely manner
10 prevent overflow of 'he ron'ainment SY5lcm.
Keep conlBiners of ignilable or reaclive wasle al leasl 40 CI'R lM.176 ARAR
50 reel rrom Ihe r.eililYs propeny line.
Keep incompolible maleri.1s ..por.'e. Scporale 40 CI'R 2104.117 ARAR
inrompalible materials Ito~d near each other by a
dike or other barrier.
AI closure, remove all huardous wasle and residues 411 r"l'll 2M.I78 AIUIR
frum Ihc containmenl system, and dc('ontaminale or
rcn10VC all containers. liners.
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Table A-3
Adiorh';porir.. ARARI and OIfIc:. Criteria (or IIIc II....yam.. l.andfiO Site
Shee. Z orJ
i\dioQ RequiJ
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"'al>leA-3
Action-.'1peri£oc ARAI!. a"" O.he, (:ri'eria lo,'he II....yam,.. 1.."""11 Si.e
StreeD of 3
ActioD Roquin:....... PrcrequGitc:6 Ulation ARAR C'.nmmcntl
Capping AI final closure of a landfill Or cell, the land(1I1 must Oosure of a RCltA interim sial us landfill 40 CI'R 26S.JIO and 265.117 AltAR Although the sile is not a RCM interim 1talus
be tapped or mainlaincd in accordance wilh 40 CI:R facility, the closure and post.cI05Un:: care regulations
26S.310 and 265.117. EPA Technical (iuiditnrc 'IlIC conlained in 40 CFR 265.310 and US.II? arc relevant
l>orunu:nl: I:inal Covers on and appropriate. I'unhermore, the capping and
IlulurdouS Wasle 11Indfills maintenance requirements dC5Cribcd in the -E.-A
and Surface Im(lOumJments Technical Guidance Document final Covers on
(EI'i\!SJO-SW -89-617) Italardous Waste l.andl1l1s and Surface
'mroundmcnl5- are lUC5. The cap .t Ihe sile will
comply with the subslaRlive design and mainlenance
rc:quiremenls specified in Ihese regulations and in Ihe
guidance document.
Underground injeclion of This regulalion sels slandards for types of AClion invotving underground injection 40 Cl'R Pans 144-147 ARAR Reinjection of treated groundwater atlhe sile shall
I realed groundwaler underground injection wells. The UIC program romply wilh thue regulations. While a permit is not
prohibifs aCfivilje( rhat .rrow movement of ~qui~d (or onsire CP.RCIA actions, fhe 'ubsranfive
rontaminanls inlo underground SQUrttl of drinking requirements would .pply for reinjection of Ireated
water which may resull in violalions of MCI..&: or gmundwale r onsite. Orfsile reinjection will have 10
adversely affect heallh. ComplianC'e wilh the UIC comply wilh the procedural and subslanrive ponions
program included. (I) meeling MCIA lor all of Ihele regulalions.
COftSiituenls reinjected, (2) submiuing invenlory
informalion, (3) oblaining a pcnnil ir lhe point of
inj<:ction is orrsitc.
Any person who diS(hafJu to an aquifer must obtain Discharge 10 an aquifer 491\.R.S.241-246 ARAR The 5ubstanlivc requirements of the permil must be
an Aquifer Prolcction permit from AI>EQ met for onsile reinjertion.
Ground-Warer Well Any nonwaste material (c.,., ground watcr or soil) Nonwasle male rial containing lisled RCRA -ronlinued in- principle ARAR CoOntaminated soil and poundwaler coolaining a lisled
Inslaltation, Ihal contains 8 listed hazardous waste musl be hazardous wasle hl7..ardouS wasle muSI be managed as. hazardous
I)evelopmenl, Tesling, mlnaged as ir it were a haz.ardous Wlste. wasle. 'll1e .conlained in- principle will not apply to
and Sampling groundwater lrelled 10 MC15 and AIJEQ IInGb It
the sile.
Ground-Waler Ground.waler monitoring .1 new or exisling RCM Creation of a new di!ipusal unil, remedial 40 CFR, Subpart F i\RAR Tl1e groundwaler moniloring requiremenls contained
Monitoring disJXMI units. ac';uns al an tJfisling HCnA un.. or in 40 C.'l,R. Seclion 26S Subpal1 Fare relevanl and
disposal of ItCltA halanJous wa!l.le appropriate for Ihe sile.
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