PB95-963136
EPA/ESD/R07-92/080
April 1995
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Shaw Avenue Dump,
Charles City, IA
3/24/1992
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."
EXPLANATiON OF SiGNiFICANT DIFFERENCES
SHAW AVENUE DOHP .
CHARLES CiTY, iOWA
Declaration
1.0
Introduction
On september 26, 1991, the U.s. Environmental Protection
Agency (EPA) issued a Record of Decision (ROD) which presented
the EPA-selected remedy for the first operable unit (OU1) at the
Shaw Avenue site in Charles City, Iowa. The remedy selected in
the ROD involved in situ fixation/stabilization of the chemical
fill and surrounding contaminated soil, installation of a low
permeability cap and ground water monitoring. The ROD also
contained a contingency stating that if treatability testing
indicated that fixation/stabilization technology was ineffective,
the material would be excavated and disposed of at an offsite
RCRA permitted disposal facility. Treatability testing conducted
subsequent to the signing of the ROD indicated that in situ
fixation/stabilization will not be adequate in treating the
chemical fill and surrounding contaminated soil at the site.
Therefore, this Explanation of Significant Differences (ESD)
provides notice that the contingency remedy will be implemented
and summarizes the basis for this change.
EPA serves as the lead agency for site activities, with
support from the Iowa Department of Natural Resources (IDNR).
This ESD is issued pursuant to Section 117(c) of the
Comprehensive Environmental Response, Compensation, and Liability
Act of 1980 (CERCLA), as amended, 42 U~S.C. ~ 9617(c), which
provides that after adoption of a final remedial action plan, if
. any settlement or consent decree under section 106 or section 122
is entered into, and if such action, settlement, or decree
differs in any significant respects from the final plan, the lead
agency shall publish an explanation of significant differences
and the reasons such changes were made.
This ESD will explain the reasons for implementing the
contingency remedy. In accordance with Section
300.435(c) (2) (i) (A) of the National Contingency Plan, 55 Fed Reg.
8666, 8852 (March 8, 1990), codified at 40 CFR Part 300, this ESD
and the information supporting it are part of the administrative
record file for the response action at ~he site. EPA has entered
into a Consent Decree under sections 104, 107 and 122 of CERCLA,
42 U.S.C. ~9604, 9607, and 9622, which would require the City of
Charles City, Iowa and Solvay Animal Health, Inc. to perform the
selected remedy. The Consent Decree is being made available for
public. comment and is consistent with the contingency remedy as
described in this ESD. ,
}
I
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2
2.0
site History and Contamination Problems
The Shaw Avenue Dump Site (Site) is located on the
southeastern edge of Charles City, Iowa, approximately 600 feet
from the Cedar River, near the intersection of Shaw Avenue and
Clark Avenue (Figures 1 and 2). The site occupies approximately
twenty-four acres, part of which is in the Cedar River 100-year
flood plain. The Site is owned by the City of Charles City. The
Charles City waste water treatment plant (POTW) is immediately
east of the Site.
The Site's primary use was as a municipal landfill by the
city. However, the waste of concern for this operab~e unit is
industrial waste. The landfill began operations sometime prior
to 1949. Disposal of solid waste by Salsbury Laboratories (now
Solvay) began in 1949 when Salsbury began significant production
and continued until 1953 when Salsbury commenced waste disposal
at the LaBounty Site. The LaBounty site has been remediated
pursuant to CERCLA. The solid wastes were generated by chemical-
batch processing of arsenic and organic compounds used in
Salsbury's production of animal pharmaceuticals. The wastes were
placed in trenches in the northern portion of the Site.
Sludge from the POTW was disposed of at the Site from 1949
to 1964. The POTW received liquid industrial wastes from
Salsbury during the time that the City disposed of its sludge at
the Site.
The Site was identified as a potential hazardous waste site
by the Iowa Department of Environmental Quality (IDEQ) in 1977.
The IDEQ studied the Site and documented arsenic contamination in
surface water in an abandoned gravel pit near the Site in several
reports issued between 1977 to 1981.
The Site was placed on the National Priorities List (NPL) in
July 1987. A Remedial Investigation/Feasibility Study (RI/FS)
was initiated in July 1988 and field work was completed in June
1990. The RI report was finished in June 1990; the Risk
Assessment was completed in April 1991; and, the FS report was
completed in June 1991.
The nature and extent of contamination at the Shaw Avenue
Dump site is summarized below. This summary is based primarily
on data generated by the work performed pursuant to the RI/FS.
Detailed information regarding the nature and extent of
contamination is -contained in the final RI report (June 1990),
which is part of the administrative record for this Site.
The areal and vertical extent of chemical fill and
associated soil contamination was estimated by analyzing samples
from soil borings, monitoring wells and trenching conducted
during the RI/FS. Chemical fill was identified in three waste
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MINNESOTA
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\ 10 Vl::' " \ \ \
~. "M.Sg,~... \. \ \ I
\D~1 C'iAR~ff ~ ~'~..
~t\ \\ . ~.1r£qLOO :\.
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.~ \- . ~,..~ ~/~('I'
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l -.~ ~/v ~ ~"" ~CUNTONi
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- MOINES ~ DA~NPCRT
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i-
SH~W ~VENU£
SITE
SOLVA'!' ANIMAl.
HEAL.TIi , 1
::£~ =:? ::~:::; SH~""" ~':::S'~':: Sl~::. ~ :/1:" S, .::.'1';£ IS?I .
FIGURE I
SITE LOC;"TION
::'.~;:".. ~'..::.\~~ 5.7::
?~C~S::;J ?!...~N
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APpnOXIMATE
:JlTf DOlJHOARY
I EGf ND
..:.--.-.--
ORT 1977
01< AND ASSOCIATES nEP
'''"NE A IIICK
~OII/ICf: fUhL .
fIGURE 2 TE SITE BOUNOARY
APPHOX~MA 5. TE
.'!lAW AVENt/EAN
~JIOI.OS£~!:~.. .
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3
cells around a city-owned maintenance facility located in the
northern portion of the site. The chemical fill is buried
approximately two to three feet below the ground surface and
extends vertically to bedrock. The thickness of the chemical
fill encountered ranges from 0.5 to 9.5 feet. The RI calculated
the total volume of chemical fill to be 370 cubic yards with
additional contamination in the adjacent soil. However,
preliminary observations from the pr~-remedial design
investigation indicate that the vol~e of chemical waste may be
closer to 600 cubic yards.
The chemical fill exhibits characteristics of process wastes
generated by. Salsbury Laboratories from 1949 to 1953. Analyses
of samples collected from the chemical fill during the RI
revealed high levels of arsenic, cadmium, chromium, and lead as
well as volatile and semi-volatile organic compounds as detailed
in Table 1. Concentrations of metal contaminants were highest in
the waste material itself, with lesser, but still elevated,
concentrations in the soil around the chemical fill. The
chemical fill and contaminated soil are considered to be the
source of contamination in the ground water.
A 200 gallon underground gasoline storage tank is located in
the vicinity of the chemical fill. The tank is owned by the City
and used as a fuel source for City vehicl~s. It is considered a
possible source of benzene, toluene, xylene, and manganese in
soil and ground water. .
Analyses of surface soil samples showed high levels of
polycyclic aromatic hydrocarbons (PAHs) and heavy metals
including arsenic; beryllium, and cadmium as detailed in Table 2.
Analyses of subsurface soil samples showed high levels of PAHs
and metals including arsenic, cadmium, and lead as detailed in
Table 3. The concentrations of PAHs are typical of those'
resulting from the burning of municipal wastes and the disposal
of asphaltic materials and are in the area of the site where
municipal wastes were burned and asphaltic materials were
disposed by the City. Additional sampling and analysis will be
conducted during the remedial design to determine the extent of
contamination in the surface soils since these concentrations
were based on composite sampling.
3.0
Selected Remedy
In the September 26, 1991 Record of Decision (ROD), EPA
selected a final remedy for QUI. The major components of the
remedy included:
-Fixation/stabilization of the chemical fill and
surrounding contaminated soil:
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'fAnI.E 1
Potential Chemicals of Concern - Chemical Fill
Shaw Avenue Dump Site
811\11 Ar Itll_t I
81189 81190 81191 81191 fol93 81195 81195 ~Our) R.nfe c "ul..... 95tll Upper
(ong/kO) (OJ/~o) (ongHO) (Dur) (IIIY/~U) (~/rJ) (lIIO/kO) (t1Q/ 9 Frequene y (1/9/ 0) r.,~) (...,/ko) Conf h'enee
(I'll/ 0) (""/~o)
(III!! kg)
Aiunoillull 740 179 691 )81 813 1220 5/5 1/9 . 1220 615 IUCI 912
AIIIIQIOIIY 4010 16200 438 IHOO 7180 611D 5/5 418. 16200 8J98 16200 13941
Antn Ic 264000 31~00 J 48200 241000 90300 8880D J 5/5 11500. 264 DOG 135000 26400.1 2285J8
Uar lUll 21.) 24 2U 81.6 JI. 5 31.4 5/5 21.J - 81.6 38 8).. 60
( adlu lUll 1300 91.1 225 1260 J90 J60 J 5/5 91.1 . 1300 651 IJoo 1150
(die lUll 210000 J 20500 J 13900 J 215000 J 80400 J 91800 J 5/5 1 1900. 270000 122240 210000 22082)
(Iorolllu8 2.6 12 45.6 6.1 11.2 14.4 5/5 2.6 . 45.6 17 45.ci 11
(o~a I I 0.97 ND I.J ND 1.1 NO 0.92 NO 5.5 4.9 1/5 0.92 . 5.5 2 5.5 4
COPller 18.8 J 202 J 45.9 J 6J J 691 J 551 J 515 18.8 . 691 204 .111 444
11'011 1410 4720 2120 1860 4200 J 14500 J 515 1410 . 14500 492 1450\1 9619
load 30.1 111 41.9 JI8 J91 2J4 J 5/5 30.7 . 111 Joo 111 539
Hdynes Iu. mo J82 JI4 667 845 1140 515 JI4 . 1510 815 1510 12.V
Hanganese 501 21.1 13.4 141 240 2J5 J 515 ZU. 501 198 5Ul 160
H~reul'Y 0.18 ND 2.1 0.28 ND 0.2 ND 2 I.J 215 0.18 - 2.1 I 2.1 2
Nickel 6.4 9.6 30.1 J5.8 188 173 515 6.4 . 188 54 lab 119
POldU lu.. 199 402 118 241 245 ' J60 5/5 118 . 402 216 402 J61
Silver 9.1 2.2 NO 1.6 ND 1.6 3 ND 2.7 J 515 1.6 - 9.1 5 !I. I 8
Sod IUI. 815 IJ20 867 2090 1290 114-0 515 815 . 2090 1276 20~0 1112
Ihaillull J.l 11.3 1.1 NO 2.] 12.8 9.6 415 1.1. 12.8 6 !l.8 II
V.ndd lUll 2 U 1.8 6.2 I.] ND 11.2 8.8 315 1.1 . 11.2 5 11.2 8
line 149 1D.9 NO 95.6 304 851 882 J 5/5 10.9 - 882 292 dd2 586
Crdn Ide 10.2 4 1.9 1.1 ND 1.6 114 I. J . 10.2 4 lo.~ 8
("9IkO) ("0Ik9) ("O/kO) ~ ("OlkO) ~ !t.o/ko) ("O/kO) ("O/kO) ("olkll) ~L Jf2!~~1. -1cilliL
N IIroben/ene JIOoo NO 5500000 NO 1900000 J 460000 NO R 61 dodo NO 5100000 NO A 1/4 31000 - 5500000 11 J2150 550,1000 580J591
?'lIllrol.loenul JlooO NO 5500000 NU 200000 NO R I 30.0000 J 610000 NO 5100000 NO 114 JIUUO. ~ 500000 1101150 5~.OOO.hl 51628/6
? N 11,.001111111. 150000 J 5300(JOOO J ?00000 Nil J 3900000 J 5900000 J 95000000 J 415 200000 . Y5UUOOOO )04 9C1OUO Y~IJIIU"(JII bLhHI.M
~.4' -0111 99 ND J 1)00 HU J 6100 J lIU NU J 680 NU J 540 NO J 1/5 99. 6100 1689.8 olUu JMU
!!!!~~~.:.
~II H"n-~'Iecl ~alues w~re USUlled equal 10 lloe deleCllon Illill w...n ukulatlno Ihe me.n concentr.ll"n.
2 r".. dupllcdle samples, Ihe hloher eOllcelllul Ion 01 Ihe two ~aOlples was used 10 calculAte the lean concenlrat 1011.
- Ihe .SlodalecJ nUII1~rlcal va1ue h an est 100JI~d qualllllr'
" . Ihe dala Is unu'a~Ie (o'npound IlIJr or .oay 1101 be ')f~s.n ).
III' - A "oll.d",ed valu~; I" aHoelaltd nu"'trl. al v.lue re'lfestllh 1/.. detecllon 1111111 01 the laLo..ator~ dppdralus.
II . I, ,.un-Odec I .a lue; Ih~ dHoe laled lIun,erlco I .olue «prose." Ih. delecll,," 11.,11 01 Ih. laborolor~ dl'paralus.
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TAnI.~ 1
Potential Chemicals of Concern - Chemical Fill
S.haw Avenue Dump Site
Ar IIhmeti
81189 DII~O 81191 f.1I91 8119) f.1I9) . 81195 81195 ~~r) Ranre ( Haollll.. 95111 UPl'ft"
(mg/~lI) (III//~g) (""JILg) Our) (1II!J/~g) Our) (III//~II) (..,,1 II hequenq ("'III 0) (~f;:~) (..../Lg) Cont Idenr e
("JIll) (111/1 0) (.~/~II)
-
Heillylene Chlurlde 19 NO 140 NO J 2J 12 J 9 NO 9 NO J 16 NO J) NO 1/5 9 . 140 41.1 Uu 8~
Ac e lone J2 J 140 NU II 28 NU 160 R 18 NO 18 NO R )1 NO J 26 NO J 1/4 18 . )1 21.25 II J4
I, I .0 leh lorut\hene 10 Nil J ~I J 210 18 J 21 J 9 "0 J 16 NO I] NO )/5 10 . 210 10.8 210 141
(II lurotul'. 10 NU 69 Nil J 11 II J 9 NO 9 "0 J 16 NO 1) "0 1/5 9 - 69 24.) bY 411
I,l-Olellloroelhane 10 NO 69 NO J 2S 9 J 9 NO 9 Nil J 16 NO J) NO 1/5 9 . 69 25.8 6\1 41
1,1,2-' rlell loroolhone 10 NO 110 J 510 210 J 81 110 J 42 21 4/5 10 - 510 162.6 510 JJb
Uenlene 10 NO 6Y Nil J 150 62 J 9 NO 9 NO J 16 NO J) "o lIS 9 - ISO 50.8 I~U 101
1 ell'dell loroelhlne 10 NU 69 "0 ,J 26 14 J 9 "0 9 "0 J 16 NO U NO 115 9 - 69 26 69 H
10lueil0 10 NO 69"11 J 19 48 J 9 NO 46 J 16 NO, U NO 2/5 10 - 19 )6.6 19 116
'CII loro~ellltne 10 NO 69 NO J 240 88 J 9 9 J 16 NO U NO 2/5 II . 240 68.8 i40 15.
[llIyl~elllene 10 NO 69 "0 J 380 210 J 18 2)J 16 Nil \J NU 2/5 10 . )80 98.6 JdO lH
Xylene (IUIdI) 10 Nil 480 J 680 530 J 110 140 J 22 J) NO 4/5 10 . 680 262.4 ~~O SU
~
....., ~./'
!!~
!I) Non.delell .aloe, were auulled equl 10 Ihe deleellon 1,'11" ..hen ul(ulallno Ille IICdn concenlratlon.
2) 1'0" d!lpllCdle samples, Ih. hlolo.r eon(."Io'ollon ot Ihe Iw" '."plt' .... used 10 Cd\culole Iho ....n eoneenlrot tun.
. 11.. JBuclaled numerical .olue h an esth.lled quanillr'
R - Ihr. dol. h unusoble '(coml'ound ...y or ...y nol bf pt"fsen ).
1m - A ""n.dderl .aloe; Ih. assocloled nUII'"rlul ..Iuo repre~.lIls Ih" delectlon 1111111 ot the 'oborolory apparolus.
II . A IIOf"O~'HI vdlue; Ihe dHOclJleJ 1I1I1,,"r":.1 vdlue r.pr.~ellis Ih. dol",II.n 11...11 ur Ihe lobur.lory Ol'p."aills.
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Potential
Table 2
Chemicals of Concern - Surface
Shaw Avenue Dump Site
Soil
Area I Ar~d 2 Area 2 (Oup) trea) trea 4 Aait~e Arllhonellc "ax 11118 9~lh Upper
(akJ/~g) (akJ/.g) (RiQ/kg) 111\1/./1) 1I19/.g) r requency (IIIIJI 0) "~an ~I.2) (D,/HO) Conlldence
~JLL (DJ/~g)
A"$.n Ic 12 ~.'J 6.2 1.1 4.4 4/4 1.1 - 12 6.1 12 II
Ueryll ium . 2.1 NO 1 NO 4.4 J 2 NO 2 NO 1/4 2 . )9.6 11.4 )9.6 31
(d,lmlum . 2.1 NO 2 NO 4.2 J 2 NO 2 NO 1/4 . 31.8 II )1.8 29
Co"oll . ~.1 ~ NO 42 J ~ NO ~ NO 2/4 . ]18 110 )18 29)
Nidel 12 1.1 ~4 J 1.) 10 4/4 1.) . ~ 21 ~ 4J
~II! ~ --fu~L ~ ~ ("g/kg) (,,0/k9) -1ill~ ~ (,,0/k9)
Pt,~n.n' hrene 6~ NO 120 11 6~ NO 10 l!4 10 - 120 6S 120 III
r luordnll,ene 130 1/11 140 I JO NO IJO NO 210 2/4 1)0 - 210 IS) 210 19)
Pyrelle 130 NO 160 1)0 1)0 NO 210 2/4 130 - 210 163 210 20)
0.11'0(0 )dlllhrdcue 6~ 1111 6J 6~ NO 6S NO 130 2/4 6~ . 110 86 130 111
ChI' yu~nt= 6~ NO 61 6~ I/O 6~ NO 140 2/4 6S - 140 84 140 122
!!~!..!:!l.
fl I/oll-~~Iecl values ..ere duuaK:d equdl 10 Ihe delecllon limit ..hen ulcul"lIng IIle mean concenlrallon.
l ror dupllCale samples, Ihe higher COllcenll'al ton 0' Ihe Iwo ~aQ1111cs was used 10 c"lculdle Ih~ loedn (oncenlrdt Ion.
- 'he aUuclaled nUI"!"'cdl v.lue Is an estlolJled 'rdnilly. .
Nil - A non-delect volue; Ihe "ssucldled lIulierlcal vo ue represen" Ihe detecllon 11.11 0' Ihe I"buralory apparatus.
. - The surlace soli rhula. refl~cl Ih~ re$ults 01 a c0"'l,oslle 01 nille samples Inr each al'U. rPA Replon VII has laken Ih. pos!!lon Ih.1 Ihe r05ul" 01
any 0' I he $url ace su II SO'''l'les In I h,,1 arta ulJy be dl a va lu~ 0' n Ille IIlICs the I'el'orled Vd lue. 1I,ere ure. , ur I h Is e..I..llon. lI,e o.Ikl...8 COllcelllralloll
Is 'Ii" .",.,u..O COIIc.nl,ol iulo 'ur ..,.ylllull. c.d",lu,., .110 c"Ii.1I uIIl\lplled by nine.
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Potential
Table 3
Chemicals of Concern - Subsurface
Shaw Avenue Dump'Site
Soil
01l5A 011511 11115e BII5C ~I ~15A Ranre Ar It hili! I 1\ Hul.... 951h Upptr
ImcJ/kg) (my/kg) (1II!I/kg) ~illL (1IIg/kU) (lIQ/kU) frequencJ ' (1101 0) Htan Al,z (lIQ/kU) Conf Idence
.J~. ~L
Arsenic 15 21 )50 120 1 J5 J 14.2 5/5 14.2. J50 101 J50 ZJI
CadaliulII NO NO J9 J 6.5 J 1.1 2.2 NO 2/5 1.1 . J9 9.) J!I 2)
CO!'Per JI 4.5 4.9 4.4 164 J 41 J 5/5 4.5 . 164 49 11>01 106
I tdd 1)0 29 20 2Z J2J IJI J 5/5 22 - )2) 121 )2) 2)1
HangdlltSe 260 J 460 J 2~O J ]/0 J 186 J 401 J 5/5 IB6 . 460 )41 460 4H
llnc 410 J 26 J 611 J Jl J J02 J 299 J 5H 26 . 410 221 410 J62
~L jillW. ~L -WfuL fulW ~L (I.g/kg) (~g/kg) (1'9/kO) j~ (1'0/' g)
Iluorene 20000 ]/0 NO 140 HO )10 NO 160 NO 1J0 NO 1/5. 140 . 20u00 4446 20000 1186)
Phendnthrene 1611000 ]10 Nil J40 Nil )10 NU 160 NO 1)0 NO 1/5 J40 . 160000 JlH6 160000 93255
Alllhrd(~n~ 6"000 Jl0 HII 140 HO ]10 HII 160 NU 1 JO NO 1/5 )40 . 88000 1811'16 11800U 51 )96
Iluordnllo.lle 190000 Jl0 "" J40 NO ]10 NO 9)0 1000 NO J J/5 . )40 - 1900UO J85J4 190000 110141
Py."eue 200000 )10 Nil J40 HII )10 NU 810 no NO 2/5 J40 . 200000 40468 200000 116m
Btnlol a )dnl hracene . 94000 310 NO 340 hO ]10 NO 160 NO 1J0 NO 1/5 140 . 94000 19246 94000 S4884
Chr~~e". 10000 )10 Nil )40 NO )10 NU 160 NO 1J0 "0 1/5 ]40 . 100000 20H6 100000 58HZ
1I1s(2 -.1 hylhcxJI )phlhd lale 19000"0 J Jl0"0 J 140 "0 J 800 J 160 NO no "0 1/5 J40 . 19000 4H2 19000 11)26
DenlOl b)I luoranl helle 94000 Jl0 HO 340 NO )10 NO 160 "0 1J0 NO 1/5 340 . 94000 19246 94000 54884
OOlllO(.)Iluordnllo.ne 65000 )/0 HII ].10 NO )10 NO 950 . ]]0 NO 215 340 . 85000 114114 85000 496/2
oenlO( a )pyrene 112000 ]10 HO 140 Nil )10 NO 160 NO ]]0 NO 1/5 )40 . 82000 161146 82000 41901
I IIdellu( I ,2, I-cd )pyren. 4/000 ]/0 HII )~O NO Jl0 NO 160 NO no Nil 1/5 140 . 4/000 9b46 4/000 21559
II i~elllO( d, h )dnlhrdcene 21000 ]10 Nil .140 NO )10 1111 160 NO ])0 NO 1/5 )40 . 21000 4bU 21000 12444
lIelllo(O,Io,I)perrlelle 51000 )/0 Nil ~U NO UO NO 160 NO 1J0 NO IH )40 . 51000 IOM6 51000 29m
Hule~:
r! NOll-doteCi valuu ...... h~ulltd equdl IU 1100 d.leclloll 11.11 wloen cdlculallnl/the "",an conunlrallon.
2 for dupllcdte sa."lc~, Ihe higher concenlrallon 01 III. IWI) sa"pl.s was osed 10 cdlcul.te Ihe llean concentrallon.
. lhe usoclated nunk!rlul Vdlue h an eSllmdted ~uantllr.
HII - A non.det.cl vdlue; Ihe dssoct.te,t numerical Vd ue I'tpre~cnlS Ihe delecllon 111111 01 Ih. laburdlorr apparatus.
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4
-Installation of a low permeability cap to protect the
fixated/stabilized material; and
-Ground water monitoring during and after
implementation of the fixation/stabilization
determine the effectiveness of the remedy in
leaching of contaminants to ground water.
to .
preventing
The ROD stated that the objectives of the remedial action
are to eliminate or reduce to a" acceptable level the risks posed
by exposure to the contaminated soil and chemical fill and to
eliminate or reduce the potential migration of contaminants into
the ground water. The ROD further stated that if treatability
testing shows that fixation/stabilization was not adequate in
treating the chemical fill and surrounding contaminated soil, the
contaminated material would be excavated and removed to a RCRA
approved landfill. .
4.0
Significant Differences and the Basis for the Difference
4.1
summary of New Information
. Data from treatability testing conducted by the Solvay
Animal Health, Inc. and the city, conducted after the September.
"26, 1991 ROD, indicates that the stabilized/fixated chemical fill
would not meet Land Ban requirements for leachability. The
treatability data for three reagents, cement, cement/fly ash, and
cement kiln dust, show Toxicity Characteristic Leachate Procedure
(TCLP) results of 33.4 mg/l, 39.9 mg/l, and 30.0 mg/l
respectively. The Land Ban standard for TCLP for arsenical
wastes is 5.6 mg/l. In addition, the arsenic concentration in
the sample used for the treatability testing was less than 20,000
ppm and the RI data for the chemical fill ranged from 88,000 ppm
to 264,000 ppm, meaning that the treatability sample may not have
been representative. Results from a more representative sample
could have even higher TCLP figures. "Further, in situ mixing may
not be as effective as laboratory mixing and could result in
higher TCLP numbers in the stabilized/fixated monolith.
EPA Region VII has also reviewed treatability results from a
similar Superfund site that had high concentrations of organic
. arsenic along with calcium carbonates. Treatability data from
fourteen studies was available for this site and none of the
results indicated that fixation/stabilization would achieve the
desired results. Again the concentrations of arsenic were lower
than what is believed to be present at the Shaw Avenue site.
4.2
Significant Differences
As indicated above, EPA is proposing to implement the
contingency remedy as described in .the ROD. The only difference
from the contingency remedy described in the ROD is that prior to
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5
disposal of the chemical fill and contaminated soil at an offsite
landfill, the contaminated material will be stabilized/fixated,
to the best practicable level if the contaminated material fails
TCLP. This treatment will satisfy the CERCLA preference for
treatment. .
This alternative will involve the excavation and removal of
the underground gasoline tank and excavation and offsite disposal
of the chemical fill material and surrounding contaminated soil.
The excavated underground storage tank will be disposed of
pursuant to the Underground storage Tank regulations. The
excavated chemical fill and contaminated soil will be disposed of
at anoffsite RCRA permitted disposal facility. . The excavated
area will then be backfilled with clean material.
The excavation of the chemical fill and surrounding
contaminated material will be accomplished using a track mounted
bac~oe. Verification testing will be conducted to assure that
the performance standards have been met. The Performance
. Standards provide that all soil, chemical fill and waste
materials above the following levels shall be excavated:
Arsenic
Cadmium
50 parts per million
20 parts per million
Vertically, excavation of the chemical fill and contaminated
soil will initially extend from the ground surface to the
chemical fill/soil contact or known depth of contamination above.
the performance standards, or to bedrock, whichever is
encountered first. Where bedrock is encountered, the bedrock
surface will be scraped by the backhoe and the scrapings disposed
of with the chemical fill and contaminated soil. Horizontally,
excavation of the chemical fill and contaminated soil will extend
a minimum of two feet beyond the limit of the chemical fill.
However, this may be modified based on the results of soil
sampling conducted in February 1992. Confirmation sampling will
be completed at fourteen foot intervals along the perimeter of
the excavation to determine that all soils exceeding the
performance standards. have been excavated. .
Excavated material will be loaded by backhoe directly into
lined trucks for transportation to the designated RCRA landfill
sites. Shipments will comply with all RCRA and Department of
Transportation requirements for shipment of hazardous waste.
When all of the identified contaminated soil has been
excavated, loaded and transported to the designated approved RCRA
landfill, the excavation will be backfilled with clean fill. The
fill will be placed in 12-inch lifts and compacted to a minimum
of 90 percent of the standard Proctor density. The upper six
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6
inches of the excavation will be backfilled ~ith clean topsoil
over which a vegetated cover will be placed. Backfill standards
will be those required for RCRA closure.
The chemical fill and contaminated soil will be
fixated/stabilized prior to disposal in the RCRA approved
landfill using the best practical means as determined by
treatability testing currently being conducted. Treatment will
not be required. for excavated soil which exceeds the performance
standards but which has a TCLP of less than 5.0 mg/l of arsenic
and 1 mg/l of cadmium.
The groundwater monitoring program will utilize the existing
wells from the Remedial Investigation, two private wells located
adjacent to the Site, and a well in a location yet to be
determined in or around the backfill. The two private wells are
not in use as water supplies. The groundwater monitoring results
will be utilized to evaluate the effectiveness of the excavation
and off-site disposal of the chemical fill and surrounding
contaminated soil in preventing and/or reducing the leaching of
contaminants to the groundwater: for the Superfund five-year
reviews required pursuant Section 121(c) of CERCLA: and
to assist in the determination of the remedial action for
Operable Unit 2 (OU2).
The excavation and off-site disposal of the chemical fill
and surrounding contaminated soil will take approximately two
weeks and cost approximately $950,000. No Operation &
Maintenance costs will be associated with the contingency remedy
because there will be no O&M necessary for the backfill material.
The groundwater monitoring program will cost about $150,000 and
will continue indefinitely. The estimated volume of chemical
fill in the. ROD is 370 cubic yards, but may be closer to 600
cubic yards.
No chemical or location-specific Applicable and/or Relevant
and Appropriate Regulations have been identified for this
alternative. Major action-specific ARARs for this alternative
include the RCRA requirements located in 40 CFR Part 264, the
underground storage tank regulations (40 CFR Part 280,
Subpart G), OSHA, and the Iowa Rules for Determining Cleanup
Actions and Responsible Parties (I.A.C., Chapter 567-133). All
Department of Transportation regulations applicable to
transportation of hazardous waste would have to be observed.
This alternative would also have to meet RCRA Land Disposal
Restrictions (40 C.F.R. Part 268) which require treatment of the
hazardous waste prior to disposal in a RCRA-authorized hazardous
waste landfill. The type of treatment would be dictated by
requirements of the RCRA Land Disposal Restrictions. Under
current regulations this material does not require treatment
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7
prior to disposal. However, in May of 1992 the Land Disposal
Restrictions will require treatment prior to disposal of these
materials.
One correction to the ROD is on page twelve in the
discussion of the arsenic concentration in the Cedar River
resulting from the Site and the existing concentration in the
river. These concentrations shoUld be in parts per billion.
Therefore, the correct contribution from the Shaw Avenue site is
one part per billion and the existing concentration in the river
is twenty parts per billion.
5.0
Affirmation of the statutory Determinations.
Considering the new information that has been developed and
the changes that have been made to the selected remedy, EPA and
IDNR believe that the remedy remains protective of human health
and the environment, complies with Federal and State requirements
that are applicable or relevant and appropriate to this remedial
action, and is cost effective. In addition, the contingency
remedy, as revised, utilizes permanent solutions and alternative
treatment technologies to the maximum extent practicable for this
site.
6.0
Role of community in the Process
The EPA solicits input from the community on the cleanup
methods proposed for response actions. This ESD, along with
other documents which formed the basis for the changes in the
remedy can be found in the administrative record file. The EPA
encourages the public to review these documents to gain a more
comprehensive understanding of the site and ongoing activities at
the Site. The administrative record file is available at the
Charles City Public Library.
Please submit written comments on this ESD to:
Hattie Thomas, Office of Public Affairs
u.s. EPA, Region VII
726 Minnesota Avenue
Kansas City, Kansas 66101
If you have any questions or need additional information on
the Site, please contact:
u.S.
Paul Roemerman
Environmental Protection Agency
Region VII
Office of Public Affairs
726 Minnesota Ave~ue
Kansas City, Kansas 66101
. (913) 551-7694
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION VII.
726 MINNESOTA AVENUE
KANSAS CITY, KANSAS 66101
MAR 2 4 1~
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MEMORANDUM
SUBJECT:
David A. Wa oner
Director, Waste Management Division
Explanation of
Shaw Avenue Du
Iowa
FROM:
TO:
This Explanation of significant Differences notifies the
public of the decision to. implement the contingency remedy of
excavation and offsite disposal of the chemical fill and
contaminated soil at the Shaw Avenue Dump Site in Charles City,
Iowa. Treatabili ty data reviewed by the U. S. Environmental
Protection Agency (EPA) indicated that the selected remedy of
fixation/stabilization was ineffective. Implementation of the
contingency remedy will take about two weeks and is scheduled for
April 1992.
The major components of this remedy include excavation with a
hydraulic excavator, and treatment and disposal at an offsite RCRA
permitted landfill:
This Explanation of Significant Differences has been
coordinated with the Office of Regional Council, the Office of
Public Affairs, the Congressional and Intergovernmental Liaison,
the Agency for Toxic Substances and Disease Registry and the Iowa
Department of Natural Resources.
On December 27, 1990, the remedy selection authority for the
Shaw Avenue Dump site was delegated to you by Don R. Clay,
Assistant Administrator. I recommend approval of the contingency
remedy. .
hPPROVE:
DISAPPROVE:
.
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