### ? * 1 v - ' 0 '^^"JL'L. 

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F . O'CONNO RCOMPAN Y SUPERFUN D SIT E
RECOR D O F DECISIO N AMENDMEN T

OPERABL E UNI T 2

Septembe r

200 2 U.S
. Environmenta l Protectio n Agenc y - Regio n I

Ne w Englan dDECLARATIO N FO RTH E RECOR D O F DECISIO N AMENDMEN T

A . SIT E NAM E AN D LOCATIO N F , O'Conno r Compan y Superfun d Site Augusta , Kennebe c County , Main e CERCLI S Identificatio n Number : MED98073147 5 PR P Lea d Operabl e Uni tTwo , Managemen tO f Migratio n
B . STATEMEN T O F BASI S AN D PURPOS E Thi s decisio n document

present s an amendment

t o th e selecte d remedia l actio n fo r th e F
. O'Conno r Compan y Superfun dSit

e i n Augusta , Main e whic h wa s chose n i n accordanc e wit h th e Comprehensiv e Environmental Response , Compensation , an d Liabilit y Ac t o f 198 0 (CERCLA) , a s amended , 4 2 U.S.C
. § § 960 1 et . seq . an d th e National Oi l an d Hazardou s Substance s Pollutio n Contingenc y Pla n (NCP ) a s amended , 4 0 C.F.R
. Part

300
. Th e Directo r

o f th e Offic e o f

Sit e Remediatio n an d Restoratio n ha s bee n delegate d th e authorit

y t o approv e thi s Recor d o f Decisio n Amendmen t

(RO D Amendment).
. Thi s decisio n wa s base d o n th e Administrativ e Record , whic h ha s bee n develope d i n accordanc e wit h Sectio n 11 3 (k) o f

CERCLA , an d whic h i s availabl e fo r revie w a t th e Lithgo w Publi c Library i n Augusta , Main e an d a

t th e Unite d State s Environmenta l Protectio n Agenc y (EPA ) Regio n 1 Offic e o f Site Remediatio n an d Restoratio n (OSRR ) Record s Center i n Boston , Massachusetts
. Th e Administrativ e Record Inde x (Appendi x B o f thi s RO D Amendment ) identifie s eac h o f th e item s comprisin g th e Administrativ e Recor d upo n whic h th e selectio n o f th e remedia l actio n i s based
. Th e Stat e o f Main e ha s concurre d wit

h th e selecte d remedy
. C
. ASSESSMEN T O F TH E SIT E Th e respons e actio n selecte d i n thi s RO D Amendment i s necessary t o protec t

th e publi c healt

h o r welfar e o r th e environmen t

fro mactual o r

threatene d release s o f

hazardou s substance s into th e environment
. D . DESCRIPTIO N O F TH E SELECTE D REMED Y Thi s RO D Amendment

change s th e remed y originall y selecte d i n th e 198 9 RO D fo r th e managemen t

o f migratio n operabl e uni t

(OU-2)
. Thi s RO D Amendment make s mino r

change s an d clarification s t o th e sourc e contro l an d Rigg s Broo k remedie s (OU- 1 an d OU-3 , respectively)
. Th e majo r component s o f

th e selecte d remedy include :

• Institutiona

l control s t o preven t

th e us e o f

contaminate d groundwater ;

• Waiver

o f federal an d state drinkin g wate r standard s fo r

alimite d portio n o f

th e Site o n the basi s o f

technica l impracticability ;Activ e recover y o f separate-phas e oi l fro mth e overburde n soi l an d bedroc k throug h annual implementatio n o f

avacuum-enhance d recover y systeman d passiv e recover y betwee n thes e annua l implementations ; Long-ter mmonitorin g o f

sit e groundwate r

o n aregula

r basi s to evaluate change s i n sit e condition s over

time ; an d A revie w o f

th e Sit e ever y fiv e year s t o ensur e that

th e remed y remain s protectiv e o f huma n healt

h an d th e environment
. E
. STATUTOR Y DETERMINATION S Th e selecte d remedy fo r

OU- 2 i s protectiv e o f

huma n healt

h an d th e environment , complie s wit h Federa l an d Stat e requirement s that

are applicabl e o r

relevant an d appropriat e t o th e remedia l actio n (unles s justifie db y awaiver) , i s cost-effective , an d utilize s permanen t solution s an d alternativ e treatmen t (o r resourc e recovery ) technologie s t o th e maximu mextent practicable
. Th e remedy als o satisfie s th e statutor y preferenc e fo r

treatmen t a s aprincipa l element

a s th e activ e oi l recover y syste mprovide s reductio n i n toxicity , mobility , an d volum e o f contaminant s throug h th e extractio n an d treatmen t

o f separate-phas e PCB-lade n oil
. Becaus e thi s remedy wil l resul t i n hazardou s substance s remainin g on-site abov e level s that allo w fo r unlimite d us e an d unrestricte d exposur e (groundwate r and/o r lan d us e restriction s ar e necessary) , a revie w wil l b e conducte d ever y fiv e year s afte r

initiatio n o f

remedia l actio n t o ensure that th e remed y continue s t o provid e adequat e protectio n o f huma n healt

h an d th e environment
. F
. SPECIA L FINDING S Issuanc e o f

thi s RO D embodie s specifi c determination s mad e b y th e Regiona l Administrato r

o r hi s designe e pursuan t

t o CERCLA
. EP A determine d that i t wa s technicall y impracticabl e t o restor e groundwate r

beneat h alimite d are ao f

th e Site t o drinkin g wate r

qualit y withi n areasonabl e tim e frame
. Therefore , EP A waive d th e attainmen t o f chemical-specifi c ARAR s fo r thi s are ao f

th e Site
. Thes e chemical-specifi c ARAR s are either bein g me t no w o r are expecte d t o b e me t

shortl y throughou t

th e res t o f th e Site , an d therefor e wil l provid e sufficien t basi s fo r EP A t o make astatutor

y findin g o f

complianc e fo r th e chemical-specifi c ARAR s presente d i n thi s RO D Amendment fo r th e res t o f th e Site
. G
. RO D DAT A CERTIFICATIO N CHECKLIS T Th e followin g informatio n i s include d i n th e Decisio n Summary sectio n o f thi s Recor d o f

Decision
. Additiona l informatio n can b e foun di n th e Administrativ e Recor d fil e fo r thi s Site
. 1
. Chemical s o f

concern (COCs ) an d thei r respectiv e concentrations
. 2
. Cleanu p level s establishe d fo r COC s an d th e basi s fo r

th e levels
. 3
. Curren t

an d reasonabl y anticipate d futur e lan d assumption s an d curren t an d potential futur e beneficia l use s o f

groundwate r

use d i n th e RO D Amendment
.4
. Potential lan d an d groundwate r us e tha t wil l b e availabl e a

t th e Sit e a s aresul t

o f th e selecte d remedy
. 5
. Estimate d capital , operatio n an d maintenanc e (O&M) , an d tota l presen t wort h costs ; discount rate ; an d th e numbe r

o f year s ove r

whic h th e remed y cos t

estimate s are projected
. 6
. Ke y factor(s ) tha t le d t o selectin g th e remedy
. H
. AUTHORIZIN G SIGNATURE S
Thi s RO D Amendmen t

document s th e selecte d remedy fo r th e F
. O'Conno r

Superfun d Site , Operabl e Uni t 2
. Thi s remed y wa s selecte d b y USEP A wit h concurrenc e o f

th e Main e Departmen t

o f Environmental Protectio n (MEDEP)
. U.S
. Environmental Protectio n Agenc y

By : ichar d ^/Cavagnero/Actin g Directo r Officej aSit

e Remediatio n an d Restoratio n Regio n 1

### Tabl e o f Content s I SIT E NAME , LOCATION , DESCRIPTIO N AN D RATIONAL E FO R AMENDMEN T 1 I I SIT E HISTOR Y AN D ENFORCEMEN T ACTIVIT Y 3 II I COMMUNIT Y PARTICIPATIO N 5 I V SCOP E AN D ROL E O F OPERABL E UNI T 5 V DESCRIPTIO N O F CHANGE S T O TH E 198 9 REMED Y 6 DESCRIPTIO N O F TH E 198 9 REMED Y 6 CHANGE S T O TH E 198 9 REMED Y 8 V I SUMMAR Y O F SIT E CHARACTERISTIC S 9 VII SUMMARY O F SIT E RISK S 1 4 VII I TECHNICA L IMPRACTICABILIT Y DETERMINATIO N 1 5 I X COMPARATIV E ANALYSI S O F TH E ORIGINA L REMED Y AN D OU- 2 ALTERNATIVE S 2 9 X TH E SELECTED REMED Y , 3 6 X I STATUTOR Y DETERMINATION S 3 9 XI I DOCUMENTATIO N O F N O SIGNIFICAN T CHANGE S 4 3 XII I STAT

E ROLE 4 3

### Figures

1
. Sit e Locatio n Ma

p 2
. Sit e Pla n 3
. T I Zon e 4
. Restrictiv e Covenan t 5
. Designate dArea , 1994 , 1997 , an d200 2 6
. TW A I I 7
. Sit e Pla n with Cros s Section s 8
. Geologi c Cros s Sectio n A - A ' 9
. Geologi c Cros s Sectio n B - B ' 10
. Geologi c Cros s Sectio n C - C ' 11
. Uplan dMars h Stud y Are a 12
. Vertica l Residua l Oi l Distributio n A - A ' 13
. Vertica l Residua l Oi l Distributio n B - B ' 14
. Vertica l Residua l Oi l Distributio n C - C ' 15
. Inferre dBedroc k

Surfac e Elevatio n 16
. Inferre dGroundwate r Flo w 17
. Conceptua l Hydrogeologi c Mode l prio r t o SCR A 18
. Conceptua l Hydrogeologi c Mode l Afte r SCR A 

### Table s 1
. Compariso n betwee n 198 9 RO D an d200 2 RO D Amendmen t 2
. PC B Result s - TW A I I 3
. Chemical-Specifi c ARAR s fo r T I Waive r 4
. Gallon s o f

Oi l Recovere dFro mTW A I I Are aWell s 5
. Summary o f

Groundwate r

Monitorin g Result s Modifie dMetho d68 0 6
. Chemical-specifi c ARAR s 7
. Location-specifi c ARAR s 8
. Action-specifi c ARAR s 

### Appendice s Appendi x A - Responsivenes s Summar y Appendi x B - Administrativ e Recor dInde x Appendi x C - Stat e Concurrenc e Lette r Appendi x D - Reference s Cite d
i n

## F . O'CONNO RCOMPAN Y SUPERFUN D SIT E

RECOR D O F DECISIO N AMENDMEN T

OPERABL E UNI T 2 Septembe r 200 2
I . SIT E NAME , LOCATION , DESCRIPTIO N AN D RATIONAL E FO R AMENDMEN T SIT E NAME : Th e F
. O'Conno r Compan y Superfun dSite
. SIT E LOCATION : Th e F
. O'Conno r Superfun dSit

e i s locate di n Augusta , Main e (Figure 1)
. Th e twenty-thre e acr e O'Conno r site i s locate do n Easter n Avenue/Rout e 1 7 i n apredominatel y rura l neighborhood
. The twenty-thre e acr e site is locate dwithi n atwenty-eigh t acr e propert y owne db y Centra

l Main e Power

(CMP)
. Th e sit

e i s bordere db y woodland s an d asmal l poultry far mt o th e north , U.S
. Rout e 1 7 t o th e south , privat e propertie s an dresidence s t o th e west , an d th e wes t branc h o f Rigg s Broo k

an d it s associate dwetland s t o th e east . Publi c wate r ha s bee n provide dt o surroundin g residents , an di s availabl e fo r futur e development
. SIT E DESCRIPTION : Th e site wa s th e forme r locatio n o f

transforme r

salvagin g processes , whic h include dstrippin g an drecyclin g transformers , som e o f whic h containe dPCB

contaminate doil
. Th e F
. O'Conno r Compan y operate dfro mth e earl y 1950 s throug h th e lat e 1970s
. A s aresul t

o f release s o f

pol y chlorinate dbiphenyl s (PCBs) , lead , chlorinate d polyaromati c hydrocarbon s (cPAHs ) an dvolatil e organi c compound s (VOCs ) a t th e site , th e site wa s place do n th e Nationa l Prioritie s Lis t (NPL ) i n 1983
. Principa l feature s o n th e propert y prio r t o remedia l action s include da n Uplan dMarsh , tw o surfac e wate r impoundment s (Uppe r

an d Lowe r Lagoons) , thre e forme r

outdoo r transforme r

wor k area s (TWAs) , an dRigg s Broo k (Figur e 2)
. Upo n completio n o f

th e sourc e contro l remedia l actio n fo r Operabl e Uni t

1 (OU-1 ) th e lagoon s wer e restore da s wetland s an d th e are aencompassin g th e thre e TWA s wa s covere dwith clea n fill , re-graded , an dsuccessfull y vegetated
. I n 1996 , EP A separate dth e site int o thre e operabl e units
. A s note dabove , OU- 1 addresse dth e sourc e contro l remedia l action , OU- 2 addresse s managemen t o f migration , an d OU- 3 addresse s Rigg s Broo k

sedimen t an dbiota
. RATIONAL E FO RAMENDMENT : O n Septembe r 27 , 1989 , EPA , wit

h concurrenc e fro mth e Main e Departmen t o f Environmenta l Protectio n (Main e DEP ) an di n accordanc e wit h th e Comprehensiv e Environmenta l Response , Compensatio n an dLiability Ac t (CERCLA) , 4 2 US C § § 960 1 etseq., issue dth e Recor do f Decisio n (ROD ) fo r

th e O'Conno r

site
. Th e RO D selecte dth e remedial actio n fo r th e sit e an d establishe dth e targe t cleanu p goal s fo r

soil ,sediments , surfac e water , an dgroundwater
. Specifically , th e RO D require dth e remediatio n o f

tw o site components :

• Th e sourc e area s tha t wer e th e TWA s an d surroundin g soils , sediments , an d surfac e wate r i n th e tw o lagoon s (late r

designate da s OU-1) ; an d
• Sit e groundwate r

tha t wa s contaminate dwit h PCBs , benzene , an d 1,4-dichlorobenzene , (late r designate da s OU-2 ) an dth e Rigg s Broo k sedimen t an dbiot a(late r

designate da s OU-3)
. Thes e tw o components , describe dseparatel y i n th e 198 9 ROD , wer e calle dth e sourc e contro l (SC ) componen t

an dth e managemen t

o f migratio n (MOM) , respectively
. Base do n a n implementabilit y assessmen t conducte da s par t

o f th e remedia l desig n studie s i n th e earl y 1990s , EP A wrot e a n Explanatio n o f Significan t

Differenc e (ESD ) i n Jun e 199 4 t o revis e th e sourc e contro l componen t o f th e selecte dremedy
. Unde r th e ROD , th e remedia l actio n objectiv e fo r th e groundwate r

(OU-2 ) wa s t o reduc e potentia l futur e publi c health risk s fro mingestio n o f PCB , benzene , an d1,4-dichlorobenzene

contaminate dgroundwate r (ROD , pag e 17)
. Thi s objectiv e wa s t o b e achieve dusin g a groundwate r

extractio n systeman d an abov e groun dtreatmen t system . I n addition , institutional control s wer e t o b e temporaril y establishe dt o reduc e th e potentia l fo r exposur e t o contaminate d groundwate r

an dwer e t o remai n i n plac e unti l th e groundwate r remediatio n wa s complete d (ROD , pag e 45)
. Th e RO D furthe r specifie dtha t

on e o r mor e pum p test s woul db e conducte da s par t o f remedia l desig n s o tha t

a n appropriat e groundwate r extractio n syste mcoul db e constructed
. I n 1992 , pum p test s wer e carrie dou t a s par t o f th e remedia l design
. A s aresul t o f thi s effort , separat e phas e oi l wa s foun di n bedroc k wells , aconditio n no t

previousl y see n a t

th e site
. Consequently , MO M effort s focuse do n oi l recovery rathe r tha n groundwate r

extractio n an d treatmen t o f dissolve dcontaminants
. Thre e effort s a t activ e oi l recover y usin g vacuum-enhance d pumpin g were carrie dou t betwee n 199 6 an d 2001
. I n Apri l 2002 , CM P submitte da n evaluatio n o f th e technica l practicabilit y o f restorin g th e groundwate r a t th e O'Conno r

site t o drinkin g wate r qualit y withi n areasonabl e perio do f time
. Thi s evaluatio n conclude dtha t becaus e o f

th e geolog y an dhydrolog y a t

th e site , ther e wer e n o technologie s whic h coul daccomplis h thi s objective
. EP A an dMain e DE P agree dwith th e conclusio n o f thi s T I evaluation
. Thi s RO D Amendmen t

addresse s change s t o th e MO M componen t o f th e original 198 9 ROD , followin g th e conclusio n o f th e sourc e contro l remedia l actio n (SCRA ) fo r OU- 1 an dth e T I evaluation
. Thi s RO D amendmen t include s aT I waive r

fo r overburde n an dbedroc k groundwate r

i n asmal l portio n o f

th e twenty-thre e acr e sit e (Figur e 3)
. Thi s RO D Amendmen t als o addresse s mino r

changes/clarification s t o th e original 198 9 remed y fo r OU-1 , sourc e control , a s modifie db y th e 199 4 ES D an d 199 5 invocatio n o f th e contingenc y alternative , an d fo r OU-3 , Rigg s Brook
.Institutiona l control s i n th e for mo f aDeclaratio n o f

Restrictiv e Covenan t

(Restrictiv e Covenant ) hav e bee n implemente dfo r th e twenty-thre e acr e site t o provid e additiona l ris k reductio n b y controllin g exposur e t o site groundwate r (Figur e 4)
. Th e us e o f

groundwate r

beneat h th e site i s prohibite dwithou t

prio r writte n approva l b y Main e DEP
. Thi s RO D Amendmen t

an dth e document s whic h for mth e basi s fo r th e Amendmen t

ar e availabl e a t

th e followin g informatio n repositories :
EP A Record s Cente r 1 Congres s Street , Suit e 110 0 Boston , M A 02114-202 3 (617)918-145 9 Hours : 1 0 a.m.-noo n 2 p.m.- 5 p.m . Lithgo w Publi c Librar y 4 5 Winthro p Stree t Augusta , Main e 04330-554 2 (207)626-241 5 Hours : Tue s - Wed : noo n t o 8 p.m .

Thurs : 8 a.m . t o noo n Fri : 1 0 a.m . t o 6 p.m . Sat : 1 0 a.m . t o 3 p.m . Main e DE P Ra y Buildin g Hospita l Stree t

Augusta , Main e 0433 3 (207)287-265 1 Hours : (b y appointment ) Mo n - Thurs : 8:3 0 a. mt o 12:3 0 p.m .

12:3 0 p.m . t o 4:3 0 p.m . Friday : 8:3 0 a.m . t o 12:3 0 p.m . 

### II . SIT E HISTOR Y AN D ENFORCEMEN T ACTIVITIE S Detail s o f th e earlie r

sit e histor y an denforcemen t activitie s ar e presente di n th e 198 9 ROD
. Th e followin g i s a n updat e t o th e site histor y an denforcemen t activitie s whic h hav e occurre dsinc e issuanc e o f

th e ROD
. I n Septembe r

1989 , EP A issue daRO D fo r th e O'Conno r

site
. Th e bar n structur e wa s t o b edecontaminated , demolished , an dthe n dispose do f offsit e a t appropriat e facilities , standin g wate r an dsediment s i n th e tw o lagoon s wer e t o b e removed , soil s contaminate dwith PCBs , PAHs , an d lea dwer e t o b e excavate dan d treate dusin g solven t extraction , contaminate dgroundwate r wa s t o b e pumpe dfro mth e soil s an dbedrock , treated , an dthe n discharged , an dsediment s an dfis h i n Rigg s Broo k

wer e t o b e sample dfo r

te n years . Performanc e standard s fo r soi l an dsedimen t

wer e se t a t 1 pp mPCBs , 1 pp mcPAHs , an d24 8 pp mlead
. Performanc e standard s fo r groundwate r

wer e se t a t 0. 5 pp b PCBs , 5 pp b benzene , an d 2 7 pp b 1,4-dichlorobenzene
. Performanc e standard s fo r th e standin g wate r

i n th e lagoon s wer e se t a t 0.06 5 pp b PCBs , 1.9 4 pp b lead , an d8 7 pp b aluminum
. Performanc e standard s fo r Rigg s Broo k sedimen t an dbiot awer e se t

a t 1 pp mPCB s an d2 pp mPCBs , respectively
. I n Septembe r

1991 , aConsen t

Decre e betwee n EP A an d CM P wa s approve db y th e U.S
. Distric t Cour t o f Maine
. Wit h thi s Consen t Decree , CM P agree dt o perfor man dfun dth e remed y selecte di n th e 198 9 ROD
. On e o f th e component s o f

th e remed y wa s institutiona l control s o n site groundwater
. I t

wa s EPA' s inten t

tha t thos e institutiona l control s woul dremai n i n effec t unti l remediatio n o f

th e groundwate r

wa s complete
. Th e Consen t

Decre e allowe dfo r

a n evaluatio n o f

th e solven t

extractio n technolog y selecte dfo r th e soils
. Followin g thi s evaluation , EP A an dMain e DE P agree dtha t thi s technolog y fo r

th e sit e soil s woul dno t

b e abl e t o attai n th e clean-u p goals
. A s aresult , i n Jun e 199 4 EP A issue da n Explanatio n o f

Significan t

Difference s (ESD ) whic h modifie dth e soi l remedy
. Soil s containin g mor e tha n te n part s pe r

millio n (ppm ) PCB s o r

PAH s o r 24 8 pp mlea dwoul db e treate dusin g solven t extractio n technology , an d soil s containin g betwee n on e t o te n pp mPCB s o r PAH s woul db e consolidate dint o on e are aonsit e an dthe n covere dwith clea n fil l brough t i n fro m offsite
. Thi s designate dare ai s show n o n Figur e 4
. I n Octobe r 1995 , EP A invoke dth e contingenc y remed y se t

fort h i n th e 199 4 ESD
. Thi s ES D als o include dacontingenc y tha t allowe dfo r

th e offsit e disposa l o f

soi l an dsedimen t

wit h greate r

tha n te n pp mPCB s an dcPAH s withou t firs t requirin g on-sit e solven t

extractio n treatment . A t th e same tim e a s th e ESD , aDeclaratio n o f Restrictiv e Covenan t

wa s execute dbetwee n CM P an dMain e DEP
. Thi s Restrictiv e Covenan t i s currentl y i n place
. O n Apri l 25 , 1996 , EP A agree dt o dela y completio n o f th e MO M design , an d t o separat e th e Rigg s Broo k

componen t

fro mth e MO M a s athir doperabl e uni t (OU-3)
. Thi s wa s don e s o tha t th e samplin g an danalysi s fo r Rigg s Brook , th e remedia l actio n require db y th e ROD , coul d begin prio r

t o th e completio n o f

th e MO M design
. Th e S C componen t o f th e selecte dremedy wa s designate da s OU- 1 an dth e MO M componen t wa s designate da s OU-2
. Phas e I o f th e sourc e contro l remedia l actio n wa s complete di n 1996
. Thi s include dsite preparation , an dth e decontamination , demolition , an doff-sit e disposa l o f th e barn
. Phas e I I activities , includin g th e off-sit e disposal o f contaminate dsoi l an d sedimen t an d th e coverin g o f th e designate darea , wer e complete di n 1997
.

### III . COMMUNIT Y PARTICIPATIO N

Thi s RO D amendmen t

meet s th e criteri afo r

communit y involvemen t

specifie di n Section s 300.4 3 5(c)(2)(ii)(A ) through(H ) o f th e NCP
. I n Jun e 200 2 EP A publishe daPropose d Pla n t o amen dth e 198 9 ROD
. Th e Propose dPla n fo r OU- 2 calle dfo r

institutiona l control s t o preven t exposur e t o contaminate dgroundwater , activ e recover y o f

separat e phas e oi l a s lon g a s practicable , designation o f asmal l portio n o f

th e site a s aT I zon e wher e state an dfedera l groundwate r standard s woul db e waived , long-ter mmonitoring , an dfive-year

reviews
. Th e amende dcleanu p pla n wa s recommende dbecaus e EP A believe di t offere dth e bes t

balanc e amon g th e nin e criteri arequire dt o b e reviewe dunde r th e NCP , includin g th e protectio n o f huma n healt h an dth e environmen t an dth e reductio n o f

contaminatio n throug h treatment . EP A hel dapubli c informatio n meetin g o n Jun e 24 , 200 2 an daforma l publi c hearin g o n Jul y 9 , 2002
. Th e publi c commen t perio dra n fro mJun e 1 9 t o Jul y 19 , 2002
. Al l forma l comment s receive do n th e Jun e 200 2 Propose dPla n ar e summarize dan dresponde dt o i n th e Responsivenes s Summary , whic h i s include da s Appendi x A o f thi s RO D Amendment
. I n addition , comment s receive ddurin g th e publi c informatio n meetin g ar e summarize di n th e Responsivenes s Summary
. Pursuan t t o Sectio n 300.825(c ) o f

th e NCP , EP A update dth e Administrativ e Recor di n Jun e 200 2 t o ad dth e document s whic h EP A relie do n t o for mth e basi s fo r th e decisio n t o modif

y th e respons e actio n fo r

OU- 2 a t th e O'Conno r

site
. Se e Appendi x B fo r

th e Administrativ e Index
. 

### IV . SCOP E AND ROL E O F OPERABL E UNI T Th e O'Conno r

sit e wa s divide dint o thre e operabl e unit s i n 1996 , seve n year s afte r th e RO D wa s signed
. Th e thre e unit s ar e a s note dabove , sourc e contro l OU-1 , groundwate r OU-2 , an dRigg s Broo k OU-3
. Remedia l actio n fo r OU- 1 wa s complete di n 199 7 an dEPA , with concurrenc e fro mMain e DEP , signe dof f o n thi s componen t

with th e approva l o f

th e Septembe r

199 8 Sourc e Contro l Remedia

l Actio n repor

t (Woodar d & Curran , 1998)
. Th e limite dactio n require d fo r Rigg s Broo k

b y th e 198 9 RO D continue s t o b e carrie dout . Thi s RO D amendmen t

pertain s t o OU-2 , althoug h a s describe dbelow , aspect s o f OU- 1 an d OU

3 wer e discusse ddurin g th e developmen t o f th e T I evaluatio n an di t

wa s mutuall y agree db y al l partie s (EPA , Main e DEP , an d CMP ) t o addres s thes e aspect s a t th e tim e o f

thi s RO D amendment
. Fo r OU-1 , th e 199 4 ES D establishe dtha t aportio n o f

th e site woul db e use dt o consolidat e soi l an dsedimen t

containin g level s betwee n on e an dte n pp mo f PCB s and/o r

cPAHs
. Thi s designate dare awoul db e covere dwit h twelv e inche s o f clea n soil , an da n operatio n an d

### maintenanc e pla n woul db e develope dt o ensur e th e integrit y o f thi s component . A s conceptuall y presente di n th e BSD , th e designate dare awa s thre e t o fou r acre s bounde do n fiv e side s with rounde dturnin g points
. A s th e actua l excavatio n fo r th e sourc e contro l remedia l actio n evolved , th e boundar y o f

th e designate dare abecam e a25-side dpolygon
. A s agree damon g al l parties , thi s create dadifficul t

situatio n fo r

anyon e inspectin g th e site t o kno w wher e th e boundar y was . EP A ha s determine dtha t

th e followin g change s t o th e designate dare ashal l b e incorporate dint o thi s RO D Amendment : Th e designate dare awil l b e surveyed , th e boundarie s simplifie dt o th e 12-side dshap e show n i n Figur e 4 , an dpermanen t marker s place da t

th e turnin g points
. Operatio n an dmaintenanc e fo r OU- 1 shal l includ e th e followin g changes :

• A t fiv e yea r interval s coinciden t

wit h eac h Fiv e Year

Review , composit e sample s fro m te n location s randoml y selecte dfro mth e SCRA gri dnode s wil l b e collecte dfro mfou r t o eigh t inche s belo w the surfac e andanalyze dfor PCBs
. •I t i s no t necessary t o resampl e fo r

PAH s base do n th e extensiv e dat acollecte ddurin g th e SCRA
. I n al l other

aspects , operatio n an dmaintenanc e shall remai n a s specifie di n th e 1994 ESD
. Regardin g OU-3 , th e 198 9 RO D se t astandar do f

1 pp mPCB s an d cPAH s i n th e Rigg s Broo k sediment s base di n par t

o n inpu t fro mU S Fis h & Wildlif

e Servic e (USFWS)
. However , i t wa s agree db y al l parties , includin g USFWS , that th e negativ e short-ter

mimpact s t o th e wetland s ecolog y outweighe dth e remova l o f sediment s t o tha t

level
. A trigge r

leve l o f 5 pp mPCB s fo r furthe r actio n wa s therefor e establishe dA s state di n th e 198 9 ROD , "i f an increas e i n th e curren t PC B sedimen t

level s occur s abov e th e 5 pp mthreshol dand/o r th e fis h tissu e sample s ar e foun dt o b e greate r

than 2 ppm , the n amor e rigorou s samplin g effor t o f suc h contaminatio n wil l b e conducte dt o determin e th e nee dfo r and/o r exten t o f furthe r remedia l action s t o b e undertake n withi n Rigg s Brook , i f

any. " (ROD , pag e 47 ) Thi s i n fac t occurre di n 199 7 whe n soi l an d sedimen t abov e 5 pp mPCB s wer e remove dsimultaneousl y with th e ongoin g SCRA , an dagai n i n 199 9 an d2000 whe n additiona l sample s wer e collected
. Th e mos t recen t dat a(2001 ) showe d tha t 3 5 o f 3 6 sampl e location s wer e belo w th e 5 pp mtrigge r level , an dth e majorit y o f

th e sample s wer e non-detect
. Main e DE P requeste dtha t thi s RO D amendmen t

restat e tha t

th e targe t cleanu p goa l fo r

Rigg s Broo k

sedimen t remain s a t

1 pp mPCB s an dcPAHs
. Th e result s fro mtw o biot asamplin g event s (199 7 an d2000) , demonstrat e tha t concentration s o f PCB s detecte di n biot ahav e no t exceede dth e RO D targe t

leve l o f 2 ppm , an di n fac t

hav e al l bee n belo w 1 ppm . V . DESCRIPTIO N O F CHANGE S T O TH E 198 9 RO D 1 . DESCRIPTIO N O F 198 9 REMED YTh e remedy selecte db y th e 198 9 RO D wa s develope dt o satisf y th e followin g fiv e remedia l actio n objective s (RAO) : •reduc e publi c health an denvironmenta l risk s fro mdirec t contac t with contaminate d soils ,

• reduc e publi c health risk s fro minhalation s o f PC B vapors ,

• reduc e futur e health risk s fro mingestio n o f contaminate dgroundwate r foun do n th e site , •reduc e publi c health risk s fro mingestio n o f PCB-contaminate dfis h fro mRigg s Brook , an d •reduc e risk s t o aquati c an dterrestria l wildlif e fro mexposur e t o contaminate dsediments
. Th e firs t tw o RA O wer e achieve dwith th e completio n o f th e sourc e contro l remedia l actio n i n 1997
. Th e soi l clean-u p began i n 199 6 with th e cleaning , demolition , an doff-sit e disposa l o f th e bar n situate d alon g Rout e 17 , an d other sit e preparatio n activities
. Th e secon d phas e o f th e soil cleanu p wa s complete di n 1997
. Thes e activitie s include dth e collectio n an doff-sit e disposa l o f lagoo n water , an dth e excavatio n an doff-sit e disposa l o f nearl y 20,00 0 ton s o f

soil
. A n additiona l 300 0 t o 400 0 ton s o f soil s wit h PCB s o r

PAH s concentration s betwee n 1 an d1 0 pp m wer e place dwithi n th e designate dare aonsite
. Thi s are awa s the n covere dwith aminimu mo f on e foo t o f clea n fil l brough t

i n fro moffsite
. Th e entir e site wa s the n graded
. Drainag e pattern s an dth e on-sit e wetland s wer e restored
. A n additiona l 0. 4 acr e o f wetland s wa s create di n th e forme r lagoon s a s replacemen t

fo r wetland s los t

a s aresul t

o f th e clean-u p activities
. Laborator y test s o f

sample s collecte dfro mth e botto man d perimete r o f th e excavatio n demonstrate dthat

th e excavatio n ha dremove dth e contaminate dsoi l t o th e performanc e standard s se t

i n th e 199 4 ESD
. Combinedwith th e operatio n an dmaintenanc e o f th e soi l cove r an dmonitorin g points , th e ris k t o publi c healt h fro mcontac t with th e soi l an dinhalatio n o f vapor s ar e addressed
. A mor e complet e descriptio n o f th e sourc e contro l activitie s ca n b e foun di n th e Septembe r 199 8 SCR A report . Th e las t tw o RA O hav e bee n achieve dthroug h th e monitorin g o f sediments , analysi s offis h tissu e fo r PC B accumulation , an dth e 199 7 excavatio n o f sedimen t i n thre e separat e location s wher e concentration s exceede dth e trigge r level
. A mor e complet e descriptio n o f th e wetland s restoration , ho t spo t excavations , an d Rigg s Broo k monitorin g ca n b e foun di n th e Wetland s Constructio n Monitorin g report s fo r 1997-200 0 (Th eTh e ground-wate r remed y selecte d i n th e 198 9 RO D include d pumpin g wells , atreatmen t system , an d anetwor

k o f monitorin g well s t o trac k contaminatio n levels
. Th e inten t wa s t o pum p an d the n treat groundwate r

whic h containe d dissolve d PCB s an d VOC s an d thereb y restor e th e qualit y o f th e groundwater
. I n 1992 , abedroc k

pum p tes t

wa s performed
. Durin g th e tes t aseparat e phas e oi l laye r u p t o thre e an d hal f

fee t thic k wa s pulle d int o thre e bedroc k well s i n Transformer

Wor k Are aI I (TW

A I I - se e Figur e 2)
. Thi s wa s th e firs t tim e tha t separat e phas e oi l ha d bee n detecte d i n th e bedrock
. A s aresult , additiona l monitorin g well s wer e installe d t o determin e ho w far th e oi l extended
. N o additiona l oi l wa s discovere d an d i t wa s conclude d tha t

th e exten t

o f fre e oi l i n th e bedroc k wa s limited
. Th e nex t stag e o f th e groundwate r

remed y too k

plac e i n 1996-97
. Abou t 2 8 gallon s o f

PCB

lade n oi l wer e pumpe d ou t o f th e shallo w bedroc k

durin g thi s period
. Th e pumpin g syste mwa s shu t dow n whe n oi l wa s n o longe r recovered
. Fro m199 7 t o 2001 , CM P continue d t o recove r oi l fro mwell s b y usin g absorben t material s t o remov e an y oi l whic h accumulate d i n th e wells
. A littl e unde r seve n gallon s o f

PCB-lade n oi l wa s recovere d durin g thi s perio d fro mwell s i n TW A II
. A thir d effor t

at oi l recover

y too k plac e fro mAugus t

t o October

2001
. Fiv e well s i n TW A I I wer e alternatel y pumped
. Jus t unde r 2 0 gallon s o f

PCB-lade n oi l wer e recovered
. Thi s pumpin g effor t was als o shu t

dow n whe n oil was no longe r pulle dint o the system . 2 . CHANGE S T O TH E 198 9 REMED Y I n Apri l 2002 , CM P submitte d a n evaluatio n o f th e technica l practicabilit y o f restorin g th e groundwate r

a t th e O'Conno r

site t o drinkin g wate r

qualit y withi n areasonabl e perio d o f time
. Thi s evaluatio n conclude d that becaus e o f

th e geolog y an d hydrolog y at th e site , ther e wer e n o technologie s whic h coul d accomplis h thi s objectiv e (th e thir d RA O i n th e 198 9 ROD)
. Th e evaluatio n wa s resubmitte d i n Jun e 200 2 followin g EP A an d Main e DE P comments . EPA , with concurrenc e fro mMain e DEP , approve d th e Jun e 200 2 report . Thi s RO D amendmen t

fo r OU- 2 select s aremed y consistin g o f institutiona l controls , activ e oi l recovery , long-ter

mmonitorin g o f

groundwater , an d five-yea r reviews
. Thi s RO D amendmen t recognize s th e technica l impracticabilit y o f achievin g th e thir d RA O (reductio n o f futur e healt

h risk s fro mingestio n o f

contaminate d groundwate r foun do n th e site ) withi n areasonabl e tim e frame
. I t establishe s atechnica l impracticabilit y zon e fo r aportio n o f

th e sit e wher e stat e an d federa l drinkin g wate r

standard s ar e waived
. A compariso n o f

th e origina l 198 9 remed y fo r groundwate r

an d th e modifie dremed y fo r OU- 2 i s provide d i n Tabl e 1
.

### VI . SUMMAR Y O F SIT E CHARACTERISTIC S

Thi s sectio n o f

th e repor t provide s asummary o f

th e groundwate r

dat aat th e site , startin g fro m th e upgradien t

positio n a t

MW-101A/B , throug h th e uplan d mars h area , th e T I zon e (TW A I I an d VER) , th e are adowngradien t o f th e T I zon e (MO M wells) , an d t o th e groundwate r discharg e are arepresente d b y MW-106A/B
. Se e figur e 3 fo r monitorin g wel l locations
. Groundwate r

cleanu p standard s establishe d i n th e RO D includ e tota l PCB s at 0. 5 Mg/L , benzen e at 5 //g/L an d1,4-dichlorobenzen e at 2 7 //g/L
. I n addition , base d o n th e ARAR s revie w discusse di n Sectio n VIII
. 1 o f thi s RO D amendment , fiv e othe r VOC s wer e identifie dwhic h sinc e th e 198 9 RO D hav e ha dARAR s establishe d an dfo r whic h aT I Waiver

wil l apply
. Thes e ARAR s includ e Maximu mContaminant s Level s (MCLs ) an dMain e Maximu mExposur e Guideline s (MEGs ) fo r

eigh t VOC s an dPCBs
. Fo r

eac h o f thes e fiv e compounds , th e ME G i s eithe r th e sam e o r

lowe r tha n th e respectiv e MCL
. 1
. Upgradien t

Locatio n Monitorin g well s MW-101 A an d MW-101 B ar e upgradien t o f th e TWAs , locate d nea

r th e wester n boundar y o f

th e site i n an uplan d area . Thes e well s wer e installe d durin g th e R I t o provid e a n indicatio n o f

regiona l wate r

qualit y a s groundwate r

flow s easterl y beneat h th e site towar d Rigg s Brook
. MW-10 1 A monitor s groundwate r i n th e overburde n soil an d MW-101 B monitor s th e bedroc k

groundwater
. Annua l samplin g o f thes e well s sinc e 199 6 ha s no t detecte d an y PCB s o r

VOCs
. 2
. Uplan d Mars h Are a A n investigatio n t o determin e th e presenc e an d extent o f oi l i n th e desiccate d cla

y i n th e Uplan d Mars h are awa s complete d i n 199 8 an d 1999
. Th e inten t o f th e investigatio n wa s t o determin e th e likel y sourc e o f

oi l that accumulate d i n awetlan d piezomete r (UM-1 ) i n th e Uplan d Mars h an d t o determin e th e distributio n o f an y additiona l residua l oi l i n tha t area . Th e investigatio n involve d completin g 1 9 GeoProb e boring s wit h continuou s samplin g (figur e 11)
. Th e sample s were retrieve d an dlogge d wit

h respec t t o th e soi l typ e an dteste d fo r oil
. Base d o n th e GeoProb e borings , th e soi l stratigraph y an d extent o f residual oi l wa s determine d i n th e Uplan d Marsh
. Th e brow n desiccate d cla

y ha s ablock

y fracture structur e where oi l reside s i n bot h vertical an d horizonta l fractures
. A sligh t to moderat e oil shee n was foun dcomin g fro mdiscret e fractures in th e clay
. Al l oi l foun d reside d a s aresidual coatin g o n th e cla y fracture s walls
. Th e result s o f th e analysi s indicate d tha t

PCB s i n soil s aroun d an dincludin g th e fracture s wer e foun dt o rang e fro m non-detec t

(ND ) t o 1000 /^g/k g (i.e
. fro mN D t o 1 ppm)
. Th e RO D targe t leve l fo r PCB s i n th e overal l mas s o f

soi l outsid e th e Sourc e Contro l Designate d Area , specifie ddurin g th e sourc e contro l remedia l action , i s 1 ppm . Therefore , concentration s o f PCB s foun di n thes e sample s di d no t excee d th e targe t

level
.Th e dat acollecte dsugges t that th e oil , whic h originate dfro mTW A I I durin g transforme r salvagin g operations , ra n of f th e lan dsurfac e towar dth e Uplan dMars h an dinfiltrate dint o th e uppe r brow n desiccate dclay durin g th e tim e that th e sit e wa s active
. Unabl e t o mov e downward, both fro mth e underlyin g sof t clay an dth e lac k

o f th e entranc e pressure s necessary fo r a n immiscibl e liqui dt o overcom e surfac e tensio n forces , th e oi l ha s remaine drelativel y immobil e i n th e uppe r clay fractures
. I n th e norther n portio n o f th e stud y area , wher e th e desiccate dclay i s i n direc t contac t with th e till , ther e i s n o evidenc e tha t suggest s th e oi l ha s migrate dalon g th e till/bedroc k

interface
. I t

appear s tha t

th e oi l ha s migrate dverticall y downwar dint o th e clay reachin g a n equilibriu mbetwee n surfac e tensio n force s impose db y th e clay fractur e capillaries , th e density consideration s o f a n immiscibl e liqui di n asaturate dmediu man dauni t infiltratio n gradient
. Very littl e horizonta l movemen t ha s occurre da t

dept h becaus e th e horizonta l gradien t acros s th e site i s no t

grea t enoug h t o overcom e th e resistin g force s describe dabove
. I t i s believe dtha t

th e oi l foun di n th e are asurroundin g UM- 1 i s residua l i n natur e an dwithou t a significan t gradien t doe s no t migrate
. 3
. T I Zon e Well s A
. PCB s Dat aEvaluatio n Th e groundwate r

fro mth e fiv e well s i n th e TW A I I Are awa s no t sample di n 199 6 o r

199 7 becaus e oi l wa s foun di n thes e well s an di t wa s agree dtha t

th e well s woul dno t

giv e representativ e result s o f

th e dissolve dconcentrations
. Afte r 1997 , th e fou r

groundwate r observatio n well s (OW-202B , OW-204B , OW-301B , an d OW-302B ) an d th e VE Rextractio n wel l (RW-101 ) wer e sample dquarterl y fo r PCB s an dth e seve n targe t VO C compound s i f

oi l wa s no t detecte di n th e wells
. However , th e result s o f TW A I I wel l samplin g indicate dawid e variatio n i n contaminan t

concentrations
. I t

wa s determine dtha t

thi s wa s du e t o th e presenc e o f emulsifie doi l i n th e wel l wate r an dassociate dVOC s i n a n oi l emulsio n whic h wa s no t presen t sufficientl y t o b e measure db y th e interfac e probe , bu t wa s visuall y detecte di n th e sample s an d purg e water . Th e sample s take n wer e no t representativ e o f

actua l dissolve dcontaminant s i n th e groundwater
. Tabl e 2 give s th e result s o f PC B dat acollecte dfro mTW A I I fro m199 8 t o 2001
. Th e result s i n bol dprin t ar e abov e th e RO D cleanu p goal fo r PCB s o f 0. 5 //g/ L an drepresen t

th e impac t

o f oi l emulsion s i n th e samples , no t dissolve dPCB s i n groundwater
. Tabl e 2 indicate s tha t

tw o wells , OW-301 B an dOW-302 B continuall y ha dPCB s detecte da t greate r concentration s tha n th e RO D cleanu p standar do f 0. 5 /ug/L
. Thes e ar e th e sam e tw o well s that ha dgroundwate r

tha t regularl y exceede dth e VO C cleanu p standards
. Separat e phas e oi l ha s bee n observe di n thre e othe r TW A I I wells , OW-202B , OW-204B , an d th e VE Rextractio n well , RW-101 , o n a n ongoin g basi s sinc e Septembe r 1998
. PCB s wer e detecte dat

8,90 0 //g/

L at OW-302 B i n Decembe r

1998
. I n Apri l 2001 , th e concentratio n o f

PCB s at OW-302 B wa s 4 4 //g/L
. Th e PC B result s at OW-302 B hav e range d 1 0fro m2. 5 t o 8,90 0 //g/L
. Separat e phas e oi l ha s als o bee n observe d i n thi s wel l ove r time
. I n Novembe r

2001 , 1.2 5 fee t

o f oi l wa s measured
. Th e increase d thicknes s o f oi l i n OW-302 B i n Novembe r

200 1 i s mos t

likel y th e resul t

o f th e operatio n o f

th e VE Rsyste m(Phas e III ) i n Septembe r

200 1 an dextremel y lo w wate r tabl e elevation
. Th e observe d oi l i s likel y responsibl e fo r th e PC B concentration s detecte d a t OW-302B
. Th e histori c PC B result s repor t ca n b e foun di n th e Jun e 200 2 Technica l Impracticabilit y Evaluatio n Report , Appendi x C
. B
. VO C Dat aEvaluatio n Th e RO D cleanu p goal s ar e 5 //g/ L fo r benzen e an d2 7 //g/

L fo r 1,4-dichlorobenzene
. Additiona l ARAR s fo r

whic h aT I waive r

wil l appl y ar e liste d i n Tabl e 3
. Benzen e concentration s fro mth e groundwate r i n TW A I I well s range d fro m0 t o 8. 0 //g/L betwee n 199 8 an d2001
. Benzen e concentration s fro mOW-302 B wer e regularl y (6/98 , 9/98 , 12/98 , an d6/99 ) detecte d at 6. 0 //g/L , whic h i s 1 //g/L ove r th e MCL/MEG
. Th e las t samplin g event at thi s wel l detecte d benzen e at 8. 0 //g/ L i n Apri l 2001
. N o other TW A I I well s exhibite d a n exceedanc e o f

th e benzen e MCL/MEG
. Th e Main e ME G fo r

1 , 4-dichlorobenzen e (2 7 //g/L ) wa s regularl y exceede d at bot h OW-301 B an d OW-302 B betwee n 199 8 an d 2001
. Th e 1,4-dichlorobenzen e result s a t thes e tw o well s range d fro m89-72 0 //g/L
. Severa l othe r targe t VOC s wer e als o detecte d i n OW-301 B an dOW

302B. Th e tw o TW A I I well s wit h th e exceedanc e fo r VOC s ar e locate d clos e togethe r i n th e cente r o f TW A II
. Thes e tw o well s ar e locate d immediatel y adjacen t t o wel l OW-202B , whic h wa s use d fo r

th e 199 2 pumpin g tes t

an d i s responsibl e fo r

drawin g oi l int o th e bedroc k aquifer
. 1,4-dichlorobenzen e wa s als o detecte d i n lo w concentration s (belo w th e MEG ) i n observatio n well s OW-204 B (u p t o 0. 7 //g/L) , OW-202 B (u p t o 2 0 //g/L ) an d th e VE Rwel l RW-10 1 (u p t o 13//g/L)
. Th e T I evaluatio n o f

ARAR s identifie dMCLs/MEG s fo r fiv e othe r VOC s whic h hav e bee n detecte d i n th e groundwater
. I n addition , anothe r VOC , 1,2,3-trichlorobenzene , ha s bee n detecte d bu t

doe s no t hav e eithe r

a n MC L o r

MEG
. Thre e o f

thes e VOCs , chlorobenzene , 1,2

- dichlorobenzene , an d1,2,4-trichlorobenzene , wer e detecte d i n th e R I sampling
. Fiv e o f thes e other VOC s wer e detecte d i n th e TW A I I well s betwee n 199 8 an d 2001
. Concentration s o f chlorobenzen e range d fro m4 t o 24 0 //g/ L a t OW-301 B an d OW-302B , exceedin g th e Main e ME G o f 4 7 //g/L
. 1,2-Dichlorobenzen e an d 1,3-Dichlorobenzen e (M E ME G o f 8 5 //g/L ) wer e detecte d a t

OW-301 B an d OW-302 B a t concentration s rangin g fro m3-21 0 //g/ L an d 2-16 0 //g/L , respectively
. Thes e compound s wer e detecte d at relativel y lo w concentration s at th e othe r TW A I I wells
. Concentration s o f

1,2,4-trichlorobenzen e hav e bee n detecte d abov e th e Main e ME G o f 7 0 //g/ L a t OW-202 B an d OW-301 B a t concentration s rangin g fro m3-61 0 //g/L , an d rangin g a s hig h a s

1 1320 0 //g/L at OW-302B
. Th e histori c VO C result s ar e include di n th e Jun e 200 2 Technica l Impracticabilit y Evaluatio n Report , Appendi x D
. C
. VE ROperatio n Th e vacuum-enhance drecover y syste m(VER ) ha s bee n operate dfo r thre e period s o f

tim e followin g post-RO D pilo t

tests . Th e tota l amoun t

o f oi l recovere dfro mth e fiv e TW A I I well s sinc e thei r installatio n i s approximatel y 85. 2 gallons
. A summary o f oi l recovere d fro mth e TW A I I well s i s presente di n Tabl e 4
. Fiv e well s (OW-202B , OW-204B , OW-301B , OW-302 B an d RW-101 ) i n th e forme r TWA I I Are aan dpiezomete r

UM- 1 hav e bee n monitore dfo r groundwate r

elevatio n an doi l thicknes s o n amonthl y basi s sinc e 1998
. Wheneve r oi l wa s detecte di n awell , a n absorben t soc k wa s lowere d int o th e wel l t o adsorb an dremov e th e oil
. Sinc e th e las t oi l recovery effor t

i n th e fal l 2001 , 1 .2 5 fee t o f oi l accumulate di n OW-302 B an dwa s remove dusin g absorben t socks
. 4
. Managemen t

o f Migratio n A
. PC B Dat aEvaluatio n Include di n thi s sectio n i s adiscussio n o f thos e well s whic h ar e locate di n th e are adowngradien t o f th e T I zone . Asid e fro mafe w initia l samplin g event s (prio r

t o 1994 ) wher e elevate d concentration s o f

PCB s ma y hav e resulte dfro mPC B adsorptio n ont o soi l particle s i n th e groundwate r

samples , concentration s o f PCB s i n groundwate r

sample s collecte dfro mwell s outsid e o f th e TW A I I Are ahav e no t exceede dth e 198 9 RO D targe t cleanu p leve l fo r

PCB s (0. 5
I n Marc h 1 999 , th e groundwate r sample s fro msi x MO M monitorin g well s wer e analyze dusin g USEP A Modifie dMetho d68 0 fo r tota l homologu e PCBs
. Th e result s o f th e 68 0 analyse s ar e summarize di n Tabl e 5
. Concentration s o f PCB s wer e belo w th e RO D targe t cleanu p level
. A s state di n Sectio n VIII
. 1. , curren t ARAR s hav e bee n reviewe dan dconcentration s o f PCB s at several well s ar e at

o r slightl y abov e th e 199 2 Main e ME G o f 0.0 5 //g/L
. Futur e analysi s o f groundwate r

fro mMO M well s wil l b e don e usin g alower detectio n limit , t o determin e i f groundwate r

outsid e th e T I Zon e (se e Figur e 3 ) meet s th e 199 2 Main e ME G o f 0.0 5 /ug/L
. B
. VO C Dat aEvaluatio n Thi s sectio n wil l discus s th e VO C result s compare dt o federa l MCL s an d Main e MEG s (se e Figur e 2 fo r

wel l locations)
. Th e VO C result s fro mMW-104 B an d OW-201 B indicat e th e presenc e o f lo w t o moderat e level s 1 2o f

VOC s i n th e bedroc k

a t thes e locations
. Th e ME G fo r 1,4-dichlorobenzen e (2 7 /^g/L ) ha s bee n exceede da t

bot h wells
. Prio r

t o Jun e 1998 , th e concentratio n o f 1,4-dichlorobenzen e range dfro m26-9 1 //g/L i n MW-104 B an d25-5 5 //g/L i n MW-201B
. Sinc e then , th e concentratio n o f

1,4-dichlorobenzen e ha s bee n consistentl y betwee n 20-4 0 //g/ L i n MW-104 B an d20-3 6 //g/

L i n MW-201B
. Thes e ar e reduction s an di f thes e decreasin g trend s continue , th e concentration s o f

1,4-dichlorobenzen e at

OW-201 B an d MW-104 B ar e expecte dt o b e consistentl y belo w th e ME G i n th e near future
. Fo r th e VOC s wit h post-RO D MCLs/MEGs , 1,2-dichlorobenzen e exceede dth e ME G o f 8 5 //g/ 1 at thes e well s prio r

t o 1997 , bu t

ha s bee n belo w th e ME G since , an d 1,3-dichlorobenzen e ha s no t exceede dit s ME G o f

8 5 //g/L
. Concentration s o f benzene , chlorobenzene , 1,2,3

- trichlorobenzen e an d 1,2,4-trichlorobenzen e hav e bee n ver y lo w t o moderat e an d hav e no t exceede dMEG s a t

MW-104 B an dOW-201B , excep t fo r 1,2,4-trichlorobenzen e prio r t o 1995
. Result s o f analysi s o f

groundwate r

fro mmonitorin g well s MW-507 A an d MW-508B , place di n th e bedroc k

trough , indicat e th e presenc e o f fiv e VOC s i n MW-507 A an dfou r VOC s i n MW

508B
. Th e relativ e VO C concentration s ar e generall y highe r i n th e shallo w groundwate r monitoredb y MW-507A
. Monitorin g wel l MW-507 A i s locate di n abedroc k troug h an d screene di n th e till/bedroc k surfac e specificall y t o monito r VO C concentration s i n th e primar y migratio n pathwa y wher e contaminate dgroundwate r fro mth e forme r

TW A sourc e area s flow s slowl y i n asoutheasterl y direction
. Monitorin g wel l MW-508 B wa s installe dint o th e bedroc k t o monito r VO C concentration s i n th e secondar y bedroc k migratio n pathway
. Th e concentration s o f 1,4-dichlorobenzen e i n MW-507 A range dfro mND-8 1 //g/ L i n th e pas t

fiv e years . Th e concentration s o f

1,4-dichlorobenzen e a

t MW-503 , downgradien t

o f MW-507A , are muc h lowe r (ND- 8 //g/L ) tha n a

t MW-507A
. Th e sam

e decreas e i n concentration s wa s observe dfo r 1,2-dichlorobenzen e an d1,3-dichlorobenzene
. Thi s reductio n i n VO C concentration s betwee n MW-507 A an dMW-502/MW-50 3 indicate s tha t ver y littl e contaminan t

mas s i s flowin g pas t

th e bedroc k troug h area . Concentration s o f benzene , chlorobenzene , 1,2,3-trichlorobenzen e an d 1,2,4-trichlorobenzen e wer e detecte dat lo w concentration s i n al l fou r well s MW-507A , MW

508B , MW-50 2 an dMW-503
. I n addition , concentration s o f VOC s a t MW-50 1 (downgradient

o f TWA III ) an d MW-511 A (downgradien t

o f TW A I ) hav e bee n no n detec t t o trac e levels
. Base do n thi s evaluatio n o f VO C data , well s alon g th e boundar y o f th e T I zon e ar e i n attainmen t o f federa l MCL s an d Main e MEG s (MW-501 , MW-502 , MW-50 3 an d MW-510A)
. Thes e decreasin g trend s i n VO C concentration s ar e likel y du e t o th e successfu l completio n o f th e SCR A an dremova l o f

residua l oi l with th e VE Rsystem , an dar e expecte dt o continue
. C
. Discharg e Zone , MW-106A/ B Concentration s o f

PCB s i n groundwate r

sample s collecte dfro mMW-106A/ B hav e no t

exceede d 1 3th e RO D targe t cleanu p leve l fo r

PCB s (0. 5 //g/L)
. Th e VO C concentration s fro mth e groundwate r i n MW-106 A an dMW-106 B hav e bee n relativel y consistent

over th e pas t si x years . MW-106 A monitor s th e overburde n aquife r a t thi s locatio n an dflow s unde r

lo w artesia n condition s durin g period s o f hig h groundwater
. Non

detec t t o trac e concentration s o f th e seve n VOC s hav e bee n detected
. Th e deepe r wel l (MW

106B) , flow s unde r

artesian condition s mos t

o f th e year , an d i s believe dt o b e interceptin g a portio n o f th e bedroc k

groundwate r

migratin g fro mth e site an d represent s th e bedroc k wate r quality
. Lo w level s o f

si x VO C compound s are regularl y detecte d a t MW-106B
. Th e concentration s o f

1,2,3-Trichlorobenzen e an d1,2,4-Trichlorobenzen e hav e generall y bee n decreasin g at

MW-106 B sinc e Marc h 199 7 an dMarc h 1995 , respectively , with mor e significan t decrease s i n 200 0 an d2001
. Th e 1,2,4-trichlorobenzen e concentration s ar e wel l belo w th e MC L an d 199 2 ME G o f 7 0 /ug/L
. (Ther e i s n o MC L o r

ME G fo r 1,2,3-trichlorobenzene
. However , i t ca n b e generall y assume d tha t it s ris k factor s woul db e simila

r t o 1,2,4-trichlorobenzene , an dth e detecte dconcentration s o f 1,2,3-trichlorobenzen e ar e als o wel l belo w 7 0 //g/L. ) Histori c PCB s an d VOC s result s o f th e MO M monitorin g conducte dbetwee n October 199 5 an d Septembe r 200 1 an dprio r

analytica l result s ar e include di n th e Jun e 200 2 Technica l Impracticabilit y Evaluatio n report , Appendice s G an dH
. 

### VII . SUMMAR Y O F SIT E RISK S Huma n health an d environmenta l ris k assessment s wer e conducte da s par t o f th e Feasibility Stud y leadin g u p t o th e 198 9 Recor do f Decision
. Thes e assessment s identifie dseve n exposur e scenario s a s posin g curren t an dpotentia l futur e risk s t o huma n health o r th e environment
. (ROD , pag e 13 ) O f

thes e seven , fiv e wer e associate dwit h th e soil s an d lagoo n sediments , on e wit h ingestio n offis h fro mRigg s Brook , an don e with ingestio n o f groundwate r

fro mth e bedrock :

• direc t

contac t with soil s b y children ;

• inhalatio n o f

vapor s fro msurfac e soils ;

• ingestio n offis h caugh t i n Rigg s Brook ;

• futur e direc t

contac t with soil s b y on-site inhabitant s

• futur e direc t

contac t with sediment s in the lowe r lagoo n by children ; and

• futur e inhalatio n o f vapor s b y on-sit e inhabitants ; and ;

• futur e ingestio n o f groundwate r

fro mwithi n th e bedrock
.

1 4Followin g th e completio n o f th e SCRA , onl y tw o potentia l exposur e scenario s remain
. The y ar e futur e ingestio n o f

groundwate r

fro mwithi n th e bedrock , an dingestio n offis h caugh t i n Rigg s Brook
. A site-wid e five-year

revie w wa s performe d i n 200 2 fo r al l thre e operabl e units
. Th e exposur e assumptions , toxicity data , an dcleanu p level s fo r groundwate r

wer e evaluate d a s par t

o f th e overal l protectivenes s determination
. Th e revie w di dno t identif y an y change s i n th e exposur e assumptions , foun dth e toxicity dat ahav e ha donl y minima l change s (som e slightl y increasing , other s decreasing ) an dconclude d tha t there ha dbee n n o significan t chang e i n sit e risks
. (EPA , 2002 ) Sinc e th e 198 9 ROD , th e Stat e o f Main e ha s promulgate d b y referenc e th e 199 2 MEGs
. Th e 199 2 ME G fo r

PCB s i s 0.0 5 ppb , a n orde r o f magnitud e lowe r

tha n th e MC L o f

0. 5 ppb , whic h i s th e RO D standard
. Excep t fo r th e immediat e are asurroundin g an dincludin g TW A II , PC B concentration s i n th e groundwate r wer e clos e t o thi s standar d (0.0 2 t o 0.0 9 pp b i n th e on e samplin g even t

wher e alowe r

detectio n limi t

wa s reached)
. Th e Restrictiv e Covenan t currentl y ensure s that

ther e wil l b e n o exposur e t o th e groundwate r beneath th e site
. 

### VIII . TECHNICA L IMPRACTICABILIT Y DETERMINATIO N Th e continue d presenc e o f separat e phas e PCB-lade n oi l fou r year s afte r

th e successfu l completio n o f

th e sourc e contro l remedia l actio n suggeste d restoratio n o f th e groundwate r

usin g th e VE Ro r

agroundwate r

extractio n an d treatmen t

syste mi s no t

possible
. Consequently , EPA , wit h concurrenc e fro mMain e DEP , agree d t o aproposa l b y CM P t o evaluat e whethe r i t woul d b e technicall y practicabl e t o restor e contaminate d groundwate r t o drinkin g wate r

standards , includin g MCL s an dMEGs
. Restoratio n o f

contaminate d groundwate r i s on e o f th e primar y objective s o f

th e Superfun d program . Th e NC P state s tha t "EP A expect s t o retur n usabl e groun d water s t o thei r beneficia l use s whereve r

practicable , withi n atim e fram e tha t i s reasonabl e give n th e particula r circumstance s o f

th e site. " Sectio n 300.430(a)(l)(iii)(F ) o f th e NCP
. Generally , restoratio n cleanu p level s in the Superfun dprogra mare establishe d by applicabl e or relevan t andappropriat e requirement s (ARARs) , suc h a s th e us e o f federa l o r stat e standard s fo r

drinkin g wate r

quality
. Further , unde r

CERCLA , a n alternativ e selecte d t o addres s contaminatio n at asite mus t

achiev e th e ARAR s identifie dfo r

th e action , o r

provid e th e basi s fo r

waivin g th e ARARs
. ARAR s ma y b e waive d fo r

an y o f si x reasons , includin g wher e complianc e wit h th e requiremen t

i s technicall y impracticabl e fro man engineerin g perspective
. Se e Sectio n 121(d)(4 ) o f CERCL A an dSectio n 300.430(f)(l)(ii)(C ) o f

th e NCP
. Th e primar y consideration s fo r determinin g th e technical impracticabilit y (TI ) o f

achievin g ARAR s ar e engineerin g feasibilit y an dreliability
. Se e NC P Preamble , 5 5 Fed
. Reg
. 874 8 (Marc h 8 , 1990)
. EPA' s Guidanc e fo r

Evaluatin g th e Technica l Impracticabilit y o f Ground-Wate r

Restoration
. (OSWE RDir
. 9234.2-25 , Septembe r 1993 , Interi mFinal ) specifie s th e followin g component s a s necessary fo r

aT I evaluation : 1 51
. Specifi c ARAR s o r medi astandar dfo r

whic h T I determination s ar e sought ; 2
. Spatial are aove r

whic h th e T I decisio n wil l apply ; 3
. Conceptual mode l that describe s sit

e geology , hydrogeology , groundwate r contaminatio n sources , fat e an dtransport ; 4
. A n evaluatio n o f

th e restoratio n potential , includin g predictiv e analyse s o f th e timeframe s t o attai n require dcleanup level s an d ademonstratio n that n o other remedial technologie s coul db e capabl e o f

achievin g groundwate r

restoration ; an d 5
. Cos t

estimate s o f

th e propose dremed y options
. Followin g aT I evaluation , EPA' s goa l o f restorin g contaminate dgroundwate r withi n a reasonabl e tim e fram e wil l b e modifie dwher e restoratio n i s foun dt o b e technicall y impracticable
. I n suc h cases , EP A wil l selec t a n alternativ e remedia l strateg y tha t i s technicall y practicable , protectiv e o f

huma n healt

h an d th e environment , an d satisfie s th e requirement s o f CERCL A an dth e NCP
. Wher e groundwate r ARAR s ar e waive da t

aSuperfun dsite du e t o technica l impracticability , EPA' s genera l expectation s ar e t o preven t furthe r migratio n o f

th e contaminate dgroundwate r plume , preven t

exposur e t o th e contaminate dgroundwater , an d evaluate furthe r

ris k reductio n measure s a s appropriate
. Se e Sectio n 300.430(a)(l)(iii)(F ) o f th e NCP
. Thes e expectation s shoul db e evaluate dalon g with th e nin e remed y selectio n criteri a provide di n th e NCP
. Th e result s o f

th e T I Evaluatio n fo r

O'Conno r

are provide dbelow
. 1
. ARAR s Unde r th e EP A Groundwate r

Protectio n Strategy , EP A ha s classifie dth e aquife r beneath th e site a s aClas s I I aquifer , i.e. , groundwate r whic h potentiall y coul db e asourc e fo r drinkin g wate r

i n th e future
. Thus , Maximu mContaminan t Level s (MCLs) , an dnon-zer o Maximu mContaminan t Leve l Goal s (MCLGs) , establishe dunde r th e Saf e Drinkin g wate r

Act , ar e ARARs
. Th e stat e Maximu mExposur e Guideline s (MEGs ) ar e chemical-specifi c ARAR s tha t ar e health

base dguideline s intende dt o determin e drinkin g wate r qualit y fo r

privat e residentia l wells
. MEG s ar e relevan t

an dappropriat e requirement s i n establishin g groundwate r remediatio n goals
. Th e MCL s an dMEG s fo r

whic h atechnica l impracticabilit y waiver wil l appl y ar e a s follows :

1 6Tabl e 3 : Chemical-Specifi c ARAR s fo r T I Waive r

Contaminan t O f Concern
Benzen e 1,4

- Dichlorobenzen e PCBs 1 Chlorobenzen e 1,2

- Dichlorobenzen e 1,3

- Dichlorobenzen e 1,2,3

- Trichlorobenzen e 1,2,4

- Trichlorobenzen e 1,3,5

- Trichlorobenzen e 2UU 1 Maximu m Groundwate r Concentratio n (//g/L ) an d Locatio n 8 - OW-302 B 72 0 - OW-302 B 4 4
. OW-302 B 24 0 - OW-302 B 210-OW-302 B 16 0 - OW-302 B 9 8 -OW-302 B 77 0 - OW-302 B
no t analyze d fo r MC L

(//g/L )
5 7 5 0. 5 10 0 60 0 N S N S 7 0 N S ME G (//g/L ) 5 2 7 0.0 5 4 7 8 5 8 5 N S 7 0 4 0 iy« y KUL > Targe t

Cleanu p Level s (//g/L ) 5 2 7 0. 5 n o RO D standar d n o RO D standar d
n o RO D standar d
n o RO D standar d
n o RO D standar d
n o RO D standar d
1 detectio n limi t

varie s with locatio n an d ar e generall y greate r tha n th e 199 2 MEG
. N S - n o standar d 2 . Spatia l Exten to f th e Technica l Impracticabilit y Zon e Thi s sectio n describe s th e horizonta l an d vertica l exten t ove r whic h th e Technica l Impracticabilit y decisio n woul d appl y (T I Zone)
. Thi s include s th e portio n o f groundwate r know n t o contai n VOC s abov e federa l MCL s an d Stat e MEG s tha t woul d requir e substantia l timeframe s t o remediat e usin g currentl y availabl e technologies
. Th e propose d T I Zon e horizontall y encompasse s th e TW A I I Are aan d th e are aassociate d with shallo w groundwate r

flo w t o th e sout h o f

th e TW A I I Area
. Vertically , th e propose d T I Zon e extend s int o bedrock
. Th e T I Zone , a s show n i n Figur e 3 , include s area s wher e VOC s an d PCB s are presen t

i n groundwate r

a t concentration s abov e RO D targe t cleanu p goal s an d curren t MCL s an dMEGs
. Thi s i s principall y th e TWA-I I area . Overall , analytica l result s fro mmonitorin g well s MW-501 , MW-502 , MW-503 , MW-505 , MW-509A , MW-510A , an d MW-511A , locate d alon g th e boundar y o f

th e T I Zone , sho w tha t

concentration s o f

th e seve n VOC s an d PCB s detecte d durin g semi-annual groundwate r monitorin g event s are belo w RO D targe t cleanu p goal s an dcurren t

MCL s an d MEGs
. 1 7I n revie w o f th e T I evaluatio n report , Main e DE P note dtha t th e T I zon e include dmos t o f th e forme r uppe r lagoon
. EP A recognizes , jus t a s th e boundar y o f

th e Designate d Are ai s bein g simplifie di n thi s RO D Amendmen t s o tha t i t ma y b e easil y identified , th e T I zon e ha s als o bee n establishe di n par t

t o allo w fo r

it s eas y identificatio n whil e onsite
. Consequently , whil e th e uppe r lagoo n wa s successfull y remediate ddurin g th e SCRA , aportio n o f i t fall s withi n th e T I zon e a s aresul t

o f simplifyin g th e T I boundary
. 3 . Conceptua l Mode l Th e conceptua l mode l serve s a s afoundatio n fo r evaluatin g th e restoratio n potentia l o f th e sit e and , thereb y assessin g th e technica l impracticabilit y a s well
. I t include s th e site geolog y an d hydrogeology , natur e an dexten t o f Contaminant s o f

Concer n i n groundwater , fat e an dtranspor t processes , andcurren t

or potentia l receptors . Thi s conceptua l mode l has bee n develope dthroug h revie w o f report s o f previou s investigation s an dth e visua l inspectio n o f subsurfac e material s durin g sourc e contro l work
. Th e SCR A involve dth e excavatio n o f asignifican t

portio n o f

th e site' s overburden , and , i n some places , exposure o f th e bedroc k

surface
. Thi s summar y o f

th e conceptua l mode l wa s presente di n th e Jun e 200 2 Technica l Impracticabilit

y Evaluatio n report . A
. Site Geolog y an dHydrogeolog y A summary o f

th e geolog y an dhydrogeolog y fo r th e overburde n an dbedroc k a t th e sit e i s provide dbelow
. 1
. Overburde n Geolog y Soil material s o n th e sit

e includ e glacia

l marin e silt s an d clay s an d glacia l til l overlyin g bedrock
. Th e uppe r cla y uni t ha s tw o stratigraphi c members : a n upper , stiff , desiccate dbrow n membe r an dalower , soft , gra y member
. Th e uppe r brow n membe r

whic h typicall y make s u p th e uppe r 1 0 to 2 0 fee t

o f th e cla y unit , i s blocky an d highl y fractured
. Th e lowe r gray membe r

i s absen t o r discontinuou s i n th e uplan dareas , wher e tota l overburde n thicknes s thin s t o les s tha n 2 0 feet
. Th e cla y tend s t o b e absen t

onl y i n area s o f

shallo w bedrock
. Th e til l i s discontinuous , varyin g i n thicknes s fro m0 t o approximatel y 4 2 fee t (B-503)
. Th e til l range s fro macoars e granula r materia l overlyin g th e shallo w bedroc k i n th e norther n an dwester n portion s o f

th e site , t o thick , dense , fine-graine dsoil s overlyin g th e deepe r bedroc k i n th e centra l an deaster n portion s o f

th e site
. I n th e TW A I I Area , th e til l i s approximatel y 0 t o 9 fee t thick
. Th e til l i s essentiall y absen t alon g th e axi s o f

th e bedroc k

ridg e fro mth e centra l t o th e norther n portio n o f th e site
. Th e change s i n th e observe dtexture s o f til l ar e inferre dt o resul t

fro m weathering
. Figure 7 show s th e locatio n o f thre e geologi c cros s section s acros s th e site
. Figur e 8 , Figur e 9 , an dFigur e 1 0 ar e th e geologi c cros s section s showin g th e inferre dsoi l stratigraph y an dbedroc k 1 8morphology. Th e stratigraphi c elevation s hav e bee n inferre dfro mth e boring s represente do n th e

profiles
. Th e inferre dgeologi c stratigraphy i s th e resul t o f th e MO M Additional Investigation s Repor t (W& C 1996a ) an d existin g boring s o n th e sit e prio r t o 1996
. Th e till/bedroc k

interfac e i s th e primar y migratio n pathwa y o f contaminants
. Th e result s fro m severa l wells , includin g B-506 , B-510 , B-514 , an d MW-504 , indicat e arelativel y highl y conductiv e water-bearin g zon e alon g th e till/bedroc k interface
. I n eac h o f

thes e borings , ver

y littl e wate r

wa s observe ddurin g th e drillin g proces s unti l th e dril l bi t penetrate dth e lower

2 t o 3 fee t o f th e til l immediatel y abov e th e bedroc k surface
. Th e potentiometri c surfac e i n eac h o f thes e boring s wa s severa

l fee t highe r tha n th e permeabl e zone , indicatin g aconfine dcondition
. Th e permeabl e zon e associate dwith th e till/bedroc k interfac e coul db e th e resul t o f a n erosiona l water-worke d environmen t i n th e initia l stage s o f

til l deposition
. Th e soil stratigraphy i n th e Uplan dMars h are aan d TW A I I Are awa s furthe r refine ddurin g an Uplan dMars h investigatio n conducte dt o identif y th e presenc e an ddistributio n o f oi l detecte di n an Uplan dMars h piezometer UM-1
. Thi s stud y helpe drefin e th e hydrogeolog y i n th e TW A I I Are aan dth e hydrogeologi c interactio n o f th e desiccate dclay with th e till/bedroc k migratio n pathway
. Th e stratigraph y o f

th e soi l materia

l i n th e Uplan dMars h are aconsist s o f approximatel y 4 to 1 0 fee t o f desiccate dbrow n cla y overlyin g approximatel y 1. 5 t o 7 fee t o f soft , unfracture dgra y clay that overlie s 2 t o 4 fee t

o f til l directl y i n contac t

wit h bedrock
. Thes e differen t layer s pinc h ou t i n area s o f shallo w bedroc k

(GeoProb e borin g G-14)
. Groundwate r i s confine di n th e til l an d predominatel y move s alon g th e till/bedroc k interface
. Surfac e wate r

infiltrate s int o th e fracture s in the brow n clay andis quasi-perche don top of the sof t clay , makin g itsel f

availabl e for evapotranspiration
. Base do n histori c wate r elevatio n data , th e quasi-perche dwate r tabl e i n th e brow n cla y fluctuate s a s muc h a s 6 t o 8 fee t durin g th e year . Figur e 1 1 show s apla n vie w o f th e sit e wit h th e GeoProb e location s an d th e locatio n o f thre e cros s sectio n lines
. Figure 12 , Figure 13 , an dFigur e 1 4 ar e th e geologi c cros s section s throug h th e Uplan dMars h are adepictin g th e stratigraphy , origina l groun dsurfac e prio r t o sourc e control , an dth e existin g groun dsurfac e afte r sourc e control
. I n general , th e thickes t

portion s o f

th e desiccate dclay wer e i n th e Uplan dMars h are awher e th e sit e topograph y flatten s (G-8 , G-9)
. Th e stratigraphy remain s relativel y consistent excep t i n th e norther n portio n o f

th e stud y are a(probe s G-12 , G-13 , G-14 , G-15 , an d G-16 ) wher e th e bedroc k surfac e rise s an d th e sof

t clay pinche s out . Se e Figur e 1 3 an d Figur e 14
. I n thi s are ath e desiccate dcla y i s i n contac t with th e till
. 2
. Bedroc k

Geolog y Th e shallo w an d dee p bedroc k flo w syste mat

th e sit e wa s studie di n several pre - an d post-RO D investigations
. Th e 199 6 fiel d study investigate dth e bedroc k surfac e i n an effor t

t o understan d th e potentia l migratio n pathwa y alon g th e to p o f th e bedrock
. Th e inferre dbedroc k surfac e elevatio n i s depicte di n Figur e 15
. Th e bedroc k

surfac e morpholog y ca

n als o b e viewe do n th e 1 9geologi c profile s o n Figure s 8-1 0 an d Figure s 12-14
. Th e bedroc k surfac e wa s verifie d durin g sourc e contro l work , i n location s wher e soi l wa s excavate d dow n t o th e bedroc k surface
. Th e bedroc k

surfac e consist s o f

ahard , minimall y weathere d quart z monzonite
. Drillin g log s fro mforme r

investigation s indicat e metasedimentary bedroc k intersperse d wit

h th e quart z monzonit e o n th e eastern portio n o f th e sit e (MW-406B ) suggestin g acontac t betwee n th e intrude dmonsonit e an dth e surroundin g metasedimentar y rock
. Th e bedroc k

structura l feature s wer e evaluate d bot h locall y an dregionall y i n th e Photogrammetri c Analysi s an d Outcro p Stud y (E
. C
. Jordan , 1986)
. Thi s evaluatio n utilize d photogrammetri c analysi s includin g th e examinatio n o f aerial photograph s an drada r imagery
. Additionally , fiv e bedroc k

outcrop s wer e examine d i n th e vicinit y o f th e site
. Thi s stud y include dinformatio n regardin g th e existenc e an dorientatio n o f bedroc k fracture s presen t

i n th e crystallin e rock s i n th e area . Result s o f thi s stud y determine d tha t th e regiona l structura l orientatio n i s i n anortheast-southwes t orientation
. Thre e prominen t NE/S W lineament s wer e identifie di n th e vicinity o f th e sit e i n th e E
. C
. Jorda n study
. Th e stud y als o determine d tha t th e mos t commo n strik

e orientatio n wa s NE/SW
. Th e Inferre d Bedroc k

Surfac e ma

p provide d i n Figure 1 5 show s that th e bedroc k

ridg e i s oriente d generall y o n anortheast-southwes t axi s coinciden t

with th e previousl y identifie dregiona l structural orientation
. Th e bedroc k ridg e i s anatura l featur e tha t ha s bee n scarre d an d rounde d b y th e las t glacia l advanc e an dretreat . I t i s aquart z monzonit e an da s suc h ha s n o beddin g o r structura l foldin g orientation
. Th e majo r structura l trend s outline d i n th e E.G
. Jorda n stud y refe r t o aNE/S W structura l orientatio n associate d with regiona l tectoni c compressio n histor y o f th e coas t o f Main e (refe r

t o th e bedroc k

geologi c map o f

Maine)
. Th e monzonit e intrusiv e i s par t o f th e Devonia

n intrusive s whic h intrude d th e country roc k o f th e regio n an d i s generall y elongate d paralle l t o beddin g strik e o f th e countr y rock
. Thi s ma y hav e ha dinfluenc e o n th e coolin g history an d pos t

placemen t

fracturin g o f

th e monzonite , bu t

i s believe d t o hav e n o direc t influenc e o n fracturin g o f

th e intrusiv e bod y an dthu s n o influenc e o n groundwate r movement . Conclusion s o f

th e 198 6 E.G
. Jorda n Stud y ar e a s follows :

• regiona l an d local strik e orientatio n i s northeast/southwest ;

• exfoliatio n typ e o f

near-horizonta l fractur e surface s ar e unifor man dwidesprea d throughou t

th e area ,
• "fracture s wil l hav e th e mos t significan t

impac t o n groundwate r

flo w pattern s withi n th e roc k mass" ;

• groundwate r

flo w fro mth e site i s expecte d t o b e generall y coinciden t with topography , an d

• th e potentia l exist s fo r

anortheast-southwes t

flo w barrie r

o r groundwate r

sin k i n th e vicinit y o f Rigg s Brook
.
2 0Th e bedroc k drillin g i n al l investigation s indicate dmostl y competen t roc k wit h very fe w recognizabl e fractures
. Th e rat e o f bedroc k drillin g wa s unusuall y slow
. Occasionally , a t rando mdepth s belo w th e bedroc k surface , th e downhol e drillin g equipmen t woul dadvanc e rapidly fo r 0. 2 t o 0. 4 feet , indicatin g th e existenc e o f awea k weathere dlaye r

o r fractur e i n th e bedrock
. Afte r

encounterin g awea

k laye r i n th e bedroc k

o r abedroc k

fracture , a n increas e i n th e availabl e formatio n wate r

woul db e observed , indicatin g th e presenc e o f groundwate r

i n th e fracture s i n th e uppe r

bedrock
. Durin g sourc e contro l wor k wher e th e bedroc k

surfac e wa s expose ddurin g soi l removal , th e bedroc k appeare dvery competent . Ver y fe w fracture s appeare d t o b e expose dalon g th e bedroc k surfac e an dnon e appeare dt o b e abl e t o suppl y an y significan t amoun t o f recharg e t o th e bedroc k

flo w system . Bedroc k

outcrop s ar e foun di n th e are ao f TW A I I an dt o th e sout h i n th e vicinity o f TW A I (refe r

t o Figur e 2)
. Generally , th e bedroc k

form s asaddle , wit h th e cente r o f th e saddl e immediatel y northeas t o f th e uppe r lagoo n (Figur e 2)
. Th e cente r o f th e saddl e form s atroug h fille dwit h til l an dth e overlyin g marin e clay
. Figur e 7 contain s geologi c cros s section s depictin g the bedroc k troug h in the cente r o f th e saddle
. Figur e 9 i s acros s sectio n alon g th e cente r o f th e saddl e an d Figur e 1 0 show s th e bedroc k ridg e t o th e northeas t

o f th e cente r o f th e saddle
. Th e til l i s absen t alon g th e to p ridg e an dmarin e clay i s i n direc t contac t wit h bedrock
. The limite dfractur e network of the bedroc k

flow syste mandlimite davailabl e recharg e fro mthe overburde n limit s flo w i n th e bedroc k aquifer
. Recharg e t o th e bedroc k fro mth e overburde n i s limite db y th e lo w permeabilit y overburde n soil s an dlac k o f shallo w groundwate r

i n th e overburden
. Becaus e th e bedroc k i s tight , limite dflo w move s throug h th e bedroc k system . 3
. Groundwate r

Flo w i n th e Overburde n an dBedroc k Flo w Syste m Th e principa l groundwate r migratio n pathwa y o n th e site i s adiscret e zon e withi n th e til l alon g th e to p o f th e bedroc k

surface
. Th e groundwate r flo w directio n i s asubdue dreflectio n o f th e bedroc k surface
. Figur e 1 6 show s th e inferre dgroundwate r flo w directio n superimpose do n th e bedroc k surfac e map . Groundwate r flo w fro mth e larg e recharg e basi n (Uplan dMarsh ) t o th e northwes t o f th e sourc e contro l are ai s confine dan dchannele dthroug h th e bedroc k troug h i n th e cente r o f th e bedroc k

saddle
. Th e reworke dtil l alon g th e bedroc k surfac e i s th e primar y migratio n pathwa y leavin g th e sourc e area . Th e bedroc k ridg e wher e th e til l i s absen t (refe r t o Figur e 10 ) inhibit s movemen t o f th e shallo w groundwate r

flo w fro mth e sourc e contro l are at o th e southeas t

towar d Rigg s Brook
. Th e uppe r til l an dclay ten dt o confin e th e groundwater , no t allowin g flo w ove r

th e bedroc k

ridg e a s depicte di n Figure 16 , an dforcin g flo w throug h th e bedroc k trough
. O n th e northwes t sid e o f th e ridg e an d withi n th e bedroc k trough , groundwate r unde r pressur e wa s observe ddurin g th e drillin g o f boring s B-514 , MW-504 , B-510 , an d B-506
. O n th e southeas t

sid e o f th e ridge , i.e. , B-515 , B-509 , MW-501 , B-508 , an d B-50 4 (Figure 16) , ver y littl e groundwate r

wa s observe dan d th e groundwate r wa s ver y slo w t o recharg e th e wells
. Unde r steady-stat e conditions , groundwate r i n thi s are awa s les s tha n 1- 2 fee t abov e th e bedroc k surface
. Conceptually , precipitation recharge s th e fracture dclay , till , an dbedroc k (wher e expose da t

th e 2 1surface) , an dflow s withi n th e shallo w groundwate r flo w regime
. Unde r

static , non-stresse d conditions , ther e i s ver

y littl e vertica

l mixin g betwee n th e overburde n an d bedroc k groundwate r i n th e immediat e are asurroundin g th e transforme r work areas . Althoug h adownwar dvertical gradient exists , th e relativel y lo w vertica l permeability o f

th e bedroc k

inhibit s vertica l migration
. Groundwate r

recharg e t o th e fil l soil s use dt o re-grad e th e site followin g th e SCR A doe s no t chang e th e overal l groundwate r flo w patterns . Th e bedroc k

ridg e inhibit s th e southeasterl y flo w o f shallo w groundwater
. Th e onl y water availabl e t o flo w o n th e southeas t sid e o f th e ridg e come s fro mrecharg e throug h th e cla y surfac e soil s an d groundwate r

dischargin g fro mth e bedrock
. Bot h source s o f recharg e t o th e til^edroc k migratio n pathwa y southeas t o f th e bedroc k

ridg e ar e very limited , leavin g somewhat dr y condition s withi n thi s migratio n pathway
. Th e contaminan t distributio n alon g th e till/bedroc k interfac e an dth e recharg e o f th e monitorin g well s i n thi s area , a s describe dabove , support s thi s understanding
. Long-ter mmonitorin g o f shallo w overburde n monitorin g wells , MW-50 1 an d MW-502 , indicate s ver y littl e overburde n groundwate r i n thi s are ao f

th e site
. Th e bedroc k

flo w regim e ha s ver y littl e wate r i n storage . Th e exfoliate dfractur e network i s far

reachin g an d derive s it s recharg e fro mth e uplan darea s surroundin g th e TWAs
. Th e vertica l permeabilit y o f

th e bedroc k

i s believe dt o b e very low , creatin g th e "quasi " perche dconditio n o f th e shallo w overburde n groundwate r flo w system . Over

mos t o f th e site , th e bedroc k groundwate r

i s unde r aconfine dcondition
. I n th e southeaster n en do f th e sit e th e potentiometri c surfac e o f th e bedroc k

groundwate r

i s abov e th e groun dsurface
. MW-106 B i s i n th e southeaster n portio n o f

th e site an di s afree-flowin g artesian well
. A s a n artesia n well , i t create s apressur e release , an d provide s aconditio n fo r contaminant s tha t

hav e entere dth e bedroc k

flo w regim e t o discharg e t o th e groun dsurface
. Th e overburde n groundwate r i s "quasi " perched ; releasin g groundwate r fro mstorag e t o suppl y recharg e to the bedroc k

fracture s wher e possible
. The horizonta l permeabilit y in the uppe r bedroc k zon e i s highe r

tha n th e vertica l permeability
. Thi s i s eviden t whe n comparin g th e potentiometri c surfac e o f

th e bedroc k

an d overburden
. Groundwate r elevatio n dat aincludin g potentiometri c surfac e map s an dtim e serie s plot s a t fou r wel l pair s ar e provide di n th e Jun e 200 2 Technica l Impracticability Evaluatio n report . Althoug h mos t o f th e bedroc k

well s ar e ope n hole s (i.e. , n o screene dzone s set ) th e wel l couple s (i.e. , MW-10 3 A , B ) ar e separate db y acasin g advance dint o rock
. Typically , th e overburde n well s ar e se t o n to p o f th e bedroc k

surfac e whil e th e bedroc k

well s ar e ope n hole s with groute dcasin g approximatel y fiv e fee t o r les s int o th e bedroc k surface
. Historically , th e differenc e i n groundwate r potential s acros s thi s relativel y shor t distanc e ha s bee n o n th e orde r o f 1 t o 2 feet
. Thi s downwar dgradien t i n th e sourc e contro l are a i s likel y du e t o th e lo w vertica l permeabilit y o f th e bedroc k

an dsupport s th e "quasi " perche d understandin g o f

th e vertica l groundwate r

flo w fro mth e overburde n int o th e bedrock
. Th e vertica l gradien t

i s downwar dove r

mos t o f th e site
. Th e vertical gradien t i s downwar dat wel l pai r MW-507A/MW-508B
. Prio r t o th e abandonmen t

o f wel l pair s MW-102A/B , MW

105A/ B an dMW-401A/

B fo r Sourc e Control , thes e well s exhibite ddownwar dvertica l gradients
.

2 2Th e vertica l gradien t i s upwar da t

th e locatio n o f

wel l pai r MW-106A/B
. Thi s wel l pai r i s locate dadjacen t

to Rigg s Broo k

andmonitor s the confine dbedroc k flo w syste mdowngradien t fro mth e site
. Bedroc k

a t thi s locatio n drop s considerabl y i n elevatio n an di s confine db y approximatel y 5 0 fee t

o f cla y soil s confinin g th e uplan dflo w fro mth e sit e t o Rigg s Brook
. Th e horizonta l gradient s hav e bee n calculate dfo r bot h th e overburde n aquife r an dth e bedroc k aquifer
. Th e gradient s ar e simila r i n bot h aquifers
. I n th e uplan dportion s o f th e site , th e horizonta l gradient s ar e approximatel y 0.0 1 an d0.02 4 o n th e overburde n an dbedroc k aquifers , respectively
. I n th e steepe r are abetwee n th e Uppe r

Lagoo n an d th e Lowe r

Lagoon , th e horizontal gradient s ar e approximatel y 0.0 9 an d 0.0 6 i n th e overburde n an d bedroc k aquifers , respectively
. Durin g th e 199 2 pumpin g test , th e bedroc k observatio n well s (MW-103B , MW-104B , MW

105B , OW-201B , OW-204B , OW-301B , an dOW-302B ) responde drelativel y quickl y and , with time , significan t

drawdow n wa s observe di n bedroc k well s a s far

away a s MW-105B
. Thi s indicate s tha t

groundwate r

i n storag e move dquickl y t o th e pumpin g wel l an dtha t recharg e (vertical ) fro mth e overburde n int o th e bedroc k wa s slow
. Becaus e groundwate r wa s take n fro m storag e withi n th e bedroc k an dwa s verticall y inhibite dfro mrechargin g th e bedroc k fro mth e overburden , recharg e t o th e pumpin g wel l cam e predominatel y fro mth e mor e regiona l network o f bedroc k fractures
. Significan t

drawdow n wa s observe dlon g distance s fro mth e pumpin g well
. The rapi drespons e observe din the bedroc k observatio n well s durin g pumpin g andthe exten t of drawdow n withi n th e bedroc k support s th e conceptua l understandin g tha t th e bedroc k

ha s afar

reaching , interconnecte dfractur e networ k with aver y lo w density o f fracture s an dthus , a relativel y slo w vertical permeabilit y an dvery littl e storage . Th e larg e variabilit y i n hydrauli c propertie s o f th e bedroc k

lend s t o th e conceptua l understandin g that th e fracture network , althoug h loosel y connected , i n th e bedroc k i s comprise do f

ver y fin e micr o fracture s that

d o no t yiel dmuc h wate r

an dlarge r

fracture s tha t

ma y yiel da s muc h a s 1 - 2 gpm . Th e bedroc k

i s relativel y tigh t

o n asite-wid e basis , a s observe db y th e perche dwate r table , visua l observation s durin g sourc e control , an dbedroc k RQ D analysi s don e durin g th e RI
. Th e bedroc k

i n th e lowe r

elevation s (nea

r wel l MW-106B ) i s confined , an dal l flo w leavin g th e site throug h th e bedroc k

flo w syste mi s confine dt o flo w fro mth e site towar dRigg s Broo k flowage , the n paralle l t o th e Rigg s Broo k flowage , an d eventuall y dischargin g t o th e Kennebe c Rive r Basin
. Becaus e o f

th e confine dnatur e o f

th e bedroc k

system , associate dlo w gradient s acros s th e site , an dth e lo w hydrauli c conductivitie s o f th e bedrock , very littl e wate r flow s naturall y throug h th e system . Wel l MW-106 B intersecte dadeepe r fractur e tha t

i s relativel y wel l connecte dt o th e bedroc k fractur e network

flowin g fro mth e site
. Whe n wel l MW-106 B wa s drilled , initia l concentration s o f sit e contaminant s at

thi s locatio n wer e non-detect
. Becaus e o f th e confine dcondition s an d th e fac t tha t wel l MW-106 B wa s allowe dt o flo w continuously , bedroc k flo w wa s shor

t circuite d increasin g th e gradien t

fro mth e site an dflushin g th e bedroc k flo w syste mtowar dMW-106 B an d eventuall y u p an d ou t

o f th e flo w systemthroug h thi s well
. A s i s show n b y th e chemica l dat a 2 3fro mMW-106B , sit e contaminant s increase dafte r th e 199 2 pum p test , whe n oi l wa s draw n dow n int o th e bedrock
. Contaminan t concentration s measure da t MW-106B , however , neve r exceede d RO D cleanu p goals
. Sinc e then , wit h groundwate r

flo w unde r

stead y stat e conditions , th e chemica l dat aha s show n astead y an dconsisten t decreasin g trend
. MW-106 B ha s provide da releas e o f aportio n o f

th e bedroc k

flo w systemt o th e groun d surfac e rather than flowin g of

f th e site
. Conceptua l depiction s o f

th e site hydrogeolog y befor e an dafte r sourc e contro l ar e presente di n figure s 1 7 an d18
. B
. Sourc e o f

Contaminatio n A n assessmen t

o f th e groundwate r

collecte dfro mth e monitorin g well s installe ddurin g th e RJ indicate dth e presenc e o f

lo w level s o f

chlorinate dbenzene s i n monitorin g well s downgradien t o f TW A I I an dth e Uppe r

Lagoo n are a(MW-10 4 an dMW-103)
. PCB s wer e onl y detecte di n sample s collecte dfro mMW-104B
. Fro msubsequen t investigations , i t

wa s foun dtha t

th e PCB s i n thi s wel l wer e no t

i n th e groundwate r

bu t wer e adsorbe dt o th e soi l particle s purge dfro mth e wel l durin g sampling
. Th e PCB s associate dwith thes e particle s wer e th e resul t o f drillin g throug h PCB-contaminate d surficia l soils
. Wel l MW-104 B ha s onl y on e foo t o f casin g se t

int o rock
. Surficia l sediment s ca n easil y migrat e int o th e borin g durin g wel l purging
. Metal s detecte d i n on-site well s were generall y comparabl e i n concentratio n t o upgradien t monitorin g an ddomesti c wells
. Th e result s o f

th e R I samplin g wor k

indicate dtha t

PCB s fro mth e transforme r salvag e operation s occurre di n thre e forme r

wor k area s locate di n th e wester n portio n o f th e site
. Thes e activitie s le dt o uncontrolle drelease s o f oi l containin g PCBs
. I n addition , surfac e erosio n ha dcause d PCB s t o migrat e ashort

distanc e fro mth e wor k

areas . Smalle r

amount s o f

PCB s ha dpermeate d int o th e subsurfac e soils
. Lo w level s o f PCB s wer e foun di n surfac e waters , sediments , an d biot a samples
. Lo w level s o f

othe r organi c an dinorgani c chemical s wer e als o foun di n som e media
. Base do n th e dat acollecte ddurin g post-RO D investigations , th e primary sourc e o f bot h oi l an d chlorobenzene s wa s th e fracture s i n th e clay
. Contaminant s wer e hel di n tensio n i n th e fracture s o f th e clay and , unde r

gravity , slowl y migrate dt o th e primar y migratio n pathwa y alon g th e till/bedroc k

surface
. Du e t o th e immiscibl e natur e o f th e oi l an dit s measure dspecifi c gravity o f 0.91 , th e oi l ha s remaine di n th e TW A I I Are awith onl y smal l amount s enterin g int o th e primar y migratio n pathway
. Th e chlorobenzene s wer e abl e t o dissolv e int o th e groundwate r an dmigrat e t o agreater

degre e withi n th e primary migratio n pathway
. Contaminan t

migratio n ha s no t

bee n significan t

beyon dth e TWA I I area . Th e followin g factor s serve dt o contro l and/o r

diminis h th e movemen t

o f chemical s i n soil s an dwater :

• lo w solubilit

y o f PCB s i n water ;

• th e stron g affinit y fo r

PCB s t o adher e t o soi l particles ; an d

2 4• th e presenc e o f thic k clay an dtil l deposit s i n th e near surfac e an ddee p groundwate r regimes
. Precipitatio n fallin g o n th e TW A I I Are aeithe r run s of f a s surfac e water

o r infiltrate s downward int o th e overburden
. A larg e portio n o f th e infiltratin g wate r

i s hel di n tensio n i n th e uppe r desiccate dclay laye r

an di s quasi-perche do n to p o f th e sof t clay layer , makin g itsel f

availabl e fo r evapotranspiration
. Very littl e recharg e enter s th e deepe r sof t clay layers , an deve n les s infiltrate s int o th e till/bedroc k flo w syste munde r

norma l conditions
. Th e desiccate dcla y fracture s allo w alimite dmigratio n pathwa y fo r wate r t o mov e downwar dtowar dth e till/bedroc k migratio n pathway
. C
. Fat e an dTranspor t

Processe s Contaminant s o n site migrat e with th e directio n o f th e groundwate r

flow
. Th e groundwate r

flo w directio n i s asubdue dreflectio n o f th e bedroc k

surfac e (Figure 16)
. Th e lo w vertica l permeability o f

th e bedroc k

act s t o for ma"quas i perched " conditio n alon g th e to p o f th e bedrock
. Althoug h i t

i s believe dtha t

th e bedroc k

receive s recharg e fro mth e uplan darea s northeas t o f th e bedroc k

trough , th e vertica l permeabilit y o f th e bedroc k

i s extremel y low , makin g th e bedroc k

amino r secondar y migratio n pathway
. Very littl e contaminan t mas s enter s th e bedroc k

flo w syste mthroug h natura l groundwate r flo w an dgroundwate r

recharge
. Contaminan t

mas s tha t i s abl e t o enter

th e bedroc k

flo w regim e unde r

stati c non-stresse d condition s flow s withi n th e fractur e networ k o f th e rock
. Th e storag e o f

groundwate r

withi n th e bedroc k i s extremel y low
. Recharg e t o apurge dwel l mos t likel y come s fro masignifican t distanc e away fro mth e monitorin g wel l du e t o th e lo w storag e capacity o f th e bedrock
. Th e overlyin g til l an d marin e clay confine s th e bedroc k aquife r a t lower elevations
. MW-106 B ha s bee n lef t flowing , providin g areleas e fo r contaminant s migratin g withi n th e dee p bedroc k flo w regim e an dlikel y represent s th e groundwate r withi n th e bedroc k

syste mthat

woul dhav e otherwis e migrate dfro mth e site
. I f MW-106 B di dno t

exist , i t i s believe dtha t

bedroc k groundwate r

dischargin g fro mtha t

wel l woul dleav e th e site flowin g t o th e east , wher e i t woul d the n flo w north roughl y paralle l t o th e Rigg s Broo k drainag e an d toward s th e regiona l groundwate r

sink o f th e Kennebe c Rive r

Basin
. Groundwate r

withi n th e primar y till/bedroc k migratio n pathwa y move s alon g th e bedroc k surfac e i n th e til l layer
. Thi s migratio n pathway , like th e bedroc k flo w system , ha s ver

y lo w storag e an d slo w groundwate r

velocities
. Therefore , eve n i n th e till/bedroc k migratio n pathway , ver y littl e wate r i s moving
. Contaminant s entere dthi s flo w syste mb y slo w recharg e fro mth e overlyin g cla y fractur e network
. Contaminant s i n groundwater , onc e i n th e till/bedroc k migratio n pathway , ar e restricte dfro mflowin g southeasterl y b y th e bedroc k ridg e an dflo w towar dth e natura l bedroc k troug h immediatel y northeas t o f th e uppe r lagoo n (refe r

t o figur e 16)
. Th e bedroc k troug h act s a s aspillway , channelin g flo w fro mth e uplan darea s surroundin g th e TWA s an d releasin g i t

t o flo w southeasterl y towar dRigg s Brook
. Sentine l monitorin g well s (MW-50 2 an d MW-503) , place dalon g th e fron t edg e o f contaminant s movin g throug h th e bedroc k trough , monito r th e long-termcontaminan t migratio n withi n th e till/bedroc k migratio n pathway
. 2 5Dissolve dVOC s ar e migratin g with th e groundwater , however , du e t o dilution , th e

concentration s o f

VOC s a t well s alon g th e boundar y o f th e T I Zon e ar e belo w th e RO D targe t cleanu p goal s an dcurren t

MCL s an dMEGs
. Residua l oi l containin g PCB s an dVOC s i s hel di n tensio n i n th e desiccatio n crack s i n th e cla y an dt o alimite dexten t

i n fracture s i n th e bedrock
. Unde r natura l conditions , ther e i s very littl e movemen t o f thi s oil
. Concentration s o f PCB s i n monitorin g well s alon g th e boundar y o f th e propose dT I Zon e hav e bee n belo w th e RO D targe t cleanu p leve l o f

0. 5 /ug/L
. However , durin g asamplin g event

conducte di n Marc h 199 9 usin g lowe r detectio n limits , concentration s o f PCB s wer e at o r slightl y abov e th e 199 2 Main e ME G o f 0.0 5 //g/L at

MW-50 3 an d MW-106
. Thes e well s ar e o n th e boundar y o r outsid e o f

th e propose dT I Zone
. Continue dmonitorin g wil l b e conducte dt o determin e i f

concentration s o f

PCB s outsid e th e propose dT I Zon e mee t th e 199 2 Main e MEG
. 4. 0 Evaluatio n o f

th e Restoratio n Potentia l Thi s sectio n evaluate s th e restoratio n potentia l b y assessin g th e performanc e o f remedial action s previousl y conducte dan d thos e tha t are ongoin g a

t th e site , an d evaluate s additiona l technologie s t o determine i f

an y coul drealisticall y attai n drinkin g wate r standard s fo r

th e site withi n a reasonabl e tim e frame
. Remedia l action s hav e bee n conducte di n thre e operabl e unit s at th e site ; OU- 1 Sourc e Contro l Operabl e Unit , OU- 2 Managemen t o f Migratio n Operabl e Unit , an dOU- 3 Rigg s Brook
. Remedia l action s a t

operabl e unit s OU- 1 an dOU- 2 ar e discusse dbelow , a s the y ar e relevan t t o th e concentratio n o f

contaminant s i n groundwate r a t th e site
. A
. Sourc e Contro l Measure s Th e SCR A fo r

OU- 1 wa s successfull y complete do n Novembe r 11 , 1997
. Th e sourc e remediatio n wa s conducte db y samplin g an dexcavatin g soil s an dsediment s contaminate dwith PCBs , lead , an d cPAH s abov e th e RO D an d ES D targe t cleanu p goals
. Approximatel y 20,00 0 ton s o f soi l an d sedimen t

wer e remove dfro mth e site
. Anothe r 3,00 0 ton s wer e excavate dan d consolidate dint o th e designate dare a(refe r t o Figur e 5 ) t o mee t

th e ES D targe t

cleanu p goals
. Soi l an d sediment

i n OU- 1 wer e sampled , excavate dan d re-sample dunti l ther e wa s n o indicatio n o f soi l containin g PCBs , cPAH s o r lea dabov e th e targe t

cleanu p goals
. B y meetin g th e require d targe t cleanu p goal s fo r

soil s an dsediment , an dremovin g site surfac e waters , th e SCRA achieve dth e remedial actio n objective s establishe dfo r th e Sourc e Contro l component i n th e 198 9 ROD
. Eve n afte r th e successfu l completio n o f th e SCRA , som

e residual oi l containin g PCB s an d VOC s remain s trappe di n desiccatio n crack s i n th e cla y an dt o alimite dexten t

i n fracture s i n bedroc k

a t th e site
. Althoug h residua l oi l remain s i n tensio n i n crack s i n th e clay , whe n i t ha s bee n analyze d i n ahomogenize dcla

y sample , th e concentration s hav e bee n belo w th e targe t cleanup goals
. Therefore , althoug h thi s remedy wa s no t abl e t o remov e al l th e residua l oil , th e approve dSCRA 2 6remediate dth e sourc e are aan d me t th e remedia l actio n objective s state d i n th e ROD
. Th e subsequen t

Uplan dMars h stud y confirme dtha t th e remedia l objective s o f th e SCR A wer e met , eve n thoug h som e residua l oi l remains
. Th e Uplan dMars h Stud y als o confirme dtha t concentration s o f

PCB s detecte di n th e dessicatio n crack s i n th e clay containin g oi l range dfro m N D t o 1 ppm . Therefore , concentration s o f PCB s i n th e fracture s di d no t excee dth e RO D targe t cleanu p leve l o f

1 pp mestablishe dfo r

th e site
. B
. Analysi s o f

Remedia l Actio n Performanc e an dRestoratio n Timefram e Th e groundwate r

remedia l alternativ e stipulate di n th e 198 9 RO D wa s th e installatio n an d operatio n o f

apum p an dtrea t

system . Durin g th e developmen t o f th e conceptua l understandin g o f th e site , th e effectivenes s o f th e pump an d treat

systemwa s evaluated
. Thi s evaluatio n indicate dtha t

atraditiona l pum p an dtrea t syste mcoul dmobiliz e contaminant s verticall y downwar dan dfurthe r

contaminat e groundwater
. Consequently , aVE Rsyste mwa s chose n rathe r tha n atraditiona l pum p an dtrea t system . Th e constructio n an doperatio n o f th e VE R syste mdiffere dfro mth e pum p an dtrea t system , a s originall y conceived , i n tha t i t extract s oi l an dwate r fro mth e site withou t

significantl y lowerin g th e groundwate r table
. Thi s woul dlimi t th e drawdow n o f

th e wate r tabl e int o th e bedroc k

an dtherefor e no t

allo w mobilize dresidua l oi l t o ente r th e bedrock , whic h coul dfurthe r contaminat e th e bedroc k

groundwater
. A s describe di n detai l i n th e Draf t Propose dFina l Managemen t o f Migratio n Remed y (W&C , 1997d) , th e VE Rpilo t

stud y wa s conducte dwit h th e objectiv e o f recoverin g oi l bot h i n th e saturate dan dunsaturate dzone s withou t furthe r contaminatin g th e bedroc k groundwater
. Th e operatio n o f

th e VE Rpum p an dtrea t

syste m(Phase s I an dI I conducte di n 199 6 an d1997) , couple dwit

h th e long-ter moperatio n an dpulsin g o f th e system , resulte di n th e remova l o f 26. 6 gallon s o f oi l fro mwithi n th e primar y migratio n pathwa y an dfro msourc e area s withi n cla y fracture s i n th e TW A I I Are a(se e Tabl e 4)
. Durin g Phas e I I o f

th e VE Rsyste moperation , th e limitation s o f th e aquife r

wer e realize dwit

h respec t t o oi l recovery . Som e o f

th e residua l oi l i n th e immediat e vicinit y o f th e VE Rwel l wa s removed , bu t

a s vacuu mpressur e decrease dawa y fro mth e well , surfac e tensio n force s an d limitation s inheren t

with multi-phas e flo w inhibite dth e movemen t o f residua l oi l t o th e well
. Th e VE Rsyste mwa s the n pulsed , t o creat e astres s i n th e system , i n a n effor t t o induc e produc t recharg e t o th e extractio n well
. Followin g tw o week s o f operation s (Phas e II) , th e syste mwa s pulse dfo r anothe r thre e month s i n a n effor t

t o tr y an dremov e a s muc h oi l a s possible
. Durin g thi s time , approximatel y 1 0 gallon s o f oi l wa s remove donl y whe n th e syste mwa s pulsed
. Followin g th e completio n o f th e SCRA , passiv e oi l recover y ha s bee n conducte di n bedroc k well s i n th e TW A I I Area
. Th e amoun t o f oi l recovere dpassivel y betwee n Decembe r 199 7 an d Augus t 200 1 wa s 7. 1 gallons
. I n th e past , th e VE Rsyste mha dsuccessfull y remove doi l fro m th e till/bedroc k

interface ; therefore , i n Augus t 200 1 VE RPhas e II I syste moperatio n wa s initiate dt o addres s th e remova l o f oi l i n bot h th e bedroc k

an doverburde n soils
. A tota l o f 19. 8 gallon s wer e recovere ddurin g thi s VE Roperatio n compare dt o 26. 6 gallon s collecte ddurin g Phas e I an d Phas e I I VE Roperation
. Followin g th e VE RPhas e III , betwee n Novembe r 200 1 an d 2 7Marc h 2002 , 1. 9 gallon s o f oi l wer e recovere dpassivel y fro mth e wells
. Mos t o f thi s oi l (1. 7 gallons ) wa s recovere di n OW-302B , an d appear s t o b e directl y relate dt o oi l induce dt o th e wel l b y th e VER
. Th e tota l oi l sinc e th e SCR A completio n i s 28. 8 gallon s (Phas e II I an dth e passiv e recovery)
. Base do n th e result s o f

groundwate r

monitorin g dat aan dth e studie s complete donsite , th e groundwate r

an dmas s flu x throug h bot h th e bedroc k an doverburde n flo w system s appear s t o b e ver y low
. Du e t o remova l o f contaminate dsourc e soil s durin g th e SCRA , an d remova l o f additiona l residua l oi l fro mth e overburde n an dbedrock , th e concentration s o f VOC s i n groundwate r

hav e bee n reduce dan d ar e expecte dt o continu e t o decrease
. Concentration s o f VOC s ar e belo w MCL s an d MEG s outsid e o f th e T I Zone
. A t

MW-104 B an d OW-201B , jus t insid e th e propose dT I Zone , bu t outsid e o f

th e TW A I I Area , VOC s slightl y excee dMEGs
. Base do n th e observe dtrend s o f decreasin g VO C concentration s i n thes e wells , i t i s estimate d tha t VO C concentration s wil l b e belo w MCL s an dMEG s a t well s outsid e th e TW A I I Are a withi n th e nex t

5 to 1 0 years . A s note di n th e discussio n o f oi l movement

withi n th e subsurface , recover y an d o r treatmen t o f residua l oi l wil l b e difficult
. I t i s believe dtha t

i t coul dtak e hundred s o f

year s t o remov e th e residual oi l an d meet

drinkin g wate r

standard s fo r

PCB s an d VOC s withi n th e TW A I I Area
. A s previousl y stated , residua l oil , the primar y sourc e of PCB s andVOCs , is trappe din fracture s in clay an dbedroc k

withi n th e TW A I I Area
. Th e quantit y o f residua l oi l remainin g i s unknow n an ddu e t o surfac e tensio n an dothe r force s holdin g thi s residua l oi l i n equilibrium , ther e i s littl e migratio n unde r

norma l conditions
. Eve n thoug h th e VE Rsyste mha s remove damoderat e amoun t o f residua l oil , an dma y continu e t o remov e oil , th e difficult y o f inducin g oi l movemen t

withi n th e clay desiccatio n crack s an dth e bedroc k fracture s make s i t

unlikel y tha t

th e residua l oi l ca n b e completel y removed
. Therefore , ther e wil l alway s b e residua l oi l availabl e t o wate r infiltratin g int o th e TW A I I Area
. Becaus e th e TW A I I Are ai s a t

th e to p o f

th e ridge , ther e i s littl e groundwate r flo w throug h thi s area . Mos t o f th e groundwate r

flo w throug h th e TW A I I Are ai s fro mth e infiltratio n o f rainwate r an d snowmelt
. Th e infiltratin g wate r wil l dissolv e PCB s an dVOC s t o thei r respectiv e solubilities , continuin g t o ad d dissolve dsourc e t o th e groundwate r withi n th e TW A I I Area
. I n order t o estimat

e th e dissolutio n tim e o f

PCB s withi n th e oil , asimpl e solubilit y calculatio n was done
. Thi s calculatio n didnot incorporat e the dissolutio n of the oil itself
. It

is believe dtha t th e oi l wil l remai n essentiall y unchange dan dth e PCB s wil l dissolv e ou t o f th e oil
. Assumin g tha t ther e i s approximatel y 10 0 gallon s o f oi l lef t a s residual , wit h a n averag e concentratio n o f 300 0 pp b an dasolubilit y o f 2. 7 pp b (USEPA , 1990 ) an dassumin g approximatel y 2. 5 gp m groundwate r

flo w throug h th e syste ma t adissolutio n concentratio n o f 20 % o f solubility , th e tim e t o dissolv e th e PCB' s woul db e 37 2 years . Give n dissolutio n o f 10 % o f solubility , tim e t o dissolv e woul db e 74 4 years . A s note dabove , sinc e th e quantit y o f residua l oi l remainin g i n th e subsurfac e i s unknown , on e hundre dgallon s wa s chose n a s areferenc e point
. Th e technica l impracticabilit y evaluatio n identifie dan d screene deightee n technologie s t o asses s 2 8thei r

abilit y t o restor e th e groundwate r t o drinkin g wate r

qualit y withi n areasonabl e timeframe
. Thes e technologie s include dinsitu applicatio n o f oxidizers , alternat e groundwate r containmen t approaches , a s wel l a s excavatio n o f al l overburde n soil
. Th e evaluatio n conclude dtha t non e o f thes e technologie s woul dachiev e th e cleanu p goal s withi n areasonabl e timeframe
. I n summary :

• Th e majorit y o f

PCB s wer e remove ddurin g th e SCRA i n 199 6 an d1997 ; residua l oi l containin g PCB s an dVOC s remain s trappe di n bedroc k fracture s an ddesiccatio n fracture s i n th e clay ;

• Site investigation s sho w tha t ther e i s littl e movemen t

o f residua l oi l containin g PCB s an d VOC s fro mth e TW A I I Area ;

• Th e VERsyste mha s ha dmoderat e succes s removing oi l fro mth e bedroc k an doverburden ;

• A Restrictiv e Covenan t ha s bee n signe db y CM P an d Main e DE P tha t prohibit s us e o f

th e groundwate r

beneath th e site
. Publi c wate r i s availabl e o n Rout e 1 7 t o th e south an dCon y Roa dt o th e west . Th e neares t know n residentia l wel l i s approximatel y ahal f mil e t o th e east , situate do n ahil l abou t

tw o hundre dfee t

abov e th e Rigg s Broo k

discharg e area . Thi s wel l intercept s flo w movin g wes t towar dRigg s Brook
. Therefore , ther e i s n o curren t drinkin g wate r exposure ;

• Base do n th e observe dtrend s o f decreasin g VO C concentration s i n groundwate r sinc e th e completio n o f

th e SCRA , i t

i s estimate dtha t

VO C concentration s at

well s outsid e o f

th e TW A I I Are awil l b e belo w MCL s an dMEG s withi n th e nex t 5 t o 1 0 years ; an d

• Du e t o th e difficult y o f removin g residua l oil , i t

i s believe dtha t

i t coul drequire hundred s o f year s t o remov e residua l oi l an dmee t drinkin g wate r

standard s fo r

PCB s an dVOC s withi n th e TW A I I Area
. 5
. Cos t Estimate s Th e cos t estimat e o f

th e amende dremed y i s describe di n Sectio n X below
. Mor e detaile dinformatio n regardin g th e technica l impracticabilit y o f restoratio n o f

th e overburde n an dbedroc k

groundwate r

ca n b e foun di n th e Fina l Technica l Impracticabilit y Evaluatio n Report
. (W&C , Jun e 2002 )


### IX . COMPARATIV E ANALYSI S O F TH E ORIGINA L REMED Y AN D OU- 2 ALTERNATIVE S Sectio n 121(b)(l ) o f

CERCL A present s severa

l factor s that

EP A i s require dto conside r i n it s 2 9assessmen t of alternatives
. Buildin g upo n thes e specifi c statutor y mandates , the NCP articulate s nin e evaluatio n criteri at o b e use d i n assessin g remedial alternatives
. Thes e criteri aare a s follows : Threshol d Criteri a I n accordanc e wit

h th e NCP , tw o threshol d criteri amus t b e me t i n orde r fo r th e alternativ e t o b e eligibl e fo r

selection : 1 . Overal l protectio n o f huma n healt h an d th e environmen taddresse s whethe r o r no t a remed y provide s adequat e protection , and describe s how risks pose d throug h eac h exposur e pathwa y ar e eliminated , reduce d o r controlle d throug h treatment , engineerin g control s o r

institutiona l controls
. 2 . Complianc e wit h applicabl e o r relevan tan d appropriat e requirement s (ARARs ) addresse s whethe r

o r no t aremed y wil l mee t

al l o f th e ARAR s o f

promulgate d stat e an d federa l environmenta l an d facility-sitin g requirements , an d i f not , provide s th e ground s fo r invokin g aCERCLA waiver(s ) fo r thos e requirements
. Primar y Balancin g Criteri a Th e followin g fiv e criteri aar e use d t o compar e an d evaluat e thos e alternative s whic h fulfil l th e tw o threshol d criteria
. 3 . Long-ter m effectivenes s an d permanenc e assesse s alternative s fo r th e long-ter m effectivenes s an d permanenc e the y afford , alon g wit h th e degre e o f certainty tha t

the y wil l b e successful
. 4 . Reductio n o f

toxicity , mobilit y o r volum e throug h treatmen taddresse s th e degre e t o whic h alternative s emplo y treatmen t to reduc e toxicity, mobilit y or volume , and how treatmen t i s use d t o addres s th e principl e threat s pose d b y th e site
. 5 . Shor tter m effectivenes s addresse s th e perio d o f tim e neede d t o achiev e protectio n an d an y advers e impact s o n huma n healt h an d th e environmen t

that may b e pose d durin g th e constructio n an d implementatio n o f th e alternativ e unti l cleanu p goal s ar e achieved
. 6 . Implementabilit y addresse s th e technical an d administrativ e feasibilit y o f an alternative , includin g th e availability o f material s an d service s neede d t o implemen t aparticular option
. 7 . Cos tinclude s estimate d capita l a s wel l a s operatio n an d maintenanc e costs , o n ane t present-worth basis
. Modifyin g Criteri a

3 0Th e tw o modifyin g criteri adiscusse dbelo w ar e use di n th e fina l evaluatio n o f remedia l alternative s generall y afte r

EP A ha s receive dpubli c commen t o n th e RI/F S an dPropose dPlan
. 8 . State acceptanc e addresse s th e State' s positio n an d ke y concern s relate dt o th e preferre d alternativ e an d othe r

alternatives , an d th e State' s comment s o n ARAR s o r th e propose d us e o f waivers
. 9 . Communit y acceptanc e addresse s th e public' s genera l respons e t o th e alternative s describe di n th e feasibilit y stud y an dPropose dPlan
.
Th e followin g i s acompariso n o f th e 198 9 RO D remed y an dth e alternative s evaluate dfo r thi s RO D amendment , contrastin g eac h remedy' s component s with respec t t o th e nin e evaluatio n criteria
. 198 9 Remed y Th e 198 9 RO D selecte dacomprehensiv e approac h t o th e contamination
. Th e sourc e contro l action s include dth e cleaning , demolition , an doff-sit e disposa l o f th e bar n situate dalon g Rout e 17 , remova l an doff-sit e disposa l o f th e standin g wate r

i n th e tw o lagoons , an dth e excavatio n an dtreatmen t

b y solven t

extractio n o f

th e soil s an dsediment s contaminate dwit h PCBs , cPAHs , an d lead
. Managemen t

o f migratio n action s include dth e pumping , treatment , an d disposa l o f th e contaminate dgroundwate r fro mth e soi l an dbedrock , an dsamplin g o f sedimen t an dfis h i n Rigg s Broo k

fo r te n years . Alternativ e 1 : Institutiona l Controls , Long-Ter m Monitoring , an d Passiv e Oi l Recover y I n thi s alternative , EP A recognize s that th e groundwate r

beneat h aportio n o f

th e site (T I zone , se e Figur e 3 ) wil l no t

b e o f drinkin g wate r

qualit y fo r

a n extende dperio do f

time , potentiall y mor e than ahundre dyear s fo r reason s state d abov e i n Sectio n VIII
. Whil e th e are ao f August a wher e th e site i s locate dha s no t see n rapi dgrowt h durin g th e tim e th e F
. O'Conno r Compan y operate do r

sinc e it s closing , th e are aca n reasonabl y b e expecte dt o experienc e som e growt h durin g th e tim e perio dneede dt o reac h th e drinkin g wate r quality
. Therefore , establishe dan d forma l control s ar e neede dt o preven t us e o f th e groundwate r

o n th e sit e an d t o preven t th e contaminatio n fro mspreadin g b y stressin g th e aquife r beneat h th e site
. CM P an d Main e DE P hav e entere dint o aRestrictive Covenan t tha t prohibit s us e o f

th e groundwate r

withou t prio r approva l fro mMain e DEP
. Thi s Restrictiv e Covenan t wil l remai n i n plac e unti l terminate db y Main e DEP
. Should , however , EP A fin dtha t thi s covenan t

i s n o longe r

protective , effective , o r i t interfere s with th e performanc e o f th e remedy, additiona l institutiona l control s wil l b e place d o n th e property . Operatio n an dmaintenanc e activitie s wil l ensur e tha t th e institutiona l control s remai n i n plac e an dare effectiv e fo r

thei r state dpurpos e an d tha

t th e Sit e i s manage dproperl y t o maintai n th e 3 1protectiv e layer o f clea n soi l abov e thos e soil s wit h lo w level s o f

PCBs
. Long-termmonitorin g o f

th e groundwate r

wil l allo w EP A an d Main e DE P t o trac k th e residua l oi l an ddissolve dPCB s an dVOC s withi n th e T I zon e an doutsid e o f it
. Thi s dat awil l allo w th e agencie s t o evaluat e whethe r th e concentration s ar e continuin g t o decrease , whethe r th e contaminatio n i s movin g beyon dit s current limit , an d whethe r

there i s achang e i n concentration s dischargin g int o Rigg s Broo k wetlands
. I n th e even t

tha t th e monitorin g dat aindicat e a n increas e i n PC B o r

VO C levels , respons e action s wil l b e evaluated , an da s appropriate , implemente da s par t

o f thi s amende dROD
. I n additio n t o thes e components , Alternativ e 1 woul dinclud e passiv e oi l recovery wher e absorben t material s woul dperiodically b e use dt o recove r fre e oi l whic h ha s draine dunde r normal condition s int o th e TW A I I wells
. Thi s woul dcontinu e unti l fre e oi l wa s n o longer observe di n th e wells
. Th e absorben t material s woul db e dispose do f a t alicense dTS D facility
. Th e estimate dperio do f

operatio n fo r

thi s alternativ e i s i n exces s o f on e hundre dyears . Th e estimate dne t

presen t wort h fo r thi s alternativ e i s $622,000
. (Cost s wer e develope dfo r thirt y year s per EP A guidance ; however , EP A expect s i t wil l tak e considerabl y longer t o reac h drinkin g wate r quality. ) Alternativ e 2 : Institutiona l Controls , Long-Ter m Monitoring , Activ e an d Passiv e Oi l Recover y Thi s alternativ e i s EPA' s selecte dalternative
. I t add s activ e recover y o f

residua l oi l t o th e component s include di n Alternativ e 1
. O n a n annua l basis , avacuu mwoul db e applie dt o well s withi n TW A I I t o dra w th e residua l oi l an dVOC s fro mth e soi l an dbedrock
. EP A i s proposin g th e annua l applicatio n t o coincid e wit h norma l lo w groundwate r level s a s tha t

ha s bee n th e tim e whe n th e amoun t

o f oi l i n th e well s ha s bee n th e greatest . Eac h applicatio n woul d continu e a s lon g as it was practica l to remov e the oil (th e criteri afor thi s is furthe r

discusse din Sectio n X.2.)
. Pas t applicatio n suggest s tha t

eac h applicatio n woul dlas t abou t fou r t o si x weeks
. Th e annua l application , fro myea r

t o year , woul dcontinu e a s lon g a s i t wa s practical
. Passiv e oi l recover y woul db e implemente dbetwee n th e activ e pumpin g efforts
. Th e recovere doi l an dth e absorben t material s woul db e dispose do f at alicense dTS D facility
. Th e estimate dperio do f

operatio n fo r

thi s alternativ e i s i n exces s o f on e hundre dyears . Th e estimate dperio do f

operatio n fo r

th e activ e oi l recover y i s fiv e t o te n years . Th e estimate dne t presen t wort h fo r thi s alternativ e i s $1,055,000
. (A s with Alternativ e 1 , cost s wer e develope dfo r thirt y year s pe r

EP A guidance ) EP A develope dthes e alternative s base do n informatio n containe di n th e 200 2 Technica l Impracticabilit y Evaluatio n submitte db y CMP , whic h i n tur n followe ddiscussion s wit h EP A an dMain e DE P regardin g site conditions
.

3 2Compariso n o f th e Origina l Remed y fo r Groundwate r an d th e OU- 2 Alternative s t o th e Nin e Criteri a 1
. Overal l Protectio n o f

Huma n Healt

h an dth e Environmen t Thi s criterio n consider s whether th e remedy , a s awhole , wil l protec t huma n healt

h an d th e environment
. Thi s include s a n assessmen t o f ho w publi c health an denvironmenta l risk s ar e properl y eliminated , reduced , o r controlle dthroug h treatment , engineerin g controls , o r institutiona l controls
. Th e origina l remed y include dpum p an d trea t technolog y a s th e metho dt o achiev e groundwate r restoratio n throughou t

th e Site
. Whil e thi s technolog y wa s t o b e implemented , short-ter m institutiona l control s wer e t o b e se t i n plac e t o preven t

exposur e t o th e contaminate d groundwater
. Thi s selectio n wa s consisten t wit h th e belie f

a t th e tim e tha t

thi s technolog y coul d effectivel y restor e contaminate dgroundwater
. I n 2002 , EP A conclude dthat restoratio n wa s no t feasible
. Therefore , withou t achievin g restoratio n withi n areasonabl e tim e fram e o r havin g a long-ter mmean s t o preven t exposur e t o th e contaminate dgroundwater , th e origina l remed y i s n o longe r protectiv e o f

huma n healt

h an dth e environmen t

i n th e long-term
. Alternative s 1 an d2 recogniz e tha t fo r aportio n o f

th e site , i t

i s technicall y impracticabl e t o restor e th e groundwate r

t o drinkin g wate r

quality , an d therefore , t o preven t exposur e t o th e contaminate dgroundwate r fo r an extende dperio do f

time , along-terminstitutional contro l i s a componen t

o f bot h alternatives
. I n addition , bot h alternative s includ e long-ter mmonitorin g o f groundwate r

t o demonstrat e tha t

th e contaminatio n i s no t

expandin g an dtha t

natura l processe s wil l continu e t o decreas e th e contaminan t concentrations
. Alternativ e 2 provide s greater overal l protectio n b y activel y removin g separat e phas e oi l fro mth e overburde n soi l an dbedroc k an d thu s mor e quickl y reduce s th e toxicity
. Thereby , wit h th e institutiona l contro l provide db y th e Restrictiv e Covenant , thi s componen t ensure s th e protectivenes s o f th e remedy
. Th e protectio n o f

huma n health an dth e environmen t i s th e mos t

importan t

criterion
. Th e Restrictiv e Covenan t

protect s huma n health a s i t prevent s huma n exposur e t o contaminate d groundwater
. Th e environmen t i s protecte dthroug h th e soi l remova l an drecovery o f th e fre e oi l (b y removing th e sourc e o f contamination , th e amoun t o f residua l contaminatio n availabl e t o aquati c an d terrestria l receptor s i s expecte dt o continu e t o decrease)
. Long-ter mmonitorin g wil l allo w EP A an d Main e DE P t o kno w whethe r th e remed y i s appropriate
. Bot h alternative s EP A evaluate drel y o n th e Restrictiv e Covenan t an dlong-ter mmonitoring
. 2
. Complianc e wit

h Applicabl e an d Relevan t

an d Appropriat e Requirement s Thi s criterio n addresse s whethe r o r no t aremed y complie s wit h al l promulgate dstat e an dfedera l environmental an d facilit

y siting requirement s that

appl y o r are relevant

an d appropriat e t o th e condition s an dremed y a t

aspecifi c site
. I f

a n ARA Rcanno t

b e met , th e analysi s o f

aremed y mus t provid e th e ground s fo r

invokin g astatutor y waiver
.

3 3Whe n th e original remed y wa s selecte di n th e 198 9 ROD , i t wa s believe dtha t

th e remed y woul d attai n al l identifie dfedera l an dstat e ARARs
. Bot h alternative s includ e aT I waive r o f drinkin g wate r

standard s fo r

th e are aidentifie da s th e T I zon e (Se e Figur e 3 ) an dwoul dcompl y wit h al l othe r identifie dfedera l an dstat e regulation s a s wel l a s drinkin g wate r

standard s outsid e o f

th e T I zone . PC B an dVO C level s outsid e th e T I zon e ar e currentl y belo w EPA' s standard s bu t a t time s ar e slightl y abov e Maine' s standards
. A s th e concentration s hav e decrease dfollowin g th e 199 7 soi l remova l action , an dactiv e an dpassiv e oi l recovery wil l continue , i t

i s anticipate dtha t

th e Main e standar dwil l b e consistentl y me t outsid e th e T I zon e i n fiv e t o te n years . EP A anticipate s tha t activ e recover y o f

th e oi l unde r

Alternativ e 2 wil l mor e quickl y lowe r

th e PC B an dVO C concentration s i n th e T I zon e tha n jus t th e passiv e recovery provide di n Alternativ e 1
. However , i t i s likel y tha t

a t th e conclusio n o f

activ e recover y th e dissolve dconcentration s withi n th e T I zon e wil l stil l b e abov e th e drinkin g wate r standards
. Becaus e th e RO D Amendmen t waive s federa l an dstat e drinkin g wate r standard s fo r

aportio n o f th e site , EP A sough t

comment fro mth e publi c regardin g thi s durin g th e public commen t period
. 3
. Long-ter

mEffectivenes s an d Permanenc e Thi s criterio n refer s t o th e abilit y o f aremedy t o maintai n reliabl e protectio n o f huma n healt

h an d th e environmen t

ove r tim e onc e th e remedia l actio n i s complete
. Th e origina l remed y woul dhav e provide dlong-termeffectivenes s an dpermanenc e onc e site groundwate r

ha d bee n restore dt o drinkin g wate r quality
. However , sinc e i t wa s demonstrate d tha t th e pum p an d treat

technolog y coul dno t

restor e th e groundwate r

withi n areasonabl e timeframe , ther e wer e concern s tha t the Restrictiv e Covenan t

alon e woul dnot

hav e the ability to , provid e an dmaintai n reliabl e long-ter meffectiveness
. Fo r thi s reason , additiona l institutiona l control s coul db e use di n th e futur e t o ensur e long-ter meffectivenes s an dpermanenc e unde r both alternative s evaluate db y EPA
. Th e long-ter

mprotectio n criterio n woul db e me t b y bot h alternative s EP A evaluated
. I f th e Restrictiv e Covenan t

i s no t effectiv e o r

protectiv e i n th e future , additiona l institutiona l control s wil l b e require db y EPA
. Th e groundwate r monitorin g wil l continu e unde r both alternative s a s lon g a s th e PC B an dVO C concentration s remai n abov e drinkin g wate r quality
. Additionally , operatio n an d maintenanc e activitie s wil l continu e t o ensure th e effectivenes s an d protectivenes s o f th e institutiona l controls
. 4
. Reductio n o f

Toxicity , Mobility , an dVolum e throug h Treatmen t Thi s criterio n contain s thre e measure s o f th e overal l performanc e o f aremedy
. Th e 198 6 amendment s t o th e Superfun dstatut e emphasiz e that , wheneve r possible , EP A shoul dselec t a remed y tha t

use s atreatmen t

proces s t o permanentl y reduc e th e leve l o f toxicity o f

contaminant s a t th e site , inhibi t

o r eliminat e th e sprea do f

contaminant s away fro mth e sourc e o f contamination , an dreduc e th e volume , o r amoun t o f contaminatio n a t

th e site
.

3 4Th e original remed y fo r th e groundwate r

operabl e uni t

use daprove n technology , pum p an d treat , t o reduc e toxicity , mobility , an dvolum e i n th e overburde n an dbedroc k groundwater
. However , a s note delsewhere , th e presenc e o f separat e phas e oi l with PCB s an dVOC s i n bot h th e fracture s i n th e overburde n cla y soi l an d i n th e bedrock , an d th e limite drecharg e o f groundwate r

i n th e contaminate dsourc e are agreatl y limite dth e effectivenes s o f pum p an dtrea t technolog y i n reducin g toxicity , mobility , an dvolume
. Bot h alternative s woul dinclud e th e remova l o f residua l oil
. Alternativ e 1 woul dremov e th e oi l a s i t move s unde r

natura l condition s int o monitorin g wells , wherea s Alternativ e 2 woul dals o emplo y apumpin g syste mt o increas e th e rat e o f th e recovery . Th e recovere doi l i s transporte d offsit e t o alicense dTS D facility
. Usin g activ e recovery unde r Alternativ e 2 , th e volum e o f th e residua l oi l wil l b e reduce dmuc h mor e quickl y the n relyin g o n natura l condition s a s propose di n Alternativ e 1
. I n turn , thi s wil l furthe r decreas e it s mobilit y throug h th e subsurface
. Therefor e Alternativ e 2 provide s th e greates t reductio n o f

toxicity , mobility , an dth e volum e o f contaminant s throug h treatment . 5
. Short-ter

mEffectivenes s Thi s criterio n refer s t o th e likelihoo do f advers e impact s o n huma n health o r th e environmen t

tha t may b e pose ddurin g th e constructio n an d implementatio n o f aremedy
. EP A doe s no t

believ e tha t

th e origina l remed y fo r

groundwate r

pose dsignifican t

short-term effectivenes s concerns . Th e potentia l exposur e o f sit e worker s an d are aresident s t o contaminate dai r

emission s durin g constructio n o f th e extractio n an dre-injectio n well s wa s minimize db y usin g standar dsafety plan s that include dai r

emission s control s an d anetwor k o f ambien t ai r monitor s t o asses s potentia l release s t o th e ai r durin g drillin g operations. Th e implementatio n o f

th e pum p an dtrea t

technolog y likewis e di dno t pos e significan t

short-ter m effectivenes s concerns . Bot h alternative s mee t

th e short-termeffectivenes s criterio n i n simila r ways . Th e implementatio n of

institutiona l control s reduce s site risk s fro mgroundwate r quickly
. The onl y remedia l action s ar e th e long-ter mmonitorin g an dth e oi l recovery , bot h o f whic h hav e bee n ongoin g fo r

years , an d th e samplin g crew s follo w establishe dhealt h an d safet

y procedures
. A s state dabove , th e recovere doi l an dabsorben t material s ar e currentl y transporte dt o alicense d TS D facilit y an dwil l continu e t o b e shippe doffsit e safel y an di n accordanc e with al l legal requirements
. 6
. Implementabilit v Thi s criterio n refer s t o th e technica l an dadministrative feasibilit y o f aremedy , including th e availabilit y o f material s an d service s neede d t o implemen t th e remedy
. Th e origina l groundwate r

remed y wa s implementabl e a s demonstrate db y th e installatio n o f recovery an d re-injectio n well s tha t wer e operate dsuccessfull y durin g th e pilo t pumpin g studies
. 3 5Bot

h alternative s evaluate di n thi s RO D Amendmen t fo r OU- 2 can b e easily implemented
. Th e material s an dequipmen t

neede dfo r

maintenanc e o f

th e site , long-ter mmonitoring , an doi l recover y ar e al l readil y available
. Th e VE Rsyste mi s alread y installe dan dha s bee n operate di n thre e separat e trial s spannin g several months
. Th e Restrictiv e Covenan t i s currentl y i n place
. I f additiona l institutiona l control s ar e needed , the y als o ca n b e readil y implemented
. 7
. Cos t Thi s criterio n include s th e ne t presen t wort h estimate s fo r

capita l (up-front ) an doperatio n an d maintenanc e cost s o f

implementin g eac h alternativ e evaluate dfo r OU-2
. Th e cost s describe d belo w d o no t

includ e previou s site-wid e cost s whic h wer e substantial
. Th e cos t estimate s onl y reflec t thos e cost s tha t

woul db e incurre dhencefort h t o implemen t th e alternative s evaluated
. Th e estimate dtota l presen t wort h cost s associate dwith th e managemen t o f migratio n componen t i n th e 198 9 RO D wa s $679,00 0 wit h operatio n an dmaintenanc e cost s fo r thirt y year s comprisin g $631,00 0 o f

th e total
. I n evaluatin g th e alternative s fo r costs , EP A note s tha t

th e ne t presen t wort h ha s bee n calculate d fo r thirt y years , followin g EP A guidance , wherea s i t i s th e expectatio n o f

al l partie s tha t

th e cleanu p activitie s wil l las t

considerabl y longer
. Th e ne t presen t wort h o f Alternative s 1 an d2 are $622,00 0 an d $1,055,000 , respectively
. 8
. Stat e Acceptanc e Thi s criterio n addresse s whether , base do n it s revie w o f th e dat aderive dfro mth e sit e an d th e Propose dPlan , th e State concur s with , opposes , o r ha s n o commen t

o n th e amendmen t

that EP A ha s selecte dfo r

th e site
. Main e DE P ha s reviewe dth e Jun e 200 2 Propose dPla n t o amen dth e 198 9 Cleanu p Plan an d a draf t o f thi s amendment
. Th e Main e DE P concur s wit h th e remedy chang e wit h certai n conditions
. Thes e condition s hav e bee n addressed
. Th e Main e DE P ha s provide dalette r o f concurrenc e whic h i s provide di n Appendi x C
. 9
. Communit y Acceptanc e Thi s criterio n addresse s whethe r th e publi c concur s wit

h EPA' s propose dAmendment
. Complianc e wit h thi s criterio n i s base do n th e comment s receive da t th e publi c meetin g an d publi c hearing
. Base do n th e publi c informatio n an dpubli c hearin g meeting s an dcomment s receive ddurin g th e publi c commen t

period , i t appear s tha t

th e propose damendmen t ha s community support . 

### X . TH E SELECTE D REMED Y FO ROU- 2 3 6EP A ha s selecte dth e remed y describe dbelo w a s th e bes t balanc e betwee n th e nin e criteria
. Th e selecte dremed y relie s o n institutiona l controls , activ e oi l recovery , an d long-ter mmonitorin g o f overburde n an dbedroc k

groundwater
. Thi s remed y wa s selecte dwithi n th e contex t o f th e determinatio n b y EP A tha t i t i s technicall y impracticabl e t o restor e th e groundwate r fo r alimite d portio n o f th e Sit e withi n areasonabl e timeframe
. Fo r th e amende dcleanu p pla n fo r OU-2 , EP A ha s selecte d aremed y whic h ensure s protectivenes s o f

huma n health an dth e environment , attain s al l federa l an dstat e regulation s with th e exceptio n o f

waivin g drinkin g wate r

standard s fo r

aportio n o f

th e site , provide s long-term an dshort-ter meffectiveness , i s implementable , an dreduce s toxicity , volume , an dmobilit y throug h treatment . Th e amende dcleanu p pla n fo r OU- 2 includes: 1
. Institutiona l control s t o preven t exposur e t o th e contaminate dgroundwate r

• I n 1994 , CM P an d Main e DE P signe daRestrictiv e Covenan t o n aportio n o f

th e propert y whic h prevent s certai n activitie s withou t writte n approva l fro mMain e DE P (se e Figure 4)
. Th e Covenan t

require s CM P t o maintai n th e propert y t o ensur e tha t th e remedy remain s protective
. Th e Covenan t run s with th e lan dan di s bindin g o n al l futur e owners . Th e Restrictiv e Covenan t

wa s recorde da t

th e Kennebe c Count y Registry o f Deed s o n Septembe r 13 , 2002
. I f

th e Covenan t

i s release dprio r

t o th e completio n o f

th e remedy , o r

i f EP A find s tha t i t i s no t effectiv e an dprotective , EP A wil l requir e othe r institutiona l control s b e pu t i n plac e o n th e site
. •A n operatio n an d maintenanc e pla n wil l b e implemente dt o ensur e tha t th e institutiona l control s ar e bein g followed , tha t the y ar e effectiv e an dprotective , an dtha t th e Site i s manage dproperly
. Th e O& M pla n wil l includ e aschedul e fo r monitorin g th e soi l cover , resurveyin g o f

th e designate darea , an dperiodi c samplin g an danalysi s t o ensur e th e integrit y o f th e soi l cove r

ove r th e designate darea . Thi s samplin g wil l coincid e with th e five-year review s an dwil l consis t

o f alimite dnumbe r

o f soi l sample s collecte dfro mabou t 6- 8 inche s belo w th e groun dsurfac e an danalyze dfo r PCBs
. 2
. A combinatio n o f

activ e an dpassiv e remova l o f th e oi l an dassociate dPCB s

• A vacuum-enhancedpumpin g syste mwil l b e use dannuall y t o remov e oi l fro mth e groundwater
. Thi s syste mwil l b e operate do n a n annua l basi s i n lat e summer - earl y fal l unti l i t i s determine dt o b e n o longe r effective
. Criteri at o b e use dt o mak e thi s determinatio n includ e th e following :

appl y th e VE Rt o fou r

well s (101 , 202B , 310B , an d 302B ) i n th e TW A I I are aat leas t onc e ever

y yea r fo r th e nex t fiv e year s (2007)
. Th e necessity an dcondition s fo r continuatio n o f

th e VE Rwoul db e addresse ddurin g th e nex t fiv e 5-yea

r review , schedule dfo r

Septembe r

2007 , an deac h subsequen t 5-yea r revie w period
. Afte r applicatio n o f

th e VE Rt o awell , recovery o f oi l wil l b e observe dove r

a 3 7perio do f u p t o on e week
. I f a"significant " amoun t

o f oi l i s recovere dfro mth e well , th e VE Rwil l b e reapplie dt o th e well
. A "significant " amoun t o f oi l wil l b e define da s a n increas e i n th e amoun t

o f oi l recovere drelativ e t o th e amoun t o f oi l recovere dthroug h passiv e means . Basicall y thi s mean s tha t i f th e VE Ri s effectivel y increasin g th e amoun t o f oi l bein g recovere dfro mawell , i t wil l continu e o n tha t

well
.

• Th e operatio n o f

th e VE Rwil l continu e fo r aperio do f

u p t o tw o month s i f

significan t amount s o f

oi l ar e recovered
. Afte r

thi s tim e weathe r

constraints an drisin g groundwate r elevation s ar e expecte dt o limi t th e effectivenes s o f

th e VER
. I t i s expecte dthat

th e VE Rwil l b e operate dfo r th e nex t fiv e year s an d thi s determinatio n regardin g th e continue doperatio n o f th e VE Ra s par t

o f thi s RO D Amendment

wil l b e mad e i n conjunctio n wit

h th e nex t five-yea r revie w schedule dfo r

summe r 2007
. Thi s componen t

o f th e remed y require s placement o f absorben t material s i n monitorin g well s afte r th e conclusio n o f

th e pumpin g t o absorb an y remainin g residua l oil
. Th e us e o f absorben t material s wil l continu e unti l a s lon g a s i t i s practical , i.e , a s lon g a s oi l i s visibl y detectable
. Betwee n activ e operatio n o f th e VER , th e well s ar e currentl y monitore do n amonthl y basis
. I t i s anticipate dthat

thi s frequenc y wil l b e reduce dt o quarterl y i n th e future
. Al l recovere d oi l an d use dabsorben t

materia l wil l b e dispose do f at alicense dTS D facility
. 3
. Monitorin g th e groundwate r t o demonstrat e that

th e contaminatio n i s no t

expandin g an dtha t natura l processe s wil l continu e t o decreas e th e contaminan t concentrations
.

• Thi s componen t

o f th e remed y require s implementatio n o f along-ter mgroundwate r monitorin g progra mt o trac k dissolve dPC B an dVOCs
. Thi s progra mwil l b e amodificatio n o f th e curren t

monitorin g program .

• I t wil l als o requir e trackin g th e progres s o f attenuatio n b y monitorin g dissolve d contaminan t

level s beyon dth e are awher e th e oi l i s presen t i n th e groundwater
. Thi s monitorin g dat awil l b e use dt o verif y tha t th e dissolve dcontaminan t concentration s ar e decreasing
. •Finall y thi s componen t

o f th e remed y wil l includ e contingencie s shoul dth e groundwate r monitorin g indicat e th e contaminatio n i s movin g beyon dit s curren t limits
. Contingencie s ma y includ e increase dsamplin g frequency , implementatio n o f additional samplin g locations , includin g an y residentia l well s installe do n adjacen t properties , reevaluatio n o f th e conceptua l model , an d increase doperatio n o f th e VER
. 4
. Evaluatin g th e cleanu p approac h t o confir mthat i t i s protectiv e o f

huma n health an dth e environmen t
3 8•A s lon g a s contaminatio n remain s whic h prevent s unrestricte dus e o f th e site , th e Superfun d law require s review s ever

y fiv e year s t o evaluat e th e effectivenes s o f th e implemente d cleanu p plan
. A s par t

o f eac h fiv e yea

r review , EP A wil l revie w th e sit e condition s t o determin e i f

th e cleanu p actio n remain s protective , conside r ne w technologies , an d refin e th e tim e estimate s necessary t o reac h th e groundwate r standards
. I n additio n t o thes e component s fo r OU-2 , monitorin g Rigg s Broo k fo r OU- 3 wil l continu e a s specifie di n th e 198 9 ROD , t o trac k change s i n PC B concentration s an d t o demonstrat e n o unacceptabl e impac t

o n sedimen t

qualit y o r aquati c o r

terrestria l organisms
.


### XI . STATUTORY DETERMINATION S Th e remedia l actio n selecte dherei n fo r implementatio n fo r

O'Conno r

OU- 2 i s consisten t

wit h CERCL A and , t o th e extent

practicable , th e NCP
. A . Th e Selecte d Remed y i s Protectiv e o f Huma n Health an d th e Environmen t Th e selecte dremed y wil l b e protectiv e o f huma n health an dth e environment
. Exposur e t o contaminate dgroundwate r wil l b e prevente dthroug h th e Restrictiv e Covenan t o r othe r institutiona l controls
. Thi s Covenan t include s th e following :

• an y us e o f

th e groundwate r

beneat h th e site i s prohibite dwithou t th e writte n approva l o f Main e DEP ;

• an y activity whic h migh t

disrup t remedia l o r

monitorin g measure s i s prohibite dwithou t th e writte n approva l o f

Main e DEP ; an d

• CM P o r an y subsequen t

owne r shal l maintai n th e sit

e i n aconditio n adequat e t o ensur e th e continue dcomplianc e wit h al l applicabl e standard s an dt o ensur e th e ongoin g adequac y o f th e remediation
. I f othe r institutiona l control s ar e required , the y wil l ensur e th e protectivenes s o f th e remedy
. Activ e recover y o f

PCB-oi l wil l decreas e th e mas s an d volum e o f th e contaminant s o f

concern a s wel l a s reduc e it s mobility
. Long-termmonitorin g o f th e groundwate r

wil l allo w EP A t o trac k th e decreasin g concentration s presen t i n th e overburde n soil s an d bedroc k aquifer
. Ther e ar e n o significan t short-ter mrisk s t o huma n healt h o r th e environmen t

durin g implementatio n o f th e selecte dremedy
. Th e potentia l exposur e o f sit e worker s an d are aresident s durin g th e annua l oi l recover y wil l b e monitore dt o asses s potentia l release s t o th e ai r durin g cleanu p operations
. A s activ e oi l recovery ha s bee n implemente da t th e sit e sinc e 1996 , it s continuatio n a s par t o f th e RO D Amendmen t

remed y i s no t

anticipate dt o pos e an y significan t risk s t o sit e worker s o r

are a residents
.
3 9B
. Th e Selecte dRemed y Attain s o r Appropriatel y Waive s ARAR s ARAR s fo r

th e site wer e identifie ddurin g th e developmen t o f th e 198 9 ROD
. A s apar t o f th e T I Evaluatio n process , arevie w o f curren t ARAR s wa s conducte dan di s .summarize dbelow
. Sectio n 300.43 0 (e ) o f

th e Nationa l Contingenc y Pla n (NCP ) require s tha t on-sit e remedia l action s at CERCL A site s mus t

mee t ARAR s unde r

federa l o r state environmenta l o r

facility sitin g law s unles s ther e ar e ground s fo r invokin g awaiver
. A waive r i s require di f

ARAR s canno t b e achieved
. Othe r

federal an d state advisories , criteria , o r guidance , a s appropriat e (t o b e considere d- TBCs) , shoul db e considere di n formulatin g th e remedia l action
. ARAR s ar e promulgated , enforceabl e federa l an dstate environmenta l o r publi c health requirements
. Ther e are tw o categorie s o f requirements : "applicable " an d "relevant an d appropriate"
. CERCL A doe s no t allo w aregulatio n t o b e considere da s bot h "applicable " an d "relevan t an dappropriate"
. Thes e categorie s ar e define dbelow : Applicabl e Requirement s - Sectio n 300. 5 o f th e NC P define s applicabl e requirement s a s "thos e cleanu p standards , standard s o f control , an dothe r

substantiv e environmenta l protectio n requirements , criteria , o r

limitation s promulgate dunde r Federa l o r

Stat e la w tha t

specificall y addres s ahazardou s substance , pollutant , contaminant , remedia l action , location , o r othe r circumstanc e at

aCERCL A site"
. Relevan t an d Appropriat e Requirement s - Sectio n 300. 5 o f th e NC P define s relevan t

an d appropriat e requirement s a s "thos e cleanu p standards , standard s o f control , an d other

substantiv e environmenta l protectio n requirements , criteria , o r limitation s promulgatedunde r Federa l o r Stat e la w that , whil e no t

'applicable ' t o ahazardou s substance , pollutant , contaminant , remedial action , location , o r

othe r circumstanc e a t

aCERCL A site , addres s problem s o r situation s sufficientl y simila

r t o thos e encountere dat

aCERCL A sit

e that thei r us e i s wel l suite dt o th e particula r site. " T o b e considere d(TBCs ) guidelines ar e non-promulgate dcriteria , advisories , an dguidanc e issue db y th e federa l o r

stat e governments . Alon g with ARARs , TBC s ma y b e use dt o develo p interi mactio n limit s necessary t o protec t huma n healt h an dth e environment
. ARAR s an d TBC s ar e divide dint o thre e categories : chemical-specific , location-specific , an d action-specific
. Thi s sectio n briefl y summarize s th e mos t significan t

chemical , locatio n an d actio n specifi c ARAR s fo r th e remedy an d identifie s thos e fo r whic h atechnica

l impracticabilit

y waive r i s sought
. Chemical-Specifi c ARAR s Chemical-Specifi c ARAR s ar e usuall y health

- o r risk-base dnumerica l value s o r methodologie s which , whe n applie dt o site-specifi c conditions , resul t i n th e determination o f

numerica l value s that establis h th e acceptabl e amoun t o r concentratio n o f

achemical tha t

ma y b e foun din , o r
4 0discharge dto , th e ambien t environment
. Thes e requirement s d o no t conside r th e mixtur e o f chemicals
. A summary o f

chemical specifi c ARAR s i s presente di n Tabl e 6
. Th e federal Maximu mContaminan t Level s (MCLs ) ar e chemical-specifi c ARAR s tha t govern th e qualit y o f

drinkin g wate r

provide db y publi c wate r

supply
. MCL s ar e relevan t an d appropriat e requirement s i n establishin g remediatio n goal s fo r groundwate r

a t th e site an dar e ARAR s outsid e th e T I zone . Th e 199 2 Stat e o f

Main e Maximu mExposur e Guideline s (MEGs ) ar e chemical-specifi c ARAR s tha t ar e health-base dguideline s intende dt o determin e drinkin g wate r qualit y fo r

privat e residentia l wells
. MEG s ar e relevan t an dappropriat e requirement s i n establishin g remediatio n goal s fo r groundwate r

a t th e site
. Main e MEG s wer e revise di n 2000 , bu t hav e no t bee n promulgate dan dtherefore , th e 200 0 Main e MEG s ar e TBCs
. Th e MCL s an dMEG s fo r

whic h atechnica l impracticabilit y waive r wil l appl y ar e note di n th e Tabl e 3 i n Sectio n VII I above
. Location-Specifi c ARAR s Location-specifi c ARAR s ar e restriction s place do n th e concentration s o f hazardou s substances , o r th e conduc t

o f activitie s solel y becaus e the y ar e i n specifi c areas . Th e genera l type s o f location-specifi c ARAR s tha t appl y t o th e site ar e briefl y describe dbelo w an dar e presente di n Tabl e 7
. Several federa l an dstat e ARAR s regulat e activitie s tha t ma y b e conducte di n wetland s an d floodplains
. Regulation s governin g endangere dspecie s a t th e federa l an dstat e level s woul dnee d t o b e considere dfo r

an y propose don-sit e actions
. Th e Main e Natura l Resource s Protectio n Ac t govern s activitie s that

ma y occu r

i n o r adjacen t t o wetland s o r

surfac e wate r

bodies
. Th e Main e Sit e Locatio n Developmen t La w regulate s activitie s tha t ma y adversel y affec t

existin g lan duses , an dsceni c characte r

o r natura l resources , an dneed s t o b e considere di n th e implementatio n o f a n alternative
. ^ N o waive r o f location-specifi c ARAR s i s bein g sough t fo r th e technica l impracticabilit y evaluatio n fo r

th e Site
. Action-Specifi c ARAR s Action-specifi c ARAR s ar e usuall y technology

- o r activity-base drequirement s o r limitation s o n action s take n with respec t

t o hazardou s wastes . Thes e requirement s ar e generall y focuse do n action s take n t o remediate , handle , treat , transport , o r dispos e o f

hazardou s wastes . Thes e action

specifi c requirement s d o no t i n themselve s determin e th e remedia l alternative ; rathe r the y indicat e ho w aselecte dalternativ e mus t b e implemented
. Th e genera l type s o f action-specifi c ARAR s tha t

appl y t o th e sit e ar e briefl y describe dbelo w an dar e presente di n Tabl e 8
. Th e Toxi c Substance s Contro l Ac t (TSCA ) regulate s th e marking , storage , disposal an d cleanu p

4 1o f

spill s o f PCB s greate r

tha n 5 0 pp mPCBs
. I n addition , th e Main e Hazardou s Wast e Managemen t

Rule s als o regulat e treatment , storag e an d disposa l o f hazardou s wastes , includin g PCBs
. Thes e regulation s woul dnee dt o b e i n th e implementatio n o f an y alternativ e that

include s th e removal and/o r

treatmen t o f contaminate dgroundwate r an dresidua l oil
. N o waiver fo r action-specifi c ARAR s i s bein g sough t fo r th e technica l impracticability evaluatio n fo r

th e Site
. C . Th e Selecte d Remedia l Actio n i s Cost-Effectiv e Th e selecte dremed y i s cost-effectiv e sinc e i t provide s overal l effectivenes s proportiona l t o it s cost . Th e projecte dne t

wort h cost s ove r

thirt y year s fo r

th e tw o amendmen t

alternative s evaluate d wer e $0.62 2 million fo r

Alternativ e 1 an d$1.05 5 millio n fo r Alternativ e 2
. Th e selecte dremed y Alternativ e 2 activel y remove s contaminatio n throug h treatmen t fro mth e groundwate r

wherea s Alternativ e 1 doe s no t

includ e activ e removal
. Additionally , EP A believe s th e actua l cos t differenc e fo r

th e tw o alternatives i s no t a s great at i t appears . Thes e cost s hav e bee n calculate d base do n thirt y years , ye t

i t i s anticipate dtha t

th e long-termmonitorin g fo r OU- 2 wil l continu e considerabl y longer
. However , b y activel y removin g th e oi l o n a n annua l basi s a s lon g a s i t i s practical , EP A expect s thi s wil l shorte n th e tim e perio dfo r groundwate r

restoratio n an d thereb y requir e les s long-ter mmonitorin g compare dt o Alternativ e 1
. D . Th e Selecte d Remed y Doe s Utiliz e Permanen tSolution s an d Alternativ e Treatmen to r Resourc e Recover y Technologie s t o th e Maximu m Exten tPracticabl e Th e selecte dremed y provide s apermanen t solutio n an dalternativ e treatmen t o r resourc e recover y technologie s t o th e maximu mexten t practicabl e fo r

th e separat e phas e oi l throug h activ e oi l recovery . Throug h institutiona l controls , th e groundwate r i s isolate dfro mhuma n us e an dthu s prevent s exposure . Extrapolation s o f groundwate r

monitorin g dat adowngradien t o f th e T I zon e indicat e tha t

th e groundwate r

beyon dth e T I zon e wil l attai n th e cleanu p standard s withi n th e nex t te n years . Throug h th e activ e recovery o f oi l o n a n annua l basis , th e selecte dremed y reduce s th e mas s o f contaminatio n mor e quickl y tha n natura l attenuatio n processes . Followin g th e complete dSCRA , th e activ e oi l recovery seek s t o permanentl y furthe r reduc e th e sourc e o f

contaminatio n fo r

th e downgradien t

groundwate r

an dRigg s Brook
. E . Th e Selecte d Remed y Doe s Satisf y th e Preferenc e fo r Treatmen ta s a Principl e Elemen t Th e selecte dremed y doe s us e treatmen t o f th e PC B oil-contaminatedgroundwate r a s aprincipl e elemen t o f th e remedy
. Th e recovere doi l i s transporte doffsit e t o alicense dTS D facility
.

4 2F . Fiv e Yea r Review s

Becaus e thi s amendmen t

woul dresul t

i n contaminant s remainin g onsite , EP A wil l revie w th e sit e a t leas t onc e ever y fiv e year s afte r

th e initiatio n o f

th e remedia l actio n a t

th e site t o assur e tha t

th e remedia l actio n continue s t o b e protectiv e o f huma n healt h an dth e environment
. Thi s revie w wil l b e consisten t

with th e CERCL A §121(c ) applicabl e fo r five-year sit e review s i n effec t

a t th e tim e o f th e review
. Th e firs t

five-year revie w fo r

th e sit e wa s triggere db y th e star t o f th e sourc e contro l remedia l actio n an dwa s complete di n Septembe r 2002
. 

### XII . DOCUMENTATIO N O F N O SIGNIFICAN T CHANGE S Th e Propose dPlan t o amen dth e 198 9 ROD , a s i t pertaine dt o th e MOM , wa s release dfo r publi c commen t i n Jun e 2002
. Th e propose dchang e call s fo r attainin g protectivenes s o f huma n healt h throug h institutiona l control s an d long-termmonitorin g rathe r tha n attainin g protectivenes s o f huma n health throug h restoratio n o f th e sit e groundwate r

throug h activ e remedia l action
. Th e amende dcleanu p plan doe s includ e activ e recover y o f th e PC B laden-oil , thereb y providin g treatmen t a s acomponen t

o f th e remedy
. EP A determine dthat , base do n comment s receive ddurin g th e publi c commen t perio dwhic h conclude do n Jul y 19 , 2002 , n o significan t chang e i s neede dto th e propose d amende dcleanup plan
. EP A ha s prepare daresponsivenes s summar y t o addres s th e comment s receive ddurin g th e publi c comment

period
. Th e responsivenes s summary i s attache d a s Appendi x A
. 

### XIII . STAT E ROL E Th e Main e Departmen t

o f Environmenta l Protectio n ha s reviewe dth e remed y chang e an d concur s with th e selecte dremed y describe di n Sectio n X o f thi s Amendment
. A cop y o f th e Stat e concurrenc e lette r

i s attache da s Appendi x C
.

4 3Septembe r 200 2 RO D Amendmen t

F . O'Conno r Superfun d Site Tabl e 1 : Compariso n betwee n 198 9 RO D an d 200 2 RO D Amendmen t 198 9 RO D - Groundwate r component s #1 : temporar

y institutiona

l controls
. Thi s woul dpreven t

exposure t o site groundwate r whil e remediatio n wa s underway
. #2 : pump-and-trea

t system . Th e appropriate sizin g o f th e system , includin g th e numbe r o f extractio n wells , pumpin g rate , treatment component s suc h a s granula r activate d carbon , san d filters , ai r

stripper , an d numbe r

o f recharg e well s wa s t o b e determine d durin g th e remedia l desig n phase
. #3 : anetwor

k o f monitorin g wells
. Th e well s use d i n th e R I woul d b e assesse d an d augmente d wit h additional well s i n both overburde n soi l an d bedrock
. #4 : Rigg s Brook

sedimen t an d biot amonitoring
. Broo k sediment s wer e t o b e monitore d yearl y fo r te n year s to asses s PC B concentrations
. Biot asamplin g wa s t o occu r fiv e year s afte r initiatio n o f

th e monitoring
. #5 : five-yea

r reviews
. Th e progres s towar d restoratio n o f

th e site groundwate r

an d th e target clea n u p goa l fo r th e sedimen t

wer e t o b e assesse d durin g each five-yea r review
. 200 2 RO D Amendmen tfo r OU- 2 # 1 permanent

institutiona

l controls
. Wit

h th e 199 4 BSD , CM P an d Main e DE P signe d a restrictiv e covenan

t whic h prevente d certai n activitie s a

t th e site withou t

writte n approval o f Main e DEP
. #2 : annual applicatio n o f

th e VE Rsystem . Th e VE Rha s bee n operate d thre e time s post-ROD , recoverin g PCB-lade n oi l fro mth e overburde n an dbedrock
. Th e VE Rwil l b e applie d annuall y i n TW A I I are awell s t o recover a s muc h oi l a s i s practical
. # 3 monthl y monitorin g o f

oi l level s i n TW

A II well s an d remova

l usin g absorben t

materials
. Betwee n th e annua

l operation s o f

th e VER , th e TW A I I wil l b e monitore d fo r separate phas e oil
. Detecte d oi l wil l b e removed usin g absorben t material
. I t

i s expecte d that monitorin g frequenc y wil l decreas e a s th e amoun t o f oi l drainin g int o th e well s decreases
. #4:long-ter

mmonitoring
. I t

wil l b e performe d t o trac k contaminant

level s i n th e T I zon e an d outsid e it
. #5 : Rigg s Broo k

sediment an d biot amonitoring
. I t wil l continu e a s OU-3 , establishe d i n 199 6 #6 : five-yea

r reviews
. Review s wil l b e conducte d to ensur

e tha t th e sit e remed y fo r al l thre e OU' s remain s protective
.Septembe r 200 2 RO D Amendmen t

F . O'Conno r Superfun d Sit e Tabl e 2 : PC S Result s - TW A I I
PC B Result s 0/g/L ) - TW A I I Samplin g Dat e
3/9 8 6/9 8 9/9 8 12/9 8 3/9 9 6/9 9 9/9 9 3/0 0 9/0 0 4/0 1 9/0 1 

## ow 202 B N D N D N S N D 0.7 9 N S N S N S N S 0.3 5 N S RO D Cleanu p Standar d

OW - OW 204 B 30 1 B N D N D 0.6 4 Jl. O N D 1.1 7 N S N S 0.6 2 N D N S 5. 6

1. 2 1. 7 7. 1 3. 1 2. 9 N S N S 8. 6 3. 5 N S 0. 5 //g/ L 

## ow 302 B 2. 5 3 2 1,50 0 8,90 0 93 0 71 0 N S N S 8. 6 4 4 N S RW-10 1

2. 3 1. 5 N S N S 2.3 2 N S N S N S N S 0.1 2 N S Numbe r o f

Exceedance s 3 3 5 4 4 5 5 5 5 2 5

N D - no n detecte d abov e PQL s N S - no t sample d du e t o presenc e o f oi l i n wel l (considere d an exceedance ) J - estimate du e t o th e percen t differenc e o f

continuin g calibratio n greate r tha n 15%
. Bol d - RO D exceedanc eSeptembe r 2002 RO D Amendmen t

F . O'Conno r Superfun d Sit e

Tabl e 3 : Chemical-Specifi c ARAR s fo r T I Waive r Contaminan t O f Concer n

Benzen e Chlorobenzen e 1 ,2-Dichlorobenzen e 1 ,3-Dichlorobenzen e 1,4

- Dichlorobenzen e 1,2,3

- Trichlorobenzen e 1,2,4

- Trichlorobenzen e 1,3,5

- Trichlorobenzen e PCBs 1 200 1 Maximu m

Groundwate r Concentratio n (//g/L ) an d Locatio n 8 - OW-302 B 24 0 - OW-302 B 21 0 - OW-302 B 16 0 - OW-302 B 72 0 - OW-302 B 9 8 -OW-302 B 77 0 - OW-302 B
no t analyze d fo r 4 4 - OW-302 B MC L

(//g/L )

5 10 0 60 0 N S 7 5 N S 7 0 N S 0. 5 199 2 ME G (^g/L ) 5 4 7 8 5 8 5 2 7 N S 7 0 4 0 0.05 1989 RO D Targe t

Cleanu p Level s (/^g/L ) 5 n o RO D standar d n o RO D standar d n o RO D standar d 2 7 n o RO D standar d
n o RO D standar d
n o RO D standar d 0. 5
1 detectio n limi t

varie s wit

h locatio n an d are generall y greate r than th e 199 2 MEG
. N S - n o standardSeptember 2002 RO D Amendmen t F
. O'Conno r

Superfun dSite Tabl e 4 : Gallon s o f

Oi l Recovere d Fro mTW A I I Are aWell s
Perio d Pum p Tes t

- VE R VE RPhase s I & I I Sourc e Contro l Passiv e Collectio n VE RPhas e II I Pos t VE RPhas e II I Tota l 1992-199

4 1996-199 7 199 7 1997-200 1 200 1 2001-200 2 

## ow 202 B 15. 8 0. 0 0. 0 2. 1 1. 9 0. 1 19. 9 OW

204 B 0. 0 0. 0 0. 0 0. 1 0. 0 0. 0 0. 1 OW

30 1 B 8. 3 0. 0 0. 0 0. 2 4. 6 0. 0 13. 1 OW-302B

5. 7 0. 0 0. 0 2. 3 10. 1 1. 7 19. 8 RW

10 1

— 26. 6 N A 2. 4 3. 2 0. 1 32. 3 Tota l

29. 8 26. 6 0. 0 7. 1 19. 8 1. 9 85. 2September 200 2 RO D Amendmen t F
. O'Conno r

Superfun d Site Tabl e 5 : Summar y o f

Groundwate r

Monitorin g Result s Modifie dMetho d 68 0 Analyte s
Tota l Mon o C B Tota l DiC B Tota l TriC B Tota l TetraC B Tota l PentaC B Tota l HextaC B Tota l HeptaC B Tota l OctaC B Tota l NonaC B DecaC B (#209 ) Tota l PC B Tota l PC B & EMP C MW

106 A 0<S/L ) N D N D N D N D N D N D N D N D N D N D N/ A N/ A MW-106 B

(MS/L ) 0.004 0.0 1 0.0 1 0.0 2 N D N D N D N D N D N D 0.05 0.0 5 MW-50 3

(^g/L ) 0.00 4 0.0 3 0.0 2 N D N D N D N D N D N D N D 0.0 6 0.0 9 MW-508 B

(A*g/L ) 0.00 8 0.0 1 N D N D N D N D N D N D N D N D 0.0 2 0.0 2 MW-104 B

0*8/L ) EMPC * 0.04 N D N D N D N D N D N D N D N D 0.0 4 0.07 OW-201 B

G*B/L ) 0 0.05 N D N D N D N D N D N D N D N D 0.0 6 0.07
Notes : EMP C - Estimate d Maximu mPossibl e Concentratio n * - EMPC=0.0 3C U

a C/ 3



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Afte rSourc e Contro l 20562 1 03\mode l afte r - WOODARD&CURRA NO'CONNO RSUPERFUN D SIT E OPERABL E UNIT- 2 Septembe r 200 2 RO D AMENDMEN T
APPENDI X A - RESPONSIVENES S SUMMAR Y

Comment s Receive d o n th e Jun e 200 2 Propose d Pla n fo r th e O'Conno r Sit e 1
. Comment s fro mCommunit y Member s N o comment s wer e receive d fro mth e communit y durin g th e Jul y 9 , 200 2 hearin g fo r th e Propose d Plan
. Severa l comment s wer e voice d durin g th e informatio n meetin g hel d o n Jun e 24 , 200 2 an d ar e summarize d below
. Community member : I n discussin g th e technica l impracticabilit y o f removin g th e oil , differen t technologie s wer e suggeste d whic h shoul d perhap s b e considere d t o clean u p th e residua l oil
. EPA' s Response : Althoug h thes e suggestions , includin g th e controlle d blastin g o f th e bedroc k

a s woul d b e don e i n aquarr y operation , wer e no t looke d a t

i n th e T I evaluation , EP A believe s th e difficultie s pose d b y th e geolog y an d hydrolog y o f th e site woul d b e th e sam e a s fo r an y o f th e eightee n technologie s considere d i n th e TI
. Thes e limitation s include : residua l oi l tie d u p i n fracture s i n th e claye y soil s an d i n th e bedrock ; limite dgroundwate r

recharg e t o th e sourc e are as o tha t ther e i s limite d flushing ; an d th e relativel y impermeabl e cla y limit s th e effectivenes s o f in-situ applicatio n o f

oxidizin g agent s o r othe r compounds
. Th e possibility o f

furthe r excavatio n o f

th e soi l with th e residua l oi l wa s evaluate d a s par t o f th e T I process . I n away , i t

pose d asimila r

questio n tha t

woul d b e aske d fo r

remova l o f

th e bedrock : ho w woul d th e limit s o f

excavatio n (o r

blasting ) b e determined ? Th e sourc e contro l effor t showe d throug h extensiv e testin g tha t th e cleanu p standard s fo r th e soil s wer e met. I n man y cases , th e result s wer e belo w th e laborator y detectio n limit
. S o wit h th e soil s alread y belo w th e detectio n limit , samplin g woul d no t provid e ametho d t o determin e th e exten t o f an y excavatio n (o r blasting)
. EP A believe s thi s woul d lea d t o arbitrar y excavatio n an d henc e i t woul d b e difficul t t o implement , difficul t

t o estimat e costs , an d difficul t t o provid e a n approac h t o asses s it s effectiveness
. Consequently , thi s alternativ e wa s screene d ou t durin g th e T I evaluation
.Communit y member : Several comment s wer e mad e tha t th e nin e criteri ause di n selectin g a remed y neede dt o b e expande dt o ten , t o loo k a t th e impac t

o f aSuperfun dsite o n propert y values
. Additionally , ther e wa s th e desir e tha t EP A direc t

th e City o f

August at o provid e ta x relie f fo r th e surroundin g properties
. EPA' s Response : EP A i s awar e o f concern s raise dat

thi s sit e regardin g th e impac t

o f havin g a Superfun dsite a s aneighbo r - thi s i s aconcer n hear dacros s th e country . EP A ha s mad e change s i n it s policie s regardin g it s approac h t o adjacen t propertie s wher e contaminatio n ha s com e t o b e located , an dEP A ha s studie dth e economi c impac t o f Superfun dsite s o n propert y values , bu t a s pointe dou t

b y Main e DE P a t

th e publi c meeting , th e Superfun dla w doe s no t provid e fo r

an y metho dt o addres s thi s issue
. Thi s issu e ma y b e mor e properl y addresse do n th e stat e an dloca l levels
. However , EP A hope s tha t b y addressin g th e problem s a t th e Sit e i n awa y tha t

protect s huma n health an dth e environmen t i n th e lon g ter mther e wil l ultimatel y b e apositiv e impac t i n th e community
. Communit y member : Several long-tim e communit y member s aske dabou t th e impac t

o n Rigg s Brook , tyin g i n thei r

recollection s o f

oi l bein g visibl e i n th e broo k an dfar downstrea mo f

th e site
. I n addition , question s were aske dregardin g th e appropriatenes s o f samplin g fis h whe n perhap s othe r organism s migh t

provid e abette r

indicatio n o f

PCB-contaminatio n EPA' s Response : EP A acknowledge s tha t condition s a t

th e O'Conno r

propert y impacte dothe r areas , suc h a s Rigg s Brook
. However , th e curren t dat aha s indicate dtha t

th e PC B concentration s ar e quit e lo w wher e groundwate r discharg e t o Rigg s Broo k i s occurrin g an d tha t

ther e doe s no t appea r t o b e an y mor e overlan dtranspor t fro mth e sourc e are at o Rigg s Brook
. Monitorin g wel l MW-106 B i s abedroc k wel l locate di n th e Rigg s Broo k wetland s an d i s a flowin g artesia n wel l - tha t is , wate r flow s ou t o f th e wel l hea dat

th e groun dsurface
. Samplin g fo r th e pas t severa l year s hav e show n lo w level s o f contaminatio n whic h ar e belo w th e RO D performanc e standards
. Yearl y sedimen t samplin g ha s indicate dtha t PC B concentration s ar e typicall y belo w th e trigge r

leve l o f 5 pp man dofte n belo w th e clea n u p goal o f 1 ppm . Analysi s o f th e dat asuggest s tha t

th e concentration s i n bot h groundwate r an dsedimen t

ar e decreasin g an d EP A anticipate s tha t

th e concentration s wil l continu e t o decreas e followin g th e sourc e contro l remedial action
. Th e us e offis h rathe r

tha n othe r

organism s a s a n indicato r o f PC B s wa s determine da t

th e tim e o f th e 198 9 ROD
. Personne l fro mU.S
. Fis h an dWildlif e Servic e (USFWS ) an dNationa l Oceani c Atmospheri c Administratio n (NOAA) , a s natura l resourc e trustees , wer e involve dwith thi s aspec t o f th e remed y selection
. A s the y ar e th e individual s with th e expertis e i n thi s field , selectio n offis h wa s base do n thei r knowledg e o f

PC B bioaccumulation
. Personne l fro m USFW S continu e t o b e involve dwith th e Rigg s Broo k monitorin g a s wel l a s EP A an d Main e DE P ecologica l ris k

assessors . I t

i s note dtha t

several specie s offis h hav e bee n collecte da s par t o f th e monitorin g program . Communit y member : Concern wa s raise dabou t th e prospec t

tha t contaminate dgroundwate r ma y 2pas s beyon dth e CM P propert y t o potentiall y impac t other properties
. EPA' s Response : Th e highes t priority i n selectin g aremedy i s t o ensure that i t i s protectiv e o f huma n health a s wel l a s th e environment
. Wit h th e acknowledgmen t tha t i t i s technically impracticabl e t o clea n u p th e groundwate r beneat h aportio n o f

th e site , EP A mus t

selec t a remed y tha t

prevent s furthe r

migratio n o f

th e contamination , an dMain e DE P strongl y agree s with this
. EP A believe s th e selecte dremed y doe s this
. Concentration s a t monitorin g well s MW-106 A an dMW-106B , locate di n th e Rigg s Broo k wetlands , plu s th e well s downgradien t o f th e TWA-I I are ahav e bee n meetin g th e performanc e standard s se t i n th e RO D fo r

th e pas t several years . EP A believe s tha t th e groundwate r

syste mha s reache dequilibriu man dtha t contaminatio n wil l no t

mov e beyon dth e CM P property . However , shoul dth e concentration s chang e i n thes e wells , an dresidentia l well s b e installe di n adjacen t properties , the n EP A woul d hav e thes e well s tested
. 2
. Comment s fro mMain e Departmen t o f Environmenta l Protectio n A t th e hearin g fo r

th e Propose d Plan , Main e DE P entere d astatement int o th e sit

e record
. Th e Stat e note dth e followin g concern s an dstate dtha t thei r concurrenc e o n th e RO D amendmen t wa s contingen t o n thes e concern s bein g addressed
. Main e DEP : USEPA mus t bette r identif y an d defin e th e criteri afo r discontinuin g us e o f

th e VE R system . EPA' s Response : I n th e Propose dPlan , EP A state dth e activ e recovery o f oi l usin g th e VE R woul dcontinu e o n a n annua l basi s a s lon g a s i t wa s practical
. Thi s RO D amendmen t provide s mor e detai l regardin g th e VE Rapplication
. I t set s fort h aframewor

k unde r whic h th e VE Rwil l operate , state s tha t

i t wil l b e operate dfo r

th e nex t fiv e years , an dtha t

th e reevaluatio n o f

it s operatio n wil l b e tie di n wit h th e nex t five-year revie w schedule dfo r

summe r 2007
. Main e DEP : Al l sit

e wor k wil l b e performe di n complianc e wit h th e revise d cleanup plan an d al l applicabl e standar doperatin g procedures , laws , an dregulations
. EPA' s Response : Al l wor k performe donsit e wil l follo w approve dwor k plan s an dal l applicabl e requirements
. Main e DEP : MEDE P wil l b e give n at leas t 2 week s notic e prio r

t o eac h samplin g event . EPA' s Response : Thi s wil l b e addresse di n an y enforcemen t agreemen t

tha t i s entere dint o t o conduc t th e remed y selecte di n thi s RO D Amendment
. Main e DEP : I t

mus t b e periodicall y demonstrate dthat ther e i s acontinuou s twelv e inche s o f clea n soi l ove r

th e Designate dArea
. Th e detail s o f suc h demonstratio n wil l b e establishe dprio rt o th e finalizatio n o f th e RO D Amendment
. EPA' s Response : A s par t

o f th e chang e i n th e soi l remedy , a s documente di n th e 199 4 ESD , twelv e inche s o f

clea n soil were to b e place dove r th e designate darea . Thi s soil , define da s containin g les s tha n on e pp mo f PCBs , wa s t o b e brough t

i n fro moffsite
. Concurren t with th e ESD , Main e DE P an d CM P signe daRestrictiv e Covenan t whic h state s tha t

CM P o r subsequen t owne r "shal l maintai n al l drainag e ways.. . permeabl e o r imperviou s cap s o r

cover s (includin g area s covere db y topsoi l o r othe r clean fill) " EP A agree dt o addres s thi s issu e concurrentl y wit h th e TI evaluation
. A s note di n Sectio n IV
. Scop e an dRol e o f

Operabl e Unit , o f

thi s RO D Amendment , operatio n an dmaintenanc e wil l includ e provision s fo r

periodi c monitorin g o f

th e soi l cove r

a s wel l a s rando msamplin g o f th e surfac e soil s t o b e performe da t th e tim e o f

th e five-year

reviews
. Main e DE P indicate dthi s wa s a n acceptabl e resolutio n fo r thi s issue
. Main e DEP : Clarify , b y incorporatio n int o th e RO D Amendment , tha t th e clean u p goal fo r

PCB s i n sedimen t

i s actuall y 1 ppm , no t

5 ppm . However , MEDE P agree s tha t th e 5 pp mtrigge r

leve l fo r remedia l actio n i s acceptable
. EPA' s Response : EP A ha s clarifie di n Sectio n IV
. Scop e an d Rol e o f Operabl e Uni t

o f thi s RO D amendment

that th e clea n u p goa l fo r PCB s i n Rigg s Broo k

an d associate dwetlan d sediment s i s 1 ppm . A revie w o f

th e 199 1 Consen t

Decre e an d th e 199 4 Revise dStatemen t o f Wor k foun dtha t neithe r documen t

provide s an y criteri at o defin e aho t spo t excavation
. Similarly , th e approve d Octobe r 199 7 Fina l Rigg s Broo k

Sedimen t an dBiot aSamplin g an dAnalysi s Pla n i s als o silen t o n thi s issue
. T o clarif

y this , th e clea

n u p goa l fo r Rigg s Broo k

an d associate d wetlan dsediment i s 1 ppm , bu t

shoul daho t

spo t excavatio n occur , th e exten t o f tha t excavatio n woul db e t o les s tha n 5 ppm . Thi s i s consisten t

wit h th e inten t

o f th e 198 9 RO D t o protec t ecologica l receptors . A s note di n th e 198 9 ROD , i n additio n t o th e clea n u p goal fo r

sediments , th e trigge r

fo r additional samplin g i s als o tie d t o th e goa l o f les s tha n 2 pp mfo r

PCB s i n fis h tissu e samples
. Shoul dthi s samplin g indicate greater than 2 pp m"then amor e rigorou s samplin g effor t o f suc h contaminatio n wil l b e conducte dt o determin e th e nee dfo r and/o r exten t o f furthe r remedial actio n t o b e undertake n withi n Rigg s Brook , i f any"
. (198 9 ROD , pag e 47 ) Main e DEP : Al l significan t erosio n occurrin g i n th e Designate dAre ao n site wil l b e addresse di n atimel y manne r

t o preven t

exposur e t o level s o f

PC B abov e 1 pp man dlea dabov e 24 8 ppm . EPA' s Response : Se e th e respons e abov e regardin g maintenanc e o f th e soi l cover .

• Comment s fro mth e Settlin g Part y Centra l Main e Powe r

Co
. (CMP ) provide dcomment s durin g th e publi c commen t perio dfo r

th esite recor di n respons e t o tw o o f Main e DEP' s comments . CM P note di t support s th e amende d RO D fo r th e O'Conno r

site
. CMP : Cove r

Soi l Effectiveness
. Th e Sourc e Contro l Remedia l Actio n (SCRA ) require dtha t a 12-inc h cove r

o f soi l containin g les s tha n 1 pp mo f PCB s b e place dove r

th e Designate dAre a, th e portio n o f

th e site wher e residua l PC B concentration s i n th e soi l coul db e u p t o 1 0 ppm . Tha t cover soi l wa s place ddurin g SCRA , an d acove r cro p o f vegetatio n wa s establishe dt o stabiliz e th e soi l an dcontro l erosion
. Th e operatin g plan require s periodi c inspection s o f th e site b y CM P t o identif y an y area s o f

erosion , an d remedia l actio n t o b e take n t o repai r thos e areas . T o addres s th e concern tha t

long-ter mgradua l erosio n coul dreduc e th e thicknes s o f soi l cove r i n som e area s withou t bein g visuall y obvious , discussion s were hel dwith Main e DE P an d EP A t o develo p a samplin g progra mfo r

th e soi l cover . EPA' s Response : A s state dabove , operatio n an dmaintenanc e wil l includ e confirmator y samplin g o f

th e soi l cove r

coinciden t

wit h th e five-year

review s fo r

th e site
. Te n location s wil l b e randoml y generate dfo r sampling , usin g th e gri dnode s fro mth e SCRA
. Composit e sample s fro m4 - 8 " belo w grad e wil l b e collecte dan danalyze dfo r PCBs
. Shoul dth e result s b e abov e 1 ppm , EPA , Main e DEP , an d CM P wil l determin e appropriat e step s t o take
. CMP : Rigg s Broo k

PC B Concentrations
. Th e U S Fis h an dWildlif e Servic e (USFWS ) evaluatio n o f

Rigg s Broo k

discusse di n th e 198 9 RO D suggeste datarge t cleanu p leve l fo r

PCB s o f 1 ppm . However , th e RO D selecte daremed y fo r th e site tha t

allowe dth e existin g maximu m o f 5 pp mPCB s i n th e sedimen t t o remai n becaus e th e short-termimpact s o f excavatio n woul db e more damagin g t o th e wetlan darea . Th e selecte d remedy require dtha t a10-yea r monitorin g progra mb e instituted , an dtha t amor e rigorou s samplin g effor t b e undertake n i f

samplin g foun d sedimen t value s abov e 5 pp mo r

fis h tissu e sample s abov e 2 ppm . Th e result s o f thi s mor e rigorou s samplin g woul db e use dt o determin e i f additiona l remediatio n o f

Rigg s Broo k

wer e t o b e required
. Becaus e excavatio n i n Rigg s Broo k coul dcaus e short-ter mdamag e t o th e ecosystem , a s recognize db y th e ROD , CM P believe s th e limit s o f an y remediatio n shoul db e establishe dwit h respec t

t o meetin g th e 5 pp mtarge t leve l fo r PCBs , an dno t

necessaril y th e 1 pp mtarge t

suggeste db y USFW S i f

doin g s o create s a n unacceptabl e short-termimpac t t o Rigg s Brook
. EPA' s Response : EP A agree s that th e limi t o f an y excavatio n base do n a n exceedanc e o f 5 pp m woul db e t o ge t

belo w 5 ppm . However , th e possibilit y exist s tha t th e level s identifie di n fis h tissu e samplin g coul db e greate r tha n 2 pp mye t

th e sedimen t

dat ab e belo w 5 ppm . Shoul dsuc h asituatio n arise , the n th e triggerin g o f furthe r samplin g with possibl e remedia l action s i s appropriate
.O'CONNO RSUPERFUN D SIT E OPERABL E UNI T 2 Septembe r 200 2 RO D AMENDMEN T
APPENDI X B - ADMINISTRATIV E RECOR D INDE X

4 FEASIBILIT Y STUD Y (FS )
1 FAC T SHEET EP A PROPOSE S T O AMEND TH E CLEAN-U P PLA N FO RTH E F O'CONNO R SUPERFUN D SIT E AUTHO RU S EP A REGIO N 1 DO C I D 3249 9 06/01/200 2 1 5 PAGE S
2 REPOR T TECHNICA L IMPRACTICABILIT Y EVALUATIO N FO ROU- 2 MANAGEMEN T O F MIGRATIO N (WIT H TRANSMITTAL ) [ 1 O F 2 ] T O CENTRAL MAINE POWE RCOMPAN Y AUTHO RWOODARD & CURRA N IN C DO C ID 3187 7 06/01/200 2 13 5 PAGE S
3 REPOR T TECHNICA L IMPRACTICABILIT Y EVALUATIO N FO ROU- 2 MANAGEMEN T O F MIGRATION , APPENDICE S [ 2 O F 2 ] T O CENTRA L MAINE POWE RCOMPANY AUTHO RWOODARD & CURRA N IN C DO C I D 3188 1 06/01/200 2 30 3 PAGE S

6 REMEDIAL DESIGN (RD )
1 REPOR T MANAGEMEN T O F MIGRATIO N FLOATIN G FREE PRODUC T OI L STUD Y AUTHO RALTO N P DAVIS , GE I CONSULTANT S IN C JOANNE O MORIN , GE I CONSULTANT S IN C MURIEL S ROBINETTE , GE I CONSULTANT S IN CDO C I D 3192 5 02/14/199 3 7 9 PAGE S

2 REPOR T REMEDIAL DESIGN/REMEDIA L ACTIO N REVISE D STATEMEN T O F WOR K AUTHO RU S EP A DO C ID 3207 8 10/20/199 4 5 0 PAGE S
3 REPOR T MANAGEMEN T O F MIGRATIO N GROUNDWATE RMONITORIN G PROGRA M SAMPLIN G AN D ANALYSI S PLAN , VOLUM E I O F E AUTHO RWOODARD & CURRA N IN C DO C I D 3193 3 12/01/199 6 15 6 PAGE S
4 LETTE RAMENDMENT S T O TH E MANAGEMEN T O F MIGRATIO N SAMPLIN G AN D ANALYSI S PLA N T O ERIN HESKETT , U S EP A REGIO N 1 AUTHO RJAME S M MOODY , WOODAR D & CURRA N IN C DO C ID 3195 3 03/14/200 0 1 0 PAGE S

7 REMEDIAL ACTIO N (RA )
1 REPORT VACUU M ENHANCE D RECOVER Y PILO T TEST , PHAS E 1 INSTALLATIO N AN D OPERATIO N REPORT (WIT H TRANSMITTAL ) AUTHO RWOODAR

D & CURRA N IN C DO C ID 3193 7 12/01/199 6 12 6 PAGE S
2 REPOR T DAT A COLLECTIO N AN D INTERPRETATIO N O F TH E PHAS E 2 OPERATIO N O F TH E VACUU M ENHANCE D RECOVER Y (VER ) SYSTE M A T TH E O'CONNO RSITE I N AUGUSTA , MAINE T O ROS S GILLELAND , U S EP A REGIO N 1 AUTHO RERI C T CARLSON , WOODARD & CURRA N IN C DO C I D 3194 8 06/27/199 7 3 3 PAGE S
3 REPOR T MANAGEMEN T O F MIGRATIO N COMPREHENSIV E EVALUATIO N AUTHO RWOODARD & CURRA N IN C DO C I D 3195 7 08/01/199 7 18 5 PAGE S
4 MEM O FINA

L INSPECTIO N O F TH E SOURC E CONTRO L REMEDIAL ACTIO N T O MAR Y JAN E ODONNELL , U S EP A REGIO N 1AUTHO RROS S GILLELAND , U S EP A REGIO N 1

DO C I D 3199 6 12/01/199 7 2 PAGE S
5 REPOR T WETLAN D CONSTRUCTIO N MONITORIN G REPOR T T O CENTRA L MAINE POWE RCOMPAN Y AUTHO RSMAR

T ASSOCIATE S DO C I D 3199 2 03/12/199 8 4 9 PAGE S
6 REPOR T FINA

L SOURC E CONTRO L REMEDIAL ACTIO N REPOR T [ 1 o f 2 ] AUTHO RWOODAR

D & CURRA N IN C DO C I D 3198 5 09/01/199 8 42 1 PAGE S
7 REPOR

T FINA L SOURC E CONTRO L REMEDIA L ACTIO N REPORT [ 2 o f 2 ] AUTHO RWOODARD & CURRA N IN C DO C I D 3199 1 09/01/199 8 35 8 PAGE S
8 LETTE ROI L STUD Y I N TH E UPLAN D MARS H ARE A A T TH E CM P O'CONNO RSITE T O RO Y KOSTER , CENTRA L MAINE POWE RCOMPAN Y AUTHO RERI C T CARLSON
. WOODARD & CURRA N IN C DO C ID 3199 7 01/26/199 9 1 9 PAGE S
9 REPORT 199 8 WETLAN D CONSTRUCTIO N MONITORIN G REPOR T T O CENTRA L MAINE POWE RCOMPAN Y AUTHO RSMART ASSOCIATE S DO C I D 3202 8 04/08/199 9 3 1 PAGE S
1 0 REPOR T 199 9 RIGG S BROO K SEDIMENT MONITORIN G REPOR T T O RO Y KOSTER , CENTRA L MAINE POWERCOMPAN Y AUTHO RHENRI J VINCENT , WOODARD & CURRA N IN C DO C I D 3205 9 02/01/200 0 10 3 PAGE S
1 1 REPOR T 199 9 WETLAN D CONSTRUCTIO N MONITORIN G REPORT T O CENTRA L MAINE POWE RCOMPAN Y AUTHO RSMAR T ASSOCIATE S DO C I D 3202 4 08/15/200 0 3 9 PAGE S
1 2 LETTE RCOMMENT S O N 199 9 WETLAN D CONSTRUCTIO N MONITORIN G REPOR T (DATED AUGUS T 15,2000 )T O CORNEL L ROSIU , U S EP A REGIO N 1 ERI N HESKETT , U S EP A REGIO N 1 AUTHO RSTEVE N E MffiRZYKOWSKI , U S DOI/U S FIS H & WILDLIFE SERVIC E DO C I D 3202 2 10/19/200 0 5 PAGE S
1 3 REPOR T 200 0 WETLAN D CONSTRUCTIO N MONITORIN G REPOR T T O CENTRA L MAINE POWE RCOMPAN Y AUTHO RSMAR T ASSOCIATE S DO C I D 3202 0 03/13/200 1 4 3 PAGE S
1 4 LETTE RCOMMENT S O N 200 0 WETLAN D CONSTRUCTIO N MONITORIN G REPOR T (DATE D MARC H 13,2001 ) T O CORNEL L ROSIU , U S EP A REGIO N 1 TERRENC E RCONNELLY , U S EP A REGIO N 1 AUTHO RSTEVE N E MffiRZYKOWSKI , U S DOI/U S FIS H & WILDLIF E SERVIC E DO C I D 3201 2 06/29/200 1 4 PAGE S
1 5 REPOR T DRAF T 200 0 RIGG S BROO K SEDIMEN T AN D BIOT A MONITORIN G REPOR T T O RO Y ROSTER , CENTRA L MAINE POWE RCOMPAN Y AUTHO RHENRI J VINCENT , WOODARD & CURRA N IN C DO C I D 3205 8 07/01/200 1 15 9 PAGE S
1 6 REPOR T REVISE D LONG-TERM GROUNDWATE RQUALIT Y MONITORIN G PROGRA M AN D PHAS E mVACUU M ENHANCE D RECOVER Y O F OI L WOR K PLA N AUTHO RWOODARD & CURRA N IN C DO C I D 3206 1 07/01/200 1 2 8 PAGE S
1 7 REPORT MANAGEMEN T O F MIGRATION , SAMPLIN G AND ANALYSI S SEMI-ANNUA L REPORT AUTHO RWOODAR

D & CURRA N IN C DO C I D 3206 6 10/01/200 1 11 2 PAGE S
1 8 REPOR T DRAFT 200 1 RIGG S BROO K SEDIMEN T MONITORIN G REPOR T AUTHO RWOODAR

D & CURRA N IN C DO C I D 3206 2 12/01/200 1 11 8 PAGE S
1 9 REPOR T DRAF T VERPHAS E mREPOR T AUTHO RWOODAR

D & CURRA N IN C DO C I D 3206 9 12/01/200 1 2 8 PAGE S2 0 LETTE RCOMMENT S O N DRAF T VE RPHAS E mREPOR T

T O TERRENC E RCONNELLY , U S EP A REGIO N 1 AUTHO RWILKE S B HARPER , M E DEP T O F ENVIRONMENTAL PROTECTIO N DO C I D 3207 2 02/16/200 2 2 PAGE S

1 0 ENFORCEMENT/NEGOTIATIO N
1 LITIGATIO N CONSEN T DECREE , UNITE D STATE S O F AMERICA , PLAINTIFF , V CENTRA L MAINE POWERCOMPANY , DEPENDEN T T O JOE C COLLIER , CENTRA L MAINE POWE RCOMPAN Y AUTHO RCYNTHI A S HUBER , U S DEP T O F JUSTIC E ELISS A TONKIN , U S EP A REGIO N 1 JULIE BELAGA , U S EP A REGIO N 1 RICHAR D B STEWART , U S DEP T O F JUSTIC E DO C I D 3207 5 07/26/199 0 8 0 PAGE S

1 3 COMMUNIT Y RELATION S
1 FAC T SHEET O'CONNO RCOMPAN Y MAINE , EPA ID #MED98073147 5 AUTHO RU S EP A REGIO N 1 DO C I D 3208 0 01/01/199 6 3 PAGE S
2 LETTE RLETTE RT O NEIGHBORS/ABUTTER S OUTLININ G TH E CONTINGENC Y REMED Y WIT H A QUESTIONNAIRE AN D TACT S A T A GLANC E SHEET ' [INCLUDIN G FA X TRANSMITTA L SHEET ] AUTHO RRO Y LANE , CENTRA L MAINE POWE RCOMPANY DO C I D 3208 3 03/26/199 6 6 PAGE S
3 MEM O RESPONSE S T O MARC H 22,199 6 NEIGHBOR/ABUTTE RQUESTIONNAIRE T O ROS S GILLELAND , U S EP A REGIO N 1 AUTHO RTERENC E RPEACOCK , CENTRA L MAINE POWE RCOMPAN Y DO C I D 3208 5 06/10/199 6 2 6 PAGE S
4 LETTE RUPDATE O N COMMUNIT Y RELATION S T O KATHLEE N B FULLER , AUGUST A (ME) , CIT Y O F AUTHO RRO Y LANE , CENTRA L MAINE POWE RCOMPAN Y 1 0DO C I D 3199 8 07/10/199 6 2 PAGE S

5 PUBLI C MEETIN G RECOR D SUMMAR Y O F CLEANU P ACTIVITY , PREPARE D FO RSIT E NEIGHBOR S AN D ABUTTIN G LANDOWNER S AUTHO RRO Y LANE , CENTRA L MAINE POWERCOMPAN Y DO C ID 3200 0 07/24/199 6 1 0 PAGE S
6 PUBLI C MEETIN G RECOR D PUBLI C MEETING , AMERICA N LEGIO N POS T 205 , AGEND A AUTHO RRO Y LANE , CENTRA L MAINE POWE RCOMPAN Y DO C I D 3200 2 12/12/199 6 1 2 PAGE S
7 NEW S CLIPPIN G EP A TEST S CON Y ROA D HOME S AUTHO RDAVE CHEEVER , KENNEBE C JOURNA L DO C I D 3200 4 06/26/199 7 2 PAGE S
8 NEW S CLIPPIN G CIT Y JUNKYAR D OFFICIALL Y CLEA N AUTHO RGAR Y J REMAL , KENNEBE C JOURNA L DO C I D 3200 5 11/13/199 7 2 PAGE S
9 NEW S CLIPPIN G WEEKL Y UPDATE , O'CONNO RSUPERFUND CLEAN-U P CELEBRATE D AUTHO RCENTRA L MAINE POWERCOMPAN Y DO C I D 3200 6 1 1 '20/199 7 2 PAGE S
1 0 FAC T SHEET EPA T O REVIE W PROGRES S O F CLEANU P A T O'CONNO RSUPERFUN D SIT E AUTHO RALIC E KAUFMAN , U S EP A REGIO N 1 DO C I D 3200 8 05/08/200 2 2 PAGE S

2 0 RECORD S MANAGEMENT
1 LIS T LIS T O F GUIDANC E DOCUMENT S AUTHO RU S EP A REGIO N 1 DO C I D 3251 9 06/20/200 2 1 PAG E

1 1O'CONNO RSUPERFUN D SIT E OPERABL E UNI T 2 Septembe r

200 2 RO D AMENDMEN T APPENDI X C - STAT E CONCURRENC E LETTE R

1 2STAT E O F MAIN E DEPARTMEN T O FENVIRONMENTA L PROTECTIO N

ANGU S S KING

. JR
. MARTH A KIRKPATRIC K GOVERNO R COMMISSIONE R September 19,200 2

Mr
. Richar dCavagner o Actin g Directo r

- Offic e o f

Sit e Remediatio n an d Restoratio n U S EPA On e Congres s Stree t

- Suit e 110

0 (HBT ) Boston , MA
. 02114-202 3 Regarding : O'Conno r Junkyar dSuperfun dSit e (F
. O'Conno r

Compan y Superfun dSite ) Augusta , Main e

Dea r Mr
. Cavagnero , Th e Main e Departmen t

o f Environmenta l Protectio n (MEDEP ) ha s complete dit s revie w o f th e Recor d o f Decisio n Amendmen t

- Operabl e Uni t

2 - fo r th e F
. O'Conno r

Compan y Superfun dSit e (Site ) i n Augusta , Main e date d Septembe

r 2002
. Base do n thi s revie w th e MEDE P i s please dt o provid e it s concurrenc e on , wit h caveats , th e revise dremed y selecte dfo r

OU-2
. Thi s remedy relie s o n activ e an dpassiv e oi l recovery , lon g ter mmonitorin g o f th e groundwater , an dlan dus e restriction s specifie di n aDeclaratio n o f Restrictiv e Covenant s recorde da t th e Kennebe c Count y Registr y o f Deed s o n Septembe r

13 , 200 2 - Boo k

7058 , pag e 42
. Thi s concurrenc e i s contingen t upo n th e followin g caveats : 1
. Finalize a n Operations an d Maintenance Plan (O&M). Th e O& M mus t

b e finalize dt o th e satisfactio n o f th e MEDEP withi n areasonabl e tim e fram e followin g ou r

concurrenc e wit h th e RO D Amendment
. A draf t O& M wa s submitte dt o MEDE P o n Jun e 6 , 200 2 b y Woodar dan dCurra n (W&C ) o n behal f o f Central Main e Powe

r Compan y (CMP)
. Thi s pla n faile dt o addres s th e monitorin g an d maintenanc e requirement s regardin g th e clea n soi l cove r overlyin g th e Designate dAre a(DA) ; therefore , i t wa s rejecte db y MEDEP
. Th e Designate dAre ai s asubsectio n o f th e propert

y wher e soil s contaminate dwit h u p t o 1 0 part s pe r millio n (ppm ) o f

polychloronate dbiphenyl s (PCBs ) an d24 8 pp m lea dwere lef t o n site
. Durin g ameetin g Augus t

14,200 2 hel donsite between representative s o f CMP , W&C , an d MEDEP , i t

wa s unanimousl y agree dtha t th e draf t O& M wil l b e revise dt o includ e provision s fo r periodi c monitorin g an d maintenanc e o f th e D A cover . Specifically , samplin g o f th e D A cove

r wil l b e performe d t o coincid e wit h eac h 5 Year Revie w proces s beginnin g i n 2007
. A tota l o f 1 0 samplin g point s wil l b e chose n randoml y fo r

eac h samplin g event . Discrete soi l sample s wil l b e collecte dfro m4 " t o 8 " belo w th e surfac e o f

th e D A an danalyze dfo r

PCBs
. MEDE P wil l b e give n a t leas t 2 week s notic e prio r

t o eac h samplin g event . AUGUST A 1 7 STAT E HOUS E STATIO N BANGO R PORTLAN D PRESQU E ISL E AUGUSTA , MAIN E 043S3-001 7 10 6 HOGA N ROA D 11 2 (.'ANC O ROA D 123 5 CENTRA L DRIVE , SKYWA Y PAR K (207 ) 287-768 8 BANGOR , MAIN E 0440 1 PORTLAND , MAIN E 0410 ? PRESQUl i ISLE , MAIN E 04769-209 4 RA Y H I D(;. , HOSPITA L ST
. (207 ) 941-457 0 FAX : (207 ) 941-458 4 (207 ) 822-610 0 EAX : (207 ) 822-650 ! (207 ) 764-047 7 FAX : (2O7 ) 764-150 7

e p prime d o n recycle d pape r2 Establish Criteria for Termination of

the Vacuum Enhanced

Recovery System (VER) Base d o n th e sit

e conceptual mode l residua l oi l remain s onsit e trappe d i n th e cla

y layer s betwee n th e overburde n an d bedroc k Additio n oi

l ma y b e presen t

trappe d i n th e bedroc k

fracture s Th e amoun t o f thi s residua l oi l i s unknown , however , i t i s understoo d tha t

an y reductio n i n th e overal l quantit y o f oi l remainin g o n sit e wil l hav e abeneficia l effec t o n groundwate r

qualit y Th e VE Rsyste mwa s firs t use d i n 199 6 Sinc e the n approximatel y 8 5 gallon s o f PCB

contammate d oi l ha s bee n recovere d throug h th e us e o f thi s syste mHowever , criteri afo r continue d us e o r terminatio n o f

thi s syste mha s neve r

bee n adequatel y define d MEDEP , followin g discussion s wit h EPA , require s tha t a s lon g a s asignifican t

amoun t o f oi l ca n b e recovere d usin g th e VE Rsystem , the n operatio n o f th e VE Rwil l continu e A significan t amoun t o f oi l i s define d a s a n increas e mth e amoun t o f oi l recovere d relativ e t o th e amoun t recovere d throug h passiv e method s usin g absorben t material s Thi s mean s tha t i f th e VE Rsyste mi s effectivel y increasin g th e amoun t

o f oi l bein g passivel y recovere d fro maparticula r well , i t wil l continu e t o b e applie d t o tha t wel l Us e o f

th e VE Rwil l continu e t o b e use d annuall y unti l a t leas t th e nex t Fiv e Yea r

Revie w proces s ( i e 2007 ) A n evaluatio n wil l b e mad e at tha t tim e t o determin e i f

furthe r us e o f th e VE Ri s stil l warrante d 3
. Continued

Adherence to th e Existing Long Term Monitoring Program Th e O& M als o include s alon g ter mmonitorin g pla n requirin g bi-annua l groundwate r samplin g o n selecte d well s Sample s fro mthes e well s wil l b e analyze d fo r PCB s an d volatil e organi c compound s Thi s informatio n wil l b e use d t o evaluat e whethe r th e remed y i s successfu l Suc h lon g ter mmonitorin g wil l continu e a s lon g a s th e groundwate r fail s t o attai n al l applicabl e standard s 4
. Consideration o f Contingencies in Case th e Selected Remedy is No t

Successful I n th e even t

th e provision s o f

th e selecte d remed y ar e no t successful , remedia l contingenc y plan s mus t b e considere d an d implemente d a s appropriate
Th e MEDE P ha s enjoye d th e cooperatio n o f th e USEP A i n addressin g th e issue s o f concer n pose d b y thi s Site , an d look s forwar d t o ultimatel y resolvin g the mthroug h thi s Recor d o f Decisio n Amendmen t

I f yo u nee d additiona l information , pleas e d o no t hesitat e t o contac t

Mark Hylan d o r

member s o f

hi s staf f Sincerely ,

Davi d Lennett Director , Burea u o f

Remediatio n an d Wast e Managemen t

c c Marth aG Kirkpatrick , Commissione r - MEDE

P Mar k Hyland , Directo r

- Divisio n o f

Remediatio n Denis e Messier , Superviso r - Superfun d an d Federa l Facilitie s Uni tF . O'CONNO RSUPERFUN D SIT E OPERABL E UNI T 2 Septembe r 200 2 RO D AMENDMEN T
APPENDI X D - REFERENCE S CITE D
U S Environmenta l Protectio n Agency , "Recor d o f Decisio n Summar y O'Conno r Compan y Superfun dSite" , Septembe r 27 , 1989
.

, "Consen t

Decree , Unite d State s o f America , Plaintif

f v . Centra l Main e Power , Defendant" , Septembers , 199 1

, "Explanatio n o f

Significan t

Difference s fo r

th e F
. O'Conno r

Compan y Superfun dSite" , Jul y 11 , 1994
.

, "Remedia l Design/Remedia l Actio n Revise d Statemen t o f Work , O'Conno r

Compan y Superfun dSite , Augusta , Maine" , Octobe r 199 4 (SO W i s appendi x A t o CD )

, "Invocatio n o f

Contingenc y Remed y fo r th e F
. O'Conno r

Compan y Superfun dSite" , Octobe r 10 , 1995
. Woodar d & Curran , Inc. , "Managemen t o f Migratio n Comprehensiv e Evaluation , O'Conno r Superfun dSite" , Augus t

199 7

, "Fina l Sourc e Contro l Remedia l Actio n Report " Septembe r 1 , 1998
.

, Oi l Stud y i n th e Uplan d Mars h Are aa t th e CM P O'Conno r

Sit e i n Augusta , Maine , Woodar d & Curran , Januar y 199 9

, "199 9 Rigg s Broo k

Sedimen t an d Biot aMonitorin g Report , O'Conno r Compan y Superfun dSite" , Februar y 200 0

, "200 0 Rigg s Broo k

Sedimen t an d Biot aMonitorin g Report , O'Conno r Compan y Superfun dSite" , July , 200 1

, "Managemen t

o f Migratio n Samplin g an d Analysi s Quarterl y Report , O'Conno r Compan y Superfun d Site" , October 26 , 200 1

, "200 1 Rigg s Broo k

Sedimen t an d Biot aMonitorin g Report , O'Conno r Compan y Superfun dSite" , Decembe r 13 , 200 1

, "Technica

l Impracticabilit

y Evaluatio n fo r

OU- 2 Management

o f Migration , O'Conno r Compan y Superfun dSite" , Jun e 7 , 200 2