ML061460262
| ML061460262 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/06/2006 |
| From: | Strmec J Exelon Generation Co |
| To: | Steven Orth NRC/FSME |
| References | |
| FOIA/PA-2006-0130 | |
| Download: ML061460262 (127) | |
Text
1,§tdvenOrth - Dresden triti Stev~
Oth-resen titim reortPaae 1I From:
To:
Date:
Subject:
<joe.strmec@exeloncorp.com>
<sko@nrc.gov>
Fri, Jan 6, 2006 1:01 PM Dresden tritium report Action Required:
Recommendation:
- Steve, This is the report from Retec. Please call with questions
<<Dresden 110905 FINAL FINAL DRAFT REPORT SUBMITTED TO Jessi.pdf>>
Joe Strmec Dresden Chemistry Manager Phone 815.416.3200 Pager 815.767.3702
This e-mail and any of its attachments may contain Exelon Corporation proprietary information, which Is privileged, confidential, or subject to copyright belonging to the Exelon Corporation family of Companies.
This e-mail is intended solely for the use of the Individual or entity to which it is addressed. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution, copying, or action taken In relation to the contents of and attachments to this e-mail is strictly prohibited and may be unlawful. If you have received this e-mail in error, please notify the sender immediately and permanently delete the original and any copy of this e-mail and any printout. Thank You.
CC:
<bob.rybak@exeloncorp.com>, <Pedro.Salas@exeloncorp.com>
Information in this record was deleted in accordance with the Freedom of Informatoff Act, exemptions e FOIA- -100s-1 WXQW
Steven Orth -,Fwd: Dresd-en triium reort
.Pa.e.......
From:-",
To:
Date:,
Subject:
'Wayne Slawinski FwdnrJan,206 1t:53 PoM w:-,Dresdentritium'report.-
I.
- Wayne, I received this report on Friday, January 6, 2006. from Joe Strmec. I have not yet reV Indicated that the report provides the background to the position that the Tritium In thI name) well Is not from Dresden.
Steve (Q
it Joe
ýcorrected 4*
I Steven Orth - HvdrolooQv Reoorts Concernin~a Tritium in Dresden Environmental Well Paae I I t Steven Orth - Hvdroloov ReDorts ConcerninQ Tritium in Dresden Environmental Well Paoe 11 From:
Steven Orth To:
TJN@nrc.gov Date:
Sat, Feb 11, 2006 4:13 PM
Subject:
Hydrology Reports Concerning Tritium in Dresden Environmental Well
- Tom, I have enclosed two hydrology reports that are focused on a contaminated well found near the Dresden NPP. EXELON has stated to us that Dresden is not the cause of the elevated tritium levels. Instead, the licensee indicated that the routine radioactive liquid releases from Braidwood into the Kakakee river are communicating with the groundwater aquifer that this well feeds from. Consequently, the tritium levels in the well are most likely attributable from routine releases from Braidwood, which is in accordance with its license.
We would appreciate your assistance as part of the TAR that we are developing to assess the adequacy of the licensee's studies (prepared by contractors). One of the studies analyzes the effects of Dresden; the other evaluates the effects of Braidwood.
We will be forwarding the Braidwood studies of offsite contamination as soon as it is obtained.
Thank you, Steven Orth
-CC:
WJS2@nrc.govjgc3@nrc.gov
F iltl DnOl Report Hydrogeology and Groundwater Investigation at the Dresden Nuclear Power Station near Morris, Illinois Prepared by.
John ;M. Shfer Stundance E~iwirornn'ental ald Etrgy Sp~pialists, Ltd, Santa Fe.-ONew Mx*i June 30, 2005 Avit'ikg'd and Ceonfhde-nlia1 Preparad at t1e Dire-clion qfCQWEseI
TABLE: OF CONTENTS Page LIST OF FIGURES................................
ii
1.0 INTRODUCTION
...-....i.............
I
2.0 BACKGROUND
2 3.() SITE CHARACTERISTICS AND SETTIN,..........
4.0 GEOLOGIC SETTINO.......
.,.........................,6 5.0 GEOLGJC MODELOF DNPS AND SU DING AREAm
.......... 8 6.0 1-IYDROGEOLOGY OF THlE D NPS ANDSURRO!8 NDN AREA...............
3 7.0 TRiTU.M CONCENtRATIO-NS.i+SHALLOW, GRODAWATER AT DNPIS...
- 23 8.0 ANA-LYSISOf TRITIU M IN TI-ORSEtN WIELL.................3 9.0 CONCLUSSIONS....0
10.0 REFERENCES
32 APPENDIX A: lORIN LOS......A I..
A APPENDIX B: EVS4PRO') INPUTT DATA...................
B1.
-APENDIX*,C:IE WING THrE DNPS 3DE*EOLOGIC MODEL....................
Cl Privileged tint thmfideitial Preparned at tihe I)ireclion of Gounisel ii
LIST"OFFI*GURES Page¢ Figure
.My DNPSinrhsterl pan.f county Figuit i2.o idntitil arta AjW'aputh Thhe DPSand thc Fiu~3 ime scoi"s Of trili urn CM ncetwf r0 t h;i th tet
. 4i Fi~u&4.Mosi :of 1:24'01 USGS zopogiah maop oeraonI0mtr res lu.op DE.
r
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. M 1"7 Fitw t.Mp hqig pi~~ (15Igalw vqfndW tW sr(bTifrows show the dirm&d&algufdwaterw),.,......
- t Fig~u~ro !4.*
.Otober- '28, 2004wa4ter Atilt*ctvi6,,n (Co-*t6itit il= 1 ft.AMSL).......
- Privit:gei.
and Coqdu tIti Plyeptiredl 4 Direction of (2oirsl
Figure 1i5. Averagd (August 1994 - Apri 2005) water table jtkxvarkm (Cntour interal1
' ZLAMSL)
.,2.
tkle,..t...
40 Figure 16. Avcrmged (August I V
94-April 205 04110h
$lw grqO4w*dter flow vectors wthe..
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Figur§4 I,,t 1I.t-itM-g idskwiI1 ti*m4#pt E vJIwftiuut *fnnk.ou nodal
.,-,Z6 Figre2.
P-x~~ip u sratetrneicafrs'qsx4 wml tpi~u Tveo~nrikn~n 1!ld
£en-ur*te 1mtnt~....~,3 J'Hilgd and LConftdendui Prepswedl"O w Ie Ditecdnofl cenrC~nsel
. IV
Lo0 INITU I)JCTION
~up~i~
iwfonrnnta
~ilfnrsgy SPena LAs L-.4. (So O~a~i~
~ cntpced byr E5xidai Genera.1tion Comlpany (Thx~eon) tQ-Investigate the iydrogeoklgy ad grounpdwae ss.isa.idi th-ji~ ~the Divsdon Nii,;1enr N Volloptiows.
(N 1cd it
=-'Q~sev ~ud-yCM-n 11inoiý Mg 1). The Pirimniar %~u hfti tiyw~teketfctinadcait~
Ern~~
groffndvoter pttihwtys ota and.O ~ffsftc;o-e.irneresi wmr tile, mocsik~ u"VbW4e poth'wy for thcq!
n~~.ationartritiuion argntn 0iho-st.n ofic Thc Qic~ng~~ud
~c~sios f t7sin04--opar
- ~s~
dii wlaedt Ii pp-rin hiri umprovidc by k~v its eonmvawrs as'wimlasfta n
iuto btizdhm st~b-II.i dy.,W.
41 l~gut~1.Mop, ohowing Gnrndy 'Coquty, IL an DNPS.i'ami,4hestenm-part -pr J'difrg avd, CwIodn0~
Preard atth Dret
-'icizmll f
2.0 BACKUROU Nfl ThePMS wsblIinteI9sspieo hfirtumnria 1-QWlV =Cupids consruted Vflidn U op'.
Th tjiti Is located ini GrundyC~wtity Illino~is in T34N, RBE-d'adccuisprso etdn 25~~~~~~~~~~~L 64, rl36ThDPSIpadtheunits: ("two additi a-a unisPerefnstructocb4R4 brouqght pp ein in17 n
fuilUntIwsttired fram, 'service,i n -1979.- Units 1 n 3:
c~dnAtinue to-9-efletttc" LIctt H tjf.
3 lnmcdaiiotbo teDNPSI Ie unteiadevlp' rt rchesidents bobW a
ff th irva the doetc el itv2)
One w
- MIA, t1Ss l,
latdat ts~~c peiid~h11 s~h~d OriiimsneJntu19.Tirn1cvlt
~~1ý senie tWcCentH~
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i.egji.c dPS1c 4rrJ&1j%
w flow tt ýthq pI? baeKg cq4o-.ThMstrenl ctfdik~bdsttt$ udrmkefby Ht~i ii~iaer~ni~omany~arn~ en&d in W-$#f h 1$st A
or-fltprnglW0Zq,.
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.4~rtei Siaz 0~4cilsoia~tdioqovf;~pnhgaddtiil a~tiaives olheattsr p
ti4$tis D~wy'rc anlscdedbHiea'. 1995) to~~~~~~
49I~ badKTRIfC NT
$T The~~~~~~~~~~o D$$iawad*promeyw t~M~i, I orn wtitidteoWos zfi cfdpdtj Thf.bi Oifd Jic 4Th q.e Mncti IL",.
Pif is Ja4l JwM itlo ou.p ay biiinbatt higtrrortient.~rttts an s.tc1,Ttol oorpi e lti provided Ito ofw ID tc e~,brin4ww.lan sut-fcevthigionik
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tm or~ntaw
(
~ppdi
'a 16% AOc~ti Of tI nt fNP',i !e--e Iaiid CoidteINUM tiw D e q)-
wi-mnei1 3
fix;fig Fig~r~ ) tp,~is trt~u~ ~~qt~iA Di J
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riiikged add Con/4)WmtiaI
.Pireowat.?
ore i&w£ýrMei qfConlwte
Figure,4. Mosaic of 1:24000 USGS-topograplic maps overlainon 10-mneter resolution.
I'rivileg&cl and (Injid1entia1 Pilepaivrd atit thwe Drtion of Caniixe4 5
4.0 GEOLOGIC SETTING As prcviously described, the DNPS is located along the upper reach of the Illinois Waterway.
1l7lhnam (1973) conducted a detailed survey of the geology along the Illinois Waterway including the area in and around the DNPS. This report adopts the nomenclature of [lflhnan (1973) in Characterizing the geology of the DNPS study area. The DNPS is located within the Morris District of Willman:(1973). The geologic units, beginning at land surface, within the study area that are important to this investigation are the Ltiedrnsolidated surficial deposits, Pennsylvanian age rocks, and the Maquokeqta Group "and Galena Grt'.tup of Ordovician age. The surficial unconsolidated deposits are a thin layer of till and/or alluvial material of Quaternary age that sit unconformably on bedrock deposits ofrPcnnsylvania age (Wllninan, 1973). Within the DNPS study area, these deposits are typically 0 to 35 feet thick.
Immediately below the surficial materials in the Morris District lie rocks of Pennsylvania age.
According to WVillman (1973), the Pennsylvanian age rocks differ from the older (and deeper) orgrnations, which are dominantly of one ro6k type, in consisting:otfa sequence of several kinds of rocks in thinner-units. In the Morris District (which includes the DNPS), the lower Pennsylvanian strata consist. 9 fthe Spoon Formationfwhich is doninanttlyshale, cl'ay, and sandst6nc but contaifis thin coal and limestone beds.
Situated unconf6rmably below the Penny'Ivanian agerocks is the Maquoketa Group of Ordovician age. The Maquoketa Group consists ofthree fonnations (Wilhln, 1973). The uppermost formation is the greeniish -gray shale named -the Brainard Shatle. It is as much as 50 -feet thick and is poorly exposed along the Des Plhines River south ofChannahon and on the west side of the Kankakee River.
In soime places, as sat Divine south of the Dresden Island Dam, thd Brainard Shale is completely truncated by Pennsylvanian sandstone. Bclowp the Brainard Shale of the Maquoketa Group lies a middle limestone named the Fort Atkinmon Liie*stone. It is ontommonly 20 to 3.0 feet thick, Tbc Fort Atkinson Limestone underlies a largqarea south ofthe Dresden Island Dam (Wilhman, 1973). Within the M6rris District, below the. Fort Atkinson Limrnestone, is the Scales Shale which is gray to brown in color and roughly 75 feet thick. It is not exposed within the study area but is present throughout the extent of the study area.
The deepest geologic unit ofinterest in this study is the Galena Group, also ofOrdovician age. The Galena Group is comprised of the Galena Dolomite which is upwards ofr250 feet thick in the study area.
Fig. 5 shows a typical stratigraphic column ofthe sequence of geologic materials from land surhece downward into the Galena Dolomite. All units shown in Fig. 5 are not present at all locations throughout the study area.
Privile'ged and Con.fidential Prepared at the Direction of Counsel 6
Geneta* $"rtigrtiphic Seqjuence of W~tenalst at the ONPS amd Surrounding Area 4epth : J 0
o Lith0oi*a 40 to 80 1.2.0 Posibj~oo domtion of Pe'nns'ylv,0idtjn System of
.. llman, 1973
-"Possbl~ySorn Porti~matiOr o~f Pennsylvan~ian System of-Possibly SpOon. Formation of Penns~ylVaNnian Systqn or W.Irman. 1973
[,, po* sibly Spoon FO.rmation of Penrmyva nian System mofi SW Ornihn 1673 posmsoJ0 viark plgenn"yly......
.of possibly Ft tisnLietn fthe Maquoki4ta Gvrou
..liman, 1973 Posistine Shale he Maqui iote Gr oup ofA Wlo.1973.
Gailena Dolomite, 1l80Q 22-
- -260
-28.0 Z00 Figure 5. Typical stratig*raphic column of geologic unitsmwithin tdic area orinvestigation from land surface to the Galena Dolomnite (Note thati all units aie bot-present cvcr'yw¢hce thtoUghout the study area).
Ptivileged alld Collfidlial Prepare~d at the Diretion qf Counsel 7
5.0 GEOLOGIC MODEL OF DNPS AND SURROUNDING AREA Overview To better understand a*d c ret the geoogic fnv ronmet ofthe DNPSand surrounding area with re~pcct to groundw'ter behabvior, a fully three-dimensional, solid geologic model or the area was con!s truc-tedtla~t ftudes al i
ft he
( I.
ogi he a e csrt ttc s
ll e units described in theprevious section of this reprt The model is basedon the analiys's fnd integraion.ofboringlogs om acrioss: the study area. A large number of drillers' boring logs are available from a gencies.suclh!
th1e ilinQi1s State.ieo:ogicl Survcy and the lllinj,5 Stawe Water Sury in addition to thosc proylded by Exelon resulting from on-site in,V.-estig.at.ions. HoWdver, in terms obftheirgcologie descripdos p
hr scosrbc aito in.th quality ohe.f io0s*. For csample,.there, is no consistent teminology-or oiiieneialurebetween logs.
Furthettlr mapany" ofdidt
- lgs.&re Adifidult to refurenee geogrphic!ly gilen th1 generic location informiaton. Each ofmore than 100 borigblogswe re screened for total depth (gen'rally only borings that penetrated the aeDhoii lm616nite we`r firther coide-red),detai iCdwb their geolo&gi description, reasonable confidence in geograpc location, and spatial coverage within the area of investigaLion.
O.fparticular conccrnas the abilitmy tob reaso-nably accu*ratly id'ntfy rthe geograpbhi* loation oteach borng.U.S Gc~ogcalS"'ve 1-24,00( digital topo graphIlk maps, U.S. G-W-logical. Survey digi'tal orthophotos, Grundy COunty plata ook* Exejon site and vicinit, maps, llinois State Geologital Survey personn we~re all ued to confirm t he locationfthe g lbgs usd to ercate thie geol*gic nodcl of ihie studyarea. This process. resulted in the*election. of-over 30. los for the construction the geologicnodel w-i~th..aln estimad Iocation raycuiayof--30 ft. (!10
-*n)The locat.ons of all 33 borgs qualified onoi"clusion in the geoloic6mode I rc,, own.in Fig. ia. Fig. !b shows the 3D perspective o the logincl~de~d n die m~o..del (AppendLxA). The georh'i coordinats of each o0g were transformed".
into the UTM.(meter)..
N "NAD27, ne 16 v*:
oordin-system for mapping and display which is Cn~sitent with-the maps and 9rthpht phyiused in this study. Land surfac 6l1vation (ft AMSL) %khe not in~cluded in-the log, was interrt d
irmh
.. GolgclSre l:Z4004444 d
Icyt elvon rnodal moai ote tudy arFg., 4).
Once :the logsto.be included in the, geologicnmodel odthlNPSand..~urrounding area wereselected, they were re-intel;rpted to conf om tw ith the stiatigraphic nomnelaturecif W; Ht nain (19-3) described
ýabo"Oe InI some instal ese the copulation betwea 'the ini descpion in the lo, nd Will
's nomenclature was not straight trard. In-these tass,all iAtttf10t &re Made to"foree consistency"
.ithithestrahltraphie.psitionng (*"
th1
, tfortk:Atson" Lmetone is evcrbelow the Scales"
!Shal and-.!;i reta.tionin ncarby rigs The.stratigrahi l.og for ea0h oftheborigswas entered into Stater,-a solware package f:r log0 naaysis. and dispay. EIah re:alilyzed log is presented in Appendix A.
Pur-ileged and Co*qfidentta Preparel at the Dirdction of Couisel 8
North
ýMlv Figure 6a. Locafions of, glogic brnswhere driIlets lo~g9:'areud roW1 con.struct the D NP S:3
[Z#~p~k ~
4
~'
'45 I-
~
SMIo.uIW wZOO
~oI
~
Figure 6b.: Persp.ctve view of drillers.' logs (Appendix A) used to construct the DNPS 3D solid gelkitgc, model.
Privileged and Coq/idential Prepawed at the Dhecltonq of('otmmsei 9
iata Preparation for EVS-Pro*.,
CTeeh Corporation's EVS-Proa) (www.Ctech.comlqpubicatipns.brochurcs/evsrO,!m) spatial data analysis and visualization sofIware tools were used to construct the 3D solid geologic, model ofrth'e DNPS.and sarroundingarea. EV-ro integra tes genstatistica! anIayses, specifically variography and 3!D kriin, with 3D vializton capabilitieS. EVS8Pro: requires borehole data representing stratigrajph'chydrostratigraphit features to be inputvia a parlieularG EO fice format. The GEO file cotnstru'ted from the boring data (Appe~ndix A) to show the 3Dý stratigraphy of the study area is presented inAppendix B.
DNPS and Surrounding Area Solid GeologiR Model The DNPS and surrounding ara..
3D solidg, o6gic model was eonstructed using EVS.Pro, as noted iabve. EVs-Pr-ii) is a "toolbox" of data input prOe.Cossing, andy isuafization functions that ared individually el~ected and iiniked? to::aehievetth oljcetivs ofW elachparticular spatial daia analysis and visualizatioin applicatioln`. The..individalt funICions arc 140ed ia a network tiat describes theoverall EVS-Pm projct. Fig 7
,hows thQ EV*S-ro* project for th DNPS geologic model Krig, 3D, Geolog.y inputs the DPNPS GEO.data file and performs.the vmography and kriging.operations. A spherical sernivariograr*,With. zero ngget is used for ord'ar kriging. The spatial resolution bof th DN-S geologic m i 30 30 Y
.he vertical
.xag.geration is 3X*The remaIn.gto.ls,"
ih theh DNPS EVS-ProV network (Fig, 71)construct the vis!alaion otthc modelWithi EVS-Proboi **h todcl can!be vJiewd fromanyperspective id orietation including slices and dices through the modeL Furthc+r an iniatiOnsan be* reated thai!tw a sequgnce of
- moel perspective to be vewed.
AppendixC lists full instruims fer Viewing thI DNPS 3D-solid g gic model. The following figures show several views ftbhe-r ltfr vrious pr§6pe6tive*. Fig.
is an bliq ueview ofthe model loking northeast. Fig. 9 shows a cult cut oI'the model along a norh-soutb tract. Fig. 10 shows the equivalent oftwq-&
thindgeologicnfenceediagras ;supeimpoAd.TlieDNPS solid geologic model can.be viewed from any.perspe tiv* andt slice within the EV*-Pro.
-sopftare. aplication. The anima.tion ofth iDe PS Teologiqc dcl tha'tacco.paniesk this eport is deigned to" bused todview
.the DNPS geologic frm a.wide rfaige of fixed pr ctives outside of the E:.-Pro, software application'.
Privilegfed and ColflidemiaI PrieparLedI at the DVIfCtion of Counsel 10
figure c.-
EVV-Pfroi petwork, for DNPS, 3D solid gooi ndl Privileg d ad Co4 fidential Prepared at the Directidon ?fCo1ilsel t
I~o~ti46 I *uel#
o: A w-&~PMtXt P141? SI) galW ocThor a~~zt~ z db Ai.41 ts-er o h~~bDPS3 elgcmtl r iewt
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-moi-rn els hon Fig; IlIwais CQJICQ(Od~~~~fl Aprikl 4t 2205 (dt*nAteeaurctipP-3?tPV-Sa S-W)
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igs 12 INArl4 20 ae ral ma.SoswCJTIthtteIakkeRvr (orial pool-elevitio equas55fAM1 h as an the 1/4 Wgtlr tabl&TO the cast 6of the uN$
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, d ~~,t~# ittfliil ta ha%44 Iv 0rsre -ofitatcr 01eQ Mi,
Th shfpIzq ruvr~o n'1r, W44WiwhstbW.i41 rpiA0$
Thern~y~ &e vjwmd hftarcl gQ4t-bRv.* iii htIA1titn
- viiathe, 1~~~Nt ~
,10$;t@a -t Otrudnro~* ~I W6W. hatllotvaeýM0f~~tC 0t914 th *s1byiwhyau1~ea i hpCtIfn4in t (e as3 fmfl1Iitu ova",i tl'Mi bth
'1
)TAI Ea11. Wly th
-~Wt jbd~ifterm aseNvayenoAlt cn berpriatd fwh tlo pahveagm'~ ~.
1.~P~
thw hb hr
- jge~O "Ia 4iirgsiWdtrptwisfdnftmi tta,~eDPsitwr e h eeta area tiong heKgdki~ce Ricr.MysIiilw gqumdato fiow t 4h~ %oth file waer abl
- mouid, Isdive~d Wtpr eAst c'lt~iht~rsdeta ra ot bi Aptiegl anil -6an0iilei.iqW Preared atiePtetmoCcslj:
Dee aedoi ADo*Cai*
oi~kaufr of nprflrisr VMhinl~m s~t~fy
~ b~tNS area4 Of
"'L ii:
,b w
.1.4.
rnwtigip~The. Wp of h 4@C bedoc aquitt ati -is the Galena&lmtrstbJwth M~qotdti ha~
tilbilgvnt; oreprdusiveunpufThedep bcparqk
'Ir~evr the St. Peter
..ppto. lW......
lY AM$*1+
.. th.
... $SO V t,
- ~
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.It (ilu+*,4_D,Z) tr.tih 4t4 ze4.+*,+
g++atisd ir b e pU.I..
M$1
+.
r
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+.,fth. +de+,p Wq+nx*
+
fl+&gbdtit t~i~ 2O~~b
~~*at~hnsa~~dakft1 t+.,Srttin+ n
,i"j vwtw ithdawm+
- .+......
A of.;+++ m oat$yhl9~
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r dutigi
, *...th di s t n
t W
t b mara....gflte$*
(e.z.
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-bd
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r to i
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t
.00 mo
.I.t Oka r
i W
e LOy 0-.0 a*
+. "
+
q r N O....g 71 isni AMA p.pnt Akufte2U4 pQ~
stta tetl
.tt.lfl, lwt bU
.Iw o+ c (- SC, ( i t). w pI+ l +,ig.++k....S
- MPZ.a g T-e.+..... 0 Wftt.,
.-A yLin I zf' NS t4~
e S4I M~nSI At$
Avuhesna ft AMZ,..
Sb fl s-o...e+ rc....
kr...o *rjn t'hgiugh tlp.
u*"
" fo.
,h+t$1 C D ES.-it iii ll$likellhd.id.
+tlr~m
- .v o.r ~ pi &i, e xt..u..l..sl.
- t.
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h.n,..
d s g. t.h.
h a l..
th Mquoicctn.shl
~tifl6 ~n b+e&riin~. fli'aI Thbtb1it tl~itfoutl~i.jh trh+ shale i-s+tzttlIYiJOW and:
may h..ave cxtep.¢4$!..1nt...he srib # een fhi i
s m P t
hbit. tbetdfT i smil ne-eohtintfbuK turated dt+hikg~d gid
-1% wt i
At.
Prepared~A arri Di0c~
qfauns015
3930az0 IMA2 M 40$010 3
- pC P Wqo0 Z=00 UWM-00.9439440.0 Fi 1, U Map Xhbwin k1tO.fibio iuibwtrlVel-WOWtring wclls.
Privi~~gedaitdD Ctfn(ideoru D6
ElgureC it. April 4, 2065 water -tteb~e elvat t~ontpur* inerval-IA f AM4L)
Orpari l11 l--h-ccihn oCozrizs'17
4s;C2 6I 4V, VVVQ 45a18c~oA
,JT 9 4
...34O
.4
.S O
, 741z",
Zi, M Figue
- 1. Mp shwin Apil 4200- sall~ ~fund~it~ flwv~tors(ble a6ws hci sh diccin t'b~l'vgoudwtr yj)
Prepared at the Die,-iEmf vze 8
458~49~
~, ~
r.
44~
Figure 14. Octofw2-IM1Ot14 water tabe'..gjyafoD 'Coot~vr idNiev 14 I fiAUSLI.
Privileged q~z4 Canftde!?iial Prepared ~zf (J~ Di~ed~tio'I of COunSel
Pjg r 1 o vi~f (A
tus 1994. rAprii 2066
.44k,~bt 0o~at~ 'OoarLia pnrv. 1. =,I: f, Pr
.eptwe at let.retinqfCune
~howthe4irctir(
fs~ij@W *boundw~fta flow).
Prpaiz /!
ýr Dfreeli,01 Of. dowzeI 21:
ptway: fOvmthe DNPS to the deep bedrock. uqui.r benc~sit Qoneqgn. y it is
.k rcaaqnabie IA assqn-e that thbcre ino signiificant &tbundtr pathiaylbr the wnigmiton bnritum fom tie DNPS
,to thcrep bedrock uquifcr. te¢re. ire b.th ~reional an4 on-siwt e dta thtlkat
-the potntioftric Withn Acb yihity WK ti I
A r; seven 'rqfitel sl4lw(ie. ttdph
< 100Il ep b*riekw*'AL*tbr
.whlich 19.95 w~atdt l*+vtl~tb*.pdblished -hButch (.20,02).): Thi Ihlwin tagbl is:*ts thes w~Is, itog with thtr dVp Smi n uraet S.twte ep inea.
I" L
O:
ft #,.,-'...
WLte~o 1995 17ftt toftft4 W4-LeI Wf Iwph surWAe :M -tamn 60U
'*"* i 04*
Wyihi-AIO
,I f.hgtoa-II*,i cto 1_e__'__
y_ T v*,,
A..:
Ap W~fthhh' vmsftjarti-onf ritaY,"Dsi awveftd I Wttbirhg stewiobk b us~a
-f1 debve M~tn 6fhMttjIhtfitid*46~~~t HzwŽ$ t-J.Q" TT t'w"l tb&&",.
atie tt.
°"J ".t.
"I p
"i~ th" PS Th" wel tt k-,..
+ " ".
A;,E "inx
'+ iA+ t4"t w t ra-:.,."
to "rerrc a~ibtct IsC&m~s th Db4PS.
u o P.r~
W inmidnptoiE~tpr
$ep osw~ w9 itk
+s +4 " "4?i
+l i 'i inih." e ell,.. T h n
.. ix?.#k22
,6:m...t+j..s +b., vat.irnt.a-.a.:
.o+ns:.,wan.. With t:,- e.-s::i+...,..
f++.
W:trng p.i.z+.
.mnI4.
is thnvtW
,,+
potedop ict *te o th m
le+t, Dolo'm++fl.itb "i
heD P o1 sur m* i
... ha -ef lp.e.....
bet~
utbottntt Aaqrukta sa.e Pflvkseern C qqJ++#+*
- +*
+dein.tal2:
++ ++++¢+*
Prep qr,+s*a.:*oJ.reclie ofmi.m Cou.nsel 22.#+
- ..p++:mm++J*+at+
7.0 TRITIUM CONCENTRATIONS IN SHALLOW' ROUNDWATER ATDNPS Tep eur Tioio'ftun(ML a
6We inrytCtesrcesue t mon ti OiaUw qoVx4wuýer kw gtntii. TN'.n
~ig~
al 04ad~g$ nsr 200 s m tleawr shallow m 1g~ wl~ o Pitin
.0W49ftfPI-a 17 shws thgft'eniqst4Mnfll204*nFg.i shos t~tlt~fro st~niZ)S.As bonihia. i) ~ I thre
-i
-e s
Cout Qte tt'S bewsn j r4be~i enta ar.p $pit4.4AcORve, ti i rirnCietttb r
i~~~it :S flhewTOM 06f-14me~u iv~;zP1'3/49I pA $
tt onko m-oreasqufhq inta} f1144Wtef~ 04' 1a&.T ttiiu emientntiwt Mi t
b e i t no mmt u I$ktiI, st~s Th:
tw.P*
i dqg A.nCI tb 4isw vso hei
'Ing seipP d ilpct rn~I1 s ~bdA1 mh nidlyst udt6 0*4m ato misi lw aquWv ;ho J$S~1P J~
r~t* a4ip~ ~t41 00P th
,9kiia+b il 4 t~Xvtitt abe Ont~tf~tT h ttfltttl m
&OtJIWdtVito spcitn ct sug~twt thfb I no&(giffiafi nitb~tothcbmone am I110 rrinawtt howr h vic~~~~~ity~W Ahn f~
II 4#k'tbs w.T~Cld.Im W
by~~~~~r ~
~
~
~
~
i h,4
. )ff iPait~tid lsl~
&i hte w Vsalh
~~~~~It~~~~~~~~~~~~i~~.
Kan,~ risn0V~itft1l w t 1nttIpg vimC&~
w~~L~~h@~iit~~~nsta~ait dflkrabm.h
..p~
waes-i s~c w
.,~
hemtha evtpa~n'tft te. D~rW~d~nnt tnIndng L
A~~~~~~~~~~~~~~~~T1 fl1t 75-d1i.1)wa sa[i~d~t~ ~na~oMflp 4f~in w3d w.on~~
wto~4(4 $4(
~AMt n ites b irohlpe ei~tl~I*
1fA'eikr(O~t b&.$tpt~o~4$4hwh~cno.ncI mni4,1 Ag
- q.
nlk ~r`vM,0`Tate Sowin rn-es MR.fhIv~ah~h
>~
lt4i~,Q ~d~~i imtdt firn t*e~1 tktik q
nttl d~4~uh pn~g~fb IiWe n Ijb tt'tt
'r~lse
~sn bouWal"tuetyotnktwtiaretMm~ae 1bwipatiophrwrs hr Prpae a 1i D/tl rz vCaac 123io- -o
S4582
-4581Q5O.4
~940~
0~
5 9 t 4F~
- 94200, S94 400 40 Figure I 7.'TrikT i0ettf1if n OIe sb14WI~WIROOOc 9a40 aqifet the. DNIPS
.n fa
.604 a ~tidC-o i 1000 24lL Prepared (a the-Dim.tHint of Ciunsed
M9UOO 493600' 19ý800ý
'Z9QWO
-iPG20O S94:4PQ Pigutt IS. Thrittu c
ti~fl't~s in ihaliAo ftifnohoifffl-'
n sjir' n 2DUS5 (Cbintni gtbursiiaaith 6fDNPS-is ra~itf of DPS-19.f EI'e1Ii~t n
qt in~ud iii
-Pilý patiddi he Dheitio6fI Cd'Ihsel-t~Q 25
4howflc ewin~igu
-or mm a
as~l 7gs ale) a--t Fiqc At IoVsnal$
whmiviThum bincnsvi rtu stihiiamdt
- ft
- -gx d 1016'v-ibnAb O Tho'p~gie n~tedas bonirkin~hj~ h~dto p ith~aU n ili iasdsr inmslkad
'oth atrWisThtfhl&.At frit t';e41r p ibr uh ail (igm Z$, itappear ihatthewellis asa4 ppmpot.2 j iiiwart
-gtk PER.
ctpnhl tqeanlr iws ofgb h~lcslgiiitaata hd ~sr~~
ieN ktit&
~n~r et~~~~~~~~~~~~-1 SO!-~wWt ite.T~ w &Apl~l44itAo pnbe ~i4~l
-Wnsd
~tbojjld 4e Jy4MWIo ba$mult hJ.1Wel setw -A th4~~~~~~3S-P 1(
Abv Mh ge o'f g-110~
Iastfe d ithsnsn~n b i
lAtO~g~pOhite
- bad, Am"e
- '4v CW4)
- A, S,
th
-e.M
~i~ly 11 Mmeston~~~~~~~~~~
betOY ZMadl~d2044fwr~4q lj~ 4k alu t$6 vtIs W.~
V oMfid&'ssw t$)
dy a$~t~actiiithwo~d Ma szudl4l3 m-w Tios fl pre a"prrriateO v 4 f
i' nsoneadzes l-e4 4.h;tS)
P4 e~sti Stsqt~ ~epedM4ZEt~W-~OO{Rawmaw.,.,
ZtPIl w h
~~rz~vat~~~tt0 rnogiies fvt*~tS 402) ws th~t flsftnf~ditkwa~thptfbxnjgtauat fikbt-tikfb o1vfte s~twrp~i~a~iiv i~)ny.n~q 4ro~bXtuh MO-tW whig -i*d*
th
-iPMefg swtg~ne~z s
i itt~~r 9enrVa it xiJ T
ptest tbflypnhesi tbeojdput was asuedto be twtIim S.rporaedic themp ahica-e:bWttelvlof ir nheodCniaaalbcrmsmln
A0.
.100 246 I~ Cons1ru~b~on hii'f1egd
'C670 C
V~fdein
-Prepared at the0 Wcirnqcoulmse
'27
dat st hanthe, DSP-34A darta e-l
%0"w~,tes aast wr cnbne orvi t1~ho.
es willporal rescdlttio1 of thp timpe hisry of.0it4,0)404. Fig. 21 5bqows$thegTpho thev~
aa trtiin, ~t~foi ucdasth U'~~n ~ti~te ~r~ brth titti~' t~isprtMode. At the begininofth sinuk ionth trhiu i~ncpraion 1$ as~sumed to bc b4egrund (c.zero i th v
4 era~rntt~ttQ%~ ~E I*:~ oo ýAoavmqppnt 4104101w~
ip 4Tippmm iiy ri. mmly. tRPjq-,
v-,Rmfng, bY.*.
hy~c vek~ itdiidi~
omltiti.
110 IN't Wio
-it-d f th~if
-innl1atd tfl~tin
..Wovpurmf os. to 1h
~evwI vdun crtn.
-:40 WONs vIS, is TPAisict1 fiyrulic coi uc.t.V.,ofparu IibnO~tond0 Aq( l~r~pn6,...o oh6tiiin vakn Privil-to oud cuI/idcnii
!'regUwdP~h bi dt~
f Couisel,
concgmmfhaiqs in The-Col C anal (Fig. 21) Wcntx-redccd M-by 10%.W.
(3v the, uncettaint in these ---
valuesand th widegaps in-thia timsr',tM jitnn qrsrnoa~.
Fig, 2-2 showt-ithe results. of whsnoej rievrpring heimtedtRtiim cnetain the observd well tritu tonmfa7s fro I
h pcrdi sapigTrh2QhIe betlo"W20pCi/
n psuiat b4 bai, rk ThA revief.i b~k'W.wl tinc rw Qct-atoobetrtiI, pra4 t
oheol. A dfr hOtetaidht ft ah I~
svery
~o4 sethzl btten d*nt ob10d.u tnI~
~tfip ocenain iov ir 4IW) ElCi Utib h DPS4~SSOdtisll pda
-a4gu4.i*; beginnt'..
iina tdlwqji-t (4Rh lrgetit~f
.066.tif~~}~p~w iecdinosn frro0uhwite al~h trn z Mit Aw4 nI~tosmth41
&Mdbt eoncentratidftsD'S 0eY ek-4ae telhrd tcewiyhite,-frie
~sreef~Q ob~edsse~i piis ig 3~
hy. WAp~~gip showir 4A7 50:46iKdai i.2tit Wih hi tapVofl tha-Viyn$tltuttihtnt~tn i te tod~ma 4$
rd0nnin7'e shown~~~~~~
.n
.i~lur
.n
.b
.w
.~~
.pvw.
Fiah~jonlifr10wAdteranspe tmriA4eahr4te4-týh V v4rLfxfwa4 provtdta~is Vs.i~eofh c6ldat'pt-ftyt-f V.1w hintovofhe arty' La whembytidd h -22A--
V=)I" rg 14' i
Pr-ivieg and. te DiWhy.a#
Prejeue athzt Df&Na'qf~nasI
Ž
ta*
'Ah~~~~~ld
~ W.O*di
- l.
q W
,a I
o
fiur Ut, 4n'-0-0 $n A
'*.5,*.
t surrbutli Of li thRe-h~
toThe4e Wtli lettef$~n'u~ucm raj'etmt
Shalowg~q.qndwaer-flow at the; PN-.,V$ I pq~l~
I the wet hitgoiCl chna adio to-d bht As by the stigco'6 the KahklcbeRivmr Shdllbi' -ow grindwator B6low 10te NS sIqa1zd
- (rQupdwater in the' shalow. *aie -OWle squifr mnsi~-~~ot tlow tc h eieta oareaso-onth of ihe DIOPS. A64n I& KiiaikA~~
Rwivrý. Th39s~uk~i ~fot
,týd b fh#u 2'004/ aIru1 00 riffiurn '1-VcI 1I hlbwmiotrgW11;Ter e'44pnco --f~rt~
fin shaow groun wmwer Imrdity ootf Fb r~
prtn araotir 14DN ilP&-tpma Thafet rabi
--t-p dom.
auf hbvtiyof 4*'
14L4 RIEFI-R&E.C$`
.1 -
111
.1.1 -Y. -k-ý
-. "Az I I-.1ý1 % ',1 -11 N.
I hwl;
-W
- ýe W%,
.ý A,
1ý
- !Vý A -A
Wchrnahnn, -H-.A,
.2005-.
Per-sonal -c-irfuidaition M.WeraniDrctrCnterfo 6ro-undwtr&ei~.ftni Sutc Water Suvmy Chiampaign, ML.
Wiliiai.ii~, 17~ (3okgy a~oI' thl Illiois' WAttea A WAbi; DR fb eni60n-fi Icn plAnnihg-,
&Sbiig, NdW 'York, NY, 621. pP..
PA"riviteg e
MYn f
(VIC-ftvia13
APPENDIX A:9 BO-Ri-I'GL(
PAw'Wogcd and Caittfideiral Aw-pvpced at theDivl P
aeelpnfoul' Al
Locationland.Nani-d Got.'i Bf.teoqritng Logs PsesO to COnstwuct DQNP$ý GeWoIogicMol 4680400-
-A582600-Ilk A582000-A45918M0
'4581000-sq3~q Epst~hg, ip.
394500
~
JQ
.Pdtldpeed ond Con1dent1fia Pvpaeda thp DlroctIopl bf !CQL!Mpl
Well-1ID: S&L-13
~JTM. etsting:
39`38ý97,O M
~
E tion-5j7& A, AM L U-TM'ý5 A~tig 45M8.1
~ I I
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-17.S.
Po~~il~1y mpnF~n n PO.' ý ylv nfA.
yemo Po~shV, FtAkB~
i~~
1b aukaroup0 Wll~i*~~
Iquo PosIby Se~slu~ebt~r
~~~~G~p~~frn
. "T*.*ftlitt lm:*lhyniUA
¶60
40O 2b0 too
Well ID 869 IIMEOtg:
34462.m EIvati 6
iO5.,AM$L UTM Nrh 45k26~
.. '- -.0
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ersiwi ytmo P~smy~pblD wFhmaff toifn yeWf
/
WOW I
P~~m~Frt~P~
l~fWOLSyt i
~s~b~y
.jAy§.ooi Vim qsort.q~f the VgL~I 4$op at Oman 24Q1 2~O
~
I
WIell ID": 8.70 UTMV Eas-tih':3$93065.4 m E-0tin 05.01-tAM-SL UTM W"Oie;r~
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$cito P~aII'yajn~ 8,hpPI~e t~~aG'rcUP of.
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h&t~qur k-eta ~i6ti pi~1 p
.411MARI.
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Well I0 87 44 3T
~ig 934Q.74' E$vain:474 k.A-Mg$
- UTM NorthiWM
4.684~
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~pon Frm Wf lri~nyteit MO.
WlMYn 14#1 p,-r -X 14 POs~bfy jn mi f
sann y1rf P-4 Oat ra
- 160
-200
- -220.
- -240 I'.
.I
Wefl I.D. 876 UTM Easth1W 394167.0' m2 EIglinkO9. fA UTM Nooopir, 95-2I63 44
-A0 180
" 220 6Q I
Litheloov I'
L~~otgy Dersiw P'ds~~
S Q
ib o tf P nsygynIt-$,
m ~
Moqtjokeip 6 P~bI SaIS h of q.kt or di oWMITFRnI I
- * -A6-0.
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W~i I~
ThUTM Em~Ine!
A~~OQr
~
yIo:535t AMUL wett 7 UT4 N"tipb. 4i 264.q M~
20 21Do
.LitolqooA Descr~ponii I
Poiby2$p~i Frmafen annyI~J~n y~-alp o
.oW R NW-M,-A#tn.,
c f Pli v 7
P~i~~r~o~r F~mg~i, orsyit-nau ytmQ AWTt3Mqslt r~po~lmn E~aI~na ~boIcrnift~
- 240, 00.6 Iv~J r5.mfc.nif
.WlI 87: 9 UTM-Egtilng 33 : mEeti:
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S.ysti.
Pp~sfb~y Qe~
~m~feyIv~ni~n 8~ys1~m ~f rn~m4~73~
om 1-97-S, A89 E-- 20 4.0':
I7 Sao:
~Juu~at~ku~4
.Well a", 90?
UTM Eastino:
M994¶h Ele*Vation:
"53G.O ftAMS.L Dept, ftIjtJ~d~g J4U11*10 P~rPSSOPv I
.2 40 7-:220 280
-*o 1".80.
~~lY
~
F4Vr~Pn QIP
- ytep~
Fo vionn2T.,
lP~by
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I Pqt5ýsj.01yF~t-
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ýGalenet D(lomt6
~vt4A-1~~~~
UTM,. N6ftehutr 4662592.Om Pgpth~ftf i~t!~wk~y jthfyDsptn i
40.
lieB
- ~2o Al,~
60I P sib~y Sp dh~Frn.AU dly -I lstvna Syte c wnrriý, von Pbsi~0~60h For t-rstOýn Iy~m QI Pd~s1bIy ~
~fhe~~r90tWIm~n, Asio1an001
- 14 i*s
20
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P~i~v poo fbfifilfh f v ni Sysfmb WIJffaf'A"P 3 "220' 2.40 280 P~gI. Oft.2o~u
W0.11 101: 1337 AJTN4 ssing; 394,1i&
'o Elvto:58f A
L r~ept~ f 10~61o~ Db". riptlah I
-440 440 P~ilypon ~fh~h F
t--f Pf1insy vahnir ytmf o~a-tem m~tpe
- 240
.280 3fl0
~ft1~W+/- griN #isw&.~ ~IC~o~m~d
w~,~ ~~l
- 1338, VTM.,stir:
141.P m ES' ato:. 5D.O ft-A.SL
,Ln"TM Nrthig 48
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.260
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Final Draft Groundwater Tritium Investigation Report Dresden Generating Station Morris, Illinois Prepared by:
The RETEC Group, Inc.
.8605 W. Bryn Mawr Avenue Chicago, Illinois 60631 RETEC Project Number:. EXENW-18513-400 Prepared for:
Exelon Generation 6500 North,Dresden Road Morris, Illinois 60450 October 19, 2005
Final Draft Groundwater Tritium Investigation Report Dresden Generating Station Morris, Illinois Prepared by:
The RETEC Group, Inc.
8605 W. Bryn Mawr Avenue Chicago, Illinois 60631 RETEC Project Number: EXENW418513-400 Prepared for:
Exelon Generation 6500 North Dresden Road Morris, Illinois 60450 Prepared by:
Randal J. MacKay, Senior Hydrogeologist Reviewed by:
David Meldl, Ph.D., CGWP, Vice President October 19, 2005 Ji prjec\\tsl\\_.conNl1CeaDred*Portep sdQ en Station GroumdwaterTritium Assessment Report 101905.doc
Table of Contents Introduction....................................................................................................
1-1 1.1 Purpose 1-1 1.2 Scope of Work..................................
1-1 1.3 Report Organization.........................................................................
1-1 2
Field Investigation 2-1 2.1 Drilling Activities 2-1 2.1.1 Baby Wells in Protected Area................................................
2-1 2.1.2 Downgradient Well Clusters....................
- ..... 2-2 2.1.3 Repair of Well DSP149.......................
2-3 2.1.4 W ell Development.................................................................
2-4 2.2 Geophysical Logging.........................................................................
2-4 2.3 Land Surveying.................................
2-4 2.4 Water Level Measurements 2-5 2.4.1 October 2004 Measurements.................................................
2-5 2.4.2 April 2005 Measurements...,.................... 2-5 2.5 Slug Tests...........................................................................................
2-5 2.6 Groundwater Sampling............ ;......................................................... 2-6 2.7 Records Search...................................................................................
2-6 3
Geology and Hydrology.................................................................................
3-1 3.1 Regional Geology.................................
3-1 3.2 Site Geology.........................
..................... 3-2 3.2.1 Topsoil.............................................
.................................. 3-2 3.2.2 Pottsville Sandstone...............................................................
3-2 3.2.3 Divine Limestone...................................................................
3-2 3.2.4 Maquoketa Shale...........................
3-3 3.2.5 Galena Dolomite.......... *........................................................
3-3 3.3 Regional Hydrogeology............................
3-3 3.4 Site Hydrogeology............................................................................
3-3 3.4.1 Hydrogeologic Units...... :...................................................... 3-3 3.4.2 Groundwater Flow.................................................................
3-4 3.4.3 Slug Test Evaluation..............................................................
3-7 3.4.4 Residential Wells............................................
3-7 4
Tritium Results...............................................................................................
4-1 4.1 Shallow Groundwater Associated with CST System....................
4-1 4.2 Storm Sewers.....................................................................................
4-2 4.2.1 Flow Path of Storm Sewers.....................................................
4-2 4.2.2 Stormwater Flow and Drainage Areas..............
4-3 4.2.3 Potential Groundwater Ingress...............................................
4-3 4.3 Site-Wide Shallow Groundwater 44 4.4 Surface W ater.......................................
.............................................. 4-6 4.5 Off-Site M igration............................................................................
4-6 5
Tritium Impacts Evaluation....................................................................
5-1
Table of Contents 5.1 Regional Background Tritium Levels................................................
5-1 5.2 Tritium Mass Release Assessment................................................... 5-1 5.2.1 Shallow Groundwater Contribution.......................................
5-2 5.2.2 Storm Sewer Contribution................................................
5-4 5.2.3 Net Release ofTritium Mass................................................
5-5 5,3 Rate of Tritium Release.....................................................................
5-6 5.4 Potential Impacts to Groundwater.....................................................
5-6 5.4.1 Shallow Groundwater............................................................
5-6 5.4.2 Residential Wells..................................................................
5-8 6
Summary....................................................................................................
6-1 7
References.........................................
7-1 ii
List of Tables I
I Table 2-1 Monitoring Well and Surface Water Coordinates and Elevations Table 2-2a Table 2-2b Table 3-1 Table 3-2 Table.3-3 Table 3-4 Table 3-5 Table 4-1 Water Level Measurements - October 28, 2004 Water Level Measurements - April 4, 2005 Generalized Geologic Column Horizontal Hydraulic Gradient Calculations Vertical Hydraulic Gradient Calculations Slug Test Results Residential Well Information Tritium Concentrations - April 8, 2005 Table 5-1 BIOSCREEN Modeling Site-Specific Input Parameters
List of Figures Figure 1-1 Site Location Map Figure 2-1 Figure 2-2 Figure 3-1 Figure 3-2 Figure 3-3 Figure 3-4a Figure 3-4b Figure 3-5 Figure 4-1 Figure 4-2 Figure.4-3 Figure 4-4 Figure 4-5 Figure 4-6a Figure 4-6b Figure 4-7 Figure 4-8 Figure 4-9 Figure 4-10 Figure 4-11 Figure 4-12 Figure 4-13a Figure 4-13b Figure 4-14 Figure 4-15 Figure 5-1 Figure 5-2 Figure 5-3 Site-Wide Water Sampling Locations CST System Water Sampling Locations Geologic Cross Section Locations Geologic Cross Section A-A' Geologic Cross Section B-B' Water Table Contour Map - October 28, 2004 Water Table Contour Map - April 4, 2005 Residential Well Locations CST System Water Sampling Locations Tritium Concentration vs. Time in W-Series Baby Wells Tritium Concentration vs. Time in T-Series Baby Wells Tritium Concentration vs. Time in R-Series Baby Wells Tritium Concentration vs. Time in E-Series BabyWells Tritium Concentration Map Near CST System - September 3, 2004 Tritium Concentration Map Near CST System - April 8, 2005 Storm Sewer Layout and Tritium Concentration Map - September 1.
2004 Tritium Concentration vs. Time in Storm Sewers Site-Wide Water Sampling Locations Tritium Concentration vs. Time in Wells DSP124 and DSP125 Tritium Concentration vs. Time in Wells DSP105, DSP106, DSP107, DSP108, and DSP123 Tritium Concentration vs. Time in Wells DSP122, DSP148, DSP149, DSP155, and DSPli6 Tritium Concentration Map - September 3, 2004 Tritium Concentration Map - April 4,2005° Tritium Concentration vs. Time in Unit 2/3 Intake Canal, Cold Canal, and Unit 2/3 Discharge Canal Tritium Concentration vs. Time in Thorsen Well and Cold Canal Tritium Plume Mass Flux East of Release Area Mass Flux West of Release Area
List of Appendices Appendix A Appendix B Appendix C Appendix D Appendix E Appendix F Appendix G Soil Boring/Rock Coring Logs and Well Construction Diagrams Geophysical Logs Site Survey Map Slug Test Data Well Record Information Historic Tritium Concentration Data Mass Flux Calculations
Executive Summary Routine groundwater sampling undertaken at the Dresden Generating Station in July 2004 detected elevated levels of tritium in shallow monitoring wells and storm sewers located near the Unit 2/3 interlock building. The tritium was traced to a release from the Condensate Storage Tank (CST) system, through a pipe thatconnects to the station HPCI system. The leak was isolated on October 20, 2004, and a replacement section of pipe aound the tank was installed the following month.
The RETEC Group, Inc. (RETEC) was contracted by Exelon to characterize the nature of groundwater flow at the facility and evaluate the fate of the tritium, to assist Exelon in evaluating regulatory compliance issues and response options.
The scope of work for this project included reviewing historical data, installing additional monitoring wells, conducting geophysical logging in some deeper wells, surveying the locations of all monitoring points, performing two rounds of water level measurements, performing slug tests on selected wells, sampling groundwater for tritium concentrations, and evaluating all of the physical and chemical data to characterize groundwater flow and tritium migration. The field activities were completed in two 'phases between October 2004 and April 2005.
The geologic units underlying Dresden Station include, in descending order:
topsoil and overburden; the Pottsville (or Spoon) Formation, the Divine Limestone Member (or Ft. Atkinson Limestone), the Maquoketa Shale Member of the Maquoketa Formation, and the Galena Formation (Harza, 1991). The Maquoketa Shale separates the water table aquifer from the lower aquifers. The water table aquifer consists of the Pottsville Sandstone and the Divine Limestone Member, and the lower aquifer consists of Galena Formation. The water table is independent of the piezometric surface of the lower aquifers because the Maquoketa Shale is a sufficiently impermeable confining unit.
Groundwater flow conditions were characterized using the water level measurements collected on October 28, 2004 and April 4, 2005. There is a mounding effect in the area of the CST system which extends to the southeast.
The groundwater' flow direction in the immediate vicinity of the liquid nitrogen tank 'is to the,east and to the northwest. In the eastern half of the Protected Area(area within the owner-controlled area enclosed by a station security fence in which the main buildings are located), groundwater flows to the north toward the'Unit 1 intake canal.
West of the CST system groundwater flows westward toward the cooling canals.
South of the Protected Area, groundwater flows to the southeast and southwest with a groundwater divide oriented northwest-southeast.
Further south of the Protected Area in the residential area, groundwater flows from the cooling canals eastward to the Kankakee River.
Executive Summary The tritium-impacted groundwater is migrating in an easterly direction, as evident from the decrease in tritium concentrations in wells W3 and T6, and an increase in well TI. Tritium also appears to be migrating toward the west, based on the sudden increase in tritium concentrations in well DSP124 located northwest of the CST system. The groundwater impact from the CST system release is confined to a small area, well within the Protected Area.
The total mass of tritium discharged to groundwater flow east of the CST system was calculated as 4.18x10' 2 pCi, and the total mass of tritium discharged to groundwater flow west of the system was calculated as 1.81x10'1 pCi. Based on a tritium concentration in the CST system of 9 to 10 million pCi/L, the combined mass (discharged to the east and west groundwater. flow) equates to approximately 121,000 gallons of tritiated water released to groundwater.
The total mass of tritium discharged to the eastern storm sewer system, which outlets into the Unit 1 intake canal, was calculated as 5.27x102 pCi. The total mass of tritium discharged to the western storm sewer system, which outlets into the Unit 2/3 discharge canal, was calculated as 7.33x1010 pCi. Based on an estimated tritium concentration in the CST-system of 9 to 10 million pCi/L, this combined mass equates to approximately 148,000 gallons of tritiated water released to the storm sewer.
The combined tritium mass discharged to the groundwater and to the storm sewer from the CST system is calculated as.9.63x1012 pCi. Based on an estimated tritium concentration in the CST system of 9 to '10 million pCiIL, the total mass released equates to approximately 267,000 gallons of tritiated water. The average rate of tritium released to the groundwater and sewer systems, assuming that the total mass of tritium was released over the duration of the discharge from the CST system (i.e., 344 days between November 2003 and October 2004), amounts to 2.80xl 010 pCi per day.
Based on fate and transport computer modeling (BIOSCREEN), the concentrations of tritium at the source and along the western plume will decrease. to below 90 pCi/L within approximately 5 years of the pipe repair.
Similarly, the concentrations at the source and along the eastern plume will drop below 290 pCi/L within approximately 8 years of the repair.
RETEC's investigation revealed that the bulk of the tritium discharged to groundwater from the CST system is flowing toward the east and northwest under the influence of the local hydraulic gradient. The tritium plume is not likely to come under the influence of the regional gradient in the southeasterly direction, and thereby impact-res*_ctial wells located south of Dresden Station. Tritium sampled in th6ell, which is located approximately 3,400 feet south of the Station, ot b ieved to be associated with the CST system release. Rather, it appears this well influenced by concentrations of tritium in the nearby cooling canals.
1 Introduction Routine groundwater sampling results undertaken in July 2004 detected elevated levels of tritium in shallow monitoring wells and storm sewers located near the Unit 2/3 interlock building. The tritium was traced to a release from the Cohdensate Storage Tank (CST) system, through a pipe that Connects to the station HPCI system. The leak was isolated on October 20, 2004, and a replacement section of pipe around the tank was installed the following month.
The RETEC Group, Inc. (RETEC) was contracted by Exelon Nuclear (Exelon) to characterize the nature of groundwater flow at the facility and evaluate the fate of the tritium. The facility is located near Morris, Illinois at the comer joining Sections 25, 26, 35, and 36, Township 34.North, Range 8 East, Grundy County, Illinois (see Figure 1-1). This report presents the results of the investigation conducted at Dresden Station by RETEC between October 2004 and April 2005.
1.1 Purpose The purpose of the investigation was to determine the nature of the groundwater flow and tritium concentrations within the area that could be affected -by the CST system release and to assist Exelon in evaluating regulatory compliance matters..
1.2 Scope of Work The scope of work for this project included reviewing historical data, installing additional monitoring wells, conducting geophysical logging in some deeper wells, surveying the locations of all monitoring points, performing two rounds of water level measurements, performing slug tests on selected wells, sampling groundwater for tritium concentrations, and evaluating all of the physical and chemical data.
The data obtained in this investigation along with the results of this evaluation are presented this report. The historical data included more than 10 years of groundwater analytical data, residential well records, several rounds of water level measurements, and technical reports. The field activities are described in more detail in Section 2.
1.3 Report Organization This report contains seven se-ions and seven appendices. Section 1 provides introductory information -
-cbding purpose and scope of work. Section 2 describes the field activities performed at the site. Section 3 summarizes the regional and site-specific geologic and hydrOgeologic environments. Section 4 presents the tritium results from groundwater and surface water samples.
Section 5 addresses the potential tritium impacts and the regulatory
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois framework for tritium.
Section 6 summarizes the findings of this investigation. Section 7 lists the sources of information references relied upon to support the preparation of this report.
Appendix A contains soil boring and rock coring logs, and well construction diagrams. Appendix B contains geophysical logs. Appendix C contains the site survey map. Appendix D contains the slug test data. Appendix E contains well record information. Appendix F contains historical tritium concentration data. Appendix G contains the mass flux calculations.
2 Field Investigation The field activities were completed in two phases between October 2004 and April 2005. The first phase included surveying the locations and elevations of all existing sampling points; measuring water levels from these sampling points; and installing four shallow wells ("baby" wells) to monitor the CST system. The second phase included the installation of nine monitoring wells (three clusters of three wells each) further south of the CST system to monitor groundwater quality in the direction of residential properties, and the repair of existing monitoring well DSP149 due to anomalous data. It also included surveying and water level measurements after the new wells were installed, geophysical logging, slug testing, records search of residential wells, and a round of groundwater sampling. It should be noted that during this project Dresden Station continued its monitoring/sampling program. The sampling results obtained from the program are also presented in this report.
2.1 Drilling Activities The drilling activities for this project included the installation of shallow wells in the Protected Area near the CST system, the installation of three dowvgradient well clusters south of the Protected Area toward the Kankakee River and the adjacent residential neighborhood, and the repair of existing well DSP149. The locations of the wells are shown in Figures 2-4 and 2-2.
The procedures used to install each of these wells are summarized in the following subsections.
2.1.1 Baby Wells in Protected Area There were 1S shallow, "baby wells" monitoring. tritium concentrations in groundwater near the water table prior to the detection of the release. During construction activities to locate and repair the pipe from the CST system, five wells (T3, T4, T7, Wl, and W2) were removed. Four new wells (E8, E9, ElO, and W2R) were installed on November 23, 2004 to enhance the network of wells used to monitor any potential release from the CST system. Figure 2-2.
shows the location of each baby well included in the CST system monitoring well network.
The new wells were installed by Trench-It, Inc. (Trench-It) of Union, Illinois, and Testing Services Corporation (TSC) of Carol Stream, Illinois. Trench-It performed private utility locating services, and was contracted to ensure each drilling location was clear of all utilities. Due to the shallow water table in the area (4 to 8 feet below ground surface), and the engineering manager's concern forunderground utilities, Trench-It's air knife and vacuum truck were used instead of the drill rig to advance each boring. The diameter of each boring varied depending on subsurface conditions affecting the air knife's
'performance.
Final Draft Groundwater Tritium Investigation Report -Dresden Generating Station, Morris, Illinois TSC personnel constructed each well using 2-inch inside diameter (ID) polyvinyl chloride (PVC) risers with 2 to 5 feet long PVC screens at the bottom. A sand pack was placed around the screen to approximately 2 feet above the screen and a bentonite seal was extended to the ground surface.
The depth of these wells varies from 5.5 to 7.2 feet below ground surface.
The wells were completed as flush-mounts with steel vaults and concrete pads. Well construction diagrams are included in Appendix A.
2.1.2 Downgradient Well Clusters Three well clusters were installed to monitor groundwater quality at the water table,. immediately above the lower confining unit of the shallow aquifer, and immediately below this confining unit. Well cluster DSPI57 was located downgradient of the CST system outside of the Protected Area to monitor on-site water quality. Well cluster DSP158 was located southeast of the CST system near the Kankakee River to monitor the potential for impacting the river. Well cluster DSP159 was ooate. douth of the CST system, adjacent to the cooling canals and near th ell, to monitor the potential for impacting the downgradient resi entia wells. The locations of these well clusters are shown in Figure 2-1.
At each location, the shallow water table well was designated with a "S", the intermediate well immediately above the confining unit was designated with a "M", and the deep well immediately below the confining unit was designated with a "D". The lithology for all of the wells, except for DSP159D, were logged by observing the drill cuttings exiting the borehole as drilling advanced. Well DSP159D was logged by collecting and observing rock cores from-the top of competent rock to bottom. The lithology was described using the Unified Soil Classification System (USCS) and the Field Guide for Rock Core Logging and Fracture. Significant features, such as moisture and soil or rock composition, were noted on the logs. Soil-color was referenced using the Munsell Soil Color Chart, and rock color was referenced using the Geologic Society of America Rock-Color Chart. The soil boring and rock coring logs, and well construction diagrams are included in Appendix A.
The shallow wells (DSP157S, DSP158S, and DSPI59S) were installed using-4-1/4 inch ID hollow stem augers to drill through the topsoil and the sandstone, where present. The wells were drilled to depths varying "from 13 to 16 feet below gr6und surface so that the top of the 10-foot screen would be set approximately 3 feet above the water table. The wells were constructed of 2-inch ID PVC risers with 10-foot lengths of 0.010-inch slotted screens. Sand filter pack was placed in the annular space around the screen, with 0.5 to 1 foot of sand below the well and 1 to 2 feet above the top of the screen. A 2-foot thick bentonite seal was placed above the filter pack. The shallow wells were completed as stick-up wells with 4-inch diameter steel protective casings set in 2-by 2-feet concrete pads.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois Drilling of the intermediate and deep wells started by using 6-1/4 and 8-1/4inch ID hollow stem augers, respectively, to refusal within the limestone. A tri-cone rotary bit was initially used to drill through the limestone, but due to very slow drilling rates, the tri-cone rotary bit was replaced by an air hammer.
The air hammer was used to drill through the shale and the dolomite in the deep wells. The intermediate wells (DSP157M, DSP158M, and DSP159M) continued drilling with a 6-inch diameter air hammer into the upper 1 to 2 feet of the shale, at depths ranging from 5i to 59 feet below ground surface.
The deep wells continued drilling with a 8-inch diameter air hammer into the upper 2 feet of the shale and installing 6-inch diameter steel casings. The casing was grouted in place and allowed to set for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to drilling through the shale and into the dolomite. Wells DSP157D and DSP158D were drilledusing a 6-inch diameter air hammer to total depths of 130.5 and 135 feet below ground surface, respectively. Well DSP159D was drilled using NXWL wireline rock coring equipment with NQ-sized casing to a total depth of 139 feet below ground surface. Rock cores were collected in 5-foot long wooden boxes with four columns per box. Following coring, the borehole was reamed using a 6-inch diameter air hammer.
The intermediate and deep wells were constructed of 2-inch ID PVC risers with 10-foot lengths of 0.010-inch slotted screens.
Sand filter pack was placed in the annular space around the screen, with approximately 1 foot of sand below the well and 2 feet of sand above the top of the screen. A 2-foot thick bentonite seal was placed on top of the filter pack, and the seal was allowed to hydrate before the remainder of the annular space was filled with grout. The intermediate and deep wells wgre completed as stick-up wells with 4-inch diameter steel protective casings set in 2-by 2-feet concrete pads.
2.1.3 Repair of Well DSP149 Since December 1996, well DSP149 has yielded anomolous water level measurements and tritium concentration values when compared to surrounding monitoring wells. The average depth to water in nearby wells is approximately 12 feet, but the depth to water in well DSP149 typically has been greater than 40 feet below ground surface.
The average tritium concentration in well DSP155 has been 880 picocuri'es per liter (pCi/L) since August 1997. The average concentration in well DSP156 has been 230 pCi/L since February 2002. Both of these wells are located within 60 to 90 feet from well DSP149. The tritium concentration in well DSP149 varied from 404 to 76,488 pCi/L from August 1995 through February 2005.
Due to the anomalous results from well DSP149, it was determined that well DSP149 was not yielding representative data, and, should be removed and replaced.
The location of this well is shown in Figure 2-1.
Well DSP149 was overdrilled using an air rotary rig with a 6-inch diameter tri-cone roller bit. The protective casing and concrete pad were removed prior to overdrilling. The monitoring well was overdrilled to a total depth of 51 feet
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois below ground surface, which is approximately 2 feet deeper than the original boring. A new well was constructed of 2-inch ID PVC riser with a 10-foot length of 0.010-inch slotted screen. Sand filter pack was placed around the annular space of the screen, with approximately 1 foot of sand below the well and 2 feet of sand above the top of the screen. A 2-foot thick bentonite seal was placed on top of the filter pack, and the seal was allowed to hydrate before the remainder of the borehole was filled with grout. The well was completed as a stick-up well with a 4-inch steel protective casing set in a 2-by 2-foot concrete pad. The soil boring log and well construction diagram are included in Appendix A.
2.1.4 Well Development Following the installation of the monitoring wells, TSC developed the new monitoring wells using a modified hand pump, a whale pump, or a bailer. The purpose of the well development is to remove silts and other fine-grained sediments from within the well and surrounding formation. The shallow and intermediate wells were developed until clear water was sustained, except for well DSP157S and DSP159S (well went dry).
Approximately six well volumes were purged from the shallow and intermediate wells. The deep wells were developed by adding water, surging the water, and then purging them dry due to dry conditions in these wells.
2.2 Geophysical Logging Natural gamma ray and electromagnetic (EM) induction logging were performed on five selected wells (DSP157D, -DSP158D, DSP159M, DSP159D, and DSP149), by Century Geophysical Corporation (CGC) of Tulsa, Oklahoma on March 16, 2005. The natural gamma ray logs show lithologic changes and show zones with significant clay content. The EM induction logs were used in correlation with the gamma ray logs to identify water bearing zones. CC_
logged the wells using a logging tool. The logging tool was lowered to the bottom of each well and then lifted through the borehole while recording the geophysical measurements. EM. induction was not effective through the steel casing of each deep well; ho wever, natural gamma ray measurements of the lithology were recorded through the casing.
The geophysical logs are included in Appendix B.
2.3 Land Surveying Atwell-Hicks, Inc. of Naperville, Illinois was contracted to perform a land survey to generate a facility map showing the locations of all wells, storm sewers, and major features of the power plant.
An initial survey was performed during the period of October 21, 2004 through October 28, 2004.
The surveyors provided northing and easting coordinates for all locations. For the monitoring wells, elevations were recorded for the ground. surface, top of the riser, and top of the protective casing. For the surface water locations, the surveyors cut a permanent mark into a concrete surface on a bridge or platform and measured the elevations from those marks. Elevations for the
Final Draft Groundwater Tritium Investigation Report -Dresden Generating Station, Morris, Illinois storm sewers were measured from the tops of the grates or the edges of the manhole covers. An additional survey was performed on April 4 and 5, 2005 to include the newly installed wells and additional locations not included in the first survey.
Table 2-1 provides a list of all sampling locations and includes their coordinates and measured elevations. A site survey map is included in Appendix C.
2.4 Water Level MeasurementS Two rounds of water levels were measured to characterize groundwater flow directions beneath the site. Water-levels were measured from all accessible monitoring wells, storm sewers, and surface water measuring points. An electronic water level indicator was used, and measurements were recorded to the nearest 0.01 feet. The first round was performed in October 28, 2004 prior to installing any additional wells. New security fences were being installed at the time of the first round of measurements, and these new fences made some of the measuring points inaccessible during the second round of measurements. The second round was performed in April 4, 2005 after the four baby wells inside the Protected Area and the three well clusters south of the Protected Area were installed and well DSPI49 was repaired.
2.4.1 October 2004 Measurements The first round of water level measurements was collected on October 28, 2004 (Table 2-2a). The baby wells located near the CST system were not accessible due to construction; therefore, measurements could not be obtained from the T-and W-series wells, and storm sewers L and M.
2.4.2 April 2005 Measurements The second round of water level measurements was collected on April 4, 2005 (Table 2-2b). The new wells were included in this round of measurements.
Baby wells T3, T7, W1, and W2 were removed during pipe repair activities; however, well W2R was installed to replace water level measurements near wells Wl and W2.
Storm sewer M was also removed during these construction activities.
2.5 Slug Tests Slug tests were,performed on 10 selected monitoring wells (DSP157S,
- DSP157M, DSPI58S,. DSP158M,
- DSPl58D, DSP159S,
- DSP159M, DSPl579D, DSP149, and DSP121) to calculate the hydraulic conductivity of the upper (water table) and the lower aquifers. The shallow wells were used to calculate the hydraulic conductivity in the upper portion of the water table aquifer, and the intermediate wells were used to calculate the hydraulic conductivity. in the lower portion of the water table aquifer.
Slug" tests performed in the shallow and intermediate wells used a 5-foot long solid slug to displace water. A 30-psi pressure transducer was placed more than 5 feet below the water level in order to record drawdown changes during the test.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois To perform slug tests in the deep wells, 20 gallons of water was added to each well due to the limited amount of water in the wells.
Drawdown was measured using an electronic water level indicator. Due to. the slow recovery, measurements began at 15-second or 30-second intervals, and then increased to 1-and 5-minute intervals after 10 and 20 minutes, respectively. The data from the test were entered in the AQTESOLV for Windows Pro software (HydroSolve, Inc., 2000) to calculate hydraulic conductivity. The slug test data are included in Appendix D.
2.6 Groundwater Sampling, A complete round of water sampling was performed on April 8, 2005.
RETEC personnel sampled the newly installed well clusters.
Dresden personnel sampled the storm sewers and the monitoring wells in the Protected A.rea, and their sampling contractor sampled the monitoring wells outside the Protected Area. A total of 54 water samples were collected (including five duplicates). The storm sewers were sampled using a Teflon dipper. All the monitoring wells, with the exception of the deep wells, were sampled using disposable bailers to prevent cross contamination.
The deep wells were essentially dry and did not have sufficient groundwater to collect samples.
Prior to sampling, each well was purged of three well casing volumes using a bailer or a pump.
Also the depth to the water was measured.
Each groundwater sample consisted of two 1-liter bottles, one for tritium analysis and the other for general chemistry parameters (pH, conductivity, and alkalinity). Dresden Chemistry performed the general chemistry analyses, and the tritium samples were shipped to Environmental, Inc. Midwest Laboratory of Northbrook, Illinois for analysis.
2.7 Records Search Local water well and boring logs, dating from the early 1900's through the 1980's, were provided upon request from the Illinois State Geologic Survey (ISGS) to help characterize the hydrogeologic conditions in the vicinity of the facility. These logs were used to identify. the thickness of the upper aquifer, and the depth and thickness of the underlying shale.
The well records provided by the ISGS included well depths and construction details; however, the 'locations of these. wells were only identified by township, and range information and the property owner at the time of installation.
This information could not be used to determine the exact location of the wells, and a later correlation of some of the residential wells demonstrated a discrepancy of over 1,000 feet from the locations. shown from the ISGS data. The well records obtained from ISGS are included in Appendix E.
Exelon provided a list of current property owners in the neighborhood immediately south of the facility and parcel numbers to RETEC. A records search was conducted at the, Grundy County Recorder's Office in an attempt to match current property owners with the ISGS well records.
RETEC
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois researched property transaction records to match them to the owners recorded on the water well permits. Computerized deed transactions were available only as far back as th6 late 1970's, and records that needed to be researched to earlier dates had to be traced back in the original handwritten ledgers available in the recorder's office.
While several current owners could be traced back to the well records, there were several problems encountered during the research. Property transactions that were deeded to a bank or a trust effectively terminated a direct chronological link since RETEC would then have to look at all property transactions from that institution making the continuation of the records search not reasonably ascertainable. Another problem encountered was that the deeded property owner might not have signed the signatures on the original well permits, thus making a correlation of records impossible.
3 Geology and Hydrology The stratigraphic terms used in this report are consistent with the terms used in the soil boring and well construction logs provided by the ISGS, and the Dresden Groundwater Study by Harza (1991), which were the primary sources of geologic information for this investigation. These documents refer to the Pennsylvanian sandstone encountered at shallow depths as the Pottsville Sandstone, and the underlying limestone is called the Divine Limestone Member of the Maquoketa Formation. These terms are not consistent with the Summary of the Geology of the Chicago Area - Circular 460 by Willman (1971).
According to Willman (1971), the Pennsylvanian sandstone is typically assigned to the Spoon Formation, and the underlying limestone is the Fort Atkinson Limestone of the Maquoketa Group.
3.1 Regional Geology The geologic layers of interest underlying Dresden. Station include, in descending order: topsoil and overburden, the Pottsville Formation, the Divine Limestone Member of the Maquoketa Formation, the Maquoketa Shale Member of the Maquoketa Formation, and the Galena Formation (Harza, 1991). The topsoil and overburden consists of sands and sandy clays, and ranges in thickness from 0 to 30 feet.
Due to irregular erosion of the Maquoketa Formation, there are outcrops of limestone north of the facility in areas where the Pottsville Formation and topsoil are absent.
The Pottsville Formation is predominantly sandstone exhibiting prominent cross bedding, as is shown in the outcrops along the intake and discharge canals. The sandstone also contains thin seams of carbonaceous material and calcium carbonate cement. The amount of cementation varies horizontally and vertically. The sandstone is absent north of the facility, and in some areas west and southeast of the facility. According to Haiza (1991), the Pottsville Sandstone varies from 0 to 50 feet thick, and is underlain by the Divine Limestone.
The surface between the Pottsville Sandstone and Divine Limestone is an unconformity.
The Divine Limestone was deposited conformably on the underlying Maquoketa Shale. The contact between these two units is transitional in some areas, with alternating layers of calcareous clays and limestone. The Divine Limestone contains occasional stylolites, solution channels, joints, cavities, and thin layers of clay. The thickness of the Divine Limestone varies from 0 to 60 feet, and the elevation of the limestone surface also varies considerably (Harza, 1991).
The Maquoketa Shale consists of dark gray to dark green dolomitic shale with layers of shale and argillaceous dolomite. The regional thickness of the shale consistently ranges between 65 and 70 feet; however, the elevation of the shale surface varies significantly.
Both the Divine Limestone and the
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois Maquoketa Shale have a regional dip to the southeast of approximately 25 feet per mile.
The shale is underlain by the Galena Dolomite, which is approximately 230 feet thick.
3.2 Site Geology The geology at the site was characterized using ISGS well records and soil boring logs completed during construction of Dresden Station, previous investigation report by Harza (1995), and drilling activities performed as part of the this hydrogeologic assessment. The geologic units characterized in this section include the topsoil, the Pottsville Formation, the Divine Limestone Member, the Maquoketa Shale, and the Galena Dolomite.
The site stratigraphy is depicted on-two geologic cross sections. The locations of the geologic cross sections are shown in Figure 3-1. The geologic cross sections that were prepared for this report are presented in Figures 3-2 and 3-3.
3.2.1 Topsoil The topsoil consists of-highly oiganic dark brown to black sandy clay with some gravel. Where present, the topsoil typically ranges between 0 and 5 feet thick across the facility. Fill material consisting of gravel and sand replaces the topsoil within the Protected Area due to construction of the facility. Also, there is 12 feet of fill material along the east bank of the "hot" cooling canal near well cluster DSP159, which was is excavated material from the construction of the cooling towers..
The fill material near well Cluster DSP159 consists of sandy clay and limestone.
3.2.2 Pottsville Sandstone The Pottsville Formation encountered during drilling and characterized from existing logs is hard, pale brown to gray, medium-to coarse-grained sandstone.
Construction plans for the facility show the sandstone exists
..beneath the entire power plant, and the sandstone is also present south of the plant at well cluster DSP,157, The thickness of the sandstone near the facility ranges from 25 to 30 feet. The Pottsville Sandstone was not encountered during drilling at well clusters DSP158 or DSP159.
3.2.3 Divine Limestone The Divine Limestone is a white to gray crystalline limestone with pale green lenses of shale encountered near the top.of the Maquoketa Shale. Air rotary drilling through the limestone was very slow, with a drilling rate as low as 3 feet per hour, indicating a very dense limestone.
Drilling through the limestone using the air hammer at well clusters DSP158 and DSP159 yielded very little water until the drill bit approached the lower. 5 feet of the limestone.
The thickness of the Divine Limestone Member ranges from 25 to 50 feet across the site.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois 3.2.4 Maquoketa Shale The Maquoketa Shale underlying the Divine Limestone is a hard and very dark greenish gray shale that consists of layers of shale and argillaceous dolomite. The depth to the top of the shale from borings encointered on site range from 48 to 83 feet, The thickness of the shale obtained from the three deep wells (DSP157D, DSP158D, and DSP159D) installed into the Galena Dolomite, and the deep geotechnical soil boring advanced during construction of Dresden Station ranged from 64 to 68 feet.
3.2.5 Galena Dolomite The Galena Dolomite is a light brownish gray to pinkish white crystalline dolomite. Sub-horizontal and vertical fractures -were observed in the rock cores for deep well DSP159D from 132 to 138 feet below ground surface.
3.3 Regional Hydrogeology The Maquoketa Shale separates the water table aquifer from the two lower aquifers. The water table aquifer consists of the Pottsville Sandstone and the Divine Limestone Member of the Maquoketa Formation. The water table is independent of the piezometric surface of the lower aquifers because the Maquoketa Shale is a sufficiently impermeable confining unit. The lower aquifers are the Ancell Aquifer within the Ordovician System and the Ironton-Galesville Aquifer within the Cambrian System (Table 3-1).
These two aquifers have a common piezometric surface because there is no confining unit between them.
The lower aquifers are recharged from surface water to the west and north of Dresden Station, where the Maquoketa Shale is discontinuous in some areas.
Vertical migration downward from the water table aquifer is impeded where the shale is present due to its low permeability. According to Harza (1991),
the piezometric surface for the lower aquifers is approximately 250 feet below ground surface in the vicinity of Dresden Station due to over-pumping in the area.
3.4 Site Hydrogeology The site hydrogeology was characterized using previous investigation reports, well records. and soil boring logs provided by ISGS, observations during drilling the newly installed wells, and slug test results. Also several rounds of water level measurements collected over several years, and tritium concentrations measured from. monitoring wells, storm sewers and surface water bodies were used to evaluate on-site groundwater flow conditions and off-site movement of groundwater.
3.4.1 Hydrogeologic Units The water table aquifer consists of the saturated overburden, the Pottsville Sandstone, and the Divine Limestone. This aquifer is monitored by several
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois shallow monitoring wells screened across the water table, and 35-and 50-foot deep wells screened in the limestone. The Maquoketa Shale is the lower confining unit to the water table aquifer. The lower aquifer consists of the Galena Dolomite. It appears that the upper portion of the Galena dolomite is unsaturated as indicated by the dry conditions in the deep wells. The dry deep wells demonstrated the lack of hydraulic interconnection between the water table aquifer and the lower aquifer, and confirmed the occurrence of substantial dhiwdown of the piezometric surface in the lower aquifer.
3.4.2 Groundwater Flow Groundwater flow conditions were characterized using the water level measurements collected on October 28, 2004 and April 4, 2005. Figures 3-4a and 3-4b present the water table contour maps of October 28, 2004 and April 4, 2005, respectively, constructed from the monitoring wells installed in the water table aquifer. Both figures show a similar groundwater flow pattern in the water table aquifer.
According to Figures 3-4a and 3-4b, there is a mounding effect in the area of the CST system which extends to the southeast.
The groundwater flow direction in the immediate vicinity of the liquid nitrogen tank is to the east and to the northwest. In the eastern half of the Protected Area, groundwater flows to the north toward the Unit 1 intake canal.
West of the CST system, groundwater flows westward toward the cooling canals.
South of the Protected Area, -groundwater flows to. the southeast and southwest with a groundwater divide oriented northwest-southeast from well DSP124 to DSPl52.
Further south of the Protected Area in the residential area, groundwater flows from the cooling canals eastward to the Kankakee River.
Horizontal Gradients The water table across most of the Protected Area slopes to the north and northeast toward the Unit 1 and Unit 2/3 intake canals. The horizontal.
hydraulic gradient values in the vicinity of the CST system calculated from the water table contour maps were 0.022 and 0.014 ft/ft to the northeast on October 28, 2004 and April 4, 2005, respectively.
Table 3-2 presents horizontal hydraulic gradient calculations within the Protected Area in the vicinity of the CST system and to the west of the CST system, and also presents calculations outside of the Protected Area to the east, southeast, and south. The average horizontal hydraulic gradient outside of the Protected Area ranges from 0.0046 ft/ft toward the southwest.to 0.035 ft/ft toward the northeast.
Normal Flow Conditions The water table contour maps presented in Figures 3-4a and 3-4b show a consistent pattern of radial flow within.the facility boundary with a groundwater divide in line with wells DSPI24 and DSP152. Although water
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois level elevations differ across the site by 1 to 2 ft between the October 28, 2004 and April 4, 2005 water level measurements, the similar patterns indicate both these maps represent normal groundwater flow conditions.
Influence of the Release Water levels were not measured in the baby wells located in the vicinity of the CST system prior to October 28, 2004. During the October 28, 2004 water level gauging event, only the E-and R-series of baby wells were accessible due to construction activities associated with repairing the pipe from which a release occurred. Baby wells E8, E9, El0, and W2R were not installed until November 2004; therefore, the water levels on at these locations could not be measured during this event.
The April 4, 2005 water table contour map shows that the highest groundwater elevations exist in the vicinity of the W-, T-, and R-series of baby wells (Figure 3-4b). Although the W-and T-series of wells were not accessible during the October 28, 2004 gauging event, Figure 3-4a shows that the highest groiudwater elevations were measured in the E-and R-series of wells. monitoring the CST system.
These higher groundwater elevations suggest the release may have influenced the water table. However, due to the porous nature of the fill material and underlying sandstone, this effect is most likely localized.
Influence of Facility Construction The ground surface elevation at Dresden Station is approximately 517'feet above mean sea level (msl), and the average water table elevation is approximately 5 10 feet msl. Construction drawings for Dresden Station show that excavations to construct the Unit 2/3 turbine building are typically deeper than 500 feet msl and are as deep as 463 feet msl. Portions of the building are constructed directly on top of the Maquoketa Shale; therefore, groundwater flow in the water table aquifer is affected throughout its entire thickness around the facility. The hydraulic gradient shows groundwater flows toward the building with preferential lateral flow around the building to the east and west.
This also can create a groundwater mounding effect around the building.
Following the installation of a new section of pipe to bypass the release area, the holes excavated east and west of the Unit 2/3 interlock building were backfiUed with 20 percent strength grout to within approximately 1 foot of the ground surface. The remainder of the holes was backfilled with excavated materials, and a thermal berm was constructed over the new pipe to provide weather protection.
The grouted material created local zones of lower hydraulic conductivity which will cause the groundwater to flow around these areas.
Influence of Surface Water Bodies
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois Dresden Station is surrounded by surface water bodies, as shown in Figure 1-1, which have a significant effect on groundwater flow. The facility is bordered by the Kankakee River to the east, the Des Plaines River to the north, and the hot and cold cooling canals to the west and south. The Kankakee River, the Des Plaines River, and the cooling canals act as boundary conditions and in fact control the groundwater flow. The Kankakee River supplies the Unit 1 and Unit 2/3 intake canals that flow along the northeastern edge of the Protected Area. Two discharge canals are located north of the Protected Area, as is the recycling canal.
A residential neighborhood is also encircled by the cooling canals and the Kankakee River.
The normal pool elevation for the Kankakee and Des Plaines Rivers, which join to form the Illinois River, is 505 feet msl.
The pooi elevation is controlled by the Dresden Island Lock and Dam, located approximately 3,000 feet northwest of Dresden Station.
This also controls the surface water elevations in the Unit 1 and Unit 2/3 intake canals and the Unit 1 discharge canal. The Unit 1 intake and discharge canals are basically stagnant water bodies since the Unit I reactor is not operating. Groundwater from Dresden Station flows toward the Kankakee and Des Plaines Rivers as shown in Figures 3-4a and 3-4b.
Water from the Unit 2/3 discharge flows south along the western edge of Dresden Station in the "hot canal", then turns to the southeast and is pumped at a lift station into Dresden Cooling Lake. Water is returned by gravity drainage in the "cold canal", located west of the hot canal. Both canals are unlined flumes cut into the bedrock. The hot canal is approximately 12 feet deep, and the bottom of the flume is at a lower elevation than the cold" canal and the groundwater at Dresden Station.
Both Figures 3-4a and 3-4b demonstrate that groundwater from Dresden Station flows toward the hot canal in the immediate vicinity of the plant.
The surface water elevation in the cold canal is higher than in the hot canal, and it is also higher than the groundwater elevation in the vicinity of the well cluster DSP159 and the Thorsen well. These data demonstrate that the cold canal is a source of recharge for the groundwater south of the plant.
Vertical Gradients Vertical 'hydraulic gradients were calculated using the April 4, 2005 water.
level data from the shallow and intermediate wells located at the new well clusters (DSP157, DSPI58, and DSP159). The vertical gradient calculated at well DSP 157, which is closest to the Protected Area, was 0.0032 ft/ft with an upward component. The vertical gradients calculated at wells DSP158 and DSPI59 were 0.017 and 0.0044 ft/ft, respectively, with downward components. The vertical gradient at well DSP158 located near the Kankakee River was greater than the gradient for well DSP159 located.between the Thorsen well and the hot canal. Table 3-3 summarizes the vertical hydraulic gradient calculations for the three well clusters.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois 3.4.3 Slug Test Evaluation The slug test data were evaluated using the AQTESOLV for Windows Pro software (HydroSolve, Inc., 2000). For this data set, the software employed the Bouwer and Rice test method for unconfined aquifers (Bouwer and Rice, 1976). The geometric mean of hydraulic conductivity values calculated for the shallow wells (DSP157S, DSP158S, and DSP159S) were two orders of magnitude greater than the geometric mean for the intermediate wells (DSP157M, DSP158M, and DSP!59M) installed just above the shale. The geometric mean of hydraulic conductivity for the shallow wells is 2.4x10"2 fl/min (34.2 ft/day), which is characteristic of unconsolidated sands or porous sandstone (Freeze and Cherry, 1979).
The geometric mean of hydraulic conductivity for the intermediate wells is 4.7xlO"4 ft/min (0.67 fl/day). Table 3-4 summarizes the slug test results for the shallow and intermediate wells.
The slug test data analysis is included in Appendix D.
The slug tests in the deep wells could only be qualitatively analyzed because they were performed predominantly in unsaturated zones of the Galena Dolomite. For well DSP158D, the initial displacement was'58.5 feet, and there was only 50 percent recovery after 60 minutes. For well DSPl59D, the initial displacement was 38 feet, and there was only 64 percent recovery after 60 minutes. Both test results could not adequately be analyzed but indicate a relatively low hydraulic conductivity.
3.4.4 Residential Wells A records search was performed to correlate residential water wells to the ISGS well records. Six well records were correlated to residential properties ca* *suth of Dresden Station. 'None of thes cords corresponded to the located at Harza (1991). referred to Flle¶Dt3) ord wasinc ell as 110 feet ep'; howevernoel rec luded in tat rep and none of the records provided by the-ISGS.
onded to that depth. The two nearest records located ne indicate a, depth of 110 feet would be in the bottomo e0 shale rA in dolomite. The well records also did not correspond t where low tritium concentrations, were detected The approxi1mtcations of the residential wells are shown in Figure 3-5.
The residential wells were typically cased to 40 feet below ground'surface and completed'at d
,f well identified by ISGS Record
- 2072, located a was installed to 101 feet below ground surface, the well rd did not entift or thckness of the shale in this boring. Therefore, it is unknown from which formation this well pumps water. Another well, ISGS Record #2.2798, had a casing set at 58 feet below ground surface. Since all of the wells, except ISGS Record #22798, had casings set at 40 feet below ground surface and the depth to shale was consistently 60 feet below ground surface, these wells are partially pumping water from the upper aquifer as water flows down the open hole beneath the casing outside of the pump. Also the well identified by ISGS Record #22798
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois receives some water from the upper aquifer since the casing is set 2 feet above the top of the shale. Well construction and property identification information is presented in Table 3-5. A property map of the. Thorsen Subdivision is included in Appendix E, along with the ISGS well records that were matched to residential properties.
4 Tritium Results Tritium concentrations were obtained from groundwater, storm sewer, and surface water samples obtained from the Dresden Station under a long-term monitoring program. Upon review of data obtained from a July 31, 2004 sampling event, the presence of a release from the CST system was identified.
Elevated tritium concentrations were detected in three storm sewers and all of the sampled baby wells. The following sections discuss the effect of the release on the tritium concentrations in the shallow groundwater near the CST system, and the tritium concentrations in the groundwater outside the CST system area and in the surface water. Also, the potential for off-site migration of tritium to the residential area south of the station is discussed.
The historical tritium concentration data are provided in Appendix F.
4.1 Shallow Groundwater Associated with CST System The shallow groundwater in the vicinity of the CST system is monitored by the W-, T-, R-, and E-series baby wells (Figure 4-1). The W-series baby wells monitor the groundwater located east of the liquid nitrogen tank and west of the Unit 2/3 interlock building. On July 31, 2004, the tritium concentrations detected in wells WI and W3 were 3,612,931 and 6,125,891 pCi/L, respectively. The highest tritium concentration from any of the water samples was recorded from well W3, located adjacent to the interlock building, on September 3, 2004 at 10,312,000 pCi/L. Well WI was located west of well W3 and had a concentration of 2,594,000 pCi/L on September 3, 2004. Well W2 was dry during this period; therefore, groundwater samples could not be collected from this location. Baby wells WI and W2 were later removed during construction activities.
Following repair of the -broken pipe, in November 2004; tritium concentrations decreased drastically in well Y3. This well had a concentration of 542,667 pCi/L on November 22, 2004, which decreased to 161,000 pCi/L on May 19, 2005.-Replacement well W2R was instilled on November 23, 2004 to rbplace baby wells W1 and W2, which were removed during construction activities.
Another well was attempted further west; h6wever, there were too many utilities in the area to risk using a hollow-stem auger rig to drill. 'Also the Pottsville Sandstone was encountered too shallow to intercept the water table using the air knife to drill a hole. Tritium concentrations in well W2R ranged from 48,000 to 301,000 pCiIL in three samples collected between December 2, 2004 and February 1, 2005, and then dropped to 182,000 pCiIL in May 19, 2005. The changes in tritium concentration with time in the W-series baby wells are presented in Figure 4-2.
The T-series baby wells monitor the groundwater located east of the Unit 2/3 interlock building. On July 31, 2004, the tritium concentration in well T6 was 1,960,331 pCiIL, which was the highest concentration measured in these wells
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois before the pipe was repaired. Analytical results from baby well T5, which is located approximately 7 feet east of T6, reported a tritium concentration of 41,662 pCi/L on July 31, 2004 and a maximum concentration of 404,437 pCi/L on August 28, 2004.
Baby wells T7 and T3 were located approximately 10 feet south of wells T6 and T5, respectively, before their removal during construction activities. The maximum concentration for well T7 was 958,000 pCi/L measured on September 3, 2004, and the maximum concentration for well T3 was 119,763 pCi/L measured on August 28, 2004.
Tritium concentrations gradually increased in baby well TI, located approximately 35 feet east of well T3, from 7,473 to 131,000 pCi/L by March 8, 2005. The April 8, 2005 groundwater sample yielded a result of 262,990 pCi/L.
Subsequent concentrations in well TI from April and May 2005 ranged from 189,000 to 252,000 pCiIL. The maximum concentration in baby well T2 located adjacent to T1 was 58,000 on October 25, 2004. The tritium concentration in well TI has remained near 5,000 pCiIL since the pipe was repaired. The changes in tritium concentration with time in the T-series baby wells are presented in Figure 4-3.
The R-and E-series baby wells also experienced increases in tritium concentrations as shown from the July 31,. 2004 sampling events; however, concentrations in these wells have typically remained near or below 5,000 pCi/L following repair of the pipe, with the exception of well R-2. In well R-2, tritium concentrations reached a maximum of 12,000 pCiIL on October 25, 2004 and then decreased to 3,000 pCi/L on April 25, 2005. It should be noted
-that baby'wells E8, E9, and E10 were installed on November 23, 2004. The changes in tritium concentration with time in the R-and E-series baby wells are presented in Figures 4-4 and 4-5, respectively.
Tritium concentrations for the baby wells in the vicinity of the CST system for September 3, 2004 and April 8, 20.05 are presented in Figures 4-6a and 4-6b, respectively. According to these figures, the tritium-impacted groundwater is migrating east as, evident from the decrease in tritium in wells W3 and T6, and an increase in well-fl. It is likely that the tritium isalso migrating west as indicated by the sudden increase in the tritium concentration in well DSP124 located northwest of the CST system The directions of plume migration are consistent with the horizontal hydraulic gradient in the vicinity of the CST system as described in Section 3.4.2.
4.2 Storm Sewers 4.2.1 Flow Path of Storm Sewers The storm sewer system layout has been determined from available data, such as catch basin location and depth, and utility drawings (Figure 4-7).
In addition, it has been assumed that the sewer pipe is aligned with the bottom of
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois the catch basins, thus the variation in the measured depth to bottom of the catch basins is representative of the slope of the sewer pipe. The depth to bottom of the catch basins ranged from 2.5 to 10 feet below ground surface.
In -the CST system area, the depth to bottom of the catch basins is approximately 2 feet below the water table. No additional catch basin or sewer system construction information was available for this report; therefore, it has been assumed that the roof gutter systems from turbine and office buildings drain directly to the local storm sewer, and that there is no immediate drainage to the storm sewer system from the bermed storage tank areas.
4.2.2 Stormwater Flow and Drainage Areas There appear to be two active sewer systems located in the vicinity of the CST system (Figure 4-7). Catch basins located on each of these sewer systems have been included as part of the tritium monitoring program. Two additional sewers appear to be located to the south of the turbine building. It appears that these unmonitored sewers drain to a stormwater drainage ditch located on the south edge of the plant.
One sewer appears to originate immediately to the east of the liquid nitrogen tank. The original terminus of this sewer was catch basin (CB) M, which was demolished during excavation activities related to the pipe repair. This sewer drains the area around the southeastern and northeastern perimeter of the turbine building, in addition to the portion of the site located between Unit 1 and the Kankakee River. This sewer. discharges to the Unit 1 intake canal through storm sewer DSP132, though the exact location of the discharge to the canal is unknown.
The second sewer originates immediately to the west of the liquid nitrogen tank and drains the area around the western perimeter of the turbine building, as well as the area to the northwest of the turbine building. This sewer drains to the Unit 2/3 disliarge canal through an outfall located in the west side of the canal. The -closest moritored catch basin to this outfall is storm sewer DSP131.
4.2.3 Potential Groundwater Ingress A total of 24 catch basins (storm sewers) have been included in the tritium monitoring program for the April 8, 2005 sampling event. Fifteen of these catch basins are located along the eastern sewer system, including (in order of proximity to the outfall) DSP132, CB A, CB B, CB C, CB D, CB E, CB F, CB G, CB H, DSP134, DSP140, CB J, CB K, DSP135, and CB M (removed).
Of the remaining 14 catch basins, elevated tritium concentrations have been detected in 11 since July 31, 2004. The only non-impacted catch basins appear tobe CB C, CB E, and CB H.
The highest tritium concentrations detected were 4,305,000 pCi/L in CB M and 3,000,000 pCiIL in DSPI35 during the September 2004 sampling event.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois The most recent sampling event for which data are available occurred in May 2005 and reported a tritium concentration of 129,000 pCiIL in DSP135. Only DSP135 (closest to the tritium source area), DSP132 (closest to the sewer outfall), DSP140 (downstream of DSP135), and DSPI34 (inside a bermed tank area near DSP140) have been continuously monitored since September 2004. The changes in tritium concentration in the storm sewers over time are presented in Figure 4-8.
Nine catch basins included in the tritium monitoring program are located along the western sewer system, including (in order of proximity to the outfall) DSP131, CB V, CB U, CB T, CB S, CB R, CB Q, CB N, and CB P.
The tritium concentrations in these catch basins with the exception of CN N, were between. 1,000 and 4,000 pCiIL. Tritium concentration in CB N was 16,000 pCiIL on September 1, 2004 and then dropped to.1,000 pCi/L on subsequent sampling on September 4, 2004.
Only DSP131 has been continuously monitored since September 2004.
Based on this data from the tritium monitoring program, tritium appears to have migrated mostly into the eastern sewer system and to a lesser extent into the western sewer system (Figure 4-7). It appears that the source of tritium in the eastern sewer system is from the CST system area, as samples from the catch basins immediately east of the liquid nitrogen tank (DSP135 and CB M) yielded the highest tritium concentrations.
Due to limited catch basin monitoring data in the western sewer system, the source of tritium is harder to identify. However, the increase in tritium concentration in DSP131 from 101 pCi/L in August 1, 2003 to 1,579 pCi/L in July 31, 2004 suggests that it was impacted by the release. The source of the tritium ingress is likely located along the sewer line between CB P and CB N, within the groundwater tritium plume.
4.3 Site-Wide, Shallow Groundwater The-,groundwater in the upper aquifer is monitored by 34 monitoring wells installed across the station, excluding the baby wells. The locations 'of these wells are shown in Figure 4-9. With the exception of three shallow wells, all other monitoring wells installed in the upper aquifer are 35 to 50 feet deep intermediate wells. The three shallow wells are 12 to 15 feet deep.
There are two wells, DSP124 and DSP125, located immediately northwest and east of the CST system area, respectively. Well DSP125 maintained consistently low tritium concentrations of less than 200 pCiIL. Well DSP124 on the other hand showed a steep increase in tritium concentration on August 1, 2004 at 91,166 pCi/L, followed by a decline to 4,060 pCi/L on April 8, 2005. This sharp increase corresponds to the release from the CST system detected on July 31, 2004. Prior to August 1, 2004, the tritium concentrations in DSP124 showed a steady decreasing trend in concentration from near 9,000 pCi'L in September 1994 to less then' 2,000 pCi/L in June 2003. The changes
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois in tritium concentration with time in wells DSP124 and DSP125 are presented in Figure 4-10.
There are five monitoring wells, DSP105, DSP106, DSP107, DSP108, and DSP123, installed near the Unit 1 reactor. The tritium concentrations in wells DSP105, DSPJ06, and DSP107 show a steady decrease in concentration since May 1994. Well DSP105 shows a decrease from slightly over 5,000 pCi/L in May 1994 to about 300 pCi/L in November 200.4. Well DSP106 shows a decrease from 18,000 pCi/L in May 1994 to about 3,000 pCi/L in April 2005.
Well DSP107 shows a decrease from 26,000 pCi/L in May 1994 to near 9,000 pCi/L in November 2004.
Well DSP108 shows a sharp decrease in concentration from about 50,000 pCi/L in May 1994 to less than 3,000 pCi/L in April 2005. Well DSP123 shows a very small decrease in concentration from about 25,000 pCi/L in May 1994 to slightly over 12,000 pCi/L in April 2005. No noticeable changes in tritium concentrations were observed in these wells on July 31, 2004 or shortly afterward.
The changes in tritium concentration with time in wells. DSP105, DSP106, DSP107, DSP108, and DSP123 are presented in Figure 4-11.
There are five monitoring wells located north of the Unit 2/3 intake canal.
Well DSP122 was installed near the Unit 2/3 discharge, and wells DSP148, DSP149, DSP155, and DSP156 were installed in the area bound by the Unit 2/3 discharge and the recycling canal. Well.DSP122 shows a decrease in concentration from about 13,000 pCi/L in December 1994 to slightly over 1,000 pCi/L in April 2005. Wells DSP148 and DSP156 show low levels of tritium at less than 300 pCi/L, and well DSP1 55. shows tritium concentrations of less than 1,000 pCi'L, with the exception of one value of 3,713 pCi/L on February 26, 2003. Well DSP149 shows a large fluctuations from April 1995 to February 2004, with maximum concentrations of 76,488 pCi/L in March 3, 2002 to minimum concentration of 404 pCi/L in May 24, 1999. As discussed in Section 2.1.3, the tritium concentration and the water level data from DSP149 were anomalous. As a result, the well was repaired, and subsequent sampling yielded a tritium concentration of 121 pCi/L on April 8, 2005.
Based on the concentrations In these wells, it appears the grouhidwater impact from the CST system did not affect-these wells. The changes in tritium concentration with time in wells DSP122, DSP148, DSP149, DSP155, and DSP156 are presented in Figure 4-12.
The tritium concentrations in the remaining monitoring wells installed farther away from the CST system were at low levels, usually below 200 pCi/L. Also very little variation of tritium was detected in these wells over time. The tritium concentrations in all monitoring wells outside the CST system area for September 3, 2004 and April 8, 2005 are presented in Figures 4-13a and 4-13b, respectively. The April 8,2005 data are also provided in Table 4-1. As can be seen from these figures, the groundwater impact from the CST system is confined to a small area. Outside this impacted area there is no evidence of elevated tritium concentrations associated with the CST system. A slightly elevated tritium concentration was observed in the intermediate monitoring
Final Draft Groundwater Tritium Investigation Report -Dresden Generating Station, Morris, Illinois well DSP159M located across the cooling canals approximately 3,400 feet south of the CST system. The tritium concentration in this well is discussed in Section 4.5.
4.4 Surface Water Surface water received from the Unit 2/3 intake runs through the facility outside of the reactors to control the temperature, then is discharged through the Unit 2/3 discharge flume into the hot canal.
The hot canal flows southward to Dresden Cooling Lake, where the water circulates and is returned north via the cold canal. Except during typical summer conditions, some or all of the surface water is returned to the Unit 2/3 intake canal to be recycled through the facility for cooling, and the rest is discharged to the Des Plaines River.
Tritium concentrations in the Unit 2/3 intake canal (DSP50), the cold canal (DSP34A), and the Unit 2/3 discharge canal (DSP20) for the period of May 1994 to May 2005 'are presented in Figure 4-14.
The locations of these surface water sampling points are shown in Figure 4-9. It can be seen from Figure 4-14 that there is a similar pattern with increasing trends of tritium concentrations in these three surface water samples.
The maximum concentration in DSP50 is 6,194 pCi/L on September 27, 2004; in DSP34A is 5,437 pCi/L on September 23, 2004; and in DSP20 is 5,978 pCi/L on November 1, 2004.
4.5 Off-Site Migration The groundwater tritium. plume is confined to a small area within the CST system, as discussed earlier. There is no evidence of off-site migration of tritium in groundwater from the Dresden Station, including toward the residential area to the south. Tritium concentrations in all monitoring wells south of the CST system area as well as south of the Protected Area, except for well DSP159M, had concentrations less than 200.pCifL, which is the low L
limit of detection by the labotry. Well DSP 159M is locatea -between the j¢-x#
coolinj canals and th eli, ind is most likely impacted by tritium concentrations in the coc ncanals rather than tritium migration from the station.
Theiýell, located approximately 3,400 feet south of the CST system area, ionsislntly showed tritium concentrations below 300 pCi/L until 1995, and then a more steady increase was noticeable by 1997.
Tritium concentrations ranged from 232 to 940 pCi/L between January 19 7 adApril 2005. the changes in tritium concentrations with time in e
well (D23) and the cold canal (DSP34A) are presented in 4-1l5.I It *n be seen from this figure that tritium concentrations in thelVJell and the cold canal show a similar pattern...Also, there is a stea increasing trend in tritium concentrations in e ell parallel to the increasing trend in the cold canal.
Water samples iected from the cold canal and well
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois DSPI59M located east of the canal. on April 8, 2005 measured tritium concentrations of 1,339 3d-3 Ci/L, respectively (Table 4-1). A water sample collected from th1 ellI on April 15, 2005 measured a tritium Oin ta n of 653 pCi/LO. Therei appears to be a strong correlation between thefinvwell tritium concentration and the cooling canal as groundwater flows from e cooling canals to the Kankakee River in an eastward direction.
Tritium has been detected.in groundt.....-r samples collected from onq one other residential well located east of theell along the, Kankakee v
goýundw* r sample. was colleced froff* the well a~n December 2, 2004, and the sample was split for analy~S twoindepe t laboratories. Due to the discrepancy in results (366 pCi/L vs. 114 pCi/L), another sample was collected on January 13, 2005, and four aliquots were reported ranging in concentration from 360 to 480 pCi/L. Another sample was collected on April 15, 2005, and the reported tritium concentration was 542 pCi/L.
ý11
5 Tritium Impacts Evaluation 5.1 Regional Background Tritium Levels Tritium is a naturally occurring radioisotope of hydrogen, which decays as a beta emitter (half life of 12.3 years). It is produced in small quantities in the upper atmosphere where it is readily incorporated into water, and therefore, is present in rainwater and surface recharge to aquifer systems. In comparison to many other atmospheric radioactive isotopes, tritium is extremely rare and not affected by any.chemical or biological processes. The naturally occurring tritium level in rainwater (pre-bomb era of early 1950 and before) is estimated at 5 to 10 tritium unit (TU), where one TU is equivalent to one tritium atom per 1018 hydrogen atoms and an equivalent gross beta radiation of 3.2 pCi/liter.
During the mid-1950s and early 1960s, the amount of tritium in the atmosphere was greatly increased as a result of nuclear weapons testing causing recharge waters to be "tagged" with excess tritium. Nuclear weapons testing resulted in atmospheric tritium levels in excess of 1,000 TU, with peaks occurring in 1963. However, since then, the values have declined due to the elimination of atmospheric nuclear weapons testing and radioactive decay. Present day background values in the range of 50 to 100 TU (i.e., 160 to 320 pCi/L) are common' in the environment (Michigan DEQ, 2002). For all practical purposes, the regional background tritium level in the -Dresden Station area will be considered to be equal to or less than 320 pCi/L.
5.2 Tritium Mass Release Assessment Dresden Station personnel conservatively estimated that tritiated water was released from the CST system and discharged into the ground over a period of 344 days between November 2003 and October 2004 at a rate of 1.31 gallons per minute (gpm).
The concentration of tritium in the CST system was approximately 9 to 10 million pCiIL. Based on these estimates, a total of 643,000 gallons of tritiated water, containing a total mass of approximately 2.3JIxl0'3pCi of tritium, was releas6* from the CST system.
Upon release, the tritiated water infiltrated through the unsaturated zone and into the groundWater.
Because this location was situated within a groundwater mound, the release was transported in multiple directions. In addition, the depth of the foundation beneath the turbine building and reactor units extends to a depth of greater than 40 feet below ground surface, creating a hydraulic barrier to the north for shallow groundwater flow. Also, the excavation outside the fobundation of the building and the backfill with permeable material (sand) created preferential pathways for groundwater flow around the building foundation.
The primary local groundwater flow directions from the location of the release are to the east and to the northwest.
Final Draft Groundwater Tritium Investigation Report -Dresden Generating Station, Morris, Illinois 5.2.1 Shallow Groundwater Contribution To represent the downstream transport of tritium using available monitoring data from the. shallow monitoring wells, RETEC calculated the mass flux of tritium along several planes drawn perpendicular to the tritium plume in each groundwater flow direction. Figure 5-1 indicates the approximate limits of the tritium plume and the planes along which the mass flux was calculated.
Detailed descriptions of the calculations performed in this evaluation and complete results are contained in Appendix G. The Darcy velocity was estimated using the hydraulic conductivity (K) value calculated from slug tests conducted at shallow monitoring well DSP157S and the hydraulic gradient (i) calculated from groundwater elevations measured in shallow wells in the vicinity of the CST system in April 2005:
Vd..,
= Ki = 3.29 x1 0-2 f/min x 0.014f/f
= 4.61lxl10- f/x144omin/xo.3o48m
= 0.20m/.
vdw.,.,
Ki = 3.29 x 102 -min xO 0 fl/f8
-2.83 xl10- flY.x 1440m!--/dxO0.3'048~n m in xO.O0861
= 0.12, y
Using the average tritium concentration (C) for each plane, the mass flux was calculated as follows:
Flux = CVd The mass flux observed along each plane is graphed versus time for groundwater flow to the east and west in Figures 5-2 and 5-3, respectively.
As anticipated, the graph of flux east of thQ release indicates that planes drawn, farther from the source generally show later peaks in mass flux, with peak flux values lower than planes drawn closer to the source. The distance between Plane 4 and Plane 5 divided by the time between peaks on the respective mass flux graphs for these planes gives an estimate of the travel time of the release equal to 4.7 centimeters per day (cm/day) to the east of the source area. The lack of a discemable peak in mass flux in Planes 1 through 3. likely indicates that these peaks were missed in the lag in monitoring between samples taken prior to the release and the July 2004 sample collection. Because only one monitoring plane could be drawn to represent data collected west of the release, a travel time of the release in this direction was not calculated. Note that the mass flux graph in the western direction does not show a discemable peak. It is also likely that the peak in mass flux in this direction was missed in the lag in monitoring.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois To estimate the mass discharged over the area of each plane in units of pCi per square meter, the average mass flux between sample dates was multiplied by the number of days between samples. The plume cross-sectional area was then modeled as follows: The width of the plume at the source was estimated to be approximately 20 feet based on the geometry of the source area at the release. Based on the depth of the deepest shallow monitoring well, the depths of both the eastern-moving and western-moving plumes at and near the source were estimated as 10 feet. These dimensions give a cross-sectional area of 200 square feet at the source.
Based on a typical plume geometry identified in Fetter (1999), a ratio of longitudinal dispersivity (i.e., along the plume centerline) to transverse dispersivity (i.e., outward from the plume centerline) was assumed as 10:1.
Therefore, based on an estimated plume length of 210 feet in the eastern direction, a maximum plume width was approximated as the source width plus twice the lateral dispersivity, or 62 feet. Likewise, using an estimated plume length of 255 feet in' the western flow direction, the maximum width of the plume is approximated as 70 feet. By multiplying the mass discharged per square meter by the modeled area of the plume, the total mass discharged through each plane was estimated for each sample period.
Finally, by summing the mass discharge during each sample period, the total mass of tritium discharged through each plane was approximated.
Since no monitoring plane exists at or near the source in the western direction, the source concentrations in this direction were estimated based on monitoring at Plane 10. An analytical model (BIOSCREEN) was applied to simulate a one-dimensional solute distribution using site-specific and constituent-specific information (USEPA, 1997). The modelinputs are described in more detail in Section 5.4.1. For calculation of the western source concentration, the plume length was set equal to 255 feet, as shown in Figure 5:1. The tritium source was modeled as a continuous source for a period of one year. The source concentration was then adjusted iteratively until the concentration at the end of the plume, approximated the value of 55,000 pCi/L based' on the concentration detected at well DSP-124 onJuly 31, 2004. The resulting western-source concentration is estimated at 200,000 pQi/L during the release.
Using the degradation rate *of concentrations detected at DSP-124, a degradation rate was applied to the western source concentration for each sample date to approximate a total mass discharged to the west through the theoretical plane drawn at the source location.
Based on the modeled planes nearest the source, approximately 4.18x10 12 pCi has been discharged tb groundwater flow east of the release.and 1.81x101' pCi has been discharged to groundwater flow west of the release, for a total. mass of4.36x1012 pCi dischargedto groundwater. Basedon atritium concentration in the CST system of 9 to 10 million pCi/L, as estimated by Dresden Station personnel, this mass equates to approximately 121,000 gallons of tritiated water released to groundwater.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois 5.2.2 Storm Sewer Contribution A portion of the Dresden Station storm sewer lies within the identified area of the tritium plume. Groundwater measured in shallow wells in the vicinity of the CST system is approximately 2 feet higher in elevation than measured invert elevations along the plant storm sewers (assumed to be 18 inches in diameter).
Analysis of samples collected from storm sewer catch basins within the. identified tritium plume (DSP134 and DSP135) and at the outlets of storm sewers draining east to the Unit 1 intake canal (DSP132) and west toward the Unit 2/3 discharge canal (DSP131), indicate significant increases in tritium concentrations following the estimated time of release from the CST system. These observations indicate that a portion of the tritium released to groundwater is infiltrating into the storm sewers flowing in each direction and discharging to the respective storm sewer outlets into the Unit 1 intake canal and Unit 2/3 discharge canal. Tritium discharged to the Unit I intake canal lies stagnant in the non-operational intake, while that discharged to the Unit 2/3 discharge canal flows through the hot canal to Dresden Cooling Lake prior to return flow through the cold canal, and out to the Des Plaines River or back into theUnit 2/3 intake.
Daily precipitation data from the Dresden Island Weather Station, obtained from accuweather.com, was used to estimate an average daily rate of runoff over the east-draining and west-draining storm sewer drainage areas. Since
_the majority of the drainage area for the storm sewers is covered in impervious material (e.g., asphalt or rooftops), it was assumed that 85% of the precipitation flows to the sewers as runoff. The volume of daily runoff was therefore calculated as 85% of the precipitation depth multiplied by the drainage basin area-for each daily precipitation depth.
A base flow rate, due to groundwater ingress into the storm sewers, was also estimated for each sewer. It was assumed that approximately 10% of the sewer pipe'surface area was cracked, allowing groundwater ingress through the'cracks. Assuming that groundWater ingress occurs over approximately one-half the surface area of the pipe, the area subject to ingress Was estimated by multiplying the pipe circumference ftimes the length times 0.5.
The groundwater seepage velocity was estimated in each direction using the hydraulic conductivity value and hydraulic gradient values identified above, with an assumed effective porosity of sandstone equal to 15% based on a typical value stAted in USEPA (1989).
Ki 3.29X 10-2 f//min xO.014flyf
-n 0.15
= 3.0734x0 x144 0m/x0.3048%
Final Draft Groundwater Tritium investigation Report - Dresden Generating Station, Morris, Illinois v.Ki 3,29x10- 2 f//minx 0.0086/ftf' n
0.15
= 1.89 x 10-' fi/x1440m'n a xO.3048 mt
= 0.83 71day The base ingress flow for each storm sewer was then estimated as the ingress area times 10% (cracked percentage of pipe) times the seepage velocity calculated as discussed above.
Based on addition of the estimated runbff and base flows, a daily storm sewer flow was estimated for each sewer. Daily tritium concentrations in the outlet catch basins were estimated based on a linear interpolation between sampling dates. By multiplying the daily tritium concentration in the outlet catch basin by the estimated daily flow rate, the daily mass of tritium discharged through each outlet was estimated. Summing these results since the estimated start of the release indicate that a total of 5.27x10 12 pCi has been discharged to the Unit 1 intake canal and 7.33x10 10 pCi has been discharged to the Unit 2/3 discharge canal, for a total mass of tritium discharged through the plant storm sewers of approximately 5.34xl 012 pCi. Based on an estimated tritium source concentration of 9 to 10 million pCi/L by Dresden Station personnel, this mass equates to approximately 148,000 gallons of tritiated water released to the storm sewer.
5.2.3 Net Release of Tritium Mass The.net release of tritium mass was evaluated from the analyses of discharge to groundwater and storm sewers as follows. Since the mass discharged to groundwater in, the western direction greatly exceeds the mass discharged to the western storm sewer, and the western storm sewer lies downgradient of the release, it is assumed that the mass observed in the western sewer represents a portion of the mass observed in groundwater. In the eastern direction, however, the estimated source'mass discharged to.stormwater exceeds the mass discharged to groundwater at the monitoring point nearest the source (ie., Plane 1 in Figure 5-1).
Since the eastern storm sewer originates immediately within the source area and follows near the plume centerline, it appears that much of the source mass may be discharging to the storm sewer upgra ient of Plane 1. Therefore, the total mass discharged in the eastern direction 'is estimated by adding the contribution observed in groundwater at Plane 1 to the estimated mass discharged to the eastern storm sewer.
Based on these analyses, the net tritium mass discharged to the groundwater and to the storm sewer from the CST system is approximated by adding the mass discharged to the western flowing groundwater (i.e., mass at the theoretical source. plane), the mass discharged to the eastern flowing
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois groundwater (i.e., mass at Plane 1), and the mass -discharged to the eastern storm sewer (i.e., through DSP132). This provides a net tritium mass of 9.63x1012 pCi released to the groundwater and storm sewer system in the vicinity of the liquid nitrogen tank. Based on an estimated tritium source concentration of 9 to 10 million pCiIL by Dresden Station personnel, this total mass represents approximately 267,000 gallons of tritiated water released from the CST system, which is 42% of the volume estimated originally by the Dresden Station personnel.
5.3 Rate of Tritium Release Based on the analysis presented in the previous section and a total mass of tritium released over the duration of the discharge from the CST system (i.e.,
344 days between November 2003 and October 2004 based on communication with Dresden Station personnel), the net rate of tritium released to the Dresden Station groundwater and sewer systems amounts to 2.80x10' pCi per day.
5.4 Potential Impacts to Groundwater 5.4.1 Shallow Groundwater RETEC developed a conceptual model of fate and transport of tritium in the above-described groundwater plumes for the purposes of identifying the approximate length, of time reqcuired for groundwater to deplete tritium concentrations at the source of the release. The solute transport modeling effort employed an analytical solution, developed by Domenico (1987), as the governing equation for transport ofa decaying solute. The analytical model (BIOSCREEN) simulated a one-dimensional solute distribution using site-specific and constituent-specific information developed in the conceptual model (USEPA, 1997).
The source area defined in the conceptual model was the area surrounding the approximated location of the release. The estimated maximum plume length in each flowdirection (i.e., east toward the Unit 1 intake canal and west toward the hot canal) was based on the maxim~um distance the tritium would travel in groundwater prior to entering plant canals. The source thickness was estimated at 10 feet saturated thickness, based on the shallowdepth of the pipe where release occurred (approximately 3 to 5 feet below ground surface).
The concentration of tritium at the source was modeled as a finite soluble mass, with a distinct source mass assigned to each direction of flow. The source mass contributing to the. plume moving west from the source was estimated by subtracting the total tritium mass discharged through the storm sewer to DSPl31 from the total mass discharged to groundwater in the western flow direction. It was assumed that preferential flow through the sewer reduces the mass in the plume downgradient of the point at which the total mass discharged to groundwater was evaluated (i.e., at the theoretical
Final Draft Groundwater Tritium Investigation Report-DresdenGenerating Station, Morris Illinois source plane). The source mass discharging east of the liquid nitrogen tank was taken as the total mass discharging to the groundwater. The calculated mass discharging to stormwater in the eastern direction exceeds the mass discharging to groundwater, indicating that (1) tritium enters the storm sewer upgradient of the monitoring points evaluated. for discharge to groundwater (i.e., Plane 1), and/or (2) limited data during the early period of the release may miss the peak in tritium concentrations nearest the source, resulting in an underestimation of the mass discharged to groundwater.
Dissolved tritium migrates in the direction of groundwater flow through the process of advection, dispersion, and degradation. Advective transport is controlled by the direction and magnitude of the groundwater seepage velocity. Groundwater seepage velocity was calculated using site-specific values for hydraulic conductivity and hydraulic gradient, and an assumed value for effective porosity based on the sandstone aquifer. The hydraulic conductivity was taken as the value calculated from the slug test conducted at shallow monitoring well DSP157S, which is similar in lithology to the area of the CST. The average hydraulic gradient was estimated from water table contour maps developed from measurements of groundwater elevation during the sampling event conducted on April 8, 2005, The effective porosity was derived as the typical value for nonfractured rocks such as sandstone (USEPA, 1989). These parameters provideý an estimate of uniform seepage velocity for the shallow aquifer.
The amount of dispersion is a function of the dissolved-phase plume size. The longitudinal dispersivity was modeled as a. function of plume length using methods given by Xu and Eckstein (1995). The transverse dispersivity was taken as 10% of the longitudinal dispersivity (Gelhar et al., 1992).
The vertical dispersivity. was taken as 10% of the transverse dispersivity (ASTM, 1995).
These relationships represent the low-end of typical dispersivity values presented in literature.
Degradation of tritium occurs through radioactive decay, Degradation of tritium was modeled as a first order decayreaction.. The rate of-degradation is described by the time it takes for the initial constituent mass to decay and is commonly referred to as the half-life (th). The half-life value for tritium used in the modeling was based on a value of 12.3 years (Michigan DEQ, 2002).
Attenuation factors were established for each compound Within BIOSCREEN based on the input parameters described above and listed in Table 5-1. After inputting these parameters, the simulation time was varied to identify the time after which concentrations of tritium in the plume.were reduced to levels below background (typically 160 to 320 pCi/L).
Based on the results of the modeling, concentrations of tritium at the source and along the western plume (toward the hot canal) will decrease to below 90 pCiIL after approximately 5 years from the pipe repair.
Similarly, the concentrations at the source and along the eastern plume will drop below 290
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois pCi/L after approximately 8 years. Results for.these time periods appear to be conservative based on a comparison of current monitoring data with the 1-year predictions from the BIOSCREEN modeling.
5.4.2 Residential Wells Based on the analysis of the site hydrogeology, it is most likely that the bulk of the tritium discharge to groundwater is flowing in the easterly and northwesterly directions under the influence of the local hydraulic gradient.
The relatively high seepage velocity calculated in shallow groundwater indicates that movement of the plume will likely continue to follow the local hydraulic gradient in each direction, flowing east alongside plant building foundations and northeasterly toward the Unit 1 intake canal, and flowing west alongside plant building foundations and northwesterly toward the hot canal. Because of this preferential flow path, the tritium plume is not likely to come under the influence of the regional gradient in the southeasterly direction, which is the only way groundwater impacted by tritium from the CST system could impact the residential wells south of Dresden Station.
6 Summary Routine groundwater sampling results undertaken in July 2004 detected elevated levels of tritium in shallow monitoring wells and storm sewers located near the Unit 2/3 interlock building. The tritium originated from a release in the CST system through a pipe that passed under a liquid nitrogen tank. The pipe was shut down on October 20, 2004 and a replacement section of pipe around the tank was installed the following month. RETEC was contracted by Exelon to characterize the nature of groundwater flow at the facility and evaluate the fate of the tritium.
The following paragraphs summarize the results of this investigation:
The groundwater flow direction in the immediate vicinity of the liquid nitrogen tank is to the east and to the northwest. In the eastern half of the Protected Area, groundwater.flows to the north toward the Unit 1 intake canal.
West of the CST system groundwater flows westward toward the cooling canals. South of the Protected Area, groundwater flows to the southeast and southwest with a groundwater divide oriented northwest-southeast from well DSP124 to DSP152. Further south of the Protected-Area in the residential area, groundwater flows from the cooling canals eastward to the Kankakee River.
f The horizontal hydraulic gradient values in the vicinity of the CST system calculated from the water table contour maps were 0.022 and 0.014 ft/ft to the northeast on October 28, 2004 and April 4, 2005, respectively.
The average horizontal hydraulic gradient outside of the Protected Area ranges from 0.0046 ft/ft toward the southwest to 0.035 ft/ft toward the northeast.
0 Portions of the building are constructed.directly. on top of the Maquoketa Shale; therefore, groundwater flow.in the water table aquifer is affected throughout its entire thickness around the facility. The hydraulic gradient shows groundwater flows toward.
the building with preferential lateral flow around the building to the east and west. This also can create a groundwater mounding effect around the building.
e Dresden Station is surrounded by surface water bodies that have a significant effect on groundwater flow.
The vertical gradient calculated at well DSP157, which is closest to the Protected Area, was 0.0032 ft/ft with an upward component..
The vertical gradients calculated at wells DSPI58 and DSP159 were 0.017 and 0.0044 ft/ft, respectively, with downward components.
Final Draft Groundwater Tritium Investigation Report -Dresden Generating Station, Morris, Illinois
" The geometric mean of hydraulic conductivity values calculated for the shallow wells were two orders of magnitude greater than the geometric mean for the intermediate wells installed just above the shale. The geometric mean of hydraulic conductivity for the shallow wells is 2.4x1(" 2 ft/min (34.2 fl/day), and the geometric mean of hydraulic conductivity for the intermediate wells is 4.7x10"4 ft/min (0.67 ft/day).
A records search was performed to correlate residential water wells to the ISGS well r however,, noeof eco o corresponded, to th ý
ývell located aý The welle erostidentl well located a The residential wells were typically cased to 40 feet below ground surface and completed at depths of 200 feet or more, A -well identified as ISGS Record #22798 had a casing set at 58 feet below ground surface. Since all of the wells, except ISGS Record
- 22798, had casings set at 40 feet below ground surface and-the depth to shale was consistently 60 feet below ground surface, these wells are partially pumping water from the upper aquifer as water flows down the open hole beneath the casing outside of the pump.
- The tritium-impacted groundwater is migrating east as evident from the decrease in tritium in wells W3 and T6, and a consequential increase in well T1. -It is likely that the tritium is also migrating west as indicated by the sudden increase in the concentration in well DSP124 located northwest of the CST system.
- There.appear to.be two active sewer systems located in the vicinity of the CST system. One sewer originates immediately to the east of the liquid nitrogen 'tank and drains the, area around the southeastern -ald northeastern perimeter of the turbine building.
This sewer discharges to the Unit I intake canal through storm sewer DSPI32. The second sewer originates immediately to the west of the liquid nitrogen tank and'drains the area around the western perimeter of the turbine-building. This sewer drains to the Unit 2/3 discharge canal through an outfall located in the west side of the canal.
Tritium appears to have migrated mostly into the eastern sewer system and to a lesser extent into the western sewer system. It appears that the source of tritium in the eastern sewer system is from the CST system, as the catch basins immediately east of the liquid. nitrogen tank have resulted in the highest tritium concentrations.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois
- Tritium concentrations in the monitoring wells installed farther away from the CST system were at low levels, usually below 200 pCi/L, with very little variation over time.
The groundwater impact from the CST system is confined to a small area. Outside this area there is no evidence of elevated tritium concentrations associated with the CST system.
" Tritium concentrations in the Unit 2/3 intake canal (DSP50), the cold canal (DSP34A), and the Unit 2/3 discharge canal (DSP20) for the period of May 1994 to May 2005 show that there is a' similar pattern. with increasing trends of tritium concentrations in these three surface water samples.
" Based on the distribution of tritium in groundwater and the geometry of the release area, the width of the plume at the source was estimated to be approximately 20 feet. The depths of both the eastem-moving and western-moving plumes at and near the source were estimated as 10 feet. The plume length was estimated as 210 feet in the eastern direction with a maximum plume width of approximately 62 feet. Likewise, the plume length was estimated as 255 feet in the western flow direction with a maximum width of approximated as 70 feet.
" The total mass of tritium discharged to groundwater flow east of the release was calculated as 4.18x1012 pCi, and the total mass of tritium discharged to groundwater flow west of the release was calculated as 1.81xl0 pCi. Based on a tritium concentration in the CST system. of 9 to 10 million pCi/L, this mass equates to approximately 121,000 gallons of tritiated water released to groundwater.
" The total mass of tritium discharged to the eastern storm sewer sysiem, which outlets into the Unit 1 intake canal, was calculated i as 5.27x1012 pCi. The total maiss of tritium discharged to the' western storm sewer system, which outlets into the.Unit 2/3 discharge canal, was calculated as 7.33xI010 pCi. Based on an estimated tritium concentration in the CST system of 9 to 10 million pCiIL, this
'ass equates to approximately 148,000 gallons of tritiated water released to the storm sewer.
e The net tritium mass discharged to the groundwater and to the storm sewerfrom the CST system is calculated as 9.63x10' pCi.
Based on an estimated tritium concentration in the CST system of 9 to 10 million pCi/L, this total mass represents approximately 267,000 gallons of tritiated water released from the CST system.
The net rate of tritium released to the Dresden Station groundwater and sewer systems, assuming that the total mass of tritium was
- Z--,
4 Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois released over the duration of the discharge from the CST system (i.e., 344 days between November 2003 and October 2004),
amounts to 2.80x,01 ° pCi per day.
Based on fate and transport computer modeling (BIOSCREEN),
the concentrations of tritium at the source and along the western plume will decrease to below 90 pCi/L after approximately 5 years from the pipe repair. Similarly, the concentrations at the source and along the eastern plume will drop below 290 pCi/L after approximately 8 years.
The investigation concluded it is most likely that the. bulk of the tritium discharge to groundwater is flowing in the easterly and northwesterly directions under the influence of the local hydraulic gradient. Movement of the plume will likely continue to follow the local hydraulic gradient in each direction. Because of this preferential flow path, the tritium plume is not likely to come under the influence of the regional gradient in the southeasterly direction, which is the only way tritium-impacted groundwater from the CST system could impact the residential -wells south of Dresden Station.
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Bouwer, H. and R. C. Rice,. 1976.
A Slug Test for Determining Hydraulic Conductivity of Unconfined Aquifers with Completely or Partially Penetrating Wells, Water Resources Research, Vol. 12, pp. 423-428.
Domenico, P.A., 1987. An Analytical Model for Multidimensional Transport of a Decaying Contaminant Species, Journal of Hydrology, v. 91, pp 59-58.
Fetter, C.W., 1994. Applied Hydrogeology Third Edition, p. 91.
Freeze, R. A., and Cherry, J. A., 1979. Groundwater, Englewood Cliffs, NJ, 604 pp.
Gelhar,'L.W., C. Welty, and K.R. Rehfeldt, 1992. A Critical Review of Data on Field-Scale Dispersion in Aquifers. Water Resources Research, Vol. 28, No.
7, pg 1955-1974.
Harza Engineering Company (Harza).
1991.
Dresden Station Site Groundwater Study, July.
Harza Environmental Services, Inc. (Harza).
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Dresden Groundwater Study Report, Morris, Illinois, January..
HydroSolve,. Inc., 2000. AQTESOLV for Windows 95/98/NT, Version 3.01 -
Professional.
"Use of Tritium in Assessing Aquifer Vulnerability."
Michigangov.<<http://www.deq.state.mi.us/documents/deq-dwrpd-gws-wpu-Tritium.pdfP> dated January 2002, accessed on June 16, 2005, 4:00 PM EST.
Newell, C*J, R.K. McLeod, J.R. Gonzales, and J.T. Wilson, 1996.
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Natural Attenuation Decision Support System," Users Manual, Version 13.
and 1.4, Nafional Risk Management Research Laboratory, Office of Research
'and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio.
USEPA, 1989. Statistical Analysis of Groundwater Monitoring at RCRA Facilities, U.S. Environmental Protection Agency, Washington, D.C.
USEPA, 1997. BIOSCREEN, Natural Attenuation Decision Support System, User's Manual, Version 1.3 and Version 1.4 Revisions, United States Environmental Protection Agency, Office of Research and Development, EPA/600/R-96/087, August 1996 and Version 1.4 Revisions, July.
Willman, H. B., 1971. Summary of the Geology of the Chicago Area, Circular 460, Illinois State Geological Survey, Urbana, Illinois.
Final Draft Groundwater Tritium Investigation Report - Dresden Generating Station, Morris, Illinois Xu, M, and Y. Eckstein, 1995. Use of Weighted Least-Squares Method in Evaluation of the Relationship Between Dispersivity and Scale, Ground Water, V. 33, No. 6, pp. 905-908.