|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 66
5
Inventory Technical Element
As noted in Chapter 3, the Integration Project's Inventory
Technical Element supports studies to develop estimates of chemical and
radionuclide inventories' at the Hanford Site. The radionuclide inventory
includes any radioactive material imported to or produced at Hanford with
a half-life greater than 5 years and activity in excess of 1 curie. The
chemical inventory includes chemicals imported, manufactured, or
produced at Hanford and other chemicals identified in the monitoring or
characterization programs. The "other' category includes new chemicals
produced, for example, through biological degradation of existing
chemicals in the environment.
There are more than a dozen databases maintained by the
Hanford Site and a large number of Hanford Site documents that contain
chemical and radionuclide inventory information. The primary inventory-
related databases include the following:
The Waste Inventory Data System (WIDS) contains
information on more than 2,500 potential waste sites at Hanford. The
database tracks descriptions of the sites, their locations, and sampling or
testing information.
.
The Solid Waste Inventory Tracking System (SWITS) tracks
inventories on radioactive and nonradioactive solid waste generated on-
site and imported from off-site facilities.
.
The Hanford Environmental Information System (HEIS)
contains Hanford Site environmental sample data, including data from
groundwater, waste sites, and soils.
· The Tank Characterization Database (TCD) contains tank
waste analytical data, historical data, and surveillance data.
The Track Radioactive Component (TRAC) database
contains modeled estimates of tank waste radionuclide inventories. A
more recently developed database, the Hanford Defined Wastes (HDW),
performs a similar function.
Most of the inventory of chemicals and radionuclides at the
Hanford Site now exists in facilities constructed on or in the vadose
As noted in Chapter 4, the term inventory is used by the Integration Project
to describe the quantities of radionuclides and chemicals that have been placed in
storage and disposal facilities at the Hanford Site.
66
OCR for page 67
Inventory Technical Element
67
zone in particular, the underground high-level waste tanks and waste
ponds, pits, trenches, and cribs (see Chapter 2~. Some of this inventory
has migrated from these facilities into the vadose zone and g~roundwater.
The need for characterization of these contaminant releases in the
vadose zone has been emphasized repeatedly in previous studies. For
example, an earlier National Research Council (NRC) report stated that
"an important component of a long-term commitment to remediating the
single-shell tanks at the Hanford Site is an adequate understanding of the
... extent to which the soil and ground water beneath the tank farms have
been contaminated. Characterization should continue until such an
understanding has been obtained" (NRC, 1996, p. 28~. A 1996
Department of Energy (DOE) review noted that "characterization of the
vadose zone is an essential step toward understanding contamination of
the groundwater, assessing the resulting health risks, and defining the
concomitant groundwater monitoring program necessary to verify the risk
assessments" (DOE, 1 997b, p. Pap.
Under current plans for the Hanford Site, the majority of the
current waste inventory in burial grounds and liquid disposal sites will be
left in place (see discussion of the Cleanup of the Hanford Site in Chapter
2), as will past contaminant releases to the vadose zone and
groundwater. Additionally, removal of waste from high-level tanks may
result in further releases of contaminants to the subsurface (see NRC,
1996, p. 36-37~. The estimation of long-term environmental impacts from
the inventories and contaminant releases to be led in the ground requires
an accurate knowledge of the amount of each contaminant in the soil (the
source term), its chemical form (speciation, see Sidebar 5.1), and the rate
at which each migrates through the subsurface, either in solution or in
colloidal form (Sidebar 5.2~. Assessment of source terms and migration
rates, in turn, requires detailed characterization of the distribution of
contamination in the environment as well as subsurface properties that
control contaminant fate and transport. Since the Integration Project's
science and technology (S&T) program mission is to aid in providing the
data required for site decisions (see Chapter 3), characterization of the
site must be one of its primary focuses.
The following are examples of decisions that will require some
knowledge of waste inventories as well as past and possible future
contaminant releases at the site:
1. Disposition of existing waste sites in the 200 Area (e.g.
disposal cribs and canyons). Should such facilities be left in place
2The committee uses the term contaminant release to describe waste that
has migrated out of disposal facilities and into the environment.
OCR for page 68
OCR for page 70
OCR for page 71
OCR for page 72
OCR for page 73
OCR for page 74
OCR for page 75
OCR for page 76
OCR for page 77
OCR for page 78
Representative terms from entire chapter:
hanford site
68
Science and Technology for Environmental Cleanup
ion.~o,r,'m.,QI' ~ :i ~:'~s's~' 'A ' ''~'t It ' ''''at'n'f'''l-'Q'~:~'''-"':'
. ~th.e.,t.m,n,sfer,o,,.f.eleckon. Sj~Xld~lOD ~~du~ion3-,--h
. o.f,.~.hem,~~al .comple~s been- Dissolved -con man cations and: .~; .
., neutm,,i.:~.o,,negabv.,e.ly~.h-a.~ d.~compl~ing--
-deso:~'on mact'cn$ at solid $olut' ~intp~e ~ ~-pre£~p~tat~-: : - ; it-- - ;
..~is,.'s.,o.l.u.tio.n.,:~a,n,0.- ' i' I ' ' i ~'l' - ' '
, .,,. :, :~~: .£,,,hem,-~cal ~~nto~ d~ rei~y.~n I -de--*n~rm~~ -n, ~ . . ;,--.;. ::: . -;
. spec.~at~ .o.n -.: :~t~ -th.e. .chem~=,,l, .~,= .:o.f a.n~:lem.,,.ent.: o.hen, .hasa. oro~un~d .
b r ~ D m b b) nd tox city. Some
im nv n b mist :sotiai7i,
~Iy n on c h~m (a' N~ ) n ys
env'tonments. - However ~ -many of--the~ "~tam- an9; of =~rn:
nfoniexhib cOmpexspe£iaiOn an i is he en al
~behavior of these sDecies~that must~be~£onsidered::=at~on~
~ .~.~ ~.~:' M:an.'y of'~e ' 'n ' i ' ~'' t''H ' ' ~''' ' "" 1 ' ' ' ~i' ' ' "' ' '' ' ' :1' ~.' ' :"'::"
ea or~transit~onmetais.Onep pe of eistii~iig liithat
istinguishes~emf~mothercontami:,n,ants~is~fliipitDii;~eanex'stin
nult!pJe oxidat~on: states ttia,t are in thl3rmQdynamic equilibr~um and
~ :. ~!.~:~'C'.'"':-,~t'f ~
~ :~ ~ :~e--~ll In ~oe amOlesam-- sk £ti ::O (~1) ah'ahIv:~- . ~
Q.x~.Ized to=. J Gh .~.m~u~, is.g, ~ i .m- ~ en;iG d £a~ino --nic, -
a,nd it-,ten,ds,,to, b,e mob-ire :in ground ~r du ~ Rs tenden '' ~ ~rm: '''
,so,l,u41,,e,,,~,,,c,,,,,,o,,,,m,,p,l,e,,,,,x,,,,,e,,,s,,~,~, ,C,,r,(~l,13, a lesg-~q
en,~m,e, a,~i,v,itie,s~a d:i Ie obil#~-i- ':-' ' ' ~t' '.;;'Th'' ,''the a ' "
=~ ~ chn~miurn in the e~nrnt~nt;~¢hal~ only~ b ~ ~ ~ ~
chrom~ium.~..:~Can~.ex~st- in.~-a va~rietv..~t.03
Inventory Technical Element
Ill ~-~ ~~ ~~-~ -if Blithe ~charactenst~cs or :er,vironm~e-ntal sys:te-ms~-that govern --if
scheming ~speciation: can:- in time and- space, i PI fl
large spatial:an-~temporal~calsse o i s:s has ~-
H~an~r6. Un&erstan:ding the processes and ~ ditto s: h I -----
~ ~ . ~ ~~ . . ~ . ~ ~ ~ .~ ~ ~ . I I :.~ . .. ~ - ~ -
speciation-~trans~-= : all i ti t ~ -b ~ p dim--- ~
.conta~m~i~n.a-nt. ,behav~or.,~ver. the wide.. range: of .en.viro:nmentai c.ondlt~l:ons~ .
fh~,nd-~t'. Hanf2 r ' . with imOro"''"e'd. co '2 ' ' 'I o ibid ' ' ~
69
.............
. ~ ~
.. -
,.
.. -.....
:-~
. ~ .
-only Of'-~.Iement mass.~onGentratio~ns.
essentially as is, or should additional steps be taken to reduce the
potential for future contaminant migration?
2. Retrieval of residual nonliquid wastes from single-shell tanks.
Would such retrieval result in substantial aclditional releases of
contaminants to the subsurface, and would these releases pose a threat
to the Columbia River or to other planned uses of the site?
3. Disposition of tank farms. If some residual waste is left in the
tanks, will it pose a hazard to the river or other receptors? If so, what
actions should be taken to minimize such hazards? For example, what
benefits would be provided by surface barriers or other methods of
infiltration reduction over the tank farms? When and where should such
barriers be emplaced?
DOE has recognized the significance of the lack of
characterization in the statement of needs for the Groundwater/ Vadose
Zone Project: "Currently, information on contaminant distribution, physical
association, and chemical form in the vaclose zone ... is not adequate to
forecast whether future breakthrough to groundwater will occur' (DOE,
2000a, p. Beg. DOE has also recognized the need for better
characterization data: "This data set is needed as input to the [System
Assessment Capability] SAC [to] allow the assessment of the cumulative
effects of Hanford Site operations and remediation on the Columbia River
and associated river-supported activities" (DOE, 2000a, p. B-74~.
There is a substantial amount of characterization work now under
way at Hanford, much of which is being conducted by the core projects
(see Chapter 3~. Existing dry wells4 are being utilized for gamma-ray
3Especially solid waste attached to the sides and bottoms of the tanks that
presumably will be removed by sluicing or other mechanical actions, which could
damage the tanks (see Chapter 2).
4As noted in Chapter 2, wells completed in the vadose zone above the water
table.
70
Science and Technology for Environmenfal Cleanup
. :S:I.DE"R 5.2 ~Do Co~llo.ids.Tr2a:'n.s'~:~.:-C2anta" '''i-' ' " t' ' ''' ' ""''-".~'- ~'- '': ''"'
olloics are collections o s ~ :pa Icles ha e~as e from
~appro' irriately ~ nanome~i.ia~m~cmme~to~ meters).
Collaidsinclude mine i 1 ; : 9
compoun:dsorminem' adi I ~ i 9 1 ii : i s:anp--
~-ba~er~a and::o~anicmacromolecule~s.~C 1! i~
transport Insoluble and there re otherw se lar el
immobile= p : lloid ir e proposeC~ to9 aYe
n~u ub~ 9~Dt ~ e n ~e t~nspoi~; K O tjetejr~
'
:
:.~
'.,,..,~:..:,.:....,.,; A.lth' ' ' ''''iti ':' 1' '''' :'' i ~' l ' th
co.,,.~.l'.o..i.ds.,hav.e t.he..po.t'.'.'nt' ' 1;' ;:'' ' :"' ' ' ' ' 1'' i' t ' ' e' ' 'hro' gh- ~
. ~ saturated ~m~edia-:- there~. liave been. no. aenera.ll~f. ~3~e.ntec] ra~nnit-~. r~.~.-.
t it-taciliae con amn nfie siu ions.ln e
| recent studies su~ppQrt the ~e: nli~t eF:f~cf:~of~colloi :lal
. omcesses m~av.~: ~n~ some~.nstances. b.e. t-o...retard...rather ~a~n~ ~er~.h~a.nce~ ~ -
tne ~anspp1~pt~ stn~ngly riorbed: contaminants~like ces~um bent alh the
~:. pmo. u-.ceD .cQllo..l.dal. ,m, a,ter,lals:. ..n',.e,,.a,,~:: ,t ,h,e .::Ie, a..d, ing:~
..: ~-a.n :et al.,'.:.2:040~.::Rap.id..£ol.1'oid g:en'er~ion'.~.:2a' ' " ' ' ' '' " t '
~ ~ ~ . ~ ~ ~ ~ ~ . . ~ ~ . ~ ~ . . . . . . ~ . - .. . . - .. j ~
- .RIu,gg.in-g;;a~n.,,d pe.,r,.'',m..,,' ' "flit' ' ' ' i' ' ' ' ' ' ' ~ ' t'~' ' ':' ':' ' 'i '- '
. ~ntamina.nt.-tr,ans,p,~. 01h st di ~ ~. pl ~ ~d
, mech.a,n,,:'s,m. s,,that ,c,,an,. e,,xpla~n,. .,a,t-l a t in; ad, th une~ ~dly de- p.;:
mI.gmt~pn:of,ce.s~um.~hr..o.ughHanfo~..:~.sedimenw- ~o tin- kin;g-: :~....,.~.~.
: ~.=llo~i.ds~ (.Ca,rr.Ql1 et, a' '' 9:' O' 1 '"T ' ' ''' ' d.' ' .' ' ' ' '' ' ' '. h'i ' ' ' ' ' ~ ' ' ~ '~
=, n.,=.n.t~,.,tia,ns an:~- -~'ghl.y alk,,,a,l'~e cond~t~ons-;~n s~mulated - - tes ; ~-
,. -gr. .e..a..lly.'.~.~b-~te,4.;the, sorpt~on of :~'um ont $ed~me.nts-.-. kee~D~-~ - ~ ~
- ~,,s,,i,,~,m,,::,i,n,,,:~ 6°:!~t l~,n,,,:.,.a,,,,n..,d.., :~D,£, ~, a,,$, ~ng.~..~ts mob~l-' y.
.~:... - ~ .:.- .. .~ EqVj - - - :,~
:su,ppo.~d s,t,udy also.~-ound that, i - ula~d high pH ste 'm:mobi:li~d ~ '
..na,,t,iv,e,..,.=iloids :in:ya.:n,~.,r.d. sed.'ments ~ nt ~ (F!u t -al.,- 2Q00; :: -: .
- ProJ.ed.t, -, Num'b,er :7.Q.1..3. .~. -in ,9 E' ' '2 ' ;,';' ' ' I' '' ' ' ' :,''
. ~..ut~o, ~ of the.w,aste' ,how,,ever,: caus.~, an:"~m di~ -
~llo~ds from the sed~men.ts; ~,though coil
nHanfordgro~undwaterdu~r~ng at~ ~|e~t D~e'Qgation
; :p~Je0..--~.podede,'le,~e..,.d, lev..e,ls~'' I' i' -' '' ~ ' i 1'1 i i ~:
;g~u'ndw.a, te, .r. f~m,,.'' '~,',.11.-~2.9,9.-W,~ '1"5" ';~'
- Fa.~), el,evated,.l~.els:.of-u,m,:n,iu ::' i - ' ' ':' '' fit ' d'' ' ' ' ' d ' t ' ' ' I '~
~,p,m, w.e,l,1:..699-.S6..-...E,.AA~,in,..the 3QO:'M' ''i'; ' ;~.
Inventory Technical Element
71
: ana 3:~64 cridy, and-eie I I t ti i fi'lt'
~~ ~ ~ ~ ~ ~ ~ - ~ ~ , --I- - -I ~ ~ - -I - ~ - - it- -: ~ ~ ~ :- ~ ~ ~ - ~~
-..:samples~..from.~11.399-.3-..~..1..~.in-~ -3~--~ (Hangman t-a1 :2000~.-
9enerated atlas= ~ ~ ~ ~ ~ ~ du to comfort .
'§:.not--:d'~e.r'mined:'d-u'~i:2n'' "'' ' ti' :' '' "' 'i' i"' ' '"' ' ' ' i' ''' ' ' '
'-:'~'1
' pluton:'um.::in. Ha,'n~.~:'.groundw."a.'.t'e,'.~.' ' ~'d' ' ' ' ' ' ' d - ': part ' f -''
·.''EM,,SP,',-.'s-.upp'o'"''2"2'' ;' ' ' i' 'a' i' '' ~ 'a" ' ' ''' ''
.~:DOE'.-2000a Tabte2-.~ -.p 2--9~.Thiss~d ~~ h. dthat--1 ss~-th 6e~ ~~-
, . . , , .. .. . . ~ . ..... ~ i
pe~nt ~ :plu.toni.~.m:was.-:bou.~.~t 2 ' 11 id ''''i
':A,re'a.2 ;~.'.,'.el.Is.' :~(Bu.'e : I i
-st2ud~ie's ~'gmuRd~'a~:.in'.the" ' '' 0 :' ' 'e': ' ' ' ' ' :0'0::' a' t.~ '-i ' ' O01'' '' ~-.~:
-'I . --It.:is-:'mp0'ant.-t i ~ h t i
. . . . ~ . .. . . ~ ~ .. .... ~ i. .. . .. ~ i.
-cotIo~ids that were general d ~ - i i i Hula ta li i
i' with-. native,,,H,an~f.o.,,~:. '' i ' i li
inadvertent era l pi iitz tied w ii the inks may differ with
respect to tr.ibspoh bebi~vror. S&T4si ipp~rted research on the role OF
colloids in contaminant ton ~
slulcinoooeration;s Ii o I t ill
- and release coil id 1
--~and the's tons Crouch the su-bsu~ce mav~b-e-~a-tshlle tome ~r
logging; push-in tools are being used for characterization at shallow
levels; laboratory studies have been conducted on the chemistry of
contaminants under specific conditions; and there is an ongoing effort to
acquire additional characterization data by drilling new boreholes in the
tank farms, as well as by geophysical logging of existing tank farm
boreholes (DOE, 1 999b). This work has provided a wealth of valuable
information, which is to be compiled in field reports on individual tank
farms. However, none of these planned tank farm field reports had been
issued by DOE or its contractors by the time this report was being
finalized for review in May 2001.
SCOPE OF INVENTORY TECHNICAL ELEMENT
The objective of the Inventory Technical Element is to develop
understanding and models to estimate the following (DOE, 2000a, pi. 1-4~:
(1 ) the partitioning of wastes in process streams that were discharged to
waste disposal facilities in the vadose zone; (2) the behavior of specific
contaminants in these waste streams; and (3) release mechanisms and
rates from waste sites (e.g., burial grounds, liquid disposal cribs) to soils.
72
Science and Technology for Environmental Cleanup
To address these objectives, S&T within this element is organized
into six activities with 23 individual projects (Table 5.~:
1. Unplanned releases. The three projects under this activity
(Inv-1 to Inv-35) are focused on estimating the volumes and compositions
of leakage that occurred from the high-level waste tanks. As noted in
Chapter 2, documentation on these releases is quite limited. These
projects were under way at the time of writing this report, and the
information generated from the work is being supplied to the Office of
River Protection's Tank Farm Vadose Zone Project (see Chapter 3~.
2. Sod site waste inventory. The seven projects (Inv-4 to Inv-10)
under this activity are intended to provide best estimates with associated
uncertainties for contaminant source terms at various waste sites.
Estimates are being made of releases resulting from early to recent site
activities. These S&T projects were under way at the time of writing this
report, and the information produced from these activities will be used by
SAC (see Chapter 4) and the core projects.
3. Models for selected contaminants. The four projects (Inv-1 1
to Inv-14) under this activity are focused on modeling the distributions for
technetium-99, tritium, and iodine-129 in Hanford waste streams as inputs
to site-wide mass balance models. The stated intent of these projects is to
generate and refine the inventory estimates for these radionuclides.
4. Release models. The two projects planned under this activity
(Inv-15 to Inv-16) are intended to model contaminant releases from
various solid waste burial sites and iodine-129 "scrubber saddles."6 These
models will be used by the SAC to predict future contaminant releases at
these sites.
5. River source term. Four projects are planned under this
activity (Inv-17 to Inv-20) to estimate the present-day releases of
chromium, strontium-90, cobalt-60, and tritium to the Columbia River.
These activities will be used by the SAC and the River Monitoring Project
(see Chapter 3) and will also be used in the Columbia River conceptual
model (see Chapter 8~.
Reconciliation of model and Beld data. There are three
projects planned under this activity (lnv-21-lnv-23), all of which will
attempt to reconcile inventory estimates obtained from process models
with field data from the soil sites. This activity will be repeated for each
version of the SAC.
5The projects within this technical element are given these identification
numbers in DOE (2000a; Table 4-1~.
6Scrubber saddles are ceramic beds that were used to remove iodine-131
from fuel dissolver offgas in the chemical processing plants.
Inventory Technical Element
TABLE 5.1 Summary of S&T Activities and Planned S&T Projects Under the Inventory
Technical Element
S&T Activity S&T Project Objectives Project Hanford EMSP
Projects Duration Funding Funding
Planned (fiscal (thousand (thousand
years) dollars) dollars)
Unplanned
releases
3
Soil site waste 7
inventor
Estimate volumes and 1999-2000 Oa
waste compositions of
unplanned releases
from tanks containing
three classes of waste:
boiling waste, dilute
waste, and
concentrated waste
Provide a methodology 1999-2001 710
and preliminary
estimates of
contaminant
inventories for several
types of intentional and
unplanned discharges
to soil in the 200 Area
o
Models for 4 Develop 2000 190 0
selected methodologies to
contaminants describe Me
distribution of Tc-99,
H-3, and 1-129 in site
waste streams
Release models 2 Develop release 2000-2001 160b 0
models for residual
contamination from
various waste sees
River source 4 Determine the 2001 195b 0
term inventories of Cr. Sr-
90, Co-60, and H-3
released to the
Columbia River
Reconciliation of 3 Provide a 2001-2003 390 0
model and reconciliation of field
field data and model data for
estimating releases to
soil
NOTE: EMSP = Environmental Management Science Program
aThe funding shown in the table will be provided by the Office of River Protection.
bSome or all of the funding shown in the table will be provided by the System Assessment Capability.
SOURCE: DOE, 2000a, Figure 4-1, Table ~1.
73
74
Science and Technology for Environmental Cleanup
EVALUATION OF WORK PLANNED UNDER THE INVENTORY
TECHNICAL ELEMENT
There is not enough detail provided in the documentation of these
projects, including the Integration Project Roadmap (DOE, 2000a), to
undertake a detailed evaluation of the projects proposed or being
conducted within this technical element. This review is therefore more
general in nature, with only general comments offered on both work in
progress and possible S&T gaps.
Integration Project staff described the S&T for this technical
element during the committee's information-gathering sessions. They
noted that the methods used to obtain estimates for contaminant
inventories vary from waste stream to waste stream. Thus, one of the
primary products of these projects will be documentation of the methods
used to generate these inventory estimates. They noted that the methods
and estimates were not intended for direct use in regulatory applications
or remediation decisions, but rather were for use in the SAC and various
core projects.
These staff acknowledged that because of the lack of adequate
record keeping, especially during the early history of the Hanford Site,
they expect to encounter future surprises regarding unexpected
contaminants in the subsurface. They also emphasized that the most
important issue is not the magnitude of the total inventory, but how much
of that material actually poses a threat to the Columbia River and other
potential receptors.
Among the major efforts under this technical element is the
compilation of estimates of the characteristics of each waste stream at the
site. The plutonium production process at Hanford consumed large
quantities of uranium metal, acids, solvents, and other chemicals and
produced waste streams containing dozens of radionuclides and chemical
species. The quantities of uranium metal and chemicals used in
processing operations can be estimated from procurement records, and
the radionuclide and chemical outputs can be estimated from various
process models. Much less well known, however, is the partitioning of
chemicals and radionuclides into the large number of process streams
and secondary waste streams during plutonium production and recovery.7
In the committee's judgment, the work under way in this technical
element to obtain inventory estimates using process models is necessary
7For example, iodine-129 was partitioned into several process and waste
streams during chemical processing of irradiated uranium slugs. Some was
discharged to the atmosphere, some was captured in offgas scrubbers (see
footnote 6), and some ended up in the high-level waste that was sent to the tanks
and may later be transported into the environment through tank leaks.
Inventory Technical Element
75
to understand the current distribution of contaminants at the Hanford Site.
It is not clear, however, whether such inventories can be estimated with
sufficient confidence to be used in site-wide models such as the SAC
without validation through field characterization studies. Moreover,
although this process model work is essential, it is not sufficient to
establish the current distribution of contaminant releases in the
subsurface at the site. Very few measurements have been made of
subsurface contaminant distributions, even though such measurements
are essential for validating and reducing uncertainties in the process
model estimates. At present, there are not sufficient data to establish
either the distributions or the rates of migration of contaminants in the
vadose zone. Data have been obtained from a few cores in the 200 Area,
for example, and from a large number of gamma-ray measurements from
shallow wells in the tank farms (see Figure 2.10~. Although the shallow-
well studies have provided valuable data on radionuclide distributions
beneath some of the tank farms, contamination extends below or laterally
to the wells in many cases. The Integration Project has acknowledged this
problem, citing multiple instances in which contamination was found to
extend as far as the bottom of these shallow wells in the AX, BX, BY, SX,
TY, and U Tank Farms (DOE, 1998a, p. 4-66~.
Similarly, modeling flow of fluids in both the vadose zone and
groundwater requires a detailed knowledge of subsurface properties,
especially hydrological parameters. Because of the size and complexity of
the Hanford Site, obtaining these data by standard methods would be
prohibitively expensive and time-consuming. The S&T work on methods
to characterize contaminant distributions in the subsurface is also
potentially applicable to subsurface property characterization.
Due at least partially to the high cost of drilling in soil with
possible radioactive contamination, there has been very little coring in the
200 Area. Only a few "deep" wells (having depths between about 150 and
200 feet) have been drilled there, including a slant-drilled well that was
completed recently in the SX Tank Farm. These efforts are yielding
important data.8 However, the site plans to drill only one additional
borehole in other tank farms in each of the next two years. In view of the
fact that there are 67 suspect "leaked' tanks and hundreds of waste
disposal sites, the planned rate of characterization is not sufficient to
establish, even approximately, the current distribution, speciation (Sidebar
5.1), or potential for transport (e.g., Sidebar 5.2) in the subsurface or
important subsurface properties. This information is critical in evaluating
the potential for future migration and in validating inventory estimates.
The committee received a briefing on the SX Tank Farm slant borehole
results at its March 2001 meeting. This work is still in progress, and the results
have not yet been published.
76
Science and Technology for Environmental Cleanup
The Integration Project has made a major effort to maximize the
effectiveness of its characterization research by piggybacking on the
activities of the core characterization projects.9 Such efforts are highly
commendable, but they are clearly insufficient to produce the detailed
level of characterization data that will likely be needed to support
remediation decision making at the site.~°
Two options for achieving more rapid characterization of
contaminant distributions and properties of the subsurface at the Hanford
Site are (1 ) to increase the funds allocated to the characterization effort,
and/or (2) to develop and apply more cost-effective characterization
methods. Due to the very high cost of drilling, retrieving, and analyzing
core at contaminated sites,' it seems unlikely to the committee that
sufficient funds can be made available to dramatically increase the rate of
characterization using conventional methods. This suggests that
investments to develop alternate methods are needed, particularly for
characterization at depths greater than can be reached by push-in
technologies at Hanford.
The need to develop alternate characterization methods—in
particular, minimally invasive technologies that work under a wide variety
of ground conditions and allow real-time, in situ characterization has
been highlighted in another National Research Council report (NRC,
2000a). Such methods include steerable microdrills (drills having a
diameter of a few centimeters) with downhole instrumentation for in situ
measurements, and directional drills that allow samples to be obtained at
long horizontal distances from the drilling site. The committee agrees
that this is an important need and recommends that development of
cost-effective strategies and methods for characterization of
contaminant distributions and subsurface properties of the vadose
zone be made a priority of the S&T program.
Since the development of cost-effective methods would likely find
wide application across the DOE complex, much of the needed S&T work
9As noted in Chapter 3, the Integration Project refers to these piggybacking
activities as Wrap-around science."
'°The committee recognizes that it is not the responsibility of the Integration
Project's S&T program to do subsurface characterization at the Hanford Site.
Nevertheless, the committee believes that this characterization work must be
done if site remediation decisions are to have sound technical and risk bases.
44The high cost of characterization has long been an issue in the DOE
complex (see GAO, 1992, 1998~.
2 DOE will spend about $2.65 million to drill, retrieve, and analyze core from
the slant borehole in the SX Tank Farm (Mark Freshley, Pacific Northwest
National Laboratory, written communication, May 8, 2001~.
'3Push-in technologies are generally useful for sampling the upper 30 meters
or so of the subsurface, depending on ground conditions.
Inventory Technical Element
77
might be done in cooperation with other DOE programs for example, the
applied research and technology development programs sponsored by
the Office of Science and Technology within the Office of Environmental
Management, which has an annual R&D budget on the order of $200
million. The focus of S&T at Hanford might be to adapt and demonstrate
technologies developed elsewhere to the needs and environmental
conditions at the site.
S&T on subsurface properties and contaminant characterization
is potentially transferable to monitoring development efforts (see Chapter
9~. Therefore, the recommended characterization S&T, if planned
carefully, could also improve subsurface monitoring capabilities.
Consider, for example, the use of characterization boreholes for
monitoring. Current practices, which are driven largely by regulations,
often result in the permanent plugging of characterization boreholes after
characterization is completed to prevent the future spread of
contamination. Once plugged, these boreholes cannot be used for
monitoring. The development of methods to develop characterization
boreholes that do not have to be permanently plugged to prevent
contaminant spread could advance monitoring capabilities at Hanford and
other DOE sites.
In addition to radionuclide contamination, the vadose zone and
groundwater in the 200 West Area are also contaminated with hazardous
chemicals. As discussed in Chapter 2, for example, large quantities of
carbon tetrachloride (as dense nonaqueous phase liquid [DNAPL]) were
discharged to cribs in the 200 Area between 1955 and 1 g73, and most of
this contamination is estimated to remain in the subsurface (DOE, 2000e).
DOE has been unable to locate the source of this contamination and does
not know whether it poses a long-term threat to the river.
The amounts and locations of carbon tetrachloride in the vadose
zone and groundwater are important and unresolved issues. The
selection of remediation options and the effectiveness of recharge
controls to keep the contamination from spreading clepend to a great
extent on the location of contaminant source terms in the subsurface. The
characterization of DNAPL bodies in the subsurface, especially the
vadose zone, is a difficult technical challenge. Developing methods to
obtain such information is an appropriate S&T program task.
The Remediation Technical Element is working on the carbon
tetrachloride plumes in the 200 West Area to assist in the development of
a strategy for corrective actions. As discussed in Chapter 9, however, all
of this work is being supported through the Environmental Management
Science Program, and none of it appears to be focused directly on
delineating the locations of DNAPL in the subsurface. The committee
recommends that the S&T program develop a plan to characterize
carbon tetrachloride contamination in the 200 West Area, including a
Sconce and ~chno~ far amend Bags
pan 10 detecitheex~tenceofpure phaseslntheg~Dundwaterand
vadosezone.Th~ p~ncou~ bsusedbythecoreprograms Wee
Chaptered 10 dothe~otuaicha~eMzsdon work.
