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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

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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.

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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 cOmpexspeiaiOn 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 OCR for page 66
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.

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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'; ' ;~.

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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.

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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.

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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

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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.

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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.

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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 methodsin 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.

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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

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