May 19, 2014 

MEMORANDUM TO: Gregory F. Suber, Chief 

Low-Level Waste Branch 

Environmental Protection 

 and Performance Assessment Directorate 

Division of Waste Management 

 and Environmental Protection 

THRU: Christepher A. McKenney, Chief /RA/ 

Performance Assessment Branch 

Environmental Protection 

 and Performance Assessment Directorate 

Division of Waste Management 

 and Environmental Protection 

FROM: Cynthia S. Barr, Sr. Systems Performance Analyst

Performance Assessment Branch 

Environmental Protection 

 and Performance Assessment Directorate 

Division of Waste Management 

 and Environmental Protection 

SUBJECT: TECHNICAL REVIEW OF HYDROLOGICAL STUDIES AND DATA 

FOR IDAHO NATIONAL LABORATORY, IDAHO NUCLEAR 

TECHNOLOGY AND ENGINEERING CENTER, TANK FARM 

FACILITY (PROJECT NO. PROJ0735) 

The U.S. Nuclear Regulatory Commission (NRC) staff has performed a technical review of the 

several documents prepared by the U.S. Department of Energy (DOE) and its contractors that 

provide information on the hydrological system at the Idaho National Laboratory (INL), Idaho 

Nuclear Technology and Engineering Center Tank Farm Facility (INTEC TFF) in Idaho Falls, 

Idaho. This technical review report supports Key Monitoring Area (KMA) 3, “Hydrological 

Uncertainties”, as detailed in the NRC staff’s plan for monitoring the INL INTEC TFF 

(Agencywide Documents Access and Management System (ADAMS) Accession No. 

ML070650222). 

CONTACT: Cynthia Barr, FSME/DWMEP 

 (301) 415-4015
G. Suber -2- 

KMA 3, “Hydrological Uncertainties”, was developed by NRC staff to manage technical 

uncertainties identified in NRC staff’s Technical Evaluation Report for the INTEC TFF during the 

monitoring period. NRC staff has reviewed a number of hydrological studies and environmental 

monitoring reports, since it began monitoring the INTEC TFF in 2007. While review of this 

additional information has increased NRC staff’s understanding of the hydrological system at 

the INTEC TFF, the information has not fundamentally changed NRC staff’s understanding of 

the technical uncertainties, nor has it changed NRC staff’s Technical Evaluation Report 

conclusions. Therefore, NRC staff has decided to close KMA 3, “Hydrological Uncertainties”, at 

this time. This decision is based on (1) years of NRC review of DOE and DOE contractor 

prepared documents, including a supplemental, groundwater analysis that addresses technical 

concerns documented in NRC staff’s Technical Evaluation Report, and (2) results of NRC onsite 

observations related to INTEC TFF tank closure activities. Should technical issues arise in the 

future, NRC staff may reopen KMA 3, or create a new monitoring area. NRC staff will also 

continue to review environmental monitoring reports routinely under KMA 4 “Monitoring During 

Operations”, in conjunction with future onsite observation visits. 

Enclosure: 

Technical Review of Hydrological 

 Studies and Data at the INL INTEC TFF
G. Suber -2- 

KMA 3, “Hydrological Uncertainties”, was developed by NRC staff to manage technical 

uncertainties identified in NRC staff’s Technical Evaluation Report for the INTEC TFF during the 

monitoring period. NRC staff has reviewed a number of hydrological studies and environmental 

monitoring reports, since it began monitoring the INTEC TFF in 2007. While review of this 

additional information has increased NRC staff’s understanding of the hydrological system at 

the INTEC TFF, the information has not fundamentally changed NRC staff’s understanding of 

the technical uncertainties, nor has it changed NRC staff’s Technical Evaluation Report 

conclusions. Therefore, NRC staff has decided to close KMA 3, “Hydrological Uncertainties”, at 

this time. This decision is based on (1) years of NRC review of DOE and DOE contractor 

prepared documents, including a supplemental, groundwater analysis that addresses technical 

concerns documented in NRC staff’s Technical Evaluation Report, and (2) results of NRC onsite 

observations related to INTEC TFF tank closure activities. Should technical issues arise in the 

future, NRC staff may reopen KMA 3, or create a new monitoring area. NRC staff will also 

continue to review environmental monitoring reports routinely under KMA 4 “Monitoring During 

Operations”, in conjunction with future onsite observation visits. 

Enclosure: 

Technical Review of Hydrological 

 Studies and Data at the INL INTEC TFF 

DISTRIBUTION: ASchwartzman MFerdas (Region I) MRoberts (Rgn I) 

WIR Service List AMohseni 

ML14113A278 

OFC DWMEP DWMEP DWMEP DWMEP DWMEP 

NAME CBarr TMoon MHeath CMcKenney CBarr 

DATE 04/22/14 04/23/14 05/14/14 05/15/14 05/16/14 

OFFICIAL RECORD COPY 
Technical Review of Hydrological Studies and Data for the Idaho National Laboratory, 

Idaho Nuclear Technology and Engineering Center, Tank Farm Facility 

Date: May 16, 2014 

Reviewers: 

Cynthia S. Barr, Senior Systems Performance Analyst, U.S. Nuclear Regulatory Commission 

Background:

Since 2007, NRC staff has performed a number of technical review activities and onsite 

observation visits that address Key Monitoring Area (KMA) 3, “Hydrological Uncertainties”, 

as detailed in the NRC staff’s plan for monitoring the Idaho National Laboratory (INL), Idaho 

Nuclear Technology and Engineering Center, Tank Farm Facility (INTEC TFF) (NRC, 2006). A 

summary description of the KMA and related technical review activities and onsite observation 

visits is provided. KMA 3 reads as follows: 

“Relevant recent and future monitoring data and modeling activities should continue to 

be evaluated to ensure that hydrological uncertainties that may significantly alter the 

conclusions in the PA and TER are addressed. If significant new information is found, 

this information should be evaluated against the PA and TER conclusions (NRC, 2006).” 

NRC staff developed KMA 3 to address a number of technical uncertainties associated with the 

United States Department of Energy’s (DOE’s) representation of the hydrological system at the 

INL INTEC TFF, as it impacts the level of natural system performance assumed in DOE’s 

groundwater model1

. These uncertainties include the following: 

• Hydrogeologic Conceptual Model (HCM)—NRC staff’s analysis of groundwater 

monitoring data revealed potential inconsistencies between the HCM implemented in 

DOE’s groundwater model and field observations (e.g., potential differences in the 

degree of lateral transport observed in the unsaturated zone in DOE’s groundwater 

model versus in reality). The assumed level of natural attenuation of radiological 

releases from the tank farm facility during transport through the vadose zone may lead to 

an underestimate of projected dose reported in DOE’s Performance Assessment (DOE, 

2003).

 

1

 NRC staff reference to “DOE’s groundwater model” in this technical review report refers to the 

PORFLOW groundwater model used by DOE to project doses to a member of the public as documented 

in DOE’s INTEC TFF Performance Assessment (DOE, 2003). 
-2- 

• Infiltration Rates—NRC staff noted that a higher assumed infiltration rate was used in 

the Comprehensive Environmental Response, Compensation, and Liability Act 

(CERCLA) risk assessment model for the INTEC TFF (DOE, 2006a) compared to the 

value assumed in DOE’s groundwater model (DOE, 2003). Higher assumed infiltration 

rates could lead to faster travel times, less decay, and less dilution in the Snake River 

Plain Aquifer. 

• Big Lost River Seepage Rates—NRC staff evaluated Big Lost River seepage rates in 

DOE’s groundwater model and concluded that the relatively high seepage rates used in 

the model may have unrealistically dispersed and diluted concentrations of radiological 

constituents in the unsaturated zone. Overly optimistic dispersion and dilution of INTEC 

TFF releases affect projected concentrations and dose for all constituents (i.e., lower 

assumed Big Lost River seepage rates could lead to higher projected concentrations 

and dose). 

Based on its own calculations, NRC staff provided an easily defensible dilution factor for all 

constituents in its INTEC TFF technical evaluation report (NRC, 2006) based on Snake River 

Plain Aquifer dilution alone (i.e., no vadose zone attenuation was considered in this calculation). 

The NRC-calculated dilution factor was sufficient for DOE to demonstrate compliance with the 

performance objectives, provided the engineered system performs as well as assumed by DOE 

in its INTEC TFF performance assessment. The “conservative” dilution factor calculated by 

NRC is between 10 and 100 as illustrated in Figure 1 (see row labeled “Natural System 

(Saturated Zone)”. 

With respect to key radionuclides Technetium(Tc)-99 and Iodine(I)-129, NRC staff concluded 

(NRC, 2006) that credit from the engineered system is also needed to mitigate releases to 

levels that will meet the performance objectives (i.e., Snake River Plain Aquifer dilution alone, 

based on the “conservative” dilution factor calculated by NRC, is insufficient to ensure that 

Tc-99 and I-129 concentrations will be reduced to levels that will meet the performance 

objectives). If tank grout performance becomes an issue, additional credit for natural 

attenuation of Tc-99 and I-129 may be needed to demonstrate compliance with the performance 

objectives. However, natural attenuation of Tc-99 and I-129 in the subsurface is primarily 

limited to dilution and dispersion, as these two constituents are relatively non-sorbing in the 

subsurface at TFF and both of these constituents are long-lived, and are not expected to decay 

appreciably during transport through the environment. However, in the future, DOE could take 

credit for infiltration controls that would serve to increase dilution, if necessary, and if additional 

supporting information is provided. 

With respect to key radionuclide Strontium(Sr)-90, NRC staff concluded (NRC, 2006) that while 

the hazard associated with Sr-90 is relatively high owing to its high specific activity (e.g., see 

Figure 1 row labeled “Minimum Total Barrier Performance Needed for Compliance”), the risk 

from Sr-90 could be eliminated entirely through either engineered or natural system 

performance (or both engineered and natural system performance) given its relatively short 

half-life and ability to decay during transport to the point of compliance2

. 

 

2

 The point of compliance is located at the point of maximum exposure outside a 100 m buffer area 

surrounding the INTEC TFF. 
-3- 

A risk-significant inventory (i.e., total radionuclide activity) of Sr-90 is located outside of primary 

containment but within the concrete vaults that house Tanks WM-185 and WM-1873

. NRC staff 

concluded that if the concrete vaults perform significantly worse than assumed in DOE’s 

performance assessment model, then hydrological uncertainties associated with the transport of 

Sr-90 in the subsurface basalt and sedimentary interbeds will become more important given the 

total amount of credit needed to reduce the risk of this high specific activity radionuclide to 

acceptable levels. Sedimentary interbeds provide a significant barrier to mitigate the release of 

Sr-90 to the unsaturated zone. Sufficient information on sedimentary interbed sorption is 

available (laboratory and field-derived sorption coefficients have been developed for Sr-90 that 

can be used to model the transport of this constituent through sedimentary interbed materials). 

However, less information is available regarding the potential for infiltrating water to bypass 

relatively more sorbing sedimentary interbeds through relatively less sorptive, fractured basalt. 

As discussed in greater detail below, preferential flow through the vadose zone is thought to be 

an important mechanism for contaminant transport at the INTEC TFF. 

Based on the preceding discussion, NRC staff concluded in its monitoring plan (NRC, 2007) 

that closure of KMA 2, related to cementitious material performance, and KMA 3, related to 

hydrological system performance and uncertainty, are intimately related as they are both 

important for assessing INTEC TFF risk. Therefore, NRC staff expects that the status of KMA 3 

would be tied to the status of KMA 2. For example, if issues arise during evaluation of KMA 2 

(e.g., the tank grout is not effective in promoting and maintaining low solubility of key 

radionuclides in a reducing environment, or the grouted tank and vault system is not effective as 

a hydraulic barrier limiting Sr-90 release), then additional credit from natural attenuation, 

evaluated under KMA 3, may be needed to demonstrate compliance. Therefore, NRC staff has 

been monitoring both grouting operations, and relevant groundwater modeling and monitoring 

activities performed at the INTEC TFF since NRC staff monitoring began in 2007. A summary 

of technical reviews and onsite observations reported in previous NRC staff Periodic Monitoring 

Compliance Reports (NRC, 2008; NRC, 2009; NRC, 2010a; NRC, 2011; and NRC, 2012) is 

provided in Appendix A. A summary of recent DOE groundwater monitoring reports reviewed 

by NRC staff in this report are provided in Appendix B. 

 

 

3 The Sr-90 inventory is located in sand pads that Tanks WM-185 and WM-187 rest on inside the 

concrete vaults that house those tanks. 
-4- 

Figure 1: Relative Hazards of and Barriers Mitigating the Risk of Key Radionuclides at 

the INTEC TFF. Image Credit: Table 14 of NRC (2006). 

 
-5- 

NRC Staff Evaluation: 

Given uncertainty in the hydrological system at the INTEC TFF, NRC staff attempted to manage 

hydrological uncertainty with “conservative”4

 calculations in its Technical Evaluation Report 

(NRC, 2006). These calculations enabled NRC staff to reach conclusions regarding the ability 

of the disposal facility to meet the performance objectives for low-level waste disposal without 

the need for additional information from DOE prior to issuance of DOE’s final waste 

determination for the INTEC TFF. NRC staff also created KMA 3 “Hydrological Uncertainties” 

in its INTEC TFF monitoring plan (NRC, 2007) to allow NRC staff to continue to evaluate key 

technical uncertainties important to assessing compliance with the performance objectives and 

to help ensure that its Technical Evaluation Report calculations were in fact “conservative”. 

Because compliance with the performance objectives is also a function of engineered system 

performance, NRC staff has also monitored DOE disposal actions, such as tank grouting 

activities, to ensure that overall system performance is adequately constrained (see Appendix A 

for more information on previous technical reviews and onsite observations). 

NRC staff focused on hydrological uncertainties during the monitoring period due to the 

importance of the vadose zone in mitigating releases from the disposal facility in DOE’s 

groundwater model. For example, DOE indicated in a response to a follow-up Request for 

Additional Information (DOE, 2006b), that the large lateral extent of the modeled contaminant 

plume diverted laterally approximately 600 meters to the south of the Tank Farm Facility (see 

Figure 2 below) is due completely to the pressure gradient that results from the steady-state 

infiltration boundary condition for the Big Lost River. As documented in NRC staff’s Technical 

Evaluation Report (NRC, 2006), DOE’s response to NRC’s inquiry regarding the cause of the 

large lateral spread (DOE, 2006b) appeared inconsistent with explanations provided in the 

actual Performance Assessment documentation (DOE, 2003)—DOE’s Performance 

Assessment indicates that the numerical model predicts contaminant transport around the 

perched zones and through breaks in the sedimentary interbeds. In fact, the numerical model 

results show no perched zones along or near the flow path of the contaminant plume making 

the relevance of the statement regarding perched water in the Performance Assessment 

unclear. Additionally, there was no indication from the monitoring data that when Big Lost River 

flow did occur that contamination was deflected nearly half a mile laterally to the south of the 

TFF. Finally, DOE’s groundwater model results provided in DOE (2006c) reveal very significant 

natural attenuation of releases from the disposal facility (i.e., concentrations are reduced 

approximately four orders of magnitude or a factor of 10,000 during transport through the 

vadose zone as shown in Figure 3 below [see, for example, difference in peak concentrations 

between zones 1 and 2 at the source and zone 4 at the vadose zone “spill-way”]). Due to the 

uncertainties in the hydrological system and the high level of performance of the vadose zone in 

DOE’s performance assessment model, NRC staff advised DOE to consider new and significant 

information collected under the CERCLA program to determine the need for supplemental 

performance assessment modeling and/or updates to its performance assessment 

documentation. 

 

4

 The term “conservative” is used by NRC staff to mean that the assumption (or set of assumptions) tends 

to lead to a higher projected dose compared to another assumption (or set of assumptions). 
-6- 

Figure 2: Technetium Plume Emanating from the INTEC TFF Diverted Laterally 

Approximately 600 m to the South. Locations Near the Source (Zones 1 and 2), at the 

Modeled “Spill-way” (Zone 4) and at the Water Table (Zone 5) are also Depicted. See 

Figure 3 Below for Technetium Concentrations at These Locations Through Time (DOE, 

2006c). 
-7- 

Figure 3: Technetium Concentrations at Zone Locations (see Figure 2 for Zone 

Locations) 1 through 5 Versus Time (DOE, 2006c). 

During the 2010 onsite observation, NRC staff was provided an opportunity to discuss 

groundwater monitoring issues identified during NRC staff’s review of DOE’s Performance 

Assessment (DOE, 2003) with DOE contractors working on related CERCLA projects. DOE 

contractor staff confirmed NRC staff’s understanding of recent CERCLA monitoring results that 

indicate that only monitoring wells located very close to the Big Lost River, north the of the 

INTEC facility, show a water level response following rare occasions when Big Lost River flow 

occurs on site. DOE contractors indicated that Big Lost River flow is currently thought to have 

little impact on perched water further away from the river near INTEC facilities. The limited 

influence of the Big Lost River on perched water at the INTEC TFF based on current 

observations is contrary to conclusions drawn by DOE during development of its performance 

assessment models5

. More recently, INL scientists have determined that anthropogenic 

sources of water to the INTEC subsurface and precipitation infiltration have a much larger effect 

 

5

 It is important to note that the future influence of the Big Lost River on the INTEC TFF subsurface is 

uncertain. However, the NRC concern is that the INTEC TFF performance assessment model was 

calibrated with the thought that the Big Lost River contributed to perched water in the northern portion of 

the INTEC TFF, while the Big Lost River is now thought to have a much more modest influence on the 

hydrogeological system. Additionally, DOE provided follow-up information that indicated that the 

deflection of contaminant plumes due to Big Lost River seepage contributed to a large decrease in 

concentrations of radiological releases from the disposal facility in the INTEC TFF performance 

assessment model. Nonetheless, NRC staff recognizes that the future influence of the Big Lost River on 

radiological releases from the INTEC TFF facility is a function of many variables such as future human 

activities (e.g., diversion of water for irrigation) and climatic variability that are difficult to assess at this 

time, leading to significant uncertainty in the dose modeling projections. NRC staff attempted to manage 

this uncertainty with conservative assumptions in its Technical Evaluation Report (NRC, 2006). 
-8- 

on perched water at the INTEC TFF. DOE’s assumption that Big Lost River seepage was a 

source of perched water observed in the northern portion of the INTEC may have negatively 

impacted the calibration process, as well as led to overly optimistic assumptions regarding 

vadose zone performance. 

DOE contractors also presented data on perched and Snake River Plain Aquifer groundwater 

sampling at INTEC. Based on review of this data, NRC staff concludes that releases from TFF 

waste transfer system piping are proximal to the INTEC TFF and that limited lateral movement 

in the vadose zone, primarily to the southeast of the facility, has been observed (e.g., NRC, 

2008; NRC, 2009; NRC, 2012). There is also evidence of rapid, preferential flow through a 

complex network of fractures, as significant radioactivity associated with the TFF waste transfer 

system releases has also been observed to the north of the facility, up-gradient of the direction 

of saturated groundwater flow (see [DOE, 2004] for more information about TFF releases and 

contaminant plumes). Infiltration associated with melting of accumulated snow in the spring has 

also been implicated with rapid transport of constituents through the subsurface at INL. 

DOE’s Performance Assessment (2003) documentation discusses different mechanisms for 

perched water formation, as well as differences in conceptual models for simulation of 

contaminant flow and transport in the subsurface at INL. For additional details, consult DOE 

(2003). Baker (2003) also recognizes two primary conceptual models for simulating solute 

transport: diffuse and preferential flow models. In the diffuse flow conceptual model, perched 

water zones accumulates until the head is sufficient to drive infiltration through the perching 

layer. In the preferential flow conceptual model, perched water moves laterally until a path 

around the perching layer is encountered. Perched zones are risk-significant because higher 

saturations lead to greater relative hydraulic conductivities. Preferential flow paths through 

fractured basalt are risk significant because they can lead to fast transport and bypassing of 

sedimentary interbed layers that have a higher sorption potential. Vadose Zone Research Park 

scientists concluded that perched water can persist for long periods of time, and that lateral 

transport can be substantial. This phenomenon is also true at the INTEC TFF; however, the 

influence of the Big Lost River on flow at the INTEC TFF appears to be less significant than 

simulated in the DOE INTEC TFF performance assessment modeling, while anthropogenic 

sources of water and precipitation infiltration appear to be more important to perched water 

formation. Precipitation infiltration can lead to greater releases from the INTEC TFF, while 

deflection of contaminant plumes due to the pressure gradient imposed by Big Lost River 

seepage appears to have decreased contaminant concentrations in DOE’s groundwater model. 

Scientists at the Vadose Zone Research Park also concluded that preferential flow dominates 

transport in the subsurface at INL. However, fracture networks within rock layers are difficult to 

characterize using traditional methods (Baker, 2006). As a result, current vadose zone 

transport models fail to capture the potential for rapid transport through fractured rock. Baker 

(2006) concludes that a better understanding of mechanisms contributing to the formation, 

longevity, and transport within perched water zones and a means to characterize and 

incorporate fracture networks into vadose zone transport models is needed to facilitate longterm stewardship of the site. 

While DOE’s performance assessment model attempts to simulate the presence of perched 

water and by-passing of contaminant plumes through breaks in sedimentary interbed materials, 

several limitations in DOE’s conceptual model and PORFLOW model implementation are noted 

in NRC staff’s Technical Evaluation Report (NRC, 2006) and summarized in this technical 

review report. Of potentially greater risk-significance, DOE’s groundwater model simulated a 

high degree of lateral transport through the vadose zone at the INTEC TFF due to a pressure 
-9- 

gradient resulting from application of a relatively high Big Lost River seepage rate as a 

boundary condition in DOE’s groundwater model. While Big Lost River seepage was not 

assumed to increase releases from the TFF (releases from the TFF were independently 

modeled in a DUST-MS simulation using an infiltration rate of 4 cm/yr), the relatively high Big 

Lost River seepage boundary condition and resulting pressure gradient appears to have led to a 

very significant reduction in concentrations emanating from the TFF in DOE’s performance 

assessment model due to dilution and dispersion. While the presence of perched water in the 

subsurface at the INTEC TFF may facilitate lateral transport and by-passing of sedimentary 

interbeds in the future, the HCM implemented by DOE in its performance assessment model is 

not supported by field observations, and the significant credit afforded by the vadose zone in 

DOE’s model also appears to be unsupported. 

In 2011, DOE contractors prepared a supplementary analysis to address NRC staff’s key 

technical issues associated with DOE’s groundwater model (Portage, 2011). In the 

supplementary analysis report, DOE indicates that the Big Lost River was thought to be a 

principal source of recharge to the shallow perched water beneath the northern part of INTEC 

based primarily on water level fluctuations in perched monitoring wells from Rodriguez et al. 

(1997). DOE acknowledged that more recent monitoring data demonstrates that the lateral 

influence of the river during flow events is much less pronounced. Therefore, DOE performed 

the additional analysis to investigate the impact of more vertical flow on projected doses to 

address NRC staff’s concerns. 

In lieu of the two-dimensional PORFLOW model used to simulate contaminant flow and 

transport in the vadose and saturated zones in DOE’s INTEC TFF performance assessment, 

DOE elected to use the GWSCREEN code. The GWSCREEN code was also used in the 

INTEC TFF performance assessment to supplement PORFLOW model calculations for longer 

evaluation periods beyond 1,000 years (i.e., PORFLOW was only used for 1,000 year 

evaluations). Because DOE was attempting to simulate only one-dimensional, vertical flow in 

the unsaturated zone and one-dimensional horizontal flow in the saturated zone, the simpler 

one-dimensional GWSCREEN code could be used for this analysis. No significant changes to 

the source release modeling using the DUST-MS computer code were made. 

DOE assumed that only interbed sediments control flow and transport in the unsaturated zone 

and that flow and transport through the basalts is instantaneous. Other key parameters are 

listed in Table 1. Results of the GWSCREEN calculations are presented in Table 2. It is 

interesting to note, that DOE simulations indicated that vadose zone dilution and dispersion 

could be rather significant (DOE, 2006c), while only a factor of two higher dose is realized with 

the alternative conceptual model. Presumably, dilution and dispersion in the vadose zone in 

DOE’s performance assessment modeling is almost entirely offset by dilution and dispersion in 

the Snake River Plain Aquifer during transport to the 100 m well location in the supplemental 

analysis. Another possible explanation is that the unit Ci release in DOE’s simulations (DOE, 

2006c) exaggerated the level of attenuation in the vadose zone compared to a simulation in 

which Tc-99 and I-129 are released more slowly to the vadose zone. NRC staff noted in its 

2011 technical review that it would be helpful for DOE to further explain the performance impact 

associated with the alternative conceptual model and any offsets between vadose and saturated 

zone dilution to further support the revised estimates. NRC staff also noted that key modeling 

parameters such as Darcy velocity, effective porosity, dispersivity, etc., should be fully 

supported and a sensitivity analysis conducted to study the impact of parameter uncertainty on 

dose predictions. 
-10- 

While changes to uncertain parameter values affecting the GWSCREEN modeled dilution such 

as infiltration rates, Aquifer Darcy velocity, dispersivity, and well screen thickness could lead to 

higher projected doses, NRC staff is confident that the safety margin is sufficient to ensure that 

the performance objective for protection of members of the public (10 CFR 61.41) can be met 

with selection of more conservative parameter values. Finally, NRC staff’s review of recent 

monitoring reports in 2012 and 2013 (see Appendix B) reveals no new and significant 

information that would alter NRC staff’s Technical Evaluation Report conclusions (NRC, 2006). 

Therefore, NRC staff continues to have reasonable assurance that the performance objectives 

in 10 CFR Part 61, Subpart C can be met. Furthermore, because no significant technical issues 

were identified under KMA 2 “Grout Formulation and Performance”, during NRC staff’s 

observation of INTEC TFF tank grouting in 2007 and 2008, NRC concludes that DOE has 

provided sufficient information for NRC staff to close KMA 3, “Hydrological Uncertainties” at this 

time. Should new and significant information become available in the future that challenges 

NRC staff TER conclusions in these areas, NRC staff may reopen KMA 3, or create a new 

monitoring area. NRC staff will also continue to review environmental monitoring reports 

routinely, in conjunction with future onsite observation visits. NRC staff expects to close KMA 2 

“Grout Formulation and Performance” if no issues are identified during observation of final tank 

grouting activities for four remaining tanks at the INTEC TFF (Tanks WM-187 through WM-190). 

Table 1: Key Parameters Used in the GWSCREEN Analysis 

Parameter Value Units 

Source length 15.24 m 

Source width 1.0 m 

Infiltration rate 0.041 m 

Interbed thickness 17.6 m 

Bulk density—unsaturated 

zone 

1.9 g/cm3

Water-filled porosity—

unsaturated zone 

0.3 

Receptor distance 100 m 

Well screen thickness 15 m 

Aquifer Darcy velocity 21.9 m/yr 

Aquifer porosity 0.1 

Aquifer bulk density 1.9 g/cm3

Longitudinal dispersivity 9 m 

Transverse dispersivity 0.00001 m 

I-129 interbed Kd 0.1 L/kg 

I-129 aquifer Kd 0 L/kg 

I-129 tank inventory 2.6E-03 Ci 

Tc-99 interbed Kd 0.01 L/kg 

Tc-99 aquifer Kd 1.0 L/kg 

Tc-99 tank inventory 1 Ci 

 
-11- 

Table 2: GWSCREEN Analysis Results 

 INTEC TFF PA GWSCREEN Results 

Nuclide Time (yr) Dose 

(mrem/yr)^ 

Time (yr) Dose 

(mrem/yr)^ 

I-129 890 0.77 1090 1.31 

Tc-99 14,600 0.012* 14,770 0.023 

^Multiple mrem/yr by 0.01 to convert to mSv/yr. 

*The Tc-99 dose reported in the INTEC TFF performance assessment was in error (i.e., the 

DOE INTEC TFF performance assessment reported a dose for Tc-99 that was 10 times higher 

than the actual results). The error was corrected in this table. 

Teleconference or Meeting: 

There were no teleconferences or meetings to support this technical review activity. 

Follow-up Actions: 

There are no follow-up actions associated with this technical review activity. 

Open Issues: 

There are no open issues associated with this technical review activity. 

Conclusions: 

KMA 3, “Hydrological Uncertainties”, was developed by NRC staff to manage technical 

uncertainties identified in NRC staff’s Technical Evaluation Report for the INTEC TFF during the 

monitoring period. NRC staff has reviewed a number of hydrological studies and environmental 

monitoring reports, since it began monitoring the INTEC TFF in 2007. While review of this 

additional information has increased NRC staff’s understanding of the hydrological system at 

the INTEC TFF, the information has not fundamentally changed NRC staff’s understanding of 

the technical uncertainties, nor has it changed NRC staff’s Technical Evaluation Report 

conclusions. Therefore, NRC staff has decided to close KMA 3, “Hydrological Uncertainties”, at 

this time. This decision is based on (1) years of NRC review of DOE and DOE contractor 

prepared documents, including a supplemental, groundwater analysis that addresses technical 

concerns documented in NRC staff’s Technical Evaluation Report, and (2) results of NRC onsite 

observations related to INTEC TFF tank closure activities. Should technical issues arise in the 

future, NRC staff may reopen KMA 3, or create a new monitoring area. NRC staff will also 

continue to review environmental monitoring reports routinely under KMA 4 “Monitoring During 

Operations”, in conjunction with future onsite observation visits. 

 
-12- 

Appendix A: Summary of Previous Technical Reviews Reviewed and Documented in 

Previous Periodic Monitoring Compliance Reports (NRC, 2008; NRC, 2009; NRC, 2010a; 

NRC, 2011; and NRC, 2012)

2007 Technical Review

Early on in the monitoring period, NRC staff reviewed a number of studies related to the 

hydrogeological system at INTEC. These documents included publications generated from 

research conducted at the Vadose Zone Research Park located just southwest of INTEC on the 

Big Lost River (e.g., see Baker, 2006). The Vadose Zone Research Park was the site of 

field-scale experiments used to study the movement of water and solutes through alluvium, 

sediment, and basalt between land surface and the underlying Snake River Plain Aquifer. 

Recharge sources at the Vadose Zone Research Park included two new percolation ponds, 

and the Big Lost River. 

One goal of the research park was to improve the understanding of vadose zone processes that 

could be applied to the INL’s environmental restoration, waste management and facility 

operations. Predicting fluid and contaminant transport in the vadose zone near INTEC at the 

INL is problematic due to the complex geology underlying the site. In 2002, DOE installed a 

system of monitoring instruments in boreholes around the perimeter of the newly constructed 

percolation ponds that extended to the Big Lost River. DOE studied important mechanisms, 

including hydraulic spreading, formation of perched water, fluid transport through fast pathways, 

extent of vertical and lateral infiltration, aquifer recharge, sorption capacity of porous media, and 

Big Lost River recharge to the vadose zone. 

Data collected by DOE at the Vadose Zone Research Park indicates that perched water persists 

in the absence of local recharge, that water infiltration is complex and can reach large distances 

laterally and vertically in a non-sequential manner, and that flow paths are highly sensitive to 

discharge location and surface flux rates. The DOE Vadose Zone Research Park researchers 

studied the characteristics of perched zones, which may increase transport rates and lead to the 

by-passing of attenuating materials in the vadose zone, to better understand the effect of 

fracture flow and preferential pathways on solute flow and transport. These studies increased 

NRC staff’s knowledge of the complex hydrogeological system at the INTEC TFF. 

NRC staff also reviewed INTEC perched and saturated groundwater monitoring data conducted 

under the Comprehensive Environmental Response, Compensation, and Liabilities Act 

(CERCLA) program (Forbes, 2007). A Record of Decision for the Tank Farm Soil and INTEC 

Groundwater Operable Unit 3-14 was signed in May 2007 (DOE, 2007). Current risks 

associated with the tank farm soil and INTEC groundwater from previous releases include 

external exposure to soil contaminated with Cesium(Cs)-137 and ingestion of contaminated 

Snake River Plain Aquifer groundwater. The Snake River Plain Aquifer currently contains 

significant concentrations of Sr-90 and nitrate from previous injection well operations and Tc-99 

resulting from tank farm releases (DOE, 2009a). DOE concluded that, if left unmitigated, 

perched water could become a source of groundwater contamination in the Snake River Plain 

Aquifer above certain CERCLA action levels (e.g., maximum contaminant levels) beyond 2095. 

CERCLA modeling also shows that with decreased infiltration in a 9.5-acre area surrounding 

the TFF, the Snake River Plain Aquifer could meet action levels by 2095. This 9.5-acre area is 

designated a recharge control zone under the selected remedy. Thus, remedial activities are 

focused on the control of recharge to the subsurface. Data collected under the CERCLA 

program are reviewed by NRC staff to provide insights on the complex hydrogeological system 

at the INTEC TFF. 
-13- 

Concentrations of Sr-90 and Tc-99 exceeded their respective drinking water standards 

(i.e., maximum contaminant level or MCLs) in one or more of the aquifer monitoring wells 

(see Figure A-1) at or near INTEC6

. One aquifer well located southeast of INTEC showed an 

increase in Sr-90 from the previous year. Consistent with data collected in 2005, Tc-99 was 

detected above drinking water standards in two aquifer wells. The highest Tc-99 concentration 

of 80 Bq/L (2,150 pCi/L) was observed at a monitoring well located just north of the INTEC TFF. 

The second highest Tc-99 concentration of 46 Bq/L (1,240 pCi/L) was observed at a new 

aquifer well located just southeast of the tank farm. DOE has attributed detectable 

concentrations of Tc-99 to historical releases from the INTEC TFF. I-129 concentrations were 

below the MCL at all aquifer locations. None of the aquifer wells showed increases in I-129 

concentration. 

 

6

 NRC low-level waste regulations found in 10 CFR Part 61, Subpart C, do not provide concentration 

limits for radioactive constituents in groundwater. Comparisons to drinking water standards are made to 

provide a relative indication of the levels of contamination in the subsurface at INTEC from historical 

releases, and are not intended to imply that these standards are necessary to demonstrate compliance 

with criteria for non-high-level waste determinations. First, groundwater contamination from historical 

releases is not within the scope of non-high-level waste determinations. Second, drinking water 

standards established by the Environmental Protection Agency (EPA) consider only the drinking water 

pathway using a specific dose methodology described in EPA’s regulations. Based on DOE’s 

performance assessment results for the INTEC TFF, drinking water standards established by the EPA are 

generally more limiting than equivalent concentrations used to demonstrate compliance with the 10 CFR 

61.41 performance objective related to protection of members of the public from releases of radioactivity 

from the disposal facility. For example, drinking water standards for beta/gamma emitters (with the 

exception of Sr-90 and H-3 that are specifically listed in EPA regulations) are based on an annual dose 

equivalent to the total body or any internal organ greater than 0.04 mSv/yr (4 mrem/yr) calculated on the 

basis of 2 L/d drinking water intake using the 168 hour data list in “Maximum Permissible Body Burdens 

and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational 

Exposure,” National Bureau of Standards Handbook 69 as amended in August 1963. Using this method, 

the limit for Tc-99 is 33 Bq/L (900 pCi/L), and the limit for I-129 is 0.037 Bq/L (1 pCi/L). The EPA 

regulation, 40 CFR 141.66(d)(2), Table A, provides a specific limit for Sr-90 in the amount of 0.3 Bq/L 

(8 pCi/L). NRC staff calculated groundwater concentrations equivalent to a dose of 0.25 mSv/yr (25 

mrem/yr) total effective dose equivalent to a member of the public using dose methodology assumptions 

reported in DOE’s INTEC TFF Performance Assessment (DOE, 2003). Concentrations equivalent to 0.25 

mSv/yr (25 mrem/yr) are 1.5 Bq/L (40 pCi/L) for Sr-90, 110 Bq/L (3000 pCi/L) for Tc-99 and 0.37 Bq/L 

(10 pCi/L) for I-129. These concentrations are 5, 3, and 10 times higher than the respective MCLs. 
-14- 

Figure A-1: Snake River Plain Aquifer Groundwater Monitoring Network (Blue Labeled 

Wells Sampled Every Year, Black Labeled Wells Sampled Only in Odd Numbered Years) 
-15- 

Figure A-2: Perched Water Monitoring (Blue Labeled Wells Sampled Every Year, Black 

Labeled Wells Sampled Only In Odd Numbered Years)
-16- 

DOE perched water monitoring data from historical releases indicate that Sr-90 was the 

principal radionuclide detected in shallow perched water at INTEC (Forbes, 2007). Perched 

water wells (see Figure A-2) located at and southeast of the INTEC TFF exhibited the highest 

levels of Sr-90 contamination. The maximum Sr-90 activity concentration observed in perched 

water in 2006 was 7290 Bq/L (197,000 pCi/L). Consistent with recent detections in 2005, 

Cesium (Cs)-137 was detected at a lower concentration in one shallow perched water well 

located at the INTEC TFF. Cs-137 is less mobile than Tc-99, I-129, and Sr-90. Thus, this 

constituent was not detected in INTEC groundwater until 2005, long after Tc-99, I-129, and Sr90 were detected in monitoring wells at INTEC. NRC staff reviews data on Cs-137 and other 

less mobile radionuclides for discernible trends and to gather information regarding the 

attenuation of these constituents in the subsurface at INTEC to compare against DOE 

performance assessment assumptions. The highest levels of Tc-99 in shallow perched water 

were observed in monitoring wells located southeast of the INTEC TFF at levels lower than the 

drinking water standards. I-129 was detected in only one perched water well located south of 

the INTEC TFF at a concentration of 0.2 Bq/L (5 pCi/L), higher than reported in 2005, and the 

highest concentration reported in any well in recent years. I-129 concentration trends were 

either relatively constant or slowly declining over time at all other locations. 

The Big Lost River flowed past INTEC from April 16, 2006 until July 3, 2006. The effect on 

perched water levels was observed only at monitoring wells located closest to the river (within 

150 m [500 feet]). Little or no water level response was observed in wells located further from 

the river. A combination of precipitation infiltration (rainfall and snowmelt), and discharges or 

leaks of water from facility pipelines appears to account for continued recharge of the perched 

water beneath the northern part of INTEC (Forbes, 2007). The extent of shallow perched water 

beneath the northern portion of INTEC expanded eastward during 2005-2006, primarily due to 

an increase in on-site precipitation infiltration. 

NRC staff also conducted two onsite observations in 2007. During the first onsite observation, 

NRC staff evaluated the implementation of the quality assurance program and reviewed the 

records pertaining to tank grouting operations. NRC staff also observed and reviewed data 

collected to assess consistency with assumptions made in the waste determination. The 

observation determined that the quality assurance program of DOE and its contractor, CH2MWG Idaho, LLC (CWI), is being implemented effectively. NRC staff also determined CWI has a 

robust program for verifying that the grout components conform to applicable ASTM standards 

and that the final grout formulations are consistent with the design specifications assumed in the 

waste determination. NRC requested additional information regarding (i) the qualifications 

required of vendors to be on DOE's "approved vendors" list and (ii) the minimum cure time 

between grout pours. NRC staff also recommended that DOE provide documentation to 

demonstrate that the high water to cement ratio used in grouting tanks WM-104, WM- 105, and 

WM-106 will not adversely impact the expected performance of the grout. NRC recommended 

that DOE document deviations from its final waste determination and performance assessment 

and assess the risk significance of these deviations. 

On the second onsite observation, NRC staff reviewed records and observed ongoing tank 

grouting operations at the INTEC TFF. NRC determined that the DOE and CWI quality 

assurance program pertaining to tank grouting, grout formulation, and placement is being 

implemented effectively. NRC reviewed the documents DOE provided in response to an NRC 

request made during its April 2007 onsite observation visit. NRC closed the issues from the 

April 2007 observation report as it has determined that satisfactory information had been 

received. 
-17- 

For the issue on the qualification for vendors on the approved vendor list, DOE supplied 

information on the quality assurance program of its vendor, Valley Ready Mix, which ensures 

the grout materials it supplies to CWI meet DOE specifications, in terms of constituent 

formulation and standard grout characteristics. NRC recommended that if specific 

characteristics of the grout material, which are not part of the standard grout characteristics, 

such as the sulfide level of the slag, are being relied on for performance, specific requirements 

for testing should be added to the quality assurance programs. 

DOE provided adequate information for NRC to close the issue on the minimum cure time for 

the grout lifts. NRC is recommending that DOE remain cognizant of the potential for crack 

formation, which may be more of an issue at other sites which have not used very conservative 

assumptions for concrete degradation. The third issue addressed the water to cement ratio 

used in three of the small tanks, as compared to the water to cement ratio assumed in the waste 

determination. NRC determined that, based on the small radionuclide inventory in the 113.6 m3 

(30,000 gal) tanks, the high water to cement ratio of the grout used in three of the four 113.6 m3 

(30,000 gal) tanks poses a low risk of significantly increasing the dose to the general population. 

2008 Technical Review (NRC, 2008)

In 2008, NRC staff reviewed groundwater monitoring data collected from the previous year. 

Consistent with previous data, concentrations of Sr-90 and Tc-99 from historical releases 

exceeded their respective drinking water standards in two or more of the aquifer monitoring 

wells (see Figure A-1) at or near INTEC. At least one aquifer monitoring wells located 

southeast of INTEC showed an increase in Sr-90 from the previous year. Consistent with 

previous data, Tc-99 was detected at concentrations above drinking water standards in two 

aquifer wells. The highest Tc-99 concentration of 61 Bq/L (1650 pCi/L) was observed at a 

monitoring well located just north of the INTEC TFF. The second highest Tc-99 of 46 Bq/L 

(1230 pCi/L) was observed at a monitoring well located just southeast of the tank farm. I-129 

concentrations were below drinking water standards at all aquifer locations. None of the aquifer 

wells showed increases in I-129 concentration. 

DOE perched water monitoring data from historical releases indicates that Sr-90 is the principal 

radionuclide detected in shallow perched water at the INTEC (Forbes, 2008). Perched water 

wells (see Figure A-2) located at and southeast of the INTEC TFF exhibited the highest levels of 

Sr-90 contamination. The maximum Sr-90 activity concentration observed in perched water in 

2007 was 5880 Bq/L (159,000 pCi/L). Although Cs-137 was detected in one shallow perched 

water well located at the INTEC TFF the previous two years (2005 and 2006), this perched well 

was dry in CY2007 and therefore could not be sampled. Consistent with previous data, the 

highest well concentrations of Tc-99 in shallow perched water were observed in monitoring 

wells located southeast of the INTEC TFF, but at levels lower than drinking water standards. I129 was not detected in any perched water well in CY2007. 

NRC staff also conducted one onsite observation in 2008 to monitor ancillary equipment 

grouting. NRC staff did not observe any problems with the grouting of the ancillary equipment 

at the INTEC TFF and the staff determined that this program is being conducted in a manner 

that ensures the grout specifications meet those that were assumed in DOE's final waste 

determination. 

 
-18- 

2009 Technical Review (NRC, 2009)

DOE developed a Tank Farm Soil and INTEC Groundwater Remedial Design/Remedial Work 

Plan (DOE, 2008), and Long-Term Monitoring Plan (DOE, 2009a) that calls for annual reporting 

of groundwater monitoring results at the INTEC TFF. As part of its technical review activities for 

2009, NRC staff reviewed the 2008 annual report (DOE, 2009b) describing maintenance, 

inspection, and other activities performed to address contaminated soils and groundwater at 

INTEC. Activities reported in the annual report include inspections, monitoring, radiological 

surveys, and maintenance of various water management and infiltration control measures 

implemented at INTEC (e.g., storm water collection ditches, evaporation pond, culverts, and 

infiltration barriers). Despite efforts to identify and control anthropogenic sources, evaluation of 

perched water levels indicates that unknown sources of water from operations may continue to 

recharge the subsurface at INTEC. Potential sources will continue to be investigated. While 

trend data show the potential for above-average snowfall accumulation and associated melting 

and infiltration to increase perched water levels at INTEC in the short-term (e.g., higher than 

average snowfall and infiltration in the winter of 2007-2008), a longer term general decline in 

shallow perched water volumes over the period from 2006 through 2008 has been observed. 

2010 Technical Review (NRC, 2010a)

In 2010, NRC staff reviewed DOE’s annual report for FY2009 (DOE, 2010a). DOE’s annual 

monitoring report describes various activities designed to control infiltration including inspection 

activities, remedial actions (e.g., laying down asphalt over decommissioned areas, constructing 

and lining ditches), identification of anthropogenic sources of water, plugging abandoned wells, 

etc. Section 5 of the annual monitoring report describes long-term monitoring activities. 

Consistent with previous data, the highest Tc-99 concentrations were associated with 

monitoring well ICPP-MON-A-230 (82 Bq/L or 2,220 pCi/L) located near the INTEC Tank Farm 

and the second-highest Tc-99 concentrations were measured at aquifer well ICPP-2021 (46 

Bq/L or 1,240 pCi/L), located southeast of the Tank Farm (see Figure A-1 for well locations). 

These two wells were the only wells to exceed the Tc-99 MCL of 33 Bq/L (900 pCi/L). ICPP2020 was the only well that showed a significantly higher Tc-99 level (14 Bq/L or 382 pCi/L) 

compared to what was reported in previous years (e.g., 8 Bq/L or 215 pCi/L in FY 2007). All 

other wells showed stable or declining trends. 

Consistent with previous data, very high Sr-90 levels (>370 Bq/L or >10,000 pCi/L) were 

observed in the northern shallow perched water across INTEC. The highest Sr-90 

concentrations were observed in wells (see Figure A-2) southeast of the Tank Farm. The 

maximum Sr-90 concentration detected was 4810 Bq/L (130,000 pCi/L) at monitoring well ICPP2018. At most well locations, Sr-90 concentrations were similar to those observed during the 

previous year, but are approximately half those reported in the same wells during the mid-1990s 

due to decay and transport. Gross beta activity was detected at nearly all perched water 

sampling locations with the highest gross beta level occurring at well ICPP-2018 (11,500 Bq/L 

or 311,000 pCi/L) consistent with the Sr-90 data. 

Detectable gross alpha activity was reported at nearly all perched water sampling locations. 

The highest gross alpha activity was measured at well 33-2 at a value of 0.74 Bq/L (20.1 pCi/L). 

However, the gross alpha activity reported in a duplicate sample from the same well was only 

0.21 Bq/L (5.75 pCi/L). No plutonium isotopes were detected in either sample from well 33-2 

and uranium concentrations, although slightly elevated, could not account for all the alpha 

activity detected in this well. The high concentrations were thought to potentially be attributable 
-19- 

to laboratory error given the results of the duplicate sample. NRC staff indicated that it would 

continue to evaluate gross alpha measurements in this and other nearby wells to ensure that no 

new alpha emitting radionuclides that are not currently being targeted for sampling are 

identified. 

The lateral extent of the northern shallow perched water was mapped in the FY 2009 report. 

Shallow perched water wells MW-8, MW-11-2, MW-12-2, and MW-18-2 were essentially dry 

(<0.15 m or <0.5 ft of water) during the monitoring period. The Big Lost River flowed past 

INTEC between June 18 and July 4, 2009. However, only one monitoring well (Well BLR-CH) 

showed a significant water-level response to the river flow event. Well BLR-CH is the well 

closest to the river (i.e., 150 m or 500 ft from the river channel). After a 4-day time lag following 

the onset of flow in the river, the perched water level in Well BLR-CH rose 7 m (22 ft) over 16 

days. This is essentially the same water-level response observed in the past at this well 

location. No other wells showed any response to flow changes in the river. 

During the onsite observation conducted in August 2010 (NRC, 2010b), NRC staff listened to 

presentations and participated in discussions with DOE and contractor staff regarding ongoing 

remedial and groundwater monitoring activities performed under the CERCLA program at the 

INTEC TFF as described in the preceding paragraphs. Prior to the onsite observation, NRC 

staff also met with officials from the State of Idaho’s Department of Environmental Quality 

(Idaho DEQ) to discuss its oversight of the site, specifically its environmental monitoring 

program. NRC staff reviewed environmental monitoring reports generated by Idaho DEQ under 

KMA 4, related to protection of individuals during operations. DOE also indicated that it was in 

the process of completing a check-list7

 to determine the need for an update to the INTEC TFF 

Performance Assessment (DOE, 2003). NRC staff indicated the following: 

1. The INTEC TFF Performance Assessment documentation (DOE, 2003) should reflect 

the results of simulations performed and additional documentation generated during the 

National Defense Authorization Act Section 3116 consultation process to answer NRC 

staff inquiry regarding the cause and performance impact of the significant lateral spread 

of the contaminant plume emanating from the TFF to the south (e.g., caused by 

pressure gradient from BLR seepage and resulted in up to a factor of 10,000 decrease in 

contaminant concentrations emanating from the tank farm facility for relatively mobile 

[non-sorbing] constituents such as Tc-99 and I-129). 

2. DOE should consider (in its decision to update the INTEC TFF performance assessment 

model) recent data collected under the CERCLA program that appears to be 

inconsistent with the DOE performance assessment modeling results with respect to the 

impact of Big Lost River flow on contaminant fate and transport at the INTEC TFF. 

Following the onsite observation, DOE completed an annual review checklist to ensure that 

conclusions reached in the waste determination remain technically sound and based upon 

current information. The annual review checklist process indicated that the modeling approach 

and assumptions of DOE’s performance assessment should be assessed because recent 

CERCLA monitoring showed anthropogenic sources are the predominant recharge source 

rather than the Big Lost River. DOE conducted additional analysis for comparison to the INTEC 

 

7 Later during the August 2012 onsite observation, DOE provided NRC staff with a copy of the 

“Compliance and Monitoring Plan for Performing Grouting at the INTEC Tank Farm Facility Closure 

Project” (DOE, 2010b). This plan contains a check-list in Appendix D that indicates that types of triggers 

that might warrant further evaluation. 
-20- 

TFF performance assessment results to investigate the potential doses for more vertical 

movement of water due to the decreased influence of the Big Lost River at the TFF. 

NRC staff reviewed the analysis as discussed in the “2011 Technical Review” section. 

2011 Technical Review (NRC, 2011)

In 2011, NRC staff reviewed DOE’s 2010 annual report (DOE, 2011a) describing maintenance, 

inspection, and other activities performed to address contaminated soils and groundwater at 

INTEC. DOE’s annual reports are not intended to interpret data, form conclusions, or determine 

the effectiveness of the selected remedy; these topics are the subject of DOE’s 5-year review of 

the effectiveness of its CERCLA response actions. A 5-year review was recently completed and 

documented in a January 2011 report (DOE, 2011b). This report is discussed further below. 

DOE’s 2010 annual monitoring report (DOE, 2011a) describes various activities designed to 

control infiltration including inspection activities, remedial actions (e.g., laying down asphalt over 

decommissioned areas; constructing and lining ditches), identification of anthropogenic sources 

of water, plugging abandoned wells, etc. Section 5 of DOE’s annual monitoring report describes 

long-term monitoring activities that are of particular interest to NRC staff in its review of KMA 3. 

During the FY2010 reporting period DOE conducted groundwater sampling at 14 Snake River 

Plain Aquifer wells8

 and five additional wells sampled as part of the Idaho CERCLA Disposal 

Facility monitoring program9

. The operating unit monitoring plan requires sampling of 15 aquifer 

wells (see Figure A-1) during the even years. One well, USGS-57, was not sampled in FY2010 

because of an inoperable submersible pump at the time of the sampling event. Perched water 

samples were collected from six perched wells: 55-06, ICPP-2018, ICPP-2019, MW-2, MW-5-2, 

MW-10-2 (see Figure A-2). Well 33-1 was not sampled because the well contained insufficient 

water for sampling. Well MW-10-2 only had enough water for a partial suite of analyses. 

Consistent with previous data, the highest Tc-99 concentrations from the April 2010 sampling 

event were associated with monitoring well ICPP-MON-A-230 (71 Bq/L or 1,930 pCi/L) located 

near the INTEC Tank Farm and the second-highest Tc-99 concentrations were measured at 

aquifer well ICPP-2021 (50 Bq/L or 1,340 pCi/L), located southeast of the TFF. These two wells 

were the only wells to exceed the Tc-99 MCL10 of 33 Bq/L (900 pCi/L). All wells show stable or 

declining trends. 

Consistent with previous data, very high Sr-90 levels (>370 Bq/L or >10,000 pCi/L) were 

observed in the northern shallow perched water across INTEC. The highest Sr-90 

concentrations were observed in wells southeast of the TFF. The maximum Sr-90 

concentration detected was 5,700 Bq/L (154,000 pCi/L) at monitoring well ICPP-2018. At most 

well locations, Sr-90 concentrations were similar to those observed during the previous year, but 

are approximately half those reported in the same wells during the mid-1990s due to decay and 

transport. Gross beta activity was detected at nearly all perched water sampling locations with 

the highest gross beta level occurring at well ICPP-2018 (12,000 Bq/L or 326,000 pCi/L) 

 

8 SRPA wells CPP-01, ICPP-2020, ICPP-2021, ICPP-MON-A-1230, MW-18-4, USGS-040, USGS-41, 

USGS-42, USGS-47, USGS-48, USGS-51, USGS-52, USGS-59, USGS-067 were sampled in the April 

2010 event. 

9

 Wells ICPP-1782, ICPP-1783, ICPP-1800, ICPP-1829, and ICPP-1831 were sampled in the April 2010 

event. 

10 Note that NRC does not use MCLs or maximum contaminant levels to determine compliance with 

performance objectives in 10 CFR Part 61, Subpart C. MCLs are standards used by the Environmental 

Protection Agency in the CERCLA program and are provided for information only. 
-21- 

consistent with the Sr-90 data. Sr-90 was detected in 13 of 14 Snake River Plain Aquifer wells 

with samples from seven of the wells exceeding the Sr-90 MCL of 0.3 Bq/L (8 pCi/L). The 

highest measurement of Sr-90 in the aquifer was 1 Bq/L (24.8 pCi/L) at well USGS-47 located 

down gradient of the former INTEC injection well. All wells showed similar or slightly lower Sr90 levels compared to the previous reporting period. 

Although U-234 and U-238 were present at background levels, no detectable gross alpha levels 

were reported for any perched water sampling locations. The apparent discrepancy between 

uranium and gross alpha measurements may be explained by the lower detection limit for U 

isotopes compared to gross alpha of 0.02 Bq/L (0.5 pCi/L) and 0.15 Bq/L (4 pCi/L), respectively. 

Analysis revealed no detectable levels of Pu in the vadose zone and aquifer wells. 

The lateral extent of the northern shallow perched water was also mapped in the FY 2010 

report. Changes in water levels at several wells could be attributable to contributions from or 

elimination of anthropogenic sources of water. The Big Lost River is another potential source 

that can impact perched water levels at INTEC and flowed past INTEC between June 9 and 14 

and between June 17, 2010 and 20, 2010. Similar to previous observations, only one 

monitoring well (Well BLR-CH) showed a significant water-level response to the river flow event. 

Well BLR-CH is the well closest to the river (i.e., 152 m [500 ft] from the river channel). After a 

4-day time lag following the onset of flow in the river, the perched water level in Well BLR-CH 

rose 3 m (10 ft) over 15 days. This is similar to the water-level response observed in the past at 

this well location. No other wells showed any response to flow changes in the river. 

DOE also conducts a 5-year review of CERCLA response actions. The 5-year review was 

conducted for the INTEC and documented in a report issued in January 2011 (DOE, 2011b). 

With respect to perched water and groundwater, DOE concludes that the CERCLA response 

actions are functioning as intended and that previous exposure assessment assumptions 

remain valid. Since the 2007 Record of Decision, DOE indicates that significant progress has 

been made towards reducing precipitation infiltration and anthropogenic recharge at INTEC. 

Plans to install a low permeability cover over the tank farm and surrounding area will proceed as 

facilities are decommissioned. Although remedial activities are not yet complete and their 

ultimate effectiveness cannot be assessed at this time, DOE concludes that indications are 

favorable that the desired effect of these remedies will be achieved. 

During FY2010, DOE contractors also performed a modeling analysis that addressed an NRC 

staff technical concern made during NRC’s 2010 onsite observation. NRC staff encouraged 

DOE to consider (in its performance assessment maintenance review) recent data collected 

under the CERCLA program that appears to be inconsistent with the DOE INTEC TFF 

performance assessment modeling results with respect to the impact of Big Lost River flow on 

contaminant fate and transport at the INTEC TFF. Recent observations of limited perched 

water level response in vadose zone wells following Big Lost River flow and other investigations 

indicate that anthropogenic sources of water associated with INTEC operations, rather than Big 

Lost River seepage, are a more significant source of perched water currently observed at 

INTEC TFF. Ultimately, DOE determined that this issue was significant enough to include in its 

performance assessment maintenance checklist and performed additional modeling to 

determine the potential dose impact of more vertical movement of water in the vadose zone at 

the INTEC TFF compared to the significant lateral spread and dilution of TFF releases that 

occurs in the vadose zone in DOE’s INTEC TFF performance assessment model. 

NRC staff reviewed DOE’s modeling analysis (Portage, 2011) that showed while the doses 

would increase by roughly a factor of two, performance objectives could still be met. DOE’s 
-22- 

analysis was conducted using the DUST-MS code originally used to develop a source term in 

the INTEC TFF Performance Assessment (DOE, 2003). The source term was used as input to 

the GWSCREEN simulations that were used to simulate vadose and saturated zone transport. 

Because flow through the TFF vadose zone was assumed to be vertical in this alternative 

conceptual model (along with 1-D flow in the saturated zone), a multi-dimensional PORFLOW 

model was not needed to perform the groundwater simulations. NRC staff noted that, in 

general, the supplemental analysis appears to be technically sound. However, NRC staff also 

noted, that DOE’s PORFLOW simulations used to prepare the INTEC TFF PA indicated that 

vadose zone dilution would be rather significant (i.e., concentrations released from the tanks 

would be thousands to tens of thousands times less during transport through the vadose zone). 

Presumably, dilution and dispersion in the vadose zone in the PA modeling was almost entirely 

offset by dilution and dispersion in the Snake River Plain Aquifer during transport to the 100 m 

well location in the supplemental analysis. NRC staff noted in its 2011 technical review that it 

would be helpful for DOE to further explain the performance impact associated with the 

alternative conceptual model and any offsets between vadose and saturated zone dilution to 

further support the revised estimates. NRC staff also noted that key modeling parameters such 

as Darcy velocity, effective porosity, dispersivity, etc., should be fully supported and a sensitivity 

analysis conducted to study the impact of parameter uncertainty on dose predictions. 

 
-23- 

Appendix B: Summary of Recent Groundwater Monitoring Reports

Not Previously Reviewed or Documented

Documents Reviewed: 

DOE, 2012a, “Fiscal Year 2011 Annual Operations and Maintenance Report for Operable Unit 

3-14, Tank Farm Soil and INTEC Groundwater”, DOE/ID-11462, Revision 0, DOE Idaho, Idaho 

Falls, Idaho, July 2012. 

DOE, 2013, “Fiscal Year 2012 Annual Operations and Maintenance Report for Operable 

Unit 3-14, Tank Farm Soil and INTEC Groundwater”, DOE/ID-11476, Rev. 0, DOE Idaho, 

Idaho Falls, Idaho, June 2013. 

2011 Annual Report

During the FY2011 reporting period (April 2011), groundwater samples were collected from 

18 of 19 Snake River Plain Aquifer monitoring wells (DOE, 2012a) targeted for sampling in odd 

years per the Operable Unit 3-14 Long-Term Monitoring Plan (DOE, 2012b), as well as 5 

additional aquifer wells sampled as part of the Idaho CERCLA Disposal Facility monitoring 

program (see Figure A-1). One well, USGS-40, was not sampled. 

Sr-90 was detected in 14 of 18 Snake River Plain Aquifer groundwater wells with 9 of the 14 

Sr-90 detections above the MCL of 0.3 Bq/L (8 pCi/L). Consistent with previous years, the 

highest concentration of Sr-90 occurred in Well USGS-47 (see Figure A-1) at a value of 0.8 

Bq/L (21 pCi/L), a little lower than previous years. Sr-90 at well USGS-47 is thought to be 

associated with the former waste injection well and attributable to desorption and/or drain out of 

Sr-90 from perched water. 

Tc-99 was detected at 17 of 18 Snake River Plain Aquifer wells sampled, with two well 

concentrations measured at levels above the MCL of 33 Bq/L (900 pCi/L). The highest well 

concentration of 39 Bq/L (1250 pCi/L) occurred at ICPP-2021 located to the southeast of the 

tank farm. The other well with a sampled groundwater concentration above the MCL occurred 

at ICPP-MON-A-230, north of the tank farm, at a value of 35 Bq/L (940 pCi/L), although the 

Tc-99 concentration in this well was significantly lower than in previous years. Tc-99 detected in 

the two highest Snake River Plain Aquifer wells is associated with historical releases from the 

tank farm facility. I-129 was detected at a minority of wells and all detections were below the 

MCL of 0.04 Bq/L (1 pCi/L). The highest concentration was detected at well USGS-67 at a 

value of 0.02 Bq/L (0.5 pCi/L). I-129 concentrations have been generally declining since the 

highest detections were measured in the 1980s and 1990s. 

Perched water samples were obtained from 22 wells (see Figure A-2); however, insufficient 

water was collected from some wells to perform a full suite of laboratory analyses. Sr-90 was 

detected in most wells, with 11 wells above the MCL of 0.3 Bq/L (8 pCi/L). The highest well 

concentration was observed at ICPP-2018 at a value of 4500 Bq/L (121,000 pCi/L). Well 

concentrations were similar to previous measurements but significantly lower than those 

observed at the same wells in the mid 1990s, given Sr-90’s half-life of 30 years11. Tc-99 was 

detected in most perched wells but none above MCLs. Perched wells observe a declining trend 

in Tc-99 concentrations due to dispersion and dilution or drain out of Tc-99 from the perched 

zone. I-129 detections have been observed in perched wells but only one well has I-129 above 

the MCL. 

 

11 Only one-half of Sr-90 remains after every 30 years, or only approximately 10 percent after 100 years. 
-24- 

The extent of perched water was also mapped in the FY2011 report. Consistent with past 

measurements, several shallow perched water wells MW-8, MW-11-2, MW-12-2, and MW-18-2 

were essentially dry. Notable changes in perched water levels include the following: 

1. Well 33-2 has historically had one of the highest perched water levels at INTEC; 

however, this well declined 2.4 m (8 ft) between the summer of 2010 and January 2011, 

when the well went dry for the first time since 2003. Then, the water level suddenly 

began rising and increased 2.4 m (8 foot) beginning in February through March 2011. 

The cause of the abrupt rise and fall of the water level was not confirmed. 

2. The Big Lost River flowed past INTEC between June 25 and July 13, 2011, with only 

monitoring well BLR-CH (see Figure A-1), closest to the river, showing any significant 

water-level response, similar to past observations. A 8 m (24 ft) water level rise in Well 

BLR-CH occurred over 2 weeks with a 4 day lag time between the river flow event and 

water level rise. 

3. Well MW-5-2 showed a sharp water-level rise beginning in late December 2010, possibly 

related to steam condensate discharged to an active shallow injection well, and then a 

sharp water-level decline beginning in July 2011 and continuing through the end of 

September 2011. 

Progress has been made to reduce perched water recharge; however, DOE expects perched 

water to persist as long as INTEC is an operational, industrial facility with pressurized 

underground water pipelines periodically developing leaks. 

With regard to tensiometer measurements, the largest change was associated with the Big Lost 

River set at the 40 m (132 ft) depth beginning in late June 2011 in response to Big Lost River 

flow. By September 2011, water potentials in the BLR-CH tensiometer had returned to values 

similar to those observed before the river flow event. At the central well set, the 85 m (280 ft) 

depth tensiometer began rising sharply in mid-April 2011 possibly due to a large underground 

water leak from a buried raw water pipeline. At the sewage treatment lagoon well set, the 32 m 

(104 ft) tensiometer showed a wetting pulse during February to March 2011 likely due to 

infiltration of melt water. Finally, at the tank farm set, the 36 m (118 ft) tensiometer showed a 

wetting pulse beginning in late July 2011 following Big Lost River Flow that began on June 25, 

2011. 

2012 Annual Report

During the FY2012 reporting period (March 2012), groundwater samples were collected from all 

14 Snake River Plain Aquifer monitoring wells (DOE, 2013) targeted for sampling in even years 

per the Operable Unit 3-14 Long-Term Monitoring Plan (DOE, 2012b), as well as 5 additional 

aquifer wells sampled as part of the Idaho CERCLA Disposal Facility monitoring program. 

Sr-90 was detected in 12 of 14 Snake River Plain Aquifer groundwater wells with 7 of the 12 

Sr-90 detections above the MCL of 0.3 Bq/L (8 pCi/L). Consistent with previous years, the 

highest concentration of Sr-90 occurred in Well USGS-47 (see Figure A-1) at a value of 0.5 

Bq/L (17 pCi/L), a little lower than previous years. Sr-90 at well USGS-47 is thought to be 

associated with the former waste injection well and attributable to desorption and/or drain out of 

Sr-90 from perched water. Figure A-1 shows the location of Snake River Plain Aquifer wells. 

Tc-99 was detected at nearly all of the Snake River Plain Aquifer wells sampled, with two well 

concentrations measured at levels above the MCL of 33 Bq/L (900 pCi/L). The highest well 
-25- 

concentration of 45 Bq/L (1,450 pCi/L) occurred at ICPP-MON-A located to the north of the tank 

farm. The other well with a sampled groundwater concentration above the MCL occurred at 

ICPP-2021, southeast of the tank farm, at a value of 33 Bq/L (1070 pCi/L). Tc-99 detected in 

the two highest Snake River Plain Aquifer wells is associated with historical releases from the 

tank farm facility. Figure B-1 provides Tc-99 concentration trends at select Snake River Plain 

Aquifer wells. I-129 concentrations were below reporting levels in all sampled wells. The 

highest concentration was detected at well USGS-67 at a value of 0.02 Bq/L (0.5 pCi/L). I-129 

concentrations have been generally declining since the highest detections were measured in the 

1980s and 1990s. 

Figure B-1: Tc-99 Concentration Trends for Selected Snake River Plain Aquifer Wells. 

Image Credit: Figure A-10 (DOE, 2013). 

 
-26- 

Perched water samples were obtained from 6 wells (see Figure A-2). One well, 33-1, had 

insufficient water for sampling, and well MW-10-2 had insufficient water collected to perform a 

full suite of laboratory analyses. Sr-90 was detected at all sampled wells, and all wells sampled 

were above the MCL of 0.3 Bq/L (8 pCi/L). The highest well concentration was observed at 

ICPP-2018 at a value of 4740 Bq/L (153,000 pCi/L). Well concentrations were similar to 

previous measurements but significantly lower than those observed at the same wells in the mid 

1990s, given Sr-90’s half-life of 30 years. Tc-99 was detected in most perched wells but none 

above MCLs. Perched wells observe a declining trend in Tc-99 concentrations due to 

dispersion and dilution or drain out of Tc-99 from the perched zone. I-129 was not detected in 

any perched well sampled in 2012. In general, I-129 has been steadily declining over the past 

several years. 

The extent of perched water was also mapped in the FY2012 report. Consistent with past 

measurements, several shallow perched water wells MW-8, MW-11-2, MW-12-2, and MW-18-2 

were essentially dry. Notable changes in perched water levels include the following: 

1. Beginning in January 2012, water levels in MW-6 and 33-3 rose sharply as a result of a 

nearby potable water leak. The 7.6 million L (2 million gal) leak began on January 5, 

2012, and caused a 4.5 m (15 ft) rise in the water level in MW-6 and a 2 m (7 ft) rise in 

the water level in MW-33. A sharp decline in the water levels occurred beginning on 

May 19, after the leak was eliminated on May 17, 2012. The water levels declined to 

nearly pre-leak levels by the end of June 2012. 

2. Except for Wells MW-6 and 33-3 that were impacted by the potable water leak, perched 

water levels declined in most of the remaining wells during FY2012. Wells 33-2, ICPP2018, 33-4-1, and 37-4 went dry during the reporting period, with the latter two wells 

going dry for the first time since they were installed in the 1990s. 

A rare Big Lost River winter flow occurred from November 2011 to February 2012 leading to the 

greatest rise in water potential in a well set near the Big Lost River at the 40 m (132 ft) level, 

beginning in late November. By July 2012, water potentials at the BLR-CH tensiometer had 

returned to pre-event values. Also noteworthy, at the sewage treatment lagoon well set, the 

tensiometer at 104 ft showed a wetting pulse during November 2011 to March 2012 that may be 

the result of infiltration of melt water into the vadose zone. 

 
-27- 

Appendix C: References

Baker, K., et al., “Conceptual Models of Flow through a Heterogeneous, Layered Vadose Zone 

under a Percolation Pond,” INEEL/EXT-04-01679, Idaho National Engineering and 

Environmental Laboratory, Bechtel BWXT Idaho, LLC, February 2004. 

Baker, K., “Idaho National Laboratory Vadose Zone Research Park Geohydrological Monitoring 

Results,” INL/EXT-05-01044, Idaho National Laboratory, Geosciences Department, Idaho Falls, 

Idaho, January 2006. 

DOE, 2003, “Performance Assessment for the Tank Farm Facility at the Idaho National 

Engineering and Environmental Laboratory,” DOE/ID–10966, Rev. 1, (Errata December 2, 

2003), DOE Idaho, Idaho Falls, Idaho, 2003. 

DOE, 2004, “Evaluation of Tc-99 in Groundwater at INTEC: Summary of Phase 1 Results,” 

ICP/EXT–04-244, Rev. 0, DOE Idaho, Idaho Falls, Idaho, September 2004. 

DOE, 2006a, “Operable Unit 3-14 Tank Farm Soil and Groundwater Remedial Investigation/ 

Baseline Risk Assessment,” DOE/NE–ID–11227, Rev. 0, DOE Idaho, Idaho Falls, Idaho, April 

2006. 

DOE, 2006b, “Follow-up Item from June 1 and 20, 2006, Meetings with DOE on INL TFF Waste 

Determination (Related to the large lateral extent of the contaminant plume),” DOE Idaho, Idaho 

Falls, Idaho, 2006. 

DOE, 2006c, “Follow-up Item from June 1 and 20, 2006, Meetings with DOE on INL TFF Waste 

Determination (Providing center-line plume concentrations),” DOE Idaho, Idaho Falls, Idaho, 

2006. 

DOE, 2008, “Operable Unit 3-14, Tank Soil and INTEC Groundwater Remedial Design/ 

Remedial Action Work Plan,” DOE/ID-11333 Rev. 0, DOE Idaho, Idaho Falls, Idaho, June 2008. 

DOE, 2007, “Record of Decision for Tank Farm Soil and Idaho Nuclear Technology and 

Engineering Center Groundwater, Operable Unit 3-14,” DOE/ID–11296, Rev. 0., DOE Idaho, 

Idaho Falls, Idaho, May 2007. 

DOE, 2009a, “Operable Unit 3-14, Tank Farm Soil and INTEC Groundwater Long-Term 

Monitoring Plan,” DOE/ID-11334, Rev. 0, DOE Idaho, Idaho Falls, Idaho, May 2009. 

DOE, 2009b, “2008 Annual Report for Operable Unit 3-14, Tank Farm Soil and INTEC 

Groundwater,” DOE/ID-11395, Revision 0, DOE Idaho, Idaho Falls, Idaho, June 2009. 

DOE, 2010a. “Fiscal Year 2009 Annual Report for Operable Unit 3-14, Tank Farm Soil and 

INTEC Groundwater,” DOE/ID-11419, Revision 0, DOE Idaho, Idaho Falls, Idaho, April 2010. 

DOE, 2010b. “Compliance and Monitoring Plan for Performing Grouting at the INTEC Tank 

Farm Facility Closure Project.” PLN-2309, Revision 3, DOE Idaho, Idaho Falls, Idaho, October 

2010. 
-28- 

DOE, 2011a, “Fiscal Year 2010 Annual Operations and Maintenance Report for Operable Unit 

3-14, Tank Farm Soil and INTEC Groundwater,” DOE/ID-11442, Rev. 0, DOE Idaho, Idaho 

Falls, Idaho, August 2011. 

DOE, 2011b, “Five-Year Review of CERCLA Response Actions at the Idaho National 

Laboratory Site—Fiscal Years 2005-2009,” DOE/ID-11429, Rev. 0, DOE Idaho, Idaho Falls, ID, 

January 2011. 

DOE, 2012a, “Fiscal Year 2011 Annual Operations and Maintenance Report for Operable Unit 

3-14, Tank Farm Soil and INTEC Groundwater”, DOE/ID-11462, Revision 0, DOE Idaho, Idaho 

Falls, Idaho, July 2012. 

DOE, 2012b, “Operable Unit 3-14, Tank Farm Soil and INTEC Groundwater Long-Term 

Monitoring Plan,” DOE/ID-11334, Rev. 2, DOE Idaho, Idaho Falls, Idaho, April 2012. 

DOE, 2013, “Fiscal Year 2012 Annual Operations and Maintenance Report for Operable Unit 3-

14, Tank Farm Soil and INTEC Groundwater”, DOE/ID-11476, Rev. 0, DOE Idaho, Idaho Falls, 

Idaho, June 2013. 

Forbes, J.R., and L.S. Cahn, “Monitoring Report/Decision Summary for Operable Unit 3-13, 

Group 4, Perched Water,” DOE/ID-11326, Revision 0, Project No. 24668, DOE Idaho, Idaho 

Falls, Idaho, October 2007. 

Forbes, J.R., and S.L. Ansley, 2008, “INTEC Groundwater Monitoring Report (2007)”, DOE/ID11356, Revision 1, DOE Idaho, Idaho Falls, Idaho, June 2008. 

NRC, 2006, “Nuclear Regulatory Commission Technical Evaluation Report for the U.S. 

Department of Energy Idaho National Laboratory Site Draft Section 3116 Waste Determination 

for Idaho Nuclear Technology and Engineering Center Tank Farm Facility,” ML062490142, 

NRC, Washington, DC, October 2006. 

NRC, 2007, “Nuclear Regulatory Commission Plan for Monitoring the Disposal Actions Taken 

by the U.S. Department of Energy at the Idaho National Laboratory Idaho Nuclear Technology 

and Engineering Center Tank Farm Facility in Accordance with the National Defense 

Authorization Act for Fiscal Year 2005.” ML070650222, NRC, Washington, DC, April 2007. 

NRC, 2008. “NRC Periodic Compliance Monitoring Report for U.S. Department of Energy NonHigh-Level Waste Disposal Actions—Annual Report for Calendar Year 2007,” NUREG-1911, 

ML082280145, NRC, Washington, DC, August 2008. 

NRC, 2009, “NRC Periodic Compliance Monitoring Report for U.S. Department of Energy NonHigh-Level Waste Disposal Actions—Annual Report for Calendar Year 2008,” NUREG-1911, 

Revision 1, ML091400501, NRC, Washington, DC, May 2009. 

NRC, 2010a, “NRC Periodic Compliance Monitoring Report for U.S. Department of Energy NonHigh-Level Waste Disposal Actions—Annual Report for Calendar Year 2009,” NUREG-1911, 

Revision 2, ML101950385, NRC, Washington, DC, June 2010. 

NRC, 2010b, “Nuclear Regulatory Commission August 10, 2010 Onsite Observation Report for 

the Idaho National Laboratory Idaho Nuclear Technology and Engineering Center Tank Farm 

Facility,” ML102770022, NRC, Washington, DC, October 2010. 
-29- 

NRC, 2011, “NRC Periodic Compliance Monitoring Report for U.S. Department of Energy NonHigh-Level Waste Disposal Actions—Annual Report for Calendar Year 2010,” NUREG-1911, 

Revision 3, ML111890412, NRC, Washington, DC, February 2012. 

NRC, 2012, “NRC Periodic Compliance Monitoring Report for U.S. Department of Energy NonHigh-Level Waste Disposal Actions—Annual Report for Calendar Year 2011,” NUREG-1911, 

Revision 4, ML12234A576, NRC, Washington, DC, August 2012. 

Portage, 2011, “Tank Farm Performance Assessment—GWSCREEN Modeling to Evaluate the 

Reduced Impact of the Big Lost River on Perched Water,” Prepared for CH2M-WG Idaho, LLC, 

Contract DE-AC07-05ID14516500116.32 by Portage, Inc., Idaho Falls, ID, August 2011. 

Rodriguez, R.R., et al., “Comprehensive RI/FS for the Idaho Chemical Processing Plant OU 3-

13 at the INEEL—Part A, RI/BRA Report (Final)”, DOE/ID-10534, DOE Idaho, Idaho Falls, 

Idaho, November.