Source: http://www.wipp.energy.gov/library/CRA/CRA-2014/CRA/Section_32/Section_32.htm
Timestamp: 2019-04-24 22:35:17+00:00

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(a) "Performance assessments shall consider natural processes and events, mining, deep drilling, and shallow drilling that may affect the disposal system during the regulatory time frame."
(b) "Assessments of mining effects may be limited to changes in the hydraulic conductivity of the hydrogeologic units of the disposal system from excavation mining for natural resources. Mining shall be assumed to occur with a one in 100 probability in each century of the regulatory time frame. Performance assessments shall assume that mineral deposits of those resources, similar in quality and type to those resources currently extracted from the Delaware Basin, will be completely removed from the controlled area during the century in which such mining is randomly calculated to occur. Complete removal of such mineral resources shall be assumed to occur only once during the regulatory time frame."
(c) "Performance assessments shall include an analysis of the effects on the disposal system of any activities that occur in the vicinity of the disposal system prior to disposal and are expected to occur in the vicinity of the disposal system soon after disposal. Such activities shall include, but shall not be limited to, existing boreholes and the development of any existing leases that can be reasonably expected to be developed in the near future, including boreholes and leases that may be used for fluid injection activities."
(d) "Performance assessments need not consider processes and events that have less than one chance in 10,000 of occurring over 10,000 years."
(3) Documents why any processes, events or sequences and combinations of processes and events identified pursuant to paragraph (e)(1) of this section were not included in performance assessment results provided in any compliance application."
Performance Assessment (PA) is a process that assesses the likelihood that the Waste Isolation Pilot Plant (WIPP) will meet the release limits specified by 40 CFR 191.13 for 10,000 years after disposal. The PA process must consider both natural and man-made processes and events which have an effect on this disposal system.
Section 194.32 (U.S. EPA 1996) requires that PAs consider the effects of excavation mining, drilling fluid injection, and future development of leases. In addition, the PA must also consider the effects of current activities such as secondary oil recovery methods (waterflooding), disposal of natural brine, and solution mining to extract brine in the vicinity of the repository. Section 194.32 requires identification of all features, events, and processes (FEPs), or sequences or combinations of processes and events that could occur during the regulatory time frame that may affect the repository, and documentation of why certain events or groups of events are not included, if so warranted.
Therefore, the PA methodology for the WIPP includes a process that compiles a comprehensive list of the FEPs that are relevant to disposal system performance. Those FEPs determined by screening analysis to have the potential to affect performance are represented in scenarios and quantitative calculations using a system of linked computer models to describe the interaction of the repository with the natural system, both with and without human intrusion. For the Compliance Certification Application (CCA) (U.S. DOE 1996), the U.S. Department of Energy (DOE) first compiled a comprehensive list of FEPs which was then subjected to a screening process that eventually lead to the set of relevant FEPs used in PA to demonstrate the WIPP's compliance with the long-term disposal standards.
· Screened Out-Regulation (SO-R): For example, future human-initiated events and processes (EPs) may be excluded from consideration for regulatory reasons (e.g., deliberate drilling intrusions). 40 CFR § 194.25(a) requires that characteristics of the future remain what they are at the time the compliance application is prepared, provided that such characteristics are not related to hydrogeologic, geologic, or climatic conditions.
· Screened Out-Probability (SO-P): 40 CFR § 194.32(d) states that PA need not consider processes and events that have less than 1 in 10,000 chance of occurring over 10,000 years.
- Insignificant Consequences. The DOE eliminated FEPs where there was a reasonable expectation that the remaining probability distribution of cumulative releases would not be significantly changed by such omissions. These FEPs are designated SO-C.
- Beneficial FEPs. FEPs that are potentially beneficial to disposal system or subsystem performance were eliminated to simplify the analysis. This argument may be used when there is uncertainty as to exactly how the FEP should be incorporated into assessment calculations, or when incorporation would incur unreasonable difficulties. This is considered a conservative decision. These FEPS are designated SO-C Beneficial (e.g., the accumulation of radioactive contaminants in soils).
The FEPs retained in the PA were accounted for under calculations of either the undisturbed performance (UP) or disturbed performance (DP) (see the CCA, Chapter 6.0, Sections 6.2.2.2 and 6.2.2.3).
· UP includes the predicted behavior of the disposal system assuming it is not disrupted by human intrusion or the occurrence of unlikely natural events.
· DP includes the predicted behavior of the disposal system assuming disruption by human intrusion or other actions, including future drilling and mining activities.
In the CCA, the DOE discussed the origin and development of the WIPP FEPs list, as well as well-defined screening criteria in the CCA, Appendix SCR. A list of the WIPP-relevant FEPs is also provided in the CCA, Chapter 6.0, Section 6.2. The DOE identified approximately 237 FEPs in three major categories: natural (N), waste- and repository-induced (W), and human-initiated (H). Of particular importance to the performance of the disposal system were those FEPs dealing with mining, deep drilling, and shallow drilling, because these FEPs have the greatest potential for disruption of the repository via inadvertent intrusion. The CCA and supporting documents illustrated the process used by the DOE to implement the FEPs in scenarios relevant to PA.
The U.S. Environmental Protection Agency (EPA) evaluated the adequacy of the natural FEPs appropriate to the disposal system and how these were considered in the PA. The EPA also evaluated the DOE's consideration of mining and drilling in the PA. The EPA performed a critical review of each step in the DOE FEP selection process for the CCA, including identification and listing of the potentially disruptive FEPs, screening of these FEPs, combination of FEPs to form scenarios, screening of scenarios, and the final formation of scenarios for use in the CCA PA.
The EPA concluded that the initial FEP list assembled by the DOE was sufficiently comprehensive. This list appropriately screened out EPs on the basis of probability, consequence, or regulatory requirements. The EPA concluded that the DOE considered and incorporated into PA numerous natural EPs, mining, and deep drilling. The EPA concluded that the DOE considered shallow drilling and appropriately screened it out on the basis of low consequence. The DOE also appropriately followed regulatory requirements when it did not consider future fluid injection activities (U.S. EPA 1998a).
The CCA described how mining is incorporated into the PA, including information on mining rates and probabilities, the application of institutional controls, hydraulic conductivity variations as a result of mining, and the extent of minable reserves (see the CCA, Chapter 6.0, Section 6.4.6.2.3). The DOE identified potash as the only natural resource currently being mined near the WIPP. The DOE used the EPA-specified frequency of mining and probability when considering changes in hydraulic conductivity up to 1,000 times the base hydraulic conductivity of the Culebra Dolomite Member of the Rustler Formation (hereafter referred to as Culebra). In its calculation of the potash area to be mined, the DOE considered minable reserves inside and outside the controlled area (the CCA, Appendix DEL, Section DEL.4.2.4 ).
In reviewing the DOE's compliance with 40 CFR § 194.32(b), the EPA considered whether the CCA included a detailed, accurate, and comprehensive analysis of mined resources in the WIPP area and sufficient information to demonstrate how mining probability was determined. Specifically, the EPA examined the validity of the DOE's potash reserve estimates, including the DOE's assumptions regarding potash reserve location, quality, and minable horizons. The EPA also examined the CCA to determine how hydraulic conductivity in the supra-Salado Formation units was modified to address changes that could be caused by mining over the 10,000-year regulatory period (U.S. EPA 1998a).
The EPA's review of minable reserves found that the DOE identified current minable thicknesses and horizons near the WIPP. The DOE's estimate roughly corresponds to that identified in an EPA technical memorandum (Peake 1996). The EPA recognized that this is not necessarily representative of the entire Delaware Basin, and it is conceivable that additional reserves could be mined in the WIPP area. However, speculation of this nature would extend to other horizons or reserves, which is beyond the intent of section 194.32(b). The EPA therefore concurred with the DOE's approach.
The EPA also found that the DOE assumed mined resources will be completely removed from the controlled area within the century in which mining occurs, and complete removal of mineral resources was assumed to occur only once over the regulatory time frame, in accordance with section 194.32(b). The DOE assumed that mining will be done via room and pillar or other conventional methods, and solution mining of potash will not take place because of mineralogical and economic constraints.
Finally, the EPA determined that mining was properly incorporated in PA through the application of the 1 to 1,000 multiplier for hydraulic conductivity in the calculated transmissivity field for the Culebra. The CCA, Appendix TFIELD and related documentation include information pertinent to this application of the transmissivity multiplier.
In the CCA, the DOE identified appropriate events and analyses of their effects on the disposal system, as well as the effects of existing boreholes. The EPA considered how these events affected the disposal system and whether the DOE addressed the potential for slant drilling. The EPA also examined whether the DOE addressed potentially exploitable existing leases.
The DOE concluded that oil and gas exploration and exploitation and water and potash exploration are the only human-initiated activities that need to be considered for PA (see the CCA, Chapter 6.0, Section 6.3.2). The DOE divided human-initiated activities into two categories: (1) those that have been Historic, Current, and Near-Future (HCN), and (2) those that may happen in the future after disposal (Future). Human-initiated activities included three different drilling-related intrusion scenarios used in PA based on the screening analysis, designated by the DOE as E1, E2, and E1E2 (see the CCA, Chapter 6.0, Section 6.3.2). The E1 scenario assumed penetration of a panel by a borehole drilled through the repository, which then strikes a brine pocket present in the underlying Castile Formation. The E2 scenario included all future boreholes that penetrate a panel but do not strike an underlying brine pocket within the Castile. The E1E2 scenario was defined as the occurrence of multiple boreholes that intersect a single waste panel, with at least one of the events being an E1 occurrence.
The EPA evaluated the DOE's compliance with 40 CFR § 194.32(c) and determined that the DOE had used a reasonable approach to screen human-initiated activities that might impact the repository. The EPA concluded that, based on the discussion in the CCA, Appendix SCR, the DOE considered the appropriate issues, and the technical conclusions reached by the DOE regarding screening of oil and gas exploration and extraction activities were valid (U.S. EPA 1998a).
The DOE listed FEPs eliminated from PA based on probability, and described why they were not included. The DOE used this requirement to screen out FEPs such as nuclear criticality, galvanic coupling, formation of new faults, glaciation, and impact of large meteorites.
The EPA examined the screening arguments and information in the CCA, Appendix SCR to assess the traceability of assumptions, approximations, and measures of uncertainties. The EPA examined the DOE's approach to determine whether it was well documented and adequately justified. The EPA examined assigned probabilities to determine whether they were appropriate, documented, and in accordance with EPA regulatory requirements, and examined the sufficiency of all data in terms of quantity and adequacy. In conclusion, the EPA concurred with the events and processes that were screened out by the DOE using the low-probability criterion (U.S EPA 1998a).
The CCA, Appendix SCR identified the processes and events, or sequences and combinations of processes and events, included in PA, including natural and human-initiated processes and events. The CCA, Appendix SCR provided a comprehensive analysis of all FEPs that may affect WIPP performance. In addition, the CCA, Appendix SCR and its attachments document the development of the WIPP FEPs list and describe its origin from over 1,200 FEPs identified through various international repository programs. The broad and comprehensive beginning of the WIPP FEPs list helps to assure that all potential WIPP-relevant FEPs can be properly identified. After refinement of the initial list, the DOE's FEP identification process resulted in approximately 237 FEPs that were retained for screening.
The EPA reviewed the DOE's initial FEPs list at each stage of development and review to determine whether it was comprehensive. In addition, the EPA examined information sources used by the DOE to compile the FEPs list for completeness and accuracy of technical information. The EPA concluded that the DOE identified those events and processes, and sequences or combinations of events and processes, that may occur during the regulatory time period and affect the repository. The EPA concluded that these FEPs represented those most critical in terms of affecting the disposal repository (U.S. EPA 1998a).
40 CFR § 194.32(e)(2) states that compliance applications must identify the processes, events or sequences and combinations of processes and events included in PA. To accomplish this, the DOE formulated conceptual models and scenarios that incorporated each of the FEPs screened in during the screening processes detailed in the CCA, Appendix SCR. The DOE developed scenarios to represent both undisturbed and disturbed system performance. FEPs were included into scenarios ranging from the effects of deep and shallow drilling and mining to undisturbed disposal system performance. In the CCA, Chapter 6.0, Section 6.2, Table 6-6, the DOE identified the specific locations in the CCA where information on the modeling of the individual FEP can be found.
The EPA reviewed the CCA to determine whether FEPs and subsequent scenarios were appropriately screened, adequately justified, and completely supported. In addition, the EPA examined combinations of FEPs and scenarios included in PA. The EPA concluded that the DOE used a process, the Statens Kärnkraftinspektion (SKI) list (modified to suit conditions at the WIPP site), that identified the processes, events, or sequences, or combinations of processes and events (Stenhouse, Chapman, and Sumerling 1993). As part of this process, the DOE adequately addressed and evaluated the effects of mining, deep drilling, and shallow drilling. The DOE evaluated the FEPs and sequences of FEPs through calculations, estimates of probability, and comparisons to regulatory requirements. The EPA concluded that the DOE appropriately identified, listed, and discussed the FEPs and the effects of the sequences and combinations of FEPs that result in modeled scenarios (U.S. EPA 1998a).
40 CFR § 194.32(e)(3) requires that FEPs not included in PA calculations be adequately documented and justified. The DOE identified approximately 237 FEPs in the CCA, Appendix SCR, and the CCA, Chapter 6.0, Section 6.3. For each FEP, the DOE provided a description and a generalized rationale for screening classifications. Of the 237 FEPs analyzed, 154 were screened out on the basis of regulations (SO-R), low consequence (SO-C), or probability (SO-P). The CCA, Appendix SCR included the DOE's screening rationale for each of the 237 CCA FEPs.
To verify the DOE's compliance with this section, the EPA reviewed the information in the CCA, Appendix SCR and also conducted audits to verify the proper execution of quality assurance programs for all items and activities important to the containment of waste in the repository, including items and activities related to FEPs. As a result of these EPA audits, the EPA concluded that quality assurance programs were properly executed for FEP-related items and activities, and that the DOE had demonstrated compliance with the requirements of section 194.32 (U.S. EPA 1998a).
For the Compliance Recertification Application of 2004 (CRA-2004) (U.S. DOE 2004) and the subsequent Performance Assessment Baseline Calculation, the DOE reevaluated all WIPP FEPs to determine if any had changed or if new FEPs needed to be added. This reevaluation resulted in only a few changes to the FEPs analysis. Wagner, Kirkes, and Martell (Wagner, Kirkes, and Martell 2003) concluded that of the original 237 FEPs included in the CCA, 106 did not change, 120 required updates to their FEP descriptions and/or screening arguments, and 7 of the original baseline FEPs screening decisions required a change from their original screening decision. Four of the original baseline FEPs were deleted or combined with other closely related FEPs, and two new FEPs were added to the baseline. These two FEPs were previously addressed in an existing FEP; they were separated for clarity. Therefore, for the CRA-2004, reevaluation resulted in a new FEPs baseline consisting of 235 FEPs, but did not change the CCA conceptual models or the scenarios developed for PA.
For the CRA-2004, the DOE applied the same approach that was used for the CCA to develop and screen the list of FEPs that may have an effect on the disposal system. Since the WIPP FEPs were previously evaluated and approved in the initial certification process, the EPA focused its recertification review on the FEPs that had changed since the 1998 Certification Decision (U.S. EPA 1998b). The EPA verified that the DOE's FEP development and review process was fundamentally the same as the CCA process, and verified that the DOE's reevaluation properly considered changes since the original certification decision in 1998. The EPA verified that any changes to FEP screening arguments or FEP-related discussions were reasonable, appropriate, and complete.
The EPA received one public comment related to the scope of PA. Some stakeholders proposed that karst (FEP N20) should be included in the PA conceptual model development. The EPA reevaluated karst issues raised by stakeholders from the CCA, as well as new information made available since the original certification decision. The EPA's review is discussed in the Technical Support Document for Section 194.14: Evaluation of Karst at the WIPP Site (U.S. EPA 2006a). After a thorough review, the EPA determined that karst should not be screened into the PA process.
Based on a review and evaluation of the CRA-2004 and supplemental information provided by the DOE, the EPA determined that the DOE continued to comply with the requirements for section 194.32 (U.S. EPA 2006b and U.S. EPA 2006c).
For the CRA-2009 (U.S. DOE 2009), the DOE identified all PA changes implemented since the CRA-2004 and determined their impacts to the FEPs baseline (Kirkes 2008). This assessment was very similar to the process used for the CRA-2004. The FEPs baseline was maintained according to Sandia National Laboratories Specific Procedure (SP) 9-4, Performing FEPS Baseline Impact Assessments for Planned and Unplanned Changes (Kirkes 2006). Any changes that affect the FEPs baseline were detailed in Appendix SCR-2009. As a result of the reevaluation, 35 FEPs were updated with new information, one screening argument was changed to correct errors discovered during review, and the screening decision for one FEP was changed from SO-R to SO-C. This latter change had no impact on PA calculations because the FEP continued to be excluded from PA, albeit via different screening rationale. Finally, there were 10 FEPs that were split into 20 similar but more specific FEPs. For the CRA-2009, there were 70 Natural FEPs, 61 Human-initiated EPs, and 114 Waste and Repository FEPs, resulting in 245 WIPP FEPs.
For the CRA-2009, the EPA reviewed and verified the process that the DOE used to determine the set of FEPs that might have an effect on the disposal system. This process was essentially the same as used for the CCA and the CRA-2004, and resulted in 245 FEPs retained for evaluation in the CRA-2009. Since it had previously evaluated and approved this process, the EPA focused its 2009 recertification review on the FEPs that have changed since the 2004 Recertification Decision. The EPA verified that any changes to FEP screening arguments or FEP-related discussions were reasonable, appropriate and complete, and determined that the DOE was in compliance with the requirements of 40 CFR § 194.32. The EPA received one public comment stating that karst (FEP N20) should be included in PA conceptual models. The EPA concurred with the DOE's position that karst at the WIPP should not be included in performance calculations (U.S. EPA 2010). Based on a review and evaluation of the CRA-2009 and supplemental information provided by the DOE, the EPA determined that the DOE continued to comply with the requirements of section 194.32 (U.S. EPA 2010).
For the CRA-2014, changes to the WIPP baseline were identified and evaluated to determine their impact upon the WIPP FEPs baseline (Kirkes 2013a). The FEPs baseline continues to be maintained according to Sandia National Laboratories SP 9-4, Performing FEPS Baseline Impact Assessments for Planned and Unplanned Changes (Kirkes 2013b)  . This reevaluation process is the same process that was used for the CRA-2004 and CRA-2009 FEP assessments. For the CRA-2014, there are 70 Natural FEPs, 61 Human-initiated EPs, and 114 Waste and Repository FEPs, resulting in 245 WIPP FEPs. These are the same 245 FEPs retained for screening in the CRA-2009. There have been no additions or deletions. However, 61 of these FEPs have been updated in some way. The current FEPs baseline is presented in Appendix SCR-2014. Table 32-1 lists the CRA-2014 FEPs and their screening decisions, and summarizes any changes to related information since the CRA-2009.
UP in the Culebra and Dewey Lake; SO-C-Beneficial in the disposal room, shaft seals, panel closures, and other geologic units.
d FEPs in this column that are not separated by rows represent FEPs that are similar in nature and are discussed and screened as a common group.
The requirements of section 194.32(b) specify assumptions regarding the implementation of mining in PA calculations. The PA modeling system used for the mining scenario is similar to that developed for the undisturbed repository scenario, but with a modified Culebra transmissivity field in the controlled area to account for the mining effects. Implementation of the mining scenario has not changed since the CRA-2009 Performance Assessment Baseline Calculation. Details regarding how mining processes are represented in PA models are described in Appendix PA-2014, Section PA-2.3.2.2.1 , and Appendix MASS-2014, Section MASS-15.1. FEPs related to the presence of resources are described and considered in Appendix SCR-2014, Section SCR-5.0.
Section 194.32(c) provides specific time frames for the evaluation of activities that may affect the disposal system. This requirement focuses on activities that have occurred in the past, are occurring, or are expected to occur in the near future. The DOE classifies this time frame as HCN. Because section 194.32(e)(1) requires the evaluation of human-initiated EPs during the regulatory time period, the DOE evaluates human-initiated FEPs for the period of time spanning from closure of the repository to 10,000 years into the future as well (Future) (see human-initiated EPs in Table 32-1). Human-initiated EPs are described and considered for both the HCN and Future time frames in Appendix SCR-2014, Section SCR-5.0. Therefore, the DOE is in compliance with the requirements of section 194.32(c).
Low-probability events can be excluded on the basis of the criterion provided in 40 CFR § 194.32(d), which states, "performance assessments need not consider processes and events that have less than one chance in 10,000 of occurring over 10,000 years." In practice, for most FEPs screened out on the basis of low probability of occurrence, it has not been possible to estimate a meaningful quantitative probability. In the absence of quantitative probability estimates, a qualitative argument was used. One FEP has been added to this screening classification since the CRA-2009. W115 Chemical Degradation of Panel Closures has been reclassified from UP to SO-P due to the newly designed panel closure system and its run-of-mine salt composition. Therefore, there are 22 FEPs screened using the SO-P criterion for the CRA-2014. FEPs screened out on the basis of low probability are listed in Table 32-2.
The requirements in section 194.32(e) are met by the analyses of FEPs as documented in Appendix SCR-2014. Table 32-1 lists the CRA-2014 FEPs and summarizes any changes to screening decisions and arguments.
Section 194.32, "Scope of Performance Assessment," requires the identification, selection, screening, and incorporation of all significant processes and events into PA. The DOE has taken a comprehensive approach in meeting the requirements of the section as documented here and in Appendix SCR-2014. The process used is consistent with evaluations of WIPP FEPs in past compliance applications. Any new information that relates to WIPP FEPs is identified and incorporated into PA as appropriate.
In summary, based on the information in Section 32.8, the DOE continues to comply with all the requirements in section 194.32 for the CRA-2014.
 Human-initiated FEPs are screened for both the HCN and Future time periods (i.e., 194.32(c) and 194.32(e)(1)).
 Note: Revision 3 of SP 9-4 was developed in response to EPA comments on the CRA-2009 Section 32, which identified inconsistencies in the documentation requirements as specified in SP 9-4 Revision 2.

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