5
Candidate Area Identification

The purpose of this chapter is to review and analyze the Candidate Area Identification (CAI) screening process (Figure 3.1), which is described in the December 1988 Siting Commission's Candidate Area Identification Report (CAIR). The first part of this chapter contains a brief description of the CAI screening process, and the second part contains the committee's assessment of the process and results.

The Siting Commission's objective in this step of the screening process was to rescreen the 69.5 percent of land not excluded by the Statewide Exclusionary Screening (SES; Chapter 4) process in order to identify 10 areas for detailed investigation. Although the sizes of the candidate areas were never formally defined by the Siting Commission, it was intended that each area might be large enough to contain a number of potential repository sites. The average size of the areas selected in this process was approximately 110 square miles (approximately 260 square kilometers) that together constituted some 2 percent of the area of the state.

The Siting Commission's objectives in this step of the screening process were to

  • apply exclusionary criteria that required some qualification or interpretation of regulatory requirements;
  • apply exclusionary and preference criteria for conditions without strict regulatory or legal definitions of boundaries;
  • apply criteria for which data were available for all areas under consideration; and
  • identify those areas of the state having the greatest potential for sites for low-level radioactive waste (LLRW) disposal.

CAI actually involved three discrete screening activities, each of which involved the application of a different set of preference and (or) exclusionary criteria. The three activities were the following (Figure 5.1):



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--> 5 Candidate Area Identification The purpose of this chapter is to review and analyze the Candidate Area Identification (CAI) screening process (Figure 3.1), which is described in the December 1988 Siting Commission's Candidate Area Identification Report (CAIR). The first part of this chapter contains a brief description of the CAI screening process, and the second part contains the committee's assessment of the process and results. The Siting Commission's objective in this step of the screening process was to rescreen the 69.5 percent of land not excluded by the Statewide Exclusionary Screening (SES; Chapter 4) process in order to identify 10 areas for detailed investigation. Although the sizes of the candidate areas were never formally defined by the Siting Commission, it was intended that each area might be large enough to contain a number of potential repository sites. The average size of the areas selected in this process was approximately 110 square miles (approximately 260 square kilometers) that together constituted some 2 percent of the area of the state. The Siting Commission's objectives in this step of the screening process were to apply exclusionary criteria that required some qualification or interpretation of regulatory requirements; apply exclusionary and preference criteria for conditions without strict regulatory or legal definitions of boundaries; apply criteria for which data were available for all areas under consideration; and identify those areas of the state having the greatest potential for sites for low-level radioactive waste (LLRW) disposal. CAI actually involved three discrete screening activities, each of which involved the application of a different set of preference and (or) exclusionary criteria. The three activities were the following (Figure 5.1):

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--> Figure 5.1 Flowchart for the CAI screening process. Exclusionary Screening. Lands remaining after SES (see Chapter 4) were screened further using nine exclusionary criteria, some of which were applied at a finer scale than in SES. After this step, approximately 40 percent of the state had been removed from consideration for an LLRW disposal facility. Initial Preference Screening. The remaining lands were scored using 14 preference criteria. A cutoff score was imposed, and the 30 highest-scoring areas were selected for further analysis. Comparative Preference Analysis. These 30 areas were rescreened using a set of 13 preference and 5 exclusionary criteria. Ten candidate areas were selected for further study. Each of these steps is described briefly in the following sections.

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--> Exclusionary Screening The methodology used by the Siting Commission for this Exclusionary Screening step was much like that for SES (Chapter 4). The nine criteria were applied using data from existing databases and published maps at a scale of 1:250,000 (the scale used in SES), as well as at other scales ranging from 1:500,000 to 1:24,000. Areas that did not satisfy all of the exclusionary criteria were eliminated from further consideration. Table 5.1 lists the exclusionary criteria used in this screening process. Criterion 4 (existing mine exclusion) was applied only to sites under consideration for a mine disposal facility. Five of the exclusionary criteria (11, 32, 36, 38, and 41) had been applied during SES but at a much coarser scale. In addition, the population density exclusion (Criterion 32) was applied to all incorporated areas of the state, and all federal, state, and Indian lands were excluded (Criteria 36, 38, and 41). The Geographic Information System (GIS) was used extensively during this and other CAI screening steps, and its analytical capabilities were utilized for the first time. The state was subdivided into cells, each having an area of 1 square mile (640 acres), for purposes of screening. At this cell size there are approximately 50,000 cells in the state, and 35,000 cells in the area of the state remaining after SES, to which the GIS was applied. If an excluded feature was contained in any part of the cell, the entire cell was removed from consideration. This screening eliminated about 9.2 percent of the area of the state and 13.2 percent of the lands remaining after SES (Table 5.1). Initial Preference Screening The remaining lands of the state were subjected to Initial Preference Screening in order to identify 30 potential candidate areas. The Siting Commission used the GIS to screen the nonexcluded areas of the state using the 1-square-mile grid cells employed in the Exclusionary Screening step of CAI. The following methodology was used (Figure 5.2):

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--> TABLE 5.1 Areas Excluded by the Exclusionary Screening Step of CAI Criterion (Number) Acres Excluded Percentage of State Excludeda Existing mine exclusion (4) 9,600 < 0.1 Ground water hydrologyb (11) 1,531,301 4.8 Surface water bodies (15) 1,059,840 3.3 Air quality nonattainment (26) 1,738,880 5.5 Population densityb (32) 571,258 1.8 Federally protected landsb (36) 139,520 0.4 State protected landsb (38) 1,104,381 3.5 Indian landsb (41) 66,845 0.2 West Valley sitec (46) 3,400 < 0.1 Totald 2,909,639 9.2 a Percentages computed using 31,728,640 acres as the area of the state of New York. b Also applied during SES but at a coarser scale. c The 1986 State Act specifically excluded West Valley from consideration as an LLRW disposal facility. d Total is less than the sum because of mutually exclusive conditions. Source: Excluded Areas Report (Siting Commission, 1993). If the feature of interest (e.g., an aquifer) was contained in any part of the cell, the entire cell was marked as containing that feature. Each cell was scored numerically for each of the 14 preference criteria (Table 5.2). A score for each criterion was obtained by multiplying the scaling factor assigned to each cell by the weight for the criterion.1 A composite score was determined for each cell by summing the scores for all of the criteria for that cell. 1   See Chapter 3 for a discussion of the numerical scoring system.

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--> Figure 5.2 Conceptual illustration of scoring system using the GIS. The  example shown is hypothetical, and cell size is not defined.

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--> TABLE 5.2 Preference Criteria Applied During Initial Preference Screening Preference Criterion Description 2 Seismic hazards 5 Geologic units 10 Distance from oil and gas fields 12 Primary and principal aquifers 13 Surface water features 14 Unconsolidated stratigraphic units 22 Best usage of surface waters 23 Annual precipitation 24 Chronic severe weather 33 Low population densities 37 Distance from federal lands 39 Distance from state lands 42 Distance from Indian lands 51 Proximity to waste generators The Siting Commission compared the cell composite scores in order to identify potential candidate areas. The commission found that composite scores for cells were similar throughout the majority of the towns,2 and for this reason it compared composite scores on a town-by-town basis and defined potential candidate areas generally along town lines. Only areas containing towns with a large number of composite scores exceeding the cutoff score of 4,400 points (out of a possible 5,000 points) were considered for selection as a potential candidate area. A 2   A town is the smallest statewide political subdivision in New York. Towns have defined boundaries and vary in size. All geographic points in the state fall within the boundaries of either a town or a city.

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--> town whose composite scores ranged mostly between 4,400 and 4,700, and that was contiguous with another town also scoring above 4,400, could be included with the other as a single potential candidate area. A town with a large portion of cell composite scores exceeding 4,700 points could be considered a potential candidate area by itself. A cutoff score was used because the scoring system did not produce a small number of high-scoring (i.e., clearly preferable) areas. Approximately 5 percent of the area of the state had a composite score of 4,400 or greater. Lowering the cutoff to just 4,300 points would have increased this area to about 8 percent (Figure 5.3). The Siting Commission stated (CAIR, p. 3-5) that a score of 4,400 points was chosen because it ''enabled a substantial reduction of the remaining area of the State under consideration and yielded a manageable number of discrete candidate areas.'' As noted previously, the Siting Commission selected 30 potential candidate areas in this step. Figure 5.3 Distribution of composite scores for Initial Preference Screening  across the area of New York State. The cutoff score was 4,400 out of a total of  5,000 points. The percentages of area of the state total approximately 60%.  The other 40% of the state was excluded during previous screening steps.

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--> Comparative Preference Analysis Comparative Preference Analysis involved the application of 5 exclusionary and 13 preference criteria (Table 5.3) to rescreen the 30 potential candidate areas. According to the Siting Plan, these criteria were not to be applied until Potential Sites Identification (PSI) screening (Chapter 6), in part because they required site-specific information. Moreover, these criteria were only a subset of the criteria to be employed during PSI screening. In applying these criteria at this earlier point in the screening process, the Siting Commission noted (CAIR, pp. 7-1, 7-2): Because additional criteria will be introduced in the next step of the site selection process, the Commission deemed it appropriate to seek a preview of the conditions likely to exist in the potential candidate areas for some of these additional criteria. . . . The assessments of these criteria were based on limited examinations of the areas, using readily available data sources. In some cases, the data sources were only indicators of the conditions being considered, rather than a precise measure of the actual condition. In other cases, approximations of a range of conditions had to be made, based on professional judgments of technical experts. In addition, in some cases, only the presence or absence of a feature could be noted. Ten candidate areas were selected on the basis of qualitative screening using these criteria. For each of the criteria, the candidate areas were rated between "most favorable" and "least favorable." The purpose of this screening was to establish the extent of the least favorable conditions and, if possible, to redraw the candidate area boundaries to exclude cells with such conditions. The Siting Commission then assigned an "overall favorability" rating to each of the 30 potential candidate areas. The basis for these rankings was justified with the following statement (CAIR, p. 8-4):

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--> TABLE 5.3 Criteria Applied During Comparative Preference Analysis Screening Criterion Description 1 Geologic complexity 3 Subsurface dissolution 4a,b Existing mine exclusion 5b Geologic units 6a Reforestation areas 12 Primary and principal aquifers 17a,c Wetlands exclusion 18c Distance from wetlands 19 Drainage 20 Erosion 21 Flooding 22 Best usage of surface waters 30 Other radionuclide sources 34 Highly populated places 44a Mineral soil groups 47 Transportation access 57a,d Historic places 59d Distance from historical/cultural resources a Exclusionary criterion. b Applied for new and existing mine disposal only. c These criteria were applied together. d These criteria were applied together.

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--> Based on the results of the comparative and the confirmatory evaluations, the potential candidate areas were given evaluations with regard to their overall favorability for containing technically superior sites. All of the "more favorable" and half of the "favorable" areas were included in the list of 10 candidate areas (Figure 5.4). The process used to select these areas, particularly the processes used to select half of the favorable sites, was not well documented in the CAIR. As part of Comparative Preference Analysis, the Siting Commission carried out a limited sensitivity analysis to examine the impact of changing preferences and weights on the selection of the 10 candidate areas. For this exercise, the 30 areas selected during Initial Preference Screening were rescored using the scenarios shown in Table 5.4. The Siting Commission found that although the scores changed somewhat for these scenarios, "most of the areas continued to display favorability scores above the cutoff level of 4,400 in each case" (CAIR, p. 5-4). Subsequently, the Siting Commission examined the change in score for each of the 1-mile-square cells within the candidate areas. For two of the scenarios (Scenarios 4 and 5 involving Criterion 51, proximity to waste generators), cells in five candidate areas fell below the cutoff. Despite this result, the Siting Commission decided not to change the screening results. It concluded (CAIR, p. 5-4): This factor [Criterion 51—proximity to waste generators] is not deemed to be of overriding significance, considering that New York waste generators are currently shipping their wastes to much more distant disposal sites out of State. The consistency of results from the sensitivity studies provides assurance of the reasonableness of the weighting factors used by the Commission in identifying the potential candidate areas. Notably, 3 of the areas that fell below the cutoff in this sensitivity analysis were among the 10 candidate areas, and sites from 2 of these areas were selected in the next step of the screening process (Chapter 6).

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--> Figure 5.4 Map of New York State showing the 10 candidate areas. Source: CAIR.

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--> (non-bedrock) geologic deposits, which: (1) receives substantial recharge from the overlying land surface; and (2) is presently utilized as a major source of water for public water supply. . . . (6 NYCRR 3 82.2(tt)) By comparison, principal aquifers referred to . . . unconsolidated (non-bedrock) geologic deposits identified by the department which: (1) receive substantial recharge from the overlying land surface; (2) are known to be highly productive or whose geology suggests a potentially abundant source of water; and (3) are not presently used as a major source of water for public water supply. (6 NYCRR 382.2(uu)) The Siting Commission had no discretion in the application of Criterion 11, because it was specified by regulation. Moreover, the commission was required to perform the screening using the primary and principal aquifers identified by the DEC. Criterion 12, on the other hand, allowed the Siting Commission to select areas distant from any hydrogeologic unit that fit the definition of principal aquifers,5 not just principal aquifers that had been identified previously by the DEC. During CAI screening, many of the counties hosting candidate areas provided evidence to the Siting Commission that their ground water resources were comparable to other principal aquifers in New York State. There were no provisions in the Siting Plan for the Siting Commission to examine these data at this stage of screening. The committee believes there should have been provisions to accommodate contributed data on aquifer characteristics, well performance, and water usage on the scale of the 1-mile-square cells used in CAI screening, 5   It should be noted that the DEC definitions of primary and principal aquifers do not include aquifers that may be found in fractured bedrock (e.g., granite, shale, or sandstone), even though these may be locally important water supplies for farms and small communities.

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--> particularly in light of the fact that the Siting Commission used outside data to reclassify two aquifers in the Siting Plan.6 Criteria 12, 13, and 18—Buffers from Water Resources These performance-oriented criteria express a preference for sites that are greater than 1 mile from a primary or principal aquifer, a significant surface water feature, or a wetland. In response to committee questions on this issue (Appendix F), the Siting Commission indicated that the 1-mile standard was based on the assumption that ground water flow rates would average about 10 feet per year. Consequently, about 500 years would be required for ground water to travel 1 mile, which would satisfy the structural stability requirements for Class C wastes. The Siting Commission also indicated that the scaling for these and other distance criteria was based largely on qualitative assessments: All of the scaling factors are intended to simply guide the site screening process and none is an absolute measure of the performance of a site in protecting public health and safety. The committee acknowledges the desirability of buffers to protect water resources. The committee notes, however, that to be most effective, such buffers must be based on local flow conditions, which depend on factors such as slope, soil type, subsurface structure, and geology. Such data were not available to the Siting Commission for all parts of the state at this stage of screening; consequently, the evaluation of these criteria should have been deferred to a later stage in the screening process. Criterion 22—Best Usage of Surface Waters Prefer areas where location of a disposal facility is unlikely to impair the best usage of surface waters, as measured against water quality standards. 6   Based on public comments on the draft Siting Plan, the Siting Commission reviewed data on other aquifers and classified the aquifers at Tug Hill and Cattaraugas Creek as equivalent to principal aquifers.

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--> Criterion 22 defines the favorability of a site relative to the current or future use of surface waters, particularly how that usage might be affected by siting an LLRW disposal facility. Scaling factors were assigned based on numerical buffer zones around surface water intakes for community water systems. For example, for intakes from water bodies less than 20 square miles in area, a site falling outside a 2-mile-wide buffer zone surrounding the entire water body would be assigned a scaling factor of 3. As noted above, the committee acknowledges the desirability of buffers to protect water resources. To be most effective, however, such buffers must be based on local flow conditions, which depend on site-specific conditions. Because such data were not available to the Siting Commission for all parts of the state at this stage of screening, the evaluation of this criterion should have been deferred to a later stage in the screening process. Criterion 26—Air Quality Nonattainment Exclude areas that are within pollutant nonattainment areas. The committee questions whether this exclusionary criterion is necessary because it appears to have no basis in legislation or existing regulation. The Siting Plan notes that development of a facility in an air quality nonattainment area could preclude the future use of on-site incineration as a waste processing method. While the ability to locate an incinerator at the disposal site would provide flexibility in the waste management system, in the committee's judgment it is not a necessary condition for an LLRW disposal facility. The committee notes that air quality could be affected during construction of the facility but that engineering controls could be utilized to minimize adverse impacts. Indeed, construction activities are conducted routinely in air quality nonattainment areas. The committee also notes that because air quality nonattainment areas do not generally coincide with rural areas, this criterion is inherently biased against rural areas (i.e., rural areas are less likely to be excluded on the basis of this criterion). Most of the land excluded by this

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--> criterion overlapped with areas already excluded by SES; however, the criterion did exclude an additional 5 percent of the state. Very little of this land was rural. In the committee's judgment, if the criterion was to be included at all, it should have been included as a preference criterion. Initial and Comparative Preference Screening As noted previously, the Siting Commission chose a cutoff score of 4,400 points in order to select the 30 candidate areas during Initial Preference Screening. In the committee's judgment, there are two problems with the Siting Commission's use of arbitrary cutoff scores to select a small number of sites from a relatively large area of the state. First, as will be shown by the following sensitivity analysis, there is not a good correlation between the numerical score and the likely performance7 of a site as an LLRW repository, owing to the way in which exclusionary and preference criteria were applied in the screening process. Thus, potentially suitable sites may have been screened out prematurely, and less suitable sites may have been retained. Second, problems were also created by the decision to use the criteria to screen out all but a few sites in the state. Even if there were a reasonably good overall correlation between numerical score and site suitability, the correlation across a truncated range of scores (e.g., over a range of a few hundred points, say from 4,000 to 4,500 points) may be poor, and there may be little if any correlation within the highly truncated range of scores when only the few top-scoring sites are considered. The 10 candidate areas identified through Comparative Preference Analysis screening were not the highest-scoring areas 7   The Siting Commission's objective in screening the state was to select a site that would meet the requirements of federal and state regulations for a land disposal facility. The emphasis of the regulations is on selecting a site capable of preventing the off-site movement of radionuclides released from an LLRW disposal facility. Since the primary release pathway is through the surface and shallow subsurface environment, state regulations focus on the geologic and hydrologic factors that control the movement of radionuclides introduced into these settings. The committee uses the term performance to describe the degree to which these geologic and hydrologic factors contribute to the integrity and stability of the repository and the prevention of radionuclide release to the accessible environment.

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--> identified during Initial Preference Screening.8 Indeed, it is unlikely that the same 10 candidate areas would have been selected had the entire set of 43 preference criteria (see Appendix I) been applied to all of the nonexcluded lands. In other words, the screening results are not unique—the areas selected depend on the sequence of screening steps and the mix of criteria applied at each step. This is a fundamental shortcoming of the screening process. Although a limited sensitivity analysis was undertaken by the Siting Commission, it was poorly documented in the CAIR, and it had a number of serious shortcomings. The analysis tested the sensitivity of scoring only for the 30 areas selected during Initial Preference Screening. It did not address whether scores for other areas of the state would change significantly if the criteria were applied in a different order. It appears to the committee that the sensitivity analysis may have been used as a means to justify the candidate areas selected, rather than as an unbiased effort to evaluate the process prior to its application. The limitations of the Siting Commission's sensitivity analysis can be demonstrated through a simple exercise that compares scores for several hypothetical scenarios for Initial Preference Screening (Table 5.5). Despite its simplicity, this exercise provides several components of a sensitivity analysis that would have been extremely valuable in planning the screening process. Table 5.5 divides the 14 preference criteria used in Initial Preference Screening into three groups: Preference criteria based on known quantities—readily available data having relatively uniform quality across the state. Such data include average annual precipitation; locations of federal, state, and Indian lands; proximity to waste generators; and distance from surface water features. Most of these criteria address nonperformance factors. That is, they are not critical issues in determining the capability of a site to function as an LLRW disposal site. Preference criteria based on uncertain quantities—data of unknown or uneven accuracy or completeness. Most of these preference criteria address the likely performance of the site as a host for an LLRW repository. These include geology, proximity to aquifers, best usage of 8   The 10 candidate areas ranked 1, 8, 9, 10, 11, 20, 21, 24, 25, and 27 out of 30.

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--> surface waters, distance to active and abandoned oil and gas fields, and the probability of seismic activity. In the scoring system used by the Siting Commission (Chapter 3), these criteria tend to give high scores to areas that lack data. Preference criteria based on population quantities—in this case, demographic information. These quantities can be measured readily, but they are sensitive to such details as placement of boundaries and annexation. The committee applied these three sets of preference criteria to seven hypothetical scenarios to test the effects of various scaling schemes; the results are shown at the bottom of Table 5.5. Scenario 1 represents the "base case" in which all of the preference criteria are assigned a scaling factor of unity (least favorable). The total score9 is 1,000 points, the minimum score an area can receive. The effect of population density on scoring is isolated in Scenario 2. Scenario 3 provides a test of the sensitivity of scoring to the presence of 1-mile buffer zones for federal, state, and Indian lands. Scenarios 4, 5, 6, and 7 assess the influence of preference criteria scored with "uncertain" data, as explained in the footnotes in Table 5.5. A significant result of this sensitivity analysis is that none of the scenarios give scores that exceed the cutoff value of 4,400 points. This is a positive attribute of the screening process because it indicates that favorable scores for a large number of criteria are required to qualify a site. The high scores shown in Table 5.5 for Scenarios 4, 5, 6, and 7 indicate that the preference criteria analyzed using uncertain data exert a strong control on scoring. Scenario 4 demonstrates, for example, that about 2,700 of the necessary 4,400 points can be attributed to highly favorable scores on these criteria alone. Because these criteria address performance factors for an LLRW facility, an area's scores may be 9   As noted in Chapter 3, the total score is equal to the sum of the scaling factors for each criterion multiplied by their respective weights.

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--> TABLE 5.5 Initial Preference Screening Sensitivity Analysis     Scaling Factora,b Category (Criterion Number) Criterion Weighta Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 Scenario 6 Scenario 7 Known Quantities Surface water features (13) 107 1 1 5 1 1 5 5 Annual precipitation (23) 53 1 1 1 1 1 1 1 Chronic severe weather (24) 53 1 1 1 1 1 1 1 Distance from federal lands (37) 27 1 1 5 1 1 5 5 Distance from state lands (39) 27 1 1 5 1 1 5 5 Distance from Indian lands (42) 27 1 1 5 1 1 5 5 Proximity to waste generators (51) 53 1 1 1 1 1 1 1 Subtotal 347               Uncertain Quantities Geology (5, 14) 200 1 1 1 5 5 5 5 Distance from oil and gas fields (10) 53 1 1 1 5 5 5 5

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-->   Scaling Factora,b Category (Criterion Number) Criterion Weighta Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 Scenario 6 Scenario 7 Primary and principal aquifers (12) 147 1 1 1 5 5 5 5 Best usage of surface waters (22) 80 1 1 1 5 5 5 5 Seismic hazards (2) 53 1 1 1 5 5 5 5 Subtotal 533               Population Quantities Low population densities (33) 120 1 5 5 1 5 1 5 Subtotal 120               Total 1,000 1,000 1,480 2,232 3,132 3,612 3,884 4,364 a See Chapter 3 for an explanation of these quantities. b Scenario 1: Least favorable [scaling factor (sf) = 1] for all criteria. Scenario 2: Most favorable (sf = 5) for low population densities. Scenario 3: Most favorable (sf = 5) for low population densities, distance from federal, state, and Indian lands, and surface water features. Scenario 4: Most favorable (sf = 5) for all "uncertain quantities." Scenario 5: Most favorable (sf = 5) for all "uncertain quantities" and low population densities. Scenario 6: Most favorable (sf = 5) for all "uncertain quantities," distance from federal, state, and Indian lands, and surface water features. Scenario 7: Most favorable (sf = 5) for all "uncertain quantities," low population densities, distance from federal, state, and Indian lands, and surface water features.

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--> correlated weakly with the potential performance of a facility located in that area. The results for Scenario 7 illustrate the influence of a poorly designed criterion on scoring. The area in Scenario 7 had the most favorable performance and population scores, yet it scored just below the cutoff. If the annual precipitation for this area was decreased by a small amount (e.g., from 50 to 49 inches per year), the score for Criterion 23 would have increased by 106 points, and the total score would have exceeded the cutoff. This example suggests that insignificant performance or licensing factors could have played a significant role in the selection of candidate areas, and it further supports the committee's conclusion that preference scores are very subjective and may not have been a strong indicator of technical suitability of a site for an LLRW disposal facility. Summary The focus of this chapter is the CAI step of the screening process. The objective of this step was to screen the 69.5 percent of state land remaining after SES to identify 10 candidate areas, each with an average size of about 110 square miles (approximately 260 square kilometers), that together constituted about 2 percent of the area of the state. The committee analyzed the exclusionary and preference criteria used in Exclusionary Screening and Initial Preference Screening (Tables 5.1, 5.2) and the screening process itself. The committee's findings are summarized in the following sections. Screening Criteria Various combinations of the exclusionary and preference criteria were applied during CAI screening. The committee identified problems with several of these criteria, as noted below (see also Chapter 6): Criterion 2—seismic hazards—should have included an exclusionary criterion for active faulting through a site in addition to the

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--> preference criterion for areas of lower seismic hazard based on the probabilistic seismic hazard maps. This exclusionary criterion should have been applied during the site studies phase of screening (see Figure 3.1). The scope of Criterion 4—existing mine exclusion—was essentially broadened by the Siting Commission to exclude all existing mines, regardless of their depth below the surface. Although there are sound technical reasons to exclude existing mines, due to their inadequate design for an LLRW disposal facility, the Siting Commission's justification—geologic complexity—could not be properly evaluated using data available during CAI screening. Criteria 11 and 12—protection of ground water resources—The application of Criterion 11 was consistent with DEC regulations. In applying Criterion 12, however, the Siting Commission should have made provisions to accommodate contributed data on aquifer characteristics, well performance, and water usage on the scale of the 1-mile-square cells used in CAI screening. Criteria 12, 13, and 18—buffers from water resources—and Criterion 22—best usage of surface waters—The committee notes that buffers are desirable but should be based on local flow conditions, data for which were not available for all parts of the state at this stage of screening. The evaluation of these criteria should have been deferred to a later stage in the screening process. Criterion 26—air quality nonattainment—appears to have no basis in legislation or regulation and should have been designated as a preference criterion. Screening Process CAI screening comprised the following three discrete activities: (1) Exclusionary Screening, (2) Initial Preference Screening, and (3) Comparative Preference Analysis. The committee identified problems with the following aspects of the screening process: The Siting Commission's use of an arbitrary cutoff score for Initial Preference Screening is not justified because there is not a strong

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--> correlation between the numerical score and the likely performance of the area as an LLRW repository, especially when only a few sites are selected from a large area of the state. The results of screening are nonunique: the candidate areas selected depend to a great extent on the sequence of screening steps and the combination of criteria applied at each step, rather than the likely performance of the site. The sensitivity analysis performed by the Siting Commission was documented poorly and had a number of technical shortcomings. The analysis was incomplete, and it was applied to only 30 areas of the state. The committee performed its own sensitivity analysis of the 14 preference criteria used in Initial Preference Screening. Based on this analysis, the committee made the following observations: A site must be favorable for a relatively large number of criteria in order to exceed the cutoff score, which is a positive attribute of the screening process. Preference criteria scored using data of unknown or uneven accuracy and completeness exerted a strong control on scoring and biased results toward favoring regions that lacked data. Because these criteria address performance factors for an LLRW repository, and because the data are so uncertain, the site scores may be correlated only weakly with the potential performance of the sites.