Regional Flow in the Rustler Formation
Modeling the paths and rates of transport of radionuclides in groundwater entails many parameters, known or approximated. If the PA model was grossly correct, if regional flow based on current hydraulic heads in the Culebra was all that mattered, the DOE claim that the Rustler is a barrier to contaminant transport might be justified.
The facts reveal the Rustler to be a much more complex aquifer. The topography slopes gently westerly towards Nash Draw, which wraps around the WIPP site (Figure 5). Nash Draw is 20 miles long, bounded on the east by a ragged scarp called Livingston Ridge. Dissolution of the Salado salt at the base of the Rustler has produced a brine aquifer beneath Nash Draw. But the Rustler mainly discharges at higher levels and to the surface in the vicinity of the salt pan, Laguna Grande, where it evaporates, at least in today's climatic setting (Phillips, 1987). The lake bottom is a deposit of at least 55 ft. of fine gypsum, attesting to a long-term anhydrite source, distinct from the sodium chloride of Salado origin discharging to the Pecos River via the brine aquifer (Phillips, 1987). Phillips documented the ephemeral nature of discharge from a lake north of Laguna Grande called Laguna Pequena (W/NW Sec. 3, T23S, R29E), recording a flow of over 100,000 gallons per minute into Laguna Grande on September 5, 1984 after a record rainfall event stimulated spring flow. There was no surface inflow to Laguna Pequena, and the outflow diminished rapidly after the measurement (Phillips, 2001). Phillips (1987, pp. 244-248) makes a convincing geochemical argument for a Rustler source of most water discharging to Laguna Pequena and Laguna Grande, which must be the long-term destination for any WIPP-site groundwaters.
The DOE model directs Culebra flow paths southward to Malaga Bend, a distant discharge area on the Pecos River. Had they incorporated the low hydraulic heads at WIPP-29 (2968 ft.) and Laguna Grande (2950 ft.), modeled paths would have turned west to Nash Draw (Phillips and Snow, 1998, p. A-8). Computed travel times through the Culebra would have been much shorter if model heads had been realistically represented.
Another significant and erroneous assumption used in PA is that the Culebra dolomite is the only aquifer of concern for radionuclide transport. Drill holes through the Rustler encountered mainly anhydrite, a dense, hard, impermeable rock in its intact form. Thus the Magenta and Culebra dolomites were considered the only persistent aquifers that could be tested and characterized. (See Figure 3). In one WIPP shaft there is a solution-enlarged vertical fracture across the brittle anhydrite of the Unnamed Lower Member (below the Culebra) (Figure 8), so the dolomites cannot be confined. Karst channeling must have occurred at the top of the Salado salt directly above the repository, and must be presumed locally present. If not now plugged with residuum, a fracture of such dimensions could convey hundreds of gallons per minute. At various levels in the Rustler and Dewey Lake formations there may be similar dissolution conduits not usually intercepted by vertical drillholes. Thus, the simplistic, two-dimensional PA model of confined flow in the Culebra dolomite fails to characterize the entire Rustler. A tiny fraction of the formation's volume, as cave passages, may occasionally convey the preponderant fraction of the discharge, at great rates unrepresented by DOE's modeling. If DOE had fully characterized Culebra fracture flow properties by slant- hole coring, dissolution conduits would also have been found and described, and by necessity, modeled.
Tests have revealed such a great range of transmissivity (hydraulic conductivity times aquifer thickness) near wells completed in the Culebra that the degree of channeling must be the main variable across the site. Transmissivity increases westward by five to six orders of magnitude (Phillips and Snow, 1998, p A-3). Of 42 wells tested, high measurements were reported at WIPP-13, H-6, P-14, H-11, DOE-1 and DOE-2 (Figure 5). The observed irregular increase of transmissivity from east to west reflects a systematic increase in the dissolution of fracture fillings, the coalescence of smaller channels into larger conduits, and the development of cross-connecting fractures and channels to other Rustler strata (Hill, 1999, Neill, et. al., 1998). Since pumping tests in the Culebra produce greatly different responses at adjacent observation wells, the conservative approach to modeling would be to utilize at each location the highest measured transmissivity. Instead, DOE has arbitrarily assumed, at wells within 1.5 miles of the center of the WIPP site, transmissivity values that are one to two orders of magnitude smaller than the highest values revealed by the hydrologic tests (Phillips and Snow, 1998, p. A-3). The consequence is that computed travel times across the first 1.5 miles are exaggerated by similar magnitudes.
Evidence of Karst
The strongest direct evidence of a saturated karst system that will influence flows from WIPP was the penetration of five caverns below the sinkhole at WIPP-33, located about 2600 ft. west of the WIPP site (See Figure 5). Those caverns totaled 29.5 ft. in height, occurring in the Dewey Lake Red Beds, and in the Forty-Niner and Magenta members of the Rustler (Sandia Labs, 1981, Phillips and Snow, 1998). The WIPP-33 sinkhole is the most westerly of four in a chain aligned eastwards 2450 ft. to within 1000 ft. of the WIPP site boundary. It can be surmised that an extensive karst conduit underlies the chain. A similar chain of nine sinkholes is aligned E-W just north of the WIPP site boundary. There the WIPP-14 drillhole revealed 74 ft. of residual clay, much gypsum, but no caves, perhaps because the hole was drilled eccentric to the sinkhole formed over collapsed caverns. At both sites, trenching and augering done by Phillips (1987) revealed conical depressions in the near-surface Mescalero caliche, culminating at a chimney, proving that they are sinkholes, not wind-deflation features. Phillips' investigation showed that there are several true sinkholes on site, including some that have been observed (e.g., during September, 1984) to conduct storm waters rapidly into the underlying formations. Coincident with several surface depressions on the WIPP site, Barrows (1983 and 1985) discovered anomalous gravity lows, probably due to gypsification of anhydrite or to karst caverns. Phillips (1987) showed that the gravity anomalies coincide with solution chimneys through, and downwarping of, the Mescalero caliche horizon.
From hydrological testing of WIPP-area boreholes, there can be derived many indirect lines of evidence for karst hydrology. The one borehole east of the WIPP site (P-18) indicates water-tightness, presumably because gypsum fracture fillings remain complete. Westward across the WIPP site toward Nash Draw, the increasing transmissivities measured in the Culebra are consistent with dissolution and removal of salt beds, subsidence damage to the gypsum-filled fractures of the Culebra (Neill, et. al., 1998, p. 11), fracturing of the brittle anhydrites above and below the Culebra, and with solution-enlarged fractures and karst conduits that coalesce downstream. Other hydrologic observations are consistent with karst. These include anomalous drawdowns interpreted as high Culebra transmissibility between certain wells but not others (Phillips and Snow, 1997). Lateral channel interconnections are implied by equal Culebra heads at some adjacent wells, and vertical channels are indicated by equal heads in the Culebra and Magenta dolomites at the same wells (Phillips and Snow, 1997). Former anhydrite beds have been converted to gypsum by freshwater recharge (Snyder, 1985). Westward freshening of Rustler waters can best be reconciled with westerly flow and vertical recharge. The youthful ages of some waters sampled from the Rustler can be attributed to rapid, local infiltration (Hill, 1999, pp. 54, 55).
When storm events recharge a mature karst aquifer, they cause a rapid rise of the water table. For lack of observations, water level fluctuations are unrecorded in the Rustler Formation. Not even WIPP-33, placed in a sinkhole, has been converted to an observation well, an obvious choice due to its deep, water-filled caverns. Karst caverns are typically spaced hundreds to thousands of feet apart, so randomly placed holes have negligible probability of encountering them, or of measuring their conductivity. The investigations have largely neglected strata other than the Culebra, few wells having been completed at other levels. If open karst channels are most common near or above the water table, but not in the Culebra, they must be sought by drill holes targeting those levels. Hydrologic testing has done nothing to characterize the karst system clearly present in some places within the WIPP site, nor has it provided representative parameters for modeling. DOE has avoided the necessary research, knowing that proof of karstic conduits would be fatal to the project. There is an affidavit (see Attachment A) from a former employee that Sandia hydrologists were forbidden even to use the word "karst," let alone investigate it.
A few feet below the surface is the Mescalero caliche, which has collapsed into Nash Draw. Testing the hypothesis that the caliche layer does not obstruct rainwater recharge in the vicinity of WIPP, Phillips (1987) dug over 1000 auger holes in and around several closed topographic depressions. The caliche bed has subsided to form funnel shapes below some of the depressions, is dissolved to residual materials in many places, and is absent where solution pipes penetrate it. The deformed caliche surface proves local subsidence, and the solution pipes prove that infiltrating water has locally karstified the caliche. Phillips explored another mile-long karst valley without a surface water course that crosses the west boundary of the WIPP site, and a chain of four sinkholes at WIPP-33 indicating that water carves elongate E-W courses through the underlying Dewey Lake and Rustler beds, at least to the depth of the Magenta Dolomite.
Observations of storm infiltration at sinkholes prove that karst conditions exist in the subsurface. About ten inches of rain fell in the vicinity (registered at Loving, 18 miles WSW of WIPP) on September 18-19, 1985, causing the WIPP-33 sinkhole to fill like a bathtub to a depth of five feet, then disappear in a few days (Phillips, 1987, p. 86). Water also ponded in the fourth depression east of WIPP-33 and rapidly infiltrated the ground. Such water can not seep away laterally from closed topographic depressions. It must follow karst conduits to the water table, joining an interconnected, perhaps locally obstructed conduit system that leads to outlets. Mature karst aquifers usually discharge at large-capacity springs along rivers or shores defining the base-level for the system, and have a strong influence on the water table everywhere upstream.
Storm waters recharge such a karst system in a matter of hours, typically causing a sudden rise and a corresponding rapid increase of spring discharges, noted in days. Wells near WIPP have not been instrumented to provide hydrographs of the karst system, so none substantiate rapid water level rises, but one typical spring- flow event has been observed. On September 5, 1984, following a major storm, Phillips (1987, p. 228) witnessed transient flow into Laguna Grande amounting to at least 100,000 gallons per minute, the water welling up through the floor of nearby Laguna Pequena (Figure 7). This is proof of karst conditions in the watershed. The chemistry of the waters was consistent with Rustler gypsum and dolomite, and dissimilar to either the brine aquifer waters flowing on Salado salt to Malaga Bend or of the effluent from the nearby potash refineries. Such hydrologic and geochemical observations should have been collected routinely by Sandia Laboratories. Years of paper studies and computational modeling have remained unsupported by basic fieldwork. Since Phillips shared his field observations with Sandia hydrologists in 1990, it seems deliberate that Phillips' thesis, one of the few data sources for surface water hydrology at WIPP, was not cited by DOE in the Compliance Certification Application (CCA) or its background documents.
No tracer tests have been done to determine potential karstic flow paths or groundwater travel times. Phillips and Snow (1998, Figure 4) analyzed the transmissivity data and head distribution among the wells, conceiving that there are preferred channel directions from the shaft area southwards and northwestwards, and from the WIPP site westwards along three paths to Nash Draw. One passes through the NW corner of the WIPP site and WIPP-33, one follows the karst valley near the center of the W boundary, and a third lies just south of the S boundary. Upon examination of many drill logs, on and off-site, Phillips (1997b) found breccia or rock fragments, residual clays, open washed-out zones, or lost core intervals strongly suggestive of dissolution at every stratigraphic interval of the Rustler, but not necessarily features that are open today. If residuum has replaced portions of the salt formerly in the Rustler, the dissolution process has been pervasive and perhaps continual, and occasional open conduits are an inescapable corollary, even if they are locally obstructed by residuum.
Dye-tracing of groundwater flows in classic karst areas such as Dalmatia, Florida and Kentucky have demonstrated transient velocities exceeding a mile per day, flows that may even now be matched west of WIPP during storms like those of September, 1984 and 1985 (Phillips, 1987). Travel-time estimates through the WIPP karst (Phillips and Snow, 1998, Snow, 1998 and Hill, 1999) have ranged between 5 years and 500 years from the center of the WIPP site to Nash Draw, but even these may not be conservative. In PA, Culebra transmissivities have been extrapolated from known points of measurement to unknown areas. This concept is invalid because transmissivity in discontinuous karstic rocks does not vary continuously, and because the extremes of Rustler transmissivity are unrepresented in the data set.
The preponderance of evidence supports the contention that PA modeling seriously underestimates releases of radioactivity to the accessible environment. This is reason enough for invalidating the certification granted by the EPA. Given its departures from rationality, the reader should be incredulous that the DOE application was approved. The EPA was well aware that the basis for objections, then and now, has always been that there are karst conditions in the Rustler.
The TRU waste has to be removed from the generator sites, even if an adequate permanent repository has not been established. TRU waste disposal underground remains premature, leaving monitored retrievable storage as the only option. A safe temporary facility could be situated near the surface of an old, stable landform, above the water table. For instance, at WIPP, it could probably be established on the Santa Rosa formation, but not on the Dewey Lake/Rustler karstland. It is evident that disposal in salt at WIPP is not the answer, where travel times in the overlying aquifer will be orders of magnitude shorter than PA predicted. The EPA has erred in certifying the repository, and recertification (in 2003) should be defeated. Meanwhile, TRU waste disposal at WIPP should stop, and the waste already in place in the first panel should be retrieved before roof collapse makes it prohibitively costly and dangerous to do so.
Dr. Snow's research was supported by a grant from the Citizens' Monitoring and Technical Assessment Fund.