Geothermal Exploration at Emerson Pass, Pyramid Paiute Tribal Lands, Nevada

GRC Transactions, Vol. 38, 2014 Geothermal Exploration at Emerson Pass, Pyramid Paiute Tribal Lands, Nevada Lisa Shevenell 1,2, Mark Coolbaugh 3,2, Richard Zehner 4, Gary Johnson 1,2, William Ehni 5, and Donna Noel 6 1 Nevada Bureau of Mines and Geology 2 ATLAS Geosciences Inc. 3 Great Basin Center for Geothermal Energy, University of Nevada, Reno 4 Geothermal Development Associates 5 Ehni Enterprises, Carson City 6 Pyramid Lake Paiute Tribe lisas@atlasgeoinc.com glj@unr.edu sereno@dimcom.net rzehner@gdareno.com ehnient@aol.com dnoel@plpt.nsn.us Keywords Geothermal, NGDS, exploration, Emerson Pass, temperature surveys, gradient wells, Nevada, Pyramid Lake ABSTRACT Five thermal gradient wells were drilled and evaluated as part of a recent collaboration between the Nevada Bureau of Mines and Geology (NBMG) and the Pyramid Lake Paiute Tribe (PLPT) at the Emerson Pass geothermal prospect. Maximum recorded temperatures were 120.8 C at 76 m (250 ft) in one of the wells drilled by the PLPT. A subsequent deeper well drilled by NBMG to 305 m (1000 ft) showed a maximum temperature of 117 C at 168 m (550 ft), with temperatures decreasing below that depth indicating a broad outflow zone between approximately 79 to 238 m (260 to 780 ft) below ground surface at 115 C. Existing data indicate that the shallow, maximum temperature zone of 120 C may be of fairly limited spatial extent based on the size of a vegetation dead zone and the near surface expression of an anomalous temperature zone depicted by several shallow temperature surveys. A deeper higher temperature reservoir could be present, although its temperature and extent remain unconstrained. Purpose The purpose of the project is to 1. Conduct shallow (2 m) temperature surveys to define a shallow thermal anomaly and assist in location of geothermal gradient wells. 2. Drill geothermal gradient well(s) at Emerson Pass, which is considered one of the most promising areas evaluated in previous work (Shevenell and Zehner, 2013). 3. Measure and evaluate temperature distributions at the site. Introduction The goal of this project was to drill temperature-gradient wells in Nevada as part of the Great Basin Consortium (Utah, Nevada, Oregon, and Idaho), from supplemental funding to the state contributions to the National Geothermal Data System (NGDS) through the Arizona Geological Survey. As part of this work, shallow temperature surveys were conducted at several sites in Nevada (Figure 1) to assist in the assessments and location of drilling targets, results of which are discussed in Shevenell and Zehner (2013). Based on these temperature surveys, and other previous work, the Emerson Pass prospect was selected for drilling of thermal gradient wells to better define the thermal anomalies indicated by these previous studies. This paper presents the results recent data collection and evaluation at the Emerson Pass geothermal area. Figure 1. Location of the Emerson Pass geothermal prospect along with other sites evaluated for consideration of more detailed studies, with Emerson Pass being selected for gradient drilling. 29

Background Emerson Pass is on the Pyramid Lake Paiute Reservation (PLPR) and the Tribe is interested in developing their geothermal resources located outside of sensitive areas (e.g., The Needles). There are no springs in the vicinity of the Emerson Pass area from which to collect any water samples. Except for the presence of tufa in the valley, and hydrothermal alteration in bedrock in the ranges (neither active), there are no surface manifestations (e.g., active hot springs or fumaroles) that indicate an active geothermal resource at this location. The two closest wells to Emerson Pass are at nearby Astor Pass, which have recorded temperatures of 76.7 and 21.3ºC, and quartz geothermometry of 177 and 102ºC, respectively. The Tufa occurrences were the impetus for the first exploration work in the Emerson Pass Area (Coolbaugh et al., 2010), which occur at the base of the hill where thermal waters would first reach the valley bottom, issuing as springs at, or near, the paleo-lake shore. Following the identification of the Tufa deposits in Emerson Pass, Kratt et al. (2010) conducted a shallow temperature survey in the area and identified areas of anomalous temperatures at 2 m depth. A maximum temperature of 35ºC was (2 m-deep) was measured ~500 m ESE of the tufa mounds that formed when spring water reacted with water in Pleistocene Lake Lahontan (Coolbaugh et al., 2010; Kratt et al., 2010). A more recent shallow temperature survey (Shevenell and Zehner, 2013) recorded a maximum temperature at 2 m of 60.3ºC. By comparison, background temperatures ranged from 17 to 18ºC at the time of the survey. The PLPR lies within a major zone of strain transfer in the northern Walker Lane, in which dextral shear along NW-striking faults merges with a system of complex N-NNE-striking normal faults. Faulds et al. (2006) postulated that the Pyramid Lake fault horsetails at the north end of Pyramid Lake as strain is progressively transferred to the Astor Pass Terraced Hills area, as well as further to the north in the Smoke Creek Desert. Approximately 3 km south of Emerson Pass, the NW-striking component is well expressed by the alignment of tufa mounds near the Needle Rocks, one of the tribe s sensitive areas. Here, spring temperatures are as high as 97 C (boiling at this elevation). More recent work at Emerson Pass included detailed geologic mapping which located several parallel normal faults in the area that may be conduits for geothermal fluid flow (Anderson and Faulds, 2013). This mapping work was used in conjunction with shallow temperature measurements in this study to locate five geothermal gradient wells, the results of which are presented here. 76 m; 145 to 250 ft) temperature gradient wells were drilled by the PLPT with McKay Drilling and one deeper (305 m; 1000 ft) well by NBMG with Welsco Drilling. Lithologic logs (mud logs) of cuttings were collected from the wells as they were drilled. Physical samples of cuttings from the 305 m well were collected over 3 m (10-foot) intervals for permanent archival in NBMG s core and cuttings facility (the Great Basin Science Sample and Records Library) and remain available for future testing. Static temperature measurements using NBMG s wireline probe were collected on several dates following gradient well completion until the temperatures appeared to have stabilized in each of the wells. As of this writing, three temperature logs had been obtained from each of the gradient wells. Results Shallow Temperature Surveys The Emerson Pass area has an obvious shallow thermal anomaly that has been detected by three different studies: the current work (Shevenell and Zehner, 2013), a PLPT unpublished survey, and Kratt et al. (2010). Although the data are not directly comparable between the current and PLPT work, they both indicate a thermal anomaly in the location depicted in Figure 2. During work at the site in the current project, a 29 station shallow temperature survey was conducted March 6-8, 2013 (Shevenell and Zehner, 2013). This new survey was conducted because there were gaps in the spatial coverage of the previous surveys, and inconsistencies in data such that direct comparisons among stations measured on different dates could not be made because base stations were not utilized during some of the surveys. One set of earlier surveys were conducted over several months between May and October, 2012 during which 209 measurements were collected and several thermal anomalies identified. However, Methods Shallow temperature surveys were conducted at the site using well established methods described by Zehner et al. (2012), Skord et al. (2011), Kratt et al, 2010, Coolbaugh et al. (2007), and Sladek et al. (2007). Results are reported in Shevenell and Zehner (2013), and presented below. Four shallow (44 to Figure 2. Results of shallow temperature surveys conducted in March 2013 (Shevenell and Zehner, 2013) and in April-May, 2010 (and Kratt et al., 2010) at Emerson Pass. 30

these data could not be directly compared among the dates due to the lack of base station data. The initial data collected by Kratt et al. (2010) included base station information, and allowed corrections to be made so that the data are directly comparable to those collected in the 2013 work (and are included in Figure 2). Some sites were re-occupied to verify the anomalies and corrections were made, which indicated that the 98 temperatures recorded by Kratt et al. (2010) in April and May, 2010 were approximately 1 C less than those of the current study (March 2013). Figure 2 shows the results of the combined 2013 and 2010 surveys indicating a thermal anomaly occurs at the site, with a maximum recorded temperature at 2 m of 60.3 C southeast of the Tufa mounds. These data were interpreted in conjunction with other information collected as part of a larger project among Desert Research Institute (DRI), University of Nevada, Reno (UNR) and the Pyramid Lake Paiute Tribe (PLPT), including structural mapping conducted by Anderson and Faulds (2013). Shallow temperatures are observed to decrease northward along a fault mapped by Anderson and Faulds (2013), shown by the green, yellow, orange and blue squares in linear alignment north of the maximum measured temperatures. Temperature Gradient Wells Using this combined information, several shallow gradient well locations were selected to be drilled by the PLPT, with BIA support. One additional location (funded by a DOE NGDS supplemental grant) for a deeper 305 m (1,000 foot) gradient well was selected in conjunction with the structural mapping results (Anderson and Faulds, 2013), with final site selection based on the outcome of the shallower gradient wells drilled by PLPT. The locations were selected to the west of the main fault plane down gradient of the maximum thermal anomaly detected, which was presumed to be at an upflow zone. The location to the west of the maximum anomaly was selected in order to avoid high temperatures in shallow horizons during the gradient drilling in the hopes of either completing above or intersecting these higher temperature zones at depth. Six gradient well locations were selected, and five wells were completed in late 2013 and early 2014 in the area generally within the zone of the anomalously high shallow temperature survey results, the nearby tufa mounds, and a series of N-S faults. The locations of these gradient wells are depicted in Figure 3 and listed in Table 1. All wells were completed as gradient wells with a 5 cm (2 inch) liner, capped at the bottom, filled with water in a steel liner with bentonite in the annular space. Figure 3. Location of temperature gradient wells relative to zone of highest shallow temperatures, faults and tufa mounds. Table 1. Summary of thermal gradient wells drilled in 2013-2014 at Emerson Pass. Max ID East_u83 North_u83 Elev (m) (m) Completed ( C) Temperature (m) EG1 276241 4464522 1235 43.3 10/3/13 96.9 43.3 EG2 276019 4464808 1217 76.2 10/6/13 120.8 76.2 EG3 275711 4465059 1207 76.2 10/8/13 108.1 76.2 EG4 275946 4465242 1225 50.3 10/10/13 97.1 50.3 EG5 276174 4464660 1237 -- not drilled -- -- EG6 276130 4464969 1234 304.8 1/10/14 116.7 167.6 PLPT 4 Wells Four shallow thermal gradient wells were drilled by PLPT in October 2013 (EG1-EG4). Temperature logs were conducted by William Ehni shortly after well completion and by NBMG on two subsequent occasions on October 12, 2013 and January 7 and 8, 2014 to verify equilibration. Although the wells showed a slight increase in temperature over the initial logs conducted by Ehni, the wells were very nearly equilibrated only days after completion and showed similar profiles for all dates. Figure 4 illustrates the latest (most equilibrated) temperatures logs obtained by NBMG on January 7, 2014. These plots show that both EG1 and EG2 have a zone of boiling at the same depths ( 33.5 to 45.7 m; 110 to 150 ft), although at different elevations. The temperatures measured in this small isothermal zone were both at 96.4 C, slightly above the boiling point at this elevation (e.g., 95.7 C at 1219 m; 4000 ft). The gradients, above these zones are, therefore, not representative of expected gradients to a higher temperature resource at depth. The EG1 well was not completed below this zone of boiling given that they had encountered a lost circulation zone at the bottom of this well and were unable to penetrate beyond 43.3 m (142 ft) depth. The EG2 well penetrated this zone, although it shows indications of decreasing gradient, possibly becoming isothermal, below approximately 64 m (210 ft) depth. The other two wells (EG3 and EG4) do not show such a boiling zone but have an apparent conductive gradient below approximately 24.4 m (80 ft; EG4) and 36.6 m (120 ft; EG3), although the gradient appears to shallow in EG4 toward the bottom of the hole. Calculated the gradients for the three wells below any zones of boiling indicate abnormally high gradients suggesting the presence 31

Figure 4. Temperature logs obtained from EG1 through EG4 on January 7 and 8, 2014, with the left figure shown in elevation, and the right figure in depth. of a relatively shallow, thermal flow zone not penetrated by the wells. Table 2 shows the calculated gradients in EG2, EG3, and EG4, which range from 260 to 1100 C/km. near the Tufa mounds as well as above and west of the faults mapped to the east that were presumed to control hydrothermal fluid circulation. Four temperature logs were run following the completion of the well and these logs are shown in Figure 5. The log run on January 29, 2014 showed an increased temperature relative to the first log run on January 15, 2014 as the well equilibrated, with an additional increase in temperature in the February 20, 2014 profile, and essentially no additional change was observed in the April 3, 2014 profile. The profiles show the same configuration, with a high calculated gradient (1300 C/km) above a large isothermal (outflow) zone from approximately 79 to 238 m (260 to 780 ft) below surface. A blow-up of the isothermal zone (Fig 6) shows that the logs detect several small temperature deviations over this isothermal depth interval suggestive of small thermal inflow zones, which are subdued in the February 20, 2014 and April 3, 2014 profiles. The five zones are illustrated with yellow horizontal lines at the following depths: 88.4, 121.9, 155.4, 167.6, and 201.1 m (290, 400, 510, 550, and 660 ft) below ground surface. Below approximately 201.1 m the temperatures in the well continuously decline indicating that the large apparent isothermal zone is likely a broad zone of outflow from multiple faults. Table 2. Calculated temperature gradients from three wells based on data collected January 7 and 8, 2014. Apparent 1 (m) 2 (m) Temp 1 ( C) Temp 2 ( C) Gradient ( C/km) EG1 NA EG2 64.0 76.2 117.6 120.8 262 EG3 36.6 76.2 77.5 107.1 747 EG4 24.4 51.5 64.4 96.1 1169 NBMG - 1 Well One 305 m (1,000 ft) temperature gradient well was drilled in January 2014 by NBMG, the lithologic log of which appears in Appendix A. The well penetrated primarily unconsolidated materials with intermittent rock chips observed in the mud return. A lost circulation zone was encountered just below the surface casing between 33.5-39.6 m (110-130 ft), which may have indicated the top of the water table intercepted by this well. Approximately 40 barrels of mud were lost in this depth interval before circulation resumed, which was maintained for the remainder of the well. The location of this well was based in part on the results of EG1-EG4 and previous work from the shallow temperature surveys. The zone of highest shallow temperatures and elevated deeper temperatures from the shallow gradient wells, including a lost circulation zone (EG1), suggest a fairly small, restricted area of high temperature activity at the site at shallow levels (<300 m). The location of the EG6 well was selected to determine if this anomalous temperature zone extended away from the obvious high temperature area, as well as to determine the extent to which the current Tufa mound occurrences might influence the hydrology of the area through structural flow paths. Thus the well was located Dead Vegetation Zone (Dead Zone) During field work at the Emerson Pass site it was observed that there was a zone of dead vegetation at and uphill of the area of maximum temperatures from the shallow temperature surveys. Figure 7 shows the location of this dead zone as mapped with GPS in January 2014. Note the scale bar that shows the zone of dead vegetation measures approximately 305 m (1000 ft) in the N-S direction, and 152 m (500 ft) in the E-W direction at its (m) Temperature ( C) 20 40 60 80 100 120 0 50 100 150 200 250 300 350 Emerson Pass EG6 1/15/2014 1/29/2014 2/20/2014 4/3/2014 Completed 1/10/14 Figure 5. Temperature profiles of EG6 thermal gradient well. 32

(m) Temperature ( C) 100 105 110 115 120 50 75 100 125 150 175 Emerson Pass EG6 200 1/15/2014 1/29/2014 225 2/20/2014 4/3/2014 250 Figure 6. Expanded view of the EG6 temperature logs of Figure 5. The April 3, 2014 profile is not plotted as it overlays the February 20, 2014 profile and the small deviations in temperature noted at the yellow lines are no longer visible by the date of this profile, three months after well completion. maximum extent. Because it was postulated that this zone results from CO 2 degassing in a shallow boiling zone, as intercepted by EG1 and EG2 (see Figure 4), a soil CO 2 survey was conducted. Results of the CO 2 survey can be found in Shevenell et al. (2014) where variations in CO 2 flux in and surrounding this dead zone are documented. It is worth noting that the zone of dead vegetation must reflect a relatively recent change in natural CO 2 (and steam) discharge from the system, possibly reflecting a recent increase in permeability in the upwelling zones. The margins of the dead zone contain dead sagebrush whereas the center consists of patchy small dead grasses or short, stunted plants. Based on repeat site visits, the zone of dead vegetation was apparently more distinct in 2014 than in 2012 and 2013 (Ryan Anderson, pers. comm., 2014). Thus, increased CO 2 surface discharge from a geothermal Figure 7. Location and extent of the zone of dead vegetation near the highest temperature shallow temperatures (red dots) measured at 2 m depth. system can be associated with natural variabilities in the system not associated with commercial production, as is the case at Emerson Pass system which has not experienced any production of geothermal fluids. Heat Loss An estimate of the heat loss from the system can be made based on the distribution of the shallow temperature survey results. Figure 8 shows the locations of the shallow temperature survey points over a larger area than is the focus of Figure 2 around the new temperature gradient wells. This figure shows that the zone of dead vegetation is quite small relative to the total area of the thermal anomaly delineated by the shallow temperature survey results. Contours of the temperatures suggest a hydrothermal outflow plume that extends 4 km in the N-S direction (green and blue contours) from north of the EG4 gradient well into the Emerson Pass valley. A conservative estimate of heat loss is calculated for the area following the methods in Coolbaugh and Sladek (2013) and Coolbaugh et al. (2014), using average temperature anomalies for the individual zones noted in Figure 8 (Blue, Green, Yellow, Pink). Temperature anomaly values (2-meter temperature at anomalous point minus background temperature at 2 meters) were converted into mean temperature gradients representative of the same points using formulas from Coolbaugh et al. (2014). At some locations at Emerson Pass, similar to some other geothermal areas (e.g. Salt Wells, Steamboat Springs), large variations in measured temperatures at 2 m depth can be observed over relatively short horizontal distances where zones of thermal convection approach the surface. In the case of Emerson Pass, these shallow convection zones are likely caused by steam. Even though steam vents were not observed, shallow steam convection is indicated by zones of dead and dying vegetation which correlate with the highest 2-meter temperature anomalies (up to 60 C) and anomalous CO 2 (Shevenell et al., 2014) measurements, and by shallow zones of isothermal boiling temperatures encountered in temperature gradient holes. Temperature anomaly contours in the area of highest temperatures were smoothed to include both high and low temperature measurements to minimize the effects of local hot spots. As such, upwelling zones constitute a relatively small proportion of the overall heat loss estimate. Heat flux was estimated by multiplying the calculated temperature gradients by the thermal conductivity of soils. The same thermal conductivity of the soils was used over all zones (0.617 W/m C). The value was obtained from the Desert Queen-Desert Peak (Coolbaugh and Sladek, 2013) study area based on numerous shallow temperature measurements at several reoccupied locations, and computed thermal diffusivities from this study area. It is assumed that the thermal conductivity is similar for soils in the Emerson Pass area, which is reasonable given the value obtained at Desert Queen is within the middle of the range reported by Robertson (1988) for air filled soils (Figure 13 of Robertson, 1988). The estimate of heat loss over the colored areas of Figure 8 using this method is approximately 3.2 MWt. Note that this is likely a lower limit on heat loss given that some of the area is in rockier terrain on the hill slopes, which would be associated with higher thermal conductivities that are not explicitly reflected in the calculation. 33

Figure 8. Contour of shallow temperatures showing an outflow plume trending away from the drilled area of Emerson Pass. Summary The Emerson Pass area has an obvious shallow thermal anomaly that has been detected by three different shallow temperature survey studies measuring temperatures at 2 m depths. However there are no thermal or non-thermal waters available for analysis and evaluation. Five temperature gradient wells were drilled in late 2013 and early 2014 with several profiles obtained from each well as they equilibrated. The four shallower wells equilibrated quite rapidly, likely, in part, because they were drilled with air, thus minimizing the disturbance of the temperature regime. The deeper gradient well was measured on four occasions up to 83 days after well completion, at which time it was apparently equilibrated. The calculated temperature gradients are unrealistically high to be projected to any reasonable depth, suggesting the presence of a shallow thermal, lateral flow zone in the area that dominates the shallow temperature gradients. Thus, none of the gradient wells suggest a high temperature (>150 C) resource, but are dominated by the shallow outflow zone. However, no water was produced during or after well drilling from which to collect water samples and calculate geothermometers, and estimates temperatures cannot be made. It is recommended that an attempt be made to collect water samples, either by perforating one of the gradient wells, or by drilling a new water well in order to better evaluate geothermal reservoir temperatures. This would allow flow testing in the area to evaluate transmissivities and the rate of fluid withdrawal that can be maintained, particularly if the Tribe decides to use the known 116 C outflow fluids in direct use applications. The data collected thus far suggest a relatively low temperature resource ( 120 C) at shallow depths in a lateral flow zone, 152 m (500 feet) thick. Based on the surface expression of the dead vegetation and shallow temperature anomalies, the highest temperature, shallow thermal zone may be relatively small in areal extent, with the highest temperatures focused along and parallel to range faults. The total area of known thermal occurrences (from the south end of the dead zone to just north of EG4, and from the fault with the highest shallow temperature to just west of EG3) encompasses 0.57 km 2 (0.22 mi 2 ). However, the total area of thermal anomaly depicted in Figure 8 is much larger (2.6 km 2 ), although smaller thermal anomalies were measured over much of this area. Reservoir evaluations (e.g., flow tests) would be required to determine if sufficient water flows are available to produce the known shallow outflow zone for economic purposes (either low temperature ORC power generation or direct use applications). It is likely that this resource is sufficient for most direct use applications if sufficient flow can be demonstrated, noting that flow requirements for most direct uses are considerably lower than those for power generation. In summary, the structural setting, the shallow thermal anomaly, the presence of a dead zone, the CO 2 anomalies, and temperatures of up to 120 C at shallow depths in the gradient wells suggest this is an excellent site for more detailed evaluations, and possibly development of a direct use or a low temperature (small, 3 MW) power generation facility. A deeper higher temperature reservoir could be present, although its temperature and extent remain unconstrained. Acknowledgments Primary funding for this work was provided by the US Department of Energy, National Geothermal Data System Project, supplemental funding to the State contributions to the NGDS through the Arizona Geological Survey, Primary award number DE-EE0002850, with subcontract to Nevada under award NV- EE002850. Funding for the four shallow temperature gradient wells were provided to PI Donna Noel through a BIA grant to the PLPT. The authors thank James Lovekin (GeothermEx) for his thoughtful review of the manuscript. References Anderson, R.B., 2014. Personal communication. Nevada Bureau of Mines and Geology. Anderson, R.B., and J.E. Faulds, 2013. Structural Controls of the Emerson Pass Geothermal System, Washoe County, Nevada. Geothermal Resources Council Transactions 37: 453-458. Coolbaugh, M., C. Sladek, R. Zehner, and C. Kratt, 2014. Shallow Temperature Surveys for Geothermal Exploration in the Great Basin, USA and Estimation of Shallow Convective Heat Loss. Geothermal Resources Council Transactions 38 (this volume). Coolbaugh, M., and C. Sladek, 2013. Measurement of Heat Loss Associated With Shallow Thermal Aquifers in Nevada, USA. Geothermal Resources Council Transactions 37: 249-254. Coolbaugh, M., Lechler, P., Sladek, C., and C. Kratt, 2010. Lithium in Tufas of the Great Basin: Exploration Implications for Geothermal Energy 34

and Lithium Resources. for Geothermal Energy and Lithium Resources 34: 521-526. Coolbaugh, M., C. Sladek, and C. Kratt, 2010. Compensation for Seasonal and Surface Affects of Shallow (Two-Meter) Temperature Measurements. Geothermal Resources Council Transactions 34: 851-856. Coolbaugh, M.F., Sladek, C., Faulds, J.E., Zehner, R.E., and Oppliger, G.L., 2007. Use of rapid temperature measurements at a 2-meter depth to augment deeper temperature gradient drilling: Proceedings, 32nd Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 22-24, 2007, 7 p. Faulds, J.E., 2006, Characterizing Structural Controls of Geothermal Fields in the Northwestern Great Basin: A Progress Report, Geothermal Resources Council Transactions, v. 30, p. 69-76. Kratt, C., C. Sladek, and M. Coolbaugh, 2010. Boom and Bust with the Latest 2m Temperature Surveys: Dead Horse Wells, Hawthorne Army Depot, Terraced Hills, and Other Areas in Nevada. Transactions Geothermal Resources Council 34: 567-574. Robertson, E.C., 1988. Thermal properties of rocks. U.S. Geol. Surv. Open- File Report 88-441, 110 p. Shevenell, L., G. Johnson, K. Ryan, and A. Reid, 2014. CO2 Surveys in Nevada: Two Example Cases. Transactions Geothermal Resources Council 38: (this volume) Shevenell, L., and R. Zehner, 2013. Shallow Temperature Surveys at Four sites in Nevada as Part of the National Geothermal Data System. Transactions Geothermal Resources Council 37: 31-36. EG6 Completed January 10, 2014 From To Appendix A Lithologic Description of Temperature Gradient Well EG6 Sil Clay Py Illite FeOx Other Qtz Vn Cal Vn Reac 10% Lithology / Description 0 10 Note: only 5 samples taken at 0-100ft. 10 20 Gravel - Angular to rounded clasts of various types, and at various stages of alteration. 20 30 40% volcanics, 60% silica-replaced volcanics and breccias, minor clays. 30 40 40 50 Gravel - similar to above but an increase in clay content to about 25%. 1 50 60 1 Gravel - similar to above but another increase in clay content to about 50%, graybrown 3 60 70 in color. 70 80 3 Clay - gray-brown in color, an increased clay content from above. Some gravel present 4 80 90 in clay. 90 100 4 100 110 Clay - mixture of drilling mud and clay. Excess mud used because loss of circulation. 16.7 62 110 120 100% brown to red clay. 16.7 62 120 130 16.7 62 130 140 16.7 62 140 150 16.7 62 Mixture of clasts of andesite(?), clay, and other volcanics. 1 16.7 62 Light green and gray andesite(?) Rock consists of 80% pyroxene and feldspars, but 150 160 very fine grains, difficult to distinguish phenocryst size. 10% pyrite - both disseminated and cubic. Largest cubic pheno about 0.25mm across. > Another clast of green andesite - containing much softer ground mass than above. 3 1.5 18.3 65 160 170 Contains large, dark green, pyroxene/hornblende phenocrysts. 5% disseminated pyrite and cubic pyrite. > Another clast of green andesite - visible phenocrysts of feldspars and pyroxene/ hornblende. 5-10% disseminated pyrite. > 3 2 18.3 65 170 180 Clay content increases 160-190 to 50-60%. Volcanic/other clasts consist of a mixture of granite?/rhyolite?/basalt? and green andesite of varying grain size/softness/oxidation. Pyrite content increases - seeing pyrite in clay and volcanics, sometimes blocks 3 2 1 of disseminated and cubic up to 3mm long. Moderate amounts of disseminated pyrite 180 190 forming between fractures. Clay and other volcanics. Continue to see 30% clay and multiple volcanics/other clasts. Still see 2-3mm blocks 2 2 1 190 200 of pyrite. Sometimes pyrite occurring with green mineral (pyroxene?). 200 210 Clay - red-brown in color, minor volcanic clasts present. 5 4 Temp ( C) Temp ( F) 35

EG6 Completed January 10, 2014 From To Sil Clay Py Illite FeOx Other Qtz Vn Cal Vn Reac 10% Lithology / Description 210 220 Sandy conglomerate. 1 4 1 21.1 70 220 230 Oxidized clasts primarily sandy conglomerate, Clasts are silt to sand sized, sub-rounded volcanics. Ground mass is 60%, soft and dark red-brown in color. Volcanics look 1 4 1 22.2 72 230 240 leached of mineral content, whatever pyrite was present is now severely oxidized. At 2 4 1 22.2 72 240 250 230 there are clear crystals of plagioclase up to 3mm. Also a chunk of silica precipitate (have not seen this since the surface - could be contamination). 1 4 1 23.9 75 250 260 2 4 1 23.9 75 260 270 2 4 1 23.9 75 270 280 1 3 1 26.7 80 280 290 Light green sandy conglomerate. Facies change - 60% light green sandy conglomerate, 40% other clasts. Contains sand-sized to silt-sized clasts of volcanics and quartz, 2 1 2 1 27.8 82 290 300 possibly an andesite source rock. Held together by silica cement(?). Little to no ground 2 2 28.3 83 mass. Disseminated pyrite present, sometimes up to 10-15%. Pyrite continuing to 300 310 form in between fractures and as disseminated nodules. Sometimes it looks like the ground mass has been replaced with pyrite. 2 2 28.3 83 310 320 > Other volcanic clasts present include quartzite, fine grained basaltic andesite with disseminated pyrite specs, chips of clear plagioclase crystals, light green, very 2 2 26.7 80 320 330 fine grained andesite, small chips of oxidized conglomerate from above, and purple feldspar-rich rhyolite to trachyte. 2 2 27.8 82 > 330-340 oxidized bed within green sandstone conglomerate. Very similar to 330 340 oxidized conglomerate beds from above. Pyrite is oxidized as well. 4 1 28.3 83 First sighting of tephra unit - 50% glass and 50% ash. 40% green sandstone conglomerate, 1 1 30.6 87 340 350 30% gray basaltic andesite with speckled pyrite. 350 360 Light green sandstone. Light green sandstone, sub-rounded grains, sand sized, silica 1 1 31.7 89 360 370 cement. Clasts appear to be primarily feldspar and pyroxene, possibly quartz. 5-10% of clasts are other volcanic (dark gray or oxidized). 2% disseminated pyrite as clasts - 1 1 33.3 92 370 380 no pyrite formation in this unit. 1 1 35.6 96 380 390 1 1 36.7 98 390 400 1 1 38.9 102 400 410 1 1 38.9 102 410 420 1 1 41.1 106 420 430 Oxidized unit, 90% of clasts are highly oxidized. Conglomerate, sandstone, minor 1 1 5 1 42.2 108 430 440 volcanics, oxidized pyrite common. The non-oxidized (10%) is mostly green sandstone conglomerate, sometimes with lots of disseminated pyrite. 1 1 5 1 43.3 110 440 450 3 1 5 44.4 112 450 460 Clay - red-brown in color 5 4 44.4 112 460 470 5 4 46.1 115 470 480 Clay and shale - soft, clay to silt sized, platy shale, interbedded with red-brown clay. 4 4 47.2 117 480 490 4 4 47.8 118 490 500 4 4 500 510 3 4 48.3 119 Dark gray sandy conglomerate. Appearance of dark gray sandy conglomerate with 3 4 48.9 120 510 520 high amounts of oxidized pyrite (up to 15%), sub-angular to sub-rounded sand sized clasts. Sandy conglomerate could derive from basaltic andesite parent rock. Evidence of silica/calcite veining (hard to tell because veinlets are so small). Near veinlets, 1 4 49.4 121 520 530 oxidation increases, possible foliation or shearing. 530 540 Clay - 80% red-brown clay 4 4 49.4 121 540 550 Shale and sandy conglomerate. About 50% red-brown shale, interbedded with dark 3 1 4 49.4 121 550 560 gray, oxidized sandy conglomerate. Oxidized pyrite and non-oxidized pyrite present. Laminated oxidized beds present in shale. 560-580 Appearance of weathering within 3 1 4 50.0 122 560 570 light green sandstone - the outer edges of all grains are being weathered to white clay. 1 1 4 51.1 124 570 580 1 1 4 51.1 124 580 590 Primarily dark gray sandy conglomerate, with about 5-10% oxidized pyrite. About 1 3 1 51.1 124 590 600 5-10% of the weathering green sandstone conglomerate present. 1 3 51.7 125 600 610 1 3 51.7 125 Temp ( C) Temp ( F) 36

EG6 Completed January 10, 2014 From To Sil Clay Py Illite FeOx Other Qtz Vn Cal Vn Reac 10% Lithology / Description 610 620 Shale. Red-brown shale with minor dark gray sandstone. 1 3 53.3 128 620 630 Primarily dark gray sandy conglomerate, seeing some minor veinlets. One vein 3 3 54.4 130 630 640 infilled with clear, radial crystal habit (could be gypsum?) - very unsure about that. About 5% rusted disseminated pyrite. 1 2 54.4 130 640 650 1 2 57.8 136 650 660 3 3 57.8 136 660 670 1 3 48.9 120 670 680 2 3 48.9 120 680 690 Shale. Red-brown shale 4 2 51.7 125 690 700 Red-brown shale with white to pink very soft clay-like material. Saw some clear 4 2 51.7 125 700 710 feldspars - could indicate ash bed? When dry it is light and chalky, could be ash or diatomite, or both. Contains minor amounts of small mafic material - indicating reworking. 3 2 51.7 125 710 720 3 2 51.7 125 720 730 3 2 54.4 130 730 740 3 2 54.4 130 740 750 Clasts of dark gray sandy conglomerate and basaltic andesite. 3 1 54.4 130 750 760 Volcaniclastic rock(?), light green reworked tuffaceous material and varying sized 3 1 54.4 130 760 770 volcanic clasts. 3 1 54.4 130 770 780 Dark gray sandy conglomerate, oxidized. At 800ft, becomes a mixture of sandy conglomerate 1 1 54.4 130 780 790 and basaltic andesite. 1 1 54.4 130 790 800 1 1 54.4 130 800 810 1 1 54.4 130 810 820 1 1 55.6 132 820 830 Shale. Red-brown shale 1 1 56.7 134 830 840 Dark gray sandy conglomerate and basaltic andesite 1 1 57.8 136 840 850 Shale. Red-brown shale 1 1 58.3 137 850 860 Dark gray sandy conglomerate and basaltic andesite 1 1 58.3 137 860 870 1 1 59.4 139 Tephra material and dark gray sandy conglomerate. Appearance of reworked tephra 1 1 60.0 140 material again, making up about 30% of sample. Also 40% dark gray sandy conglomerate 870 880 and 20% brown shale. 880 890 Dark gray sandy conglomerate and basaltic andesite 1 1 62.2 144 890 900 Shale. Red-brown shale 1 1 62.2 144 900 910 Dark gray sandstone. Oxidation and weathering around some individual grains (of 2 1 62.2 144 910 920 basaltic andesite?). Weathering veneer around these grains appears to be brown and oxidized (could be oxidized pyrite). Some grains more weathered than others - with 2 1 62.2 144 920 930 oxidized ground mass. At 950, basaltic andesite appears and continues to 980. Also 1 1 62.8 145 930 940 minor appearance of red-brown shale. 1 1 62.8 145 940 950 1 1 64.4 148 950 960 1 1 64.4 148 960 970 1 1 65.6 150 970 980 1 1 65.6 150 980 990 Dark gray sandy conglomerate and basaltic andesite and 30% red-brown shale. 2 1 66.1 151 990 1000 Dark gray sandy conglomerate and basaltic andesite. 2 1 1000 1010 Alteration -- Mineralization 1=trace, 2=weak, 3=mod, 4=st, 5=intense). Temperature is mud return temperature Temp ( C) Temp ( F) 37

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