GRC Transactions, Vol. 38, 2014 Geothermal Assessment of the Reno-Tahoe Airport, Nevada Lisa Shevenell 1,2, Gary Johnson 1,2, and Katie Ryan 1 1 Nevada Bureau of Mines and Geology 2 ATLAS Geosciences Inc lisas@atlasgeoinc.com glj@unr.edu Keywords Geothermal, NGDS, exploration, Moana, Reno Airport, temperature surveys, gradient wells, Nevada ABSTRACT The Moana geothermal system in southwest Reno, NV has been used for decades for domestic and commercial space heating using a the low temperature resource, intercepted at relatively shallow depths ( 90 C at <305 m(<1,000 ft)). As such, several commercial properties in southwest Reno have expressed interested to the authors in utilizing geothermal resources for building heating and cooling including the Grand Sierra Resort, Reno- Sparks Convention Center, Atlantis Casino and the Reno-Tahoe Airport. However, data in these areas to evaluate the geothermal potential has been sparse. Recent funding from DOE afforded the opportunity to fill in some data gaps in this area to begin evaluation of the geothermal potential outside of the main Moana geothermal system. This work included drilling a 305 m (1,000 ft) temperature gradient well on the Reno-Tahoe International Airport property. Unconsolidated sediments were penetrated throughout the length of the well, which had an equilibrated, conductive temperature gradient of 56 C/km. The Moana resource (west of the Airport) is being used by the Peppermill Hotel-Casino, pumping 79 C waters from 425 to 1,341 m (1,400 to 4,400 ft). Based on this new gradient well, the depth in the Airport area to attain the top of a resource with similar temperatures would be approximately 1,220 m (4,000 ft). Hence, preliminary indications are that there is not a currently economic resource beneath the Airport property, due to the large depths of drilling that would be required to penetrate the unconsolidated sediments and intersect the fractured andesite unit hosting the resource on the west side of the Airport site. Introduction The Moana geothermal area in Southwest Reno has long been used for geothermal space heating at Manzanita and Warren Estates and intermittently at the Peppermill Casino, with new geothermal production initiated in 2010 that has allowed the Casino to heat 195,000 m 2 (2.1 M ft 2 ) of their hotel towers and swimming pools. The first author has been contacted on numerous occasions by the Airport Authority to ask what the geothermal potential of their area is. Existing data compilation showed large data gaps in this area such that it was not possible to determine if the Moana system extended under the property. Funding made available through a National Geothermal Data System supplemental grant provided the resources to investigate if thermal anomalies could be identified on the Airport property. As such, a 305 m temperature gradient well was drilled on the Reno-Tahoe Airport property. The goal of this project is to collect new data and 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 (2013a). Based on available data from previous work, the site location downgradient from the Moana geothermal system being used for space heating, interest by the Airport Authority, and existence of a gap in data on the property such that its geothermal potential was unknown, the Reno Airport prospect was selected for drilling of a thermal gradient well to determine if the thermal anomalies west of the Airport extended to the Airport property. Additionally, this site was selected because funding for this work was federal, it was decided that the Airport would be a better investment for public use and not specifically favor any particular business (e.g., Grand Sierra or Atlantis Casinos, who have also expressed interest in geothermal development). This paper presents the results of recent data collection and evaluation at the Reno-Tahoe Airport. Purpose The purpose of the project is to 1. Compile exiting information that may assist in assessing the geothermal potential of the Airport; 19
the potential of the Airport property. There are no gradient data or water chemistry samples within the Airport property, with an obvious gap in spring/well data when plotted on a map with available information in the Reno area (Figure 2). Additionally, there are no springs or open wells on the property that could be sampled. This area was selected due to this lack of available information, ease of access, interest by the Airport Authority, likelihood of more rapid development than other areas if sufficient resources were to be located, and available funding to conduct the investigation. The west side of the airport was the focus of the work because that is the area of current and planned buildings, and this area is closer to the known Moana geothermal system. Methods Figure 1. Location of the Reno-Tahoe Airport geothermal prospect along with other sites evaluated for consideration of more detailed studies. Shallow temperature surveys were conducted at Charnock Ranch, Darroughs Hot Springs, Pinto Hot Springs, Emerson Pass and the Airport (Shevenell and Zehner, 2013a), and one gradient well was drilled at Emerson Pass (Shevenell et al., 2014) and the Airport, described here. 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 (2013a), and presented below. One 1,000 ft well was drilled by Welsco Drilling with NBMG supervision. Lithologic logs (mud logs) of cuttings were collected by NBMG from the well as it was drilled. Physical samples of cuttings from the 305 m (1,000 ft) 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. The well was completed as a gradient well with a 5 cm (2 inch) liner capped at the bottom and bentonite in the annular space. Static temperature measurements using NBMG s wireline probe were collected on several dates following gradient well completion until the temperatures stabilized. 2. Conduct shallow temperature survey to determine if a shallow thermal anomaly exists at the site; 3. Drill a geothermal gradient well; 4. Measure and evaluate temperature profiles in the new well; 5. Provide a preliminary assessment of the potential to use geothermal fluids to heat Airport property buildings. Background Over the past 10 years, continued interest has been expressed by the Airport Authority, the Reno-Sparks Convention Center, the Grand Sierra Resort and the Atlantis Casino in using geothermal resources for space heating, most recently from the Airport and Grand Sierra (Figure 2). As essentially no data are available from within the Airport property, only surrounding areas, there has been insufficient information from which to assess Figure 2. Map showing well bore temperatures and relative locations of the Airport study area, Grand Sierra Resort, Atlantis Casino-Reno Convention Center area, and the developed Peppermill and Manzanita/Warren Estates areas, within the Moana geothermal system. 20
Table 1. Summary of shallow temperature survey. Temperature ( C) Min Max Average Std Dev Reno-Tahoe Airport (N = 11) T 1.5m 8.3 13.2 10.5 1.5 T 2m 8.7 13.5 10.7 1.5 Figure 3. Shallow temperature survey results at the Reno-Tahoe Airport. The purple circles show locations of the probe sites with all sites measuring background temperatures in the 9-15 C range. Several probes were wet when removed, and these sites labeled wet. Figure adapted from Shevenell and Zehner (2013a). Geochemistry No springs or wells are available on the Airport property from which to collect water samples. Historical samples surrounding the area, including the well-known Moana geothermal area are available, however. Figure 2 shows the distribution of water temperatures around the Airport, with a gap in data on the Airport property. Figure 4 shows only the wells closest to the Airport, with a summary of data from these wells listed in Table 2. The closest four samples to the property indicate temperatures of 16.4 to 18.5 C, with three of the four from wells that are only 4.6 to 7.6 m deep. Only one of these four locations has sufficient chemistry from which to calculate geothermometers, an Air National Guard well (Table 2; depth unknown). The highest temperature measured near the Airport is 21 C from a 209 m deep well (Terminal Way location on Figure 4). Nearby thermal waters are known in the Moana geothermal system to the west where temperatures up to 99 C have been measured in shallow wells (approximately 90 m deep), and warm waters to the east and southeast of the Airport are also present. Geothermometers in the Moana area are on the order of 110 C (chalcedony), and the nearby Peppermill Hotel water chemistry indicates a reservoir temperature of up to 134 C (Na-K-Ca, Mg-corr) (data link: http://www.nbmg.unr.edu/geothermal/ GeochemDatabase.html). The Airport is likely down gradient of these two areas, and elevated temperatures at depth are possible, although probably most suitable for direct uses rather than Results Shallow Temperature Survey A shallow temperature survey was conducted on April 4, 2013 in which 11 probes were placed, five of which were wet when removed (Figure 3). All temperatures are low (<13.5 C; see Table 1), ranging from 8.7 to 13.5 C with an average of 10.7 ± 1.5 C at 2 m, with slightly lower temperatures recorded at 1.5 m (averaging 10.5 ± 1.5 C). Groundwater in the area is at only 2.4 m (8 feet) depth at some times of the year, and it was not surprising that the shallow cold zone would mask any geothermal signature at deeper levels. Gradient hole drilling was conducted to determine if geothermal waters occur below this shallow cold zone. Table 1 documents the minimum, maximum, average and standard deviation measured at each of the probe sites at 1.5 and 2.0 m depth. No thermal anomalies were detected with the shallow survey; temperatures are observed to increase slightly with depth. Figure 4. Location of wells closest to the Airport, summarized in Table 2. The red star shows the location of the 305 m gradient well drilled during this project. 21
electrical power generation. The TG-1 gradient well drilled at the site provides the first available data to investigate the possibility of thermal waters beneath the Airport. Existing data do not suggest a thermal anomaly beneath the property (e.g., Figures 2 and 4), but there is an obvious data gap on the Airport property. Table 2. Maximum geothermometer temperatures ( C) from areas nearest to and surrounding the Airport. Table 2 summarizes the maximum geothermometer temperatures of sites surrounding the Airport property, and suggests highest temperatures are to the west of the Airport. The maximum temperature of 98.5 C (chalcedony geothermometer at the NWIS well, SW of the Airport) exceeds those currently being produced by the Peppermill to the west, suggesting the possibility that there may be a geothermal resource in the southwest part of the Airport property. An estimated gradient is included in the table using the temperature at total depth and an assumed temperature of 10.7 C at 2 m (based on shallow temperature results). The depths expected to an 80 C resources, if present, are based on these estimated gradients. One water sample was collected from the TG-1 well on February 6, 2014 once it was found that the well leaked around the annulus and water was allowed to discharge through the 22 installed valve. It is unclear where the water originates, although the temperature logs (below) suggest an influence of this leakage between 30.5 and 82 m (100 and 270 ft) as the temperature became isothermal in this zone in later surveys. Although the sample was expected to be contaminated with drilling mud, and it was Locale Name T ( C) (m) Chalced ( C) Na-K-Ca K/Mg Est Gradient ( C/km) to 80 C (km) to 80 C (ft) SW SPPC Well - Peckham Lane 19.5 142.4 -- -- -- 63 1.1 3634 SW USGS Well - Peckham 16 7.6 80.4 50.5 46.1 Too shallow -- -- SW NWIS Well 30BADD1 18 6.4 98.5 68.5 62.3 Too shallow -- -- W Air Natl Guard 16.4 4.6 78.7 -- -- Too shallow -- -- NW Wooster School USGS Well 1 17.8 11.6 76.7 64 78.5 Too shallow -- -- NW SPPC Well - Mill St 18.5 201.2 66.7 53.4 51 39 1.8 5813 NNW SPPC Well-Terminal Way 20 208.8 76.7 64 -- 45 1.5 5062 NNW Terminal Way 21 209 -- -- -- 50 1.4 4576 N Liston Park Well 16.5 11.9 85.5 72.3 59.3 Too shallow -- -- NE SPPC Well - Greg St 17 83.5 62.2 54.3 50.1 77 0.9 2948 E Boynton Slough 18.5 4.3 86.9 55.6 52.7 Too shallow -- -- SW Airport TG-1 well 28.6 304.8 85 55 53 56 1.23 4019 Assumed background temperature is 10.7 C at 2 m depth. Figure 5. Photo of filters containing colloidal drilling mud material filtered out of the 2.75 L water sample collected from TG-1. as observed on the multiple filters during sampling (Figure 5), the ultimate TDS was low at 324 mg/l, with estimated chalcedony, Na-K-Ca and K/Mg within the range observed for other samples collected around the Airport. Chalcedony temperatures are calculated to be 85 C, but it is unknown the extent to which the sample is contaminated. Because bentonite muds have colloidal material <0.45 um through which waters were filtered (Figure 5), the elevated SiO 2 observed in the sample cannot be reliably attributed to the pristine water of the aquifer. Hence, the collected sample provides an indication of a thermal influence, but would require confirmation by an uncontaminated sample to verify or refute the actual geothermometer temperature. Based on results from higher temperature systems (Figure 8 in Shevenell and Zehner, 2013b, reproduced below in Figure 6), cold waters can provide an indication of geothermal waters at depth, with estimated temperatures lower than, but trending toward the reservoir temperature, as illustrated for Desert Peak and Salt Wells. Although the sampled and geothermometer temperatures of the Moana area are less than those of the Desert Peak and Salt Wells areas, they show the same general trend in measured versus geothermometer temperatures, with estimated geothermometer temperatures well above measured temperatures from the sampled cold and warm waters. The trend suggests these fluids may originate from a reservoir approaching 125 C (several samples plot at 125 C on Figure 6, although all of these are upgradient from the Airport location). Cation and silica geothermometers indicate a Moana-system reservoir temperature of 125 C, with the Peppermill production horizon being within an outflow zone of this reservoir (Spampanato et al., 2010). However, given that the Airport would also be in a more distal outflow from this source area, lower temperatures were anticipated beneath the property. In any event, the elevated geothermometer estimates from the various Moana area geothermometer estimates from cold waters may be a valuable exploration tool even if the temperature estimates cannot be taken literally. Estimated chalcedony temperatures nearest to Airport TG-1 are up to 98.5 C from one 18 C well (NWIS Well 30BADD1; 800 m SW of TG-1) and 78.7 C from a 16.4 C well (Air National Guard Well; 1250 m N of TG-1), which suggested there may be an economic resource beneath the Airport property.
Shevenell, et al. Figure 6. Measured temperature versus geothermometer estimates from cold and warm waters in Nevada, with the Reno samples in and near the Moana geothermal system in brown. Figure reproduced from Shevenell and Zehner (2013b). Gradient Well Drilling Figure 9. Plot of seven temperature profiles from the Airport TG-1 well. The Airport TG-1 well was spudded on September 10, 2013 and completed on September 16, 2013 by Welsco Corp. to a depth of 305 m (Figure 4 (red Star) and Figure 7). The well penetrated Neogene sedimentary units (undivided) as mapped by Ramelli et al. (2011). All mud returns were from unconsolidated sediments with significant clay that impeded drilling progress throughout much of the boring. Description of the mud returns appears in Appendix A. East-west sections across the Truckee Meadows through Reno are presented in NBMG OFR11-7 (Ramelli et al., 2011), with the C-C section being drawn just north of the east-west runway at the Airport (Figure 8). This section shows that the Neogene sedimentary unit (Tn on ORF11-7 map) may be as thick as 457 to 610 m (1500 to 2000) ft in this area of the Airport such that basement would not be intercepted until approximately 610 m (2000 ft) depth. At this depth is the Kate Peak andesite (Tua), which is the current production zone at the Peppermill HotelCasino, although earlier production in the 1980s was within the shallower Neogene clastic unit at 100 and 284 m (328 and 934 ft) at 53 C (Spampanato, et. al., 2010). The new wells drilled in 2009 and 2010 for the expansion of the Peppermill space heating system found an intensely fractured zone occurs in the Kate Peak andesite from 762 to 1,036 m (2,500 to 3,400 ft), making the andesite highly permeable in this horizon. The Peppermill #8 well for the 20092010 expansion of the geothermal heating system was perforated from 431 to 1,348 m (1,415 to 4,421 ft) to produce thermal waters from this broad zone. Figure 7. Drill rig at TG-1, Reno-Tahoe Airport, September 2013. Temperature Profiles Figure 8. West to East cross section (C-C ) modified from Ramelli et al. (2011) showing the location of the Airport TG-1 well, bottoming above the andesite (Tua), which occurs at 457 to 610 m (1,500 to 2,000 ft) in this area. 23 Seven temperature profiles were obtained from TG-1 between 2 and 140 days after the September 15, 2013 completion of the well (Figure 9,
Table 3. Summary of temperature logs from Airport TG-1 well. Date Table 3). The well was clearly not equilibrated during first survey on September 17, 2013 (Figure 9) and suggested a conductive gradient of 42 C/km. The well had essentially come to equilibrium two months later on November 17, 2013, with the final profile measured February 18, 2014 indicating a conductive gradient of 56 C/km. The irregular pattern between approximately 30 and 80 m (100 to 270 ft; yellow vertical bar on Figure 9) depth after October 24, 2013 apparently results from the initiation of a leak in the well. The valve open to the annular space flowed about 38-57 L/min (10 to 15 gpm) when opened on February 5, 2014 indicating the bentonite had washed out in this zone. The valve had not been opened prior to this date, and the profiles suggest the leak may have occurred earlier. Although a water sample was collected, it was heavily contaminated with drilling mud as evidenced by the filters (see above). Gradients were calculated between 97 m (320 ft) and total depth to eliminate this and other near surface perturbations in the temperature profile. Estimated gradients increased from the initial 42 to the final 56 C/km on February 18, 2014. After this final log, the well was plugged and abandoned. Although temperature logs and bottom hole temperatures are not presented in Spampanato, et. al. (2010), the reported temperatures of Peppermill #8 and #9 are suggestive of gradients on the order of 51 and 47 C/km, respectively, assuming the maximum temperatures occur at total depth. The actual gradients are likely higher given the maximum temperature may not be at total depth as this system is presumed to be in an outflow of the higher temperature system feeding the Moana geothermal area, and the Peppermill is producing from a large perforated interval (431 to 1,348 m). Presumably higher (economic) temperatures occur at shallower depths within this interval, which may be in an isothermal zone. These lower limits on the estimated gradients of the Peppermill wells noted above are similar to the Airport TG-1 well of approximately 56 C/km (equilibrated). However, the TG-1 well is entirely in the unconsolidated valley fill, whereas those in the Peppermill wells are partly completed in andesitic rock. Thermal conductivities in unconsolidated fill can be on the order of 2 times lower than those in rock (e.g., Robertson, 1988) indicating that for the same gradient, the heat flow in the Peppermill area could be up to twice that in the Airport area (e.g., Blackwell and Chapman, 1977). Conclusions Gradient ( C/ km) (m) to 100 C (212 F) (m) to 79 C (174 F) September 17, 2013 42.0 2013 1536 September 24, 2013 53.1 1652 1275 October 10, 2013 54.0 1628 1258 October 24, 2013 53.1 1652 1275 November 17, 2013 53.6 1640 1266 February 5, 2014 55.0 1608 1245 February 18, 2014 56.0 1582 1225 Shallow temperature surveys, geochemical evaluation of existing data, gradient well drilling and temperature logging were conducted at the Reno-Tahoe Airport as part of DOE supported geothermal assessments. Although there are no direct indicators of geothermal potential on the Airport property itself, nearby data suggest there may be a resource beneath the property that could be tapped for direct uses. Given the interest expressed by the Airport Authority, this site was selected for gradient drilling to encourage use of the geothermal resource, if present. It is likely that this site would actually be developed in the near-future if a suitable resource could be located. Unconsolidated sediments were penetrated throughout the length of the well, which had an equilibrated temperature gradient of 56 C/km, but a bottom hole temperature of only 28.6 C. No notable fluid inflows were detected during drilling of the gradient well. The Moana resource is being used by the Peppermill Hotel- Casino, pumping 79 C waters from 427 to 1,341 m (1,400 to 4,400 ft). Based on this new gradient well, the depth in the Airport area to attain the top of a resource with similar temperatures would be approximately 1,220 m (4,000 ft). Additionally, gradients might shallow (decrease) in wells as they penetrate the Kate Peak Andesite beneath the airport due to increased thermal conductivities of the rock, so that suitable temperatures (e.g., 79 C) may be even deeper than 1,220 m beneath the Airport. Hence, preliminary indications are that there is not a currently economic resource beneath the Airport property, due to the large depths of drilling that would be required to penetrate the unconsolidated sediments and intersect the fractured andesite unit hosting the resource to the west of the Airport site. 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. Partial funding for this work was provided via salary support by Nevada Bureau of Mines and Geology. The authors thank Duncan Foley (Pacific Lutheran University) for is thoughtful review of the manuscript. References Blackwell, D.D., and D.S., Chapman, 1977. Interpretation of geothermal gradients and heat flow data for Basin and Range geothermal systems. Geothermal Resources Council Transactions 1: 19-20. 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. 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. Geothermal Resources Council Transactions 34: 567-574. Ramelli, A.R., C.D. Henry, and J.P. Walker, 2011. Preliminary revised geologic maps of the Reno urban area, Nevada. Nevada Bureau of Mines and Geology Open-File Report 11-7. http://www.nbmg.unr.edu/dox/ of117plate1.pdf Robertson, E.C., 1988. Thermal properties of rocks. U.S. Geol. Surv. Open- File Report 88-441, 110 p. 24
Skord, J., C. Sladek, M. Coolbaugh, P.H. Cashman, M. Lazaro, and C. Kratt, 2011. Two-Meter Temperature Surveys for Geothermal Exploration Project at NAS Fallon. Geothermal Resources Council Transactions 35: 1023-1027. Sladek, C., Coolbaugh, M.F., and R.E. Zehner, 2007. Development of 2-Meter Soil Temperature Probes and Results of Temperature Survey Conducted at Desert Peak, Nevada, USA. Geothermal Resources Council Transactions 31: 363-368. Shevenell, L., R. Zehner, G. Johnson, W. Ehni, D. Noel, and K. Ryan, 2014. Geothermal Exploration at Emerson Pass, Pyramid Paiute Tribal Lands, Nevada. Geothermal Resources Council Transactions 38: (this volume). Shevenell, L., and R. Zehner, 2013a. Shallow Temperature Surveys at Four Sites in Nevada as part of the National Geothermal Data System. Geothermal Resources Council Transactions 37: 31-36. Shevenell, L., and R. Zehner, 2013b. Geochemical Data Collection and Evaluation as Part of the National Geothermal Data System. Geothermal Resources Council Transactions 37: 437-444. Spampanato, T., D. Parker, A. Bailey, W. Ehni, and J. Walker, 2010. Overview of the Deep Geothermal Production at the Peppermill Resort. Geothermal Resources Council Transactions 34: 957-962. Zehner, R.E., Tullar, K. N., and Rutledge, E, 2012, Effectiveness of 2-Meter and Geoprobe Shallow Temperature Surveys in Early Stage Geothermal Exploration, Geothermal Resources Council Transactions 36: 835-841. Appendix A Hole No. Airport TG-1 Alteration/Mineralization - 1=trace, 2=weak, 3=mod, 4=st, 5=intense From To Lithology / Description 0 10 Gravel - undifferentiated alluvium 10 20 20 30 Clay (90%) - dark tan in color 5 30 40 Gravel - containing grains of quartz, volcanics, andesite, breccia? Basalt? 1 40 50 Range in size from coarse sand to fine gravel 1 50 60 1 60 70 1 70 80 1 80 90 1 90 100 Casing set to 100 1 100 110 Gravel 1 110 120 Clay (100%) - dark tan in color 5 120 130 Contamination? - cement 130 140 Gravel - same as above, contains grains of quartz, volcanics, some oxidized 2.5 140 150 clasts, some larger, rounded clasts (may indicate contamination?), minor pyrite. 2 150 160 2 160 170 2 170 180 2 180 190 Gravel - primarily gray in color (may indicate change in parent rock) T=75F 190 200 increase in clay 3 increase in andesite, andesite makes up 70% of sample, with minor quartz 3 200 210 and other grains 210 220 3 220 230 3 230 240 3 240 250 decrease in clay content, T=75F 1 Sil Decal Clay Py Illite C FeOx Other Qtz Cal Dolo Reac 10% 25
From Hole No. Airport TG-1 To Lithology / Description Gravel - higher oxidation than in the gravel above. Andesite to basaltic andesite 60%, oxidized andesite 10%, chert and quartzite and other grains make up 30% of sample. Alteration/Mineralization - 1=trace, 2=weak, 3=mod, 4=st, 5=intense 250 260 260 270 2 270 280 2 280 290 1 Gravel - increase in clay content, large chips of andesite. Andesite 70%, 3 1 290 300 quartz 10%, chert 5%, other grains make up 15% of sample. T=80F 300 310 3 1 310 320 3 320 330 3 330 340 Gravel - increase in clay and increase in oxidation. Contains mixture of 3 340 350 quartz, granite, andesite, chert, shale. 3 350 360 increase in oxidation T=77F 3.5 360 370 3 370 380 3 380 390 1 390 400 T=75F 5 1 400 410 increase in clay content to 90% 3.5 1 410 420 3.5 1 420 430 3.5 1 430 440 3.5 1 440 450 3.5 1 450 460 increase in clay to 95%, becomes slightly darker gray, T=79F 4.5 460 470 4 470 480 Gravel - mostly andesite with 20% clay material. 1 480 490 1 490 500 Clay - gray in color, makes up 90% of sample 5 500 510 5 510 520 5 520 530 T=80F 5 530 540 5 Gravel/Clay - consists of andesite material, minor chert and minor granite 2 540 550 present. Gravel is 60% of sample and clay is 40% 550 560 increase in clay to 60% 4 560 570 4 570 580 4 580 590 Clay - makes up 95 to 100% of sample 5 590 600 T=85F 5 600 610 clay becoming more sandy 5 610 620 5 620 630 5 630 640 5 Sil Decal Clay Py Illite C FeOx 2 Other Qtz Cal Dolo Reac 10% 26
From To Hole No. Airport TG-1 Lithology / Description 640 650 Gravel - andesite makes up 60% of sample, clay 10%, 10% green rock with 650 660 visible phenocrysts, 10% oxidized clasts, 10% other grains. 660 670 670 680 680 690 690 700 700 710 710 720 720 730 730 740 740 750 increase in clay and oxidation 750 760 760 770 770 780 Gravel/Clay - 50/50 split of both 780 790 Gravel - very similar to above, but possibly slightly more clay. Drillers 790 800 indicate a lot of clay but it is not apparent in the chips, they could have been over-rinsed 800 810 810 820 820 830 830 840 840 850 850 860 860 870 Clay - mostly gray-brown clay, with only about 20% gravelly sand present 3 870 880 3 880 890 increase in clay content to 90% 4 890 900 4 900 910 3 910 920 Gravel - gravelly sand, high in andesite, clay makes up 30-40% 1 920 930 1 930 940 1 940 950 1 950 960 1 960 970 1 970 980 increase in clay content to make more of a 50/50 split 3 980 990 Clay - gray-brown in color with 20% gravelly sand. 4 990 1000 4 1000 1010 Clay changes to light gray 4 Temperatures are mud return temperatures in F. Alteration/Mineralization - 1=trace, 2=weak, 3=mod, 4=st, 5=intense Sil Decal Clay Py Illite C FeOx Other Qtz Cal Dolo Reac 10% 27
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