A06_WellSiteReport-MasonPass_ForReferenceOnly.pdf

Well Site inveStigation

Site Name: Mason Pass Well, Mason Valley Basin (108)—designated basin

Use of water: Stockwater. Permit 49424 / Certificate 12576, 100% BLM ownership. Priority 1985.

Legal Description: T. 14 N., R. 25 E., Sec. 19 NESW (MDBM) (N14 E25 19ACBC1)

State, County: Nevada, Lyon County

Field Office: Sierra Front Field Office

Date Examined: June 17, 2019 and August 8, 2019

Topographic Map: Mason Butte Quadrangle 7.5 minute series; Carson City 100K

Aerial Photography: n/a

Evaluated by: Niki Cutler, Hydrologist

Accompanied in field / Reviewed by: Dan Erbes, Nevada State Office Hydrogeologist

Altitude of Land Surface (source of elevation data): Less than 4,400 feet (ft) above mean sea level (amsl) based on United States Geological Survey (USGS) 7.5” topographic map, and 4,400 ft amsl in Nevada Division of Water Resources (NDWR) Bulletin #38 (Huxel and Harris, 1969).

Existing Well: The Mason Pass Well (MPW), located in Mason Valley and shown on Figure 1, was completed December 4, 1958 using a cable tool well drilling rig (NDWR Well log No. 32542 http://water.nv.gov/DisplayWellLogQueryReport.aspx). The well log, included in Appendix A, records layers of clay, sand, gravel and boulders to the completed depth of 120 ft below ground surface (bgs) (e.g., approximately 4,280 ft amsl). First water was encountered at 72 ft bgs. The chief water bearing formation was a sand layer recorded from 107-120 ft bgs. The well was completed in an 8-inch borehole using 6-inch steel casing with perforations (1/8-inch by 2-inch) from 100-120 ft bgs. No sand-pack was installed. The standing water level recorded following well completion was 65 ft bgs (e.g., water level elevation approximately 4,335 ft amsl).

Appurtenances included a wind water pump (decommissioned in 2015), pipeline and round trough. Recent field visits by BLM staff in 2018 and 2019 suggest up to 10 ft of debris in bottom of well and no standing water. A down-hole camera survey conducted in August 2019 recorded 360˚ every 10 ft and showed perforations have been sealed off due to scaling. A non-use notice of forfeiture was sent to BLM from NDWR on August 10, 2017. The State Engineer granted BLM an extension of time until August 20, 2020 to get the water back into use.

http://water.nv.gov/DisplayWellLogQueryReport.aspx

Mason Pass Well

Description of Geology: The following geological description is summarized from Morrison and Frye (1965), Proffett (1977), Proffett and Dilles (1984), Parsons (1995) and Reheis (1999).

The MPW site is located within the western Great Basin of the Basin and Range Physiographic Province on the east side of the Sierra Nevada in Lyon County, Nevada. Basin and Range style extension commenced in west-central Nevada during the Miocene (23.0 to 5.3 million-years ago) and continues to present. Two distinct extensional styles are commonly observed: (1) an initial stage of isolated highly extended terranes where mid-crustal rocks are exposed at the surface, exhumed by low-angle normal faults, uplift, and erosion, and (2) a second, later stage of higher-angled block faulting.

The east slope of the Sierra Nevada is complex and irregular and the physiographic and structural break between the Sierra Nevada and the Basin and Range is gradational. The east slope of the range is cut by a number of major normal faults delineating north-trending ranges which are connected to the main mass of the Sierra Nevada on the southern ends but diverge from the range northward creating deep intervening sediment filled basins. The Singatse and Wassuk ranges on either side of Mason Valley are two block ranges bounding a sediment filled basin of this type.

The MPW site is located along the western edge of Mason Valley at the base of the Singatse Range, a primarily west-tilted fault block approximately 25 miles in length. Geologic units exposed near the MPW site in the Singatse Range comprise Mesozoic (251.9 to 66 million-year old) meta-volcanic and sedimentary rocks which have been intruded by the Jurassic-age (~201.3 to 145 million year old) Yerington batholith (see Figure 2). The Mesozoic rocks were deeply eroded during late Cretaceous (~145.0 to 66.0 million-years ago) and early Tertiary (66.0 to 0.01 million-year old) and overlain by a thick sequence of volcanic and sedimentary lithologies. All units were tilted steeply to the west as a result of crustal extension in the Miocene and displaced into numerous blocks by easterly-dipping listric normal faults. The eastern front of the Singatse Range is marked by an irregular normal fault scarp (the Montana-Yerington fault) with indicated movements of up to 1,500 ft of down-throw on the east.

During the Pliocene (5.3 to 2.58 million-years ago) and Pleistocene (2.58 to 0.1 million-years ago), Mason Valley received sediments from surrounding highlands. Pleistocene sedimentary rocks included fanglomerates, fluvial deposits (e.g., ancestral Walker River), as well as lacustrine clays and beach deposits formed during two high stands of Pluvial Lake Lahontan (Morrison, 1964), the Eetza high stand rising to an elevation of about 4,380 ft amsl approximately 50,000 years ago, and the Sehoo high stand rising to about 4,370 ft amsl approximately 20,000 years ago.

Fanglomerate and fluvial deposition likely continued between lake high stands. Holocene age (0.12 million-years ago to present) deposits included fanglomerate, dune sand, and Walker River floodplain alluvium.

FIGURE 2

GEOLOGIC MAP

WEST-CENTRAL MASON VALLEY

LEGEND After Dilles and Proffett (1984)

Quaternary Alluvium

Jurassic Yerington Batholith intrusive rocks, Jqm and Jpqm, quartz monzonite

Mason Pass Well

(select geologic units)

Jqm Jbqm

Montana-Yerington Fault

Fault (dashed where inferred)

Qal

The Walker River flows north through Mason Valley until reaching the valley’s northern end near Wabuska, Nevada. Here the river changes course, turning eastward and ultimately south towards Walker Lake. Sedimentary evidence suggests that the Walker River changed course at least twice in the previous 13,000 years, instead flowing northwest through Adrian Valley (e.g., Churchill Narrows) from a point near present-day Wabuska and into the Carson River. During these course changes the Walker River ceased to flow into Walker Lake, causing it to dry up. During the Pleistocene, the Churchill Narrows also connected Pluvial Lake Lahontan between the Carson Sink and Mason Valley during the Eetza and Sehoo high stands.

Inferred Aquifer (description and depth of producing zone) and Analysis of Data: The following information is referenced from Morrison (1964), NDWR Water Resources Bulletin #38 (Huxel and Harris, 1969), the Geologic Map of the Yerington District, Nevada (Proffett and Dilles , 1984) , and the Yerington Mine Hazard Ranking System Report (EPA, 2016).

Groundwater in Mason Valley generally flows south to north in the direction of the north flowing Walker River. Groundwater flow directions are affected locally by bedrock outcrops along valley margins and drawdown from pumped wells and irrigation activities on cultivated fields in Mason Valley. The alluvial aquifer consists of well-sorted deposits of sand and gravel from ancestral channels of the Walker River and fan deposits from valley floor down-faulting with concurrent up-lifted mountain blocks. Monitoring wells installed throughout the valley are categorized into shallow, intermediate and deep zones based on interbedded clays/fine silts, however these fingers are laterally discontinuous and not indicative of true zones.

The MPW is completed in shallow alluvium near the western valley margin adjacent to the consolidated rock/valley fill boundary and categorized as “less than 60% sand and gravel ratio to all other material” (Huxel and Harris, 1969, pp 11-13, Figure 3). Transmissibility (the capability of water to move through the porous medium) estimates for the area near the MPW site are approximately 25,000 gallons per day per ft (gpd/ft) (Huxel and Harris, 1969, Figure 4).

Transmissibility nearer the center of the valley vary from 50,000-200,000 gpd/ft.

The MPW site resides at a surface elevation of approximately 4,400 ft amsl above and to the west of present-day Walker River. Topographic relief surrounding the MPW site ranges from slight to moderate. Carson Hill on the east flank of the Singatse Range rises nearly 600 ft to an elevation of 4,989 ft amsl within one-mile southwest of the MPW site. The surface slope to the northeast from the MPW site towards Mason Valley is more gradual, dropping only 60 ft in elevation to 4,340 ft amsl over a distance of one mile. The Sunset Hills located one-mile southeast of the MPW site range up to 4,624 ft amsl in elevation.

Bedrock exposed directly southwest and upslope of the MPW site comprises Yerington batholith quartz monzonite. The Sunset Hills south and southeast of the MPW site also comprise Yerington batholith quartz monzonite surrounded by recent alluvium. The north-south trending Montana- Yerington fault is inferred over a mile southeast of the MPW site in Mason Valley alluvium immediately east of Sunset Hills. This relationship suggests the MPW site likely occurs on a structural bench comprising an intermediate fault block situated east of the Singatse Range and west of the Montana-Yerington fault. The occurrence shallow bedrock within a mile west and south of the MPW site, west of the primary range front fault, suggests the alluvial aquifer thickness in the area surrounding the MPW site is likely much less than aquifer thicknesses encountered in Mason Valley east of the Montana-Yerington fault.

Estimated Static Water Level: The standing water level recorded following completion of the MPW in 1958 was 65 ft bgs (e.g., water level elevation approximately 4,335 ft amsl). In 1966, the MPW is cited in NDWR Water Resources Bulletin #38 (Huxel and Harris, Table 25, Well No. 14/25- 19ac1) as having a water level of 68.38 ft bgs (e.g., approximately 4,331.62 ft amsl). During that period, Anaconda Copper Company operated the Yerington Copper Mine (from 1956 to 1978) approximately six miles south-southeast of the MPW. Dewatering associated with open pit mining at the Yerington Copper Mine reportedly did not directly affect the alluvial groundwater west of the open pit (EPA, 2016), and water levels in the alluvial aquifer surrounding the pit have recovered substantially since mining ceased in 1978. Therefore, impacts from nearby open pit mining will not be considered further in this investigation.

Monitoring conducted in 2015 associated with closure of the nearby Yerington Mine Site (EPA, 2016) indicates water levels proximal to the MPW site may have declined over 46 feet to an elevation of 4,285.56 ft amsl over the last 49 years. There are multiple monitoring wells nearby the MPW site with screens straddling the water table. Water levels recorded from these wells in 2015 suggest a steep localized westward groundwater gradient exists between Mason Valley and the MPW site as shown on Figure 3. This contrasts with the groundwater gradient observed within Mason Valley which is northerly and much flatter (e.g. suggestive of higher permeability/transmissivity). The steeper westward gradient proximal to the MPW is likely attributed to the limited thickness of saturated alluvium residing over less permeable shallow bedrock in that area. Selected well data from wells nearby the MPW site are listed in Table 1.

The groundwater gradient measured between the MPW site and Mason Valley, west of the Montana-Yerington fault, is westerly at about 0.02 ft/ft (EPA 2016, Figure 11). Projecting that gradient west 3,900 ft from Well B/W-54S (e.g., water level elevation of 4,306 ft amsl in 2015) suggests a conservative drop in water level by about 78 feet (e.g., 3,900 ft * 0.02 ft/ft = 78 ft) at the MPW site, which equates to a projected groundwater elevation of 4,228 ft amsl, or 172 ft bgs based on the surface elevation of 4,400 ft amsl. It is possible water may be encountered at a shallower depth based on a water level measurement reported at monitoring well B/W-58S (EPA 2016, Figure 11) in the vicinity of the MPW site which suggests a water level elevation of 4,285.56 amsl (e.g., about 115 ft bgs).

FIGURE 3

POTENTIOMETRIC SURFACE MAP

WEST-CENTRAL MASON VALLEY

LEGEND

After EPA (2016) HRS

Mason Pass Well

Mason Pass Well (MPW)

B/W-58S 4285.56

Monitor Well Groundwater Eleva�on (Measured 2/23/15 - 2/25/15)

Groundwater Contour (Interpolated and Inferred)

Red Shed Well

Table 1. Potentiometric surface, shallow alluvial aquifer (EPA, 2016, Figure 11; NDWR, 2019)

Monitoring well no.

Groundwater elevation, amsl

Screen interval, amsl

Location 11 S (UTM) Comment

B/W-27S 4,335.36 (2015) 4,339-4,319 310801 / 4322746 Near valley floor, background monitoring well

B/W-64S 4,336.5 (2015) 4,348-4,328 311149 / 4321945 Near valley floor, background monitoring well

B/W-83S 4,336.4 (2015) 4,326-4,306 311141 / 4322366 Near valley floor, background monitoring well

B/W-54S 4,306 (2015)

B/W-53S1

B/W-53S2 4,300 (2019*) 4,270-4,190 Red Shed Well

B/W-108

Mason Pass Well (MPW)

4,362 (2015) 4,300-4,280 Water level reported 30 feet above 1966 level (error?)

B/W-58S 4,285.56 (2015) B/W-58S aka 14/25-19ac1

*http://water.nv.gov

Anticipated Yield: Fractured bedrock at a depth of 172 ft bgs beneath the MPW site is anticipated to have a specific capacity of about 4.2 gallons per minute (gpm) per foot of drawdown. The current water right is for 2.17 acre-feet annually or 1.34 gpm metered.

The yield anticipated from shallow bedrock occurring west of the Montana-Yerington fault proximal to the MPW site is best supported by Well B/W 53S2 (e.g., Red Shed Well). The Red Shed Well is located north of the Sunset Hills, less than one mile southeast of the MPW site.

According the well log for the Red Shed Well (NDWR No. 40321), included in Appendix A, drilling was completed in 1992 to a depth of 263 ft bgs from a surface elevation of 4,460 ft amsl. The Red Shed Well was drilled from an elevation about 60-feet higher than the MPW site, encountered about 70 feet of alluvium and then advanced another 193 feet through fractured bedrock encountering water in bedrock fractures yielding 75 gallons per minute (gpm) for 20 hours and exhibiting 18 feet of drawdown (e.g., a specific capacity of about 4.2 gpm/ft). Water level records available from NDWR (2019) indicate the depth to water recorded in the Red Shed Well on October 30, 2019 was 159.86 feet bgs, which equates to a water level elevation of approximately 4,300 ft amsl.

Recommendation for Site:

Recommend completing a new well, as opposed to deepening the existing well. The new well should be designed to extract sufficient resource from shallow fractured bedrock to meet current needs. A nearby well with a specific capacity of 4.2 gpm/ft of drawdown was completed in shallow fractured bedrock. During the completion phase of the well, BLM will need to coordinate with the driller to identify the specific capacity. The conservative estimated depth to water in the shallow alluvium and/or fractured bedrock in the vicinity of the MPW site is approximately 172 ft bgs.

Drilling and Well Construction Recommendations:

A mud and/or air rotary drilling rig would be most appropriate for drilling in competent bedrock anticipated at the MPW site. A pilot hole should be drilled initially to a depth of approximately 200 to 250 ft bgs proximal to the MPW site to identify potential production zones within the shallow alluvium (if present) and/or fracture zones (if any) in the underlying bedrock. The pilot hole should be drilled as far east of the current well as allowed without changing the point of diversion under the current water right (e.g. up to 300 ft).

The final well design should be based on production zones identified in the pilot hole. A well diameter of 6” will require a borehole of 10” to accommodate for the 2” (minimum) annulus and should allow for sufficient production. The well should be drilled deep enough to accommodate proper efficiency while providing sufficient capacity for the end use. The pump should be set in the cased section of the well within the saturated zone and sufficiently above the lowest screened interval (e.g., for a maximum desired production rate of 20 gpm at a specific capacity of 4 gpm/ft, the pump intake should be set in the cased section of the well at least 5-feet above the lowest screened interval). Acknowledging water levels near the MPW site appear to have declined nearly a foot-per-year over the past 49 years, it would be prudent to include additional saturated capacity within the cased section of the well above the lowest screened interval in the final well design, if possible.

Casing should be set in all unstable or potentially unstable zones, and a well screen installed in the producing zone(s) to prevent sand or silt from entering the well. The annulus will need to be packed properly with filter material, which will prevent (or slow) silt from entering the well. It may be unlikely, however, if multiple production zones are found, then one should be selected, since there are State regulations set to limit mixing between aquifers. There may be waivers if the issue of multiple zones arises. The well screen preferably should be of the continuous slot, wire wound type; louvered or machine cut slots may be used. Perforations made with a cutting torch, hacksaw, or punched in place with a casing perforator should not be used since these perforations allow sand or silt to enter the casing, resulting in damage to the pump. The well should be properly developed by pumping, surging or jetting. An aquifer test for yield must be conducted to verify the quantity of water available, measured in gpm/ft of drawdown.

Additionally, a water sample should be collected for majors/miners, isotopes and nutrients as a baseline to compare to later if needed.

The well must be drilled by a Nevada licensed well driller, and in accordance with applicable state regulations.

An access port should be provided at the surface to allow future measurement of water levels.

This access port should be at least 1/2 inch in diameter, and should have a screw-on type of cover to allow for ease of removal and inserting a water level tape into the well.

A new pump and power source (e.g., windmill/sucker rod, solar or other appropriate power source) should also be installed. The trough and associated conveyance system should be rebuilt, and a meter should be installed to record production.

References:

Dilles, J. M. and Proffett, J. M., 1984. Mesozoic and Cenozoic geology of the Yerington district, Lyon County, Nevada, Nevada Bureau of Mines and Geology Map 77.

EPA, 2016. Hazard ranking system documentation record (HRS), Anaconda Copper Mine, Yerington, Lyon County, Nevada, EPA ID# NVD083917252, prepared by EPA Region 9 in September 2016.

Huxel, Jr., C. J. and Harris, E. E., 1969. Water Resources Bulletin #38. Water resources and development in Mason Valley, Lyon and Mineral Counties, Nevada, 1948-1965. Prepared in cooperation with United States Department of the Interior Geological Survey. 103 pgs.

Morrison R. B., 1964. Lake Lahontan: Geology of southern Carson Desert, Nevada, a stratigraphic study of the Cenozoic geology of part of the basin of Lake Lahontan, one of the great late Pleistocene lakes of Western Untied States.

Morrison R. B. and Frye J. C., 1965. Correlation of the Middle and Late Quaternary successions of the Lake Lahontan, Lake Bonneville, Rocky Mountain (Wasatch Range), Southern Great Plains, and Eastern Midwest Areas.

Proffett, J. M., 1977. Cenozoic geology of the Yerington district, Nevada, and implications for the nature and origin of Basin and Range faulting, Geological Society of America Bulletin, v. 88, p.

247-266, February 1977.

Parsons, T. E., 1995. The Basin and Range province: Chapter 7, in Continental rifts: evolution, structure, and tectonics, pp. 277-324, K.H. Olsen ed.

Reheis, M., 1999. Extent of Pleistocene lakes in western Great Basin, USGS misc. field studies map MF-2323.

NDWR, 2019. State of Nevada Division of Water Resources website: http://water.nv.gov/ Permit 49424, Well Log 32542, well water measurements for MPW and nearby wells: including Red Shed Well, Permit 58527, Well Log 40321.

http://water.nv.gov/

APPENDIX A

NDWR Well Logs (2)

Mason Pass Well Log 32542 - Page 1 of 2:

Mason Pass Well Log 32542 - Page 2 of 2:

Red Shed Well Log 40321 - Page 1 of 1