U.S. Department of the Interior Prepared in cooperation with the Scientific Investigations Map 3310 U.S. Geological Survey North Platte Natural Resources District, South Platte Natural Resources District, Twin Platte Natural Resources District, Conservation and Survey Division of the University of Nebraska-Lincoln, and the Nebraska Environmental Trust Sheet 1 of 2

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4,150 4,250 4,350 Index map 4,350 North Platte Natural 4,150 Resources District EXPLANATION 4,100 4,200 4,100 4,350 State Route 156 4,050 4,150 South Platte Natural Resources District (NRD) 4,350 4,100 airborne electromagnetic area 4,000 4,100 Twin Platte Natural 4,100 4,300 Resources District Twin Platte NRD airborne electromagnetic area 4,050 4,000 4,050 4,100 3,950 North Platte NRD airborne electromagnetic area 3,900 4,200 4,200 2010 airborne electromagnetic flight line 4,050 4,200 4,250 4,200 4,250 2008 and 2009 airborne electromagnetic flight line 3,950 4,250 4,250 (Abraham and others, 2012) 42° 4,000 4,250 4,000 3,950 South Platte Natural 4,050 4,200 Cooperative Hydrology Test hole 4,000 4,250 Resources District Study boundary 4,150 4,150 3,850 3,900 4,200 3,950 3,900 Base from National Atlas of the United States, 2014 030 60 MILES Shaded relief from Esri, 2013 3,900 4,100 Lambert Conformal Conic projection 3,800 3,850 4,150 4,150 4,150 Horizontal coordinate information is referenced to the 4,100 Creek 0 30 60 KILOMETERS North American Horizontal of 1983 (NAD 83) 3,800 3,950 4,100 3,850 3,850 3,750 4,100 92 92 4,100

Figure 1. Location of 2010 airborne electromagnetic (AEM) flight lines (this study), and 2008 and 2009 airborne electromagnetic flight lines. 3,900 4,200 e

4,200 3,950 tu 4,100 3,900 3,900 4,050 4,050

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4,050 the BOA configuration is the use of airborne electromagnetic (AEM) etatS 3,800 3,950 ABSTRACT 4,050 3,900 4,000 4,150 surveys. State Route 161 3,850 3,800 EXPLANATION 4,050 4,100 Tributary of 4,100 4,100 Water resources in the North and South Platte River valleys of From 2008 to 2010, the USGS and its cooperators collaborated 3,750 4,000 3,950 Structure contour—Shows altitude of base of aquifer. Dashed Nebraska, including the valley of Lodgepole Creek, are critical to the to use airborne geophysical surveys for areas of the North and South 4,150 3,900 4,050 4,200 3,950 4,100 where approximately located. Contour interval is 50 feet. Datum 4,000 social and economic health of the area, and for the recovery of threat- Platte River valleys including the valley of Lodgepole Creek in 4,150 4,250 3,900 is National Geodetic Vertical Datum of 1929 (NGVD 29) 3,900 3,900 3,900 3,750 ened and endangered species in the Platte River Basin. Groundwater western Nebraska (fig. 1). The objective of the surveys was to map 3,800 3,850 3,850 4,000 3,100, 3,350, 3,600, 3,850, 4,100, 4,350, 4,600, 4,850, 5,100, 5,350 State Route 92 4,300 3,850 and surface water are heavily used resources, and uses are regulated the aquifers and underlying bedrock topography of selected areas to 4,100 3,900 3,850 3,950 3,150, 3,400, 3,650, 3,900, 4,150, 4,400, 4,650, 4,900, 5,150 3,900 3,950 4,050 3,850 in the study area. Irrigation is the dominant water use and, in most help improve the understanding of groundwater and surface-water 4,150 4,200 3,700 3,900 3,200, 3,450, 3,700, 3,950, 4,200, 4,450, 4,700, 4,950, 5,200 3,750 3,800 4,250 4,800 4,450 instances, is supplied by both groundwater and surface-water sources. interactions to guide water-management decisions. This project was 4,200 4,5504,000 3,750 3,250, 3,500, 3,750, 4,000, 4,250, 4,500, 4,750, 5,000, 5,250 4,500 3,850 4,400 4,300 3,700 4,000 4,000 The U.S. Geological Survey and its partners have collaborated to use a cooperative study involving the Nebraska Environmental Trust, 4,400 3,800 4,300 4,550 4,550 4,350 3,300, 3,550, 3,800, 4,050, 4,300, 4,550, 4,800, 5,050, 5,300 4,750 3,850 4,200 4,600 3,750 airborne geophysical surveys for areas of the North and South Platte the NPNRD, the South Platte Natural Resources District (SPNRD), 4,200 4,700 4,400 4,250 4,600 4,450 4,200 3,850 4,550 4,650 4,450 State Route L62A Alt Structure contour control point—Symbol color indicates elevation River valleys including the valley of Lodgepole Creek in western the Twin Platte Natural Resources District (TPNRD), Conservation 4,350 4,500 4,350 4,250 4,250 4,300 3,900 3,900 4,500 4,700 3,750 range, in feet above NGVD 29 4,450 4,450 3,650 Nebraska. The objective of the surveys was to map the aquifers and and Survey Division of the University of Nebraska-Lincoln, and the 4,600 3,800 3,850 4,000 4,200 4,500 3,800 3,100–3,150, 3,350–3,400, 3,600–3,650, 3,850–3,900, 4,100–4,150, 4,400 4,300 4,150 4,550 underlying bedrock topography of selected areas to help improve USGS. 4,550 4,100 3,850 3,750 4,350–4,400, 4,600–4,650, 4,850–4,900, 5,100–5,150, 5,350–5,400 4,450 4,600 3,950 the understanding of groundwater–surface-water relations to guide 4,250 4,600 This report presents the interpreted BOA surface for parts of the 3,750 3,850 3,900 3,150–3,200, 3,400–3,450, 3,650–3,700, 3,900–3,950, 4,150–4,200, 4,300 4,300 4,400 4,450 4400–4,450, 4,650–4,700, 4,900–4,950, 5,150–5,200 water-management decisions. This project was a cooperative study area consisting of the NPNRD, SPNRD, and TPNRD (figs. 2 and 3). 4,500

4,350 4,600 4,500 4,550 4,550 4,350 3,700 3,850 3,200–3,250, 3,450–3,500, 3,700–3,750, 3,950–4,000, 4,200 –4,250, involving the North Platte Natural Resources District, the South The interpretations presented in this report build on previous work 4,000 3,850 3,900 4,450–4,500, 4,700–4,750, 4,950–5,000, 5,200–5,250 Platte Natural Resources District, the Twin Platte Natural Resources (Abraham and others, 2012) by including AEM survey data collected 4,600 4,100 3,750 3,950 4,150 3,800 3,250–3,300, 3,500–3,550, 3,750–3,800, 4,000–4,050, 4,250–4,300, 4,500 4,400 District, the Conservation and Survey Division of the University of in 2010 (U.S. Geological Survey Crustal Geophysics and Geochem- 4,550 4,300 3,950 4,500–4,550, 4,750–4,800, 5,000–5,050, 5,250–5,300 4,550 4,000 3,950 3,900

6,4 4,050 4,350 4,450 4,600 3,700 Nebraska-Lincoln, and the Nebraska Environmental Trust. 4,500 4,600 4,700 5 4,250 4,200 4,300 3,300–3,350, 3,550–3,600, 3,800–3,850, 4,050–4,100, 4,300–4,350, istry Science Center, 2014), and lithologic descriptions and borehole 0 4,150 4,400 4,100 3,600 3,700 4,450 4,000 3,600 4,550–4,600, 4,800–4,850, 5,050–5,100, 5,300–5,350 4,150 3,950 This report presents the interpreted base-of-aquifer surface for geophysical logs from additional test holes provided by separate 4,050 3,650 Tributary of Bayard Drain 4,250 4,300 3,650 3,650 part of the area consisting of the North Platte Natural Resources Dis- but related studies (James C. Cannia, U.S Geological Survey, writ- 4,450 4,100 3,700 4,250 4,300 4,200 3,700 North Platte Natural Resources District airborne electro- 4,500 3,750 3,900 trict, the South Platte Natural Resources District, and the Twin Platte ten commun., 2012; Hobza and Sibray, 2014; T.A. Kuntz, Adaptive 3,750 magnetic survey boundary 4,600 3,650 3,850 4,250 4,650 3,550 3,900 Natural Resources District. The interpretations presented herein build Resources Inc., written commun., 2012). This information will be 4,500 4,000 South Platte Natural Resources District airborne electro- 4,600 4,300 4,050 4,550 4,350 4,100 3,800 3,700 3,700 on work done by previous researchers from 2008 to 2009 by incor- used to improve the accuracy and representativeness of the existing 4,400 4,450 3,750 magnetic survey boundary 4,100 4,150 porating additional airborne electromagnetic survey data collected in hydrogeologic frameworks of the NPNRD, SPNRD, and TPNRD. 4,200 3,750 3,900 US Route 85 4,150 3,700 2010 and additional test holes from separate, related studies. To make The geology and water resources in the study area have been 4,150 3,850 4,250 4,150 4,150 4,000 3,950 4,100 4,250 the airborne electromagnetic data useful, numerical inversion was described by many earlier investigators (Darton, 1903a, 1903b; Wen- 4,200 4,200 3,700 4,250 4,300 used to convert the measured data into a depth-dependent subsurface zel and others, 1946; Bjorklund, 1957; Smith, 1969; Smith and Soud- 4,300 4,400 4,350 4,150 3,650 resistivity model. An interpretation of the elevation and configuration ers, 1971, 1975; Swinehart and others, 1985; Souders, 1986; Sibray 4,400 4,450 3,500 3,650 3,650 4,400 3,850 3,550 3,700 of the base of aquifer was completed in a geographic information sys- and Zhang, 1994; Steele and others, 2007). Cannia and others (2006) 4,200 3,550 3,600 4,350 4,250 3,550 4,350 3,700 3,600 3,600 4,300 4,150 4,350 4,200 3,600 tem that provided x, y, and z coordinates. The process of interpretation constructed a hydrostratigraphic framework and characterization of 4,200 4,250 State Route 88 4,300 4,000 3,650 3,550 involved manually picking locations (base-of-aquifer elevations) on underlying aquifers of the COHYST area (fig. 1) that were used in 3,950 3,700 State Route 151 3,850 4,100 4,200 3,900 3,750 3,550 4,050 3,800 the displayed airborne electromagnetic-derived resistivity profile by recently published groundwater-flow models (Carney, 2008; Luckey 4,050 4,250 3,700 4,300 3,700 4,000 3,500 the project geophysicist, hydrologist, and geologist. These locations, and Cannia, 2006), which included all of the study area. Within the 3,500 3, 450 Creek 4,000 3,600 3,650 or picks, of the base-of-aquifer elevation (typically the top of the study area the principal aquifer is the High Plains aquifer system, 3,550 3,400 3,950 State Route 92 3,550 3,700 3,600

73 3,600 Brule Formation of the White River Group) were then stored in a geo- which is composed of the following geologic units: 4,000 3,500

2 4,050 3,900

referenced database. The pick was made by comparing the inverted RC • Quaternary-age deposits of alluvium and valley-fill deposits, State Route 88 3,650 3,750 3,600 airborne electromagnetic-derived resistivity profile to the lithologic 3,800 3,700 3,500 and eolian sand; 3,750 3,500 3,550 3,550 3,850 3,600 descriptions and borehole geophysical logs from nearby test holes. 4,050 3,750 3,550 • Broadwater Formation of Tertiary age; 3,900 3,550 The database of interpretive picks of the base-of-aquifer elevation was 4,050 3,600 3,800 used to create primary input for interpolating the new base-of-aquifer • Ogallala Group of Tertiary age; 3,600 3,950 3,550 contours. 3,450 • Arikaree Group of Tertiary age; and 4,100 4,000 3,400 The automatically generated contours were manually adjusted 3,550 • Brule Formation of the White River Group (referred to hereaf- 3,750 3,500 based on the interpreted location of paleovalleys eroded into the 3,550 ter as the Brule) of Tertiary age, where the Brule is fractured 3,800 3,450 base-of-aquifer surface and associated bedrock highs, many of which 4,050 3,650 (Gutentag and others, 1984; Cannia and others, 2006). 3,700 3,600 Lisco 3,400 were unmapped before this study. When contours are overlain by 3,750 3,350 3,700 4,100 3,900 3,350 3,250 The Brule forms the BOA in most parts of the study area. Cannia 3,450 3,300 the water-table surface, the saturated thickness of the aquifer can be 3,800 3,200 and others (2006) mapped localized areas where the Brule is absent; 3,750 3,600 computed, which allows an estimate of total water in storage. The 3,850 41°30' 3,650 3,500 contours of the base-of-aquifer surface presented in this report may undifferentiated Cretaceous-age units form the BOA near the North 4,150 3,400 4,400 3,600 3,550 Platte River in the western part of the NPNRD and in the TPNRD 3,300 be used as the lower boundary layer in existing and future groundwa- 4,300 4,350 0 4,250 3,80 4,200 4,100 3,600 3,350 ter-flow models. The integration of geophysical data into the contour- south of Lake McConaughy (fig. 1). 4,050 Creek 4,150 3,900 ing process facilitated a more continuous and spatially comprehensive 3,650

view of the hydrogeologic framework. 3,850 3,400 METHODS 3,800

3,800 26

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1 3,850 3,700 3,850 3,650 3,600 3,500 3,450 3,400 3,550 This section of the report summarizes the methods used to RC INTRODUCTION 4,000 3,450 enhance existing BOA contours using information from additional 3,950 3,950 4,150 3,850 3,500 3,900 3,800 3,900 Water resources in the North and South Platte River valleys AEM surveys. Further detail and information regarding the process- State Route 216 3,850 3,550 4,000 3,850 of Nebraska, including the valley of Lodgepole Creek (fig. 1), are ing workflow including geophysical data processing and inversion 4,200 3,950 3,600 4,450 critical to the social and economic health of the area, and the man- can be located in Abraham and others (2012). 4,400 3,500 4,600 4,550 4,500 4,450 4,350 3,800 3,650 Hypsometric contours of the BOA surface of the study area were 4,800 3,850 agement of endangered species along the Platte River corridor. Both 4,850 4,950 4,300 3,900 groundwater and surface water are heavily used resources, and uses modified using the following data: lithologic descriptions and bore- 4,400 4,900 4,100 5,000 4,250 are regulated in the study area and in the entire Platte River Basin. In hole geophysical logs from additional test holes, time-domain elec- 5,050 4,100 3,950 3,900 tromagnetic (TDEM) surveys, and AEM surveys. Investigation of the 4,700 3,800 4,650 4,450 4,150 addition to regulated water resources use is the need to provide water 4,550

4,600 4,750 4,500 3,850 BOA began by first assembling all the available information, which 4,450 4,400 4,550 4,200 4,250 3,750 for the recovery of threatened and endangered species in the Platte 4,500 Creek State Route 92 4,800 4,250 3,850 3,700 3,650 4,200 3,600 River Basin. The Platte River Recovery and Implementation Program included existing geographic information system (GIS) data for BOA 4,850 4,150 3,550 4,950 4,900 4,150 4,100 3,900 5,000 3,500 (PRRIP) is a partnership between the U.S. Department of the Interior, contours (Abraham and others, 2012; Cannia and others, 2006), 4,500 4,100 3,950 and the States of Wyoming, Colorado, and Nebraska to manage hab- depth to the geologic units that form the BOA at available test holes 5,150 5,050 4,450 3,700 3,850 itat and water for recovery of the threatened and endangered species (University of Nebraska-Lincoln, Conservation and Survey Division, 5,100 4,400 3,750 3,800 3,550

2014), test holes drilled in separate but related studies (J.C. Cannia, 4,350 3,600 in the Big Bend reach (not shown in any maps) of the Platte River 3,650 5,050 4,150 U.S. Geological Survey, written commun., 2012; Hobza and Sibray, 3,750 3,800 3,850 3,700 (Kenny, 2008). Water for the program is stored in Lake McConaughy 5,000 4,200 5 4,300 3,750

1 3,900 4,950 4150 3,950 3,900 or received from the South Platte River (fig. 1). Some of the water 2014; T.A. Kuntz, Adaptive Resources Inc., written commun., 2012), 2

4,000 e

tu 4,100 3,800 from the North Platte River is distributed downstream to the Big Bend and digitized unpublished hand-drawn outcrop maps (R.F. Diffen- 4,900 3,950

oR eta oR dal Jr., University of Nebraska-Lincoln, Conservation and Survey 4,100 3,850 reach of the Platte River to improve and maintain the habitat of threat- 4,850 3,950 4,150 3,950

3,900 Division, unpub. data, 2013; J.B. Swinehart, University of Nebras- t ened or endangered species (Kenny, 2008). Before reaching Lake 4,650 4,300 4,050 S 4,350 McConaughy (fig. 1), the lowest reservoir on the North Platte River, ka-Lincoln, Conservation and Survey Division, unpub. data, 2013). 5,000 4,700 4,400 4,200 385 Route US 3,950 4,650 4,200 4,350 snowmelt runoff from its mountain headwaters passes through many The data supporting the BOA interpretations presented in this report 4,000 5,050 4,250 4,050 27 Route State include information from AEM surveys completed in 2010 using 4,450 4,300 4,100 reservoirs, canal systems, and tributaries, and provides a large per- 4,100 4,150 4,100 4,100 centage of the recharge to the aquifers within the valley alluvium. The the SkyTEM system (U.S. Geological Survey Crustal Geophysics US Route 30 4,300 4,150 3,350

and Geochemistry Science Center, 2014). AEM surveys increasingly 5,000 4,150 4,150 3,450 3,400 complexities of the interaction of the groundwater and surface-water Interstate 80 4,150 3,300 4,900 4,200 have been used to characterize aquifers and their geologic setting 4,150 3,650 systems are similar in the South Platte River Basin. Understanding the 4,150 4,250 3,350 4,200 (Smith and others, 2007). The SkyTEM is a TDEM mapping plat- 4,950 4,250 3,550

complex groundwater and surface-water interactions of the North and 4,300 4200 1

7 4,250 South Platte Rivers, and Lodgepole Creek (fig. 1), allows managers form that was used to map the electrical properties of earth materials 3,600

e 4,200 3,500 3,300 t 4,400 3,800 3,700 to better regulate the limited supplies of water for all uses including from the near-surface 10 meters (m; 33 feet [ft]) down to depths of uo 4,350

4,550 4,500 4,450 R 5,000 4,250 3,900 3,750 300–400 m (984–1,312 ft; U.S. Geological Survey Crustal Geophys- e 3,250 4,850 environmental flows required for endangered species. t 4,600 4,650 a 4,300 ics and Geochemistry Science Center, 2014). tS 3,850 3,200 Primary groundwater and surface-water management concerns 4,200 3,100 For the 2010 AEM surveys, approximately 1,890 linear kilome- 4,700 4,150 3,150 include those related to water availability and water quality for human 4,750 4,900 uses, and these concerns exist both locally and downstream from ters (km; 1,174 miles [mi]) of data were collected (fig. 1). The AEM Interstate 80 4,800 4,350 the study area. Irrigation is the dominant water use, which in most surveys for the selected areas were conducted using two distinct instances is supplied by both groundwater and surface-water sources methods: block flights and reconnaissance lines. Block flights 3,700 4,950

(Carney, 2008; Luckey and Cannia, 2006). The study area covers were characterized by tightly spaced lines, uniformly spaced 220– Interstate 80

parts of western Nebraska, and typically receives between 33 and 400 m (722–1,312 ft) apart, and trended in a uniform direction. An 4,150 US Route 30 3,950 48 centimeters (cm; 13 and 19 inches [in.], respectively) of precipi- example of a block flight oriented in a north-south direction can be 4,000 5,000 4,050 3,900 located northwest of Sidney in figure 1. The second configuration 4,150 3,650 tation annually (National Oceanic and Atmospheric Administration, 4,200 4,100 5,050 3,850 2014). Supplemental water through irrigation is necessary for agricul- used widely spaced lines oriented in the direction likely to provide 4,200 3,700 3,800 3,750 ture. In the South Platte River and Lodgepole Creek drainage basins, the widest areal coverage possible for identifying the BOA. These 4,250 3,500 5,100 0 3,600

widely spaced lines were termed reconnaissance lines and provided 27 Route State dual sources (both groundwater and surface water) are used to irrigate 3,65 3,550 4,300 3,400 3,300 approximately 54,000 hectares (ha; 133,000 acres) of crops (South an initial view of the subsurface in areas where the existing geologic 3,600 3,450 US Route 385 Platte Natural Resources District, 2008). Much of the water pro- framework was poorly constrained. An example of a reconnaissance 4,500 line can be located as the single flight line trending north-south and 4,350 3,350 vided for irrigation is used and reused multiple times along its course 5,150 3,300 beginning northeast of Sidney in figure 1. Within the NPNRD, 2010 3,550 downstream. The use of dual-sources creates a complex interaction 5,200 4,400

tS US Route 138 between its source and its fate, which can make water management AEM data collection included two block flights: one west of Bayard State Route 19

ta 3,350 and another east of Bridgeport (fig. 1). Several reconnaissance lines e challenging. 4,450 5,250 4,550 4,500 3,550 3,400 3,450

Because of the multiple water uses and the consequential man- also were collected parallel to the North Platte River, and several 5,350 etuoR3,400 3,400 3,350

1 agement challenges, additional data regarding water resources are lines oriented north-south, east of Bridgeport (fig. 1). Within the 5,300 1 required for use in other studies, including the U.S. Geological Sur- SPNRD, two large block flights trending north-south were collected Interstate 76 vey (USGS) High Plains “Groundwater Availability Study” (Hous- north of Lodgepole Creek: one in western Cheyenne County and 41° ton and others, 2013; Qi, 2010; Qi and Christenson, 2010; Stanton one extending north from northwest of Sidney into the NPNRD Base from National Atlas of the United States, 2014 015 015 20 MILES Universal Transverse Mercator projection, zone 13 north, in meters and others, 2011) and the Cooperative Hydrology Study (COHYST; was collected (fig. 1). Reconnaissance lines also were collected Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83) National Geodetic Vertical Datum of 1929 (NGVD 29) 0 5 10 15 20 KILOMETERS Carney, 2008; Peterson, 2007; Luckey and Cannia, 2006). Addition- near the block flights (fig. 1). Within the TPNRD, AEM data col- Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not ally, water-resources data are actively being incorporated within the lection included the following two block flights: one along Western imply endorsement by the U.S. Government. Figure 2. Elevation of the base-of-aquifer surface for parts of the North Platte Natural Resources District and the South Platte Natural Resources District, 2014. This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary “Simulation of Groundwater Flow and Analysis of the Effects of the Canal near the South Platte River, extending into Deuel County, and between electronic plotters and between X and Y directions on the same plotter, and paper may change Water Management Options in the North Platte Natural Resources another along the North Platte River downstream from Lake McCo- size due to atmospheric conditions; therefore, scale and proportions may not be true on plots of this map. naughy (fig. 1). Two reconnaissance lines were collected north of the For more information on the USGS—the Federal source for science about the Earth, its natural and living District (NPNRD) Study,” which will be referred to hereinafter as resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS the NPNRD Groundwater Management Model (S.M. Peterson, U.S. block flight near Lake McConaughy (fig. 1). Three additional test This report is available at http://dx.doi.org/10.3133/sim3310. Geological Survey, oral commun., 2011). Refinement of the base-of- holes were drilled in Keith County to provide additional ground truth Suggested Citation: Hobza, C.M., Abraham, J.D., Cannia, J.C., Johnson, M.R., and Sibray, S.S., 2014, Base for interpreting the reconnaissance lines (James Cannia, U.S. Geo- Base of Principal Aquifer for Parts of the North Platte, South Platte, and Twin Platte Natural Resources District, Western Nebraska of principal aquifer for parts of the North Platte, South Platte, and Twin Platte Natural Resources Districts, aquifer (BOA) configuration will improve the reliability of the predic- western Nebraska: U.S. Geological Survey Scientific Investigations Map 3310, 2 sheets, http://dx.doi. logical Survey, written commun., 2012; fig. 1). ISSN 2329-132X (online) org/10.3133/sim3310. tions made with these models. One approach to deriving and refining By Christopher M. Hobza, Jared D. Abraham, James C. Cannia, Michaela R. Johnson, and Steven S. Sibray