Miscellaneous Publication 167, Map and database of exploration drilling targets categorized by play type, North Slope and offshore Arctic Alaska, presents a compilation of discovery well and production data for oil and gas wells throughout the North Slope and offshore Arctic Alaska. Since exploration drilling began on the North Slope of Alaska in 1944, numerous oil and gas accumulations have been discovered and 18 billion barrels of liquid hydrocarbons have been produced from North Alaska through 2018. Wells have targeted five main play types: Ellesmerian clastics and carbonates (Kekiktuk, Lisburne, Ivishak, Shublik, and Sag River), Jurassic shoreface sands (Barrow, Simpson, Kugrua, Nechelik, Nuiqsut, and Alpine), Cretaceous rift sands (Walakpa, Kuparuk, Put River, Kemik, and Thomson), Brookian turbidites (Torok, Seabee, and Canning), and Brookian topsets (Nanushuk, Tuluvak, Schrader Bluff, West Sak, Ugnu, Prince Creek, and Sagavanirktok). A sixth category called 'Other' includes the remaining targets (e.g., basement, methane hydrates, and coalbed methane). This comprehensive study documents the drilling target by play type from public domain sources for 548 exploration wells on the North Slope and adjacent offshore areas in the Beaufort Sea and Chukchi Sea. The discovery well and production data for each producing pool are integrated into the study. All files are available from the DGGS website: http://doi.org/10.14509/30579.

This data set provides a collection of maps of geoecological characteristics of areas within the Beechey Point quadrangle near Prudhoe Bay on the North slope of Alaska: a geobotanical atlas of the Prudhoe Bay region, a land cover map of the Beechey Point quadrangle, and cumulative impact maps in the Prudhoe Bay Oilfield for ten dates from 1968 to 2010. The geobotanical atlas is based on aerial photographs and covers 145 square kilometers of the Prudhoe Bay Oilfield. The land cover map of the Beechey Point quadrangle was derived from the Landsat multispectral scanner, aerial photography, and other field and cartographic methods. The cumulative impact maps of the Prudhoe Bay Oilfield show historical infrastructure and natural changes digitized from aerial photos taken in each successive analysis year (1968, 1970, 1972, 1973, 1977, 1979, 1983, 1990, 2001, and 2010). Nine geoecological attributes are included: dominant vegetation, secondary vegetation, tertiary vegetation, percentage open water, landform, dominant surface form, secondary surface form, dominant soil, and secondary soil. These data document environmental changes in an Arctic region that is affected by both climate change and rapid industrial development.

This map shows the oil and natural gas wells across the United States. Oil and Natural Gas Well: A hole drilled in the earth for the purpose of finding or producing crude oil or natural gas; or producing services related to the production of crude or natural gas. Geographic coverage includes the United States (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Florida, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Montana, North Dakota, Nebraska, Nevada, New Mexico, New York, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Virginia, Washington, West Virginia, Wyoming) as well Oil and Natural Gas wells in the Canadian provinces of British Columbia and Manitoba that are within 100 miles of the country's border with the United States. According to the Energy Information Administration (EIA) the following states do not have active/producing Oil or Natural Gas Wells: Connecticut, Delaware, District of Columbia, Georgia, Hawaii, Iowa, Idaho, Massachusetts, Maine, Minnesota, North Carolina, New Hampshire, New Jersey, Rhode Island, South Carolina, Vermont, and Wisconsin. Some states do have wells for underground Natural Gas storage facilities where these have been identified they were included. This layer is derived from well data from individual states and provinces and United States Agencies. This layer is complete for the United States but further development of data missing from two Canadian provinces and Mexico is in process. This update release includes an additional 497,036 wells covering Texas. Oil and gas exploration in Texas takes advantage of drilling technology to use a single surface well drilling location to drill multiple bottom hole well connections to extract oil and gas. The addition of Well data from Texas results in the addition of a related table to support this one surface well to many bottom hole connections. This related table provides records for Wells that have more than one bottom hole linked to the surface well. Sourced from the HIFLD Open Data Portal for Energy.

The oil and gas producing regions of Alaska have nearly 45 billion barrels of oil which will be left in the ground, or ?stranded?, following the use of today's oil recovery practices. A major portion of this ?stranded oil? is in reservoirs technically and economically amenable to enhanced oil recovery (EOR) using carbon dioxide (CO2) injection. This report evaluates the future oil recovery potential in the large oil fields of the North Slope and Cook Inlet regions of Alaska and the barriers that stand in the way of this potential. The report then discusses how a concerted set of ?basin-oriented strategies? could help Alaska's oil production industry overcome these barriers.

Map B of the historical infrastructure changes for the Prudhoe Bay Oilfield for 10 dates from the initial oil discovery in 1968–2011. Aerial photos taken in 1949 and 1968 were used to define the geobotanical characteristics prior to development. Infrastructure changes were digitized from each successive analysis year (1970, 1972, 1973, 1977, 1979, 1983, 1990, 2001, and 2010). Polygon fields include nine geoecological attributes: dominant vegetation, secondary vegetation, tertiary vegetation; percentage open water; landform; dominant surface form, secondary surface form; dominant soil, and secondary soil. Secondary and tertiary variables were mapped if they covered more than 30% of a map polygon. Primary and secondary infrastructure-related change attributes were mapped for each year with imagery, and for six years (1968, 1977, 1983, 1990, 2001, 2010) primary non-infrastructure-related changes were also mapped. References Raynolds M.K., Walker D.A., Ambrosius K.J., Brown J., Everett K.R., Kanevskiy M., Kofinas G.P., Romanovsky V.E., Shur Y. & Webber P.J. (2014). Cumulative geoecological effects of 62 years of infrastructure and climate change in ice-rich permafrost landscapes, Prudhoe Bay Oilfield, Alaska. Global Change Biology, 20, 1211-1224.

Report of Investigation 2018-6, Geologic map of the Umiat-Gubik area, central North Slope, Alaska, provides a 1:63,360-scale geologic map of the hydrocarbon-bearing Umiat-Gubik area of the central North Slope, Alaska, spans approximately 2,100 km2 at the northern extent of the Brooks Range foothills fold-and-thrust belt in the Colville foreland basin. This geologic map was prepared through assimilation of field observations, aerial and satellite imagery, seismic-reflection data, and well logs. Near-surface formation picks were available or derived for most of the area's 24 exploration wells, and two cross-sections were constructed along lines of section that are constrained at depth by our interpretations of publicly available two-dimensional seismic data. The mapped area hosts exposures of Upper Cretaceous strata in the Nanushuk, Seabee, Tuluvak, Schrader Bluff, and Prince Creek Formations, constituting an approximately 2-km-thick succession that crops out discontinuously in the low-relief, tundra-mantled region. This part of the siliciclastic Brookian megasequence stratigraphy comprises principally shallow-marine deposits. Our work benefits from and reflects recent sequence-stratigraphic advances that better constrain how this part of the Colville basin continued to fill by a northeastward prograding clastic wedge during Late Cretaceous time, with the exposed stratigraphy recognized as basin-scale topset units. A series of east- to east-southeast-trending, km-scale wavelength, gentle folds are mapped in the area. Anticlines are locally breached by thrusts and interpreted to be folded above faulted and penetratively deformed mid-Cretaceous Torok Formation. Undeveloped, sub-commercial (as of this writing) petroleum accumulations occur along doubly plunging anticlinal traps at three long-recognized fields in the map area: Umiat (mostly oil), Gubik (gas), and East Umiat (gas). The Umiat oil field structural culmination is modified by thrust faults that breach the surface, and the East Umiat gas field is associated with a north-dipping back-thrust that is evident in seismic data and cuts across the Upper Cretaceous stratigraphy; thrust faults near the Gubik gas field lie within and below the Torok Formation. Various interpretations have previously been published for some of the area's structures, with important implications for petroleum trap geometries in the gas-prone foothills region. We present new data and interpretations that support the inference of a principal, south-dipping thrust fault that breaches the north limb of Umiat anticline near Umiat. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/30099.

Arctic Vegetation Archive - Alaska: Prudhoe Bay Vegetation Plots. The vegetation of the Prudhoe Bay area was described and mapped by D. A. Walker for doctoral thesis at the University of Colorado, Department of Environmental, Population and Organismic Biology (Walker 1981). The study was initiated in 1973 under the U.S. Tundra Biome portion of the International Biological Program (IBP) and is part of U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory (CRREL) research activities conducted under DA Project 4A161102AT24. Results were also included in CRREL report 85-14 (D. Walker 1985). This study is important because it came 5 years after the discovery of the Prudhoe Bay Oilfield and includes baseline vegetation and environmental data of the Prudhoe Bay Oil Field. Data from eighty-nine subjectively located study plots are presented. Plots occur in forty-three plant communities and 4 broad habitat categories including: 1) dry tundra (including gravelly pingos, high-centered polygons, frost scars, dry river sands and gravels, sand dunes, river bluffs, coastal beaches, and early melting snowbeds (24 plots), 2) moist tundra (including moist nonacidic tundra, acidic coastal tundra, snowbeds, moist stream banks, bird mounds and animal dens, and moist sandy tundra (33 plots), wet tundra (including wet nonacidic tundra, wet acidic tundra, and wet saline coastal tundra) (22 plots), aquatic tundra (including shallow and deep water habitats, and (10 plots). Plots were permanently marked in a corner of the first square meter of the 1 m by 10 m plots, and in a corner of the 1 square meter plots. Species and environmental data (including soil physical variables, subjective site assessments, and active layer depths) were collected in the field and soil samples were brought back to the lab for the chemical assessments. Approximate GPS coordinates were obtained for all but 2 plots by the author in 2013 utilizing aerial photographs of the study area in conjunction with Google Earth. These data were subsequently used in several reports and publications listed below. References: Raynolds, M. K., Walker, D. A., Ambrosius, K. J., Brown, J., Everett, K. R., Kanevskiy, M., Kofinas, G. P., Romanovsky, V. E., Shur, Y., and P. J. Webber. 2014. Cumulative geoecological effects of 62 years of infrastructure and climate change in ice-rich permafrost landscapes, Prudhoe Bay Oilfield, Alaska. Global Change Biology 20:1211-1224. Walker, D. A., K. R. Everett, P. J. Webber, and J. Brown (Editors). 1980. Geobotanical Atlas of the Prudhoe Bay Region, Alaska. CRREL Report 80-14. U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, USA. Walker, D. A. 1981. The vegetation and environmental gradients of the Prudhoe Bay region, Alaska. Dissertation. University of Colorado, Boulder, CO, USA. Walker, D. A. 1985. The vegetation and environmental gradients of the Prudhoe Bay region. CRREL Report No. 85-14. U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, USA. Walker, D. A., and W. Acevedo. 1987. Vegetation and a Landsat-derived Land Cover Map of the Beechey Point Quadrangle, Arctic Coastal Plain, Alaska. CRREL Report 87-5. U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, USA. Walker, D. A., and K. R. Everett. 1991. Loess ecosystems of northern Alaska: regional gradient and toposequence at Prudhoe Bay. Ecological Monographs 61:437–464. Webber, P. J., and D. A. Walker. 1975. Vegetation and landscape analysis at Prudhoe Bay, Alaska: a vegetation map of the Tundra Biome study area. Pages 81–91 in J. Brown, editor. Ecological Investigations of the Tundra Biome in the Prudhoe Bay Region, Alaska. Biological Papers of the University of Alaska, Fairbanks, Alaska, USA.

This map covers most of the Prudhoe Bay Oilfield on the North Slope of Alaska that was under development in 1980, covering 145 km^2. The map synthesizes work done for the US Army Corps of Engineers CRREL, the International Biome Program, and the UNESCO MAB Project 6. The mapping was based on aerial photographs taken in 1973 at a scale of 1:6000. The maps are thus a static representation of a type of arctic tundra at a time when only relatively minor terrain disturbance had occurred. It can be used as a baseline against which further natural and human-induced changes to the landscape can be measured. A geoecological approach was used in the mapping of landforms (12 units as well as linear mapping of steep embankments, undercut river banks, excavated areas and streams), soils (7 units) and land cover (29 natural vegetation units and 8 disturbed units). References Walker, D. A., K. R. Everett, P. J. Webber, and J. Brown. 1980. Geobotanical Atlas of the Prudhoe Bay Region, Alaska. US Army Corps of Engineers, CRREL Report 80-14.

Outer Continental Shelf Oil and Natural Gas WellsThis feature layer, utilizing National Geospatial Data Asset (NGDA) data from the Bureau of Ocean Energy Management (BOEM), displays oil and natural gas wells found in the United States' federal Outer Continental Shelf (OCS) waters. According to BOEM, these are "existing wells drilled for exploration or extraction of oil and/or gas products. Additional information includes the API (American Petroleum Institute) number, well name, well type, spud date, and well status. Only wells found in federal Outer Continental Shelf (OCS) waters are included".OCS Oil and Natural Gas WellsData currency: This cached Esri federal service is checked weekly for updates from its enterprise federal source (OCS Oil and Natural Gas Wells) and will support mapping, analysis, data exports and OGC API – Feature access.NGDAID:Alaska Region: 53 (Outer Continental Shelf Oil and Natural Gas Wells - Alaska Region NAD 83)Gulf of Mexico Region: 54 (Outer Continental Shelf Oil and Natural Gas Wells - Gulf of Mexico Region NAD 27)Pacific Region: 55 (Outer Continental Shelf Oil and Natural Gas Wells - Pacific OCS Region NAD 83)OGC API Features Link: (Outer Continental Shelf Oil and Natural Gas Wells - OGC Features) copy this link to embed it in OGC Compliant viewersFor more information: National OCS Oil and Gas Leasing Program; Energy EconomicsFor feedback please contact: Esri_US_Federal_Data@esri.comNGDA Data SetThis data set is part of the NGDA Utilities Theme Community. Per the Federal Geospatial Data Committee (FGDC), Utilities is defined as the "means, aids, and usage of facilities for producing, conveying, distributing, processing or disposing of public and private commodities including power, energy, communications, natural gas, and water. Includes sub themes for Energy, Drinking water and Water treatment, and Communications."For other NGDA Content: Esri Federal Datasets

The Well Log Tracking System (WELTS) contains water well construction and lithologic information submitted to the Division of Mining, Land and Water, Alaska Hydrologic Survey by water well contractors as required per Alaska State Statute 41.08.020(b4) authority delegated to the Alaska Hydrologic Survey per Department Order 115, require of water well contractors, the filing with it of basic water and aquifer data normally obtained, including but not limited to well location, estimated elevation, well driller's logs, pumping tests and flow measurements, and water quality determinations. Additionally, per Alaska Administrative Code, Title 11 Natural Resources, Part 6 Lands, Chapter 93 Water Management, Article 2 Appropriation and Use of Water 11 AAC 93.140(a):

For a drilled, driven, jetted, or augered well constructed, the water well contractor or a person who constructs the well shall file a report within 45 days after completion with both the property owner and the department. The report must contain the following information as applicable: (1) the method of construction; (2) the type of fluids used for drilling; (3) the location of the well; (4) an accurate log of the soil and rock formations encountered and the depths at which the formations occur; (5) the depth of the casing; (6) the height of the casing above ground; (7) the depth and type of grouting; (8) the depth of any screens; (9) the casing diameter; (10) the casing material; (11) the depth of perforation or opening in the casing; (12) the well development method; (13) the total depth of the well; (14) the depth of the static water level; (15) the anticipated use of the well; (16) the maximum well yield; (17) the results of any well yield, aquifer, or drawdown test that was conducted; (18) if the water well contractor or person who constructs the well installs a pump at the time of construction, the depth of the pump intake and the rated pump capacity at that depth. (b) When the drill rig is removed from the well site, the well must be sealed with a sanitary seal and a readily accessible means provided to allow for monitoring of the static water level in the well. (c) A hand-dug well that is permanently decommissioned shall be filled by the land owner to a point 12 in above the existing ground level with well-compacted impermeable material. (d) A well, other than a hand-dug well, that is permanently decommissioned by the owner of the well must comply with the requirements of 18 AAC 80.015(e) . (e) If the department believes that an encounter of oil, gas, or other hazardous substance is likely to result from well drilling, the department will notify the Alaska Oil and Gas Conservation Commission, and the provisions of AS 31.05.030 (g) may apply. (f) The department will notify the Department of Environmental Conservation of any permanently abandoned well that may contaminate water of the state under the provisions of 18 AAC 80. (g) Information required by (a) of this section is required for any water well that has been deepened, modified, or abandoned, and for any water supply well or water well that is used for monitoring, observation, or aquifer testing, including a dry or low-yield water well that is not used. This data characterizes the geographic representation of well logs within the State of Alaska contained in the Well Log Tracking System. The shape file was developed using well location information submitted with well logs. Well locations represented by a gold star symbol, represent the approximate (centroid) location, and may represent a cluster of wells. Well locations represented by a blue circle symbol, represent wells submitted with latitude and longitude coordinates. Each feature has an associated attribute record, including a Well Log Tracking System identification number which serves as an index to case-file information. Those requiring more information regarding WELTS should contact the Alaska Department of Natural Resources Alaska Hydrologic Survey directly.

Extensive oil and gas activity has occurred in the Arctic, primarily land-based, with Russia extracting 80% of the oil and 99% of the gas to date (AMAP 2008). Furthermore, the Arctic still contains large petroleum hydrocarbon reserves and potentially holds one fifth of the world’s yet undiscovered resources, according to the US Geological Survey (USGS 2008) (Fig. 14.4). While much of the currently known Arctic oil and gas reserves are in Russia (75% of oil and 90% of gas; AMAP 2008), more than half of the estimated undiscovered Arctic oil reserves are in Alaska (offshore and onshore), the Amerasian Basin (offshore north of the Beaufort Sea) and in W and E Greenland (offshore). More than 70% of the Arctic undiscovered natural gas is estimated to be located in the W Siberian Basin (Yamal Peninsula and offshore in the Kara Sea), the E Barents Basin and in Alaska (offshore and onshore) (AMSA 2009). Associated with future exploration and development, each of these regions would require vastly expanded Arctic marine operations, and several regions such as offshore Greenland would require fully developed Arctic marine transport systems to carry hydrocarbons to global markets. In this context, regions of high interest for economic development face cumulative environmental pressure from anthropogenic activities such as hydrocarbon exploitation locally, together with global changes associated with climatic and oceanographic trends. Conservation of Arctic Flora and Fauna, CAFF 2013 - Akureyri . Arctic Biodiversity Assessment. Status and Trends in Arctic biodiversity. - Marine ecosystems (Chapter 14 - page 501). Figure adapted from the USGS

description: In 1988, the U.S. Fish and Wildlife Service (Service) funded a contaminants project with the following objectives : 1) conduct a reconnaissance-level field inspection of abandoned oil and gas exploration sites on the Alaska Peninsula/ Becharof National Wildlife Refuge, 2) identify and map abandoned physical remains of oil exploration activities and 3) collect soil samples for organochlorine, petroleum, and metal analysis. During the field survey, several sites warranting further study were identified. One such site was Bear Creek Well No., drilled as an exploration well by the Humble Oil and Refining Company (now Exxon) in the 1950s and abandoned for lack of commercial potential. The well pads still contained a large amount of wood and metal from buildings and machinery used during the exploration drilling. In early 1990, Refuge Manager Ronald Hood proposed to the Exxon officials involved in the Exxon Valdez oil spill cleanup that Exxon remove both the debris at the Bear Creek Well No. 1 site and the old culverts under the access road. Exxon complied, removing the debris and most of the culverts during 1990 and 1991. In 1993 Service personnel performed soil sampling at the well pads to identify any residual contamination left after Exxon's abandonment of the site. Some petroleum and metal residues of concern were found on the pads. Also, the remains of the reserve pit were found to be eroding into a stream which flows into Bear Creek, an important salmon spawning stream. The reserve pit residues contained significant amounts of barium (identified in an earlier report), petroleum, zinc, and a trace of polychlorinated biphyenls. It is recommended that this site be investigated further to determine the extent of the contamination related to the well pads and the reserve pit and the ecological risk associated with this site.; abstract: In 1988, the U.S. Fish and Wildlife Service (Service) funded a contaminants project with the following objectives : 1) conduct a reconnaissance-level field inspection of abandoned oil and gas exploration sites on the Alaska Peninsula/ Becharof National Wildlife Refuge, 2) identify and map abandoned physical remains of oil exploration activities and 3) collect soil samples for organochlorine, petroleum, and metal analysis. During the field survey, several sites warranting further study were identified. One such site was Bear Creek Well No., drilled as an exploration well by the Humble Oil and Refining Company (now Exxon) in the 1950s and abandoned for lack of commercial potential. The well pads still contained a large amount of wood and metal from buildings and machinery used during the exploration drilling. In early 1990, Refuge Manager Ronald Hood proposed to the Exxon officials involved in the Exxon Valdez oil spill cleanup that Exxon remove both the debris at the Bear Creek Well No. 1 site and the old culverts under the access road. Exxon complied, removing the debris and most of the culverts during 1990 and 1991. In 1993 Service personnel performed soil sampling at the well pads to identify any residual contamination left after Exxon's abandonment of the site. Some petroleum and metal residues of concern were found on the pads. Also, the remains of the reserve pit were found to be eroding into a stream which flows into Bear Creek, an important salmon spawning stream. The reserve pit residues contained significant amounts of barium (identified in an earlier report), petroleum, zinc, and a trace of polychlorinated biphyenls. It is recommended that this site be investigated further to determine the extent of the contamination related to the well pads and the reserve pit and the ecological risk associated with this site.

Vegetation and land cover for Beechey Point 1:250,000-scale topographic quadrangle. Derived from a single Landsat MSS scene. Printed map: AK Vegetation and Land Cover Series l-0211. Digital raster data set also available. Seven categories. Data stored as 50 meter UTM-referenced pixels.

Information available as map or digital data set. Map unit coverage within each township printed on back of map. Map printed using Scitex laser printer. Documentation - Walker, D.A. and W. Acevedo, 1987, Vegetation and a Landsat-derived Land Cover Map of the Beechey Point Quadrangle, Arctic Coastal Plain, Alaska, U.S. Army Cold Regions Research and Engineering Laboratory, CRREL Report 87-5, 63 p.

The purpose of the cell map is to display the exploration maturity, type of production, and distribution of production in quarter-mile cells in each of the oil and gas plays and each of the provinces defined for the 1995 U.S. National Oil and Gas Assessment.

Cell maps for each oil and gas play were created by the USGS as a method for illustrating the degree of exploration, type of production, and distribution of production in a play or province. Each cell represents a quarter-mile square of the land surface, and the cells are coded to represent whether the wells included within the cell are predominantly oil-producing, gas-producing, both oil and gas-producing, or dry. The well information was initially retrieved from the Petroleum Information (PI) Well History Control System (WHCS), which is a proprietary, commercial database containing information for most oil and gas wells in the U.S. Cells were developed as a graphic solution to overcome the problem of displaying proprietary WHCS data. No proprietary data are displayed or included in the cell maps. The data from WHCS were current as of December 1990 when the cell maps were created in 1994.

Oil and gas plays within province 2 (Central Alaska) are listed here by play number, type, and name:

Number Type Name 201 conventional Central Alaska Cenozoic Gas 202 conventional Central Alaska Mesozoic Gas 203 conventional Central Alaska Paleozoic Oil 204 conventional Kandik Pre-Mid-Cretaceous Strata 205 conventional Kandik Upper Cretaceous and Tertiary Non-Marine Stata

Regional boundaries established for the purpose of preparing regional master oil and hazardous substance discharge prevention and contingency plans. Product of the Alaska Department of Environmental Conservation's Spill Prevention and Response Division. This layer was developed by Unioning school district polygons per the descriptions in 18 AAC 75.495.

A vegetation/land cover raster digital data set for the entire National Petroleum Reserve in Alaska (NPR-A) was generated from Landsat multispectral data sets. Included are eleven categories of vegetation and land cover which are derived from all or portions of 10 Landsat MSS scenes. The data set covers all or part of thirteen 1:250,000-scale topographic quadrangles. Data are stored in 50 meter pixels and registered to a UTM base. A full NPR-A mosaic as well as the 1:250,000 topographic series. Data are available in two forms: a digital mosaic of (1) the entire NPR-A coverage, split into two pieces each and registered to a separate UTM zone, or (2) for each 1:250,000-scale topo quadrangle area within the NPR-A. This file is too large to remain online. It is stored on magnetic tape at Moffett Field, CA.