A number of Australian underground mines are using empirical rating systems to characterize the ground conditions in developmental headings for geotechnical design. The two best-known rating systems are Barton’s Rock Tunnelling Quality Index (Q-System, also known as the NGI System) and Bieniawski’s Rock Mass Rating (RMR, also known as the Geomechanics Classification). As the RMR makes no allowance for high ground stresses at depth, Barton’s Q-System is more likely to be used in deep Australian underground mines. The Q-value is determined from equation 1 using the six parameters listed in table 1. The numerical value of Q ranges from 0.001 (exceptionally poor) to 1000 (exceptionally good) quality rock. <...>

The United States and the individual states have followed a legal system based on Roman law, which allows private ownership of oil and gas interests. Nevertheless, the federal and state governments control the leasing of about one-third of the oil and gas interests underlying the onshore landmass of the United States (estimated at 2.2 billion acres). They also control 100% (97% federal and 3% state) of the offshore areas of the United States (estimated at 885.6 million acres). In additional, 54 million acres of Indian lands are subject to U.S. government leasing control, and leasing rights to 44 million acres in Alaska are controlled by Alaskan natives (Mineral Management Service, 1989; Petroleum Independent, 1991). <...>

Activities in mineral deposit modeling have continued to develop on several fronts since the publication of “Mineral Deposit Models,” edited by Cox and Singer (1986). That bulletin is a collection of 87 descriptive deposit models and 60 grade and tonnage models prepared by many authors both from within and outside of the U.S. Geological Survey. The present bulletin continues that effort with the addition of new or revised models. Before these models are introduced, a review of modeling as used here is provided as well as an overview of mineral deposit modeling since the publication of Cox and Singer (1986).

Ephemeral streams, dry washes, gullies, draws and arroyos are common names for a major element of Western landscapes. By definition ephemeral streams are characterized by short periods of flow, following local and intense rainfall, and alternating with long periods in which the channel is dry (Fig.] ,2).