Civil and Building Engineering.

The U.S. Geological Survey (USGS) maintains a vast amount of geologic information developed in the past and is adding to their collections. Geologic and topographic maps are available for many areas of the United States. The USGS released a study (1953) consisting of six maps entitled Interpreting Geologic Maps for Engineering Purposes Hollidaysburg Quadrangle, Pennsylvania. The maps were prepared by members of the Engineering Geology and Ground Water Branches. The first two maps in the release were a topographic map and a general-purpose geologic map. The final four maps were interpreted from the first two and showed (1) foundation and excavation conditions; (2) construction materials; (3) the water supply, both surface and underground; and (4) site selection for engineering works. The text accompanying the set stated: ‘‘This set of maps has been prepared to show the kinds of information, useful to engineers, that can be derived from ordinary geologicmaps.’’ The text and the detailed information on the right side of each map
provide an excellent guide to the engineer who wishes to study an area with respect to the design and construction of foundations for a particular project.

Aerial photographs are available from the USGS and can be used to gain information on the occurrence of different types of soil (Johnson, 1951; Stevens 1951) as well as the geology of an area (Browning, 1951).
The Iowa Engineering Experiment Station (1959) has published a number of aerial photographs to illustrate their use in identifying geologic conditions such as areas of sand covered by variable amounts of flood-deposited clay near the Mississippi River; erosion of shale to create a dendritic stream pattern; sinks identifying an area of limestone; almost horizontal lava flows that are cut by streams; granite or similar rock revealed by a fine fracture pattern; stable sand dunes; and alluvial fans extending out from mountains.
The current National Atlas is available online (http: / /www.nationalatlas. gov), and maps are available under various headings, including, for example, construction materials, coal fields, geologic maps, and seismic hazards. GE-ODE (Geo-Data Explorer) is an interactive world map (http: / /geode.usgs.gov) that allows the user to retrieve, display, and manipulate multiple types of information, such as satellite images, geologic maps, and other information.

Many states have an agency that provides information on the geology of the state. In Texas, the Bureau of Economic Geology has a number of publications of value to engineers—for example, a report on the engineering properties of land-resource units in the Corpus Christi area. In addition, local groups may be able to provide useful information that will assist the engineer in planning a site study.

In view of the extensive information available from governmental agencies and the importance of such information to the design of foundations, the engineer may wish to take the time to gather appropriate information for a specific project.