Since early 1968, the Trans-Alaska Pipeline System has been involved in surface and subsurface investigations for a pipeline originating at Prudhoe Bay and terminating at Valdez, Alaska. This route, which is slightly less than 800 mi long, crosses numerous geologic provinces, each with its own set of engineering and geologic problems.

Since work was begun, field studies have increased in scope and have advanced from preliminary route studies to more detailed surface and subsurface work. Presently, 12 drilling units are operating in the field and over 800 borings have been accomplished south of the Yukon River. Over 300 pipeline route borings have been put down north of the Yukon River and approximately 800 additional borings are planned. Drilling equipment being used is capable of being moved in rough terrain and of obtaining undisturbed frozen cores of different sizes to depths of 50 ft or more.

Many problems have been and are still being studied to further insure integrity and optimum security of the proposed pipeline. Some of the soil related problems receiving attention are (1) extent and character of permafrost; (2) solifluction; (3) landslides and avalanches; (4) stream and river scour; (5) erosion potential; (6) soil types and physical properties; and (7) seismicity.

Many techniques other than drilling have been, and are being, used or studied. Included are both infrared color and black and white aerial photography and other remote sensing techniques including thermal scanning and sidelooking radar. These techniques have been used to compile geologic maps of the entire route. In addition, seismic and acoustical sounding equipment is being evaluated.

As rapidly as information becomes available, it is utilized to finalize design parameters and determine construction requirements and controls. Because of the highly variable and complex soil and related conditions along the route, evaluation of all geologic and engineering data is a time consuming but extremely necessary process. It is anticipated that careful studies and the design now in progress will continue throughout the preconstruction and construction phases of the project. These studies, together with continued review of all data, will combine to insure a safe, pipeline system.

End_of_Article - Last_Page 2496------------