Some Geological Factors
In Underground Waste Disposal
NORMAN F. BILLINGS
Chief, Hydrology Division
Michigan Water Resources Commission
Lansing, Michigan
Geology has much the same importance with regard to putting
liquids into the ground as it does in taking liquids out of the ground.
In fact, waste injection is probably even more acutely dependent on
geological conditions than is the production of oil or water, because
it is so closely tied into plant location. Advantage must be taken of
conditions within the immediate vicinity of waste production as contrasted with the feasibility of going far afield in search of favorable
sites for oil or water production.
Underground geology is seldom easily appraised because it is hidden
from view and because the processes which were involved in the creation of most geological sections were highly complicated. It is not the
purpose of this paper to attempt any profound analysis of waste disposal
geology. It is proposed only to offer a generalized picture of geological
processes and conditions as they bear upon this interest, to serve as the
basis for more intensive study where indicated. In such detailed appraisals competent geological advice should always be sought.
Technically speaking, any substance which forms an appreciable
portion of the earth's crust is termed "rock" whether or not that substance happens to be hard and stonelike.
Rocks are divided into three great classes according to their origin.
These classes differ markedly in their utility for waste disposal purposes. Igneous rock is that which has congealed directly from a molten
state. It is the original source of material which makes up rocks of the
other two classes. Sedimentary rock is that which has formed through
the deposition of sediments. Metamorphic rock, the third class, consists of igneous or sedimentary rocks which have been significantly
changed from their original state by heat or pressure or both. Consolidated rock formations of any class near the surface of the earth
may contain enough fracture openings to offer some prospect for waste
disposal. That superficial type of fracture system, however, has little
practical importance because the total void space is seldom large and also
132