bbles a very tough one, not likely to be
resolved with the wave of anyone's hand. Except in visible and
well-defended watercourses like Rock Creek, they will probably persist
for a long while, even though in reduced quantities, together with some
storm runoff and some periodic discharge from combined sewers, not a
major component in estuarial pollution but a stubborn one.

A final great contaminant against which weapons are meager is acid mine
drainage. Its sources along the North Branch are numerous, as we have
seen. They have been and are being minutely studied, but present
technology does not furnish any clear and effective means of dealing
with each source individually and returning the upper river and its
branches to health, and such source rectification would be the only
really adequate answer.

Surface strip mines are deservedly notorious for the destruction of the
rugged green landscapes that are one of Appalachia's greatest resources.
Because of the public disgust they arouse, they have had a lot of
attention, and methods for conducting this sort of mining less brutally
and for reclaiming old minesites have been worked out. These methods
have notable effect on silt and acid production. Because State laws to
regulate strip mining have been generally scarce and weak, however, and
because the reclamation of old mines is very expensive, such action is
mainly more honored in the breach than in the observance.

However, strip mines produce only a tenth to a quarter of acid mine
pollution, and if they were all under control the problem would still be
huge. The active or abandoned underground mines that give out the great
bulk of the acid and other pollutive substances have so far almost
totally resisted satisfactory management, despite tremendous efforts.
Among techniques that have been tried are neutralization with limestone
and other materials, air sealing to cut down on the oxidation that helps
form the acid, sealing of mine openings to prevent outflow, mining
methods designed to prevent exposure of sulfuritic materials, and
chemical inhibition of acid generation. Regardless of the hope that some
have aroused, none has worked well and economically, and the search is
hindered by a continuing lack of data and scientific knowledge
concerning the complex physical and chemical processes by which the
pollutants are formed.

A number of agencies are researching this whole problem, among them the
Federal Water Pollutio