Other sources of trouble without clear-cut present solutions are big ones. Surface runoff from both cities and rural areas, as we have seen, causes much pollution. In the country, soil conservation measures can slow it somewhat and strain out some pollutants, and augmentation of streams' flow can enhance their capacity to oxidize the wastes. But neither of these seem likely to do much to ease the longrun buildup and diffusion of persistent pollutants like pesticides, or to avert the possibility of disastrous spills. Public education and wiser restrictive legislation may help, but the only real hope in terms of these poisons appears to be that more selective and less indestructible substitutes will be found, and all promising means of biological pest control explored. Continuing programs are focused on the problem, but it continues to be serious.
Pollutive runoff from urban areas merges with the whole question of urban sewer systems, for most of it gets to the river through storm sewers. We have seen that the old-style combined sewers of the District of Columbia and Alexandria cause gross pollution when storms force open their overflow gates, and we have seen too why the approach to this problem that formerly prevailed—the arduous, hugely expensive digging up of sewers and their replacement with dual pipes to carry storm runoff and sewage separately—is no longer considered satisfactory. For the more modern dual systems also contribute much trouble through the filthy rainwater that pours out into streams from the storm system and through the accidental or illegal channeling of sanitary wastes into storm sewers.
A wholly satisfactory answer would allow runoff water as well as all sanitary wastes to be held for full treatment at a standard plant. But when we consider that at the Washington metropolis the dirty local runoff from a single storm may amount to billions of gallons, the question of where to hold it grows a bit complex, and is leading toward experimentation with such ideas as vast subterranean networks of tunnels for storage. Partial answers might come from subjecting storm and mixed flows to different and lesser kinds of treatment by micro-screens at sewer outfalls, detention and settling tanks, and filtration beds. These possibilities and others need much investigation and testing.
Then there are the multitude of nasty mysterious dribbles that help to degrade Rock Creek and can undoubtedly be found in even more profusion along every other metropolitan watercourse. Such of them as issue from storm sewers will be eliminated when a solution turns up for the problem of runoff water. The others, and they are numerous, will not. Even if the bureaucratic and political tangles that help to perpetuate them—which will be mentioned again—are dealt with, the sheer mathematics of possibility in a great city, plus the frequent difficulty of fixing responsibility, make the overall problem of these miscellaneous leaks and dribbles 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 Pollution Control Administration, the Geological Survey, the Bureau of Mines, the Soil Conservation Service, INCOPOT, and some State government bodies. Sooner or later an answer or a set of answers must come out of these efforts. But nothing presently conduces to a belief that the acid problem on the North Branch or anywhere else is going to find quick and dramatic alleviation at its sources.
Dilution of this acid pollution helps to minimize its effects, not actually neutralizing them but reducing their severity in periods of low river flow. It can be accomplished by impounding mine drainage for release only during periods of high flow, though where sources are many as on the North Branch this would be difficult. Or fresh water can be held in bulk storage for release during low flow. In helping acid conditions along the lower North Branch, therefore, the authorized Bloomington reservoir may play a part, though it will do nothing for the upper reaches of the river and the reservoir water itself will be acidic if nothing is done to neutralize it. Under INCOPOT auspices, a promising inquiry is being conducted into the possibility of instream acid removal above the reservoir, using an energy process possibly powered by electricity generated at the dam. If it works out as well as seems probable, the benefits can be huge.
