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To help save the creek and its parks and to stimulate a better kind of development of the rest of its basin, citizens formed a watershed association under Soil Conservation Service auspices and brought about the construction of two small upstream reservoirs to control flooding—with results noted in the precedingchapter—and to collect silt. They sought to promote better land use as well, for the reservoirs' effectiveness is obviously dependent on their not filling up quickly with an excess of sediment. Better land use around a city depends on zoning and other legal devices to regulate the density and distribution of construction, and on controls over the way land is shaped, and a sharp conflict developed between the watershed's defenders and the Council of Montgomery County, Maryland, in office at that time, whose rezonings in favor of standard massive suburbanization and whose failure to enact sediment-control ordinances threatened the whole effort. Rock Creek has many friends, and their subsequent fight for its salvation has had good effect, though much remains to be done.
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However, Rock Creek is only one of many metropolitan streams that need protection, both for their own sake and for that of the estuary. Some are getting it—in the preceding chapter we noted the happy example of Pohick Creek in Virginia, where whole watershed planning is being accomplished almost from scratch, before development. But many more are being ruined by the steady advance of standard urban sprawl.
Thus the main cause of urban silt is faulty or nonexistent or powerless land planning, and the problem merges with the whole question of landscape preservation. The ecological principles involved in good practical land planning—the distribution of uses based on what land and water can take without being degraded and causing silt, flooding, and downstream pollution—are the same basic principles that lead to scenic beauty and a decent human environment. This is a subject we will explore in more detail when we arrive at considering the landscape as a whole, but for now it may be worthwhile to note that insofar as urban erosion and silt stem from decisions of political agencies inclined to subjugate well-known good land use principles to speculative pressures, expediency, and other things, their origin is political and economic.
Organic materials are pervasive enough in the upper estuary that during periods of even normal flow their decay pulls oxygen levels down. Under usual conditions this B.O.D. grows worse and worse downstream and reaches a peak in the neighborhood of Mount Vernon, though its effects continue to be felt below. Fish kills among the rugged resident species that predominate in these reaches of the river are not uncommon, the shoreline windrows of deceased carp andperch periodically adding their essence to what metropolitans have come to accept as the Potomac's normal summer smell. And along with the organic materials are heavy concentrations of bacteria.
The organic and bacterial load enters the estuary from many sources, most of them local, for only a little of this material comes down from the upper river. A significant amount of it issues from the network of small urban watercourses like Rock Creek. Many of these were covered over as storm sewers or troughed in concrete long ago, but they continue to serve their age-old function of draining the lands they traverse, even if through cast-iron gratings.
A good bit of the organic load in these tributaries consists of raw human waste, incongruous and particularly obnoxious around a modern city. The bulk of it is released in periodic surges when local rainstorms overload the old-fashioned combined sewer systems of the District of Columbia and Alexandria. In dry weather these systems send both collected sanitary wastes and street drainage down to the cities' respective treatment plants, but during storms when street drainage is heavy the sewers' capacity is exceeded and overflow gates gush mixed stormwater and sewage out into the streams, which carry it to the estuary.
In the suburbs, more modern separate storm and sanitary sewers are the rule, but they too have some problems of a kind we noted in relation to the upper river. Investigations on Rock Creek revealed steady dribbles of raw sewage entering the creek or itstributaries from a large number of storm-sewer outfalls and other places. Partly these flow from malfunctioning individual septic systems in outlying areas, surreptitious connections of house sanitary sewers to the storm system, breaks and leaks in sanitary sewers, and such things. Partly too they seem to come from the fact that some sanitary sewers are having to carry more sewage than they were designed to handle, so that their overflow valves leak more or less constantly into the storm sewer system. The capacity of sewage collection systems is related to planning. If a pipe is laid down to a fringe area where county zoning maps indicate only limited development is going to be permitted, its size is gauged to that kind of development. But if the zoning is changed later and three times as many houses are hooked up to the line as were originally envisioned, trouble results. Rock Creek is heavily affected by such sewage, and the chances are that the situation is much worse on many other urban drainways, for their longstanding degradation or sheer disappearance from view has lost them the alert defenders who watch over Rock Creek in its pleasant valley.
Out of the storm sewers whether combined or separate, off of the roads and streambanks and hillsides, down the urban tributaries or directly overland into the estuary, comes still another big jolt of organic and bacterial pollution every time there is a heavy rain. This is surface runoff, the washings of the street and parks and sidewalks and rooftops. Besides debris, it contains vast hordes of bacteria and many kinds of organic oxygen-demanding substances, of which animal droppings are only one easily definable example. Around a city the size of the Washington metropolis, this runoff would constitute a worrisome pollution problem even if the matter of sanitary wastes were thoroughly in control.
Ships
Ships and large boats in the estuary, in accordance with an unfortunately persistent nautical tradition, generally discharge toilet wastes and garbage directly into the water on which they float. Some of these are coastal or transoceanic vessels, both commercial and naval. Many more belong to the fleet of pleasure boats which have been increasing at Washington despite the water's unpleasant state to which they add their bit, degrading the element that is supposed to provide the enjoyment for which the boats were built. It is not a problem limited to the Potomac estuary, but widespread these days and the focus of much concern among public health and pollution control authorities, conservationists, and the boat and marina industries themselves.
Around the various marinas to be found along metropolitan shores—several of them Federally owned—sanitary facilities are generally skimpy, and no regulations govern the discharge of wastes from boats. Since individual marinas may berth as many as 600 or 700 craft, a great many of them in daily use during the recreation season and some inhabited as dwellings the year round, summer conditions that frequently prevail around these places are not to be described in polite terms.
Less visible at the point of origin thoughnot in its ultimate effects is the huge organic load that comes to the estuary in the effluent of local sewage treatment plants, estimated at possibly 300 to 350 million gallons per day. There are many smaller plants strung out down both shores of the upper estuary, but four larger ones handle the bulk of metropolitan sewage. Of these, three—the main plant at Blue Plains in the District, the Alexandria plant, and the Fairfax County Westgate plant—furnish secondary treatment, and the fourth, the Arlington County plant on Four Mile Run, is on the verge of putting new secondary facilities into operation.
Yet the same problem of plant operation that exists in the upper Basin also rears its head here. A casual boat ride down the shoreline with a few excursions up tributary creek-mouths demonstrates that many of the smaller plants, including a number of Federal ones, are emitting a very low quality of effluent, and this is borne out by sanitary surveys. The proliferation of such small plants around cities and elsewhere is a headache to sanitary authorities, for their very size and numbers create a probability of trouble. Much effort is going into eliminating them and channeling the wastes they receive into the larger plants.
But the large plants themselves at this point are a much bigger part of the problem; on the basis of sheer volume, their contribution to estuarial pollution dwarfs all others. The Blue Plains plant is by far the largest of the four, handling wastes from about 1.4 million people in Washington and outlying areas on both sides of the river. By the terms of a conference convened in 1957 by the PublicHealth Service to investigate the sanitary state of the Potomac at Washington, the District committed itself to maintain 80% efficiency of treatment at this plant, which was then brand new. Last year, ten years afterward, the most generous recent calculation of the efficiency there was 62%, and some qualified observers expressed a conviction that Blue Plains had never consistently functioned at much over 50%—in other words, it had been returning to the estuary unassimilated organic materials equivalent to the raw discharges of a population of roughly 500,000 to 700,000 people each day. Nor do these figures include a great deal of sludge that has been flushed on into the river when digesters have failed to function properly, or the plant's frequently inadequate use of chlorination against bacterial pollution and odors. Since the same 1957 conference required of the other metropolitan jurisdictions only that they do equally as well as the main plant in quality of treatment, they have clearly not been obligated to superhuman effort.
Filtration bed
Criticism of Blue Plains is in part criticism of ourselves. Because of the distinctive relationship between the District and the Federal Government, the District's treatment plant is in a sense a Federal installation, funded through Congress and with more direct links to Federal water quality agencies than any other big municipal plant in the country. The number of people the plant serves has, of course, increased greatly in the past ten years. It may have been, as has been claimed, somewhat underdesigned to begin with, and it undoubtedly needs expansion now. Yet a rather substantial improvement in the quality of treatment there in quite recent months, mainly under the stimulus of this planning effort and the present surge of interest in the Potomac, indicates that had emphasis on lowoperating costs been subjugated to pride in results, the present plant could long ago have been made to function reasonably well and the estuary would have had to cope with a much lighter load of wastes.
The truly spectacular manifestation of pollution in the metropolitan Potomac is the periodic growth of algae there in summertime. When conditions are right—when sun, summer temperatures, low inflows from the river above, and a heavy concentration of nitrate and phosphate nutrients all combine to make of the upper estuary one vast inspired pool of fertility—the whole surface of the river may be covered with a thick bright emerald mat, and boats that pass at speed leave wakes of green instead of white. The infestation may extend downstream for thirty or forty miles, in various degrees of concentration, and even if the water were bacterially safe this "bloom," as it is called, would prohibit its recreational use by anyone without a strong stomach. It further disrupts aquatic life balances, and periodically dies and decays aromatically, setting off whole new cycles of oxygen depletion, fish kills, stink, and fertilization.
The problem is one of fertility, of course, and stems from the huge quantities of nitrogen and phosphorus perennially present in the water. Some of this comes down from the upper river—where, as we noted, much of it derives from land runoff—but by far the greatest part of it originates at the metropolis and enters the river through the effluent of waste treatment plants. Efficiency of operation has hardly anything to do with it, for even the best standard treatment has little effect on nutrients.
Eutrophication is the scientific name of this kind of overenrichment. It is occurring in many places, Lake Erie being the best-known single example in this country. Though its causes are mainly known, the process itself is still not fully understood, particularly in regard to the function of nitrogen and the way it works. But the other key element, phosphorus, has been more amenable to study and to possible action. It occurs in body wastes, in artificial fertilizers, as a by-product of natural decay, and very notably in detergents. Some eight tons of it are released into the estuary each day from the treatment plants in addition to the undetermined but much smaller amounts arriving from upriver, and the usual overall accumulation is enough to make the river's phosphorus content exceed that considered desirable all the way from Theodore Roosevelt Island to Quantico, Virginia, and below, which represents the general extent of the summertime "blooms."
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Dilapidation begets disrespect, and the abused and often repellent waters of the upper estuary are undoubtedly subjected to much additional miscellaneous pollution by people who believe perhaps that a little more cannot possibly matter. Again, Federal or Federally connected institutions have not been setting the best possible example, and there are many of them around the capital city. Unwarranted waste discharges of one kind or another have been traced to most of the military installations fronting the river, to military hospitals, to government heating plants, to the National Zoo, to National Parks, and to similar Federal sources including the marinas already mentioned. In most cases, measures are now being taken to eliminate these discharges, but it is a commentary on the complexity and difficulty of the whole task of dealing with pollution that at the level of government where real concern with the problem has been acute for a decade or more, and furthermore at and around the very seat of that government, such practices should have persisted this long.
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Junk and debris of all descriptions infest the metropolitan river, floating about, washing onto the shores, poking up stolidly here and there out of mudflats. Most items in a dreary inventory that might be compiled would turnout to be something that was discarded somewhere it didn't belong by someone who did not want to go to the trouble to put it where it did belong. Therefore, the main source is undoubtedly simple disregard for the sensibilities and rights of others, multiplied and complicated by the immense number of people in the metropolis and the wide territory they occupy. In our study of Rock Creek last year, some powerful subsidiary reasons for the prevalence of debris turned up also, ranging to streetcleaning methods and the inconvenient hours kept by some public dumps where citizens have to carry their larger trash. Metropolitan problems are seldom simple, and many of them in one way or another manage to inflict a part of their complexity on the river at the national capital, which is sad but possibly appropriate in a time like the present.
Downriver from the main effects of the metropolitan complexities, the widening brackish and salt portions of the Potomac estuary form a generally healthy body of water, though changes loom as the metropolis moves inexorably outward from its center and as hitherto remote Tidewater areas are brought more and more under the influence of modern ways of being. Localized problems of pollution point to general dangers that will certainly materialize unless safeguards are set up in time, for estuaries are delicate, immensely productive, and still somewhat mysterious aquatic environments that have been and still are too much taken for granted.
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Rapid human intrusion on estuaries duringthe past twenty years has been making apparent their phenomenal value in a natural condition. Vulnerable, attractive to diverse interests that work their beds for sand and gravel and fill in their marshes for development and casually pollute them, they have recently been called America's most endangered natural habitat. They are almost unbelievably fertile places, with involved biological cycles that can convert the fertility into usable food at rates per acre far exceeding those of the finest farm land; in terms of money, one recentset of experiments indicates the possibility of attaining an annual shellfish production on tended beds worth over $26,000 an acre.
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Furthermore, aside from the direct harvest of this wealth from estuaries each year by commercial and sport fishermen, these in-between waters make an indispensable contribution to the entire Atlantic coastal fishery, an industry worth a billion dollars a year. The reason for this is that at least 70 percent of coastal fishes spend some essential part of their life cycle within an estuary—spawning there, or passing through on their way to spawn in running fresh streams, or moving in as fry from the rivers or the open sea to find a "nursery" in one of the varied estuarine habitats—bays, marshes, sandy shorelines, mudflats, tidal creeks, or weed beds.
The oysters from the famous beds in the Saint Mary's River off of the lower Potomac are mainly condemned as unfit for consumption because of local sewage pollution, and these beds are not the only unfit ones, for towns and resorts in the region have been growing and sanitary facilities have not been keeping pace. Already some arms of the superb natural harbors formed by the tributary creeks are noxious with discharges from boats at big marinas, and gravel dredging is stirring up silt to smother bottom life, including shellfish. As Tidewater agriculture revives and modernizes, pesticides and artificial fertilizers are coming to be as much a part of the scene there as in other farming regions, and may be expected to influence the estuary—in fact, they undoubtedly already are doing so in subtle ways with effects not yet apparent.
Yet most of this part of the river is still beautiful and continues to yield good harvests of seafood. The Potomac River Fisheries Commission has been alert to obvious dangers and has moved against them where its powers have permitted, and natives of the area are increasingly alert in protecting the estuary. Many of them depend on it for a living, most are oriented toward it for their pleasures, and until lately a good many of them counted on it for transportation. In a number of different ways, it matters in their lives. And that fact offers some hope for the future, especially if it is fostered and strengthened by overall protective measures.
Two main general approaches to water quality improvement exist: treatment of pollution at its source or occasionally after it has entered a stream, and augmentation of the stream's flow to help it assimilate loads of waste beyond its natural capacity. A third possibility in certain situations is the diversion of wastes out of a stream's drainage entirely. In practice, these methods can be varied and combined in any number of ways to fit a need.
To take the last one first, diversion of whole wastes as received from their sources is a total and dramatic means of coping with a pollution problem stemming from collectable wastes, but it often has disadvantages. One of these, of course, is the possibility that the pollution problem may be simply transplanted elsewhere—that the water in which the wastes eventually end up will suffer. Anotheris loss of water from the stream system. If, as is usual, a town gets its water out of the local river or a tributary and does not give it back after use—preferably well cleaned up—other users downstream are not going to have as much water available to them, and the essential processes and ecology of the river itself may suffer.
The only place such wholesale diversion of wastes has been seriously considered in the Potomac Basin is at metropolitan Washington, whose sewage could feasibly be piped across Chesapeake Bay and the Delmarva peninsula and well out into the Atlantic—possibly, as has been suggested, in combination with sewage from Baltimore. It would be a permanent means of disposal, but very expensive in terms of both investment and operating costs. Furthermore, though in the estuary no downstream users would suffer a loss of water supply, the water content in metropolitan sewage has at times risen as high as 80 percent of the flow of the river above the upstream intakes. The effects of such a subtraction of fresh water on the estuary itself—changes in flow, and in the penetration of salt water upriver, with an inevitable alteration in valuable fisheries and the whole balance of aquatic life established through millennia—could easily turn out to be disastrous.
Standard treatment of pollution at its source consists of the primary and secondary processes we have glanced at, sometimes adjusted to specific industrial wastes. It has to be brought up to peak efficiency along the Potomac, for this is a "known factor" of greatsignificance. Plants can and must be improved physically where necessary, and qualified operators provided for them. Collection systems have to be improved or enlarged in many places. Diminutive plants, doomed to inefficiency by their size and the financial impossibility of hiring expert workers for them, need to be eliminated in favor of regional waste collection and treatment facilities, which are quite feasible, particularly in the watershed units of the upper Basin.
Even so, it has emerged clearly to view in this Potomac study that standard treatment alone is no longer an answer in areas of concentrated or continuous population and industry, where the leftover wastes and the nutrients in the effluent from even well-run standard plants can often add up to a killing load for water.
Total diversion of treatment plant effluents is sometimes possible, but is subject to the same objections that apply to total diversion of untreated sewage—possible pollution of the receiving water (such as Chesapeake Bay or the lower Potomac estuary, both of which have been suggested and considered for Washington's effluent) and the alteration of hydrological and ecological conditions. Modified forms of effluent diversion, however, may offer more promise.
Effluents from maximum standard treatment processes, for instance, can be injected into underground strata as recharge water for aquifers—a process mentioned earlier as one alternative in the emerging package of water supply techniques—or may be spread over the surface of large areas of rural landwhere they serve as irrigation water and fertilizer combined, as well as soaking down into underlying aquifers. For large scale, sustained use, both of these practices still offer some technical difficulties—algae buildups that interfere with percolation, odor problems, limited aquifer capacities, the large amounts of land required for spreading, the effect of rain and freezing weather, and such things. And where the aquifers in question do not feed the original source stream system, a big subtraction is again involved. But for certain conditions in certain places these problems are undoubtedly going to be worked out.
A more modest but highly useful modification of effluent diversion is the spacing of treatment plant outfalls at intervals for a long distance downstream from a treatment plant. If nutrient and organic loads are not tremendously heavy in relation to the size of the receiving stream, this procedure can help to assure that no one stretch gets too strong a dose of them. It is likely to find good use in the Potomac and elsewhere, though only as an adjunct to the best available treatment.
"Advanced treatment" and "tertiary treatment" are becoming common terms nowadays. They refer to any of a considerable array of additional or intensified processes aimed at attaining levels of purification that would have cost an impossible price a few years ago. Most of them are still experimental and often still expensive, and they involve everything from filtration through powdered coal to flash distillation, with still others in prospect. Some bypass conventional treatment and deal with whole raw wastes. More build on conventional treatment and are designed to remove nutrients and residual organic material from its effluents. Of these latter approaches, at least one, involving lime precipitation and other processes to remove nearly all phosphorus and most remaining organic material, is nearing a stage of development and economy that may warrant important use. It will be applied first at the new Piscataway treatment plant of the Washington Suburban Sanitary Commission in Prince Georges County, Maryland, which will also incorporate research and demonstration projects in nitrogen stripping and other things.
Water Treatment
In the long run such advances offer the main hope of clean water for a superpopulated future America, where volumes of wastes are going to be enormous and first-rate off-stream treatment is going to have to be the main way of handling them. Even where wastes can be collected easily for treatment, however, as in industry or in sewered populated areas, it may take a good many years to work out varied forms of advanced treatment adaptable to different sets of circumstances, at prices that communities can afford to pay—and a willingness to pay what can be paid is going to have to be a part of the long clean-up job ahead. Undoubtedly continuing research will work out such forms of treatment, but the research itself may be quite costly and no one can predict its pace.
Where waste sources are too diffuse to be channeled into collection systems—as along many agricultural streams heavily polluted through land runoff and drainage, and also in some urban situation—present tools are extremely limited. Soil conservation practices aimed at cutting down erosion—to be discussed within a few pages—tend to keep not only silt but nutrients and other substances on the land to some extent. Concentrated sources of animal manure such as dairies, poultry operations, and feed lots can be brought under some control by fencing stock off from streams and by techniques of lagooning and later field spreading, which need much wider use in the Potomac Basin. But even if these approaches were applied fully throughout the region within a shorter time than appears likely or even possible, land runoff would still be a heavy source of water degradation.
Hence it is probable that flow augmentation—sometimes called "flow dilution" or included in the broader term "flow regulation"—through the release of stored water, will be an important auxiliary tool in water quality management for a good while to come. This is not a form of flushing wastes downstream from their source and out of sight, as some opponents continue to insist, but a means of helping streams to oxygenate and decompose excess wastes by the same processes they have always used on natural and normal loads. On the other hand, neither is flow augmentation the end-all cure for pollution that enthusiasts of a few years ago claimed it to be. Its effect on slow masses of water is uncertain and probably minimal, and too much dependence on it even for flowing streams would obviously encourage neglect of the practical and moral need to keep filth and troublesome substances from getting into the streams in the first place. Furthermore, such dependence would lead rapidly to a point of diminishing returns, like the flood-plain development and protection cycle examined in the preceding chapter. Increases in populations and pollution would lead to a necessity to provide more and more augmentation of flows, with storage space in reservoirs becoming more and more expensive precisely as flood protection does. Flow augmentation is no substitute for good treatment, but a valuable adjunct.
In the record drought summer of 1966 the South Fork of the Shenandoah, heavily polluted with municipal and industrial wastes near Waynesboro, and with fertilizer, manure, and other substances in drainage from the rich and intensively utilized farm country through which it flows, ran very low for months. In many places it was slimy and unpleasant, and aquatic life suffered to some extent, but the picture was not nearly so dismal as it would have been if the river had not been helped out more or less by accident. The source of this help was some 2000 gallons of water per minute that the Merck plant at Elkton and the Dupont plant near Waynesboro were releasing after having pumped it out of deep aquifers and used it for cooling. If all sources of pollution had been receiving adequate treatment, this minimal dilution might not have been so badly needed to avoid the fish kills and algal stagnation and other results that would have ensured without it. But "all sources" include the problematic agricultural drainage, and for that matter the definition of "adequate treatment" is going to have to go up and up in our expansive future.
The sad situation of the smaller and much less industrialized Monocacy in the same summer underscores the point. The Monocacy flows through similar farming country and passes by a few towns. The largest of these is Frederick, Maryland, for whose approximately 40,000 people the little river furnishes water and a conduit to carry away the effluent from their average-to-good secondary plant. At times during that dry summer practically the entire flow of the river below Frederick consisted of effluent, with effects on stream life, esthetics, and the general surroundings that are not hard to imagine.
Another good example of a place where, under present conditions, augmentation could sometimes be used beneficially is at Great Falls and in the Potomac gorge below. Heavy public expenditure has protected the shore in much of this neighborhood and provided pleasant recreation areas whose main scenic focus is the violent magnificence of the river in its plunge. But the magnificence becomes a rather drab joke in dry summers when metropolitan withdrawals of water above that point shrink the river to a semblance of normal flow.
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The North Branch and some smaller Basin streams also need this same kind of help andmost will continue to need it even when the best economically feasible treatment of all collectable wastes entering them is ensured. It can be provided out of reservoirs, large or small, whose need for other purposes as well will keep the cost of dilution within reason. A future possibility, if research presently going on in the Basin verifies it and shows ways of putting it to use, is to employ ground water in the same way. There can be no doubt that if the flowing waters of the Basin are to be put back in good condition and kept that way under population pressures that are in prospect, flow augmentation in some places is going to be an important tool.
In the upper estuary, however, its usefulness appears to be far more limited. The plan proposed in theArmy Reportof 1963, in line with a Public Health Service approach emphasized in the 1961 Water Pollution Control Act, was designed to provide an eventual minimum flow into the upper estuary of 3100 cubic feet per second, or around two billion gallons per day, for the purpose of dealing with treatment-plant effluents and miscellaneous pollution. But more recent investigations have raised strong doubt as to whether such augmentation could do the job in the estuary with its huge volume of water, and its slow, tide-baffled currents that greatly lessen its assimilative capacity.
In terms of dissolved oxygen, dilution of such a body of water for quality improvement appears to decrease in unit effectiveness as the volume of dilution is stepped up, which means that past a certain minimal point of improvement it gets expensive and requiresunreasonable amounts of storage. In terms of nutrients, one authority has calculated that about 20,000 cubic feet per second would be required to reduce the nutrient level in the upper estuary to a point where it would be only twice that of a normal and healthily "rich" section of the upper Chesapeake Bay. Some augmentation below the point of diminishing returns will undoubtedly be needed, not only for the estuary but to keep the river alive in its gorge above Washington during periods of low flow. But as a main tool for the metropolitan river, it will not substitute for achievement of the best possible standard treatment followed by advanced treatment and other techniques.
Obviously, just as in water supply, an ultimate cure for water quality ills is going to consist of a "mix" of solutions, different techniques being applied to the situations they are best suited to deal with, and combinations of them being worked out where combinations are what is indicated. Already the same kind of sophisticated mathematical models of given bodies of water—including the Potomac—that are being used to study solutions for water supply problems are being put to use on water quality as well, weighing the benefits and drawbacks of various combinations of means. And, just as in water supply, ultimate "hard" technology is undoubtedly going to make better solutions possible, while a strong and meaningful start is possible with the technology that is on hand.
Silt is a truly Basinwide problem. The individual tiny grains of soil that mass to sullyand choke the estuary may have originated anywhere in the thousands of square miles of drainage above. They constitute an economic loss at their points of origin as well as a trouble all along their downstream course of migration.
The basic-physical ways of preventing silt are twofold and easily defined: first, the maintenance of proper land cover—vegetation or humus or mulch which blankets and anchors the soil particles and prevents falling or flowing water from dislodging them—and second, structural approaches that control the flow of water and can also serve to trap eroded material. These latter can be anything from good contour plowing practices to a major reservoir with a certain silt capacity built into it.
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Such techniques are the basis of existing programs of the Soil Conservation Service and the Forest Service that have proved their effectiveness over many years of rural application. Watershed planning with small reservoirs, check dams, and terraces backed upby good land treatment and use, soil surveys, wise forestry practices, and such things are stimulated and bolstered in these programs by technical and financial assistance given to private landowners, States, and local organizations. They have already had important local effects in the Potomac States as throughout the country, but for maximum value in relieving sedimentation they are going to need much wider and more intensive application.
In modified form, they can be effective against newer and more concentrated sources of silt, while sometimes accomplishing other purposes as well. As we noted in discussing metropolitan pollution, urban land undergoing development can enormously benefit from good watershed planning. Preservation of critically erosive and flood-prone land in grass and forest, insistence on prompt re-vegetation of bared land and the use of such things as sediment detention basins by developers, the construction of small headwater reservoirs when they are needed to trap silt and reduce flooding—all these elements of watershed planning are effective not only against silt but against standard urban and suburban ugliness. The translation of rural techniques to city use cannot be literal, for both urban hydrology and urban land use are distinctive, and a good deal remains to be learned about making the techniques work better there. But their basic principles are obviously a main hope.
Other modifications of them, if put into wide practice, can cut down on the heavy production of silt by strip mines in the upper Basin; these involve both the reclamation ofabandoned mines and the use of more care in scraping new ones. And application of the same principles—protective cover and detention of runoff—to new highway and road construction, as well as to the reclamation of banks and shoulders on old secondary roads, has to be achieved.
The silt already in the upper estuary, and likely to continue to be deposited there even after the best available controls may have been put into operation above, will need radical treatment. The tens of millions of tons already choking the metropolitan river, the stockpile of centuries, will have to be dredged out if the river is going to be as pleasant and useful at the capital as it ought to be, and so will the yearly additions that can inevitably be expected. This can be done if the money is available, though a considerable unsolved problem, under research at present, is where to put the silt after it has been taken out of the river, for appropriate fill sites are growing scarce.
Turbidity in the sluggish upper estuary will continue to be a problem too, for the fine particles of silt that cause it are the least affected by standard land treatment and sediment control measures. Polyelectrolytes—chemicals which when applied in quite small amounts can coagulate such suspended silt and settle it out—offer some promise as tools against turbidity and are being tried out experimentally above one of the reservoirs on upper Rock Creek, with good results thus far. Very possibly they may prove to be useful for clearing up the estuary after it has been roiled by storm runoff, and for achieving somecontrol of murky waters around sand and gravel dredging operations. However, ironically, it has also been pointed out that until the excess of nutrients in the upper estuary is eliminated, such clearing of the water could very possibly cause a great increase in the already disastrous algae blooms, by allowing sunlight to penetrate to greater depths and foster more production of this undelightful greenery. Cleanup of pollution as complex as that evolved in the 20th century has to be across the board.
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Barring a general philosophical revolution on the part of the American people, the problem of junk and debris in our waters is likely to continue and even to increase as people and their consumption of the products of the economy maintain their geometric growth. Clean rivers in themselves might deter a good many people from cluttering them thus, and so might public education, stiff fines, and the provision of better municipal pickup and dumping facilities. But mainly getting rid of such detritus is probably going to be a matterof fairly continuous gathering and disposal. On navigable waters like those of the upper Potomac estuary, ingenious collection craft under the command of Army Engineers are in prospect; elsewhere the job is likely to be more old-fashioned and laborious.
For certain remaining pollution problems, no definite full technological answers exist at present and the main hope must be to alleviate them as much as possible while pressing a search for long-run answers. Some are relatively restricted in their effects in the Potomac Basin so far, though they have some drastic local effects and some long-run implications. Certain industrial wastes not amenable to any presently known form of treatment, such as tannery discharges at Petersburg, West Virginia, and Williamsport, Maryland, are one example. So are the noxious exudations of raw sewage and garbage from ships and pleasure craft. Marinas themselves and the boats docked there can and must be connected to waste collection systems. Laws can and should prohibit discharges from watercraft in harbors and rivers. But until better means of on-board waste treatment or retention than exist at present are evolved and made mandatory, the multitudes of boats with standard toilet facilities are going to keep on causing trouble.
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 runofffrom 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 designedto 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.