(9) Final chemical treatment (chlorine, lime, fluoride, phosphate)

PURPOSE OF CHEMICALS

CHLORINE: Destroys organic materials PHOSPHATE: Lessens pipe corrosion FLUORIDE: Lessens tooth decay CARBON: Controls taste and odor ALUM: Forms "floc" (snowflakes) to trap impurities LIME: Helps "floc" formation; lessens pipe corrosion ]

The basic and usual damage comes from oxygen depletion. A stream has a natural capacity for hastening the decay of organic wastes, which is determined by such things as the volume of its flow, the pollution already in it, its velocity and depth, and its temperature. When that capacity is exceeded, as we have noted, too much of the stream's oxygen is used up by the process of decay and the stream, which is an intricately complex work of living things, begins to die. Under really bad conditions, the waste solids themselves cannot all be a.s.similated, and hence may build up in layers of stinking sludge at the bottom of the stream and continue to seize available oxygen for a long time thereafter.

Conventional waste treatment, in plants built by towns or by industries whose raw materials are animal or vegetable in origin, is aimed at removing the solids in the wastes and reducing the bio-chemical oxygen demand--called B.O.D. It is a speeded-up version of the same process of purification that goes on normally in any stream when loads are not too heavy. "Primary" treatment removes such solids as will readily settle out and pa.s.ses the rest on back to the stream as part of the effluent.

"Secondary" treatment plants, after settling out the gross solids, speed up decay by furnishing air to the bacteria that eat up dissolved and finely suspended materials; a good secondary plant, under much more skillful supervision than is usual, can get rid of 85 or 90 percent of the organic materials and the a.s.sociated B.O.D. by the time it turns its effluent into a stream. How damaging that effluent will be depends on a number of things, chief among them being the size and condition of the receiving stream and the volume of organic materials that went into the treatment plant in the first place. A riverside town of 1000 with a secondary treatment plant operating at 75 percent efficiency is going to inflict on its river a daily load roughly equivalent to the raw sewage from 250 people.

Over the years a lot of hard effort, notably on the part of the Interstate Commission on the Potomac River Basin, has resulted in some degree of treatment for about 85 percent of all munic.i.p.al wastes and 83 percent of those produced by industry along the Basin's flowing streams. Put in another way, by INCOPOT calculations the total waste load imposed on the Potomac is only about three-quarters of what it was in 1956, despite a population increase of nearly a fifth.

That it is still much too high in many parts of the upper Basin does not require elaborate instruments to detect, but only a nose and a pair of eyes. A very few industries and towns are still dumping raw wastes, and many of the others need better and bigger sewers and treatment plants or better operation of the plants they have. Sewage collection systems are sometimes of the old-fashioned combined type, like c.u.mberland's--and, as we shall see, like Washington's--which have to carry storm runoff as well as wastes, and overflow during rainy periods, releasing heavy pollution without treatment. But even separate sanitary sewers are often overloaded by having to serve greater populations than they were designed for, which means that their escape valves may leak raw sewage more or less continuously into surface watercourses and that the quality of treatment given the sewage that does reach the treatment plant signifies less than it ought to.

Antiquated or overloaded treatment plants cause much trouble. Old primary plants too small for present populations often remove only about a third or less of the organic material, but by their very existence they tend to lull communities into a false conviction that they are doing their part toward clean rivers. Tiny plants of the sort authorized locally for new leapfrog subdivisions and vacation colonies are usually doomed to restricted efficiency by their very size. These often are underdesigned even for initial loads, let alone for the growth that comes later, and most of them are poorly run.

This question of operation is crucial. A new, well-designed, expensive plant in slovenly or inexpert hands--a frequent paradox--can put out a much greater waste load than a well-operated old one. The plant at Romney, West Virginia, on the lower South Branch, the best example of responsible operation in the Basin, is old, but because it is well run it usually achieves about 92 percent elimination of B.O.D. in comparison with the 75 percent or even less that some newer and more imposing plants can claim.

The reasons for poor operation are various. One is a shortage of qualified operators, based on a need for better salaries, more training programs, and rigid mandatory State certification of operators'

abilities. Another reason can be a pinchpenny att.i.tude on the part of munic.i.p.al authorities toward sewage treatment. It is one sizable expenditure whose results cannot easily be pointed out with pride to local taxpayers at election time, for its main effect is usually downstream from the munic.i.p.ality itself. Thus the big encompa.s.sing reason for bad plant operation--cutting corners, refusing to spend what needs to be spent, failing to supervise--has to be called philosophical.

It comes from a failure on the part of local operators and authorities and much of the public to comprehend the immorality of deliberate avoidable pollution, and it may mean that munic.i.p.al operation of treatment plants is itself often a major source of trouble.

A clear example of this philosophical deficiency is one large Basin treatment plant that was reported to have "handled"--i.e., properly disposed of--a third less sewage sludge in 1965 than it had in 1960, despite a large increase in the population it serves. The unhandled sludge, of course, went straight into the local river for reasons of convenience, economy, and callous indifference.

For the most part, large private industry demonstrates more responsibility in this respect than the Basin's munic.i.p.alities or Federal installations. There are some miserable exceptions where individual industries dominate a locality's economy and take casual advantage of that fact. But responsible industry is concerned with public relations, and knows that a fish kill or a gray-blue stretch of blighted water downstream from its outfalls is the poorest kind of public relations to be had.

To be able to say precisely how much bad plant operation is adding to pollution in the Potomac will require exhaustive and continuous sampling and a.n.a.lysis of a kind that may be expected now that the Water Quality Act of 1965 is about to make itself felt through application of new State water quality standards. But experienced observers in INCOPOT and elsewhere feel strongly that bad operation does much more damage than do over-aged or outgrown facilities, though these play a big part too.

Bacterial pollution--the category of most interest from a public health standpoint--fluctuates a great deal in the Basin's flowing streams, but is heavy in most of them by current standards during times of normal flow. It may come from raw waste discharges, from treatment plants that skimp on chlorination of their effluent, or from storm runoff and natural drainage off the land and urban pavements. But before anyone can confidently say how dangerous it is to swimmers and others who make intimate use of rivers and creeks, water scientists are going to have to learn more about its measurement and cla.s.sification than they presently know.

[Ill.u.s.tration]

No easily applied method of testing can effectively establish the guaranteed absence of human disease germs. The traditional "Coliform Count" plays safe, as it must. It measures the concentration of certain easily spotted "indicator" organisms that do not themselves make people sick but are always voluminously present in the fecal discharges that can carry harmful germs, and it gauges the danger by the concentration of these indicators.

However, concentrations of coliform bacteria, originating in animal manure or elsewhere, may invade a stream through runoff from rural lands without having any meaningful relationship to human disease germs.

Counting them under such circ.u.mstances is a little like measuring the depth of the proverbial well by the length of the pump handle.

Furthermore, no one really knows how easy or how hard it may be to catch given diseases by swimming. In this country, outbreaks of leptospirosis, an illness common to man and certain animals, have been traced to swimming holes, and other links are obvious. On the other hand, some careful British investigations turned up a good many quite healthy people who habitually splashed about in sea water teeming with pathogenic organisms of one sort or another. Sea water and fresh water have vastly different qualities, but the subject is presently full of confusion, and it needs much research.

Land runoff in general furnishes a large amount of pollution of all cla.s.ses, and in all parts of the upper Basin except the least-used forest sections. Besides bacteria, heavy loads of organic material may be washed into streams in regions with high densities of livestock or poultry, and some pollution of this sort is found practically everywhere. The wild and domestic animal population of the Basin above Washington has been estimated to produce wastes equivalent to those of about 3.5 million people. Much of this is dealt with by the "living filter" of the soil, but much also reaches the streams, a.s.sociated with sediment from erosion producing rains. And the sources, particularly in areas such as those along the Shenandoah and the Monocacy and other streams with wide rich valleys, are numerous and diffuse.

Nitrogen and phosphorus nutrients, which foster weeds and slime in quiet stream stretches and contribute to the problems of the estuary downstream, are found in undesirable concentrations in most of the Basin's waters above the Fall Line. Not only are the growths encouraged by these fertilizing agents ugly, but they also upset the ecological balance of streams by favoring certain types of aquatic life over others, and they can cause tastes, odors, and clogging in water supply systems and sometimes, by rotting, a secondary sort of oxygen deficiency. Nitrogen and phosphorus occur in the effluent from waste treatment plants, for they are present in human wastes and in detergents, and in dissolved form are little affected by standard treatment processes. And in the upper Basin a large part of the nutrient load in streams appears to be a.s.sociated with sediment from the same diffused land runoff mentioned above, for they occur abundantly in manure, in synthetic fertilizers, in certain natural soils, and in decaying organic substances of many kinds. The health and growth of living things is dependent on these elements, of course; it is their excessive release into waters that causes trouble.

From the same farming regions and even more from lawns and gardens and parks in more populated areas, pesticides and other economic poisons accompany sediment into the stream system or are blown into it as sprays and dusts. They seem not to be as great a problem in the Potomac as in some other rivers, but they are present in probably significant amounts; indicator tests hover near Public Health Service drinking-water limits in the river. Their use, here as elsewhere, increases year by year, for they are tremendously effective against many of man's ancient enemies. Being easily available, they are often used in uninformed and careless ways despite government efforts to determine and publicize safe levels of application. Knowledge about their side effects, both immediate and long-term, is still full of gaps. Badly misused, they are obviously dangerous. But information about the precise results of their ordinary use and their buildup in nature acc.u.mulates very slowly.

The persistent chlorinated hydrocarbons--DDT and its relatives--last for a long time after being released into the environment, concentrating at various points in the natural food chain and often in man himself. It is said that an average adult Californian's tissues today contain more DDT than is allowed in beef for interstate shipment. But no one is yet certain what this means in relation to that average Californian's physical wellbeing, and in terms of fish and wildlife, though the link between these materials and certain destructive changes can be seen, evidence in other cases--the declining fertility and numbers of bald eagles, for instance, which some investigators believe to derive from pesticide residues--only points toward such a link. Until all the facts are in and the impact of such poisons has been clearly restricted to the pest species at which they are aimed, they are going to continue to be a heavy concern for conservationists and others alarmed about environmental pollution, along the Potomac and elsewhere.

[Ill.u.s.tration]

[Ill.u.s.tration]

One of the princ.i.p.al Potomac pollutants, silt, not only comes from the land but is the land, most often good topsoil, washing away toward the sea. Even under pristine conditions streams are likely to run somewhat muddy after storms; it is a natural phenomenon, a by-effect of the way climate carves landscapes. On the evidence, however, the Potomac landscape since its colonization by white men has been undergoing a much more rapid carving than anyone could consider to be natural. Most of its streams, particularly in their lower reaches, are thickly opaque for long periods after rain, and gross erosion in the Basin--the amount of soil washed away from where it usefully belongs to somewhere else--averages about 50 million tons per year, a major depletion of the soil resource and a degrading influence on the landscape through erosion. The part of this silt that gets into streams cuts down on the usefulness of the water, creates ugly turbidity, chokes quiet pools and reservoirs, suffocates bottom-dwelling creatures and plants on which the streams' wholeness may depend, and rides down the current to add heavily to the problems of the estuary, into which some 2.5 million tons of it are annually discharged.

Sediment is dislodged from the land by the pounding action of raindrops and the flow of runoff, and sometimes is washed from streambanks during high flows--which may themselves be higher and more frequent because of silt-clogged channels. The bulk of it can be blamed on unsound land use.

This may be rural, based in the old use-her-up-and-move-along pioneer outlook that has never died out among us despite wide understanding of better ways of doing things. People in places still overgraze pastures and clean-cut timber so that rain can get at the soil and eat it away, and they still farm land too steep to stay in place without its vegetative cover, or they plow even suitable rolling land in straight rows up and down hill so that water and soil sluice away together down the furrows when it rains. Despite a sharply effective three decades of work and public education by the Soil Conservation Service and other agencies, these old practices continue in some places and cause much erosion.

[Ill.u.s.tration]

Also, increasingly, bad land use involves the ways in which great machines adapt the landscape to hundreds of sophisticated purposes. The ma.s.sive eatings of powered blades and scoops to get at coal and other minerals on the steep slopes of the North Branch watershed and elsewhere, add heavily to sedimentation. So do broad rights-of-way gashed out of the countryside and left bare under storms in the months before highway construction is done, and secondary roads that even when finished may be left for years or forever with denuded clay shoulders and ditches and banks that wash with every rain. And so, most particularly, do the great polygons of rolling land around the Basin's town and cities that are stripped naked by bulldozers and left sitting in that condition for long periods, while they await the erection of buildings and blocks of homes. This is occurring throughout the Basin, but most notably around Washington, where the highest erosion rates of all are found. We will take a look at its details and the reasons for it a little further along in this chapter when we examine the estuary's situation.

Except for the acid parts of the North Branch, the upper Basin's waters in most places, most of the time, can still serve the "practical"

purposes to which they are put--irrigation, industrial uses, munic.i.p.al supply after purification, and even the absorption and digestion of effluents from adequate, well-run treatment plants. Most of the streams are usually good to look at, especially in conjunction with the superb rural landscapes against backgrounds of wooded mountains that are characteristic. They furnish much pleasure to fishermen, hunters, boatmen, swimmers, picnickers, and other folk, though in some places it is an open question, as we have seen, whether or not contact with the water is prudent. And almost everywhere, aging locals can recall a time when their stream was a happier amenity than now--when it held more fish, ran clearer over stones and gravel not coated with weeds and green slime, did not have the smell it presently emanates, was colder and more copious....

Their nostalgia probably does not play them false, even though conditions in many places are better now than in the intermediate past, after modern times had settled in, but before INCOPOT and the Soil Conservation Service and such influences had begun to push for reform of the casual, anciently human ways of doing things in which present human populations can no longer afford to indulge themselves. Some of the gains that have been made are being cancelled out by growth and new types of pollution, however, and in general the flowing Potomac river system is teetering at the brink of bad trouble. It needs help.

If the flowing upper Potomac had any lingering oxygen deficiency in its lower stretches--though it seems usually not to--it would tend to rectify the lack in its turbulent eighteen-miles descent across the Fall Line, a superb natural "treatment plant." Normally it arrives at Washington charged with oxygen, but does bring down with it the part of its nutrient load that has not fertilized upstream weeds and algae, periodic waves of bacterial concentration, and a great deal of debris and silt in season.

In the broadening, slowing upper estuary, its sluggish currents confused by the twice-daily surge and ebb of tides, these materials from above are stirred in with an array of specifically metropolitan pollutants--with more silt off of the outraged urban watershed, with junk and debris of a thousand sorts, with decaying substances and bacteria from many sources, and with vast new quant.i.ties of nitrogen and phosphorus. The consequence is a weighty and sometimes spectacular pollution problem directly adjacent to the proud national capital. It is at its vivid and aromatic worst in summer, when the most Americans come there fondly to view the city and the Potomac, and when locals who want to boat and fish and swim and do the other things one does on water would make most use of the river--indeed, do make use of it in spite of everything.

Like the meek, the upper estuary inherits the earth, or at least that part of the Basin's earth that is washed downriver as silt. There are enough fine suspended sediment particles in the water of the metropolitan river to make it drably opaque most of the time, even during relatively dry spells, when heavy sand and gravel dredging helps to keep it stirred up. As the current loses force and washes back and forth with the tides, the particles settle out slowly into smothering, continually renewed blankets on the bottom, and over two centuries have accreted into great mudbanks and shoals. Channel dredging to maintain navigation has been going on since the early 19th century, about 180,000 cubic yards being presently removed each year. The dumping of the dredged materials on the marshes and long low sh.o.r.es has built up wide, flat, new flood plain areas around the city over the years, including the sites of Washington National Airport, Anacostia and Bolling Air Fields, and East and West Potomac Parks.

Such channel dredging has little effect on the gradual shoaling of this whole part of the river in general. Miles of formerly navigable water downstream from Memorial Bridge are now only one to four feet deep and useless for either pleasure or commercial craft. It has been estimated that present rates of deposition will within fifty years fill in the upper estuary completely to a mile or so below Alexandria, except for a river channel. The same process is at work in the tributary creek-bays that give onto the estuary, some of which have silted so heavily since Colonial Days that formerly thriving ports--among them Bladensburg, Dumfries, and Port Tobacco--are now distant from the water.

The bulk of estuarial silt comes down the main river from the upper Basin. But a heavy increment is added in the metropolitan area. Modern mechanized development of the city's hilly environs on a huge scale, continuing year by year with few thoughtful rules to guide it heretofore, has brought about erosion that on individual patches of bared land may reach a temporary rate of 50,000 tons per square mile per year, and even average rates in this area are far in excess of anything else in the Basin.

We had to examine the reasons for this rather closely last year in a study of Rock Creek's ailments, whose findings we published in a report called _The Creek and the City_. This much-admired metropolitan stream has been relatively well protected, with the parks along its wooded valley and an upper watershed that until quite recently remained essentially rural. But as development has proceeded in standard and careless ways--the wholesale stripping and scarification of big tracts of rolling, fine-textured land, the long naked wait for development--the creek has come to be muddy and ugly almost all the time and has been spewing an estimated 100,000 tons of sediment a year into the estuary, with frequent floods.

[Ill.u.s.tration]

[Ill.u.s.tration]

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 a.s.sociation under Soil Conservation Service auspices and brought about the construction of two small upstream reservoirs to control flooding--with results noted in the preceding chapter--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 ma.s.sive 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.

[Ill.u.s.tration]

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 sh.o.r.eline windrows of deceased carp and perch 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 its tributaries from a large number of storm-sewer outfalls and other places. Partly these flow from malfunctioning individual septic systems in outlying areas, surrept.i.tious 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 const.i.tute a worrisome pollution problem even if the matter of sanitary wastes were thoroughly in control.