appearance of streams. Efficient sedimentation will remove a substantial part of suspended matter generally and nearly the whole of the suspended matter which is capable of settling and producing bottom deposits of an offensive character. Fine screening is intermediate in effectiveness between coarse screening and sedimentation. The requirements of each particular situation and the relative cost of the installation and operation of these three systems must determine in each case the type of treatment to be adopted. There is a third type of nuisance, chemical in its nature, which arises from changes in the chemical characteristics of streams-reduction in the normal degree of aeration, development of offensive odors, and discoloration and banishment or destruction of fish life. It is due to the oxidizable character of the polluted waters. Partial improvement results from screening or sedimentation by the removal of a portion of the oxidizable matter. Biochemical oxidation of sewage, which is the most effective treatment, is brought about by passing it through natural or specially prepared beds of sand or over the surface of stones or other coarse material or by passing it through tanks, with artificial aeration in contact with sludge properly cultivated (activated sludge), for the development of oxidizing organisms.

With the extension of stream pollution by increasing population these three kinds of nuisance appear in the chronological order in which reference has been made to them. A minor physically undetectable pollution may seriously injure a stream bacterially, and a stream may be physically affected by floating débris and deposits, and yet, from a chemical standpoint, be normal or practically so. The final result of continuously increasing pollution is the chemical breakdown of a stream, resulting in the most objectionable conditions, examples of which are becoming increasingly common in the more densely settled sections of both countries. In purely local situations in the Niagara, Detroit, and St. Clair Rivers, for instance, notably in the vicinity of sewer outlets and the mouths of tributary streams, and in the inner harbor at Buffalo, the waters are polluted to the extent of definite chemical nuisance. At these points the difficulty is due to incomplete dispersion of the sewage permitting the overloading of the immediate waters. The rivers as a whole, however, are far removed from this condition.

It is advisable to consider the Niagara and Detroit Rivers as a class by themselves so far as remedial and preventive systems are concerned. As has been stated, the most serious condition existing is the bacterial pollution of these streams. To remedy this evil, sewage treatment should be applied in connection with dilution so far as is necessary to bring their waters to the standard mentioned—a mean annual cross-sectional average of B. coli not exceeding 500 per 100 c. c. This necessary sewage purification can be effected by fine screen

It must be admitted that the conservation of public health is of paramount importance under the treaty. This is Sanitary considera- evident from Article IV to which reference has been made. The significance of sanitary considerations is also evidenced by Article VIII of the treaty,

tion first in order of procedure.

which contains the following provisions:

The following order of procedure shall be observed among the various uses enumerated hereafter for these waters (meanng boundary waters), and no use shall be permitted which tends materially to conflict with or restrain any other use which is given preference over it in this order of procedure:

1. Uses for domestic and sanitary purposes.

2. Uses for navigation, including the service of canals for the purposes of navigation.

3. Uses for power and for irrigation purposes.

"Injury" a complex question.

*

Although this order of procedure is in respect to certain uses enumerated in this particular article, it may be taken as indicative of the view of the high contracting parties regarding the importance of sanitation. Notwithstanding this, the discharge of sewage into streams can not be looked upon exclusively from the standpoint of its harmful effects upon health and property. The reference itself does not so look upon pollution. One of the questions in its second branch is, "By what means or arrangement can a system or method of rendering these waters sanitary and suitable for domestic and other uses be best secured and maintained in order to insure the adequate protection and development of all interests involved on both sides of the boundary?" The growth and development of riparian communities would be seriously arrested if pollution were looked upon from this standpoint exclusively. While public health is the paramount consideration, it must be looked upon, however, as only one of a large number of elements in the many-sided and complex question of the public weal.

The pollution of rivers in England has been the subject of investigation by royal commissions which have been studying the question very thoroughly and almost continuously for about 50 years. Their investigations have covered nearly all the rivers of England and practically all the various phases of the problem of river contamination, and the voluminous reports submitted by them from time to time are very valuable and deserving of careful study. The conclusions and recommendations made in these reports, while recognizing sanitary considerations as first in order of precedence, are based upon the implied assumption that the solution of the problem lies in the proper balancing of the various conflicting elements existing in the individual cases.

"Injury " as between lower and upper communities.

The parties who appeared before the commission discussed the question of "injury" almost entirely as viewed from two standpoints: First, from the standpoint of the relation between the riparian communities which pollute the waters of the streams and those communities which suffer in consequence of the pollution of their water supply; and, second, from the standpoint of the agriculturists, the floating population of summer resorts, casual visitors, picnickers, campers, yachtsmen, and crews and passengers of vessels frequenting boundary waters.

The difficulties arising from viewing the situation from the first standpoint will appear by considering the supposititious case of town "A" and town "B," the first town being situate above the other on the same bank of a boundary stream, the former discharging raw sewage from its sewerage system into the river, the latter being obliged to drink the water thus contaminated or to purify it at its own expense. To compel "A" to purify its sewage absolutely or completely would, under present conditions and in the present state of sanitary engineering practice, involve a financial burden too great for that town to bear, a burden which might retard its progress both industrially and in respect to population. On the other hand, to permit "A" to relieve itself of any reasonable financial burden by throwing its raw sewage on the waterworks intake of "B" and thus compelling that town either to drink contaminated water, or to assume an unreasonable financial burden in purifying it, would be an act of injustice which no fair-minded community, with a proper appreciation of the evil inflicted, would perpetrate or continue, and one to which no community should be asked to submit. If the harm which would be done "B" could be remedied, however, by the assumption of a financial burden which would be reasonable under all the circumstances of the case, there would not be an "injury" within the meaning of the reference or the treaty.

standpoint of summer

residents, etc.

From the second standpoint, that of the agriculturist, the floating population of summer resorts, etc., the question of "Injury" from the "injury" under the reference is a much more difficult one. The shores and islands of the boundary rivers and lakes must particularly be considered. Their scenic attractions, their pure air and salubrious climate, their opportunities for bathing, fishing, and yachting, and their ease of access, affording facilities for rest, enjoyment, and health restoration to unlimited numbers, are invaluable assets, factors in progress and civilization which should not, unless under the pressure of absolute necessity, be destroyed. The harm done by existing pollution to bathing resorts can not be remedied except by preventing the discharge of sewage into the waters which flow to them. Contamination of the sources of the drinking supplies of these classes of people is a most serious matter. The millions whom it affects or may affect are

87873-18-3

Typhoid death rates per 100,000 of population.

1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916

It may be incidently mentioned that there is a marked improvement in the statistical showing in the period since the commission's investigation in 1913. This is largely attributable to the fact that in consequence of this investigation greater efforts have been made to protect water supplies by the use of bleaching powder and liquid chlorine. The condition, however, is still far from satisfactory. Notwithstanding the general improvement, violent outbreaks of typhoid fever have occurred, and the potential danger must continue to exist in view of the extensive pollution of these waters and the limitations and inefficient operation of water-purification plants. Not only have the border communities suffered from this condition, but the navigation interests have also been injured very severely from the disastrous outbreaks consequent on the use of polluted boundary water.

IV. TRANSBOUNDARY EFFECTS OF POLLUTION.

This report so far has dealt with pollution generally in boundary waters. The reference as amended calls for a further inquiry into pollution of the waters on one side of the boundary line which may extend to and effect those upon the other side. Some persons who appeared before the commission argued for a literal interpretation of the language of the amended reference and suggested that the only pollution with which the commission is concerned is that which actually crosses the boundary line and has a transboundary effect. While the commission does not accept this narrow interpretation, it must consider the extent to which, and the places at which, pollution has such an effect.

Detroit River.

The most intense and the most clearly demonstrable cases of pollution crossing the boundary exist in the Detroit and Niagara Rivers. The city of Detroit discharges into the former all the raw sewage from its estimated population of 850,000. On the United States side opposite Amherstburg the pollution of the river reaches the enormous figure of 10,392 B. coli per 100 c. c., and its waters from that point to Lake Erie and the waters of that lake within a radius of about 4 miles from the mouth of the river are very greatly polluted. Beyond question the pollution from Detroit and the towns lower down the river crosses the boundary line and affects detrimentally health and property on the other side. A notable example of this is to be found in the condition of the shore waters of Bois Blanc Island, a summer resort on the Canadian side of the river which is extremely popular, especially with the inhabitants of Detroit. The island shore waters are very greatly polluted by the sewage from that city. The transboundary effect of this pollution may be estimated from the data given in Tables XII, XIII, and XIV, and the maps opposite pages 38, 39, 40, 41, and 42 of the Progress Report. Transboundary effects are detectable along the lower stretches of the river generally. Owing to the comparative smallness of the towns on the Canadian. side, it is not at present possible to trace pollution from them across the boundary, but these towns are growing rapidly, and if they ever attain anything like the size of Detroit or Buffalo, unless successful preventive or remedial measures are adopted, the river will be absolutely unfit for domestic purposes.