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8. That continuous tests be made by submerging timber treated with creosote oil in several degrees, ranging from the portion in which all the toxic ingredients have been removed to that of the full oil.
9. That continuous tests on the various commercial forms of surface coverings be made.
10. That service records and general data, including the element of cost, on the various forms of piling material other than timber be investigated.
11. That construction methods be further developed and the theories be disseminated among construction forces to cause a more careful handling of treated material about to be put in place.
RESEARCH WORK ON MARINE PILING
HERMANN VON SCHRENK, Chairman; Z. M. Briggs, S. D. COOPER, A. B.
ILSLEY, W. H. KIRKBRIDE, Sub-Committee. Wooden piles used in marine construction have since the earliest days been subject to attack by various forms of marine borers, including members of the genera, Teredo, Xylotrya, Limnoria, Sphaeroma, etc. Very little definite information, however, is available with reference to exact distribution of the various forms, their specific identity, the conditions under which they live, influence of temperature and salinity of waters, the methods of reproduction, feeding habits and kindred points.
The comparatively recent attack on marine structures in San Francisco Bay and in north European waters has brought the subject of marine borers and methods to be used to protect against their ravages prominently to the attention of engineers in all parts of the world. As this is a matter of very vital interest to the members of the A.R.E.A., your Committee has prepared a brief discussion of this subject.
RECENT DEVELOPMENTS.--While marine borers have been more or less prevalent in the warmer waters tributary to the United States and Canada, no unusual activities were reported until 1917, at which time unusually severe attacks of marine borers were reported by Dr. A. L. Barrows at various points in San Francisco Bay.
The outbreak in San Francisco Bay has continued with remarkable vigor so that to date approximately $20,000,000 worth of damage, more or less, has been reported from that region alone. While these reports were coming from San Francisco similar reports were being received from various north European waters, particularly along the coast of Norway and Sweden, and from various points in England.
The European interest in this subject is very well shown in the recent appearance of a long report by a special committee of the British Institution of Civil Engineers appointed to investigate the “deterioration of structures of timber, metal and concrete exposed to the action of seawater.” The report of this committee, consisting of a volume of 301 pages, with thirty-three plates and thirty-seven figures, deals in part with marine borer attack on wooden structures in all parts of the world and is a valuable contribution to this extremely important problem. Another recent report comes from Denmark, the result of investigations of a joint committee of the Danish, Swedish and Norwegian Engineering Societies.
RECENT INVESTIGATIONS.--Stimulated by the recent attacks just referred to, investigations with reference to marine borers have been started in various parts of the world. The first contribution of impor
tance dealt with the San Francisco Bay situation ‘and appeared as a report of the San Francisco Bay Marine Piling Committee of the American Wood-Preservers' Association, in 1921.
This valuable report gives a complete description of the attack, discussion of the various forms of borers found, a description of the physical conditions of San Francisco Bay with particular reference to salinities and temperatures, and suggestions for protective methods to be used. Various activities in Europe are also to be noted, particularly the report of the British Institution of Civil Engineers already referred to, and work done in Sweden and Denmark.
Shortly after the San Francisco Bay appearance it was recognized that environmental conditions probably had a good deal to do with the virulence of attack at that point. The salinity of San Francisco Bay had risen considerably due to reduction on fresh water run-off from the western slopes of the Sierra. Recognizing the probable vital relationship between attacks of marine borers and salinity and temperature of waters in which these organisms thrive, careful determinations as to salinity and temperature have been made in San Francisco Bay and investigations are now in progress to more clearly define the extremes of salinities and temperature under which the various species develop. Recognizing the possibility of unusual marine borer attacks in other parts of the country, your Committee has endeavored to obtain information as to salinity and temperature at various points on the Atlantic, Gulf and Pacific Coasts. In the report by Sumner et al., "A Report Upon the Physical Conditions in San Francisco Bay, etc.,” University of California Publications in Zoology, July, 1914, a comparison is made between the annual water temperatures for San Francisco Bay, Woods Hole, Mass., and points in Chesapeake Bay, which are of interest in this connection:
“The mean latitude of these points in Chesapeake Bay is very nearly the same as that of San Francisco Bay. The mean annual water temperature for the former bay, computed from the records referred to, is 14.38° C. (57.89° F.), that for the latter bay being 12.91° C. (55.23° F.). The chief difference between the temperature conditions of these two bodies of water lies, however, in their respective annual ranges. In Chesapeake Bay this amounts to 22.12° C. (39.82° F.), while in San Francisco Bay it is not much more than a third (38 per cent.) as great, being 8.35° C. (15.03° F.). Thus the equable climate for which California Coast is famous is reflected in (we should say, is largely due to) the equable temperature of its coastal waters, though the direction of the prevailing winds is likewise an important factor."
“The resemblance between the Chesapeake Bay curve and that for Woods Hole, Mass., is sufficiently striking. The latter is based upon the monthly means for a period of six years, as recorded at the Woods Hole station of the Bureau of Fisheries. The vertical distance between the Woods Hole and Chesapeake Bay curves remains surprisingly constant throughout the year, representing, on the average, 3.82° C.
"The mean annual temperature of the surface water in Woods Hole Harbor is 10.56° C. (51.01° F.), or more than 2° C. lower than that of San Francisco Bay. The annual range, computed as for the other points, is 21.50° C. (38.74° F.).”
The same authors in discussing ranges of salinity make the following reference for the same stations:
“For Buzzard's Bay and Vineyard Sound, the density ranged during the observations made in the course of the biological survey of the Woods Hole region from 1.0212 to 1.0244, representing salinities of about 28.7 and 33.0 respectively. The mean for the two bodies of water was about 31.7, a figure slightly higher than that for San Francisco Bay at the station nearest the Golden Gate, and about 15 per cent. higher than that for the Bay as a whole. The absence of any large streams within the Woods Hole region and the free intermingling of the coastal water with the ocean through the tides, are obviously responsible both for the higher mean salinity and for the small range of salinity in that region."
“In Chesapeake Bay, on the other hand, the salinity averages much lower than in San Francisco Bay. Figures are available from twentyfour stations within the upper two-thirds of Chesapeake Bay. These are derived from the "Manual of Oyster Culture in Maryland," by Grave (1912, pages 47-48). We have converted the density figures given in this report into corresponding ones for salinity, making due allowance for the temperatures at which the salinometer readings were made.”
"The observations in Chesapeake Bay were made during two periods of the year: (1) during that of greatest rainfall (April 20 to May 8), and (2) during the period of least expected rainfall (October 10 to 26). The mean salinity for all the stations for the first period was 10.86, that for the second being 14.20. The mean of these two figures is 12.53 This represents an average salinity considerably less than half that of San Francisco Bay. It is a lower figure, indeed, than the annual mean for any of our hydrographic stations, even those in Carquinez Strait."
"The mean figure for the Chesapeake Bay station having the highest salinity (average for the two periods) was 18.90, that for the station having the lowest salinity being 4.33."
Aside from a lot of isolated observations very few data appear to be available for the different ports of the Atlantic, Gulf and Pacific Coasts. A few figures which were obtained through the courtesy of Messrs. E. J. Pearson, J. F. Pinson and G. J. Ray are herewith submitted as suggestions:
San FRANCISCO BAY.-See Proceedings of American Wood-Preservers' Association, 1920.
New YORK HARBOR: The following temperatures were taken by the Metropolitan Sewerage Commission of New York in 1912 and 1913 at Pier A, Hudson River mid-stream:
The following temperatures were taken by the New York Aquarium at the Battery, New York City, at 3:00 p. m. daily in 1920 :