Page images

face. They have also tried various means of handling Douglas Fir, and for example favor the growths cut from rocky land which are highly resinous, particularly at the butt. They have found that additional length of life can be secured by driving these piles butt end down so that the most resinous section comes in the range of the greatest attack, from mud line to low tide level.

The Northern Pacific Railway has conducted considerable investigations of borer action at Seattle. A complete diver inspection has been made of all their wharf piles, and increment borings have been taken. Complete records of this examination were made showing progressive stages of destruction of the piles. As an example of the severity of borer action, they make the following statement:

“We have many samples of piling completely honeycombed with teredo holes, through a heavily impregnated ring of creosote.”

As already stated, this railroad has driven a set of test piles in a dock at Seattle, and is co-operating with this Sub-Committee in recording results of service observations.

The Oregon-Washington Railroad and Navigation Lines have wharves at Seattle, Tacoma, Ilwaco and Nahcotta, where they consider the creosoting of piling essential in all cases. The results of their investigations are interesting for many reasons, including that of using green piles without air-seasoning, and favoring water jetting in driving, where possible.

The Southern Pacific Company has marine structures at Tillamook, Yaquina, Coos, San Francisco and San Diego Bays, as well as elsewhere. A characteristic of this Company's work is that of being the only road which operates its own Pacific Coast pile treating plant. Furthermore, it is in position to raft piles or handle on cars to the job direct from the creosote plant, thus eliminating to a very large extent the liability to damage from dogging and frequent handling. A third point is that they have positively succeeded in turning out creosoted fir piling which is still serving, after having been in place 30 years. As already stated, this railroad has also driven test piles for observation under the direction of this Sub-Committee.

The Northwestern Pacific Railroad Company has marine structures in San Francisco Bay, Petaluma Creek and elsewhere. This railroad has demonstrated an interesting use of metal sheathing for pile covering, some of which was tried as far back as 1884. Some of their metal covered piles driven at a more recent date are still in service, after being in place from 15 to 20 years. This road is also co-operating with this Sub-Committee in the matter of service test piles driven by them, at Tiburon.

The San Francisco-Oakland Terminal Railways have a long pier extending into San Francisco Bay from the east side. They have tried several forms of pile covering including wood battens and concrete, and

in one case found untreated eucalyptus piles, which had been driven with bark on in shallow water, to be still sound after 15 years of service. These were removed and not redriven when the Company altered its pier, thus making it impossible to observe the possibilities of further service.

Among the numerous industrial firmis actively co-operating in the project to combat the marine borers is the California-Hawaiian Sugar Refining Company, located at Crockett, on Carquinez Straits, a body of water tributary to San Francisco Bay. The experience of this Company is particularly noteworthy for the reason that the water in the Straits was originally fresh at their location, and later became salt because of inroads of irrigation projects on the river above, and because of the years of drought. Their shipments of raw sugar from the Hawaiian Islands create extremely heavy loads on their wharves and warehouses, all of which are supported on piles. The arrival of salt water brought with it a very severe attack of marine borers, and after a failure of a wharf section, the Company set about to redrive all foundations. New wharf and warehouse floors were made of reinforced concrete, supported by groined arches, which in turn rested on the piling. Timber piles were used where the bottoms of groined arches penetrated several feet below the mud line, and reinforced concrete piles where they would be exposed to salt water.

The Santa Fe Railway Company has a number of marine structures in San Francisco Bay and at San Diego, and has constantly been in touch with coast investigations. They are participating in the continuous pile service test already referred to, and have driven a set at San Diego for observation.

The entire waterfront of San Francisco is under the control of the California State Board of Harbor Commissioners, who began to function in 1863. Since that time, they have directed all building in this section of the harbor, and their files constitute one of the most valuable records on Pacific Coast waterfront construction in existence. In this respect they are fortunate, for the reason that the Ferry building, which houses their offices, was not destroyed by the great fire of 1906. A majority of other organizations with general offices in the heart of the City, lost all their records, and now only have those dating from that year. Another feature which has helped to make their records available is the biennial reports which have been published regularly, and now can be referred to. The Harbor Board is in direct control of a great number of marine structures, and their experiences over such a long period have demonstrated many valuable facts.

The Board has just issued a report on Piling Service Records which includes much interesting information, some of which is briefly noted in the following:

A complete diver inspection of their wharf piling has disclosed the astonishing fact that 80 per cent of the creosoted pile failures were attributable to dog holes, permitting attacks of marine borers. The Board was the first large organization to use the Holmes patent cylinders, which consist of casting a concrete cylinder around a single pile or group of piles. The report states that the single green piles encased in concrete are successful if properly designed and constructed. They also report on the failure of a group of 1,200 eucalyptus piles, driven in 1908. The failure was due to breakage and to Xylotrya attack, and all were replaced in 1912.

BIOLOGICAL.-In order that progress may be made in detecting and reporting the presence and activity of marine borers, it is essential that their individual characteristics so far determined be given as widespread publicity as possible. Unfortunately, little is known and less has been written on the subject. The layman has been content to merge all of the Mollusca group into one type and call them "teredo” and all of the Crustacea group into one type and call them "limnoria.” This has served for all practical purposes to the present time, but since every source must be utilized henceforth in gathering information, it would be well to have a distinction drawn between Teredo and Xylotrya, and between Limnoria and Sphaeroma.

Two rough means are available for this purpose: The physical appearance of the borer; and the character of the burrows created by them, when a sufficiently large number are present. A brief statement of characteristics of the more common borers is given in the following. and has been prepared from descriptions furnished by Professor Charles A. Kofoid, of the University of California. At the end of these descriptions a tabulation has been prepared to provide convenient means of identification. Teredo Navalis Linnaeus (Mollusca Group):

This borer when full grown is usually from 14 to 18 inches in diameter at the head, and 4 to 12 inches in length. It may be four..) with greater length, but the above is more common, and it is desired here to show this form as the small borer, as compared to the larger Xylotrya. Its color is whitish and translucent. The boring action is accomplished with a pair of bi-valve shells at its head, which open and close "rubbing." or "filing” away the wood. At the tail are attached small, fat, doublepointed “pallets,” which prevent intruders from entering its burrow. These latter are the most distinctive features of their bodies, as compared to those of the Xylotrya, which serve for the same purpose, but are long and like feathers.

The Teredo first appears as free swimming larvas which have been released from the body of the female. Moving about in the water, they soon develop the pair of bi-valve shells, and with this additional weight tend to settle near the mud-line. If not destroyed by other forms oi marine life, and if the water contains sufficient food mourishment, they ultimately discover weak spots or irregularities in piling, or other timber substructures; and, having attached themselves, begin to bore in. They enter the piles horizontally through minute holes, the range of attack

usually being between mud-line and low-water. Having entered the pile they turn and work longitudinally with the surface in parellel symmetrical lines, their greatest activity being in the outermost three inches of the pile, but in this respect it is interesting to note that at Port Costa, they attacked in such large numbers that the entire pile cross-section was destroyed. Teredo seem to be able to thrive in brackish water, and are able to survive under alternating flows of fresh and salt waters. The burrow walls one lined with a whitish nacre secretion which readily can be scaled off. Teredo diegensis Bartsch (Mollusca Group) :

This form seems to be confined to the California coast, and has only been found in small numbers to date. Since it has not yet been a very destructive agency, its characteristics need only a brief description. It is the smallest of the Mollusca group, being only about 4 inches long. Other features are like those of the Teredo navalis given above, with the exception of the distinctive tail pallets. These are fork-shaped, with two long points, as compared to the short points of the Teredo navalis. Xylotrya setacea Tryon (Mollusca Group) :

This borer is the largest of the Mollusca group, usually being about y4 inch in diameter at the head and about 2 feet long. The color, boring action, and development from the larval stage are similar to that of the Teredo. The pallets are very distinctive, however, two of which are attached at the tail and have the appearance of feathers, often about 11/2 inches long. After having entered the wood horizontally through a minute hole, the borer rapidly expands to its full diameter. It then proceeds to bore in any direction, changing its course abruptly and often selecting the pile center section, apparently because of having it undisturbed by Teredo who are working in the outer shell. This abrupt changing of course distinguishes it from the Teredo. The Xylotrya does not seem to be able to live in polluted salt water, and is usually found where the water is clear and of high salinity. Limnoria lignorum Rathke (Crustacea Group):

This is a very small, flat, oval-shaped borer, with length about 14 inch and width about 3/32 inch. The back is covered with several smooth, curved armor “scales" which lap over and slide upon each other and are capable of adapting themselves to any curve of the animal's body. (For purposes of description, a popular comparison can be made to the commonly-known back armor of the armadillo.) It has two pairs of antennae, and seven pairs of legs. Under the head are four pairs of small biting “claws" with which it tears away the wood. It has no free swimming larval stage, and is apparently transplanted by the female moving from timber to timber and depositing eggs. These in turn hatch out and continue the propagation. Limnoria often cover a surface completely, there being possibly 200 on a square inch. Once having gained possession of a surface, they can succeed in repelling other borers. The area attacked is usually

between high and low tide levels. A characteristic of the Limnoria is
that it thrives in polluted water of high salinity.
Sphaeroma pentodon Richardson (Crustacea Group):

This borer has the same general appearance as the Limnoria, but is much larger, thus bearing a similar relation to the latter, as the Xylotrya does to the Teredo. Its width is about 14 inch, and its length about 1 inch. The color varies from dark olive to reddish brown. Its smooth, sliding back armor "scales” can easily be seen, and when disturbed it can roll itself into a ball about 14 inch in diameter. Its burrow is about 42 inch in diameter and usually remains near the pile surface, following the softer portions of the wood. This burrow being near the surface is quickly attacked by the Limnoria, and hence often obscured by being eaten away irregularly. The range of attack is usually between high and low water, and the borer thrives in all conditions of salt water, brackish, polluted, or of clear, high salinity.

From the foregoing it can be seen that the destruction of an unprotected timber pile can be complete if the borers enter the locality. Teredo will general honeycomb the outer three inches between mud-line and low water. Xylotrya will reduce the center section between mud-line and low water; Limnoria will eat off the pile between high and low tides, and Sphaeroma will burrow into the surface shell between high and low tides. Piles in brackish water can be destroyed by Teredo and Sphaeroma; in polluted water by Limnoria and Sphaeroma, and in clear water, at high salinity by all four types.

The foregoing also shows that the critical stage of marine borer growth for which all piles must be prepared is the larval condition. If the larvae can be repelled because of finding no untreated wood, or no irregularities or crevices in the surface, long life of the piles may be expected.

The following tabulation of Pacific Coast harbors gives the names of marine borers already discovered, and a statement of the length of life of creosoted fir piling. "Teredo” have commonly been reported at points where it is practically certain none exist, but rather Xylotraya of the teredo family. It is also probable that Sphaeroma exist at all these points but were not reported because of difficulty of inspection or failure to recognize them. The minimum life of creosoted piling roughly indicates the severity of attack, if treatment is imperfect or if a blemish is present allowing borers to secure a hold. The maximum life indicates the possibilities of the better quality of such piles. Untreated piling has not been listed because its life is negligible at these points, except #t Tillamook, Yaquina and Coos Bays, where borer attack is light and probably sporadic. It is of interest to note that the Teredodiegensis was given its name by Bartsch because of having been found in San Diego Bay.

ALASKA.—Xylotrya have succeeded in establishing themselves in Alaskan harbors and have created much damage. They appear to thrive in the cold, fresh, unpolluted salt water of that region.


« PreviousContinue »