"Creosoted Materials"

By CHAS. R. WILSON, JR., Chas. R. McCormick Lumber Cou, San Francisco

Chas. R. LViIson, Ir,

Due to the fact that the action of marinc borers has bccn so severe on the Pacific Coast. which condition runs back as far as can bc authentically .traced, governmental, munrcipal and large private industrial cngineering organizations havc rcalizcd the necessity and economy of timbcr preservation to prevcnt againgt this attack. Onq of the earliest pioncers on a large scale in this regard being thd Southern Pacific Railroad, which organization today operatcs a number of the largest and most modcrnly equipped crebsote timber treating planti in this country, howcvcr, although practically all thcir plants are built primarily to carry out the treatment of cross ties, these peoplc use a great number of creosoted piling in their wharf structures and ferry slips, as wcll as many miles of creosoted timber trcstlcs.

The life of a creosoted timber wharf structurc under average circumstances can bc anticipated conservatively at 25 to 30 years and due to the cost of such structure being approximatcly onethird that of any other typc of permanent construction, is the most economical. In order to warrant building a marinc structurc of any other material than creosoted timber it would ncccssarily have -to render a positive servicc lifc of ninety ycars. As the pcriod of obsolescehce in wharf construction is approximatcly 4O years thcre is no inducemcnt to build for longer life whcre it involvcs such very high costs. After a creosoted timber wharf has bcen in service 25 to 30 years it becomes nccessary in some cases to make repairs and in such cases the maintenance cost for the succeeding i0 to 15 years necessary to givc the wharf- a service lifc of 40 years, docs not run more than one-quartcr tbc original cost of the wharf, which in thc first place as previously statld is approximatcly one-third thc cost of any other type of Dermanent construction.

- Fis. 1 and 2 show cross sections of an untrcated pile placed in thi waters of the uppcr San Francisco Bay at Pittsburg. In' asmuch as ttrc rainlall in thc year 1923 had been somewhat undcr normal and due to the fact that thc streams arc being tappcd for irrisation and power dcvelopmcnt, the salt watcrs of the bay rec6dcd to this- point, carrying with it thc marinc borer attack and causing the damage shown, in the pcriod of six months. Previous to this time it had becn confidently thought that the salt watcrs of the bay could not and would not cvcr reach so far in thc uppcr bay. Salinity'tcsts have shown, howevcr, that thc waters wcre of-practically sufficient salt contcnt as far up thc Sacramento Rivei as Rio Vista, about 15 miles above Pittsbur& to suDDort the marinc borcr life.

the avcragc life of untreated piling in San Francisco Bay is 6 to 9 months. Harbor enginccrs have found it economical in this day to also crcosote the fender pilcs in watcrfront structurc€'

Fit. 4 and 5 show cross sections df creosoted piles in scrvicc in San -Francisco Bay 29 to 30 years. The wharf in which thcse pilcs wcre installeil was dismCntled, duc to the U. S. Enginccrs (War Department) having moved the pierhead linc inshore. Thc piles wcrc salvaged and redrivcn and arc today rendering lfi) per icnt capacity selvice in waters infcstcd with i'narine borers and are as s-ound as the day they were originally placcd. Thesc- piles alt told havc now becn-in seivice 36 to 37 ycars in heavily infcsted rratcrs in San Francisco Bay. In thc structure from which these piling wcre removcd after-!0 ycars' -service, th-erg.wcre -approl!- inatdiv 14,000 creosotcd piles. At thc time of dismantling this wharf, approximately 75 pcr cent of thc pilcs were in sound condition ind fit to rcdrive and arc today in scrvicc.

Fis. 4. 5 and 6 show somc'waterfront construction in San FranciscdBiv started in 1925 and completed this year. Fig. 4 shows l4-inch butt crcosotcd piles and l2xl2 crcosoted caps in place with creosoted 5xl0 sway braccs rcady to be placcd. Thc pilc driver preoaring to drive battcr or brace piles can be sccn in thc backcr6und. Fic. 5 chows crcosoted compound stringcrr 'lxl6 and ircosoted bridsins in placc rcady, for the laying of crco,soted tice. Fig. 6 showsireosoted 6xE tics in placc. Aftcr the rails arc olaccd oln thesc ties, crcosoted 4xl0 and 4x12 timbcr planking iri[ bc laid as a gub-foor to a Topcka deck.

Thc deceivinc Dart of the action of the marinc borer on untrcatcd piling, i-s ihat although the pilc may appcar sound on its surfacc, the interior may bc entircly honcycombed and the best way to detcrminc whcher or not thc wharf has bccn subje-ctcd to thc attack of the borcr is to pull scveral pilcs and section them for inspection. One method of inspection which. is gencrally used but, u;fortunatcln does not givc i reprcsentative lrrowled^g-e of the condition of the pile, is to go bclow the wharf at low tide in a small boat and cut into somC of thc piling with an axc. This somctimes cxt oses a light attack of thc borer and would inrii- catc that thc pile has not been sevcrely attackc4 but if this pile were pulled it would very probably show thc attack to be concentraied at thc mud-linc. This is duc to thc fact that thc specific gravity of thc larvae of tcredo is such that it movcs about with lhc cirrents on the bottom and becomes dcposited on the oilins at thc mud-line. The tcredo thcn enters thc pilc the iizc 6f a pin point and in six months or less, through- fast borings, groith -and brceding the pile has bccn endrely honcocombed.

The question of thc marinc borer has bccn very thoroughly investicited ovcr a period of thrce years by a body of very able ensin;rs and scicntists. Thia body of research intelligence toinca bv thc principal industrial and govcrnmental organizations of the Picific Coast is known as the San Francisco Bay Marine Piling Cornmittec and has investigatcd the p-roblcm of the marine borc""e irom cvcry possiblc anglJand has dcveloped^ a- means.of Drotcction to wharf structurcs against the ravages of this marinc icst Thc committcc is in position to furnish any tcchnical in-

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