16 



have not proved to be of such irresistible nature against the 

 attacks of the teredo and limnoria as at first anticipated, 

 nevertheless the life of these piles will be greatly prolonged 

 and the present enormous expense for repiling somewhat 

 reduced in the future." 



In the period from 1895 to 1900 the Board in addition to utiliz- 

 ing coated and creosoted piles made a beginning in concrete substruc- 

 tures. The foundations for the Ferry Building were completed Sept. 

 1st, 1895. In this construction clusters of green piles aggregating 

 5200 were encased in rectangular concrete piers which were constructed 

 inside of an open coffer dam. Following this construction the sub- 

 structure for Pier 5 and for Folsom St. Wharf were constructed in 

 1896 of green pile clusters which were encased with concrete placed 

 inside of a cylindrical shell of 3-16 inch boiler plate. These types of 

 construction have proven satisfactory and the sub-structure supports 

 are still in use. 



About 1900 there was developed the concrete cylinder substruc- 

 ture known as the Holmes patent. In its earlier form this consisted in 

 the surrounding of clusters of green piles with a wooden stave cylin- 

 drical form driven into the mud and sealed at the bottom after which 

 concrete was poured for encasing the piles. 



From 1901 to 1907 Piers 7, 11, 19, 21, 23, 25 and 27 were built of 

 this type of construction. In the Biennial Report of 1908 the As 

 sistant State Engineer reports as follows: 



"There are practically two kinds of piers in existence on 

 the waterfront of San Francisco. One is the pier resting on 

 creosoted piles and comprises the remains of the old work, com- 

 pleted previous to the use of the Howard Holmes patent. The 

 other comprises the piers resting on piles protected by con- 

 crete according to Mr. Holmes' patent .... 



"Those of the first kind are very hard to maintain, and it 

 has been the policy of the Board for a long time to construct 



all new piers on the patented piles " 



But speaking of the patented piles he later adds: 



"In a few instances the concrete cylinder piers iiave failed 

 and fallen from their position. This latter failure is undoubt- 

 edly due to the practice of placing the concrete for a consider- 

 able portion of the bottom of the cylinders under iciter without 

 any special device to present a separation of the^ ingredients." 

 Since 1908 when the above was written the cylinder piers of this 

 type have likewise proven "very hard to maintain" and have been 

 generally repaired by replacement of faulty cylinders. These replace- 

 ments were due in part to the disintegration of poor concrete (proba- 

 bly poured into the sea water) but principally to failure to properly 

 seal the cylinders and encase the piles at the mud line. Numerous 



