118 THE S£N FRANCISCO EARTHQUAKE AND FIRE. 
in the immediate vicinity of existing faults and near areas including 
any considerable amount of made ground, both conduits and mains 
may be expected to suffer serious damage. At one point on Van 
Ness avenue (see B, PI. LVI), where I happened to see the mains 
uncovered, a heavy water pipe, apparently about 20 inches in diame- 
ter, had been broken into pieces not more than 2 feet long. The total 
length of the break, however, was not more than 40 or 50 feet, so far 
as I could judge from what I saw uncovered. It would seem that this 
main might have been spliced in a few hours had there been some 
means of rapidly plugging the broken ends on either side of the 
break and making a number of taps in the undamaged parts with 
parallel lengths of fire hose of large size. With gate valves at short 
intervals it ought to be possible to cut out any damaged portion of 
the system by connecting through with fire hose in such a way as to 
maintain at least a partial supply of water for fire-fighting purposes. 
Some similar plan on a larger scale might be devised for repairing 
conduits. 
It would also seem desirable, wherever an important conduit or 
main crosses filled ground or material soft enough to suffer con- 
solidation as a result of thorough shaking, to carry the main on piles 
or other foundations reaching to firm material below. Wherever 
there was filled ground the vibration due to the earthquake seemed 
to have much the same effect as would be produced in a vessel that 
had been loosely filled with sand and then subjected to vibration ; as 
is well known, the sand, under such circumstances, will suffer con- 
solidation to a very appreciable extent, which naturally lowers its 
surface by an amount corresponding in a general way to the intensity 
of the vibration. Where a large area and volume of made ground is 
subjected to similar vibration, subsidence occurs, and not only are 
buildings on the surface thrown down and destroyed, but water 
mains, sewers, etc., running through the filled material are subjected 
to a deflection which necessarily shatters them. 
SEWERS. 
The effect of the earthquake on sewers seemed to be practically 
the same as on conduits and water mains, except as varied by differ- 
ence of material, where such difference existed. The necessity for 
firm foundations for sewers running through made ground is clearly 
indicated. The need of rapid repairs to the sewers is not quite so 
great as in the case of the fire mains, because a city can get along 
with inadequate sewerage facilities, if necessary. It would seem 
desirable, however, that all important sewers passing through made 
ground should be constructed of the heaviest iron or steel pipes, and 
be provided with an adequate foundation. Of course* sewers are not 
