The Forrest City times., 1899-07-28
RAILROADS OVER BOGS.
Oevices of Engineers for Crossins Dangerous Marshes - Mud
 Foundations.

The sinking of a section of the main hne of the South Pacific Coast (narrow gauge) railroad short distance south of the bridge across the entrance to San Leandro bay opens up new problem ir railroad engineering to be solved. Tn, roadbed traverses the salt marshes bor. dering the bay almost all the way from Alameda to Alviso, and in sop,e parts these marshes are very soft and cut il every direction by sloughs. in many parts the roadbed lies on a foundation of mud, to which there is apparently nc bottom; but so long as there is no room for the mud to shift or no agent at worI undermining it the roadbed stays i, place. The company has had much trou. ble, however, where the recent sub sidence occurred. It has subsided OF more than one occasion before, and it has taken a lot of new material each time to bring it up to grade. The diff. culty grows out of the fact that the road embankment at that particular point is swept at its base by swift tidal cur rent, which undermines the soft mud stratum and causes the roadbed to sliI in a body out of sight, leaving the rlili and ties hanging in the air. The trou blesome current is said to have a ve locity of 15 or 16 miles an hour. It i, intended to control it by damming the source, thus holding the water brought by the rising tide into the depressed marsh land in the neighborhood by pre- venting it's outflow.
 The marshes in the neighborhood ot San Francisco and adjacent bays have perplexed railroad builders since early days. In spots the mud is so deep that attempts to sound it have resulted ir the discovery of no bottom. At those points on the north arm of the estuary of San Antonia-that is, the arm con meeting Oakland creek with Lake Mer ritt-where the steam railroads serving Oakland cross, there is at least no feet of soft mud. There the engineers were forced to rely on suction to support the trestling, and the spliced piles in the middle of the First street railroad cross ing are said to be 110 feet in length and are held solely by the suction of the mud itself.
 All the piling constituting the foun, dation of the ferry building at the foot of Market street and much of tho piling driven into the made land or which the foundations of most of the big buildings in the lower Market street building rest are held in place by suction. So powerful is this suction o1 the soft mud that pile driven into il so far cannot be budged by the strokes of the heaviest triphammers used in pile driving, and the end of it will broom un. der the blows.
 The builders of the California Pacific railroad encountered much trouble with section of soft marsh land adjacent to Suisun. Time after time the entire road. bed sunk not only out of sight but out of soundings also, and stable founda. ton was only acquired after repeated filling in, the lower stratum of mate. rial being held in suspension, it is be, lieved, in the body of the mud, suction preventing it from subsiding further.
 The engineer of the Valley railroad has made a mattress foundation fol
 
 tne roadbed over the Martinez and San Joaquin marshes like the mattress foundation which Capt. Eads adopted for the levees constructed by him at the mouth of the Mississippi river. These mattresses are made of brush bound together with wire and laid on the surface of the marsh. Dredgeu then lift the mud cut ont of ths trenches on either side and deposit ii on these mattresses, thus forming an embankment that will carry when thor oughly settled, many times the weight it will ever be required to carry. These mattresses distribute the weight evenly over so large an area of the soft mud underlying the marsh that it does not perceptibly affect it, and the embank ment is practically as secure and per manent as if it were built on founda- ton of rock.-San Francisco Chronicle.