150 TUNNELING 



timbering is accomplished. In such cases the cost of the 

 method used cute a small figure, so long as it is safe and 

 expeditious. 



BALTIMORE BELT LINE TUNNEL. 



The Baltimore Belt Ry. Co. was organized in 1890 by 

 officials of the Baltimore & Ohio, and Western Maryland rail- 

 ways, and Baltimore Capitalists, to build 7 miles of double track 

 railway, mostly within the city limits of Baltimore. This rail- 

 way was partly open cut and embankment, and partly tunnel, 

 and its object was to afford the companies named facilities for 

 reaching the center of the city with their passengers and freight. 

 To carry out the work the Maryland Construction Co. was 

 organized by the parties interested, and in September, 1890, this 

 company let the contract for construction to Rayan & McDon- 

 ald of Baltimore, Md. The chief difficulties of the work cen- 

 tered in the construction of the Howard-street tunnel, 8,350 ft. 

 long, running underneath the principal business section of 

 the city. 



Material Penetrated. The soil penetrated by the tunnel 

 was of almost all kinds and consistencies, but was chiefly sand 

 of varying degrees of fineness penetrated by seams of loam, 

 clay, and gravel. Some of the clay was so hard and tough that 

 it could not be removed except by blasting. Rock was also 

 found in a few places. For the most part, however, the work 

 was through soft ground, furnishing more or less water, which 

 necessitated unusual precautions to avoid the settling of the 

 street, and consequent damage to the buildings along the line. 

 A large quantity of water was encountered. Generally this 

 water could be removed by drainage and pumps, and the earth 

 be prevented from washing in by packing the space between the 

 timbering with hay or other materials. At points where the 

 inflow was greatest, and the earth was washed in despite 

 the hay packing, the method was adopted of driving 6-in. per- 



