Amputating Pittsburgh's "Hump" 



THE "Hump" in Pittsburgh was a 

 hilly prominence upon which stood 

 the County Courthouse. Ad- 

 joining it were the Frick, Carnegie, and 

 other large sky-scrapers. It impeded 

 travel. Hence it was decided to remove 

 the "Hump." This involved the cutting 

 down of fifteen thousand feet of city 

 street, and affecting twenty-two im- 

 portant city blocks. 



In this district thirteen public service 

 corporations had underground conduits, 



cables, pipes, 



etc. 



In the busi- 

 ness section 

 of most large 

 American 

 cities the 

 overhead 

 wires and ca- 

 bles have 

 been so ef- 

 f e c t u al 1 y 

 placed under- 

 ground that 

 nothing re- 

 minds us of 

 the mechan- 

 ism whereby 

 water, gas 

 and electrici- 

 ty are sup- 

 plied a few 

 feet beneath 

 the surface of 

 the street. 



Particular- 

 ly difficult 

 was the task 

 of maintain- 

 ing in opera- 

 tive condi- 

 tion seven 

 thousand, 

 two hundred paper-insulated cable wires 

 contained in lead cable-sheaths. These 

 cables, twenty-one in number, were 

 originally drawn into vitrified clay con- 

 duits and spliced in manholes located at 

 the street intersections. When the cut- 

 ting of the "Hump" proceeded and the 

 street was down to the level of the con- 

 duits, it was found that the drilling and 



How the cables carrying most of Pittsburgh's telephone 



conversations were taken care of until the new conduits 



were ready for use 



blasting in the immediate vicinity shat- 

 tered the conduits, so that further exca- 

 vating would cause the conduit line to 

 collapse. The clay conduits were broken 

 off the cables and the cables were planked 

 up in a box or trough. Alongside the 

 plank box was the trench, twenty-two 

 feet deep, in which a conduit line was 

 to be constructed by what is known 

 as the "split duct" method. These 

 special conduits are scored lengthwise 

 inside and outside before being vitrified 



or baked and 

 can be easily 

 split in two. 

 After a layer 

 of half-ducts 

 is laid in ce- 

 ment, it is 

 possible to 

 place the ca- 

 bles in posi- 

 tion and re- 

 place the top 

 halves of the 

 ducts. 



This pro- 

 cedure of low- 

 ering the tel- 

 ephone cables 

 into split 

 ducts saved 

 about $40,- 

 000 which 

 would have 

 been expenrl- 

 ed in purchas- 

 ing new un- 

 derground 

 cable to be 

 pulled, splic- 

 ed and cut 

 into service, 

 to say noth- 

 ing of the oc- 

 service and 

 the working 



casional interruptions of 

 confusion in transferring 

 lines from the old cables to the new ones 

 The cables thus lowered below the new 

 grade of the "Hump" cut contained 

 three thousand, four hundred and eighty- 

 one miles of copper wire, paper-insulated, 

 twisted into pairs and enclosed in a lead 

 sheath. The time required to accomplish 



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