Economic Water System Alterations
How the City of Philadelphia Took Advantage of Subway Construction, Thus Avoiding Expense of Excavations—Some Problems Involved
THE following paper outlines some of the problems met by the Bureau of Water, Philadelphia, in connection with the building of the subway in that city, and also shows how the bureau took advantage of the work to relocate and alter old mains and pipes which had been laid for some years:
To visualize the water distribution system and its relation to Broad Street where the present work on subway construction is active, it is in order to digress from the main subject and outline briefly a history covering location and water lines involved.
History of Philadelphia’s Water Supply System
An early means of furnishing water to Philadelphia was through a pumping station located and built during the year 1799 on the Schuylkill River at Chestnut Street. Here an engine of 1 1/2 m. g. capacity pumped through a circular brick conduit built on Chestnut St. to Centre Square on which now stands the Public Buildings—City Hall—at Broad and Market Streets. The building, with a pumping installation of 1 m. g. capacity, was erected on Centre Square in 1801 and was removed during 1829 at which time a supply of water was being furnished from the Fairmount Works.
The construction of the subway under the existing City Hall uncovered sections of the masonry flume referred to above and excavations on Chestnut Street have at times involved this old structure.
Following the Fairmount Works were those located in 1848 at Girard Avenue called the Spring Garden Works from both of which were pipe lines conveying water to reservoirs and the laying of 48, 36 and 30 inch mains were required to furnish with a supply of water the rapidly growing city. A glance at the map of Philadelphia will disclose Broad Street, the location of which marks closely a midway line between the Schuylkill and Delaware Rivers—for a length of approximately seven miles. Further observation shows the street system being developed with two main thoroughfares forming somewhat a means for transit and utility convenience.
Market Street being laid out at an earlier date has borne cars on its surface from and including the horse drawn period to date but a recognition of Broad Streel as an attractive avenue for vehicles has kept it generally clear from surface or elevated common carriers.
Approaching the year 1900 the largest water pipe occupying Broad Street was a 30″ in size. A number of smaller mains were laid for the consumers’ service and due to the roadway width these were placed on each side but not under the footways.
Filtration Construction Causes Radical Change
Upon the construction of the filtration system a radical change was planned for the supply of water east of the Schuylkill River. An impressive addition to the water works included a large filter plant at Torresdale with an imposing pumping station at Gardner’s Point from which Delaware River water would he delivered through an extensive pipe system for express and service purpose. The existing mains had been designed to distribute a supply of water pumped from the Schuylkill and much of this system was continued to serve as trunks for the passage of water from the Delaware source, all of which made necessary a reverse flow through the mains. Such a design for a distribution system was far from ideal and considerable distortion was practiced to effect a flexible system. The filtration planning contributed to Broad Street a 48″ trunk main and upon the water introduction to this design, the distribution system was functioning with a draft of 65 and 35% respectively from the Delaware and Schuylkill Rivers. During the last two decades a pipe system for fire fighting purposes was added throughout a considerable length of this same street. This main is 12 and 20 inches in size and with the connecting fire hydrant lines contributed an additional structure to maintain.
Subway Construction Gives Opportunity for Alterations
The studies on subway construction offered the bureau of water the opportunity to iron out some of the pipe installations which had resulted from a time to time addition, a record of such connections being only in the minds of former employees.
Generally a policy was adopted to remove and relocate the large mains lying parallel with the axis of Broad Street and to raise those of the important trunks which were on intersecting streets. An early policy adopted on one contract held to hanging the service mains from the deck of the timber bridge which formed the vehicular surface. The vibration due to the passage of trucks and cars and the shock imposed by the use of dynamite caused innumerable breaks which because a general nuisance to the contractor excavating below decks and likewise the loss of water to the householder and business plant raised a storm of protests. A general laying a new pipe was resorted to in a location adopted under the footway and the new line was charged before the services were transferred. This method of operation was extremely satisfactory and much confusion was eliminated. On such sections where large mains were crowded out a parallel street was selected to provide a location for new pipe. A section of the work through a congested area will not admit of this transfer and it is purposed to relay a 48-inch main over the masonry roof of subway—reducing at station locations to twin 36-inch mains.
“The studies on subway construction offered the bureau of water the opportunity to iron out some of the pipe installations which had resulted from a time to time addition, a record of such connections being only in the minds of former employees.”
* Excerpts from paper read before the annual convention of the 4-State Section, American Water Works Association.
Relocation of High Pressure Fire Lines
The High Pressure fire lines were moved to a location generally under the footway requiring also the relocation of many fire hydrants. No breaks have occurred on this system of piping and during subway construction line has been supported by 12 x 12 posts.
One break of a serious nature has occurred on large pipe—this being where active work was under way on a 48-inch crossing Broad Street, the location of which required a radical adjustment to permit the passage of the subway. The break took place at an hour when workmen were few and the sub-surface supports took splendid care of the flood.
The raising of a section of 48-inch steel pipe marked an unique piece of work. The elevation of this pipe was low for the subway section which in turn could assume no lower level due to the existence of a trunk sewer over which it must pass. During the activities of the existing contracts there have been involved 26,000 lineal feet of 48, 36 and 30-inch pipe together with 64.000 lineal feet of 12-inch and smaller, all of which construction has been executed by the contractors’ force under expert inspection.
Cooperation with Transit Department
The water bureau assigned selected men to handle valves in case of trouble and a most harmonious coordination with the constructive interests has been in effect. Where lines were relaid holding to equal sizes, the expense of pipe and laying was borne exclusively by the transit department. In the event of a larger main being planned such as the service mains which were formerly six inch, the bureau of water met the difference in cost. Pipe of all descriptions have been encountered: bored wooden logs laid prior to 1820 and cast iron brought from England some of which were imported as early as 1817 and following were the domestic contributions of C. I. bell and spigot; C. I. flange; C. I. Universal and Steel.
Some Interesting Incidents During Work
The handling of each and all has placed no unusual burden on the department’s force and many times during this construction have happened incidents which have injected a humorous cast to the outsider looking on. There might be reference to the consumer, even though notified, who, finding no water in his fixtures, due to a shift of service, left home and upon returning discovered a modest flood; the general protest along certain sections of unskillful operations of the city’s filter plant and the careless use of chemicals which gave an odor and taste to their water; and the consumer who would suffer a loss of service due to the sawing off and appropriation by persons unknown of the temporary lead services exposed but hidden below decks. All insignificant occurrences to us in general, hut of extreme moment to the individual involved.
No large work can proceed with any satisfactory progress without skill and coordination of interests concerned and the writer takes great pleasure in referring to the splendid way which the contractors have executed their work and the generous way all concerned have contributed their efforts.