HAER Report

Construction Methods and Machinery

Once the BPC and its professional staff determined the activities necessary to prepare the river for parkway development, Downer set out to find the best method to execute the 1917 construction program. He noted that the type of work proposed by the BPC was relatively uncommon. The greatest challenge lay in devising a means to excavate the river at a reasonable cost without destroying the attractive natural features that remained. He explained that most of the work was "wet excavation, " which was far more complex than grading on dry land. Using hand labor to accomplish this task would be "exceedingly expensive." In addition, resorting to hand labor would make it nearly impossible to achieve a uniform depth along the river bottom. The wet excavation work was also unsuited for work by traditional steam shovels and similar machines. In many areas, excavating the Bronx River required working in very restricted terrain, which made it impossible to use the large dredges and scows ordinarily employed to deepen or enlarge river channels. The large suction dredges employed on major hydraulic excavation projects were not appropriate since there were no settling areas available to pump out spoil. In open sections along the river, Downer wanted to use machines that could excavate from the riverbanks. He required that the machinery be portable and easy to move between job sites.(175)

Downer consulted with experienced contractors to ascertain whether they were willing and able to work on the type of excavation required by the BPC. Tentative specifications for the excavation work were drawn up in hopes of inviting proposals. The subsequent bids were far too high for the commission’s budget. The contractors did not have the appropriate equipment and were unwilling to purchase it without being handsomely compensated. Downing also discovered that the contractors he consulted were annoyed by the strict contract terms required by the BPC, such as stipulations that they must preserve trees and other natural features and strip and store topsoil for future landscaping use. The BPC consulted with other park boards and learned that they, too, had found it impractical to use regular contractors for work that required the protection of landscape features. The consensus of the park authorities he contacted was that contractors’ work had negative effects on landscaping. Downer concluded that the best way to carry out river improvement, grading, and other tasks that affected the parkway landscape was to use the BPC’s own work force under close supervision of the landscape architects and engineers. The BPC decided that contractors would only be used to build bridges, sewers, and other conventional structures, since they already had the equipment and experience necessary to carry out those projects.(176)

Downer conducted an "exhaustive investigation" to ascertain what type of dredging machine could be adapted for BPC work. Downer noted that the BPC’s requirements were exceptionally stringent: the dredge had to work around overhanging trees and projecting roots; under low, arched bridges; in shallow water; and with limited space for discharged materials. Downer also wanted the machine to work well for both wet and dry excavation. He invited companies to submit designs, but few firms answered the call. The Bucyrus Company of Milwaukee informed Downer that it was building an excavator for use in the New York City subway and believed it could modify the machine to fit the BPC’s requirements. The Bucyrus machine could work in limited space, requiring only 6' of width and 6'-6" overhead clearance. The machine was equipped with caterpillar traction for dry excavation, but it could be easily adapted for use in the river by mounting it on a scow. Downer explained how the dredge could be modified with a belt conveyor to carry excavated materials between the trees that flanked the river and load it onto wagons or dump-carts. Downer visited Milwaukee for a demonstration of the machine and recommended that the BPC purchase it if it demonstrated the ability to successfully withstand the severe tests of the subway work.(177)