Where the rotary broom is preceded by a street sprinkler, the dust forms into mud and clings to the surface of the pavement, and where the pavement is rough the mud is forced into the joints between paving blocks. As the street becomes dry, the dirt pulverizes and appears again as a dust nuisance. In all but one instance machine sweepers have been dispensed with in Chicago. South Water Street, the heavy wholesale fruit district of the city, is badly congested during the day, which makes it impossible effectively to clean this district by the “block” system. This street becomes very dirty during the day and is covered with a thick layer of dirt and débris at night. In this instance, the broom machines appear to be effective and give fairly good results in the cleaning of this coarse material.
The Chicago Commission believes that the mixing of calcium chloride with the water which is sprinkled in the different sections of the city would greatly add to the effectiveness of street cleaning and eliminating the perils of dust.
According to Very horse drawn brooms of the rotary style are not as effective as the hand broom.
Whinery says, “Sweeping by power sweepers at intervals of one or more days, while less expensive is far less effective and satisfactory than hand sweeping, though if properly done and supplemented by sprinkling with water or oil at intervals sufficiently near together to prevent dust flying it serves a good purpose.”
J. W. Paxton is of the opinion that the machine broom raises so much dust that heavy sprinkling is required. The fine dust mixed with water produces mud which is smeared on the street by the broom and when this becomes dry it turns to dust again. The broom sweeps only the coarser particles and many of these are thrown over the broom by centrifugal force to the pavement again.
In Philadelphia, machine broom cleaning is done in batteries of two or three, preceded by sprinklers, the number of brooms in each battery depending upon the width and character of the streets to be cleaned. The average gang consists of two machine brooms and one sprinkler, and four to seven broomers and a sufficient supply of wagons to remove the refuse, the number depending upon the haul to the dump and season of year, together with amount and character of traffic.