The comparative economy of the pumping system is shown by estimates
in detail of the cost of constructing and operating such a system in
contrast with, the cost of raising the grade and introducing tidal
sewers. Under both systems the cost of the ordinary sewers will be
about the same. A proper system of tidal sewers, it is claimed, will
necessitate the raising of the grade of the streets on the low lands
to a height at least ten feet above mean high water. The extra cost of
raising the streets is estimated at $3,000,000. The cost of the pumping
system, with machinery and power sufficient to remove all storm water
and sewage, is put at $150,000, while the running expenses, including
interest on the first outlay, are put at $30,000 a year. The interest on
the preliminary expenditure of the first plan considered is $180,000 a
year, or six times as much as the pumping system would involve.
According to the estimates made by Engineer Kirkwood, in his report
of 1874, a total pumping capacity of 134,500,000 gallons a day will
ultimately have to be provided to meet the requirements during the
heaviest storms, besides some six or seven million gallons a day of
sewage proper, exclusive of storm waters. Not more than half that amount
of pumping will be required at first, the increase to be made gradually
as the marsh land is built upon.
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