, and with a
discharge capacity of more than 10,000 cubic feet a second. The seven
billion gallons of water that these pumps can move a day would fill a
lake one mile square and thirty-five feet deep.

Three of the canals empty into Lake Pontchartrain, the fourth, the
Florida Walk Canal, into Bayou Bienvenu, which leads into Lake Borgne,
an arm of Pontchartrain.

Because of this drainage contamination, the lake shore front of New
Orleans has been held back in its development. Yet it is an ideal site
for a suburb--on a beautiful body of water, and just half a dozen miles
from the business district.

So the Sewerage and Water Board has been planning ultimately to turn
the city's entire drainage into Bayou Bienvenu, a stream with swamps on
both sides, running into a lake surrounded by marsh.

The Industrial Canal crosses the Florida Walk drainage canal. This made
it necessary to build the inverted siphon.

A siphon, in the ordinary sense, is a bent tube, one section of which
is longer than the other, through which a liquid flows by its own
weight over an elevation to a lower level. But siphon here is an
engineering term to describe a channel that goes under an
obstruction--the canal--and returns the water to its former level.

Like the famous rivers that drop into the earth and appear again miles
further on, the Florida drainage canal approaches to within a hundred
or so feet of the Industrial Canal, then dives forty feet underground,
passes beneath the shipway, and comes to the surface on the other side,
in front of the pumping station, which lifts it into Bayou Bienvenu.

At first it was planned to build a comparatively small siphon, but
while the plans were being drawn, New Orleans entered upon its
tremendous development. The engineers threw away their blueprints and
began over again. They designed one that is capable of handling the
entire drainage of the city. And in April, 1920, it was finished--a
work of steel and concrete and machinery, costing nearly three-quarters
of a million dollars, and with a capacity of 2,000 cubic feet of water
a second, 7,200,000 an hour, 172,800,000 a day.

It was a work that presented many difficulties. First the Florida Walk
canal had to be closed by two cofferdams. The space between was pumped
out, the excavation was made, and the driving of foundation piling
begun. Quicksands gave much trouble. They flowed into the cut, until
they were stopped with sheet piling. The piles wer