p15  Part II
Statement of General Requirements

An investigation into the principal features and outlines of a drainage system for the City of New Orleans will be made with a view of realizing the inevitable growth and development of the city, and the increasing demands which, at the present time, sanitation, comfort and economy make upon every large modern community.

In the past it was deemed sufficient to adopt makeshifts, one after another, to accomplish some immediate ends and to benefit small disconnected sections. The result has naturally been: a somewhat incoherent and crude system of drains and canals, insufficient in size, depth and slope; a disposal of the water which, regarding its main channels and outfalls, is becoming more and more objectionable; and methods of pumping which are both inefficient and uneconomical.

It has now become clear not only that the city will steadily advance in size and importance, but that means will become available, in proportion to its growth, to better the streets, the railway service, the lighting and water supply, the pavements, the sewerage and also the drainage. Any material improvements of the city that are now instituted, should no longer be temporary expedients, but based upon well digested plans designed to provide for all future contingencies, so far as these can be safely estimated.

The recent establishment of a sewerage system, which is to remove from the buildings to a proper outfall, all foul waste matters that can be carried away in suspension by flowing water, has in some degree affected the drainage question by removing from consideration an element that would have caused a material modification of the problem.

The drainage question of this city to‑day, therefore applies principally to the removal of the rain water falling upon the inhabited and built-up part of the city, which does not penetrate the ground, but runs off into the gutters, and then floods the streets and finally the low territory, causing more or less damage to property and interfering with travel and the transaction of business. It applies likewise to the removal of the ground water which at present saturates the soil, causing unsanitary conditions, besides preventing the usefulness of the territory, for one or another purpose as may be required in a large city.

Many blocks in the city which are not now built up because they are practically swamps, although within convenient distance of the business center, will likewise be benefited by efficient drainage.

A drainage project should therefore be extended to all territory which is now, or will be, built up in a reasonable time, and it should see the removal of rain and ground water from the same, so that the whole area can be made and kept thoroughly dry. This area has been limited for the present purpose as follows, viz.: On the left bank of the Mississippi River, of the territory embraced by the Upper Protection Levee, Lake Pontchartrain, People's Avenue Canal, Florida Avenue and the lower limits of the city; and on the right bank of the Mississippi  p16 River, the line between the parishes of Orleans and Jefferson, the lower side of the naval reservation and rear protection levee, all as shown on Plate IV.

The lowness of the land requires all of the rain and ground water to be lifted by pumps, before it can be actually disposed of. As the area is one of great magnitude, the required pumping capacity will be considerable, and it becomes necessary to adopt such methods of collecting and conveying the water, as will enable the most economical pumps and arrangements to be used. It also becomes a matter of moment to ascertain the most economical lines, sizes, depths and slopes of the canals to facilitate such removal in the most efficient way.

A further important requirement of a drainage plan is the final proper disposition of the water. Since, in the near future, most of the sewage will be separated from the drainage water, it is to be assumed that the latter will soon be much improved in quality, although still containing street washings and leachings from the soil. The storm water from heavy showers is less objectionable in quality. The high dilution of the organic matter will render it inoffensive and harmless, notwithstanding the water may be more turbid from a larger amount of suspended earthy matter that is contained in it.

The question of disposal must be answered in the light of these two conditions of the water. Its ordinary flow should not be delivered where even its slight pollution would be undesirable or detrimental to the value of adjoining lands. It would if possible be discharged at points where no considerable development is expected.​a

The first flow from a storm generally carries with it the washings from the streets and houses, and is also to a certain degree polluted. It is therefore advisable to treat it like the ordinary flow. The water from heavy rain-falls, however, so largely dilutes the waters just mentioned, that it can be considered quite unobjectionable, at least from a sanitary point of view, and discharged at the nearest available points into any natural water course or lake. As it may sometimes gather up and carry along considerable quantities of silt, due to its greater velocity, care must be taken that no detriment to the canals results therefrom.

The final requirement is the maintenance of the two existing navigation canals to best subserve the demands of commerce. It has been suggested, and with some good reason, that the river end of these canals as far as Broad street might be abandoned for navigation and made available for drainage, but on the lake side of Broad street they should be preserved and kept free from surface water, on account of resulting deposits.

Any plan satisfying all of the above-mentioned demands must necessarily be comprehensive; it must cover a large and now mostly uninhabited territory, and a long time will be required to execute the same. As some of the demands are now urgent, and should be satisfied as soon as practicable, the plan should therefore allow of the possibility of at once carrying out some portions independently of others, so that it will solve the present difficulties efficiently and economically, and at the same time be in harmony with the whole work and facilitate eventual extension and completion.

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Thayer's Note:

a The vagueness of this, combined with a much more rapid expansion and development of the area surrounding New Orleans than seems to have been expected, is one of the two principal causes of many of the drainage problems facing New Orleans today, since areas available for water discharge are now inhabited suburbs. The other is that all this pumping and de-saturation of the soil has resulted in massive subsidence, thus lowering the levels in the city even further below that of the Gulf.

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