p39  Part V
Prosecution of Work; its Proper Order and Extent

Without prejudice to its final completion the plan allows great latitude in the order with which the construction of its several parts may be undertaken in any section. It also permits the execution of effective work to any extent however small or great for which means may be, or may become, available. Almost any one of the numerous canals, branches, drains, pumps, etc., proposed in the plan, may be built with the certainty that its immediate effect will be to relieve, to some extent, certain parts of the city from their present unsatisfactory condition as regards drainage, and that the work done will be of permanent and increasing value, as the extension of the plan proceeds.

But the largest benefits will, in general, closely follow the locality where the works are most nearly complete. Thus, if only the Main Canal, with its Pumping Stations and Relief Branches were put in operation, the drainage of their immediate vicinity would be at once accomplished; though little or no benefit would result to the remoter regions until they were penetrated by the Branch Canals and Drains, designed to carry off their drainage, and these conduits were, in turn, connected with an improved system of street grades and gutters.

On the other hand it is evident that while the grades and gutters of the streets in any portion of the city may be so improved as to greatly facilitate drainage, such improvement can only effect a local benefit, the Main Drains, Canals and Pumps being necessary for the final disposal of the run‑off. Both parts of the plan, the pumps and main canals, as well as the minor channels and improved street grades and gutters, are essential for the efficient drainage of any of the sections. Nevertheless, the several sections may be separately treated, in case considerations of finance or policy, or other reasons, are found to make such a course desirable. But no part of the improvement should be undertaken which in its effect, increases the quantity of water collected at any point, without providing for the necessary pumps and canals to properly dispose of it.

As it is proposed to discharge the excessive volumes of storm-water, brought to the Main Canal from the upper sections of the city, into Lake Pontchartrain by means of Relief Branches and Auxiliary Pumps, it is of course entirely practicable to allow ftp, all the run‑off, both from excessive storms and from daily flow, to be discharged from any of these sections into Lake Pontchartrain. The drainage thus carried to the Lake would not be more polluted than that now delivered there, and whenever the Main Canal was completed for service, any nuisance would be at once abated, and the operation of the system could, thereafter, proceed in accordance with the completed plan, and the drainage be delivered into Lake Borgne.

 p40  While the ultimate construction of the Main Canal to its outfall through Bayou Bienvenu, into Lake Borgne, is an essential feature of the plan, its completion as a continuous channel of discharge may, if time or means are wanting, be postponed, and only such parts of its length as are necessary to convey the run‑off from the several sections to the nearest pumping stations, or to serve for storage purposes need be built until it is found convenient or necessary to do so. But whatever parts of it are undertaken should be made of the ultimate cross-section required, and all parts, at least between the New Canal and St. Bernard avenue, should be lined when they are constructed.

In general, all canals, branches and drains between the river and the Main Canal, should be lined with Masonry, and many of them covered with the street pavements; but those between the Main Canal and the Lake may be left without lining for years to come.

The enlargement of existing canals between the Main Canal and the Lake, as well as the cutting of new ones, or their subsequent enlargement, can mostly be done with dredging machinery, and the total cost should not be increased by undertaking the work in instalments, that is, by opening canals of moderate sizes at first, and afterwards enlarging them.

Canals and drains between the Main Canal and the river should, in general, be lined as they are built, though the covering of the larger ones may be omitted without impairing their efficiency as drains. In some cases, where they occupy narrow streets, the absence of covering would result in considerable public inconvenience and, in a few instances, might leave such streets useless as avenues of travel, which, presumably, could not long be tolerated. It would, therefore, appear proper to prosecute the work on most of the canals and other conduits between Broad street and the river, under specifications requiring them to be lined and covered; and the estimates hereinafter presented contemplate such lining, except in certain specified cases, and the covering of all drains between Claiborne street and the river, with certain others mentioned.

It will of course be necessary for public convenience to build bridges at numerous points across all uncovered canals and branches, but as this work should not in any way increase or diminish the capacity of the channels for drainage, it is considered as forming no essential part of the plan, and its cost is not included in the estimates.

Care should be taken that whatever bridges are built shall not obstruct the free flow of the Canals, and as far as possible all bridges crossing the larger Canals and Branches, especially on the Lake side of the Main Canal, should be so constructed as to facilitate the passage of dredge boats.

Since the run‑off which the drains and branches are separately designed to carry cannot be expected to reach the pumping stations to which they are tributary simultaneously with full volumes, it follows, as already stated, that the maximum capacity of the plant at any station may be less than that which would be required to pump the  p41 sum of the several rates of run‑off which may be delivered into the Main Canal. The pumping plant as first installed, therefore, need not be of full aggregate capacity, and for the further reason that, until larger areas of the city are paved and improved the ultimate capacity cannot be called for, even though the entire system of canals and drains were complete, and, also, that it cannot be presumed that the entire plan will be put under construction at once, or that its execution, even when undertaken, will be completed so rapidly as to make the full-powered plant an early necessity.

It would appear to be good policy to install pumping plants at most of the stations, only as fast as it may be found necessary to keep pace with the construction of the canals, drains, etc., as they are undertaken. The stations should be so designed that pumps comparatively small in capacity, or in number, merely effectively installed at first, and subsequently increased in capacity or number as occasion arises, and to any required extent.

For reasons stated on page 36, the estimates hereinafter ZZZ preed include provision for a Pumping Plant of a capacity to discharge approximately two-thirds of the aggregate of maximum run‑offs for which the drains and canals are designed; but the instalment of the plant to any such extent cannot be recommended until experience proves its necessity.

That part of the Second Section lying between Broad street and the river, on account of the concentration there of improved properties, paved streets and business houses, and of its central position with reference to the most densely inhabited area of the city, is now more urgently in need of improved drainage than other localities, and it is evident that the benefits to be derived from the execution of the plan, would be of greater immediate public value there than in any other section of the city. It hence suggests itself that this section may properly receive the first attention in the prosecution of this work, and a special estimate of cost has accordingly been prepared for it, so that, in case the City Council should desire to undertake this work, before arranging for the execution of other parts of the plan, it may proceed intelligently.

The relative order of importance, for the execution of the several parts proposed in the Second Section, is as follows:

1st. The construction of the Pumping Stations, Nos. 2 and 7, with the improvement of the Relief Branch Canal connecting these Stations.

2d. The construction of the St. Louis Branch Canal with lining and covering, or the acquirement and adaptation of the Carondelet Navigation Canal for drainage purposes set out Broad street.

3d. The Main and Branch Drains between Broad street and the river, to be lined and covered.

 p42  4th. The improvement of street grades and gutters. Such improvements, however, should not be delayed on account of the non-completion of other parts of the work, though it can accomplish little of itself in the way of drainage, except to relieve one locality by flooding another.

5th. The improvement of the Orleans Relief Outfall Canal.

6th. The construction of Main and Branch Drains between Broad street and the lake.

7th. The construction of the Main Canal and its connection with the sections above and below.

The work in other sections may be prosecuted in any order, or at any time, as it may be found most convenient. Whatever is done towards carrying out the plan in any section, cannot be injurious to the interests of other sections, whether or not they are directly benefited.

The First Section has the largest area, and, at present, its tendency towards increase in population and improvement, is probably more apparent than that of the other sections. But whether or not this tendency will continue as notably in the future as in the past cannot be predicted. A part of the drainage under existing arrangements, is discharged into the New Orleans Navigation Canal, a condition of affairs which will probably require change, and some work under the new plan may soon be demanded for that purpose.

The work in the Algiers Section, on account of its comparatively small size and cost might be done with less means than would suffice for much effective work in other sections, and hence might be undertaken at an early date.

In the Third, Fourth and Fifth Sections, the situation and conditions are so similar, as to offer, at this time, no suggestion of priority in date, or of limit in the extent to which work should be undertaken.

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Thayer's 5

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