THE SEWERAGE OF NAHANT.

THE little town of Nahant, one hundredth part the area of Plymouth, was considerably disturbed during the latter half of 1881, and the first half of 1882, by the appearance of typhoid fever in various parts of the town.

The questions then presented for solution were,

1st. What was the cause of disease?

2d. What should be the remedy?

3d. How long would it take to give relief?

4th. What would it cost?

The disease being zymotic, the remedies suggested were largely those that would be prescribed by a Board of Health -cleaning of premises, securing better drainage, plumbing, etc., and removal of all decomposing matters; afterwards trying to better the quality of water, ice, milk, etc.

Without going into details that would prove but repetitions of what may be already fairly well known, the writer desires to call attention in as few words as possible to those portions of the work that may not be so well understood; viz., separate sewerage, and the apparent recovery of the soil after pollution.

The former of these two subjects is better understood, perhaps, than the latter, although still imperfectly known in this country.

The latter subject, so far as the writer's knowledge extends, has never been discussed in print before, and although isolated cases have been noticed where soil was recovered, to greater or less extent, yet it has apparently either been overlooked, or considered as of small moment.

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It being determined to construct a system of sewers, the separate" system was adopted, as less expensive and quicker to build. It was argued that if manholes were placed at all junctions, and changes of direction, whether

vertical or horizontal, it would be comparatively easy to flush with water, or clean with rods, chains, brushes, etc. (See Figs. 1, 2 and 3.)

On questions relating not only to the preliminary selection of materials, but actual constructive work and maintenance, the writer borrowed freely on all sides, and though usually the methods heretofore employed by other engineers answered the purpose at Nahant, occasionally slight modifications and additions were made that seemed desirable.

Particularly was this the case with the apparatus for cleaning the sewers, and in the arrangement for the ventilation both of sewers and private drains.

The requisite capacities for the sewers were figured, on a basis of the area to be served, the proposed grade for each pipe, the velocity of flow of sewage, in every case, and the quantity of sewage that might be delivered at given points during those hours when plumbing would be in greatest use (between 8 and 10 A.M.). The sizes for pipes, thus determined by calculation, were doubled, so that when in maximum use they would run one-half full. Although many of the lateral sewers, figured on this basis and doubled, should have been four-inch pipes and not larger, the difficulty experienced in obtaining sufficient quantities of pipe of that size, straight enough to admit of inspection between manholes placed 250 feet apart, was so great, that six-inch pipe was selected as the minimum size.

Actually constructed, the sewers vary in size from six inches to eighteen inches in diameter, and are, so far as possible, laid with tight joints, excluding all ground and surface water. At the present time, the only water purposely admitted to any of the pipes, other than house sewage, is the rainfall from the roof of one school-house', that covers. an area of 1,300 square feet. This was connected, as that part of the sewer was what is termed a "dead end" and received the sewage from one house only.

It is believed that the pipe system at Nahant represents to-day the only thorough system of separate sewers in this country. They certainly can be pointed to as the only system of separate sewers that are operated without public water of any description, and that in certain sections have