The Sewerage of Sea Coast Towns

is an entirely new one the quantity must be estimated. If there is a water supply system the amount of water consumed per day, after making due allowance for the quantity

WATER

per head

ng, &c.) 1 Cleansing purposes (was

ts are in gene

e in genera

ta

the resident inhabitants. The problem is complicated in sea coast towns by the large influx of visitors during certain short periods of the year, for whom the sewerage system must be sufficient, and yet it must not be so large compared with the requirements of the residential population that it cannot be kept in an efficient state during that part of the year when the visitors are absent. The visitors are of two types-the daily trippers and those who spend several days or weeks in the town. The daily tripper may n

n the quantity of sewage flowing into the sewers is very great, but it reduces as the population increases, owing to the diversity of the occupations and habits of the inhabitants. In all cases where the residential portions of the district are straggling, and the outfall works are situated at a long distance from the centre of the town, the flow becomes steadier, and the inequalities are not so prominently marked at the outlet end of the sewer. The rate of flow increases more or less gradually to the maximum about midday, and falls off in the afternoon in the same gradual manner. The following table, based on numerous

LE N

Y VARIATION IN TH

tal Flow Passing

6 | 0.5 | 0.7 | 0.8 7.0 " | 0.5 | 0.5 | 1.0 | 1.5 | 1.6 | 1.7 | 2.0 | 2.5 8.0 " | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 5.0 9.0 " | 3.5 | 4.5 | 4.5 | 4.8 | 5.5 | 5.8 | 6.0 | 6.5 10.0 " | 6.5 | 6.5 | 6.8 | 7.0 | 7.5 | 7.7 | 8.0 | 8.0 11.0 " |10.5 |11.0 |10.5 |10.0 | 9.6 | 9.3 | 9.0 | 8.8 Noon |11.0 |11.3 |10.8 |10.3 | 9.3 | 9.5 | 9.2 | 9.0 1.0 p.m. | 6.0 | 5.5 | 6.0 | 6.7 | 7.0 | 7.2 | 7.3 | 7.5 2.0 " | 7.0 | 7.3 | 7.0 | 7.0 | 6.5 | 6.5 | 6.2 | 6.0 3.0 " | 6.8 | 6.5 | 6.5 | 6.5 | 6.5 | 6.3 | 6.3 | 6.0 4.0 " | 7.5 | 7.5 | 7.3 | 7.

SIS O

flow passing off d

---------------

ulati

--+----+----+

0 | 4,000 | 5,000 | 6,

----+----+----+--

3 | 78.8 | 78.6 | 78.7 |

7 | 21.2 | 21.4 | 21.3 |

83.6 | 82.6 | 81.7 | 81

| 72.1 | 71.4 | 70.0

66.1 | 65.6 | 64.5 |

61.4 | 60.8 | 59.5 |

43.1 | 47.5 | 46.8 |

27.11| 27.3 | 26.8 |

21.3 | 20.3 | 19.3 |

| 10.8 | 10.3 | 9.

3.9 | 5.2 | 6.6 | 7.

8.7 | 9.8 | 10.7 |

----+----+----+--

ate to populations of one, five, and ten thousand r

e allowance must be made accordingly. The greater the amount of extra liquid flowing in the sewers as a permanent constant stream, the less marked will be the hourly variations; and in one set of gaugings which came unde

12 Hourly Variation

to be watertight before the trenches are filled in; but in practice this happy state is not obtainable. The pipes may not all be bedded as solidly as they should be, and when the pressure of the earth comes upon them settlement takes place and the joints are broken. Joints may also be broken by careless filling of trenches, or by men walking upon the pipes before they are sufficiently covered. Some engineers specify that all sewers shall be tested and proved to be absolutely water-tight before they are "passed" and covered in, but make a proviso that if, after the completion of the works, the leakage into any section exceeds 1/2 cubic foot per minute per mile of sewe