Milk and its relation to the public health . Fig. 54.—Showing how a cesspool located on high ground may fail to pollute a well lower : Practical Hygiene; Phila. and N. Y., 1901, p. 324. through a porous soil that has become saturated or finally by the in-tentional or accidental introduction of impurities, it is necessary toguard against each of these sources. WELLS. To guard against the pollution of wells the location is of impor-tance. Where it is possible the ground should slope away naturallyon all sides, and the pump should be on top of a mound which shouldbe well sodded or
Milk and its relation to the public health . Fig. 54.—Showing how a cesspool located on high ground may fail to pollute a well lower : Practical Hygiene; Phila. and N. Y., 1901, p. 324. through a porous soil that has become saturated or finally by the in-tentional or accidental introduction of impurities, it is necessary toguard against each of these sources. WELLS. To guard against the pollution of wells the location is of impor-tance. Where it is possible the ground should slope away naturallyon all sides, and the pump should be on top of a mound which shouldbe well sodded or cemented all around. Sources of domestic or ofother pollution should be separated from the well by an imperviouslayer below ground to avoid the danger of pollution from seepage. Figure 54 shows how a stratum of rock may protect a well frompollution, even where the drainage is toward the well. 583 The following figure shows how a cesspool may pollute a well,even though the cesspool is at a lower level than the top of the well:. Fig. 55.—Showing pollution of a well by a cesspool situated on a lower level than the top of the : Practical Hygiene; Phila. and X. Y., 1901, p. 324. The ground immediately around the well should be protected fromstray animals by a fence or otherwise. The shaft of the well shouldbe thoroughly tight and for this reason the use of terra cotta tiles ormetal pipe, for the shaft is to be preferred to walling up with bricksand mortar. In any event the space immediately around the shaftproper should be puddled with clay or cement, or, as advised by Koch,have the upper part packed around with sand. The use of open wellsor even the use of chain pumps is not to be recommended, since theyare more or less liable to pollution from the introduction of impuritiesdown the shaft. In all cases the well should be guarded by a tightcoping and cover. A device sometimes resorted to, and which is anadvantage, is to cover over the well with a tight cover and t
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