DILUTION is the method of sewage disposal most commonly employed outside of England. As usually practiced it can scarcely be said to be a system of disposal. since the sewage is dis charged into the nearest body of water with lit-tle regard to consequences. In :1/41assachu setts, New York. New Jersey, and Ohio, all new disposal schemes must be approved by a cen tral body, which is the State Board of Health in all States but New• Jersey, and the State Sewage Commission in that commonwealth. In England all new disposal works involving loans must be approved by the Local Government Board. The stringent legislation against water pollu tion renders the employment of dilntion alone a less common practice there than in America. The first principle in disposal by dilution, indeed, in all sewage disposal, is never to endanger a public water supply; the second is not so to over load the stream or other body of water as to create a nuisance.
The best example in the States of disposal by dilution was furnished. first by the city of Boston, and afterwardt by Boston and other near-by towns united to form the Metro politan Sewerage District. The various communi ties in the district have their individual sewer age systems. These all discharge into one or
the other of two large trunk or outlet sewers, leading to carefully selected points of discharge. At one of the outlets, located at Moon Island, the sewage is stored in reservoirs and discharged at ebb-tide. At the other, or Deer Island outlet, it is discharged continuously. Pumping is nec essary for each outlet sewer. A third outlet sewer, which will also discharge continuously in Boston Harbor, was under way in 1901. The other two were built. in 1884 and 1895. respec tively. At Milwaukee and Chicago huge pump ing works and tunnels were built several years ago to pump lake water into rivers badly pol luted by sewage, mitigating the nuisance by The Chicago flushing tunnel was put in use in 1880, and the one at Milwaukee in 1888. The Chicago Drainage Canal (q.v.) is by far the most notable work ever undertaken for the disposal of sewage by dilution. The ca pacity of the canal was based on a flow of 1 cubic foot of water per minute to each five in habitants, some years hence, or 2160 gallons of diluted sewage per day for each future inhabi tant:.