The sand of the filter was as capable of filtering the full supply of water as it ever had been, and the efficiency was as good; but the underdrains were no longer able to collect the filtered water and deliver it. As the filtering area was ample for the supply, it was desired to avoid construction of additional filtering area. The underdrains were dug up and cleaned during the periods when the filter was drained. As the filter is all in one bed, the times when the filter could be allowed to remain drained, and when the work could proceed, were limited. Great care was taken to leave the work in good condition, and free from passages, at the end of each day’s work, but the numbers of bacteria in the effluent nevertheless increased somewhat. Some weeks afterward the number of cases of typhoid fever in the city increased. The numbers did not become as high as they had been prior to the introduction of filtered water, but they were much higher than they had been since that time, and they pointed strongly to the disturbance of the underdrains as the cause of the increase. The numbers of bacteria in the applied water and in the effluent from the Lawrence filter by months, from the time the filter was put in operation, compiled from the reports of the State Board of Health, as far as available, are as follows: BACTERIA IN WATER APPLIED TO AND EFFLUENT FROM LAWRENCE FILTER. RAW WATER. ----------------+--------+--------+--------+--------+--------+-------- | 1893. | 1894. | 1895. | 1896. | 1897. | 1898. ----------------+--------+--------+--------+--------+--------+-------- January | | 7,700 | 18,700 | 7,500 | 13,314 | 6,519 February | | 7,600 | 15,040 | 12,600 | 13,113 | 4,653 March | | 6,500 | 20,770 | 5,900 | 12,055 | 3,748 April | | 11,200 | 8,420 | 3,800 | 6,904 | 2,320 | | | | | | May | | 6,000 | 7,000 | 9,600 | 4,625 | 2,050 June | | 8,300 | 9,000 | 6,400 | 4,650 | 6,775 July | | 2,400 | 10,000 | 3,900 | 6,240 | 2,840 August | | 3,100 | 5,000 | 2,700 | 10,700 | 8,575 | | | | | | September | 57,500 | 6,500 | 5,000 | 12,300 | 27,300 | 6,100 October | 22,200 | 25,300 | 19,000 | 5,300 | 13,200 | 5,120 November | 10,800 | 16,600 | 8,700 | 5,600 | 6,644 | 4,310 December | 8,100 | 23,800 | 6,700 | 9,695 | 5,581 | 5,200 +--------+--------+--------+--------+--------+-------- Average | 24,650 | 10,417 | 11,111 | 7,108 | 10,360 | 4,850 EFFLUENT.