Columns: A - Amount that would have entered the system if the gates had been left continuously open. B - Number of hours gates were closed. C - Amount shut out. D - Amount deposited in Dalecarlia Reservoir. E - Amount deposited in Georgetown Reservoir. F - Amount deposited in McMillan Park Reservoir. G - Amount entering filtration plant. =========+=======+=======+=======+=======+=====+=====+=====+======== Month. | A | B | C | D | E | F | G | Total. ---------+-------+-------+-------+-------+-----+-----+-----+-------- 1909. ---------+-------+-------+-------+-------+-----+-----+-----+-------- July | 318 | 32.0 | 3 | 0 | 125 | 74 | 116 | 318 August | 146 | 47.0 | 1 | 0 | 78 | 38 | 29 | 146 September| 97 | 57.0 | 7 | 21 | 13 | 38 | 18 | 97 October | 61 | 90.5 | 8 | 7 | 9 | 25 | 12 | 61 November | 50 | 60.0 | 4 | 13 | 5 | 17 | 11 | 50 December | 370 | 99.0 | 126 | 108 | 33 | 59 | 44 | 370 ---------+-------+-------+-------+-------+-----+-----+-----+-------- 1910. ---------+-------+-------+-------+-------+-----+-----+-----+-------- January | 2,410 | 136.0 | 1,109 | 1,020 | 67 | 117 | 97 | 2,410 February | 839 | 117.5 | 481 | 126 | 56 | 75 | 101 | 839 March | 208 | 7.5 | 13 | 43 | 15 | 13 | 124 | 208 April | 321 | 65.0 | 17 | 195 | 43 | 43 | 23 | 321 May | 197 | 84.5 | 58 | 54 | 22 | 24 | 39 | 197 June | 1,505 | 124.0 | 786 | 535 | 49 | 88 | 47 | 1,505 ---------+-------+-------+-------+-------+-----+-----+-----+-------- Total | 6,522 | 920.0 | 2,613 | 2,122 | 515 | 611 | 661 | 6,522 =========+=======+=======+=======+=======+=====+=====+=====+======== In order to relieve the situation at such times, the expedient of raking was tried. This was first attempted with the filters filled with water; the effluent was first shut off in order to prevent a downward flow of water, and the filter was then raked or harrowed from boats. This method was not satisfactory, however, as the work was neither as uniform nor as thorough as necessary. Later, the filters were drained to the necessary depth, and the surface of the sand was thoroughly stirred with iron garden rakes. The filters were then filled with filtered water through the under-drains and put in service. This latter method proved so satisfactory that it has been resorted to at all times when the work was at all pressing. When the runs were of short duration, and the depth to which the mud had penetrated the filter sand was slight, a raking seemed to be nearly as effective in restoring the filter capacity as a scraping; it could be done in 8 hours by 3 laborers, and there seemed to be no ill effects from lowered efficiency.