Filter Gravel and Sand

Issue 26 and Volume 54.

Filter Gravel and Sand The filter medium for the filters being constructed for the new Colon waterworks will consist of layers of selected Chagres River gravel and Punta Chamé sand. The gravel will be placed at the bottom of the filter, in three layers. For the first, or bottom, layer the gravel will be laid 10 inches deep and in size will be that which can be passed through a 1 1/4-inch screen and held on a 5/8-inch screen; for the second layer, seven inches in depth, the gravel passing through the 5/8-inch screen and held on a 3/8-inch screen; for the top layer, that which can be passed through a 3/8-inch mesh and held on a 3-16-inch screen. On top of this last layer of gravel will be placed 30 inches of washed sand, separated in such a manner as to give a mean effective size, approximately .35 to…

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