11-26-2001 Council Packet - Laserfiche WebLink

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OCT-31-01 HED 12:U PM DEPHAVEN CITY HALL FAXNa 16124741274 P. 07 Section 330:00 5. Operating inslnictions shall be posted on every niter system. All valves shall be properly designed, indicating their purpose. 6. Where dissimilar metals arc sued in the construction of the filter, which may set up galvanic currents, then suitable provision shall be made to resist electrolytic corrosion. 7. Filters shall be so designed and installed that they can be readily disassembled and the filter elements removed. pressure Filters. Pressure filter systems utiliang sand or other equally efTeclivc filter media acceptable to the Community Health Board shall be designed and installed to operate at a rate not to cxce^ three (3) galloits per minute, per square fool of Alter area and to back^vash at a minimum rate of twelve (12) gallons per minute per square foot of surface water. 1. Filter tanks shall be fabricated to meet tlic 1956 ASMH Specifications for non-code pressure vessels, wiili the exception that standard type dished and fla led heads may be used. Tanks shall be built for a minimum of fiAy (SO) pounds working pressure and tested at ISO PSI. The filter underdrain shall have an effective distribution of at least 25% of the cross section area of the lank. Tanks shall not be placed underground. 2. Filter tanks shall be supported in a manner to prevent tipping or settling. Filter Media SoeciAcations for Sand Filters. 1. The principal filler medium shall be, as a minimum, a hard, uniformly graded silica maierial with e£fecti\'e particle sizes between 0.4S md 0.55 millimeters in diameter, with uniformity co>cfAcient of 1.75. There shall be no limestone, clay or deleterious matter present. 2. 1 he principal filter medium shall be no less than 20 inches in depth with a Aeeboa.’d of no less than tweU’c (12) inches. 3. Thin* shall be no less than four grades of rock, which shall be clean, non- crushed, rounded, non-porous, non-calcareous material. 4. The total depth of the rock supporting bed shall be no le.<s than 16 inches and each grade shall be two (2) inches or greater in depth. Each layer of rock shall be leveled to prevent intermixing of adjacent grades. 5. Tlie top layer shall vary in size between one-eigliih inch and onc-quaiter inch. The next layer shall vary in size between one-quarter inch and one- half inch. The next layer shall vary in size between one-half inch and three- quarters inch. The bottom layer shall vary in size between one inch and