PROGRAMS AND PLANS--Policy on suspended sediment filers--The asbestos mat shall not be used. The Whatman 934 AH shall be used. In Reply Refer To: December 24, 1991 Mail Stop 415 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM 92.05 Subject: PROGRAMS AND PLANS--Policy on suspended sediment filers--The asbestos mat shall not be used. The Whatman 934 AH shall be used. The prescribed methods for determining the concentration of sediment samples by U.S. Geological Survey (USGS) sediment laboratories are those described in Book 5, chapter C1 of the series "Techniques of Water-Resources Investigations of the United States Geological Survey." Sediment concentration can be determined by either the filtration or evaporation method. The filtration equipment includes a crucible with a perforated bottom, a crucible filter, and vacuum system. Guy (1969) recommended use of either the Whatman #934-AH glass filter or a glass-fiber filter disk covered by an asbestos mat. A crucible filter is not required for the evaporation method. The use of asbestos is no longer permitted in a USGS sediment laboratory. Therefore, only the Whatman 934 AH filter should be used when sediment concentrations are determined by the filtration method. If a laboratory chooses to use a filter other than the Whatman 934 AH, the laboratory must provide documentation that the filters are equivalent. Beginning with the 1992 water-year annual report, laboratories must obtain approval from the Office of Surface Water before publishing concentration data collected using filters other than the Whatman 934 AH. Reference Guy, Harold P., 1969, Laboratory theory and methods for sediment analysis: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. C1, 58 p. Charles W. Boning Chief, Office of Surface Water WRD Distribution: A, B, PO, FO