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