Sediment Laboratory Procedures In Reply Refer To: May 14, 1996 Mail Stop 415 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 96.07 Subject: Sediment Laboratory Procedures Attached is a memorandum from the Federal Interagency Sedimentation Project (FISP) approving the use of the Sedigraph for determining sediment fall diameter. The Office of Surface Water (OSW) approved the use of sedigraph procedures in OSW Technical Memorandum No. 93.11. The OSW welcomes the endorsement of the FISP which means that all Federal Agencies should accept the results from this instrument. The use of the sedigraph for determining sediment fall diameter provides the potential for lowering our analytical costs. OSW recommends its use consistent with the documentation required in the attached memorandum. Thomas H. Yorke Chief, Office of Surface Water Attachment WRD Distribution: A, B ___________________________________________________________________ ATTACHMENT 15 April 1996 FEDERAL INTERAGENCY SEDIMENTATION PROJECT MEMORANDUM 96.01 Subject: Sediment size Data Determined by use of the Sedigraph BACKGROUND The Federal Agencies have traditionally recommended sediment fall diameter be determined by the V A tube, pipet, B W tube, or hydrometer. The Sedigraph is a much faster and cheaper method for size analysis and the Sediment Action Committee of the Water Resources Division (WRD) of the USGS has recommended that it be approved as an alternative method of analysis for fall diameter. A comparison of the pipet and Sedigraph has been documented in a memorandum from the Branch of Quality Assurance (WRD) to the Office of Surface Water (WRD) dated December 14, 1992 and in the Federal Interagency Report KK "Evaluation of Pipet and X-ray Procedures for Determining Particle-size Distributions for Sediment" by Rollin Hotchkiss, 1994. For sizes in the silt-clay range, there is a general tendency for the Sedigraph to indicate about 5 to 10 percent more material is finer than a given size than indicated by the pipet method. For a given field site, comparison tests indicate that the relationship between sedigraph and pipet methods can be established by performing duplicate analyses. For this reason it is important to identify the method of analysis when storing the size data and to perform duplicate sample analyses to document the bias at a given site. Approval: The Federal Interagency Sedimentation Project (FISP) Technical Committee now approves the use of the Sedigraph method for the analysis of fall diameter. Data obtained by use of the Sedigraph should reference the method of analysis and anyone who chooses to use the Sedigraph method should perform duplicate sample analysis on at least 10 percent of the samples until the relationship between the Sedigraph and pipet (or other standard method) results can be quantified for this site. Sincerely, /signed/ LARRY J. SCHMIDT Chairman, Sedimentation Project Technical Committee USDA Forest Service