Sediment Laboratory Procedures

In Reply Refer To:                                       May 14, 1996
Mail Stop 415


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


WRD Distribution: A, B


ATTACHMENT                                              15 April 1996


Subject: Sediment size Data Determined by use of the Sedigraph


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.


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.



Chairman, Sedimentation Project Technical Committee
USDA Forest Service