Distribution of "Evaluation of pipet and x-ray procedures for determining particle-size distributions of sediment," Federal Interagency Project Report KK 



In Reply Refer To:                                       June 19, 1995
Mail Stop 415


OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 95.06

Subject:  Distribution of "Evaluation of pipet and x-ray procedures 
          for determining particle-size distributions of sediment," 
          Federal Interagency Project Report KK 

Attached is a copy of the subject report which served as part of the 
basis for the Office of Surface Water (OSW) decision to approve the 
Sedigraph as a method of size analysis for fall diameter in OSW Techni
cal Memorandum No. 93.11. The Sedigraph is an x-ray based sediment size 
analysis instrument for use in the silt-clay size range. It provides 
more consistent size analysis data than the pipet, especially for the 
small size classes, and the analyses can be performed much more quickly 
than by the pipet method or bottom withdrawal methods. Two Water 
Resources Division sediment laboratories, Iowa and Washington, have 
Sedigraph instruments.

The OSW encourages the use of the Sedigraph for size analysis and 
believes it will become the future standard method. For sizes in the 
silt-clay range, there is a general tendency for the Sedigraph to indi
cate that about 5 to 10 percent more material is finer than a given size 
indicated by the pipet method. For a given field site, comparison test 
indicates that the relationship between Sedigraph and pipet methods can 
be established by performing duplicate analyses. Each District that 
chooses to switch from one size analysis method to another should per
form duplicate sample analysis on at least 10 percent of the samples 
until the relationship between the Sedigraph and the former analysis 
method can be quantified. For new stations, the difference need not be 
established so the 10 percent duplicate analyses are not required.


                                Ernest F. Hubbard
                                Acting Chief, Office of Surface Water

Attachment

WRD Distribution: FO