Comparison of the Suspended-Sediment Splitting Capabilities of the Churn and Cone Splitters

To: "A  - Division Chief and Staff",
        "B  - Branch Chiefs and Offices",
        "DC - All District Chiefs",
        "CD - All Data Chiefs",,
        "William M Alley, Chief, OGW, Reston, VA" ,
        "Mary J Amos, Secretary (OA), Reston, VA" ,
        "Velvie E Stockdale, Office Automation Assistant, Reston, VA" ,
        "Thomas E Reilly, Hydrologist, Reston, VA" ,
        "Hayes F Grubb, RASA Coordinator, OGW, Reston, VA" ,
        "Kenneth J Hollett, Asst. Chief, OGW, Reston, VA" ,
        "Jilann O Brunett, Data Coordinator, Reston, VA" ,
        "Arlen W Harbaugh, Hydrologist, Reston, VA" ,
        "James W LaBaugh, Hydrologist, Reston, VA" ,
        "John R Gray, Hydrologist, Reston, VA" ,
        "Harvey E Jobson, Hydrologist, Reston, VA" ,
        "L. Jane Rose, Secretary, Reston, VA" ,
        "Annette L Ledford, Clerk Typist, Reston, VA" ,
        "Harry F Lins, Hydrologist, Reston, VA" ,
        "Robert R Mason Jr., Hydrologist(Engr), Reston, VA" ,
        "Alison Barker, Volunteer Hydrologist, Reston, VA" ,
        "Thomas H Yorke Jr., Chief, OSW, Reston, VA" ,
        "Ernest F Hubbard, Assistant Chief, OSW, Reston, VA" ,
        "William H Kirby, Hydrologist (Engr), Reston, VA" ,

Date: Wed, 14 May 1997 09:51:50 -0400
From: "David A Rickert, Chief, OWQ, Reston, VA" 

In Reply Refer To:
Mail Stop 412                                            May 5, 1997


Subject:  Comparison of the Suspended-Sediment Splitting Capabilities of 
          the Churn and Cone Splitters

The Office of Water Quality (OWQ), with advice from the Office of Surface 
Water (OSW) and the National Water Quality Assessment (NAWQA) Program, 
has conducted a series of laboratory tests on the suspended-sediment 
splitting capabilities of the churn and cone devices. The tests were 
conducted on prepared samples using monomineralic silica sands of various 
controlled concentrations and mean particle sizes in distilled water. The 
detailed results of the tests are available via anonymous ftp in a 
document entitled "Selected Laboratory Tests of the Whole-Water Sample 
Splitting Capabilities of the 14-Liter Churn Splitter and Teflon Cone 
Splitter" by Art Horowitz and others.

login: anonymous
password: userid
cd pub/owq/

The major findings of the sample-splitting tests and resultant Division 
policies are:

1.      At suspended-sediment concentrations <1,000 mg/l and mean particle 
size <250 um, the two devices provide sufficiently comparable and 
acceptable sample-splitting capabilities for whole-water samples (based 
on bias and precision) to enable interchangeable use. A 
suspended-sediment concentration of 1,000 mg/L is equivalent to the 93rd 
percentile of average suspended-sediment concentrations at 428 U.S. 
Geological Survey (USGS) river-monitoring stations for the period 
1980-89. Also, for the 1,000 mg/L limit, historical data indicate that 
the concentration of sand grains >250 um is likely to be small.

2.      At a suspended-sediment concentration of 10,000 mg/L (the next tested 
level above 1,000 mg/L), the churn exhibits unacceptable bias and 
precision. Thus, the upper suspended-sediment concentration limit for 
processing whole-water samples with the churn splitter is set at <1,000 

3.      At a suspended-sediment concentration of 10,000 mg/L, the cone 
splitter still splits samples with acceptable bias and precision. 
Performance of the cone is unacceptable at 100,000 mg/L (the next tested 
level). Thus, the upper limit for processing whole-water samples with the 
cone splitter is set at <10,000 mg/L. This is equivalent to greater than 
the 99th percentile of the average suspended-sediment concentrations at 
the 428 USGS river-monitoring stations. 

Based on these results, Division personnel can use either device for 
processing whole-water samples with suspended-sediment concentrations 
<1,000 mg/L, and can use the cone splitter for samples with 
suspended-sediment concentrations of <10,000 mg/L.

The offices thank Art Horowitz, Tim Hayes, John Gray, Paul Capel, and 
Judy Scholz for their major roles in designing, implementing, and 
interpreting the splitting device tests. We also thank the 
Instrumentation Committee for financially supporting this important 

                        David A. Rickert
                        Chief, Office of Water Quality

This memorandum supersedes OWQ Technical Memorandums 76.24-T and 77.01, 
and modifies 80.17.

Key words: churn, cone, concentrations, sediment

Distribution:     A, B, DC, CD
                  District Water-Quality Specialists
                  Office of Ground Water Staff
                  Office of Surface Water Staff
                  OWQ Staff
                  Regional Water Quality Specialists