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A COMPARISON OF TSS AND SSC DATA

A COMPARISON OF TSS AND SSC DATA. Subtitled What are TSS and SSC data, and who cares?. Sediment Data-Collection Techniques USGS National Training Center Course SW1091 Toutle, Castle Rock, and Vancouver, WA March 24-28, 2014 John R. Gray (jrgray@usgs.gov)

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A COMPARISON OF TSS AND SSC DATA

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  1. A COMPARISON OF TSS AND SSC DATA SubtitledWhat are TSS and SSC data, and who cares? • Sediment Data-Collection Techniques • USGS National Training Center Course SW1091 • Toutle, Castle Rock, and Vancouver, WA • March 24-28, 2014 • John R. Gray (jrgray@usgs.gov) • National Sediment Specialist(retired) • USGS Office of Surface Water

  2. TO BE COVERED • Problem Identification. • What are TSS data? SSC data? • Research Results. • Ramifications of TSS data use. • Who cares? Project funded by the USGS Offices of Surface Water, and Water Quality

  3. Background Information • USEPA: Fluvial Sediment andsorbed constituents are the Most Widespread Impairment of the Nation’s Rivers http://iaspub.epa.gov/waters10/attains_nation_cy.control?p_report_type=T#tmdl_by_pollutant • TSS Data are Often the Only Source of Sediment Data Available: 29 of 31 States sediment metric is (was?) TSS (per questionnaire, Gray & Glysson 2003). http://water.usgs.gov/osw/techniques/TSS/pruitt.pdf

  4. I. Societal Relevance of Sediment National Perspective Accessed January 26, 2012 Remove the sediment…“End” 9 of top 10 impairments. ? ?

  5. Societal Relevance of Sediment – Cost $Billions • $25-$65 billion: Annual physical, chemical, and biological damages sediment damages in N. America (SCIENCE, 1995, by Pimental et al., adjusted for inflation); most damages in U.S. • $2.5 billion: Sediment damages and remediation, reservoir-storage facilities (per ARS & USGS). • $0.8-$1.1 billion: Created Louisiana’s coastal wetlands annual costs (per COE estimates). • $1.1 billion: Dredging costs in support of about 490 million tonnes of commerce on the Mississippi and Ohio Rivers in 2007 (per COE estimates). • $1.5-$2.5 billion: Cost for 3-5 overflow diversions to build wetlands in Louisiana; up to 20 could be constructed (per COE estimate). • $0.7 billion: Missouri River Recovery Program, Environmental Management Program, low-flow water-supply infrastructure upgrades (per combined COE estimates). • $Unknown, but Undoubtedly Substantial: Gulf Hypoxia, sediment management from dam removal, sediment-quality impairments, etc. …we ran out of room... 

  6. June 1998

  7. Total Suspended Solids (TSS) versus Suspended-Sediment Concentration (SSC) • The TSS analysis entails withdrawal of an aliquot of the original sample for subsequent analysis. (Standard Methods 2540-D) • The SSC analysis uses the entire water-sediment mixture. (ASTM D-3977)

  8. PROBLEM • TSS data are solid-phase metrics for 29 of 31 States responding to a 2002 questionnaire (Pruitt, in Gray and Glysson, 2003). • The TSS method tends to provide: • Negatively biased, and • More variant data than that for the demonstrably reliable SSC method(when used on samples collected from open-channel flow*). *Important caveat

  9. TSS ANALYTICAL PROCEDURE • Originated for wastewater analyses (Δ in 1976). • In practice, techniques and equipment vary. • Cannot determine particle-size distributions. • Fast turnaround, lower cost? (some say NO) • Uses aliquot of original sample.

  10. SSC ANALYTICAL PROCEDURE • ASTM Standard Procedure based on Federal Interagency Sedimentation Project research, 1940 ++ (along with some home cookin’…I can explain) • Can determine particle-size distributions • Slower turnaround, higher cost? Some say NO. • Measures all sediment and mass of water-sediment mixture using prescribed equipment.

  11. National Sediment Laboratory Quality Assurance Programhttp://sedserv.cr.usgs.gov/ • Training in lab procedures • On-site lab evaluations • Single-blind program • Double-blind program • National quality-control data evaluation • Follow-up evaluations • Documentation of QC plans and procedures

  12. ORGINAL DATA SET • 14,466 pairs of samples from 48 States and Puerto Rico • 53 QC samples from USGS Sediment Lab Quality Assurance Program • Most SSC Samples were Analyzed in USGS-Approved Laboratories using ASTM Standard D-3977 • TSS Analyses were Performed by USGS, State, and Contractor Laboratories

  13. TSS SSC

  14. !Note reversal of axes!

  15. August 1998

  16. SSC TSS

  17. Summary of years of record and errors in the estimations of suspended-sediment loads (all errors are in percent)

  18. NATIONAL-SCALE IMPLICATIONS • Difference between TSS and SSC analytical results of paired samples can be substantial; estimates of instantaneous sediment discharges can be orders of magnitude in error. • No simple, straight-forward way to adjust TSS data to estimate SSC without paired data. • TSS-generated load-reliability suspect.

  19. NATIONAL-SCALE IMPLICATIONS (cont) • TSS data are “fundamentally unreliable.” • USGS guidelines ban routine TSS collection • Legal ramifications: Can one prove that TSS results are reliable? • Given the big picture, are production of TSS data in lieu of SSC data justifiable? • Our Conclusion…Quality of Nation’s sediment data would be greatly enhanced all produced by the SSC Method.

  20. INTERNAL USGS GUIDANCEOSW/OWQ Technical Memo 2001.03 • USGS must collect SSC data. • If one must collect TSS sample (compliance, continuity), must also collect duplicate SSC sample. • Collect TSS data alone only if you have proven that they represent the true concentration of solid-phase material. http://water.usgs.gov/admin/memo/SW/sw01.03.html

  21. USGS WRI 00-4191 & OTHER TSS-FOCUSED PAPERSby Gray, Glysson, Conge/Turcios, and Schwarz http://www.usgs.gov/osw/techniques/sediment/ • ADJUSTMENT OF TOTAL SUSPENDED SOLIDS DATA FOR USE IN SEDIMENT STUDIES • COMPARABILITY OF TOTAL SUSPENDED SOLIDS AND SUSPENDED- SEDIMENT DATA • A COMPARISON OF LOAD ESTIMATES USING TSS AND SSC DATA SUSPENDED SOLIDS AND

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