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Sediment Quality Assessment and Management Framework for Dam Removal Projects

Sediment Quality Assessment and Management Framework for Dam Removal Projects. Brian Graber & Karen Pelto Riverways Program, Massachusetts Fish & Game Joseph Rathbun Water Bureau, Michigan Dept. of Environmental Quality James Turek NOAA Restoration Center Laura Wildman American Rivers.

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Sediment Quality Assessment and Management Framework for Dam Removal Projects

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  1. Sediment Quality Assessment and Management Framework for Dam Removal Projects Brian Graber & Karen Pelto Riverways Program, Massachusetts Fish & Game Joseph Rathbun Water Bureau, Michigan Dept. of Environmental Quality James Turek NOAA Restoration Center Laura Wildman American Rivers

  2. Basic Concepts: Reservoirs are Sediment Traps • Many trap 95 % of the sediment that enters them from upstream • Large sediment particles typically form deltas at upstream end • Small sediment particles typically transported farther into reservoir • Many contaminants typically bind to small particles

  3. Basic Concepts: Issues with Contaminated Sediment • Direct toxicity to organisms • Acute • Chronic • Bioaccumulation in organisms • Alter benthic community • Contaminate overlying water • Affect disposal of dredged material

  4. Initial screening indicates sediment contamination likely Reconnaissance and/or definitive survey SQC not exceeded SQC exceeded Analyze transport capacity & downstream sensitivity Not bioavailable Bioavailable Low transport capacity High transport capacity (Optional) Sediment Management Framework Sediment Assessment Framework

  5. Initial Landscape-Level Screening • Screen impoundment sediment quality based on landscape-level GIS information • Screening can flag an impoundment, watershed, or region for likely contaminants

  6. Predictive Model - RISQA • Regional • Impounded • Sediment • Quality • Assessment • Working with USGS • Probabilistic model to estimate: • Sediment quantity • Trace elements • Organic contaminants

  7. Developing and Validating RISQA • Compile existing data on sediment quality and quantity in impoundments • Field assess volume and quality of sediment in selected impoundments • Develop and validate a GIS-based model for predicting sediment quantity and quality based on basin characteristics

  8. *preliminary data* HazardImpoundmentPEC exceedances Sig. PXZ-001 none Sig. D2Z-008 PAH High UXZ-001 Cd, Cu, Pb, Cr Sig. NUZ-001 Cu Low HKZ-001 none none LVZ-001 Cr Low A2Z-001 none Low PTZ-001 Pb, PAH, PCB Sig. FTZ-001 Cd, Pb Sig. AJZ-001 DDE Combine dam hazard classification with contaminant assessment?

  9. Preliminary Modeling Results Preliminary regression analyses indicate that sediment contamination variability may be best explained by: • Percent impervious area • Number of point sources (NPDES, 21E, underground tanks, etc.) Additional impoundments are currently being assessed to validate the model

  10. Preferred Survey Design Process • Establish study objectives, evaluate existing data, etc. • Conduct reconnaissancesurvey • Refine study objectives - Choose minimum number of stations that are representative of study area • Conduct definitive survey

  11. Reconnaissance Survey • Objectives • Sampling access • Sample collectability • Qualitatively assess nature and extent of deposits • Quantitatively collect a small number of (silt) sediment quality samples • Equipment • Probing rod or tube • Small grab or core sampler • GPS

  12. Reconn. Survey – Mud Music ♫ Use hollow metal tube to identify surface sediment type: • Rock = bounce & clang • Clay = bounce & silent • Gravel = crunch • Silt = silent, penetration • Sand = silent, no penetration Reconn. sample from silt portion

  13. Moving from Reconn Survey to Definitive Survey Combine: • Reconn survey info • Regulatory guidelines/requirements • State specific • Watershed screening information (due diligence) • Best professional judgment To determine if additional assessment is needed ex. headwaters; run-of-river; gravel

  14. Definitive Survey • Objective • Quantitatively establish magnitude and extent of contamination • Equipment • Grab or core samplers • GPS Largely the same as reconn…

  15. Definitive Survey Sampling Design • How many samples will be collected • Where samples will be collected • How samples will be collected

  16. Sampling Design – How Many? • Most subjective part of survey design • Best Professional Judgment and regulatory guidelines • Minimum 50-ft diameter “hot spots”? • $$$$ (affects sampling resolution) • Elipgrid-PC software • Computes probability of locating “hot spots” • Based on total area, grid spacing, and potential hot spot size, shape, orientation • Can use to determine number of samples

  17. Sampling Design – Where? • Objective of the study • Cost-effectiveness • Use Elipgrid-PC • Sediment patterns

  18. Simple Random Sampling Dam

  19. Systematic Grid Sampling Dam

  20. Subjective Sampling Dam Outfall

  21. Stratified Random Sampling Dam Gravel Bar Silt Bar

  22. Sample Collection: Grab Sampling • More “recent” sediments (?) • Mixed, mobile surface layer • (grab 2 – 24 L) • “Biologically active” zone • Upper 10 cm or so Ponar Sampler

  23. Sample Collection: Core Sampling • Recent to older sediment • Stratified, less mobile deposits • important if mobilized during removal • Hand corers • Cores = a few feet long, 2” diameter • Shallow water • Gravity corers, piston corers, etc. • Cores < 5’ long • Deep water • Vibrocorers • Cores = up to 20’ long, 4” diameter • Deep water (> 1,000’) • Less disruption of sediment column • Challenges in gravel, clay

  24. Sample Analysis - Chemical • Often only testing done – least expensive • Methods well-established • Common analytes = metals, PCBs, PAHs

  25. Sediment Analysis – Toxicity • Done less often than chemical testing • greater expense • requires larger sample • Why do toxicity testing? • Integrates effects • Uses important food chain organisms • Direct proof of effects No effect = no pollution (?) Midge larvae Amphipod

  26. Data Interpretation:Sediment Quality Criteria Uses: • Evaluate sediment quality • Establish cleanup objectives • Assess suitability for disposal • Assess suitability for natural erosion & deposition Agree to at start of project

  27. Chemical Concentration SQC • Tied to biological effects • Cu > X ppm = mortality in mayflies • Usually tied to toxicity rather than bioaccumulation or changes in community structure or human health • More often guidelines than regulations • vary state to state

  28. Database Chemical SQC PEC = probable effects concentration (above which effects are probable) TEC = threshold effects concentration (below which effects rarely observed) Presumed Toxic PEC Possibly Toxic Increasing Concentration TEC Presumed Nontoxic

  29. Low transport capacity and/or high d/s sensitivity High transport capacity and/or low d/s sensitivity Not bioavailable Bioavailable (Optional) Natural erosion & deposition Staged dam removal Cap or isolate Partial sediment removal Full sediment removal Sediment Management Framework

  30. Complete Dam Removal & Natural Erosion & Deposition Issue: demonstrate transport & deposition will not: • Cause long-term adverse physical habitat changes downstream or upstream • Fill pools, bury riffles, etc. downstream • Upstream channel incision • Increase bioavailability (exposure/mobilization) of contaminants

  31. Staged Dam Removal & Natural Erosion & Deposition Issues: • Assess engineering suitability of dam for staged removal • Assess probability, magnitude, impacts of higher, “pulsed” water flows and sediment loads on downstream geomorphology and ecology • (Plus issues for complete dam removal)

  32. On-Site Isolation or Capping Issue: demonstrate that: • Capping will reduce contaminant availability to aquatic and terrestrial ecosystems, and humans • Capping won’t disrupt remaining ecosystem • Decrease riparian zone, wetlands, bottomlands, etc.

  33. Partial Removal of Hot Spots Tasks: • Locate hot spots • Remove & dispose of sediment • In the “dry” or “wet” • Demonstrate that remaining sediment is nontoxic • Post-remediation monitoring

  34. Sediment Removal – “Wet” & “Dry” (HRC, Inc.) (ECT, Inc.)

  35. Full Removal of All Sediment Tasks: • Identify extent of contaminated sediment, in3D • Characterize degree of contamination, for disposal decisions • Assess potential disturbance of original channel bed • Remove & dispose • Post-remediation monitoring

  36. Initial screening indicates sediment contamination likely Reconnaissance and/or definitive survey SQC not exceeded SQC exceeded Analyze transport capacity & downstream sensitivity Not bioavailable Bioavailable Low transport capacity High transport capacity (Optional) Sediment Management Framework Sediment Quality and Management Options

  37. Contaminated Sediment = Run Away? • Dams as a long-term sediment and contaminant management plan? • Reservoir = contaminant “time bomb”

  38. For more information: • Brian Graber, brian.graber@state.ma.us • Joseph Rathbun, rathbunj@michigan.gov

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