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. Sediment Assessment Framework Reconnaissance and/or definitive survey SQC exceeded Analyze transport capacity & downstream sensitivity Low transport capacity High transport capacity Not bioavailableBioavailable Initial screening indicates sediment contamination likely SQC not exceeded (Optional) Sediment Management 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 R egional I mpounded S ediment Q uality A ssessment Working with USGS Probabilistic model to estimate: 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* HazardImpoundment PEC exceedances Sig.PXZ-001none Sig.D2Z-008PAH HighUXZ-001Cd, Cu, Pb, Cr Sig.NUZ-001Cu LowHKZ-001none noneLVZ-001Cr LowA2Z-001none LowPTZ-001Pb, PAH, PCB Sig.FTZ-001Cd, Pb Sig.AJZ-001DDE 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 areaPercent impervious area Number of point sources (NPDES, 21E, underground tanks, etc.)Number of point sources (NPDES, 21E, underground tanks, etc.) Additional impoundments are currently being assessed to validate the model

10. Preferred Survey Design Process 1.Establish study objectives, evaluate existing data, etc. 2.Conduct reconnaissance survey 3.Refine study objectives - Choose minimum number of stations that are representative of study area - Choose minimum number of stations that are representative of study area 4.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 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 GravelBar 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) Increasing Concentration PresumedNontoxic PresumedToxic PossiblyToxic PEC TEC

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

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: 1. Assess engineering suitability of dam for staged removal 2. Assess probability, magnitude, impacts of higher, pulsed water flows and sediment loads on downstream geomorphology and ecology 3. (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 wont disrupt remaining ecosystem –Decrease riparian zone, wetlands, bottomlands, etc.

33. Partial Removal of Hot Spots Tasks: 1. Locate hot spots 2. Remove & dispose of sediment In the dry or wet In the dry or wet 3. Demonstrate that remaining sediment is nontoxic 4. Post-remediation monitoring

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

35. Full Removal of All Sediment Tasks: 1. Identify extent of contaminated sediment, in 3D 2. Characterize degree of contamination, for disposal decisions 3. Assess potential disturbance of original channel bed 4. Remove & dispose 5. Post-remediation monitoring

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

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