SEDIMENT ASSESSMENT & SEDIMENT ASSESSMENT & MANAGEMENT FOR DAM MANAGEMENT FOR DAM

REMOVAL PROJECTSREMOVAL PROJECTS

Joe RathbunJoe RathbunMichigan Dept. of Environmental QualityMichigan Dept. of Environmental Quality

Water BureauWater Bureau517-373-8868517-373-8868

rathbunj@michigan.govrathbunj@michigan.gov

OutlineOutlineBasic ConceptsBasic Concepts

Sample CollectionSample Collection– Survey designSurvey design– Grab and core samplingGrab and core sampling

Effects AssessmentEffects Assessment– ToxicityToxicity– BioaccumulationBioaccumulation– Sediment quality criteriaSediment quality criteria

Sediment Management OptionsSediment Management Options

Sediment Assessment Framework

Reconnaissance and/or definitive survey

SQC exceeded

Analyze transport capacity & downstream sensitivity

Low transport capacity

High transport capacity

Not bioavailable Bioavailable

Initial screening indicates sediment contamination likely

SQC not exceeded

(Optional)

Sediment ManagementFramework

Sediment Management Framework

Fullremoval

Partialremoval

Cap or isolate

Natural erosion& deposition

Stagedremoval

Low transport capacity and/or

high d/s sensitivity

High transport capacity and/or

low d/s sensitivity

Not bioavailable Bioavailable

(Optional)

Basic Concepts: Basic Concepts: Sediment TransportSediment Transport

Rivers do 2 things very wellRivers do 2 things very well

–Move Move waterwater

–Move Move sedimentsediment

Most sediment transported during Most sediment transported during floodsfloods

Basic Concepts: Reservoirs are Basic Concepts: Reservoirs are Sediment TrapsSediment Traps

Many trap Many trap 95 %95 % of the sediment of the sediment that enters them from upstreamthat enters them from upstream

LargeLarge sediment particles form sediment particles form deltas at upstream enddeltas at upstream end

SmallSmall sediment particles sediment particles transported farther into reservoirtransported farther into reservoir

Basic Concepts: Issues with Basic Concepts: Issues with Contaminated SedimentsContaminated Sediments

Direct Direct toxicitytoxicity to organisms to organisms– AcuteAcute– ChronicChronic

BioaccumulationBioaccumulation in organisms in organisms

Alter Alter benthic communitybenthic community

Contaminate overlying Contaminate overlying waterwater

Affect disposal of Affect disposal of dredged materialdredged material

Basic Concepts: Basic Concepts: Contaminant DistributionContaminant Distribution

↓↓ grain size = grain size = ↑↑ contaminant contaminant concentrationconcentration– Silt = Silt = ↑↑ TOC, for organics (& metals) TOC, for organics (& metals)

– Clay = Clay = ↑↑ binding sites for metals binding sites for metals

Grain size distribution “predictable”Grain size distribution “predictable”– Upper impoundment = large particlesUpper impoundment = large particles– Lower impoundment = finesLower impoundment = fines

Organic Contaminants:Organic Contaminants:Sediment vs. Water Sediment vs. Water

ConcentrationsConcentrations

Depending on contaminant Depending on contaminant polarity, solubility, etc. …polarity, solubility, etc. …

Sediment > water by factor of Sediment > water by factor of 1,0001,000 to to 10,000,00010,000,000

Almost always have to sample…Almost always have to sample…

Because of unexpected historic Because of unexpected historic contaminant sources:contaminant sources:

Brick factories Brick factories = Cd, Pb, Ni, Ba, Se, Co= Cd, Pb, Ni, Ba, Se, Co

Orchards & tobacco fieldsOrchards & tobacco fields = As, Hg = As, Hg

TanneriesTanneries = Cd, Cr, As, Hg = Cd, Cr, As, Hg

Coal gasification plantsCoal gasification plants = PAHs, metals = PAHs, metals

Glass factoriesGlass factories = As, other metals = As, other metals

CemeteriesCemeteries = Pb, As, Hg = Pb, As, Hg

Dye manufacturersDye manufacturers = metals = metals

Sampling Survey DesignSampling Survey Design

First step in samplingFirst step in sampling

Extremely important to data qualityExtremely important to data quality

Sediment quality data are easy to Sediment quality data are easy to collect but difficult to interpret unless collect but difficult to interpret unless obtained using a well-designed surveyobtained using a well-designed survey

Sampling Survey Design:Sampling Survey Design:Field vs. Lab HeterogeneityField vs. Lab Heterogeneity

Sources of data variabilitySources of data variability– In-situIn-situ heterogeneity, in the field heterogeneity, in the field– CollectionCollection biases & inaccuracies biases & inaccuracies– LabLab biases & inaccuracies biases & inaccuracies

PCBs in soil (EPA, 1992):PCBs in soil (EPA, 1992):– Lab = < 1 % of data variabilityLab = < 1 % of data variability– Location of sample = 92 % of data Location of sample = 92 % of data

variabilityvariability

Simplest Case:Simplest Case:Small Dam…Rural Area…No MoneySmall Dam…Rural Area…No Money

Minimum data required:Minimum data required:

Demonstrate Demonstrate lack of upstream sourceslack of upstream sources

Find siltFind silt deposits & establish thickness deposits & establish thickness

Collect Collect minimal number of samplesminimal number of samples– ≥ ≥ 1 from each silt deposit, & combine?1 from each silt deposit, & combine?

Analyze for Analyze for organics & metalsorganics & metals

Compare to Compare to sediment quality criteriasediment quality criteria

Sample benthos?Sample benthos?

Preferred Survey Design ProcessPreferred Survey Design Process

1.1. Establish Establish study objectivesstudy objectives, evaluate , evaluate existing data, etc.existing data, etc.

2.2. Conduct Conduct reconnaissancereconnaissance surveysurvey

3.3. Refine study objectivesRefine study objectives - Choose minimum number of stations that - Choose minimum number of stations that

are representative of study areaare representative of study area

4.4. Conduct Conduct definitive surveydefinitive survey

Reconnaissance SurveyReconnaissance Survey

ObjectivesObjectives– Sampling accessSampling access– Sample collectabilitySample collectability– Qualitatively assess nature and extent of Qualitatively assess nature and extent of

contaminated depositscontaminated deposits

EquipmentEquipment– Probing rodProbing rod– Small grab or core samplerSmall grab or core sampler– Equipment for hydrographic surveyEquipment for hydrographic survey– GPSGPS

Reconn. Survey – Mud Music Reconn. Survey – Mud Music ♫♫

Use Use hollow metal tubehollow metal tube to identify to identify sediment type:sediment type:

RockRock = bounce & clang = bounce & clang

ClayClay = bounce & silent = bounce & silent

GravelGravel = crunch = crunch

SiltSilt = silent, penetration = silent, penetration

SandSand = silent, no penetration = silent, no penetration

Definitive SurveyDefinitive Survey

ObjectiveObjective

– Quantitatively Quantitatively establish magnitude establish magnitude and extent of contaminationand extent of contamination

EquipmentEquipment

– Grab or core samplersGrab or core samplers

– GPSGPS

Largely the same as reconn…Largely the same as reconn…

Definitive Survey ComponentsDefinitive Survey Components

– Sampling designSampling design– Sample collection technique(s)Sample collection technique(s)– Sample analysis technique(s)Sample analysis technique(s)– Field and lab QA/QCField and lab QA/QC– Data interpretationData interpretation– Data mapping, volumetric Data mapping, volumetric

calculationscalculations– Modeling (?)Modeling (?)

Sampling DesignSampling Design

WhatWhat samples will be collected samples will be collected– Whole sedimentWhole sediment– ElutriateElutriate– Pore waterPore water

How manyHow many samples will be collected samples will be collected

WhereWhere samples will be collected samples will be collected

HowHow samples will be collected samples will be collected

((WhenWhen samples will be collected) samples will be collected)

Sampling Design – How Many?Sampling Design – How Many?

Statistical calculations, with existing Statistical calculations, with existing datadata

n = n = VarianceVariance

MeanMean22 x Precision x Precision22

- Requires historic data set- Requires historic data set

- Really only appropriate for data from a - Really only appropriate for data from a single stationsingle station!!

Sampling Design – How Many?Sampling Design – How Many?

Calculated ‘n’ is the number of samples Calculated ‘n’ is the number of samples that yields an overall that yields an overall meanmean concentration for the entire study areaconcentration for the entire study area

Sometimes want to identify Sometimes want to identify hot spotshot spots, , not average conditionsnot average conditions

Sampling Design – How Many?Sampling Design – How Many?

Geostatistical modelsGeostatistical models

Elipgrid-PCElipgrid-PC

– Design of sampling gridsDesign of sampling grids

– Probability of locating “hot spots”Probability of locating “hot spots”

– Hot spot size, shape, orientation, + Hot spot size, shape, orientation, + grid spacing (= number of samples)grid spacing (= number of samples)

http://dqo.pnl.gov/software/elipgrid.htmhttp://dqo.pnl.gov/software/elipgrid.htm

Elipgrid ExampleElipgrid Example

Canals on Lake St. Clair (MI)Canals on Lake St. Clair (MI)

Surface areaSurface area = 233,000 ft = 233,000 ft22 = 21,700 m = 21,700 m22

- About 6 football fields- About 6 football fields

Square gridSquare grid

95 % confidence95 % confidence

Circular hot spotCircular hot spot

Calculate Calculate how many sampleshow many samples for for different hot spot sizesdifferent hot spot sizes

Elipgrid ExampleElipgrid Example

Hot Spot Radius (m)Hot Spot Radius (m) # Samples# Samples

11 7,787 7,787

55 312 312

1010 7878

1515 3535

2020 2020

Often not happy with results!Often not happy with results!

Sampling Design – Where?Sampling Design – Where?

Objective Objective of the studyof the study

Cost-effectivenessCost-effectiveness– Use Elipgrid-PCUse Elipgrid-PC

Patterns of sediment Patterns of sediment contamination contamination variabilityvariability

Practical considerationsPractical considerations– $$$$$$$$$$

Simple Random SamplingSimple Random Sampling

FlowFlow

Systematic Grid SamplingSystematic Grid Sampling

FlowFlow

Subjective SamplingSubjective Sampling

OutfallOutfall

FlowFlow

Stratified Random SamplingStratified Random Sampling

GravelGravel

BarBar

Silt BarSilt Bar

FlowFlow

Some Sampling Design Some Sampling Design GuidanceGuidance

Contaminant Contaminant distribution:distribution:

Random & uniformRandom & uniform

Known strataKnown strata

Known hot spotsKnown hot spots

Linear trends, or Linear trends, or mapping importantmapping important

Recommended Recommended strategy:strategy:

Random samplingRandom sampling

Stratified random Stratified random samplingsampling

Subjective samplingSubjective sampling

Systematic grid Systematic grid samplingsampling

Sample CollectionSample Collection

Grab samplersGrab samplers

Core samplersCore samplers

Grab SamplingGrab Sampling

More “recent” sedimentsMore “recent” sediments

Mixed, mobile surface layerMixed, mobile surface layer

““Biologically active” zoneBiologically active” zone

Grab Samplers…Grab Samplers…

Require smaller sampling vesselsRequire smaller sampling vessels

Changing sediment composition = Changing sediment composition = variable variable penetration depthspenetration depths

– Silt > sand > gravel or claySilt > sand > gravel or clay

– Watch for “buried” sampler in soft Watch for “buried” sampler in soft sedimentssediments

Ekman Grab SamplerEkman Grab Sampler

(Kahl Scientific Co.)(Kahl Scientific Co.)

Ekman in dugout canoeEkman in dugout canoe

Ponar samplerPonar sampler

Ponar Sampling in WhalerPonar Sampling in Whaler

Van Veen Grab SamplerVan Veen Grab Sampler

Grab Sampling is Dirty Work!Grab Sampling is Dirty Work!

Capacity of Grab SamplersCapacity of Grab Samplers

Ekman = Ekman = 3.5 L3.5 L

Petite Ponar = Petite Ponar = 2.4 L 2.4 L

Standard Ponar = Standard Ponar = 8.2 L8.2 L

Van Veen = Van Veen = 24 L24 L

Core SamplingCore Sampling

Recent to older sedimentsRecent to older sediments

Stratified, less mobile depositsStratified, less mobile deposits

Aerobic Aerobic → anaerobic sediment→ anaerobic sediment

– Influences metal & nutrient Influences metal & nutrient availabilityavailability

Core Samplers…Core Samplers…

May distort sediment column May distort sediment column (smearing, compression) or not sample (smearing, compression) or not sample completely (rodding)completely (rodding)

May require larger sampling vesselsMay require larger sampling vessels

Changing sediment composition = Changing sediment composition = variable variable penetration depthpenetration depth– Silt > sand > gravel or claySilt > sand > gravel or clay

Core Sampler TypesCore Sampler Types

Hand corersHand corers– Cores = a few feet long, 2” diameterCores = a few feet long, 2” diameter– Shallow waterShallow water

Gravity corers, piston corers, etc.Gravity corers, piston corers, etc.– Cores < 5’ longCores < 5’ long– Deep waterDeep water

VibrocorersVibrocorers– Cores = up to 20’ long, 4” diameterCores = up to 20’ long, 4” diameter– Deep water (> 1,000’)Deep water (> 1,000’)

Hand-coringHand-coringCoreCore TubeTube Plastic tube – drive in with Plastic tube – drive in with

fence post driver or sledgefence post driver or sledge

Can’t drive in farther Can’t drive in farther than can be pulled out than can be pulled out by hand, or with small by hand, or with small

winchwinch

Hand-coringHand-coring

Hand-coringHand-coring

SubsampleSubsample

sleevesleeve

Gravity CorerGravity Corer

Balcheck corerBalcheck corer

Requires winchRequires winch– 50 lbs. +50 lbs. +

Core = a few feet Core = a few feet long, 2”-3” diameterlong, 2”-3” diameter

(Wildlife Supply Co.)(Wildlife Supply Co.)

Vibrocore SamplingVibrocore Sampling

Rossfelder = www.rossfelder.comRossfelder = www.rossfelder.com

Rossfelder P-3 or P-5 vibrocore headRossfelder P-3 or P-5 vibrocore headSubmersible to 2,000’Submersible to 2,000’Cores 2”-4” diameter, up to ~ 15’ longCores 2”-4” diameter, up to ~ 15’ longVC head = 150 lbsVC head = 150 lbsVC head + full 15’ core tube = 300+ lbsVC head + full 15’ core tube = 300+ lbs

Rossfelder P-5 Rossfelder P-5 vibrocorervibrocorer– 150 pounds150 pounds– 3,400 vpm3,400 vpm– Cores to ~ 15 feetCores to ~ 15 feet– Less disruption of Less disruption of

sediment column sediment column than “push cores”than “push cores”

Vibrocoring from Vibrocoring from the the R.V. MudpuppyR.V. Mudpuppy

Vibrocoring from the Vibrocoring from the R.V. MudpuppyR.V. Mudpuppy

Vibrocoring from a Pontoon BoatVibrocoring from a Pontoon Boat

Vibrocoring from a ZodiacVibrocoring from a Zodiac

Vibrocoring from john boatsVibrocoring from john boats

Vibrocorer suspended from boom truckVibrocorer suspended from boom truck

CorerCorer headhead

Core SamplingCore Sampling

Core to “refusal” Core to “refusal” where possiblewhere possible

In impoundments, In impoundments, try for original try for original terrestrial soilterrestrial soil

Core TubesCore Tubes

1/8”, 4” OD 1/8”, 4” OD Lexan tubingLexan tubing– Polycarbonate resinPolycarbonate resin

– Tougher than CAB, but more brittleTougher than CAB, but more brittle

– Not easily cut into sectionsNot easily cut into sections

– Available in other thicknesses & Available in other thicknesses & diametersdiameters

Core TubesCore Tubes

3/32” thick, 4” OD 3/32” thick, 4” OD cellulose acetate cellulose acetate butyrate (CABbutyrate (CAB) tubing) tubing

– Easily cut into sections & cappedEasily cut into sections & capped

– Available in other thicknesses & Available in other thicknesses & diametersdiameters

Core CatchersCore Catchers

From Wildlife Supply Co.From Wildlife Supply Co.

Core ProcessingCore Processing

““Processing”:Processing”:1.1. Cut tube into sections, if necessaryCut tube into sections, if necessary2.2. Open core tubeOpen core tube3.3. Document core stratigraphyDocument core stratigraphy4.4. Collect sub-samplesCollect sub-samples

Can be done on sampling vessel or on Can be done on sampling vessel or on shoreshore

– On shore = more people, but fasterOn shore = more people, but faster

Fein SawFein Saw

Opening tube with a FeinOpening tube with a Fein®® saw saw

Subsampling the CoreSubsampling the Core

Plan ahead of timePlan ahead of time

Consider necessary Consider necessary sample volume sample volume (= minimum (= minimum sampling interval)sampling interval)

Plan for field QC Plan for field QC samplessamples– Usually field dupsUsually field dups

Documenting the CoreDocumenting the Core

Photographs:Photographs:

Label in each photoLabel in each photo

Put measuring tape Put measuring tape in photoin photo

Field NotesField Notes

Color, texture, etc.Color, texture, etc.

Don’t wear polarized Don’t wear polarized sunglassessunglasses

A word about Sediment Dating…A word about Sediment Dating…

A word about Sediment Dating…A word about Sediment Dating…

Lead-210Lead-210

tt1/21/2 = 22.3 years = 22.3 years

Gone after 6-7 half-lives (130-160 years)Gone after 6-7 half-lives (130-160 years)

Best in lake environmentsBest in lake environments

Often get confusing data; Often get confusing data; collect collect multiple coresmultiple cores

Toxicity TestingToxicity Testing

Done less often than chemical testing Done less often than chemical testing or biological communitiesor biological communities

Why do toxicity testing?Why do toxicity testing?– Integrates effectsIntegrates effects– Not affected by habitat qualityNot affected by habitat quality– Uses important food chain organismsUses important food chain organisms– Direct proof of effectsDirect proof of effects

No effect = no pollution (?)No effect = no pollution (?)

Freshwater Bioassay OrganismsFreshwater Bioassay OrganismsMidge larvae AmphipodMidge larvae Amphipod

Toxicity Test TypesToxicity Test Types

Acute or ChronicAcute or Chronic

Standardized by EPA, ASTM, & Standardized by EPA, ASTM, & Environment CanadaEnvironment Canada

AcuteAcute = 10-14 days; endpoints = = 10-14 days; endpoints = survival, growthsurvival, growth

ChronicChronic = 28-60 days; endpoints = = 28-60 days; endpoints = survival, growth, reproductionsurvival, growth, reproduction

Bioaccumulation TestingBioaccumulation Testing

Three kinds:Three kinds:

Laboratory testsLaboratory tests

Field studiesField studies– Caged organismsCaged organisms– Resident Resident

organismsorganisms

ModelsModels

Bioaccumulation TestingBioaccumulation TestingLaboratory testLaboratory test = aquatic oligochaete = aquatic oligochaete Lumbriculus variagatusLumbriculus variagatus

28 days28 days

Accumulation Factor (AF) = Accumulation Factor (AF) = conc. in wormsconc. in worms

conc. in sedimentconc. in sediment

Bioaccumulation ModelingBioaccumulation Modeling

Simplest = Equilibrium Partitioning Simplest = Equilibrium Partitioning ModelingModeling

LipidsLipids

Sediment CarbonSediment Carbon Interstitial WaterInterstitial Water

Equilibrium Partition ModelingEquilibrium Partition Modeling

(Ct(Ctssss/L) = (Cs/TOC) x AF/L) = (Cs/TOC) x AF

CtCtssss = = fish tissue conc. at steady statefish tissue conc. at steady state

L = L = fish tissue lipid contentfish tissue lipid contentCs = Cs = sediment concentrationsediment concentrationTOC = TOC = sediment total organic carbonsediment total organic carbonAF = AF = biota/sediment accumulation biota/sediment accumulation

factor (BSAF)factor (BSAF)

More sophisticated More sophisticated bioaccumulation modelsbioaccumulation models

Environmental propertiesEnvironmental properties– Water temperatureWater temperature– DOC, TOCDOC, TOC

Chemical characteristicsChemical characteristics– Water concentrationWater concentration– Sediment concentrationSediment concentration– Octanol-water partition coefficient (Kow)Octanol-water partition coefficient (Kow)

Species characteristicsSpecies characteristics– Lipid contentLipid content– DietDiet– Life history & food chain positionLife history & food chain position

Bioaccumulation TestingBioaccumulation Testing

My preferred hierarchy:My preferred hierarchy:

Caged organisms & laboratory studiesCaged organisms & laboratory studiesResident YOY fishResident YOY fishResident adult bottom-feeding fish, or Resident adult bottom-feeding fish, or other benthic organismsother benthic organismsModelsModels

Always better to measure than to modelAlways better to measure than to model

Dam-Specific Effects IssuesDam-Specific Effects Issues

Lower water level = turn aquatic Lower water level = turn aquatic problem into terrestrial problemproblem into terrestrial problem

– Different toxicity & bioaccumulation Different toxicity & bioaccumulation routes & endpoints (species)routes & endpoints (species)

– Top predator now an eagle or mink Top predator now an eagle or mink instead of a fishinstead of a fish

– Increase human exposure ?Increase human exposure ?

Data Interpretation:Data Interpretation:Sediment Quality CriteriaSediment Quality Criteria

Uses:Uses:

Evaluate sediment qualityEvaluate sediment quality

Establish cleanup objectivesEstablish cleanup objectives

Assess suitability for open-water Assess suitability for open-water disposaldisposal

Assess fill quality for shoreline Assess fill quality for shoreline developmentdevelopment

Agree to at start of projectAgree to at start of project

Chemical Concentration SQCChemical Concentration SQC

Tied to Tied to biological effectsbiological effects

– Cu > X ppm = mortality in mayfliesCu > X ppm = mortality in mayflies

Usually tied to Usually tied to toxicitytoxicity rather than rather than bioaccumulation or changes in bioaccumulation or changes in community structure or human healthcommunity structure or human health

More often More often guidelinesguidelines than than regulationsregulations

Database Chemical SQCDatabase Chemical SQCIn

crea

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Incr

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PresumedPresumed

NontoxicNontoxic

PresumedPresumed

ToxicToxic

PossiblyPossibly

ToxicToxic

PECPEC

TECTEC

Examples (Examples (mg/Kg DWmg/Kg DW))

ChemicalChemical TECTEC PECPEC

Total PCBsTotal PCBs 0.060.06 0.680.68

Total DDTTotal DDT 0.0050.005 0.570.57

CadmiumCadmium 0.990.99 4.984.98

LeadLead 35.835.8 128128

ZincZinc 121121 459459

(McDonald et al., 2000)(McDonald et al., 2000)

Wisconsin SQC GuidanceWisconsin SQC Guidance

““Consensus-Based Sediment Qaulity Consensus-Based Sediment Qaulity Guidelines – Recommendations for Use Guidelines – Recommendations for Use

and Application – Interim Guidance”and Application – Interim Guidance”

WT-732 2003WT-732 2003

Wisconsin DNR Contaminated Sediment Wisconsin DNR Contaminated Sediment Standing TeamStanding Team

One Scenario…One Scenario…In

crea

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Incr

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Co

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ntr

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No additionalNo additional

samplingsampling

Additional samplingAdditional sampling

definitely requireddefinitely required

Additional sampling/assessment Additional sampling/assessment may be requiredmay be required

PECPEC

TECTEC

Wisconsin = Midpoint Wisconsin = Midpoint Concentration & Concern LevelsConcentration & Concern Levels

Incr

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Co

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ntr

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crea

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PECPEC

TECTEC

““MEC”MEC”

Level 4Level 4

Level 3Level 3

Level 2Level 2

Level 1Level 1

Use Levels to Rank SitesUse Levels to Rank Sites

Other “SQC”Other “SQC”

SoilSoil quality criteria quality criteria

Residential or Industrial land useResidential or Industrial land use

PECPEC Resid. SoilResid. Soil Ind. SoilInd. Soil

PCBs PCBs 0.680.68 44 16 16

Copper Copper 149149 20,000 20,000 73,00073,000

Lead Lead 128128 400400 900 900

(mg/Kg DW)(mg/Kg DW)

Dam-Specific SQC IssuesDam-Specific SQC Issues

Original native soil = excavation depthOriginal native soil = excavation depth

– Easy to determine excavation depthEasy to determine excavation depth

– Concentrations = Concentrations = cleanup criteria?cleanup criteria?

Recon vs. Definitive SurveysRecon vs. Definitive Surveys

Start with Recon SurveyStart with Recon Survey

– Limited number of samplesLimited number of samples

– Bulk sediment chemistryBulk sediment chemistry

– Compare to SQCCompare to SQC

– Grain size & organic carbon contentGrain size & organic carbon content

Recon vs. Definitive SurveysRecon vs. Definitive Surveys

Depending on results of Recon Survey, Depending on results of Recon Survey, may:may:

– No No additional samplingadditional sampling

– LimitedLimited additional sampling, for additional sampling, for chemistrychemistry

– ExtensiveExtensive additional sampling, for additional sampling, for chemistry, toxicity, bioaccumulationchemistry, toxicity, bioaccumulation

Sediment Management Framework

Fullremoval

Partialremoval

Cap or isolate

Natural erosion& deposition

Stagedremoval

Low transport capacity and/or

low d/s sensitivity

High transport capacity and/or

high d/s sensitivity

Not bioavailable Bioavailable

(Optional)

Complete Dam Removal & Complete Dam Removal & Natural Erosion & DepositionNatural Erosion & Deposition

Issue:Issue: demonstrate transport & demonstrate transport & deposition will not:deposition will not:

Cause Cause long-termlong-term adverse physical adverse physical habitat changes downstream or habitat changes downstream or upstreamupstream– Fill pools, bury riffles, etc. downstreamFill pools, bury riffles, etc. downstream– Upstream channel incisionUpstream channel incision

Increase Increase bioavailabilitybioavailability of contaminants of contaminants

Staged Dam Removal & Staged Dam Removal & Natural Erosion & DepositionNatural Erosion & Deposition

Issues:Issues:

1.1. Assess Assess engineering suitabilityengineering suitability of dam of dam for staged removalfor staged removal

2.2. Assess impacts of Assess impacts of water flows and water flows and sediment loadssediment loads on downstream on downstream geomorphology and ecologygeomorphology and ecology

3.3. ((PlusPlus issues for complete dam issues for complete dam removal)removal)

On-Site Isolation or CappingOn-Site Isolation or Capping

Issue:Issue: demonstrate that: demonstrate that:

Capping will reduce contaminant Capping will reduce contaminant availability to aquatic and terrestrial availability to aquatic and terrestrial ecosystems, and humansecosystems, and humans

Capping won’t disrupt remaining Capping won’t disrupt remaining ecosystemecosystem– Decrease riparian zone, wetlands, Decrease riparian zone, wetlands,

bottomlands, etc.bottomlands, etc.

Partial Removal of Hot SpotsPartial Removal of Hot Spots

Tasks:Tasks:

1.1. Locate Locate hot spotshot spots

2.2. Remove & disposeRemove & dispose of sediment of sediment In the “dry” or “wet”In the “dry” or “wet”

3.3. Demonstrate that remaining sediment Demonstrate that remaining sediment is is nontoxicnontoxic

4.4. Post-remediation Post-remediation monitoringmonitoring

Sediment Removal – Sediment Removal – “Wet” & “Dry”“Wet” & “Dry”

(HRC, Inc.)(HRC, Inc.)

(ECT, Inc.)(ECT, Inc.)

Full Removal of All SedimentFull Removal of All Sediment

Tasks:Tasks:

1.1. Identify Identify extentextent of contaminated of contaminated sediment, sediment, inin 3D3D

2.2. Characterize Characterize degreedegree of contamination, of contamination, for disposal decisionsfor disposal decisions

3.3. Remove & disposeRemove & dispose

4.4. Post-remediation Post-remediation monitoringmonitoring

Contaminated Seds = Contaminated Seds = Run AwayRun Away

Long term = Long term = bad ideabad idea

Reservoir = contaminant Reservoir = contaminant “time “time bomb”bomb”

Combine Combine dam hazard assessmentdam hazard assessment with contaminant assessment?with contaminant assessment?

Post-Remediation MonitoringPost-Remediation Monitoring

Sediment analysesSediment analyses

Channel geometry & substrate Channel geometry & substrate measurementsmeasurements

Revegetation rate of former Revegetation rate of former impoundmentimpoundment

Fish & macroinvertebratesFish & macroinvertebrates

Changes in recreational & other social Changes in recreational & other social aspects and perceptionsaspects and perceptions

““There is something fascinating There is something fascinating about science. One gets such a about science. One gets such a

wholesale return of conjecture out of wholesale return of conjecture out of a trifling investment of fact.”a trifling investment of fact.”

( (Mark Twain, 1874)Mark Twain, 1874)

Objective = optimize Objective = optimize representativenessrepresentativeness of our facts, to of our facts, to

improve the quality of our improve the quality of our conjecturesconjectures