SEDIMENT ASSESSMENT & MANAGEMENT FOR DAM REMOVAL PROJECTS Joe Rathbun Michigan Dept. of Environmental Quality Water Bureau

Outline Basic Concepts Sample Collection –Survey design –Grab and core sampling Effects Assessment –Toxicity –Bioaccumulation –Sediment quality criteria Sediment Management Options

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

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

Basic Concepts: Sediment Transport Rivers do 2 things very well –Move water –Move sediment Most sediment transported during floods

Basic Concepts: Reservoirs are Sediment Traps Many trap 95 % of the sediment that enters them from upstream Large sediment particles form deltas at upstream end Small sediment particles transported farther into reservoir

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

Basic Concepts: Contaminant Distribution ↓ grain size = ↑ contaminant concentration –Silt = ↑ TOC, for organics (& metals) –Clay = ↑ binding sites for metals Grain size distribution “predictable” –Upper impoundment = large particles –Lower impoundment = fines

Organic Contaminants: Sediment vs. Water Concentrations Depending on contaminant polarity, solubility, etc. … Sediment > water by factor of 1,000 to 10,000,000

Almost always have to sample… Because of unexpected historic contaminant sources: Brick factories = Cd, Pb, Ni, Ba, Se, Co Orchards & tobacco fields = As, Hg Tanneries = Cd, Cr, As, Hg Coal gasification plants = PAHs, metals Glass factories = As, other metals Cemeteries = Pb, As, Hg Dye manufacturers = metals

Sampling Survey Design First step in sampling Extremely important to data quality Sediment quality data are easy to collect but difficult to interpret unless obtained using a well-designed survey

Sampling Survey Design: Field vs. Lab Heterogeneity Sources of data variability –In-situ heterogeneity, in the field –Collection biases & inaccuracies –Lab biases & inaccuracies PCBs in soil (EPA, 1992): –Lab = < 1 % of data variability –Location of sample = 92 % of data variability

Simplest Case: Small Dam…Rural Area…No Money Minimum data required: Demonstrate lack of upstream sources Find silt deposits & establish thickness Collect minimal number of samples –≥ 1 from each silt deposit, & combine? Analyze for organics & metals Compare to sediment quality criteria Sample benthos?

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

Reconnaissance Survey Objectives –Sampling access –Sample collectability –Qualitatively assess nature and extent of contaminated deposits Equipment –Probing rod –Small grab or core sampler –Equipment for hydrographic survey –GPS

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

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

Definitive Survey Components –Sampling design –Sample collection technique(s) –Sample analysis technique(s) –Field and lab QA/QC –Data interpretation –Data mapping, volumetric calculations –Modeling (?)

Sampling Design What samples will be collected –Whole sediment –Elutriate –Pore water How many samples will be collected Where samples will be collected How samples will be collected (When samples will be collected)

Sampling Design – How Many? Statistical calculations, with existing data n = Variance n = Variance Mean 2 x Precision 2 Mean 2 x Precision 2 - Requires historic data set - Really only appropriate for data from a single station!

Sampling Design – How Many? Calculated ‘n’ is the number of samples that yields an overall mean concentration for the entire study area Sometimes want to identify hot spots, not average conditions

Sampling Design – How Many? Geostatistical models Elipgrid-PC –Design of sampling grids –Probability of locating “hot spots” –Hot spot size, shape, orientation, + grid spacing (= number of samples)

Elipgrid Example Canals on Lake St. Clair (MI) Surface area = 233,000 ft 2 = 21,700 m 2 - About 6 football fields Square grid 95 % confidence Circular hot spot Calculate how many samples for different hot spot sizes

Elipgrid Example Hot Spot Radius (m)# Samples 1 7, Often not happy with results!

Sampling Design – Where? Objective of the study Cost-effectiveness –Use Elipgrid-PC Patterns of sediment contamination variability Practical considerations –$$$$$

Simple Random Sampling Flow

Systematic Grid Sampling Flow

Subjective Sampling Outfall Flow

Stratified Random Sampling GravelBar Silt Bar Flow

Some Sampling Design Guidance Contaminant distribution: Random & uniform Known strata Known hot spots Linear trends, or mapping important Recommended strategy: Random sampling Stratified random sampling Subjective sampling Systematic grid sampling

Sample Collection Grab samplers Grab samplers Core samplers Core samplers

Grab Sampling More “recent” sediments Mixed, mobile surface layer “Biologically active” zone

Grab Samplers… Require smaller sampling vessels Changing sediment composition = variable penetration depths –Silt > sand > gravel or clay –Watch for “buried” sampler in soft sediments

Ekman Grab Sampler (Kahl Scientific Co.)

Ekman in dugout canoe

Ponar sampler

Ponar Sampling in Whaler

Van Veen Grab Sampler

Grab Sampling is Dirty Work!

Capacity of Grab Samplers Ekman = 3.5 L Petite Ponar = 2.4 L Standard Ponar = 8.2 L Van Veen = 24 L

Core Sampling Recent to older sediments Stratified, less mobile deposits Aerobic → anaerobic sediment –Influences metal & nutrient availability

Core Samplers… May distort sediment column (smearing, compression) or not sample completely (rodding) May require larger sampling vessels Changing sediment composition = variable penetration depth –Silt > sand > gravel or clay

Core Sampler Types 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’)

Hand-coring Core Tube Plastic tube – drive in with fence post driver or sledge Can’t drive in farther than can be pulled out by hand, or with small winch

Hand-coring

Hand-coring Subsamplesleeve

Gravity Corer Balcheck corer Requires winch –50 lbs. + Core = a few feet long, 2”-3” diameter (Wildlife Supply Co.)

Vibrocore Sampling Rossfelder = Rossfelder P-3 or P-5 vibrocore head Submersible to 2,000’ Cores 2”-4” diameter, up to ~ 15’ long VC head = 150 lbs VC head + full 15’ core tube = 300+ lbs

Rossfelder P-5 vibrocorer –150 pounds –3,400 vpm –Cores to ~ 15 feet –Less disruption of sediment column than “push cores”

Vibrocoring from the R.V. Mudpuppy

Vibrocoring from a Pontoon Boat

Vibrocoring from a Zodiac

Vibrocoring from john boats

Vibrocorer suspended from boom truck Corer head

Core Sampling Core to “refusal” where possible In impoundments, try for original terrestrial soil

Core Tubes 1/8”, 4” OD Lexan tubing –Polycarbonate resin –Tougher than CAB, but more brittle –Not easily cut into sections –Available in other thicknesses & diameters

Core Tubes 3/32” thick, 4” OD cellulose acetate butyrate (CAB) tubing –Easily cut into sections & capped –Available in other thicknesses & diameters

Core Catchers From Wildlife Supply Co.

Core Processing “Processing”: 1.Cut tube into sections, if necessary 2.Open core tube 3.Document core stratigraphy 4.Collect sub-samples Can be done on sampling vessel or on shore –On shore = more people, but faster

Fein Saw

Opening tube with a Fein ® saw

Subsampling the Core Plan ahead of time Consider necessary sample volume (= minimum sampling interval) Plan for field QC samples –Usually field dups

Documenting the Core Photographs: Label in each photo Put measuring tape in photo Field Notes Color, texture, etc. Don’t wear polarized sunglasses

A word about Sediment Dating…

Lead-210 t 1/2 = 22.3 years Gone after 6-7 half-lives ( years) Best in lake environments Often get confusing data; collect multiple cores

Toxicity Testing Done less often than chemical testing or biological communities Why do toxicity testing? –Integrates effects –Not affected by habitat quality –Uses important food chain organisms –Direct proof of effects No effect = no pollution (?)

Freshwater Bioassay Organisms Midge larvae Amphipod

Toxicity Test Types Acute or Chronic Standardized by EPA, ASTM, & Environment Canada Acute = days; endpoints = survival, growth Chronic = days; endpoints = survival, growth, reproduction

Bioaccumulation Testing Three kinds: Laboratory tests Field studies –Caged organisms –Resident organisms Models

Bioaccumulation Testing Laboratory test = aquatic oligochaete Lumbriculus variagatus 28 days Accumulation Factor (AF) = conc. in worms conc. in sediment conc. in sediment

Bioaccumulation Modeling Simplest = Equilibrium Partitioning Modeling Lipids Sediment Carbon Interstitial Water

Equilibrium Partition Modeling (Ct ss /L) = (Cs/TOC) x AF Ct ss =fish tissue conc. at steady state L = fish tissue lipid content Cs = sediment concentration TOC = sediment total organic carbon AF = biota/sediment accumulation factor (BSAF)

More sophisticated bioaccumulation models Environmental properties –Water temperature –DOC, TOC Chemical characteristics –Water concentration –Sediment concentration –Octanol-water partition coefficient (Kow) Species characteristics –Lipid content –Diet –Life history & food chain position

Bioaccumulation Testing My preferred hierarchy: Caged organisms & laboratory studies Resident YOY fish Resident adult bottom-feeding fish, or other benthic organisms Models Always better to measure than to model

Dam-Specific Effects Issues Lower water level = turn aquatic problem into terrestrial problem –Different toxicity & bioaccumulation routes & endpoints (species) –Top predator now an eagle or mink instead of a fish –Increase human exposure ?

Data Interpretation: Sediment Quality Criteria Uses: Evaluate sediment quality Establish cleanup objectives Assess suitability for open-water disposal Assess fill quality for shoreline development Agree to at start of project

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

Database Chemical SQC Increasing Concentration PresumedNontoxic PresumedToxic PossiblyToxic PEC TEC

Examples ( mg/Kg DW ) ChemicalTECPEC Total PCBs Total DDT Cadmium Lead Zinc (McDonald et al., 2000)

Wisconsin SQC Guidance “Consensus-Based Sediment Qaulity Guidelines – Recommendations for Use and Application – Interim Guidance” WT Wisconsin DNR Contaminated Sediment Standing Team

One Scenario… Increasing Concentration No additional sampling Additional sampling definitely required Additional sampling/assessment may be required PEC TEC

Wisconsin = Midpoint Concentration & Concern Levels Increasing Concentration PEC TEC “MEC” Level 4 Level 3 Level 2 Level 1 Use Levels to Rank Sites

Other “SQC” Soil quality criteria Residential or Industrial land use PEC Resid. Soil Ind. Soil PCBs Copper ,000 73,000 Lead (mg/Kg DW)

Dam-Specific SQC Issues Original native soil = excavation depth –Easy to determine excavation depth –Concentrations = cleanup criteria?

Recon vs. Definitive Surveys Start with Recon Survey –Limited number of samples –Bulk sediment chemistry –Compare to SQC –Grain size & organic carbon content

Recon vs. Definitive Surveys Depending on results of Recon Survey, may: –No additional sampling –Limited additional sampling, for chemistry –Extensive additional sampling, for chemistry, toxicity, bioaccumulation

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

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 of contaminants

Staged Dam Removal & Natural Erosion & Deposition Issues: 1. Assess engineering suitability of dam for staged removal 2. Assess impacts of water flows and sediment loads on downstream geomorphology and ecology 3. (Plus issues for complete dam removal)

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.

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

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

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

Contaminated Seds = Run Away Long term = bad idea Reservoir = contaminant “time bomb” Combine dam hazard assessment with contaminant assessment?

Post-Remediation Monitoring Sediment analyses Channel geometry & substrate measurements Revegetation rate of former impoundment Fish & macroinvertebrates Changes in recreational & other social aspects and perceptions

“There is something fascinating about science. One gets such a wholesale return of conjecture out of a trifling investment of fact.” (Mark Twain, 1874) Objective = optimize representativeness of our facts, to improve the quality of our conjectures