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Title: SEDIMENT ASSESSMENT


1
SEDIMENT ASSESSMENT MANAGEMENT FOR DAM REMOVAL
PROJECTS
  • Joe Rathbun
  • Michigan Dept. of Environmental Quality
  • Water Bureau
  • 517-373-8868
  • rathbunj_at_michigan.gov

2
Outline
  • Basic Concepts
  • Sample Collection
  • Survey design
  • Grab and core sampling
  • Effects Assessment
  • Toxicity
  • Bioaccumulation
  • Sediment quality criteria
  • Sediment Management Options

3
Sediment Assessment Framework
4
Sediment Management Framework
5
Basic Concepts Sediment Transport
  • Rivers do 2 things very well
  • Move water
  • Move sediment
  • Most sediment transported during floods

6
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

7
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

8
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

9
Organic ContaminantsSediment vs. Water
Concentrations
  • Depending on contaminant polarity, solubility,
    etc.
  • Sediment gt water by factor of 1,000 to 10,000,000

10
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

11
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

12
Sampling Survey DesignField 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 lt 1 of data variability
  • Location of sample 92 of data variability

13
Simplest CaseSmall DamRural AreaNo 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?

14
Preferred Survey Design Process
  • Establish study objectives, evaluate existing
    data, etc.
  • Conduct reconnaissance survey
  • Refine study objectives
  • - Choose minimum number of stations that are
    representative of study area
  • Conduct definitive survey

15
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

16
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

17
Definitive Survey
  • Objective
  • Quantitatively establish magnitude and extent of
    contamination
  • Equipment
  • Grab or core samplers
  • GPS
  • Largely the same as reconn

18
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 (?)

19
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)

20
Sampling Design How Many?
  • Statistical calculations, with existing data
  • n Variance
  • Mean2 x Precision2
  • - Requires historic data set
  • - Really only appropriate for data from a single
    station!

21
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

22
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)
  • http//dqo.pnl.gov/software/elipgrid.htm

23
Elipgrid Example
  • Canals on Lake St. Clair (MI)
  • Surface area 233,000 ft2 21,700 m2
  • - About 6 football fields
  • Square grid
  • 95 confidence
  • Circular hot spot
  • Calculate how many samples for different hot spot
    sizes

24
Elipgrid Example
  • Hot Spot Radius (m) Samples
  • 1 7,787
  • 5 312
  • 10 78
  • 15 35
  • 20 20
  • Often not happy with results!

25
Sampling Design Where?
  • Objective of the study
  • Cost-effectiveness
  • Use Elipgrid-PC
  • Patterns of sediment contamination variability
  • Practical considerations

26
Simple Random Sampling
Flow
27
Systematic Grid Sampling
Flow
28
Subjective Sampling
Flow
Outfall
29
Stratified Random Sampling
Gravel Bar
Flow
Silt Bar
30
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

31
Sample Collection
  • Grab samplers
  • Core samplers

32
Grab Sampling
  • More recent sediments
  • Mixed, mobile surface layer
  • Biologically active zone

33
Grab Samplers
  • Require smaller sampling vessels
  • Changing sediment composition variable
    penetration depths
  • Silt gt sand gt gravel or clay
  • Watch for buried sampler in soft sediments

34
Ekman Grab Sampler
(Kahl Scientific Co.)
35
Ekman in dugout canoe
36
Ponar sampler
37
Ponar Sampling in Whaler
38
Van Veen Grab Sampler
39
Grab Sampling is Dirty Work!
40
Capacity of Grab Samplers
  • Ekman 3.5 L
  • Petite Ponar 2.4 L
  • Standard Ponar 8.2 L
  • Van Veen 24 L

41
Core Sampling
  • Recent to older sediments
  • Stratified, less mobile deposits
  • Aerobic ? anaerobic sediment
  • Influences metal nutrient availability

42
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 gt sand gt gravel or clay

43
Core Sampler Types
  • Hand corers
  • Cores a few feet long, 2 diameter
  • Shallow water
  • Gravity corers, piston corers, etc.
  • Cores lt 5 long
  • Deep water
  • Vibrocorers
  • Cores up to 20 long, 4 diameter
  • Deep water (gt 1,000)

44
Hand-coring
Core Tube
Plastic tube drive in with fence post driver or
sledge
Cant drive in farther than can be pulled out by
hand, or with small winch
45
Hand-coring
46
Hand-coring
Subsample sleeve
47
Gravity Corer
  • Balcheck corer
  • Requires winch
  • 50 lbs.
  • Core a few feet long, 2-3 diameter

(Wildlife Supply Co.)
48
Vibrocore Sampling
  • Rossfelder www.rossfelder.com
  • 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

49
  • Rossfelder P-5 vibrocorer
  • 150 pounds
  • 3,400 vpm
  • Cores to 15 feet
  • Less disruption of sediment column than push
    cores

50
Vibrocoring from the R.V. Mudpuppy
51
Vibrocoring from the R.V. Mudpuppy
52
Vibrocoring from a Pontoon Boat
53
Vibrocoring from a Zodiac
54
Vibrocoring from john boats
55
Vibrocorer suspended from boom truck
Corer head
56
Core Sampling
  • Core to refusal where possible
  • In impoundments, try for original terrestrial soil

57
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

58
Core Tubes
  • 3/32 thick, 4 OD cellulose acetate butyrate
    (CAB) tubing
  • Easily cut into sections capped
  • Available in other thicknesses diameters

59
Core Catchers
From Wildlife Supply Co.
60
Core Processing
  • Processing
  • Cut tube into sections, if necessary
  • Open core tube
  • Document core stratigraphy
  • Collect sub-samples
  • Can be done on sampling vessel or on shore
  • On shore more people, but faster

61
Fein Saw
62
Opening tube with a Fein saw
63
Subsampling the Core
  • Plan ahead of time
  • Consider necessary sample volume ( minimum
    sampling interval)
  • Plan for field QC samples
  • Usually field dups

64
Documenting the Core
  • Photographs
  • Label in each photo
  • Put measuring tape in photo
  • Field Notes
  • Color, texture, etc.
  • Dont wear polarized sunglasses

65
A word about Sediment Dating
66
A word about Sediment Dating
  • Lead-210
  • t1/2 22.3 years
  • Gone after 6-7 half-lives (130-160 years)
  • Best in lake environments
  • Often get confusing data collect multiple cores

67
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 (?)

68
Freshwater Bioassay OrganismsMidge larvae
Amphipod
69
Toxicity Test Types
  • Acute or Chronic
  • Standardized by EPA, ASTM, Environment Canada
  • Acute 10-14 days endpoints survival, growth
  • Chronic 28-60 days endpoints survival,
    growth, reproduction

70
Bioaccumulation Testing
  • Three kinds
  • Laboratory tests
  • Field studies
  • Caged organisms
  • Resident organisms
  • Models

71
Bioaccumulation Testing
  • Laboratory test aquatic oligochaete Lumbriculus
    variagatus
  • 28 days
  • Accumulation Factor (AF) conc. in worms
  • conc. in sediment

72
Bioaccumulation Modeling
  • Simplest Equilibrium Partitioning Modeling

Lipids
Sediment Carbon
Interstitial Water
73
Equilibrium Partition Modeling
  • (Ctss/L) (Cs/TOC) x AF
  • Ctss 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)

74
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

75
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

76
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 ?

77
Data InterpretationSediment 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

78
Chemical Concentration SQC
  • Tied to biological effects
  • Cu gt 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

79
Database Chemical SQC
Presumed Toxic
PEC
Possibly Toxic
Increasing Concentration
TEC
Presumed Nontoxic
80
Examples (mg/Kg DW)
  • Chemical TEC PEC
  • Total PCBs 0.06 0.68
  • Total DDT 0.005 0.57
  • Cadmium 0.99 4.98
  • Lead 35.8 128
  • Zinc 121 459

(McDonald et al., 2000)
81
Wisconsin SQC Guidance
  • Consensus-Based Sediment Qaulity Guidelines
    Recommendations for Use and Application Interim
    Guidance
  • WT-732 2003
  • Wisconsin DNR Contaminated Sediment Standing Team

82
One Scenario
Additional sampling definitely required
PEC
Additional sampling/assessment may be required
Increasing Concentration
TEC
No additional sampling
83
Wisconsin Midpoint Concentration Concern
Levels
Level 4
PEC
Level 3
MEC
Increasing Concentration
Level 2
TEC
Level 1
Use Levels to Rank Sites
84
Other SQC
  • Soil quality criteria
  • Residential or Industrial land use
  • PEC Resid. Soil Ind. Soil
  • PCBs 0.68 4 16
  • Copper 149 20,000 73,000
  • Lead 128 400 900
  • (mg/Kg DW)

85
Dam-Specific SQC Issues
  • Original native soil excavation depth
  • Easy to determine excavation depth
  • Concentrations cleanup criteria?

86
Recon vs. Definitive Surveys
  • Start with Recon Survey
  • Limited number of samples
  • Bulk sediment chemistry
  • Compare to SQC
  • Grain size organic carbon content

87
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

88
Sediment Management Framework
89
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

90
Staged Dam Removal Natural Erosion Deposition
  • Issues
  • Assess engineering suitability of dam for staged
    removal
  • Assess impacts of water flows and sediment loads
    on downstream geomorphology and ecology
  • (Plus issues for complete dam removal)

91
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.

92
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

93
Sediment Removal Wet Dry
(HRC, Inc.)
(ECT, Inc.)
94
Full Removal of All Sediment
  • Tasks
  • Identify extent of contaminated sediment, in 3D
  • Characterize degree of contamination, for
    disposal decisions
  • Remove dispose
  • Post-remediation monitoring

95
Contaminated Seds Run Away
  • Long term bad idea
  • Reservoir contaminant time bomb
  • Combine dam hazard assessment with contaminant
    assessment?

96
Post-Remediation Monitoring
  • Sediment analyses
  • Channel geometry substrate measurements
  • Revegetation rate of former impoundment
  • Fish macroinvertebrates
  • Changes in recreational other social aspects
    and perceptions

97
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
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