Characterizing the Post-Dredge Surface:Comparison of In-Situ (Pre-dredge) and

Post-Dredge Grab Samples at Three Sites in the Willamette River, Portland Harbor, Oregon

Michelle HollisPort of Portland

& James McMillanPortland District

Laura Inouye, Washington Department of EcologyJonathan Freedman, US Environmental Protection Agency, Region

10

PurposeCompare concentrations from pre-dredge

core samples and post-dredge grab samples at 3 sites

Examine contributions to post-dredge surface (PDS) chemistry based on site conditions

Use findings to inform risk-based regulatory decision making for dredging projects in the Portland Harbor

PDS

Dredge Prism

PDS

BEFORE AFTER

ProblemCore samples measure the pre-dredge conditionThe in-situ core sample characterizing the PDS is often

used in regulatory decision makingBUT, in-situ PDS samples don’t account for:

Post-dredge Surface (PDS)

current

fallback &physical mixing from dredging

deposition

side slopesloughing

mixing frommarine traffic

current mixing

Fallback from the dredge Physical mixing during dredging Side-slope sloughing Current mixing within the dredge

area

Deposition during/after dredging Mixing caused by natural

processes and marine traffic

(After ERDC, 2008 The Four Rs of Environmental Dredging: Resuspension, Release, Residual, and Risk [TR-08-4])

Regulatory Review of Post-Dredge Surface Regulatory agencies want to know what’s being

dredged AND what will be exposed after dredgingRegulatory concerns regarding:

Endangered speciesState water quality parameters (sediment-water

column interface)State anti-degradation policies

(i.e., exposed surface >> dredge prism = BAD)State and federal permits may require:

Monitoring after dredgingPhysical isolation of the PDS

Placement of a clean sand cover Natural infill (of cleaner sediment)

MethodsCompared concentrations of chemicals of concern:

PDS

BEFORE DREDGING

Dredge Prism

In-situ core sample

(pre-dredge estimate)

AFTER DREDGING

PDS

Post-dredge grab samples (of the actual post-dredge surface)

Methods (cont.)Examined factors contributing to PDS chemistry:

Post-dredge Surface (PDS)

current

fallback &physical mixing from dredging

deposition

side slopesloughing

mixing frommarine traffic

current mixing

(After ERDC, 2008 The Four Rs of Environmental Dredging: Resuspension, Release, Residual, and Risk [TR-08-4])

Portland Harbor Sites (3)

PORTLAND, OR

VANCOUVER, WA

Columbia R.

Willamette R.

PoP T5Willamette

FNC – PO Bar

N

2 4 60miles

PoP T2

Post Office Bar

Willamette R. FNCPost Office Bar

PORTLAND, OR

VANCOUVER, WA

Columbia R.

Willam

ette R.

Willamette R. FNC – PO BarN

2 4 60miles

DETAILS• Location: Willamette River, RM 2.1-2.4• Volume: 52,300 cy• Depth: Dredged to -40 feet CRD

(plus 2 feet advanced maintenance) • Disposal: Upland, West Hayden Is.

Placement Site • Project completed in Sept./Oct.

2011

73.2

80.483.8-36

-32

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD) VC-05

VC-01 VC-03

Downstream End (RM 2.1) Upstream End (RM 2.3)

ZINC: WILLAMETTE R., POST OFFICE BAR – 2009 pre-dredge

Feb. 2009 mudline

In-situ dredge prism core sample(PRE-dredge)

68.9226

156

In-situ PDS core sample(PRE-dredge)

8987.1

77.2DredgePrism

Zinc SL = 130 ppm

VC-02 VC-04

VC-06

Zinc Concentrations

Sample

PRE-DREDGE (Core) Zinc Screening

LevelDredge Prism

Sloughing Material

In-Situ PDS

Average 84.4 79.1 150.3 130 ppm

73.2

80.483.8-36

-32

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD) VC-05

VC-01 VC-03

BC-01 BC-02 BC-03BC-04 BC-05

Downstream End (RM 2.1) Upstream End (RM 2.3)

ZINC: WILLAMETTE R., POST OFFICE BAR – 2009 pre-dredge; 2011 post-dredge

Feb. 2009 mudline

Oct. 2011 PDS

In-situ dredge prism core sample(PRE-dredge)

68.9226

156

91 10396 97 112

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

8987.1

77.2DredgePrism

Zinc SL = 130 ppm

VC-02 VC-04

VC-06

Zinc Concentrations

Sample

PRE-DREDGE (Core)POST-DREDGE

(Grab) Zinc Screening

LevelDredge Prism

Sloughing Material

In-Situ PDS

Oct. 2011

Average 84.4 79.1 150.3 99.8 130 ppm

73.2

80.483.8-36

-32

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD) VC-05

VC-01 VC-03

BC-01 BC-02BC-03 BC-04 BC-05

Downstream End (RM 2.1) Upstream End (RM 2.3)

ZINC: WILLAMETTE R., POST OFFICE BAR – 2009 pre-dredge; 2011 & 2012 post-dredge

Feb. 2009 mudline

Oct. 2011 PDS

In-situ dredge prism core sample(PRE-dredge)

68.9226

156

91 10396 97 112

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

Apr. 2012 surface 8875 98

86 88

8987.1

77.2DredgePrism

Zinc Concentrations

Sample

PRE-DREDGE (Core)POST-DREDGE

(Grab) Zinc Screening

LevelDredge Prism

Sloughing Material

In-Situ PDS

Oct. 2011

Apr. 2012

Average 84.4 79.1 150.3 99.8 87 130 ppm

Zinc SL = 130 ppm

VC-02 VC-04

VC-06

<7.2

<12<12-36

-32

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD) VC-05

VC-01 VC-03

Downstream End (RM 2.1) Upstream End (RM 2.3)

PCBs: WILLAMETTE R., POST OFFICE BAR – 2009 pre-dredge

Feb. 2009 mudline

Oct. 2011 PDS

In-situ dredge prism core sample(PRE-dredge)

<7.4154

79

In-situ PDS core sample(PRE-dredge)

<1256

<12DredgePrism

PCBs SL = 60 ppb

VC-02 VC-04

VC-06

PCBs Concentrations

Sample

PRE-DREDGE (Core) PCB Screening

LevelDredge Prism

Sloughing Material

In-Situ PDS

Average 22.7 ND 78.9 60 ppb

<7.2

<12<12-36

-32

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD) VC-05

VC-01 VC-03

BC-01 BC-02BC-03 BC-04 BC-05

Downstream End (RM 2.1) Upstream End (RM 2.3)

PCBs: WILLAMETTE R., POST OFFICE BAR – 2009 pre-dredge; 2011 post-dredge

Feb. 2009 mudline

Oct. 2011 PDS

In-situ dredge prism core sample(PRE-dredge)

<7.4154

79

16 <9.8<9.6 <10 39

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

<1256

<12DredgePrism

PCBs SL = 60 ppb

VC-02 VC-04

VC-06

PCBs Concentrations

Sample

PRE-DREDGE (Core)POST-DREDGE

(Grab) PCB Screening

LevelDredge Prism

Sloughing Material

In-Situ PDS Oct. 2011

Average 22.7 ND 78.9 13.9 60 ppb

<7.2

<12<12-36

-32

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD) VC-05

VC-01 VC-03

BC-01 BC-02BC-03 BC-04 BC-05

Downstream End (RM 2.1) Upstream End (RM 2.3)

PCBs: WILLAMETTE R., POST OFFICE BAR – 2009 pre-dredge; 2011 & 2012 post-dredge

Feb. 2009 mudline

Oct. 2011 PDS

In-situ dredge prism core sample(PRE-dredge)

<7.4154

79

16 <9.8<9.6 <10 39

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

Apr. 2012 surface <9.7<9.9 <9.8

<9.7 <9.7

<1256

<12DredgePrism

PCBs Concentrations

Sample

PRE-DREDGE (Core)POST-DREDGE

(Grab) PCB Screening

LevelDredge Prism

Sloughing Material

In-Situ PDS Oct. 2011

Apr. 2012

Average 22.7 ND 78.9 13.9 ND 60 ppb

PCBs SL = 60 ppb

VC-02 VC-04

VC-06

Port of PortlandTerminal 2, Berth 205

DETAILS• Location: Willamette River, RM 10 • Volume: ~10,000 cy (project total 12,424 cy)• Depth: Dredged to -37 feet CRD

(plus 2 feet overdepth allowance) • Disposal: Upland, West Hayden Island

Placement Site • Project completed in July/Aug. 2008

PORTLAND, OR

VANCOUVER, WAColumbia R.

Willam

ette R.

N

2 4 60miles

Port of PortlandTerminal 2

DEHP: PORT OF PORTLAND, TERMINAL 2 – January 2008 pre-dredge

-29

-38

-26

-27

-36

-35

-34

-33

-32

-31

-30

-37

-28

Dep

th (f

eet C

RD)

Downstream Upstream

Aug. 2008 PDS

DEHP SL = 220 ppb

-39

C-5

130 240

C-3

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

DredgePrism

Jan. 2008 mudline

100 (dredge prism

composite)

DEHP Concentrations

Sample

PRE-DREDGE (Core)

DEHP Screening Level

Dredge Prism

In-Situ PDS

Result 100 240 220 ppb

DEHP: PORT OF PORTLAND, TERMINAL 2 – January 2008 pre-dredge; August 2008 post-dredge

-29

-38

-26

-27

-36

-35

-34

-33

-32

-31

-30

-37

-28

Dep

th (f

eet C

RD)

Downstream Upstream

Aug. 2008 PDS

DEHP SL = 220 ppb

-39

100

C-5

130 240

C-3

DEHP Concentrations

Sample

PRE-DREDGE (Core)

POST-DREDGE (Grab)

DEHP Screening Level

Dredge Prism

In-Situ PDS August 2008

Result 100 240 100 220 ppb

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

DredgePrism

Jan. 2008 mudline

100 (dredge prism

composite)

PORTLAND, OR

VANCOUVER, WA

Columbia R.

Willam

ette R.

Port of PortlandTerminal 5

N

2 4 60miles

Port of PortlandTerminal 5, Berth 501

DETAILS• Location: Willamette River, RM 1-2• Volume: 12,246 cy (project total 25,000 cy)• Depth: Dredged to -43 feet CRD

(plus 3 feet overdepth allowance) • Disposal: Upland, West Hayden Island

Placement Site • Project completed in July/Aug. 2010

ZINC: PORT OF PORTLAND, TERMINAL 5 – 2008 pre-dredge

-36

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD)

Downstream Upstream

Jun. 2007 mudline

July 2010 PDS

Zinc SL = 130 ppm

-46

C-7

177

126

C-12

74

85

268

197

C-6

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

DredgePrism

Zinc Concentrations

Sample

PRE-DREDGE (Core) Zinc Screening

LevelDredge Prism In-Situ PDSAverage 156 153 130 ppm

ZINC: PORT OF PORTLAND, TERMINAL 5 – 2008 pre-dredge; 2010 post-dredge

-36

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD)

Downstream Upstream

Jun. 2007 mudline

July 2010 PDS

Zinc SL = 130 ppm

-46

98167 116

C-7

177

126

C-12

74

85

268

197

C-6

C-7C-12 C-6

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

DredgePrism

Zinc Concentrations

Sample

PRE-DREDGE (Core) POST-DREDGE (Grab) Zinc Screening

LevelDredge Prism In-Situ PDS July 2010Average 156 153 127 130 ppm

ZINC: PORT OF PORTLAND, TERMINAL 5 – 2008 pre-dredge; 2010 & 2011 post-dredge

-36

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD)

Downstream Upstream

Jun. 2007 mudline

July 2010 PDS

Zinc SL = 130 ppm

-46

98167 116

Aug. 2011 surface

C-7

177

126

C-12

74

85

268

197

C-6

C-7

160

C-12

93C-6

120

Zinc Concentrations

Sample

PRE-DREDGE (Core) POST-DREDGE (Grab) Zinc Screening

LevelDredge Prism In-Situ PDS July 2010 Aug. 2011Average 156 153 127 124 130 ppm

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

DredgePrism

PCBs: PORT OF PORTLAND, TERMINAL 5 – 2008 pre-dredge

-36

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD)

Downstream Upstream

Jun. 2007 mudline

July 2010 surface

PCBs SL = 60 ppb

-46

C-7

34

47

410

38

C-6C-12

<3.9

22

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

DredgePrism

PCBs Data Summary

Sample

PRE-DREDGE (Core) PCB Screening

LevelDredge Prism In-Situ PDS

Average 149 36 60 ppb

PCBs: PORT OF PORTLAND, TERMINAL 5 – 2008 pre-dredge; 2010 post-dredge

-36

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD)

Downstream Upstream

Jun. 2007 mudline

July 2010 surface

PCBs SL = 60 ppb

-46

2825.337

C-7

34

47

410

38

C-6C-12

<3.9

22

C-7C-12 C-6

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

DredgePrism

PCBs Data Summary

Sample

PRE-DREDGE (Core) POST-DREDGE (Grab) PCB Screening

LevelDredge Prism In-Situ PDS July 2010

Average 149 36 30 60 ppb

PCBs: PORT OF PORTLAND, TERMINAL 5 – 2008 pre-dredge; 2010 & 2011 post-dredge

-36

-45

-33

-34

-43

-42

-41

-40

-39

-38

-37

-44

-35

Dep

th (f

eet C

RD)

Downstream Upstream

Jun. 2007 mudline

July 2010 surface

PCBs SL = 60 ppb

-46

2825.337

Aug. 2011 surface

C-7

34

47

410

38

C-6C-12

<3.9

22

C-7

<3.8

C-12

<3.9C-6

9.6

PCBs Data Summary

Sample

PRE-DREDGE (Core) POST-DREDGE (Grab) PCB Screening

LevelDredge Prism In-Situ PDS July 2010

Aug. 2011

Average 149 36 30 4.0 60 ppb

In-situ dredge prism core sample(PRE-dredge)

In-situ PDS core sample(PRE-dredge)

Surface grab sample(POST-dredge)

DredgePrism

What might account for differences between in-situ cores and PDS grabs?Fallback is a realityMixing happens: physical mixing during

dredgingnatural river processes, marine traffic

Side slope sloughingKnown rates of deposition: 4” to 6” year

accumulation

PDS

Regulatory requirements for the PDS(based on pre-dredge core sampling)BEFORE DREDGINGBioassays on pre-dredge core samplesBenthic invertebrate studyAFTER DREDGINGPDS sediment samplingMonitored natural recovery

Additional sediment samplingBathymetric surveysAdditional benthic invertebrate studies

OR

OVERDREDGE and cover with sand

ConclusionsThe in-situ PDS core sample generally over-

predicted the post-dredge condition Depending on site conditions and patterns of

contamination, the in-situ PDS sample may under-predict the post-dredge condition

When available, consider historic information and knowledge of site conditions to help predict PDS chemistry and potentially reduce sampling burden:

CPDS = ƒ[cin-situ core, cDP(mixed&fallback), cside slope, cdeposition]

ConclusionsAgencies and the regulated community should use these findings to inform risk-based regulatory decision making for dredging projects in the Portland Harbor

Future WorkExamine additional paired in-situ core and PDS grab samples to improve risk-based decision making in the Portland Harbor

Questions?