Field testing of thin layer

capping with AC and

passive materials in

Norway

Espen Eek1, Amy Oen1, Gijs Breedveld1,

Magnus Sparrevik1, Morten Schaanning2

Bjørnar Beylich2, Kristoffer Næs2 Jonas

Gunnarsson3 and Gerard Cornelissen1

1Norwegian Geotechnical Institute

2Norwegian Institute for Water Research

3Stockholm University

Content

• Thin layer capping

• Methods used in the study of

thin layer capping

• Effetiveness

Clay+AC

Foto: Beylich, NIVA

Why thin layer capping?

•Remediation of large moderately contaminated areas •Less use of non-renewable resources •Less cost •Less secondary effects on the environment where remediation is done

?

Working principle of passive and active caps

Sediment

Diffusion layer

Bioturbation

Sediment

Bioturbation layer ? Passive Active

How will it work in the field

Partners in Opticap

Technical: Scientific:

Financial: Materials:

Methods used to study thin layer capping

Placement Effectiveness Secondary

effects

Modeling Placement from

barge

Diffusion through cap

layers

Life cycle

assessment (LCA)

Laboratory tests

Test of individual

mechanisms

Material properties Sorption and

diffusion studies

Leaching from

materials

Laboratory tests

multiple

mechanisms

(Boxcosm)

Influence of

Bioturbation on cap

properties

Bio-accumulation

and flux

Toxic effects of

capping materials

Field tests Cap thickness

measured in situ

Flux in situ and

accumulation in

organims

Ecological status

measured in testplots

Relevance and presision in different

methods

Laboratory

Boxcosm

Field studies

Laboratory

Boxcosm

Field studies

Relevance

Presision

Boxcosm tests, NIVAs research station, Solbergstrand

Sediment

Cap

SPMD

Water flow

Effectiveness of thin layer capping

Flux in boxcosm

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

OCS (73 950 pg) 59,5 % 46,8 % 37,6 % 3,9 % 0,1 % 0,0 %

HCBz (226 000 pg) 87,6 % 50,9 % 14,8 % 11,5 % 0,2 % 0,2 %

Sum PCDD/F (3002) 77,8 % 78,2 % 66,0 % 16,4 % 4,4 % 4,2 %

WHO-TEQ (276 pg) 85,1 % 84,1 % 63,4 % 16,7 % 3,6 % 2,7 %

Cl-5 LI/Cl-5 AC/Cl-5 Cl-30 AC/Cl-30 LDPE-bl

Clay 0,5 cm Clay/Lignin 0,5 cm

Clay/AC 0,5 cm

Clay 3 cm

Clay/AC 3 cm Blank

Reduced

concentration of

OCS, HCB and

dioksines i pore

water in bioturbation

layer (0-3 cm)

Control boxes

Cap efficiency >95% for 3 cm clay/AC

Model: RE = e-b√tykkelse

Dredging and mixing materials in a hopper dredger

Application at 30m depth by hopper dredger

Application at 100m depth using a separate pump on transport platform

Field testing of thin layer capping

Material mixing in hopper dredger

Suspended limestone slurry pumped out 5 – 10 m above the seabed

Grenlandfjord (30 m depth)

Clay Reference Clay+AC

Foto: Beylich, NIVA Foto: Beylich, NIVA Foto: Beylich, NIVA

www.opticap.no

Flux chambers with

infinite sink passive samplers

Exposed in 2 – 24 weeks

Flux of TBT, PAHs, PCBs and dioxins

from the seabed

Eek et al., Environmental Science & Technology 2010

Monitoring of effectiveness of the thin

layer capping in the field

Release of dioxins/furanes in flux chambers from

Grenlandfjord test plots

0

5

10

15

20

25

30

35

Month 1-7

Month 9-14

Month 14-20

Month 20-23

Month 1-7

Month 9-14

Month 14-20

Month 20-23

Month 1-7

Month 9-14

Month 14-20

Month 20-23

Month 1-7

Month 9-14

Month 14-20

Month 20-23

Month 1-7

Month 9-14

Month 14-20

Month 9-14

Month 14-20

Ormer-Ref Ormer-limestone Ormer-clay Ormer-AC Eidanger-Ref Eidanger-AC

Flu

x P

CD

D/F

(p

g T

EQ

m-2

d-1

)

Freely dissolved organic contaminants in

overlying water

Organic contaminants bound in the POM

Dioxines dissolved in water

Passive samplers made from Plastic material (POM)

Chemical analysis

Extraction

Calculation of freely

dissolved concentrations

Freely dissolved Dioxins in overlying

water at Grenlandfjord test plots

0

20

40

60

80

100

120

140

160

180

Mnd 1-7

Mnd 9-14

Mnd14-20

Mnd 1-7

Mnd 9-14

Mnd14-20

Mnd 9-14

Mnd14-20

Mnd 9-14

Mnd14-20

Mnd 9-14

Mnd14-20

Mnd 9-14

Mnd14-20

Ormer-Ref Ormer-limestone Ormer-clay Ormer-AC Eidanger-Ref Eidanger-AC

CW

PC

DD

/F (

pg

m-3

)

Freely dissolved TBT in overlying water

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

16,0

Before capping 1 mnth aftercapping

8 mnth aftercapping

12 mnth aftercapping

TB

T-c

on

cen

trati

on

in

wate

r (

ng

L-

1)

Test field capped with 5 cm limestone slurry

Test field capped with 5 cm AC-limestone slurry

Modelled vs measured Remediation effectiveness (RE)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

RE

me

asu

red

RE modeled

1:1 Flux in situ Flux boxcosm fra felt

Polycheat i boxcosm fra felt Snail boxcosm fra felt 2009 Snail boxcosm fra felt 2010

Cw POM Difusion only

Leire og kalkfeltene

AC-feltene

Flux and polycheats in boxcosm:

No effectiveness

Theoretical/measured diffusion only Generally good agrement found between modeled and measured efectiveness Effectivensess measured in boxcosms was lower than expected for passive materials

Model: RE = e-b√tykkelse

Conclusions

Placement of AC-mixed with clay resulted in well defined AC-layers

Important parameters like pore water concentrations sediment to

water release and overlying water concentrations can be

monitored in situ

Thin layer capping with or without AC can reduce the availability

with 50 – 95 %

Both cap thickness and active material content are important

Thanks !