Challenges of Performing Contaminated Sediment Remediation and Restoration in China and Taiwan

Brian J. Mastin, Ph.D. Dave Renfrew

Jerry ChenSamuel Wu Ph.D.

Dredging 2012 – San Diego, CAOctober 23, 2012

SOUTHERN RESEARCH INSTITUTELegendary Discoveries. Leading Innovation.

Overview

• Remediation/Restoration • Case study – An-shun Remediation Project• Case study – Xiawangang River Remediation Project

Sediment management projects conducted in isolation of watershed

objectives are not typically sustainable

Integrated Sustainable Sediment Management

Phased Approach to Sediment Remediation & Restoration Implementation

Source Control & Define Objectives

Sampling & Analysis (RI)

Bench-scale Feasibility (FS)

Pilot-scale Implementation

Operations & Maintenance – Sustainability

Full-scale Implementation

Design & Engineering

• Identification of Sources• Best Management Practices• Prevent Recontamination

• Nature, Magnitude & Extent • Goodness-of-fit• Scalability • Performance (effectiveness & efficiency) • 2o & 3o Treatment• Timeline

• 90% complete• Incorporate contractor suggestions

• Proof of Concept • Remediation, Restoration, Rehabilitation

Risk Management Goals and Objectives for Successful Remediation

Typically use several sediment quality metrics to determine the contaminants of concern and biological risks for each Site based on established benchmarks & multiple lines of evidence (weight of evidence approach).

1. Analytical endpoints and thresholds2. Toxicity to sentinel test species3. Benthic community assessment (simultaneously evaluated with

habitat conditions)4. Biological tissue concentrations (i.e., bioaccumulation in

benthic macroinvertebrates and/or fish species)

An-shun Remediation Project

xian-gong community

Lu-Er community

Remediation Site

竹筏

港

溪

鹿

耳

門

溪

灣海峽

Taiwan Strait

Tainan City

Taiwan

Preliminary Site Investigation

Sediment: < 1,400 mg/kg Hg Contamination above soil

control standard to > 90-cm

Sediment: < 1,400 mg/kg Hg Contamination above soil

control standard to > 90-cm

SEAWATER POND

ALKALI-CHLORINE

PLANT

PENTACHLORO- PHENOL PLANT

Hot Spot

Hot Spot

Hot Spot

Weirs/Outfalls

Pond A

Pond B

Sediment/soil control standardsHg: 10 mg/kg Total Hg

Dioxin: 500 ng-L-TEQ/kg

Objectives

1) Perform turn-key remediation of mercury (Hg) and dioxin contaminated

sediment in Pond B.

2) Incorporate separation of “clean” sand for beneficial reuse on site.

Sediment Management Plan

Sediment Characterization

Sediment Excavation

Hydraulic dredging

Sand Separation – hydrocyclones

Soil washing

WWTPVerification & Additional Remediatione.g., capping, backfilling Effluent

“Clean” Sand for

Beneficial Reuse

Contaminated Fines: Dewatered & Consolidated

Remedial Investigation Results

Pond B

Pond A

Contaminated SedimentPond A: ~125,000-m3

Pond B: 116,400-m3

Xiawangang River Remediation Project Zhuzhou City, China

Objective

Perform a sediment remediation and environmental rehabilitation of 4-km of the Xiawangang River in order to decrease the

human health and environmental risks associated with metals-contaminated (e.g., Cd,

Hg, As, and Pb) sediment and water.

Xiawangang River Overview

WESTON Proposed Section

Surface Area(meters2)

Total Volume Sediment (meters3)

Total Volume By Particle Size (meters3)

Gravel Sand Silt Clay

1 4,796 5,584 1,464 3,923 713 248

2 1,707 2,049 537 1,439 261 91

3 2,744 3,293 858 2,286 443 147

4 2,697 2,130 441 856 797 106

5 1,001 2,002 414 805 749 100

6 5,489 6,077 1,251 2,439 2,283 308

7 5,209 8,200 1,096 2,944 3,912 760

8 4,014 6,229 832 2,236 2,971 577

9 1,096 1,193 223 305 721 80

10 134 134 25 34 81 9

TOTAL 28,887 36,891 7,141 17,267 12,930 2,427

Metal-contamination

Weston River

Section

Mass of Metal within Each Section (metric tons)

Cadmium (Cd)

Chromium (Cr)

Copper (Cu)

Lead (Pb)

Mercury (Hg)

Nickel (Ni)

Arsenic (As)

Zinc (Zn)

1 1.552 0.991 10.598 12.720 0.041 0.554 1.624 86.173

2 0.570 0.363 3.889 4.667 0.015 0.203 0.596 31.616

3 0.916 0.584 6.251 7.502 0.024 0.327 0.958 50.822

4 0.592 0.378 4.043 4.852 0.016 0.211 0.619 32.870

5 0.557 0.355 3.800 4.561 0.015 0.199 0.582 30.895

6 1.689 1.078 11.535 13.844 0.044 0.603 1.767 93.784

7 2.280 1.455 15.564 18.680 0.060 0.813 2.385 126.547

8 1.732 1.105 11.823 14.190 0.045 0.618 1.811 96.130

9 0.332 0.212 2.264 2.717 0.009 0.118 0.347 18.408

10 0.037 0.024 0.254 0.305 0.001 0.013 0.039 2.065

TOTAL 10.26 6.55 70.02 84.04 0.27 3.66 10.73 569.31

Note: Results represent the volume of sediment from each River section multiplied by the 2011 average sediment concentration (n=29) for the 20-cm depth horizon and the 100-cm depth horizon.

Challenges - Site Access & Equipment Selection

10 Remediation Plans

Schedule

Section Transect(m)

In situSediment Volume

(m3)

Total Mass*(dry metric tons)

S/S Volume**(m3)

Timeline to Completion+

(days)

ConstructionSequence

1 3070 - 4060 5,584 12,696 4,120 28 2

2 2840 - 3070 1,790 4,068 1,321 9 3

3 2260 – 2840 5,436 11,948 4,120 54 4

4 2020 – 2260 246 508 195 6 3

5 1920 – 2020 2,002 4,136 1,588 15 4

6 1440 – 1920 6,077 12,562 4,826 30 3

7 780 – 1440 8,200 17,424 7,104 41 2

8 230 – 780 6,229 13,232 5,397 31 3

9 40 – 230 1,193 2,658 970 12 4

10 0 - 40 134 298 109 12 1

TOTALs 36,891 79,530 29,750 (59,500 mt)

95

Challenges to Remediation

• Extremely high contaminant concentrations

• Multiple exposure pathways

• The overall objectives and beneficial uses not defined

• Remediation and rehabilitation performance goals were not defined

• Limited in-channel footprint for sediment management

• Restricted access due to active industrial facilities, power lines,

pipelines, steep and unstable channel banks, railways and roads

• Incomplete performance expectations for bank stabilization and

source control

Additional Challenges

• Previously conducted remedial investigations and feasibility

studies were incomplete• “Ground-truthing” of project objectives and performing data

gap investigations was not performed

• No regional guidance on development of a Stormwater Management Plan

• No regional guidance on point and nonpoint source control

• No operation and monitoring component

• No risk-based effects guidance for this type of watershed

• Equipment availability

What other surprises?????

Thank you!!

Questions??

SOUTHERN RESEARCH INSTITUTELegendary Discoveries. Leading Innovation.

Brian J Mastin, PhD (mastin@southernresearch.org)

Dave Renfrew (dave.renfrew@westonsolutions.com)