aoc sediment update_part 1
DESCRIPTION
2012 update on sediment management at Areas of Concern across the Great Lakes. Excellent information about the north harbour section of Thunder Bay, OntarioTRANSCRIPT
Contaminated Sediment
Management
Roger Santiago – Environment Canada
2012 RAP Implementation Workshop Getting the Job Done !
Priority Sediment Remediation Sites
Contaminated Site Overview • Thunder Bay N. Harbour – Hg, Organic material – 350,000 m3 • Peninsula Harbour – Hg, PCBs – 256,000 m2 • St. Marys River – PAHs – 50,000 m3 (app.) • St. Clair River – Hg – 61,000 m3 • Hamilton Harbour – PAHs, metals – 675,000 m3 • Niagara River – PCBs – 20,000 m3 (MoNR)
Conceptual Implementation Schedule and Estimated Costs (in $1000)
Implementation estimate based on sediment risk assessment
Implementation estimate based on SMO
Implementation estimate based on Engineering Design
AOCs 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 Total
TB $21,600 $21,600 $21,600 $65,000
PH $7,300 $7,300
SM $5,000 $5,000 $10,000
SC $8,750 $8,750 $17,500
Total Cost (without RR)
$99,800
RR (to 2022) $105,000
TOTAL COST (with RR)
$204,800
Stages of Sediment Projects (7) Post Construction
(6) During Construction
(5) Tender Award
(4) Detailed Engineering Design
(3) Preliminary Engineering Design
(2) Conceptual Design
(1) Sediment Assessment
Sediment Remediation Challenges Cost Estimate Increases
Increasing Certainty in Estimate
Sediment Remediation Challenges
• Ability to secure1/3 local funding – Depressed local markets – Local industry bankruptcy issues – Lack of interest/responsibility
• Project lead (Contracting Authority) • Future Liability for in-situ remediation • Site Access/Ownership Issues • Coordinating stakeholder (funding parties) interest • Cost overruns during implementation • Cost estimate increases
Science Challenges to GL Sediment Remediation
Great Lakes Areas of Concern • Lack of Chemical Guidelines for COC in Sediment • Absence of confirmed dose-response information for COC • Development of innovative techniques to identify and manage debris • Develop and implement feasible pore water sampling methods • Develop approaches to reduce uncertainty related to identification of
contamination layer • Understanding the dynamics of natural recovery and recovery post
remediation and the ability to to predict through modelling when short and long term goals will be achieved
• Addressing temporal variability in benthic community structure related to stressors such as invasive species, climate change, change in abundance of native taxa, watershed disturbance etc.
Thunder Bay North Harbour Sediment Management
RAP Workshop February 8, 2012
Thunder Bay Area of Concern
Thunder Bay Project Site
Thunder Bay North Harbour - Contaminated Sediment Management
Contamination Overview
Contaminated Sediment
Mercury Concentrations in Surficial Sediments
Mercury Concentrations at Depth
Enriched Organic Sediment
Toxicity and Biomagnification
• Monitored natural recovery
• Capping (sand or reactive cap)
• On-site confined disposal facility
• Dredging with disposal at an off-site confined disposal facility
• Dredging with upland disposal
Conceptual Sediment Management Schedule
Additional Studies in support of SMO – 2012 Decision on preferred SMO – 2013 Engineering Design/ EA – 2014-2015 Construction (assume 2 to 5 years) – 2016-20?? Long-term monitoring – 15 years
Peninsula Harbour Sediment Management
RAP Workshop February 8, 2012
Peninsula Harbour Area of Concern
Project Description • Elevated levels of Mercury and PCBs are
present in sediment in Peninsula Harbour with the highest concentration found in Jellicoe Cove.
• Contaminated sediment in Jellicoe Cove is acting as a source of mercury and PCBs for the rest of the PH and posing risk to biota.
• Results of Risk Assessment indicated that sediment management action is required
Peninsula Harbour Shoreline 2007
1. Sediment Sampling - Chemistry
Surface concentrations of mercury average 7 ppm, which is 3.5X higher than the guideline.
Average subsurface concentrations are 3X higher than average surface concentrations.
Sediment Core Sample
2. In-Situ Tracer Measurements (6/05-7/06)
• Divers applied a tracer (mineral) in slurry form to measure sediment mixing rate
• Cores were initially collected to determine background levels
• One year later, sampling revealed mixing of surface sediment to 8 cm
Conclusion: Mixing generally occurs in top 8 cm of sediment
3a. Rotating Circular Flume Tests
• Tells us how the sediment resists bottom currents
• Large diameter sediment cores collected and tested for erosional resistance in a rotating circular flume
Conclusion: Strong bottom currents are required to mobilize sediment that is deeper than 5 cm
Objective: Measure strength of bottom current needed to mobilize sediment
3b. In Situ Flume Experiments (9/07)
• At 4 sites, flume was deployed in Jellicoe Cove to measure erosional resistance of surface sediments
• Compared to subsurface sediment, surface fines erode with weaker bottom currents
Conclusion: Surface sediment (1-5 cm) erodes with bottom currents 10x weaker than for deeper sediment
Objective: Measure strength of bottom current needed to mobilize sediment
4. Wave Climate (6/05-7/06 and 11/06-5/07)
• Bottom currents measured by a current meter (MAVS-3)
• Year-round • 6 months in high energy
season
Objective: Measure bottom currents in Jellicoe Cove
Conclusion: Currents strong enough to move surface sediment are common. Currents strong enough to move subsurface sediment are rare.
Conclusions
1. Thin layer capping will help manage the surface sediment that is currently mobile.
2. Dredging is not required to address subsurface sediment mobility.
Sediment Management Option
• Thin layer capping was selected to manage the contaminated sediments.
• Area with > 3 ppm Hg will be covered with 15 to 20 cm of clean sand (approx. 20 hectares – about 40 football fields)
• Area with >0.34 ppm PCB will be covered with 15 to 20 cm of clean sand (approx. 5 hectares – about 5 football fields)
Thin-Layer Capping
Sediment Profile Imaging Camera
Thin layer cap
Capped sediment
EA Findings
Results of the assessment indicate: • DFO Authorization under section 35(2) of the Fisheries Act is
required. • Town of Marathon may be subjected to truck traffic and noise
during the construction period • AECOM confirmed that local pits in the Marathon area have
suitable cap material. • There are no additional regulatory restrictions on dredging post
cap to allow access to larger vessels • The MPI water intake will be protected during construction.
Sediment Remediation Schedule
MERX Tender Posting – March 2012 Tender Award – April 2012 Mobilization – May 2012 Pilot Scale Demonstration – June 2012 Production Capping – June – Aug 2012 Demobilization – September 2012 Post Engineering Assessment 2013 Long Term Monitoring – 2014
Long Term Monitoring Plan Year Years after Cap Monitoring Component Survey Period 2013 1 Cap Movement and Submerged Aquatic Vegetation fall
Cap Thickness Study summer/fall
2015 3 Cap Movement and Submerged Aquatic Vegetation fall
2017 5 Cap Movement and Submerged Aquatic Vegetation fall Benthic Community/Benthic Tissue/Sediment Chemistry fall Fish Tissue Survey last week of June to end of August
2022 10 Cap Movement Survey fall Benthic Community/Benthic Tissue/Sediment Chemistry fall Fish Tissue Survey last week of June to end of August
2027 15 Cap Movement Survey fall Benthic Community/Benthic Tissue/Sediment Chemistry fall Fish Tissue Survey last week of June to end of August
2032 20 Cap Movement Survey fall Benthic Community/Benthic Tissue/Sediment Chemistry fall Fish Tissue Survey last week of June to end of August
St. Clair River – Sediment Management
RAP Workshop February 8, 2012
St. Clair River
St. Clair River – Contaminated Sediment Management
St. Clair River AOC
St. Clair River Sediment Remediation Project
• Eddy Pump hydraulic dredge used to remove 13,000 m3 contaminated sediment (Hg, and organics) with physical dewatering and anaerobic bioremediation (biopile) and on-site disposal
Dow River Cleanup
Dow River Cleanup
Habitat Restoration - 2005
• Restore the area to a state of granular sediment.
• Enhance fisheries habitat and promote benthic macroinvertebrate recolonization.
Priority Zones for Sediment Management
Three priority zones for management;
1. Volume near Suncor dock, (25,700m3)
2. Volume near Shell dock (5,500m3), and
3. Volume near Guthrie Park (3,750m3)
Suncor
Guthrie Park
Shell
These areas represent depositional areas downstream from the original source.
St. Clair River Priority Areas
1. Sediment Chemistry • 61% of sediment samples more than
2 mg/kg Hg (Provincial SEL) • Hg in buried sediment up to 5 times
higher than surface sediment in some places
3. Sediment Toxicity • No strong evidence of toxicity to Hg
5. Changes to Benthic Community • No strong evidence of community
changes due to Hg compared to reference sites
7. Potential for Biomagnification • Negligible risk to wildlife that eat fish • Risks to some fish species • Priority Areas identified based on
risk to fish
Management Goals Removal of Hg-contaminated sediment:
1. as a source to downstream sites 2. to promote local risk reduction 3. for contaminant mass removal