Contaminated Sediment ManagementRoger Santiago – Environment Canada 2012 RAP Implementation Workshop Getting the Job Done !
Priority Sediment Remediation SitesContaminated 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 andEstimated 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 $21,600 $21,600 $21,600 $65,000 TB PH $7,300 $7,300 $5,000 $5,000 $10,000 SM SC $8,750 $8,750 $17,500Total Cost $99,800(without RR) $105,000RR (to 2022)TOTAL COST $204,800(with RR)
Sediment Remediation Challenges Cost Estimate IncreasesStages of Sediment Projects(7) Post Construction Increasing Certainty(6) During Construction in Estimate(5) Tender Award(4) Detailed Engineering Design(3) Preliminary Engineering Design(2) Conceptual Design(1) Sediment Assessment
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
• 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 ScheduleAdditional Studies in support of SMO – 2012Decision on preferred SMO – 2013Engineering Design/ EA – 2014-2015Construction (assume 2 to 5 years) – 2016-20??Long-term monitoring – 15 years
Peninsula Harbour Sediment Management RAP Workshop February 8, 2012
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 Sediment Core SampleSurface concentrations of mercury average7 ppm, which is 3.5X higher than theguideline.Average subsurface concentrations are 3Xhigher than average surface concentrations.
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 cmConclusion: Mixing generally occurs in top 8 cm ofsediment
3a. Rotating Circular Flume TestsObjective: Measure strength of bottom current needed to mobilizesediment• Tells us how the sediment resists bottom currents• Large diameter sediment cores collected and tested for erosional resistance in a rotating circular flumeConclusion: Strong bottom currents are required tomobilize sediment that is deeper than 5 cm
3b. In Situ Flume Experiments (9/07)Objective: Measure strength of bottom current needed to mobilizesediment • 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 currentsConclusion: Surface sediment (1-5 cm) erodes withbottom currents 10x weaker than for deeper sediment
4. Wave Climate (6/05-7/06 and 11/06-5/07)Objective: Measure bottom currents in Jellicoe Cove • Bottom currents measured by a current meter (MAVS-3) • Year-round • 6 months in high energy seasonConclusion: Currents strong enough to move surfacesediment are common. Currents strong enough to movesubsurface sediment are rare.
Conclusions1. 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 Thin layer cap Capped sediment Sediment Profile Imaging Camera
EA FindingsResults 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 ScheduleMERX Tender Posting – March 2012Tender Award – April 2012Mobilization – May 2012Pilot Scale Demonstration – June 2012Production Capping – June – Aug 2012Demobilization – September 2012Post Engineering Assessment 2013Long Term Monitoring – 2014
Long Term Monitoring PlanYear Years after Cap Monitoring Component Survey Period2013 1 Cap Movement and Submerged Aquatic Vegetation fall Cap Thickness Study summer/fall2015 3 Cap Movement and Submerged Aquatic Vegetation fall2017 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 August2022 10 Cap Movement Survey fall Benthic Community/Benthic Tissue/Sediment Chemistry fall Fish Tissue Survey last week of June to end of August2027 15 Cap Movement Survey fall Benthic Community/Benthic Tissue/Sediment Chemistry fall Fish Tissue Survey last week of June to end of August2032 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 –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
Habitat Restoration - 2005• Restore the area to a state of granular sediment.• Enhance fisheries habitat and promote benthic macroinvertebrate recolonization.
Priority Zones for Sediment ManagementSuncor Three priority zones for management; 1. Volume near Suncor dock, (25,700m3) 2. Volume near Shell dock (5,500m3), and Shell 3. Volume near Guthrie Park (3,750m3)GuthriePark These areas represent depositional areas downstream from the original source.
St. Clair River Priority Areas1. 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 places3. Sediment Toxicity • No strong evidence of toxicity to Hg5. Changes to Benthic Community • No strong evidence of community changes due to Hg compared to reference sites7. 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