St. Clair River Area of Concern Engineering and Design Plan for - PowerPoint PPT Presentation

St. Clair River Area of Concern Engineering and Design Plan for Management of Contaminated Sediment Mike Moroney, Project Manager St. Clair Region Conservation Authority

Overview Background information on the St. Clair River Area of Concern Efforts to date to address mercury contaminated sediment in the three priority areas of the St. Clair River Outcome of the assessment of the most recent sediment, worm, and fish data Work planned for the engineering and design plan phase 2

Cooperation on the Great Lakes Boundary Waters Treaty (1909) Canada – Canada Canada-Ontario Ontario International U.S. Joint Commission Great Lakes Federal Water Canada-Ontario Great Great Lakes Quality Agreement Lakes Program Agreement Strategy 3

Great Lakes Areas of Concern • The St. Clair River is one of the Areas of Concern (AOC) established by the Great Lakes Water Agreement (GLWQA) • Under both the GLWQA and the Canada-Ontario Agreement key actions are identified for the clean-up of AOCs • Management of remaining mercury contaminated sediments within the St. Clair River AOC is one of the key projects in order to delist it as a Great Lakes AOC 4

St. Clair River Area of Concern Significant Accomplishments to Date: • Over $75 million has been invested in combined sewer overflow remediation by the City of Sarnia • $115 million dollars in ongoing industrial wastewater improvements over the past 10 years • $35 million to upgrade the Sarnia, Corunna and Courtright Sewage Treatment Plants • On-going shoreline softening effort (approximately $3 million to date) • Over 161 hectares (400 acres) of valuable wetland habitat restored or enhanced within the AOC 5 5

History of Sediments in the St. Clair River 1950s – most of river on 1957 1968 1977 1985 2000 shores impaired or degraded 2000 – recovery This graphic represents apparent but three a band of sediment extending from the priority areas identified Canadian shoreline. for further study based on benthic community studies 2005 – Initial clean up of three remaining priority areas 6

St. Clair River Sediment Management Project Overview • 2005 – A clean-up of contaminated sediment in the river located adjacent to the Dow Canada property was completed. This clean-up was for a number of different contaminants including mercury. • 2007 - A sediment technical team was established to develop a sediment management strategy for the remaining contaminated sediments. This team included Environment and Climate Change Canada, Ministry of the Environment Conservation and Parks, Sarnia Lambton Environmental Association, St. Clair Region Conservation Authority, Walpole Island First Nation and Aamjiwnaang First Nation. • 2009 – Sediment assessment of three remaining priority areas completed. 7

Remaining Priority Areas for Sediment Management Priority Area 1 at Suncor Docks Priority Area 2 at Shell Docks Priority Area 3 at Guthrie Park Stag Island Corunna 8

St. Clair River Priority Areas Sediment Assessment 2009 • Used the Canada-Ontario Decision-Making Framework For the Assessment of Great Lakes Contaminated Sediment. • Used four lines of evidence: • Sediment Chemistry • Sediment Toxicity • Benthic Community Structure • Biomagnification Potential • Results showed high mercury concentrations and risk of biomagnification in fish Sediment Management Goals: • Control this source as it contributes to downstream sites • Promote local risk reduction • Contaminant mass removal/isolation 9

St. Clair River Sediment Management Options 2013 – Sediment Management Options report was completed and extensive community engagement conducted on the options. • Supporting work included Geophysical, Geochemical, and Geotechnical studies. • Short listed conceptual designs were developed, these included; Hydraulic dredging (vacuuming of sediment and o water) Blended option (hydraulic dredging and thin-layer o capping) Isolation capping o Endorsement for Hydraulic dredging was received from: • Technical Team, o St. Clair River Canadian Remedial Action Plan o Implementation Committee, St. Clair River Bi-national Public Advisory Council, o Aamjiwnaang First Nation and Walpole Island First o Nation. 10

St. Clair River Sediment Management Data Review 2016 – A technical team was formed to review data from three priority areas to review the toxicity reference value to determine risk to fish, and to look at implementation issues based on different management actions Integrate review Technical findings into working updated group formed conceptual site models Consensus on Sediment management Review scope existing and new data for the priority areas 11

New Data and Analyses • MECP collected sediment and worm samples in 2010 and 2011 within the priority areas • MECP/MNRF also collected fish samples in 2015 in the upper, middle, and lower reaches of the St. Clair River • The new dataset enabled the technical team to recalculate the potential accumulation of mercury from sediment to worms to fish • And then predict the concentration of mercury in sediment that would result in concentrations in fish below levels of concern in fish residing in the priority areas. 12

Upper St Clair River 2015 Fish Sampling 1 Locations 2 Priority Areas In Upper 3 and Middle Middle St Clair River Reaches of St Clair River Michigan Ontario 13

Sediment Data Water • Evaluated top 15 cm because surface sediment is more important than deep sediment for biological exposure • Mercury in deep sediment is not available to biota and unlikely to be disturbed Surface Sediment Mixing Deep Sediment 14

Mercury Concentrations in Surface Sediment Area 1 Area 2 Area 3 15

What Levels of Mercury in Fish are Safe for Fish ? • Considered two protective concentrations (i.e., toxicity reference values or TRVs) for mercury in fish – 0.2 mg/kg (Beckvar et al. 2005) – 0.77 mg/kg (Fuchsman et al. 2016) • The higher value was based on review of the same studies included in Beckvar et al. (2005) as well as more recent studies and data from field investigations • For purpose of this evaluation, the focus was on 0.2 mg/kg in fish 16

2015 Fish Data from Upper and Middle Reaches • Mercury concentrations in fish were generally low Redhorse Sucker • All but two species had average concentrations < 0.2 mg/kg on a whole body basis • Freshwater Drum and Yellow Perch had slightly higher average concentrations but they are migratory fish with other potential Freshwater Drum sources of mercury exposure Yellow Perch 17

Predicting Fish Mercury from Sediment Mercury • Objective = Identify the mercury concentration in sediment that is protective of fish • Calculated mathematical relationship between – Sediment and worms – Worms and fish • Based on new and historical data Sediment Worms Redhorse sucker 18

Sediment to Worms • First, the technical team predicted mercury in worms based on mercury concentration in sediment • Based on the mathematical relationship within the 2010/2011 paired worm and sediment data 19

Worms to Fish = Biomagnification Factor • Then, the team predicted mercury in fish based on predicted mercury concentration in worms • Calculated two biomagnification = BMF factors (BMFs) based on new data and on new + historical data • Results were similar and both BMFs were used in the analysis 20

Sediment to Fish • The team’s analyses predict that an average mercury concentration in sediment of 3 mg/kg Fish will result in an average concentration in fish of 0.1 – 0.2 mg/kg Mercury • Fish are exposed to average concentrations in 0.1 – 0.2 worms and sediment because they feed over a mg/kg large area 3 mg/kg BMF Sediment Worms Redhorse sucker 21

Identification of Action Level in Sediment • Action level is the concentration above which remediation will take place • The technical team evaluated a range of action levels and calculated what the average mercury concentration would be after remediating sediment greater than the action level and replacing with a layer of clean backfill • An action level of 10 mg/kg was selected because it results in an average mercury concentration in sediment that is protective of fish Sediment Mercury 3 mg/kg Action Level Sediment 10 mg/kg 22

Current Mercury Concentrations in Surface Sediment Area 1 Area 2 Area 3 23

Remove Sediment with Mercury > 10 mg/kg Replace with Clean Backfill Area 1 Area 2 Area 3 24

Action Level of 10 mg/kg in Sediment Predicted to Result in Fish Mercury of 0.1 – 0.2 mg/kg Sediment Mercury Fish Action Level Mercury 0.1 – 0.2 10 mg/kg mg/kg 3 mg/kg BMF Sediment Worms Redhorse sucker 25

Outcome of Re-evaluation • Remove sediment via hydraulic dredging or, in targeted areas, mechanical dredging where mercury concentrations in surface sediment exceed 10 mg/kg • Replace with a layer of clean backfill so average mercury in each priority area is 3 mg/kg • In areas inaccessible for dredging, consider capping to cover contamination • Details will be refined based on additional data collection during detailed engineering design of the remedy 26