Sediment Dredging at Superfund Megasites ... - Emsus.com

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Differences in Site Conditions Influence ResultsGrasse River, NY• Contaminated sedimentsunderlain by bedrock and hardpan(not “dredgeable”).• River channel deepened byblasting contains unevensubstrate (ridges, gulleys,scattered boulders) beneathsediments that make dredgeaccess difficult.• Difficult to characterize the depthof contaminated sediment usingstandard characterizationtechniques due to heterogeneity ofunderlying material.• Debris present; removed prior todredging operations.Head of Hylebos, WA• Contaminated sediments underlain bydense, sandy material (“dredgeable”).• Former tidal flat has relativelyfeatureless and homogeneoussubstrate underlying contaminatedsediments.• Relatively easy to characterize thedepth and extent of contaminationbased on historic channel depth andvisual differences betweencontaminated and clean sediment.• Debris present; removed prior todredging operations.16
Manistique River and Harbor•Removal was initially expected totake 3 seasons and remove 104,000cy – project took 6 seasons andremoved approximately 190,000 cy.•Issues encountered in characterizingthe extent of contaminated sedimentand completely removing sedimentresiding over fractured bedrock.•Cleanup level: average PCBconcentration of 10 mg/kg throughoutthe sediment column within the AOC.•Post-dredging average PCBconcentrations (top foot) throughoutthe site were 9.0 mg/kg (2000) and7.3 mg/kg (2001).
Page 1 and 2: Sediment Dredging atSuperfund Megas
Page 3 and 4: Reviewers of the Final ReportReview
Page 5 and 6: Outline• Introduction• Evaluati
Page 7 and 8: Committee’s Evaluation ofDredging
Page 9 and 10: Evaluation of Dredging Effectivenes
Page 15: Range of Experiences at Dredging Pr
Page 21 and 22: Monitoring at Sediment MegasitesREC
Page 23: Improving Future Decision-Making•

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