LEAF Method Testing of MGP-impacted Sediments in Gowanus Canal

Transcription

1 LEAF Method Testing of MGP-impacted Sediments in Gowanus Canal RE3 Conference 2014 Jeff Gentry, P.E. Principal Technologist January 28, 2014

2 Gowanus Canal Superfund Site 1.8 mile long canal in Brooklyn, New York City Constructed in 1860 s Significant Constituent of Concern Sources Three MPG plants Many historic waterfront industries Two major combined sewer overflows Designated a Superfund Site in March 2010

3 Gowanus Canal: Past, Present and Future eveals_plans_for_700unit_colossus_on_the_canal.php Frequent industrial use of canal continues in Middle Canal Active redevelopment such as proposed 700- unit apartment

4 Coal Tar Upwelling Creates Visible Sheens

5 EPA Record of Decision Issued September 30,2013 In Situ Stabilization Remedy Component Estimated 600 feet in Remedial Target Area 1 in Upper Canal Estimated 2,700 feet in Remedial Target Area 2 in Middle Canal 5

6 Example Cross Section Elevation (feet NAVD88 Approximate) Elevation (feet NAVD88 Approximate) 10 ft 0 ft -10 ft -20 ft -30 ft -40 ft 10 ft 0 ft -10 ft -20 ft -30 ft -40 ft Existing Soft Sediment Native Sediments Post Implementation Stabilized Sediments Native Sediments Augers Barge Selected Remedy Summary Soft sediment removal ISS of 5 feet of native sediment in select areas Active capping 6

7 Field Sample Collection December 2012 NAPL up to 52% saturation 7

8 Objectives Sequester NAPL Migration and Reduce Dissolved Phase Impacts 8

9 Leaching Environmental Assessment Framework (LEAF) Methods Method 1313 Liquid-Solid Partitioning as a Function of Eluate ph using a Parallel Batch Procedure Method 1314 Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio (L/S) using an Up-flow Percolation Column Procedure Method 1315 Mass Transfer Rates in Monolithic and Compacted Granular Materials using a Semi-dynamic Tank Leaching Procedure Method 1316 Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio using a Parallel Batch Procedure 9

10 Gowanus LEAF Testing Overview Method 1312 (SPLP), used on native and stabilized sediment Method 1316 used on native and OC amended sediment Method 1315 used on stabilized sediment

11 1315 and 1316 What do they Simulate in the Canal? Elevation (feet NAVD88 Approximate) 10 ft 0 ft -10 ft -20 ft -30 ft -40 ft Equilibrium Release Native Sediment Groundwater flows through impacted sediment Mass Transfer Release Stabilized Sediment Majority of groundwater flows around stabilized sediment, Contaminants transfer from external surface area Use Test 1316 for Equilibrium Release Use 1315 for Mass Transfer Release 11

12 Native and OC Amended Sediment Test Process 12

13 Naphthalene (mg/kg dry) 1316 Result (Naphthalene Key COC) Raw Sediment vs. Raw Sediment + 1% OC Naphthalene Mass Released Raw Sediment Raw one-to-one slope A + 1% OC 1% OC one-to-one slope L/S Ratio (ml/g dry) Similar naphthalene concentrations for all L/S Ratio s One-to-one slope of curve characteristic of solubility controlled release (ITRC 2011) Addition of 1 percent oleophilic clay resulted in ~50 percent reduction 13

14 Semi-Dynamic Leaching-Mix Design Process 14

15 Unconfined Compressive Strength (psi) Hydraulic Conductivity (cm/sec) Hydraulic Conductivity Results 1.00E E E E-08 Raw Sediment Range of Stabilized Mixes 338A Raw Sediment ISS Mixes 338A Raw Sediment ISS Mixes Hydraulic conductivity measured (ASTM D5084) on undisturbed native sediment and test cylinders One to 2.5 orders of magnitude reduction achieved All mixes achieved test strength requirements 20 0 Raw Sediment Range of Stabilized Mixes 15

16 SPLP Concentration (mg/l) 7-Day SPLP results show no reductions Naphthalene - Raw Sediment Naphthalene - Stabilized Monoliths Raw Sediment Stabilized SPLP did not yield meaningful results that enable optimization of mix designs 16

17 1315 Test Modifications Method 1315 as written is not approved for organics Three modifications to the method were incorporated for organics Near zero headspace No filtration before eluate analysis Used polydimethylsiloxane (PDMS) liners in vessels PDMS addition was developed at Vanderbilt (published by EPRI) The PDMS liner acts as a VOC sink to: maintain low VOC concentrations in the water bath preserve the concentration gradient between the solidified materials and the water bath which is the driving force for mass transport 17

18 1315 Lab Process Using PDMS Liners 18

19 1315 Results Eluate and Effective Concentration Mass transfer stops Mass transfer rate reduced No reduction in mass transfer 19

20 Cumulative release (mg/m²) 1315 Results Naphthalene Cumulative Release slope indicates diffusion controlled mass transfer Time (days) H1 Mix(0% OC) H2 Mix(1% OC) H3 Mix (2% OC) H4 Mix(3% OC) H5 Mix(4% OC) slope=0.5 20

21 Diffusivity (cm^2/sec) 1315 Diffusivity Estimates 1.00E E E E results can be used to estimate diffusion coefficients 1.00E E-10 21

22 Combining 1316 and 1315 Results Reduction in mass released from 1%OC Order of magnitude reduction by S/S Native Sediments Stabilized Sediments 22

23 Oleophilic Clay Leaching Reduction vs. Cost 10% Portland Cement 91% Leaching Reduction $14/cy Reagent Cost 4% Oleophilic Clay 93% Leaching Reduction $165/cy Reagent Cost 23

24 Conclusions Test Results Show Potential Effectiveness of ISS in Canal Migrating NAPL can be sequestered Leaching can be greatly reduced Use of the 1316 and 1315 test methods showed that stabilization of the canal sediments would be effective in significantly reducing the transport of contaminants to surface water LEAF methods were shown to be more reliable for testing the leaching from stabilized sediment than the traditional SPLP method Use of the new LEAF test methods enables us to assess that the use of additives such as oleophilic clay and carbon may not be justified 24

25 What Did We Learn about PDMS Liners? Using PDMS liners was critical to the test results Without the liners, the eluate naphthalene concentration would increase to a point where mass transfer would be affected Planning for PDMS liners is essential: Doubles the number of analysis samples since both the eluate and liner extract need to be analyzed If analyzing both VOCs and SVOCs require separate test cylinders and test vessels because the methods require different extractants. This would require FOUR times the number of analytical samples. 25

26 Acknowledgements Acknowledgements: US EPA - Christos Tsiamis CH2M HILL Mike Niemet, Morgan Bruno, Dusty Berggren and Dr. Andy Garrabrants 26