Bench-Scale Testing Report Pre-Design Investigations ... · relative mix design performance....

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Bench-Scale Testing Report Pre-Design Investigations

Gowanus Canal Brooklyn, New York

Prepared for United States Environmental Protection Agency

July 2013

Prepared by

III

Executive Summary A field investigation was performed in order to collect data in support of the active capping design for contaminated sediments at the Gowanus Canal in Brooklyn, New York. Soft and native sediment samples were collected to investigate general chemistry, limited geotechnical properties, and non-aqueous phase liquid (NAPL) mobility potential, and to evaluate in-situ stabilization (ISS) of native sediments through bench-scale testing.

Evaluation of ISS included leaching testing using the newly developed Leaching Environmental Assessment Framework (LEAF) testing programs developed by the United States Environmental Protection Agency (USEPA). The LEAF methods are used to characterize fundamental leaching behavior by testing under specific release conditions to provide a basis for comparison between treated and untreated materials.

The general chemistry investigation results were consistent with those found during the Remedial Investigation (RI) at the Canal. It also found that naphthalene had the highest leachable concentration from raw bulk sediment and was therefore most appropriate to use as a target constituent of concern (COC) for assessing ISS performance in the bench-scale study.

The geotechnical investigation showed results consistent with those found in a more extensive geotechnical investigation performed by National Grid using different testing methods. Both investigations showed that native sediments exhibit acceptable amounts of settlement under the stresses of an applied active cap as proposed in several of the remedial alternatives proposed in the Feasibility Study (FS).

The NAPL mobility investigation found high NAPL impacts in the native sediments, with pore fluid saturations (PFSs) (percent of pore volume occupied by NAPL) up to 50 percent at Transect 338. The NAPL impacts in soft sediment were significantly higher than the NAPL impacts in native sediments at Transect 339, while the soft sediment impacts were relatively low at Transect 340. Of the tested sediments, only the native sediment samples from Transect 338 showed mobility during water flood testing. Mobility was limited to samples with more than 20.8 percent PFS. A correlation was observed between total petroleum hydrocarbon (TPH) (sum of diesel, gas, and oil fractions) and NAPL content from PFS, suggesting that a TPH concentration greater than 58,000 milligrams per kilogram (mg/kg) indicates that NAPL mobility may occur.

The bench-scale ISS test found that NAPL mobility was not observed after stabilization, indicating that ISS may be an appropriate technology to sequester NAPL migration.

The addition of 1 percent oleophilic clay (OC) alone to native sediment reduced the cumulative release of naphthalene based on batch leaching tests, but this absorption capacity is likely to be exhausted under continuous loading scenarios in the Canal.

The mix designs tested showed:

Strength test criteria were for unconfined compressive strength (UCS), and the results indicate that ISS would provide a stabilized material of sufficient strength to support an active cap as proposed in the FS.

Hydraulic conductivity was significantly decreased. All test mix designs resulted in a decrease of one to two orders of magnitude in hydraulic conductivity relative to untreated native sediment, indicating that ISS would reduce percolation through the stabilized sediment relative to the untreated sediment.

ISS significantly reduces mass transfer from untreated native sediment. All mix designs showed a large reduction in effective diffusion coefficient (De) relative to the untreated native sediment, indicating that mass release would be reduced with any of the mixes tested. The relative reduction in De is considered indicative of relative mix design performance.

Leaching from ISS-treated sediment is reduced by an order of magnitude compared to untreated native sediment. This release reduction is considered to be reliable over the long-term since the increased strength of the stabilized sediment is sufficient to provide durability.

BENCH-SCALE TESTING REPORT PRE-DESIGN INVESTIGATIONS GOWANUS CANAL, BROOKLYN, NEW YORK

IV

The addition of OC did not significantly reduce leaching. Mix designs with Portland cement (PC)/slag cement and bentonite alone reduced leaching nearly 90 percent relative to untreated sediment; the addition of OC to the mixture only reduced leaching by another 32 percent relative to the PC/slag cement mixture. The inclusion of OC was not required for the mixes to cure into a stabilized monolith.

Overall, the bench test showed that ISS has the potential to significantly reduce NAPL migration and dissolved COC mass releases in the areas of the Canal targeted for ISS treatment. More investigation, including an ISS pilot-scale test, will be performed prior to design of the final remedy for the Gowanus Canal.

V

Contents Executive Summary .......................................................................................................................................... iii

Acronyms and Abbreviations ............................................................................................................................ ix

1 Introduction ...................................................................................................................................... 1-1 1.1 Site Description ................................................................................................................................ 1-1 1.2 Purpose and Organization of Report ............................................................................................... 1-2

2 Sample Collection Activities ............................................................................................................... 2-1 2.1 Overview .......................................................................................................................................... 2-1

2.1.1 Visual Core Sampling .......................................................................................................... 2-1 2.1.2 Shelby Tube Sampling ......................................................................................................... 2-2 2.1.3 Bulk Sample Collection ....................................................................................................... 2-3

2.2 Groundwater and NAPL Sample Collection ..................................................................................... 2-4 2.3 Deviations from the QAPP ............................................................................................................... 2-4

3 General Chemistry and Geotechnical Testing ..................................................................................... 3-1 3.1 Methods ........................................................................................................................................... 3-1

3.1.1 General Chemistry .............................................................................................................. 3-1 3.1.2 Geotechical ......................................................................................................................... 3-1

3.2 Deviations from the QAPP ............................................................................................................... 3-1 3.3 Results and Analysis ......................................................................................................................... 3-2

3.3.1 General Chemistry .............................................................................................................. 3-2 3.3.2 Geotechnical ....................................................................................................................... 3-3

4 NAPL Mobility Testing ....................................................................................................................... 4-1 4.1 Methods ........................................................................................................................................... 4-1

4.1.1 Core Cutting and Preparation ............................................................................................. 4-1 4.1.2 NAPL Pore Fluid Saturation................................................................................................. 4-1 4.1.3 Water Flood Testing ........................................................................................................... 4-1


4.3.1 Sample Selection ................................................................................................................ 4-2 4.3.2 NAPL Pore Fluid Saturation and Distribution ..................................................................... 4-3 4.3.3 NAPL Mobility Potential ...................................................................................................... 4-3 4.3.4 Comparison of PFS to TPH .................................................................................................. 4-4

4.4 Conclusions ...................................................................................................................................... 4-5

5 Bench-Scale Stabilization Testing ....................................................................................................... 5-1 5.1 Purpose ............................................................................................................................................ 5-1 5.2 Objectives ........................................................................................................................................ 5-1 5.3 Methods ........................................................................................................................................... 5-2

5.3.1 Sample Collection ............................................................................................................... 5-2 5.3.2 Sediment Characterization ................................................................................................. 5-2 5.3.3 Mix Testing ......................................................................................................................... 5-3


5.5.1 Raw Sediment Characterization ......................................................................................... 5-5 5.5.2 Strength .............................................................................................................................. 5-7 5.5.3 Hydraulic Conductivity ........................................................................................................ 5-7 5.5.4 Environmental Testing ........................................................................................................ 5-7


VI

5.5.5 Semi-Dynamic Leaching (SDL)............................................................................................. 5-8 5.5.6 Untreated and Treated Sediment Comparison ................................................................ 5-10 5.5.7 Mix Design Comparison .................................................................................................... 5-10

5.6 Conclusions .................................................................................................................................... 5-10

6 References ........................................................................................................................................ 6-1

Appendixes

A Field Sampling Notes B Sediment Core Logs C Sediment Core Photographs D General Chemistry Analytical Laboratory Reports E Geotechnical Laboratory Reports F Native Sediment Bearing Calculations G NAPL Mobility Laboratory Report H ISS Laboratory Reports I National Grid NAPL Laboratory Analytical Results J 1316 Leaching Laboratory Report K Calculations: 1316 Mass Released for Tested Liquid/Solid Ratios L SDL Laboratory Report M 1315 Leachability Backup Calculations

Tables

2-1 Sediment Sample Collection Details 2-2 Visual Core Location Data 2-3 Native Sediment Sampling Intervals

3-1 General Chemistry and Geotechnical Sample Summary 3-2 General chemistry Results Summary 3-3 Pocket Penetrometer and Pocket Torvane Summary 3-4 Consolidation Testing Summary 3-5 Geotechnical Results Summary 3-6 Hydraulic Conductivity Results Summary from Native Sediment Cores

4-1 NAPL Mobility Sample Summary 4-2 NAPL Pore Fluid Saturation Results Summary 4-3 Water Flooding Results Summary 4-4 NAPL Pore Fluid Saturation Results Summary – Post Water Flooding 4-5 Comparison of Pore Fluid Saturation to TPH

5-1 Final Chronic Values 5-2 ISS Mix Design Summary 5-3 338A Composite Characterization Summary 5-4 Effective Solubilities of NAPL Constituents 5-5 338A Raw Sediment Composite – USEPA 1316 Extraction 5-6 338A Treated Sediment – USEPA 1316 Extraction 5-7 ISS 7-day Unconfined Compressive Strength Results Summary 5-8 ISS 28-day Unconfined Compressive Strength Results Summary 5-9 28-Day Cure Hydraulic Conductivity Results Summary 5-10 Analytical Results Summary from 7-Day ISS Core Breaks 5-11 USEPA 1315 Extraction – Eluate vs. Liner Masses 5-12 USEPA 1315 Extraction – Effective Concentrations 5-13 Physical Parameters Summary – USEPA 1315 Extraction

CONTENTS

VII

5-14 Benzene Summary – USEPA 1315 Extraction 5-15 Toluene Summary – USEPA 1315 Extraction 5-16 Ethylbenzene Summary – USEPA 1315 Extraction 5-17 m,p-Xylene Summary – USEPA 1315 Extraction 5-18 o-Xylene Summary – USEPA 1315 Extraction 5-19 Naphthalene Summary – USEPA 1315 Extraction 5-20 USEPA 1315 Extraction – Diffusivity Coefficients 5-21 USEPA 1315 Extraction – Retardation Factors 5-22 Comparison of Mix Design Performance

Figures

1-1 Site Location Map

2-1 Sediment Sample Locations 2-2 Groundwater and NAPL Sample Locations

3-1 Total PAH Concentrations in Native Sediment

4-1a Groundwater Upwelling Velocities 4-1b Groundwater Upwelling Velocity Calculations 4-2 Transect 338 Recovery and Pore Fluid Analysis Locations 4-3 Transect 339 Recovery and Pore Fluid Analysis Locations 4-4 Transect 340 Recovery and Pore Fluid Analysis Locations 4-5 338C-C Eluate 4-6 338B-G Eluate 4-7 ISS-Treated vs. Raw Native Sediment NAPL Mobility Testing 4-8 NAPL Method Correlation

5-1 Percolation Release vs. Mass Transfer Release 5-2 ISS Mix Design Process 5-3 Leaching Testing Setup – USEPA Method 1316 Raw Sediment vs. USEPA Method 1315 Stabilized

Monoliths 5-4 USEPA Method 1315 Leaching Test Procedure 5-5 Raw Sediment Total and SPLP COC Concentrations 5-6 Leaching of Raw Native Sediment and 1% OC-amended Native Sediment 5-7 Unconfined Compressive Strength Comparison – Raw vs. ISS Treated Sediment 5-8 Hydraulic Conductivity Comparison – Raw vs. ISS Treated Sediment 5-9 Raw vs. ISS-Treated Sediment – Total Naphthalene Concentrations 5-10 Relative Mass Release – Eluate vs. PDMS Liner 5-11 1315 Concentration Comparison 5-12 Diffusivity Coefficients by Mix Design 5-13 Retardation Factors by ISS Mix Design 5-14 Leaching Comparison – Raw vs. ISS-Treated Sediment

IX

Acronyms and Abbreviations ASL Applied Sciences Laboratory ASTM American Society for Testing and Materials

bgs below ground surface BSTR Bench-Scale Testing Report BTEX benzene, toluene, ethylbenzene, and xylene BTEXN benzene, toluene, ethylbenzene, xylene, and naphthalene BTU/lb British thermal unit per pound

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of 1980 cm/sec centimeter per second COC constituent of concern

DAW diffusion coefficient in water De effective diffusion coefficient Dobs observed diffusion coefficient Dp diffusion coefficient adjusted for a porous media

FS Feasibility Study ft/day foot per day

GPS global positioning system

IDW investigation-derived waste ISS in-situ stabilization

L/S liquid-to-solid ratio LEAF Leaching Environmental Assessment Framework

mg/kg milligram per kilogram mg/L milligram per liter MGP manufactured-gas plant mL milliliter ML non-plastic silt mL/g milliliter per gram mL/min milliliter per minute

NAPL non-aqueous phase liquid

OC oleophilic clay OL organic silt

PAH polycyclic aromatic hydrocarbon PC Portland cement PDMS polydimethylsiloxane PFS pore fluid saturation PID photoionization detector psf pound per square foot psi pound per square inch

QAPP Quality Assurance Project Plan

RAO remedial action objective RF retardation factor RI Remedial Investigation


X

ROD Record of Decision RTA Remedial Target Area

SDL semi-dynamic leaching SM silty sand SPLP synthetic precipitation leaching procedure SVOC semivolatile organic compound SW-SM well-graded sand with silt

TOC total organic carbon TPH total petroleum hydrocarbon tsf ton per square foot

UCS unconfined compressive strength USCS Unified Soil Classification System USEPA United States Environmental Protection Agency

VOC volatile organic compound

BENCH-SCALE REPORT.DOCX 1-1

SECTION 1

Introduction The United States Environmental Protection Agency (USEPA) Region 2 completed a comprehensive Remedial Investigation (RI) in the Gowanus Canal (USEPA, 2011). The results of this investigation indicated that Gowanus Canal sediments are impacted with non-aqueous phase liquids (NAPLs). A Feasibility Study (FS) of remedial alternatives for the Gowanus Canal (CH2M HILL, 2011) presented the following remedial action objectives (RAOs) for the NAPL‐impacted sediments:

Prevent the migration of NAPL into the canal after the remedial action is completed

Prevent NAPL from serving as a source of contaminants to groundwater discharging to the canal

To address these RAOs, the FS presented alternatives that included active capping of the entire canal. Active capping is expected to both control NAPL migration and reduce the dissolved phase flux of contaminants to the Gowanus Canal. In-situ stabilization (ISS) of native sediment was selected as a remedial technology to be included for the preferred alternative where the NAPL impacts were high.

A field investigation was performed in order to collect data in support of the active capping design and to collect bulk sediment samples to be used in bench-test studies to evaluate ISS. This field investigation was performed as a joint effort between USEPA (represented by CH2M HILL) and National Grid (represented by GEI).

This Bench-Scale Testing Report (BSTR) was prepared for USEPA Region 2 by CH2M HILL to present the results of the bench-scale testing that was conducted in accordance with the Technical Plan for Pre-design NAPL Mobility and Geotechnical Investigation (CH2M HILL, 2012a) and the Technical Plan for Pre-design Bench Scale Testing of In-situ Stabilization of Native Sediments (CH2M HILL, 2012b). These results will be used to evaluate where and how ISS can be applied on the native sediments to achieve the established RAOs. Sampling and testing activities were performed, except where noted, following the procedures in the Quality Assurance Project Plan (QAPP) (CH2M HILL, 2012c). Testing, except where noted, was performed by CH2M HILL’s Applied Sciences Laboratory (ASL), in Corvallis, Oregon.

USEPA retained the services of Professor Andrew Garrabrants of Vanderbilt University to assist in the ISS bench-scale tests. Professor Garrabrants was a lead contributor for the developed of the Leaching Environmental Assessment Framework (LEAF) testing programs that lead to the development and release of new leaching test methods used in the bench tests.

1.1 Site Description The Gowanus Canal is a 1.8-mile-long, man-made canal in the Brooklyn Borough of New York City, in Kings County, New York (Figure 1-1). The canal was built in the 1860s by bulkheading and dredging a tidal creek and surrounding lowland marshes. Following construction, the canal quickly became one of the nation’s busiest industrial waterways, servicing heavy industries that included manufactured-gas plants (MGPs), coal yards, cement manufacturers, tanneries, paint and ink factories, machine shops, chemical plants, and oil refineries. It was also the repository of untreated industrial wastes, raw sewage, and surface-water runoff for decades, causing it to become one of New York’s most polluted waterways. Although the level of industrial activity along the canal has declined over the years, high levels of contamination remain in the sediments.

On March 2, 2010, USEPA placed the Gowanus Canal (USEPA Identification Number: NYN000206222) on its National Priorities List of hazardous waste sites requiring further evaluation. Accordingly, USEPA Region 2 has conducted a RI and FS of the canal according to the requirements of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) (also known as “Superfund”), as amended. The RI was completed in January 2011 (USEPA, 2011) and the FS was completed in December 2012 (USEPA, 2012a). The FS presented remedial alternatives for the Gowanus Canal. A Proposed Plan for remedial action was submitted by USEPA for public comment on December 27, 2012 (USEPA, 2012b), and a Record of Decision (ROD) for the canal is


1-2 BENCH-SCALE REPORT.DOCX

expected to be released in 2013. The pre-design activities conducted during this study are intended to gather additional information that is needed to support the Proposed Plan and ROD and design of the preferred remedial alternative during the remedial design phase.

1.2 Purpose and Organization of Report This BSTR presents the results of the field investigation and bench-scale testing. The report is organized into the following five sections:

1. Introduction. Briefly describes the regulatory framework, BSTR purpose and organization, and site setting.

2. Sample Collection Activities. Discusses the samples that were collected to support this investigation.

3. General Chemistry and Geotechnical Testing. Presents the materials and methodologies used to conduct the geotechnical tests and presents the associated results, analyses, and conclusions.

4. Non-Aqueous Phase Liquid Mobility Tests. Presents the materials and methodologies used to conduct the NAPL mobility tests and presents the associated results, analyses, and conclusions.

5. Bench-Scale Stabilization Testing. Presents the materials and methodologies used to conduct the ISS bench-scale tests and presents the associated results, analyses, and conclusions.

6. References. Presents a list of documents cited in this report.

All tables, figures, and appendixes are included at the end of the report.


SECTION 2

Sample Collection Activities 2.1 Overview Sample collection activities were conducted between November 27 and December 7, 2012. Figure 2-1 shows the five transects where sediment sampling was planned. As described in the following paragraphs, sampling was completed only along three of the five transects.

The collected sediment samples, along with the planned samples that were not collected, are listed in Table 2-1. The table includes the coordinates where each sample was collected, the sediment layer of each sample, and the depth interval of each sample. Field notes from the sampling activities are included as Appendix A.

Sampling was initially started at Transect 338 and moved down the canal. Planned samples at transects 336 and 337 were not collected due to access issues. The 3rd Street, Carroll Street, and Union Street bridges crossing the Canal were all damaged during Hurricane Sandy prior to the sampling event. None of these three bridges were restored to operational status during the sampling event, so barge access to the areas of the canal above 3rd Street was not possible. Additionally, the planned sample at location 340C on transect 340 had to be adjusted approximately 45 feet towards the center of the Canal due to another barge parked on top of the planned sample location.

At each location, the planned sampling approach was to collect an initial sediment core from the soft sediment surface (mudline) to approximately 5 feet below the soft and native sediment interface via vibracore drilling. These samples are considered “bulk” samples and are not undisturbed. These initial “visual” cores were to be used both to log the core and to collect general chemistry samples. As close as possible to these initial cores, additional co-located cores were to be advanced into the native sediment to collect undisturbed native sediment samples in Shelby Tubes using the same vibracore drill rig. The visual core was collected first and used to determine the depth of the soft and native sediment interface. After collection of the visual core was completed, Shelby tube samples were collected at that location before the barge was moved to the next location. Sampling (visual and Shelby tubes) at each location across the targeted transect was completed prior to making a decision based on visual observations on which location should be targeted for bulk sample collection. The barge was then moved back to the chosen location to complete bulk sample collection. Additional details about each of these sampling activities are presented as follows.

Groundwater and NAPL samples assumed to be representative of those present in the canal sediments were collected from two upland wells. The locations of the wells where the groundwater and NAPL sample were collected are shown on Figure 2-2. Additional details about these sampling activities are presented as follows.

2.1.1 Visual Core Sampling Upon arrival at each sampling station, the spuds were lowered to anchor the sampling barge in place and the actual global positioning system (GPS) coordinates were recorded. The GPS coordinates were obtained from a handheld Trimble GeoXH with an external antenna that was positioned alongside the vibracore tooling above the moon pool. The GPS coordinates of each sample location and the total depth of the visual boring are presented in Table 2-2.

The vibracore was then advanced from the mudline in 5-foot runs. After each 5-foot run was advanced to depth, the core barrel was retrieved from the borehole and the sediment was vibrated into the plastic “bag” liner. The core barrel was then advanced back down the borehole to collect the next 5-foot run. The drillers were asked to stop advancing the borehole after a minimum of 5 feet of native sediment had been visually identified. The drillers then pulled all tooling and grouted the borehole closed.



Each 5-foot run of sediment was photographed and logged. Sediment core logging included the following activities:

Visual logging of sediment material according to American Society for Testing and Materials (ASTM) D2488

Visual logging of apparent NAPL impacts

Obtaining photoionization detector (PID) readings at approximately every 1-foot interval

Strength testing with a shear vane and pocket penetrometer

Recording of observations on the sediment core logs

Sediment core logs are presented in Appendix B. Sediment core photographs are presented in Appendix C.

Samples from the most-impacted 1-foot-long interval of the soft sediment, as determined by visual observations and PID readings, was collected in the appropriate glassware with a disposable plastic scoop directly from the core. Soft sediment material from along the entire length of the soft sediment column was then collected with a new disposable plastic scoop and homogenized in a disposable aluminum paint tray. The composited soft sediment material was then transferred to the appropriate glassware using the same disposable scoop used to homogenize the material. The remaining composite left after filling all necessary sample jars was placed in a gallon Ziploc bag, which was sealed and placed in a second sealed, outer Ziploc bag. This material was placed on ice in the cooler to be saved for the transect-wide soft sediment composite for heat of combustion analyses. All sample jars were wiped clean to remove excess sediment from the outside, labeled, placed in bubble wrap, sealed in Ziploc bags, and placed in the cooler on ice until they were transferred to land for shipping.

The sampling process previously described for soft sediment was repeated for native sediment, with the most visually impacted 1-foot-long segment collected as a grab sample. Samples from the native sediment material from along the entire length of the recovered core were then collected and containerized using the same selection and homogenization process. Any remaining composited native sediment volume exceeding the analytical requirements was placed in the sediment investigation-derived waste (IDW) drum.

In some sample locations, the visual core was advanced to more than 5 feet below the soft and native sediment interface, which was the maximum boring depth specified in the QAPP. Consequently, the composite native sediment sample locations 338A, 338C, 339A, 339C, and 340C included native sediment material from below the targeted top 5-foot zone of interest. Additionally, the grab sample from the most highly impacted recovered native interval at location 338C was actually collected from below the targeted top 5 feet of native sediment. A comparison of the targeted native sediment intervals versus collected composite and grab sample intervals is presented in Table 2-3.

After sampling was completed at each of the three locations across a given transect, the Ziploc bags containing the remaining soft sediment composite material from each of the three locations was transferred to a new disposable aluminum paint tray. The materials from the three locations were homogenized using a disposable plastic scoop. The transect composite was then transferred into the correct glassware with the same disposable scoop used for homogenization. The sample jar was wiped clean to remove excess sediment from the outside, labeled, placed in bubble wrap, sealed in a Ziploc bag, and placed in the cooler on ice until it was transferred to land for shipping. Any remaining transect composite soft sediment volume exceeding the analytical requirement was placed in the sediment IDW drum.

2.1.2 Shelby Tube Sampling All Shelby tube samples were collected using the same protocol. The Shelby tube was pushed to the targeted depth interval and opened to allow the sample to enter the Shelby tube. The tube was left in place for 20 minutes, and then the tube was tripped out of the hole and recovery was measured. If recovery was deemed sufficient, the drillers waxed the top end shut with hot wax applied via a metal ladle. After the wax on the top end began to harden, the tube was rotated 180 degrees and the bottom of the tube was waxed shut. Once the wax hardened, both ends were packed with sawdust and capped. The caps were taped in place with duct tape, and the tubes were labeled with the sample identification, top depth, bottom depth, and orientation. The geotechnical samples were placed in a 5-gallon pail to maintain upright orientation during storage. The NAPL mobility cores were placed

SECTION 2—SAMPLE COLLECTION ACTIVITIES


on their side in a large cooler filled with dry ice to freeze the pore fluids in place. The NAPL mobility cores were then shipped frozen on dry ice to the laboratory for analysis.

All collected Shelby tube samples are listed in Table 2-1, along with the recoveries achieved for each sample. Planned samples that were not collected are described as follows.

A second NAPL mobility Shelby tube was not collected at 338C because two attempts were completed to collect the sample from 6.5 to 9 feet below ground surface (bgs) with minimal recovery. There was gravel present in the visual logging vibracore from 6.5 to 7.5 feet bgs, so an additional attempt was made to collect the NAPL mobility Shelby tube from 7.5 to 10 feet bgs in an attempt to avoid the gravel layer that was thought to be contributing to poor recovery. Minimal recovery was achieved at this depth interval as well. This depth interval was abandoned, and only the 10- to 12.5-foot interval was collected.

A second NAPL mobility Shelby tube was not collected at 340B because three attempts were completed to collect the 8- to 10-foot interval sample and no recovery was achieved during any of the three attempts.

No Shelby tubes for either NAPL mobility or geotechnical analysis were collected at 340C. Multiple attempts were made to collect Shelby tube samples at this location using both the standard Shelby tube and the Gregory Undisturbed Sampler, and recovery was very poor on each attempt. In consultation with the drilling contractor and after evaluation of the collocated visual sediment core, it was decided that Shelby tube samples could not be collected at this location and no further attempts were made. The poor recovery was likely the result of the coarse-grained unconsolidated sand found at the top of the native sediment column at this location.

2.1.3 Bulk Sample Collection For native bulk sample collection, the vibracore was pushed to the depth of the soft and native sediment interface identified from the visual logging sediment core. The vibracore was then pushed 5 feet into the native sediment before being tripped out of the hole. The material was vibrated out of the vibracore into 5-gallon metal pails. Any excess (standing) fluid on top of the pails was poured off into the liquid IDW drum. The borehole was grouted closed, one spud on the barge was pulled up, and the barge was rotated approximately 2 feet before the spud was dropped down again to anchor the barge. The previous process was repeated at the new location. This process was repeated as necessary until the specified volume of sediment had been collected.

For location 338A where both soft and native sediment was collected, the vibracore collected sample from the top of the sediment (mudline) to the previously identified soft and native sediment interface. This material was tripped out of the hole and vibrated into soft sediment bulk metal pails. The vibracore then went back down the same hole, from the previously terminated depth at the soft and native interface to 5 feet below the interface before being tripped out of the hole. The previously described steps for native sediment bulk collection were then followed.

Based on observed visual NAPL impacts and recorded PID readings, it was decided that the bulk native sediment sample for ISS bench-scale testing at Transect 338 should be collected at location 338A. The barge was moved to this location and native sediment was collected from the 6- to 11-foot interval (top 5 feet of native sediment). Enough sonic cores were collected to fill nine 5-gallon metal pails approximately 4/5 of the way full. The pails were sealed and packed in overpack boxes for shipping. There was discussion midway through the collection of the bulk native sediment sample at 338A that some bulk soft sediment material may be useful for additional testing, and a decision was made to collect three buckets of soft sediment bulk material at this location. Three 5-gallon buckets were filled 4/5 of the way full, sealed, and packed in overpack boxes for shipping. Upon receipt at the laboratory, this soft sediment bulk sample material was held for potential future analyses.

Because the bulk sample planned at Transect 336 could not be collected due to access issues, it was decided to collect an additional contingency bulk sediment sample at location 339C. This sample was collected from the 8- to 13-foot interval (top 5 feet of native sediment). Enough sonic cores were collected to fill six 5-gallon metal pails approximately 4/5 of the way full. The pails were sealed and packed in overpack boxes for shipping. Upon receipt at the laboratory, this bulk sample material was held for potential future analyses.



2.2 Groundwater and Non-Aqueous Phase Liquid Sample Collection

GEI Consultants collected the planned NAPL and groundwater samples and then transferred custody to CH2M HILL field personnel for shipping. Five liters of groundwater and 5 liters of NAPL were each collected from wells CGRW-04 on the Citizens Site and FW-RW-107A on the Fulton Works Site (Figure 2-2). These samples were shipped under dangerous-goods placarding.

2.3 Deviations from the Quality Assurance Project Plan Sample collection was performed according to the procedures presented in the QAPP with a few exceptions. These deviations from the planned work related primarily to the locations sampled and are summarized as follows.

No samples or bulk native sediment material were collected at 336A, B, or C due to inoperable bridges preventing access

No samples were collected at 337A, B, or C due to inoperable bridges preventing access

Planned sample location 340C had to be adjusted approximately 45 feet towards the center of the Canal due to another barge parked on top of the planned sample location

Bulk native sediment material was collected at 339C for possible replacement use in ISS bench testing; this was an addition to samples planned in the QAPP

Bulk soft sediment material was collected at 338A; this was an addition to samples planned in the QAPP


SECTION 3

General Chemistry and Geotechnical Testing 3.1 Methods There were three different types of samples received at the laboratory for the general chemistry and geotechnical testing analyses:

Soft and native sediment samples obtained from the vibracore and placed in glass jars during the core logging process

Undisturbed samples of the native sediment in Shelby tubes

The list of the analyses completed as part of this study is shown in Table 3-1. The analyses performed followed well established methods as described in the Technical Plan (CH2M HILL, 2012a), and are not described in detail in this section.

3.1.1 General Chemistry Soft and native sediment samples in jars were sent to ASL for analysis of general chemistry parameters. The maximum‐impacted region of the soft and native sediment cores, based on visual observations and PID readings, were sub‐sampled and analyzed for total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) concentrations. The remaining soft sediment and top 5 feet of native sediment were homogenized separately and analyzed for average TPH and PAH concentrations. Composite native sediment samples were also analyzed for pH and total organic carbon (TOC). A composite of soft sediment from each transect was analyzed for thermal value.

3.1.2 Geotechical Native sediment samples in jars were sent to ASL for analysis of Atterberg limits. Undisturbed native sediment samples in Shelby tubes were shipped in an upright position to a specialty geotechnical laboratory for analysis of hydraulic conductivity and consolidation testing. Note that grain-size analysis was performed on select native sediment samples as part of the NAPL mobility suite of analyses described in Section 4.

3.2 Deviations from the Quality Assurance Project Plan Sample analysis was done according to the procedures presented in the QAPP with a few exceptions. These deviations from the planned work are summarized as follows.

Unconfined compressive strength (UCS) measurements (ASTM D2166) were not performed on the Shelby tube samples obtained from the native sediment due to the non-cohesive nature of the samples. Instead, pocket penetrometer and pocket torvane measurements obtained in the field during sampling will be used to estimate in-situ strength. Standard Penetrometer Testing and cone penetrometer testing results (obtained by GEI Consultants) will be used to provide information about in-situ strength.

Incremental consolidation testing (ASTM D2435) was added for Shelby tube samples that were not granular. This test was used to assess the primary consolidation and secondary consolidation of the sediment under compression.

It was not possible to perform Atterberg limit tests (ASTM D4318) on granular samples without a significant portion of clay and silt. On Transects 338 through 340, Atterberg limits were able to be determined for four of the nine samples obtained.



3.3 Results and Analysis The full laboratory analytical reports for the general chemistry parameters are provided in Appendix D. The full laboratory analytical reports for the geotechnical parameters are provided in Appendix E. This section presents an overall summary and analysis of the test results.

3.3.1 General Chemistry The results of the general chemistry analyses are summarized in Table 3-2. The following subsections provide a description of the results for select analytical parameters.

pH and Total Organic Carbon pH and TOC were obtained from composite native sediment samples obtained from each location across the transects. The ranges of pH values observed in the native sediment for each of the transects were:

Transect 338: 8.62 to 9.54

Transect 339: 7.79 to 8.23

Transect 340: 8.21 to 9.01

The generally basic range of the pH in the native sediments may be a significant factor to be considered in the selection and application of certain treatment process.

The ranges of TOC observed in the native sediment for each of the transects were:

Transect 338: 28,400 to 52,600 milligrams per kilogram (mg/kg)

Transect 339: 206 to 4,210 mg/kg

Transect 340: 1,120 to 6,950 mg/kg

These results were generally consistent with the results from the RI, which ranged from 1,130 to 168,000 mg/kg (mean = 18,700 mg/kg) for the native sediment samples. For comparison, the results for the soft sediment from the RI ranged from 55,400 to 151,000 mg/kg (mean = 91,500 mg/kg). On average, the soft sediment contained approximately 5 times more TOC than the native sediment, and TOC in the soft sediment is likely to contain a larger fraction of readily degradable organic material.

Thermal Value Composite soft sediment samples were obtained for each transect to give an average representation of the thermal value of the soft sediment. The samples were obtained because cogeneration of electricity during incineration of the dredged soft sediment was considered as a potential benefit in the treatment and disposal option in the FS. The thermal value results from the composite soft sediment samples were as follows:

Transect 338: 2,510 British thermal units per pound (BTU/lb)

Transect 339: 592 BTU/lb

Transect 340: 480 BTU/lb

The results from Transects 339 and 340 were similar to results from samples obtained near Seventh Street (319 BTU/lb) and Sacket Street (409 BTU/lb) in March of 2011. The result from Transect 338 was approximately 5 times higher than the 2011 results. The higher values at Transect 338 are likely the result of the higher NAPL content.

Total Petroleum Hydrocarbons Composite and grab samples from both the native and soft sediment intervals were obtained for TPH from each transect. The range of values observed for the overall sum of the TPH fractions (gas, diesel, and oil) for each transect were as follows:

Transect 338

Soft: 22,200 to 133,000 mg/kg

Native: 59,200 to 115,000 mg/kg

SECTION 3—GENERAL CHEMISTRY AND GEOTECHNICAL TESTING


Transect 339

Soft: 2,060 to 127,000 mg/kg

Native: 13.6 to 941 mg/kg

Transect 340

Soft: 5,840 to 17,500 mg/kg

Native: 191 to 19,000 mg/kg

For the native sediment, a comparison of the combined TPH results to TOC indicates that most of the TOC is made up of TPH (NAPL). This is to be expected since the native sediments are deeper in the sediment profile and less prone to the accumulation of biological organic material. The exception to this may be at Transect 339 where the NAPL impacts are relatively low, in which case the TOC is likely to contain a relatively larger portion of non-NAPL organic material. For both the native and soft sediment samples, the TPH-diesel fraction makes up the bulk of the combined TPH, followed by the TPH-oil, then the TPH-gas fractions. Section 4 will present a further analysis of combined TPH and comparison to NAPL pore fluid saturation (PFS).

The TPH of the soft sediments is also within the range of the TOC measured during the RI, but at a lower percentage due to the TOC impacts not associated with NAPL measured in the TPH analysis.

Polycyclic Aromatic Hydrocarbons Composite and grab samples from both the native and soft sediment intervals were obtained for PAHs from each transect. The range of values observed for the total sum of PAHs detected for each transect were as follows:

Transect 338

Soft: 4,210 to 16,600 mg/kg

Native: 16,600 to 49,400 mg/kg

Transect 339

Soft: 599 to 22,100 mg/kg

Native: 0.64 to 873 mg/kg

Transect 340

Soft: 97.5 to 3,300 mg/kg

Native: 241 to 8,050 mg/kg

For the native sediment, a comparison of the observed ranges of the total sum of PAHs detected for each transect are compared to the results from the RI on Figure 3-1. The figure indicates that the PAH results were similar for the two events.

3.3.2 Geotechnical The geotechnical data collection and analysis portion of the work was designed to integrate with the geotechnical investigation performed by National Grid in August 2012; its report was submitted to USEPA in May 2013. The purpose of the National Grid geotechnical investigation was to obtain geotechnical strength parameters of the Canal sediments to gain a better understanding of the sediments’ bearing and shear load capacities in addition to the sediments’ compressibility characteristics along the Canal (National Grid, 2013). The investigation by National Grid included:

Nineteen cone penetration tests (piezocone and flow penetrometer)

Five test borings – sonic drilling

A laboratory testing program that included geotechnical index testing:

grain-size distribution (ASTM D422)

unit weight (ASTM D7263)

specific gravity (Method not defined by National Grid)



natural moisture content (ASTM D2216)

organic content (ASTM D2974)

Atterberg limits (ASTM D4318)

unconsolidated-undrained compression (ASTM D2850)

isotropically consolidated undrained compression strength testing (ASTM D4767)

incremental consolidation testing (ASTM D2435)

USEPA’s work intentionally did not overlap National Grid’s studies, and its focus was to collect data by taking additional measurements or samples readily obtained from planned investigation work for the NAPL mobility assessment and bench-scale stabilization testing. The results of USEPA’s work are presented in this section. The combined data set of USEPA results presented in this report and National Grid’s work (National Grid, 2013) provide valuable information for the remedial design.

Strength Strength analysis on sediment samples provides information to support the assessment of the ability of the untreated native sediment material to structurally support installation of an active cap.

Table 3-3 lists a summary of pocket penetrometer and pocket torvane readings from USEPA’s sampling event. The pocket penetrometer reads in-situ UCS. The pocket torvane is a hand held vane shear device used for rapid measurement of undrained shear strength. USEPA’s measurements from the torvane device were also compared to National Grid data.

The samples tested in the laboratory by USEPA were all native sediment samples collected at least 6.25 feet or deeper below the mudline; samples analyzed by National Grid were primarily soft sediment samples collected as shallow as 0 to 2 feet below the mudline.

USEPA’s native sediments were primarily non-plastic silts (ML) and silty sands (SM) (Appendix B). There are slight variations to this generalization due to the presence of gravel and debris and location along the transects of the Canal and the impacts from upland runoff and tidal flows.

Pocket penetrometer and pocket torvane measurements taken in the field (Table 3-3, Appendix B) show relatively inconsistent results. The torvane results show variability of shear strength at various depths in both the soft and native sediments. As expected, sediments that were coarser-grained in composition showed little to no shear strength (Transect 340). At Transects 338 and 339, the shear strength tended to increase with depth. Shear strengths in the soft sediment were estimated at 60 to 300 pounds per square foot (psf). Native sediments where cohesion was present ranged from 500 to 3,000 psf.

Field shear-strength measurements collected with the pocket torvane were consistent with the cone penetrometer testing data collected by National Grid for shallow soft sediments and native sediments (National Grid, 2013). The National Grid data also showed that sediments towards the Canal mouth (Transect 340) are non-cohesive in nature and more coarse-grained than sediments at the upper transects. Strength data will need to be further refined during the remedial design. Analysis of the strength data is provided later in this section.

Consolidation Total settlement of the sediment can be divided into three portions: elastic (immediate) settlement, primary consolidation settlement, and secondary consolidation settlement. Elastic settlement occurs instantaneously when a load is applied. Consolidation is a process by which soils decrease in volume over time. In general, it is the process by which reduction in volume takes place by expulsion of water under long-term static loads. Consolidation is an important sediment property since it affects the long-term stability of the proposed active cap. (Holtz & Kovacs, 1981)

Consolidation is measured in a two-step procedure. Primary consolidation reflects the settlement over time when a load is applied with the time-rate of consolidation varying based on the material hydraulic conductivity. Secondary compression is the compression of sediment that takes place after primary consolidation consisting primarily of the rearranging of material particles.

SECTION 3—GENERAL CHEMISTRY AND GEOTECHNICAL TESTING


The samples chosen for consolidation testing were selected based on field visual observations during core logging to represent native sediments that appeared to be most susceptible to the largest amount of settlement. The preconsolidation pressures for consolidation testing were estimated using the Casagrandes method of approximation (Holtz & Kovacs, 1981). The preconsolidation pressure for sample 340B was estimated at 0.4 ton per square foot (tsf), and the preconsolidation pressure for sample 339C was estimated at 1.8 tsf, as presented in Table 3-4. Estimating an existing overburden pressure at 340B of 625 psf, the native sediment in this area is considered to be overconsolidated. Location 339C, with an estimated existing overburden pressure of 520 psf, is also overconsolidated. Overconsolidated soils typically exhibit lower potential for consolidation settlement and a more stable capping surface.

National Grid also performed consolidation testing on one sample at a location near Transect 340 (National Grid, 2013). This sample was also found to be overconsolidated, showing consistency with the 340B consolidation testing results. National Grid performed additional consolidation testing but this was within the soft sediment depths and upper reaches of the canal.

Atterberg Limits The Atterberg limit test determines the liquid limit and plastic limit of the canal native sediment samples tested. These properties relate to the compressibility, hydraulic conductivity, and strength of the native sediments, and these data ai in determining their suitability as a base for a cap; further data analysis will be needed in the remedial design phase.

The Atterberg limits results are summarized in Table 3-5. The Atterberg limit tests show that the native sediments tested are non-plastic. This is not consistent with National Grid data showing samples at boring number GC-B-005 at a depth of 15.3 feet with a Unified Soil Classification System (USCS) classification of organic silt (OL) having a plasticity index of 9, and at a depth of 11.45 feet with a USCS classification of OL and a plasticity index of 41. The Atterberg limits testing by USEPA was on samples on Transect 340 that were near the 6.25-foot depth below the mudline, and it is possible that the different locations contributed to the variability in plasticity shown.

Higher plasticity sediments are generally indicative of a higher susceptibility to consolidation settlement. Consolidation testing showed that native sediments specifically were overconsolidated indicating lesser amounts of long-term settlement are anticipated.

Hydraulic Conductivity USEPA performed hydraulic conductivity testing on eight native sediment samples at depths ranging from 6 to 12 feet below the mudline, as summarized in Table 3-6. The results provide information on the potential for transport of NAPL and groundwater from canal native sediments into the surface water.

The hydraulic conductivity ranged from 5.2x10-7 centimeters per second (cm/sec) to 2.4x10-4 cm/sec but was generally in the 1.0x10-6 cm/sec range. Samples with a higher hydraulic conductivity (339B and 340A) are classified as sands and gravels. Samples with lower hydraulic conductivities (and thus lower potential for NAPL transport) contained higher fractions of silt than samples with higher hydraulic conductivities (higher potential for NAPL transport). One outlier was sample 340B, at a depth of 6 to 8 feet below the mudline, which exhibited a hydraulic conductivity of 5.2x10-7 cm/sec where very little fines were present. A second test was performed on this sample to evaluate test consistency and varied effective stress and hydraulic gradients. The second test result was 5.0x10-7 cm/sec, which is within an acceptable margin of error of the test. The variation in hydraulic conductivity of the Shelby tube sample compared to the fines content of the grain-size test from the same location is likely due to the difference in depth of the two samples. The Shelby tube sample at 7 to 7.3 feet below the mudline most likely contained a USCS ML silt material (see boring log GC-SD340B [Appendix B]), whereas the grain-size test sample was collected at a depth of 6.25 to 6.44 feet below mudline, which was most likely a USCS well-graded sand with silt (SW-SM) material with a low fines content and higher hydraulic conductivity.

Conclusions The geotechnical tests performed on native sediment are in general agreement with the results provided by National Grid. The data presented in this report and by National Grid were used to perform preliminary settlement calculations on native sediment. The calculations are presented in Appendix F. The data analysis



indicates that acceptable amounts of settlement (4.3 to 4.4 inches) are expected for capping on the native sediment layer. The factor of safety in regards to bearing failure for the native sediment ranged from 7.6 to 8.4, displaying the variability in the bearing capacity, but a high factor of safety for bearing failure beneath the cap.


SECTION 4

Non-Aqueous Phase Liquid Mobility Testing 4.1 Methods Three different types of samples were submitted at the laboratory for NAPL mobility analysis:

NAPL and groundwater in separate glass jars

Soft sediment samples obtained from the vibracore and placed in glass jars during the core logging process

Undisturbed samples of the native sediment in Shelby tubes and frozen on dry ice to retain pore fluids

The list of the NAPL mobility analyses completed as part of this study is shown in Table 4-1. Several of the analyses performed followed well-established methods, as described in the Technical Plan (CH2M HILL, 2012a), and are not described further in this section.

4.1.1 Core Cutting and Preparation Upon receipt of the samples at the laboratory, the frozen Shelby tubes were removed from the dry ice and placed into a chest freezer for storage prior to processing. The core cutting procedure consisted of deep-freezing each Shelby tube in a liquid nitrogen bath for several minutes. The core was then removed from the bath and cut laterally into 2-inch slices with a diamond blade. Each slice was then placed into a sample containment cup and allowed to thaw in its original orientation. The surface of each slice was then photographed under ultraviolet and white light, and the photographs were used to select the core slices for further processing. The core selection process is described further in Section 4.3.1.

4.1.2 Non-Aqueous Phase Liquid Pore Fluid Saturation Measurement of NAPL PFS is a key parameter in the NAPL mobility suite of analyses. It uses a direct distillation process, called a Dean-Stark extraction (API, 1998), on the sediment sample to determine the volume of water and NAPL present. As performed, the Dean-Stark process involves various measurements that result in determination of a number of important parameters for the sample, including:

Total porosity (percent bulk sample volume)

Grain and bulk density (grams per milliliter)

NAPL, water, and air saturation (percent of pore volume)

4.1.3 Water Flood Testing The water flood tests utilize an up-flow column-type system to push water through undisturbed sediment core slices. The system is capable of continuous data monitoring of pressure changes within a few centimeters of water column up to approximately 20 pounds per square inch (psi) (46 feet of water column) under controlled and stable flow conditions. Very low Darcy fluxes can be employed. The top and bottom mounting plates of the test cell were perforated and lined with stainless steel wire mesh to allow water to flow through the test sample without washing the solids out of the sample. The upper mounting plate has an observation reservoir to note the presence of NAPL in the test eluate.

The existing groundwater model submitted by National Grid and prepared by GEI and Mutch Associate, LLC, was used as the basis for the groundwater discharge rates to the canal. Figure 4-1a shows the groundwater discharge rates documented in the groundwater report. Figure 4-1b presents calculations where these rates were converted to Darcy flux estimates based on the discharge area size. The estimated steady-state Darcy flux estimates for each Remedial Target Area (RTA) are:

RTA 1 – 0.3 foot per day (ft/day)

RTA 2 – 0.08 ft/day

RTA 3- 0.02 ft/day



These velocities represent the typical steady-state discharge velocities averaged over large areas of the Canal. Darcy flux rates much higher than 0.3 ft/day are expected in the Canal at isolated locations (seeps) and during low tides and periods of high precipitation. Therefore, the actual fluxes to be encountered at various specific locations can be expected to vary by at least an order of magnitude above these typical estimates.

For the water flooding tests, 50-milliliter (mL) aliquots of water were pushed through the samples at three different Darcy fluxes per sample:

Low: 0.43 ft/day (0.38 milliliter per minute [mL/min])

Medium: 0.86 ft/day (0.77 mL/min)

High: 4.3 ft/day (3.8 mL/min)

The low flux value of 0.43 ft/day was selected because it was close to the typical flux in RTA 1 of 0.3 ft/day and resulted in reasonable run times for each 50-mL water flood sample aliquot (approximately 2.2 hours). Some exceptions were made for samples that had uncharacteristically high or low conductivities. The resulting pressure drop across the samples ranged from 0.18 to 20.3 psi. In one of the tests, an additional 350 mL of water was passed through the test sample in order to assess the residual NAPL PFS in the sample after no more NAPL was observed to be released.

4.2 Deviations from the Quality Assurance Project Plan Sample analysis was done according to the procedures presented in the QAPP with a few exceptions. These deviations from the planned work are summarized as follows.

Fewer samples were collected than planned due to inoperable bridges preventing access to Transects 336 and 337 and incomplete recovery at some locations.

Fewer NAPL and groundwater samples were collected than anticipated due to access limitations and the availability of free product in certain wells.

Lower applied pressures were considered for the water flood testing in order to more closely approximate actual groundwater upwelling velocities.

The NAPL flood testing originally scoped was not performed. The goal of this test was to determine the pressures that would drive NAPL through the sample. CH2M HILL determined that the these tests would not be as beneficial as performing additional water drive tests at much lower pressures, similar to those exerted by the groundwater discharge to the Gowanus Canal. Data were collected to determine if NAPL is upwardly mobile in intact core segments under the actual discharge rates of the Gowanus Canal directly, rather than knowing the pressures where NAPL would move through impacted sediment.

4.3 Results and Analysis The full laboratory analytical report for the NAPL Mobility analyses is provided in Appendix G. The following subsections present an overall summary and analysis of the test results.

4.3.1 Sample Selection The ultraviolet and white light photography results (Appendix G, Tables 5 through 13) were reviewed in combination with the sediment boring logs to select samples to be run for PFS determination. Ultraviolet light photography of the core sections is a standard practice to assist in identifying NAPL impacts. Many NAPLs fluoresce under ultraviolet light. However, the samples collected from the Canal did not fluoresce under ultraviolet light, so the degree of NAPL impacts were identified based on visual photography.

Samples were selected where the visual NAPL impacts appeared to be the greatest, with preference given to locations closer to the soft-native interface. Samples at the ends of the core and samples with anomalies such as large rocks or voids were avoided. Approximately one PFS sample per foot of core was used as a guideline for the number of samples selected. Upon completion of the initial PFS analyses, the results were used to select additional samples from the core for the water flood tests.

SECTION 4—NAPL MOBILITY TESTING


4.3.2 Non-Aqueous Phase Liquid Pore Fluid Saturation and Distribution The results of the NAPL PFS analyses are summarized in Table 4-2.

The results are presented on simple cross-sections for each transect on Figures 4-2 through 4-4. Analysis of the results on the figures yielded the following general observations about the NAPL impacts in the three transects:

Transect 338 (338A-C): Native sediment NAPL impacts are the highest of the three transects. The NAPL impacts in the soft sediment are relatively less than those in the native. These results are in agreement with the site conceptual model, as Transect 338 is located adjacent to the Carroll Gardens former MGP site (Figure 2-1).

Soft Sediment: 5.5 to 20 percent NAPL PFS

Native Sediment: 2.3 to 50 percent NAPL PFS

Transect 339 (339A-C): Soft sediment NAPL impacts are highest of the three transects. The native sediment had little to no NAPL impacts except near the soft sediment interface. The low amount of native NAPL impacts was unexpected, as Transect 339 is located adjacent to the Metropolitan former MGP Site (Figure 2-1).

Soft Sediment: 2.4 to 50 percent NAPL PFS

Native Sediment: less than 0.1 to 7.6 percent NAPL PFS

Transect 340 (340A-C): Moderate native sediment NAPL impacts were observed. The NAPL impacts in the soft sediment are relatively less than those in the native and were less than the other two transects. These results are in agreement with the site conceptual model, as Transect 340 is located down the Canal from all three former MGP sites (Figure 2-1).

Soft Sediment: 0.4 to 5.9 percent NAPL PFS

Native Sediment: 2.1 to 15 percent NAPL PFS

In general, NAPL saturation was variable with depth. At location 338A on Transect 338, where sample recovery was the greatest, the highest NAPL PFS results were located throughout the 5-foot depth interval sampled, but the results were stratified with a low value measured between two higher values. This is characteristic of NAPL architecture where NAPL distribution is variable based on small changes in capillary pressures caused by changes in geology. Likely pockets of NAPL are possibly connected through tortuous flow paths, or the NAPL may be present in isolated pockets.

The low native sediment NAPL impact at Transect 339 was not expected since this location had NAPL impacts of coating, staining, and blebs documented during the RI. This illustrates the highly variable nature of NAPL impacts in native sediment along the reach of the canal. The variability of NAPL impacts at Transect 339 is also evident between the soft and native sediment layers where the soft sediment impacts were the highest measured compared to the relatively low native sediment NAPL impacts.

4.3.3 Non-Aqueous Phase Liquid Mobility Potential The groundwater upwelling into the Gowanus Canal has the potential to mobilize NAPL in the sediments upward into an overlying cap and/or surface water. The potential for NAPL to be mobilized upward increases with the degree of NAPL PFS, as well as with increasing groundwater upwelling velocity. The actual groundwater upwelling velocities into the Canal will vary substantially as a result of seasonal and tidal changes to the local hydraulic gradient affected by transient storm events. Figure 4-1a shows the groundwater velocity range that recharge into the bottom of the Canal.

Water Flooding Tests – Native Sediment The results of the water flooding tests performed on samples of native sediments are summarized in Table 4-3.

The water flooding tests indicated that NAPL could be mobilized from select samples at all three locations on Transect 338 (338A, B, and C). No NAPL was mobilized in samples from Transects 339 and 340. Of the five samples that showed NAPL mobility, only the two samples from 338B showed NAPL mobility at a Darcy flux at or below



0.43 ft/day, which was the initial low flux starting point for the tests. Select photos of mobilized NAPL during the water flooding tests are shown on Figures 4-5 and 4-6.

Table 4-4 summarizes the measurements of NAPL PFS after the water flooding tests were completed. The NAPL PFS values for samples where NAPL mobility was observed ranged from 20.8 to 41.2 percent, indicating that the potential for NAPL mobility exists when the NAPL PFS was greater than 20.8 percent. The sample with 20.8 percent NAPL PFS had additional water passed through it in order to push as much NAPL out as possible before the PFS measurement was obtained. Therefore, the NAPL PFS value of 20.8 percent can be considered to be representative of the residual NAPL PFS, where NAPL PFS values below this value are not likely to be mobilized by upwelling groundwater based on the tests conducted in this study. Additional sampling is recommended to verify this preliminary conclusion on NAPL residual saturation.

Water Flooding Tests – In-situ Stabilization-Treated Sediment Bench tests for ISS were performed and are discussed in the next section. One of the objectives of the ISS is to prevent migration of NAPL into the active cap overlaying native sediment. To determine if ISS prevented NAPL migration, one of the Mix Designs (Mix H1 described in Section 5) was tested in the water flooding test.

Figure 4-7 shows the results of these tests. The untreated sample was collected from Transect 338. The stabilized monolith from Mix Design H1 was crushed and placed in the test apparatus since the test equipment could not push water through a stabilized monolith. No NAPL was mobilized from this sample even at the highest flow velocities. The addition of stabilization agents adsorbs the NAPL, removing it as a liquid phase and preventing migration, even if the stabilized monolith is crushed.

4.3.4 Comparison of Pore Fluid Saturation to Total Petroleum Hydrocarbon NAPL PFS is a direct volumetric-based measurement of the quantity of NAPL present in a sample expressed as a percentage of the total pore space. Since PFS is a volume-based measurement, undisturbed samples will provide the most representative results, because the sample matrix is representative of in-situ conditions. However, representative sample bulk volumes can be estimated for loose samples, as was done for the soft sediment samples in this study.

The quantity of NAPL in a sample can also be expressed on a mass basis, and this most commonly reported as mass of NAPL per unit mass of sample (mg/kg). If the site NAPL is made up predominantly of petroleum hydrocarbons, then there is a physical relationship between the combined TPH (that is, gasoline, diesel, and oil) and the NAPL PFS. The following relationship is taken from ASTM E2531-06:

Rearranging the terms yields:

Where:

So = NAPL PFS TPH = Total petroleum hydrocarbon concentration in mg/kg ρfb = Soil field bulk density ρo = NAPL density n = Soil porosity

As part of this study, TPH was analyzed independently as part of the general chemistry suite of parameters described in Section 3. Additionally, co-located NAPL PFS samples were either obtained directly from the same cores (soft sediment) or from an adjacent Shelby tube sample at the same depth (native sediment). Therefore, the data collected in this study allowed for a direct comparision of the two independent measurements. It should be noted that more often than not, attempts to correlate independent measuements of these types on other past projects has resulted in poor correlations. The reasons for the typically poor correlation are not well understood,

SECTION 4—NAPL MOBILITY TESTING


since the relationship between the mass-based and volume-based parametrers is physically based. However, possible options include sample variabilty, matrix interference, and method extraction issues.

For the data on this project, since the soil bulk density, porosity, and oil density were measured as part of the PFS analysis, these data were converted from NAPL PFS to TPH for the comparison. If a reliable correlation can be developed, future design investigations could consider using TPH analysis (which does not require undisturbed cores or the Dean-Stark distillation) to characterize NAPL impacts.

Figure 4-8 shows the correlation plot between NAPL PFS (converted to a mass basis) and TPH, where TPH represents the sum of the gas-, diesel-, and oil-range fractions (see Table 3-2). In this case, a 74 percent correleation exists between the independent results. Additionally, the correlation was close to a 1-to-1 relationship, which indicates that the two independent techniques produced statistically similar results for the Gowanus samples. A summary of the data used in the correlation plot is shown in Table 4-5.

The direct relationship suggests that the residual NAPL PFS saturation, determined from the NAPL mobility tests, could be converted to mg/kg and used to infer a TPH threshold for potential NAPL mobility. Furthermore, the TPH results from this sampling event (and past and future events) could potentially be used as a surrogate indicator of NAPL PFS. As discussed in Section 4.3.3.1, NAPL mobility was observed for NAPL PFS values at or above 20.8 percent. No mobile NAPL was observed below this threshold in the limited sample analyzed. The corresponding mass-based NAPL content where NAPL mobility was observed was above approximately 58,000 mg/kg. It should be noted that there was considerably more variabiliy in the mass-based NAPL content, which is a direct result of variability in the porosity of the samples. Future work on NAPL impacts should include TPH analysis to determine if this preliminary conclusion is valid and whether TPH can be used to determine potantially mobile NAPL areas for the remedial design.

4.4 Conclusions A summary of key conclusions from the NAPL mobility testing are described as follows:

Transect 338 (near the Citizen’s MGP) had the highest NAPL impacts in the native sediments, with NAPL PFS values ranging up to 50 percent.

The soft sediment NAPL impacts were significantly higher than the native sediment at Transect 339 (near the Fulton MGP).

The soft and native sediment NAPL impacts were relatively low at Transect 340, some distance downstream of the two MGPs.

The water flooding tests indicated that Transect 338 was the only transect to show mobile NAPL in the native sediments tested. Mobile NAPL was observed at NAPL PFS values above 20.8 percent, and NAPL mobility occurred at all three sample locations across Transect 338 (338A, B, and C).

A 74 percent correlation was found between independent measurements of TPH (directly measured, sum of gas, diesel, and oil fractions) and NAPL content (converted to mg/kg from NAPL PFS). These data suggest that 58,000 mg/kg of TPH represents a conservative lower bound where NAPL mobility may occur.


SECTION 5

Bench-Scale Stabilization Testing 5.1 Purpose ISS was presented in the FS (CH2M HILL, 2011) as a potential remedial technology for select sections of native sediment within the Gowanus Canal. This technology was included as part of two of the remedial alternatives to address NAPL migration to the Canal. The top 5 feet of native material was selected as the target treatment area based on available information, which indicated that NAPL impacts at the boundary between native and soft sediment had NAPL saturated conditions. This finding increased the likelihood of continued NAPL migration to the Canal. ISS utilizes select reagents to decrease sediment hydraulic conductivity and adsorb constituents of concern (COCs), thus reducing NAPL migration and contaminant leaching.

To evaluate the potential effectiveness of ISS at the Gowanus Canal and to gather the suite of information needed for a remedial design, several stages of investigations are warranted, including:

Geotechnical testing

NAPL mobility testing

ISS bench-scale testing

Design investigations to delineate conditions along the Canal where ISS should be applied

Pilot testing

This section presents the results from the ISS bench-scale testing. Together with the results of the geotechnical testing and NAPL mobility testing described in the previous sections, these results from the ISS testing will be used to evaluate where and how ISS can be applied to achieve the established RAOs of preventing NAPL migration and reducing the leachability of NAPL impacted sediment.

The following sections summarize the objectives, methods, and findings of the bench-scale stabilization testing.

5.2 Objectives Fifteen mix designs using highly NAPL-impacted native sediments from a target ISS area identified in the FS were evaluated in the ISS bench-scale test. The objectives of this test were to measure decreases in the leaching potential of COCs, reductions in sediment hydraulic conductivity, and increases in material strength from the stabilized sediment monoliths.

A minimum UCS criterion of 20 psi is used for the ISS tests based on the required integrity of molded samples during testing.

Targets for final leaching concentrations from the stabilized materials were based on the Final Chronic Values presented in the FS as shown in Table 5-1. The semivolatile organic compounds (SVOCs) selected for leaching concentrations were based on the composition of NAPL from the MGP sites. Although there are no Final Chronic Values for volatile organic compounds (VOCs), VOCs are included in the study because of their presence in NAPL in canal sediments.

Leachability of COCs from the granular native sediment was characterized using a batch extraction leaching method (USEPA Method 1316, hereinafter referred to as 1316), while stabilized sediment monoliths underwent long-term, semi-dynamic leaching (SDL) tests (USEPA Method 1315, hereinafter referred to as 1315) to evaluate COC leachability. The different leaching methods for granular and monolithic materials directly address the mode of water contact for each of these materials in the environment. Groundwater will flow through or “percolate” through granular material such as native sediments, and release will be controlled by the partitioning of COCs between the solid and liquid phases. After ISS treatment, groundwater migration through the material is significantly reduced due to a reduction in the hydraulic conductivity in solidified materials, and water contact is dominated by flow around the ISS mass. The rate of COC release is controlled by the rate of mass transfer



through the pore structure of the stabilized monolith to the surface exposed to groundwater. Figure 5-1 presents an analogy of percolation and mass transport release using common household materials.

Results from these analyses were used to determine the reduction in COC leaching that can be achieved through ISS.

5.3 Methods Figure 5-2 presents a summary flow chart showing the various tests performed as part of the ISS bench-scale test. The test and analytical methods are explained in more detail in the following subsections.

5.3.1 Sample Collection Sampling was generally conducted as described in the Technical Plan for Pre-Design Bench Scale Testing of In-Situ Stabilization of Native Sediments, Gowanus Canal, Brooklyn, New York (CH2M HILL, 2012b), hereinafter referred to as the ISS Testing Work Plan. Additional detail on sediment sampling was provided in Section 2 of this BSTR.

5.3.2 Sediment Characterization At the laboratory, samples were homogenized by placing the entire sample in a lined metal trough and thoroughly mixing the material with shovels until the sample was visually homogeneous. The homogenized sample was then sub-sampled for characterization, and then placed into sealed 5-gallon buckets until used in ISS testing. Characterization of the homogenized sample included measurement of:

Total VOCs and SVOCs (SW8260 and SW8270) in triplicate to determine the variability in COC concentrations of the homogenized sediment

Synthetic precipitation leaching procedure (SPLP) VOCs and SVOCs (USEPA 1312/SW8260 and SW8270) in triplicate

Moisture content (ASTM 2216) in triplicate

Leaching by modified 1316

1316 is designed to measure liquid-solid partitioning of non-volatile or inorganic constituents as a function of the liquid-to-solid ratio (L/S). Two modifications were employed to increase data reliability for volatile constituents of interest. First, headspace was minimized in leaching vessels through optimization of the vessel size relative to L/Ss to reduce volatilization of constituents. Second, samples were centrifuged to separate the liquid and solid phases instead of filtering the sample to reduce losses through volatilization during filtering.

Reagent Information The solidification and stabilization test evaluated 15 mix designs utilizing combinations of three reagents:

Portland cement (PC)/Slag Cement – Lafarge Type I/II (60 percent) blended with NewCem (40 percent) with either

Bentonite – CETCO Premium Gel (Type API 13 Section 9)

or

Oleophilic Clay (OC) – CETCO SS-199

PC/Slag Cement are inorganic cementitious/pozzolanic agents used to transform the sediment into a durable solid, low-hydraulic-conductivity material. The use of OC as a stabilizing agent was based on its greater selectivity for chlorinated VOCs and SVOCs (Sell et al., 1992), presence of NAPL, and the reported tendency of activated carbon to foul in the presence of NAPL (Reible et al., 2008) and its associated high bulking (it has a very low unit weight). OC dosing (up to 4 percent) was bracketed based on the sorption capacity in aqueous solution (0.5 pound organics per pound OC), the expected quantity to break the separate phase (NAPL) based on consideration of chemical partitioning relationships, and total VOC and SVOC content.

SECTION 5—BENCH-SCALE STABILIZATION TESTING


Mix Creation and Curing Reagent mix designs are summarized in Table 5-2. Initially, the test scope was set to evaluate PC doses ranging from 10 to 20 weight percent; however, trial premixes created to gauge mix consistency indicated that these PC doses yielded solidified samples with high strength within 3 days. The PC dose range was then scaled back to 5 to 10 weight percent. This scaling back is expected to result in cost savings in a full scale application.

The reagent grouts were prepared immediately before mixing them with the sediment. Tap water, cement, and bentonite or OC were added and thoroughly mixed with a stainless steel spoon following the addition of each reagent. Test mixtures indicated that a water-to-reagent mass ratio of 0.8 yielded a grout of proper consistency (similar to pancake batter) for pumpability.

Fully prepared grouts were slowly added to the wet sediments contained in stainless steel mixing bowls. Grouts were folded in with a stainless steel spoon, and then the material was thoroughly blended by hand until the mixture was homogeneous. Tap water was added to each mixture to achieve a consistency similar to a milkshake. After homogenization, the mixed material was distributed to 10 cylindrical molds (2 inches in diameter by 4 inches length). Each mold was labeled with the mix design identification code and a letter, replicates A through J (see Figure 5-2). Material was transferred into the molds in five lifts, and the molds were gently tamped on a hard surface to remove air pockets from within the material. After the final lift was delivered and the mold was tamped, the top surface was leveled with a spatula and covered with plastic snap-on lids. The molded samples were left undisturbed to cure at room temperature.

5.3.3 Mix Testing Stabilized sediment monolith replicates were selected for testing after 7 or 28 days of curing. These analyses are described as follows.

Unconfined Compressive Strength After curing for 7 days, replicates A through C of each mixture were analyzed for UCS. The molded samples were weighed and the dimensions recorded, then the maximum strength at failure was determined following strength testing. These parameters were used to calculate the UCS (applied force per unit surface area) for each replicate.

Material from each replicate was collected in a Ziploc bag and sampled for measurement of moisture content. All material from the crushed cylinders for each mix design was then combined in one Ziploc bag, reduced in size to pass through a 3/8-inch sieve, homogenized, then sampled for analysis of total and SPLP SVOCs and VOCs (SW8270/SW8260). Residual material was stored in a Ziploc bag at 4 degrees Celsius.

After 28 days of curing, three replicates (D through F) were analyzed for UCS as previously described. The moisture content was measured for each replicate, and residual material for each mix design was collected in a Ziploc bag and stored at 4 degrees Celsius.

Hydraulic Conductivity After curing for 28 days, replicate G of each mix design was submitted to GeoTesting Express, Inc., in its existing mold for analysis of hydraulic conductivity using a flexible wall permeameter (ASTM D5084). Moisture content, specific gravity, and wet and dry unit weights were included as part of this analysis. Hydraulic conductivity testing was performed at an effective stress of 5 psi.

Batch Leaching Testing The 1316 test is intended to measure equilibrium concentrations at different L/S where L/S is the ratio of the volume of liquid (that is, extractant plus inherent water contained in the material) to the dry mass of solid material and is usually expressed in units of milliliters per gram (mL/g), dry weight, at the laboratory scale and liters per kilogram, dry weight, at the field scale. The concentrations of COCs in the eluent are directly measured. The release rate is calculated by multiplying the concentration by the L/S.

The 1316 tests were performed on raw sediment. In addition, to determine whether the addition of OC alone could reduce COC leaching from the raw sediment, without stabilization, an additional 1316 test was performed on raw sediment amended with 1 percent OC. Testing was performed as described in Section 5.3.2. In addition to



the five 1316 extracts with L/S varying from 0.5 to 10 mL/g, another revision was made to the testing procedure to include an extract at L/S of 20 mL/g, similar to the test condition of SPLP data for raw sediment that were analyzed in addition to the specified L/S.

Semi-Dynamic Leaching Testing SDL testing was conducted in accordance with modified 1315 using replicate H of each mix design. Professor Andrew Garrabrants of Vanderbilt University consulted with ASL on the performance and modification of this testing method. For this analysis, solidified sample cylinders were statically suspended in an exchangeable deionized water bath for set leaching intervals. At the conclusion of the leaching interval, the samples were transferred to a fresh deionized water bath, and the eluate (deionized water) from the previous period was analyzed for COCs. The 1315 test setup for ISS Mix Designs H6 through H10 is shown on Figure 5-3, and an overview of the SDL process is shown on Figure 5-4.

1315 is designed for analysis of inorganic leaching over a 63-day period and, in itself, is not suitable for characterization of volatile or semivolatile constituent leaching. Three modifications were employed to address the release of VOCs. The modifications assisted in the retention of organic constituents by reducing the headspace within the leaching vessels, bypassing eluate filtration before analysis, and using leaching vessels lined with polydimethylsiloxane (PDMS) to capture COCs diffusion from the solidified monolith. The PDMS liner acted as a VOC sink to maintain low aqueous concentrations in the water bath and therefore preserving the concentration gradient between the solidified materials and the water bath, which is the driving force for mass transport. This modification allowed for determination of mass transport rates without the aqueous solubility limitations for compounds with low solubility.

The use of PDMS liners in the 1315 test was developed by Vanderbilt University, and its use for PAH leaching was documented by the Electric Power Research Institute (2009) to address the low solubility and high volatility of some SVOC and VOC compounds. The purpose of this modification to the procedure is to adsorb VOC and SVOC compounds from the eluate to prevent losses through volatilization and prevent them from accumulating in the eluate at concentrations that would reduce the mass transfer from the stabilized monolith.

After the water eluate was sampled and removed from each leaching vessel, the PDMS liner was extracted with 30 mL of purge-and-trap-grade methanol. Each jar was continuously rotated on its side for 16 hours for the liner extraction, and then the extractant was removed. The efficiency of this single extraction was determined by performing multiple extractions at two different time points. Each subsequent extraction removed approximately 34 percent as much mass as the previous extraction; therefore, the concentration of each constituent measured in the first extract represented approximately 66 percent of the total mass adsorbed to the PDMS. Leaching calculations assumed that this efficiency was applicable to every time-interval for every constituent. Both the water eluate and methanol extract were analyzed for VOCs using SW8260 for a total of 11 time–intervals, the nine intervals noted in 1315, plus additional intervals at 77 and at 90 days.

Leaching data from 1315 were managed using LeachXS Lite (Vanderbilt, 2010), a database-driven software tool for management and visualization of LEAF leaching data. After generation, analytical data for the elutent and extractant at each leaching interval were entered into the LeachXS Lite data analysis spreadsheet. This spreadsheet was used to upload laboratory and analytical data for 1315 into the LeachSX Lite program in order to produce graphical representations and summary tables of the SDL testing results.

Contingency Replicates Replicates I and J of each mix design were spare specimens that have been archived as contingency until after the bench-testing materials are released for disposal.

5.4 Deviations from the Quality Assurance Project Plan Bench-testing was performed according to the procedures presented in the QAPP with a few exceptions. Deviations from the planned work are summarized as follows.



The triplicate samples from VOC and SVOCs were not collected at the same time. The later samples showed lower COC concentrations likely a result of volatilization of VOCs. In addition, the homogenized samples had lower overall concentrations than the grab of field composite samples, likely a result of VOC loss from the bulk sample during transport or during the homogenization process.

Based on high strength preliminary results from trial mixes, the cement doses were reduced to 5, 7.5, and 10 percent cement from the original planned additions of 10, 15, and 20 percent.

USEPA Method 1314 (hereinafter referred to as 1314) was replaced by a modified 1316 after further discussion with Professor Garrabrants indicated that batch testing would provide equivalent release data with a more controlled leaching test for the particular suite of contaminants.

1316 leaching tests were run on an additional sample of sediment with a 1 percent OC dose. This was reduced from the 1, 2, 3, and 4 percent OC doses planned for the 1314 tests due to the larger quantity of sediment required to produce the L/S required to analyze for SVOCs.

A PDMS coating was added to the 1315 vessels in order to absorb the organic constituents from the aqueous phase and to maintain the maximum concentration gradient for diffusion from the solidified matrix. This required a methanol extraction and an additional chemical analysis of the extract at each time interval.

The Leach XS Lite data analysis spreadsheet was modified by Professor Garrabrants to account for the use of the PDMS liner COC concentration in addition to the eluate concentration to calculate an “effective concentration” for the mass released calculations.

SVOCs were eliminated from the 1315 analyses based on only two SVOCs being detected in the SPLP tests, naphthalene and 2-methylnaphthalene; naphthalene was detected at approximately 6 times the concentration of 2-methylnaphthalene in the SPLP test. Naphthalene is also analyzed in the VOC test and therefore was analyzed as part of the VOC test program.

5.5 Results and Analysis Results of the various analyses performed as part of the ISS bench-scale testing are summarized in the following subsections. The full laboratory analytical reports are provided in Appendix H.

5.5.1 Raw Sediment Characterization The results of the various analyses performed to characterize the raw native sediment composite sample from location 338A are detailed in the following subsections.

General Chemistry SPLP and Total VOC and SVOC concentrations in the raw composited sediment used in the bench-scale test are summarized in Table 5-3. The pure component solubility limits in water are also presented. Naphthalene was the only VOC in the sediment to exceed 10 percent of its pure-phase aqueous solubility limit. Several other SVOCs exceeded 10 percent of their respective solubility limits, but the solubility limits of these compounds are so low that none were detected at concentrations above their respective method reporting limit. Since naphthalene was the only positively detected compound to leach from the untreated sediment under SPLP leaching conditions, naphthalene was selected as the representative target compound for these tests.

Figure 5-5 presents a graph of the benzene, toluene, ethylbenzene, and xylene (BTEX) and PAH constituents detected in the SPLP analysis and their corresponding total concentrations. As shown, 2-methynaphthalene was detected in the SPLP analysis, but only at 20 percent of the concentration of naphthalene, justifying the use of naphthalene to characterize PAH leachability for the subsequent tests.

Batch Leaching NAPL COC Effective Solubilities



The effective solubilities of COCs detected in the NAPL from the Gowanus Canal sediment were calculated from the pure-component water solubilities and the mole fraction of COCs in a NAPL sample from upland well CGRW01 based on Raoult’s law:

Where SA = effective aqueous solubility of the NAPL component A XA is the mole fraction of A in the NAPL SA theoretical = theoretical solubility of the pure component A in water γNAPL = activity coefficient of A in the NAPL (assumed to be 1 for all compounds)

The laboratory analytical data for the NAPL sample are included in Appendix I. The total mass accounted for in VOC and SVOC analysis only accounts for 80 percent of the mass present. Since this is for a NAPL sample, the remainder are organic compounds, just not measured in the VOC or SVOC analysis. The remaining 80 percent is likely aliphatic hydrocarbons of various carbon chain lengths. The molecular weight of the unidentified fraction was assumed to be 200 grams per mole, representing a C12 to C16 hydrocarbon. The resulting effective solubilities of the COCs, as well as other detected compounds in the NAPL mixture, are summarized in Table 5-4. This calculation results in an effective solubility for naphthalene of 4 milligrams per liter (mg/L).

The Raoult’s law calculation is expected to only approximate the effective solubility within factors of 2 to 4 in complex mixtures such as coal tar. The 4-mg/L effective solubility for naphthalene is in the range documented of 2 to 4 mg/L (ACSE, 2004).

Raw Sediment

The results of the 1316 leaching test on native sediment are summarized in Table 5-5. The complete analytical results are included as Appendix J. The concentration data were used to calculate a mass release and a time-equivalency for each L/S based on the planned stabilization scenario and the groundwater fluxes reported by National Grid (National Grid, 2013). These calculations are presented in Appendix K.

The naphthalene concentrations and mass of naphthalene released versus L/S are shown on Figure 5-6. The naphthalene concentrations at each L/S were relatively constant. The mass release and L/S are directly proportional, indicating that the release is solubility-controlled (ITRC, 2011). This indicates that the rate of mass released from untreated sediment is directly proportional to the rate of groundwater percolating through the sediment.

The SPLP data for the raw sediment are also shown on Figure 5-6, due to the fact that both SPLP and 1316 are batch extraction tests yielding leaching results assumed to represent partitioning between solid and liquid phases. However, SPLP is conducted at an L/S of 20 mL/g of material and has a larger maximum particle size specification. Including the SPLP data on the 1316 data analysis on Figure 5-6 provides an additional extraction data point, and makes the 1316 data more easily relatable to the more widely used SPLP value. The concentration of naphthalene released from each of the varying L/Ss is approximately the same (ranging from 5.19 to 6.50 mg/L), but the mass released increased with increasing L/S. The SPLP test produced a greater mass release than any of the L/Ss used in the 1316 test, as is expected from its greater L/S.

OC-Treated Sediment

Raw sediment was amended with one percent OC to determine if OC only would provide a significant reduction in naphthalene transport.

The results of the 1316 leaching test on native sediment amended with 1 percent OC are summarized in Table 5-5, and the complete analytical package is included in Appendix J. The COC concentrations and mass of COC released versus L/S are shown on Figure 5-6. The mass release and L/S are directly proportional, indicating that the release is solubility-controlled.

While the slope of the mass release versus L/S curve is equal to that seen for the untreated raw sediment, the masses of naphthalene released from the treated sediment were lower than those observed in the raw sediment



leaching test. A comparison of the two samples is also shown on the bottom of Figure 5-6. These data are used later in this report to compare to the mass release from ISS-treated sediment.

5.5.2 Strength For testing purposes, a minimum strength of 20 psi after 7 days of curing time was chosen as the performance criterion for this bench-scale test. As shown in Table 5-6, the average UCS of triplicate specimens for all mix designs easily exceeded 20 psi after 7 days curing time, and all mixes were carried forward for a 28-day cure. Table 5-7 summarizes the 28-day UCS testing results based on the average of triplicate specimens. All 7- and 28-day cure UCS values exceeded the 20-psi standard.

The strengths of all stabilized monoliths was much greater than the strengths estimated from the pocket penetrometer readings on the native sediment core in the field. The average UCS estimated by the pocket penetrometer for all locations in the canal was 7.6 psi, and the average UCS estimated by the pocket penetrometer for raw sediment at 338A was 4.34 psi (Table 3-3). All stabilized monoliths had strengths approximately 25 times or more greater than the raw sediment at 338A, as shown on Figure 5-7.

5.5.3 Hydraulic Conductivity Hydraulic conductivity tests were completed on 28-day cures of all mix designs. Once saturated, the samples were evaluated at an effective stress of 5 psi.

For typical ISS applications, a maximum hydraulic conductivity of the mix is typically specified to be on the order of 1x10-6 or 1x10-7 cm/sec. Table 5-8 shows the measured hydraulic conductivity-values for the mix designs to be within the 1x10-6 to 10-8 cm/sec range after 28 days of curing time. Mix H-10 has the greatest hydraulic conductivity value (1x10-6 cm/sec), and Mix H-12 has the lowest hydraulic conductivity value of the tested mixes (2.9x10-8 cm/sec). There was not a strong correlation between the OC content and the hydraulic conductivity, or between the PC content and the hydraulic conductivity. Table 5-8 also shows that all mix designs had a lower hydraulic conductivity after 28 days of curing compared to the raw native sediment sample collected at location 338A.

Figure 5-8 presents the raw native and mix design hydraulic conductivity results.

5.5.4 Environmental Testing After the 7-day UCS replicates were broken, the UCS sample breaks for the three replicates were composited and subjected to environmental analysis (totals and SPLP). Results of those tests are described as follows.

Totals Table 5-9 shows a comparison of the total VOC and SVOC results from the 7-day breaks compared to the total results of the untreated raw 338A native sediment homogenized sample. The results are compared only to the first of three replicates of the native sediment homogenized sample since the later two were collected at a later time. Total BTEX VOC values were generally similar to or lower in the mixes compared to the raw native sediment. The total SVOC naphthalene concentrations in all mixes were reduced to below those in the untreated raw native sediment.

Figure 5-9 presents a graph of the raw sediment total naphthalene VOC results and the 7-day break naphthalene VOC results. The results generally show that mass was conserved from the untreated to treated sediment. The 7-day break results are all lower than the raw sediment homogenized results where you would expect them to be lower from the addition of reagents.

SPLP Table 5-9 shows a comparison of the SPLP-VOC and SPLP-SVOC results from the 7-day breaks compared to the SPLP results of the untreated raw 338A native sediment homogenized sample. SPLP-naphthalene SVOC values were lower for all mixes compared to the raw untreated sediment. The SPLP-VOC values for all mixes were reduced below those measured in the raw native sediment for BTEX. Naphthalene increased slightly in the SPLP-VOC analyses for the mixes relative to the raw sediment.



The naphthalene SPLP concentration of nearly 8 mg/L is higher than the estimated naphthalene effective solubility concentration of 4 mg/L. Because the actual effective solubility can vary from the estimated value by a factor of 2 to 4, the SPLP concentration is considered a better estimate of the effective solubility and will be used in subsequent section of this report.

5.5.5 Semi-Dynamic Leaching The SDL test provides information on ISS treated material. This information includes:

Comparison of the eluate concentration to the solubility limit to determine if mass transfer was affected by the eluate concentration approaching the solubility limit.

Estimation of the rate of mass released. Because groundwater flow is significantly reduced where ISS is performed, the main mass transfer mechanism in the ISS-treated mass is diffusion. Under the assumption of simple diffusion, the diffusion coefficient is used in Fick’s law with the concentration gradient to calculate the rate of mass transfer. The USEPA 1315 data can be used to estimate the effective diffusion coefficient (De) using the procedures presented in this section. Changes in the De calculated from the cumulative release curve from similar sized monoliths are a measure of the leaching reduction achieved from ISS.

Comparison of the cumulative mass released from untreated sediment to the mass released from the stabilized monolith.

Eluate and PDMS Mass The concentrations of COCs in both the eluate and the methanol extract were determined for each interval. The measured concentrations of COCs in the PDMS liner methanol extract were all divided by 0.66 to account for the methanol extraction efficiency of the single methanol extraction. These resulting concentrations in the aqueous phase and PDMS extract were multiplied by the eluate volume and methanol extract volume, respectively, to calculate the masses in each phase for each time interval. Table 5-10 summarizes the relative masses of each COC recovered from the eluate (water bath) and methanol extract from the PDMS liner for each time interval. Figure 5-10 presents the mass of naphthalene in the PDMS and aqueous eluate fractions for each time interval in Mix H6. The mass of COCs recovered from the PDMS liner was far greater than the mass in the eluate, especially at the later intervals where interval leaching time was greater. The greater mass recovery from the PDMS phase over the aqueous phase indicates that the PDMS liner was performing its intended function of removing COCs from solution in order to maintain a strong concentration gradient at the solid and water interface. The relative amounts of mass from each phase for this mix design as shown in Figure 5-10 is representative of the mass distribution observed in the other mix designs.

Effective Concentration The masses in the PDMS phase and aqueous phase (described in the previous section) were combined and divided by the eluate volume to determine the effective concentration of COCs for each interval. This effective concentration is a hypothetical value that includes all of the mass released from the monolith for a given time interval. The effective concentrations for each interval are reported in Table 5-11.

The effective concentrations of the COCs, along with the eluate-only concentrations of COCs, were compared to the effective solubilities of the COCs from the site NAPL. The effective concentrations of all COCs exceeded the effective solubilities estimate for naphthalene (estimated by the SPLP result) at certain time intervals as shown on Figure 5-11.

These results show the benefit of using the PDMS liner. Because the PDMS liner adsorbed the naphthalene removing it from solution, the actual eluate concentration never exceeded 1.5 mg/L, well below the effective solubility estimate of 8 mg/L, maintaining a consistent and high concentration gradient during the test that did not approach the solubility limit.



Effective Diffusion Coefficient There are several ways that SDL test results can be used to assess the performance of mix designs: the primary methods being comparisons based on the measured De and shape (slope) of the cumulative mass curve of each COC from each mix design specimen.

The cumulative mass released from the mix designs can be used to estimate the De of a COC from a soil-cement cylinder based on a simple diffusion model of 1-dimensional diffusion of COCs from a mix design monolith suspended in a water bath. SDL tests were used to evaluate the leaching potential of benzene, toluene, ethylbenzene, xylene, and naphthalene (BTEXN) for all mix designs.

The underlying theory of relating the mass released per time interval to the De is described in USEPA 1315 documentation. The numerical approach developed by Crank (1986) is that the mass released over a time interval is proportional to the De and time to the ½ power by the following relationship:

Rearranged:

This equation was used to estimate the observed diffusion coefficient (Dobs) for each time interval of the SDL test, which accounts for both physical retention and chemical interactions within the monolith matrix. The Dobs for all of the leaching time intervals were then averaged to estimate the De for each mix design.

The complete analytical report for the SDL test is presented in Appendix L. The calculations of extraction efficiency, mass release, and effective concentration are presented in Appendix M. The physical parameters of each SDL test specimen are summarized in Table 5-12, and the leaching data by COC for BTEXN are summarized in Tables 5-13 through 5-18. The following sections address how the leaching data sets and their comparisons can be used for decision-making and mix design selection.

A main goal of ISS is to produce an intact soil-cement mass characterized by a hydraulic conductivity of 10-5 cm/sec or less (~10-7 cm/sec desired), which essentially renders the soil-cement as a diffusion-controlled system. Under these conditions, the retardation factor (RF) on contaminant transport effectively reduces to a comparison of the De of the COC, which includes physical retention of COCs due to steric effects of small pores and pore structure parameters (such as tortuosity and connectivity) versus its diffusivity through porous media (Dp). Dp is

the pore diffusivity, which accounts for the fact that the plane perpendicular to diffusion into water is a porous media. Dp is calculated from the free molecular diffusion of the COC in water (DAW).Mathematically, the RF on diffusive transport (leaching) for each COC from a stabilized sediment cylinder is expressed as Dp/De, and RFs much greater than 1 are desired.

Table 5-19 summarizes the estimated Dobs values for each mix organized by COC, where the raw data was taken

from Appendix L. Table 5-20 summarizes the estimated RF values for each mix, organized by COC.

Figure 5-12 presents the data in graphical form, with one graph showing the DAW, Dp, and De for each mix design, while Figure 5-13 shows the RF for each mix design.



COC Cumulative Mass Release By evaluating the slope of the cumulative COC mass release curve (from the soil-cement cylinder) over each time interval, insight is gained on the dominant mass transfer phenomena occurring at the surface of the specimen (that is, whether the leaching of the COCs is surface-controlled or diffusion-controlled, the latter being more preferable for long-term performance). The slope can vary significantly between COCs. A slope value of approximately 0.5±0.1 for the naphthalene cumulative release curve indicates that the release is diffusion controlled. Figure 5-14 presents the cumulative mass release curve for naphthalene for all mix designs. At initial time intervals, the slopes did not follow the 0.5 slope, indicating that other effects were having an impact on the mass release. The slopes approached 0.5 for all mixes at later time intervals as these other effects were diminished.

The cumulative mass release curves for BTEX are presented in Appendix J, and all cumulative mass release data for the COCs are presented in Tables 5-13 through 5-18. The BTEX cumulative mass release curves follow the trend observed for naphthalene, with initial time intervals deviating from a slope of 0.5 due to surface-washing effects, and these effects are diminished at later time points.

5.5.6 Untreated and Treated Sediment Comparison The difference in the COC mass flux rates determined by Methods 1316 and 1315 can be quantified. This requires that the test results be put on an equivalent basis. The 1316 mass release data are reported as a function of the L/S so the rate of liquid migration through the untreated sediment is needed to convert the results to a flux (rate per unit area) reported for the 1315 test.

The 1316 data were converted based on knowledge of the groundwater flow rates. Estimates of the discharge rate are provided from the groundwater model submitted by National Grid and prepared by GEI and Mutch Associate, LLC (GEI, 2011). For example, the discharge rate to RTA 1 is estimated at 352 gallons per minute over a surface area of approximately 215,000 square feet. RTA 1 is used because it has the highest groundwater discharge rate and therefore the shortest travel time through native sediment.

Appendix K presents the calculations performed to document the groundwater discharge rates and the 1316 data to determine the mass released per unit area of groundwater percolation. The calculations used a 5-foot sediment layer as proposed for the remedial alternatives using sediment stabilization. Once in the form of mass released per unit area, these data can be directly compared to the 1315 data mass release per unit area.

Figure 5-14 shows a graphical representation of these results showing that the mass released from stabilized sediment is nearly an order of magnitude less for naphthalene than untreated sediment. The mix design data show a relatively tight grouping of data points indicating limited difference in each mix design.

5.5.7 Mix Design Comparison The cumulative release data from the treated and stabilized sediment can be used to evaluate the effectiveness of each mix design. These data are shown in Table 5-21. The 90-day cumulative release data point for untreated sediment was determined from the graph on Figure 5-14 by interpolating between data points. The 1315 cumulative release for the 90-day interval was used for the stabilized sediment data points.

These results show that the mass releases from all the stabilized mixes were reduced by 89 to 93 percent compared to mass releases from the untreated native sediment, indicating there is very little difference in release reduction performance between the varying mix designs. The analysis in Table 5-21 also compares the release reduction between each mix design using Mix H1 as a basis. The data show an incremental improvement over H1 mix-design-based increasing cement and OC doses with the maximum reduction of 32 percent achieved for Mix H15 (10 percent PC and 4 percent OC).

5.6 Conclusions The purpose of the ISS bench-scale study for the Gowanus Canal Superfund site was to determine a range of mix designs for ISS of highly impacted sediment to measure decreases in the leaching potential of COCs, indicated by mass releases of BTEX and naphthalene during leaching tests. The main conclusions from this study are:



From the raw sediment chemistry section presented in Section 5.5.1.1, naphthalene had the highest leachable concentration and was used as the primary target COC to assess the performance of ISS. BTEX was examined as secondary target COCs for assessing the performance of ISS.

NAPL mobility test results presented in Section 4 showed that NAPL was potentially mobile in highly impacted areas. Once stabilized, no NAPL mobility was observed, indicating NAPL migration can be sequestered by stabilization.

The addition of 1 percent OC to native sediment reduced the cumulative release of naphthalene from the native sediment based on Method 1316 testing. However, the absorption capacity of the OC would likely be exhausted under continuous mass loading scenarios.

All mix designs easily exceed the 20-psi test criterion. The addition of OC was not needed for the mixes to cure.

All mix designs showed a hydraulic conductivity decrease of one to two orders of magnitude compared to raw native sediment, indicating that percolation through native sediment would be greatly reduced by stabilization.

Data from effective solubility calculations, SPLP results, and Method 1316 results were consistent and illustrate a continuum of leaching behavior that can be used to predict COC release from native sediment.

The adaption of Method 1315 to VOCs was shown to be robust and reliable based on the use of the PDMS liners. Up to 88 percent of the naphthalene mass was captured with the PDMS liner. Without the liner, the eluate concentration would have approached the effective solubility limit for naphthalene in water, effectively arresting the rate of mass transfer from the mix designs leading to incorrect estimates of the reduced mass fluxes.

All mix designs tested showed a large reduction of up to three orders of magnitude in the De compared to raw native sediment. However, for organic constituents, mass release may not be entirely diffusion controlled because of surface effects. The De reduction is considered a relative measure of the mix design performance.

Comparison of the 1316 data for percolation release to the 1315 mass transfer release shows that stabilization can reduce naphthalene mass release by an order of magnitude. The release reduction is considered to have long-term reliability since the stabilized material has sufficient strength for durability. However, not much difference in performance was noted with increasing OC dose, and OC was not needed for the mixes to cure.

Overall, ISS has the potential to significantly reduce or eliminate NAPL migration and greatly reduce COC dissolved mass releases in ISS-treated areas.


SECTION 6

References American Petroleum Institute (API). 1998. Recommended Practices for Core Analysis. Recommended Practice 40. Second Edition. February.

American Society of Civil Engineers (ASCE). 2004. Natural Attenuation of Hazardous Wastes. June 21, 2004.

CH2M HILL. 2011. Draft Feasibility Study, Gowanus Canal. December.

CH2M HILL. 2012a. Technical Plan for Pre-design NAPL Mobility and Geotechnical Investigation. Revised October.

CH2M HILL. 2012b. Technical Plan for Pre-design Bench Scale Testing of In-situ Stabilization of Native Sediments. Revised October.

CH2M HILL. 2012c. Quality Assurance Project Plan, Gowanus Canal Superfund Site, Brooklyn, New York, Pre-Design Data Collection NAPL Mobility and Geotechnical Investigation and in Situ Stabilization Bench Scale Testing. October.

Crank. 1986. Mathematics of Diffusion, Oxford University Press, London.

Electric Power Research Institute (EPRI). 2009. Leaching Assessment Methods for the Evaluation of the Effectiveness of In Situ Stabilization of Soil Material at Manufactured Gas Plants. Electric Power Research Institute. March.

GEI. 2011. Groundwater Model Report, Gowanus Canal Superfund Site. December.

Holtz, Robert D., and William D. Kovacs. 1981. An Introduction to Geotechnical Engineering. Prentice Hall. Englewood Cliffs, New Jersey.

Interstate Technology and Regulatory Council (ITRC). 2011. Development of Performance Specifications for Solidification/Stabilization. Interstate Technology and Regulatory Council. July.

National Grid. 2013. National Grid Comments on the USEPA Proposed Remedial Action Plan for the Gowanus Canal. April.

Reible, D.D., Lu, X., Galjour, J., and Qi., Y. 2008. “The use of Organoclay in Managing Dissolved Contaminants Relevant to Contaminated Sediments,” Technical Report 840, CETCO, Hoffman Estates, IL, p.12.

Sell, N.J., Revall, M.A., Bentley, W., and McIntosh, T.H. 1992. “Solidification and Stabilization of Phenol and Chlorinated Phenol Contaminated Soils,” Stabilization and Solidification of Hazardous, Radioactive and Mixed Wastes: 2nd Volume, ASTM STP 1233, T.M. Gilliam and C.C Wiles eds., American Society for Testing and Materials, Philadelphia, PA, pp. 73-85.

United States Environmental Protection Agency (USEPA). 2011. Draft Gowanus Canal Remedial Investigation Report. Prepared by HDR, CH2M HILL and GRB Environmental Services Inc. for USEPA Region 2. January.

USEPA. 2012a. Feasibility Study, Gowanus Canal. Prepared by CH2M HILL for USEPA Region 2. December 2011.

USEPA. 2012b. Proposed Plan.

Vanderbilt. 2010. LeachXS Software. Available at: <http://www.vanderbilt.edu/leaching/>.

Figures

FIGURE 1-1Site Location MapGowanus Canal Superfund SiteBrooklyn, New York

Legend

Proposed Sampling Transect

Proposed Bulk ISS Transect

RTA 1RTA 2RTA 3b Sigourney Street to Redhook Channel

FIGURE 2-1Sediment Sample Collection Location MapGowanus Canal Superfund SiteBrooklyn, New York

Transect 340GC-SD76C near 66+49

Transect 339GC-SD64D near 51+61

Transect 337GC-SD11Anear 07+60

Not Sampled

Transect 336GC-SD152near 03+94

Not Sampled

Transect 338GC-SD44Anear 35+40

Metro MGP Fulton MGPCG/PP MGP

A

CB

A

CBA

CB

FIGURE 2-2Groundwater and NAPL Sample Collection LocationsGowanus Canal Superfund SiteBrooklyn, New York

CGRW-04

CGRW-06I

FW-RW-107

FIGURE 3-1Total PAH Concentration in Native Sediment Along Gowanus CanalGowanus Canal Superfund SiteBrooklyn, New York

241 to 8,050 mg/kg

0.64 to 873 mg/kg

16,600 to 49,400 mg/kg

Transect 340 Transect 339

Transect 338

Transect 336

Transect 337

Source:GEIGroundwater Model ReportGowanus Canal Superfund SiteDecember 2011Figure 6-1

07/01/2013

Figure 4-1a

Groundwater Upwelling VelocitiesSIZE

FSCM NO DWG NO REV

SCALE 1 : 1 SHEET 1 OF 2

07/01/2013

Figure 4-1b

Groundwater Upwelling Velocity CalculationsSIZE

FSCM NO DWG NO REV

SCALE 1 : 1 SHEET 2 OF 2

Canal

Segment Canal RTA

RTA Area

(ft^2)

Discharge

(gpm)

1 1 2312 1 1213 2 674 2 1265 2 96 3 732,361 67

Calculate Discharge per RTA (ft^3/day)231 gal + 121 gal 352 gal

min min min

352 gal 1440 min 1 ft^3 67760 ft^3min day 7.48052 gallon day

Calculate Darcy Flux (ft/day)

67760 ft^3 0.32 ftday 214,119 ft^2 day

Calculate Velocity (ft/day)0.32 ft 1.58 ft

day 0.2 porosity day

Canal

Segment Canal RTA

RTA Area

(ft^2)

Discharge

(gpm)

Discharge

(ft^3/d)

Darcy Flux

(ft/day)

Velocity

(ft/day)

1 1 2312 1 1213 2 674 2 1265 2 96 3 732,361 67 12897 0.02 0.09

214,119 67760 0.32 1.58

518,245 38885 0.08 0.38

214,119

518,245

Based on these calculations, the groundwater Darcy fluxes for RTA 1 and RTA 2 range from 0.08 to 0.5 ft/day. Assuming an effective porosity of 0.2, the groundwater velocities for RTA 1 and RTA 2 range from 0.4 to 1.6 ft/day.

Native Sediment

Soft Sediment

27%

2.3%

12%

25%

12%

26%

18%

27%

52%

50%

9.2%

36%

25%

Shelby Tube Core Recovered

NAPL Test Interval

Core Recovery Unsuccessful

Vibracore Recovered (Soft Sediment)

Grab (1.0-2.0')15%

Composite20%

Grab (5.0-6.0')19%

Composite17%

Grab (2.0-3.0')5.5%

Composite11%

NAPL Saturation (% Vpore)

Tota

l Dep

th (f

t)

Nat

ive

Sedi

men

t Dep

th (f

t)

FIGURE 4-2Transect 338 Recovery and Pore Fluid Analysis LocationsGowanus Canal Superfund SiteBrooklyn, New YorkVibracore Recovered

(Native Sediment)

Native Sediment 0.5%

<0.1%

<0.1%

<0.1%

0.9%

1.2%

<0.1%

<0.1%

<0.1%

<0.1%

<0.1%

<0.1%

<0.1%

7.6%


Grab (5.0-6.0')2.4%

Composite6.7%

Grab (4.0-5.0')8.2%

Composite9.4%

Grab (1.5-2.5')50%

Composite6.5%

Soft Sediment

Shelby Tube Core RecoveredCore Recovery Unsuccessful

Tota

l Dep

th (f

t)

Nat

ive

Sedi

men

t Dep

th (f

t)

<0.1%

FIGURE 4-3Transect 339 Recovery and Pore Fluid Analysis LocationsGowanus Canal Superfund SiteBrooklyn, New York

NAPL Test IntervalVibracore Recovered (Soft Sediment)Vibracore Recovered (Native Sediment)

Native Sediment

Soft Sediment

11%

4.0%

3.9%

9.7%

15%

2.1%

4.6%

2.1%

Grab (2.0-3.0')5.9%

Composite1.9%

Grab (4.0-5.0')0.4%

Composite0.6%

Grab (7.0-8.0')1.4%

Composite0.6%


Shelby Tube Core RecoveredCore Recovery Unsuccessful

Tota

l Dep

th (f

t)

Nat

ive

Sedi

men

t Dep

th (f

t)

FIGURE 4-4Transect 340 Recovery and Pore Fluid Analysis LocationsGowanus Canal Superfund SiteBrooklyn, New York

NAPL Test IntervalVibracore Recovered (Soft Sediment)Vibracore Recovered (Native Sediment)

FIGURE 4-5338C-C EluateGowanus Canal Superfund SiteBrooklyn, New York

0.43 ft/day, 0.88 psi 4.3 ft/day, 6.5 psi

FIGURE 4-6338B-G EluateGowanus Canal Superfund SiteBrooklyn, New York

0.43 ft/day, 1.9 psi 4.3 ft/day, 7.6 psi0.86 ft/day, 2.9 psi

FIGURE 4-7ISS-Treated vs. Raw Native Sediment NAPL Mobility TestingGowanus Canal Superfund SiteBrooklyn, New York

Stabilized Sediment mix H1, crushed Repacked Stablized Sediment Prepared for Water Drive Test

NAPL-free eluate from stabilized sediment

NAPL-containing eluate from Raw Native Sediment

NAPL Migration from Raw Native Sediment during Water Flood

Test

Raw Native sediment packed for testing

FIGURE 4-8NAPL Method CorrelationGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-1Percolation Release vs. Mass Transfer ReleaseGowanus Canal Superfund SiteBrooklyn, New York

Figure Source: Dr. Garrabrants, Vanderbilt University

FIGURE 5-2ISS Mix Design ProcessGowanus Canal Superfund SiteBrooklyn, New York

A B C D E F G H

R

S

S H

HOMOGENIZED LAB COMPOSITETotals, SPLP, & EPA 1316

VOCs, SVOCs(3 replicates)

SEDIMENT SOURCE MATERIALHIGH IMPACT AREA: Location 338A

ADD REAGENTS AS SLURRY TO LAB COMPOSITEPC: 5 to 10%OC: 0 to 4%Ben: 0 to 0.5%

Mix ReplicatesA-J (2x4 inch molds)

UCS K EPA 1315 (modified)

7 day 28 day 28 day

MIX DESIGNS (H-1 to H-15)

Curing Period

UCSPhysicochemical Data

Replicates A-G

Semi-dynamic Leaching Tests

Replicate H

28 dayReagent

suite

VOCs(2 hrs to 90 days)

Completed Gowanus Canal Mix Design Process

28 day

I J

SPARES

Check SlumpASTM C143

Totals & SPLPVOCs, SVOCs

MeOHExtraction of PDMS Liner

Eluate

Homogenized Raw Sediment + 1% OC

EPA 1316

FIGURE 5-3Leaching Testing Setup – USEPA Method 1316 Raw Sediment vs. USEPA Method 1315 Stabilized MonolithsGowanus Canal Superfund SiteBrooklyn, New York

1316 Test Setup – same raw sediment sample in each vessel (T01 through T05) with varying

L/S ratios

1315 Test Setup – test mix H7 through H10 monoliths in PDMS-

lined leaching vessels during time interval t0

(zero to two hours leaching time).

FIGURE 5-4USEPA Method 1315 Leaching Test ProcedureGowanus Canal Superfund SiteBrooklyn, New York

Apply PDMS liner to sample vesselsPlace stabilized sediment monoliths in sample

holders

Place stabilized sediment monoliths in DI water (eluate) in PDMS-lined vessels and leave for specified leaching

time intervalAt end of specified leaching itnerval, transfer monoliths from eluate bath into new PDMS-lined vessel containing fresh eluate

(DI water). Analyze previous eluate for COCs. Extract PDMS from previous sample vessel, and analyze extract for COCs.

Repeat Steps 3 and 4 for each specified testing interval. Combine measured PDMS COC mass and eluate COC mass and dividide by eluate volume to estimate effective eluate concentration with

PDMS mass included.

FIGURE 5-5Raw Sediment Total and SPLP COC ConcentrationsGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-6Leaching of Raw Native Sediment and 1% OC-Amended SedimentGowanus Canal Superfund SiteBrooklyn, New York

SPLP

Data points denoted as SPLP are from raw sediment characterization analysis. Added to 1316 data for comparison.

FIGURE 5-7Unconfined Compressive Strength Comparison – Raw vs. ISS Treated SedimentGowanus Canal Superfund SiteBrooklyn, New York

0

20

40

60

80

100

120

Unconfined Compressive Strength (psi)

Mix Design

Strength of Stabilized vs. Raw Sediment

Average 338A Native Sediment

Stabilized 338A Sediment

Raw H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14 H15

Note: All ISS-treated samples except H3 exceeded the maximum strength capacity of the instrument and were reported as “greater than” the strength values shown based on instrument maximum

force and physical dimensions of the sediment monoliths.

FIGURE 5-8Hydraulic Conductivity Comparison – Raw vs. ISS Treated SedimentGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-9Raw vs. ISS-Treated Sediment – Total Naphthalene ConcentrationsGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-10Relative Mass Release – Eluate vs. PDMS LinerGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-111315 Naphthalene Concentration ComparisonGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-12Diffusivity Coefficients by ISS Mix DesignGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-13Retardation Factors by ISS Mix DesignGowanus Canal Superfund SiteBrooklyn, New York

FIGURE 5-14Leaching Comparison – Raw vs. ISS-Treated SedimentGowanus Canal Superfund SiteBrooklyn, New York

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