A.02.11_Attach_4_Ref_6_RIR_VicenzaORC_Remediation.pdf

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F I N A L R E P O R T

POL83 Full Scale ORC Injection

Remediation Report

AEDB-CC site name: CCVI018

Prepared for

U.S. Army Corps of

Engineers, Europe District

February 2015

CH2M HILL s.r.l.

via XXV Aprile, 2

20097 San Donato Milanese (MI)

Italy

[458084-FINAL] CH2M HILL SRL III

Contents Section Page

Acronyms and Abbreviations .............................................................................................................. v

Introduction ................................................................................................................................... 1-1

1.1 Project Scope and Objectives .......................................................................................... 1-1

1.2 Deviations from Remedial Action Work Plan .................................................................. 1-2

1.2.1 Screened sections and well type ........................................................................ 1-2

1.2.2 Optimization of the second ORC injection design .............................................. 1-2

1.2.3 Extension of the project duration to allow implementation of an optimized remediation strategy, tailored to the specific critical areas and compound...... 1-3

1.2.4 Confirmatory sampling – duplicate batches for October 2015 events and focused sampling in November 2015 ............................................................................... 1-3

1.3 Regulatory Framework .................................................................................................... 1-3

1.4 Document Organization ................................................................................................... 1-4

General Environmental Setting and Site Background ....................................................................... 2-1

2.1 Site Setting ....................................................................................................................... 2-1

2.2 Local Geological and Hydrogeological Features .............................................................. 2-1

2.3 Historical Environmental Background ............................................................................. 2-2

2.4 Selected Remedial Approach ........................................................................................... 2-3

Field Activities Summary Description .............................................................................................. 3-1

3.1 Utility Avoidance and UXO Avoidance Activities ............................................................. 3-1

3.2 Wells Installation ............................................................................................................. 3-1

3.3 Topographic Surveys ........................................................................................................ 3-2

3.4 Injection Activities............................................................................................................ 3-2

3.4.1 Injected compound ............................................................................................. 3-2

3.4.2 Injection Methodology ....................................................................................... 3-3

3.4.3 First Injection Cycle Design ................................................................................. 3-3

3.4.4 Second Injection Cycle Design ............................................................................ 3-3

3.5 Groundwater Monitoring and Sampling Activities .......................................................... 3-4

3.5.1 Baseline Groundwater Monitoring (November 2012) ........................................ 3-4

3.5.2 Monthly Monitoring Events (December 2012 - October 2015).......................... 3-5

3.5.3 Focused Confirmatory Event (November 2015) ................................................. 3-5

3.5.4 Basewide Groundwater Monitoring (January 2015) .......................................... 3-5

3.5.5 Field Operations .................................................................................................. 3-5

Waste Management ....................................................................................................................... 4-1

ORC Injection Results ..................................................................................................................... 5-1

5.1 Local Geological and Hydrogeological Features .............................................................. 5-1

5.1.1 Geological Characteristics ................................................................................... 5-1

5.1.2 Hydrogeological Characteristics ......................................................................... 5-1

5.2 Chemical Features of the Aquifer .................................................................................... 5-3

5.2.1 Chemical Analyses Results .................................................................................. 5-3

5.2.2 Time-trend Analysis ............................................................................................ 5-6

5.2.3 Geochemical Parameters .................................................................................... 5-8

Conclusions and Recommendations ................................................................................................ 6-1

CONTENTS

Section Page

IV CH2M HILL SRL [458084- FINAL]

References ..................................................................................................................................... 7-1

Appendixes

Appendix A Boring Logs and New Wells Construction Scheme

Appendix B Photographic Documentation

Appendix C Field Forms

Appendix D ORC Injections Characteristics

Appendix E Waste Disposal Documentation

Appendix F 2012-2015 Analytical Results and Laboratory Certificates (electronic format only)

Appendix G MNA Evaluation

Tables

3-1 Summary of the Field and Laboratory Activities

3-2 New Monitoring Wells – Drilling and Installation Details

3-3 Topographic Survey Results (April 2013) – Injection Points Coordinates

3-4 Topographic Survey Results (October 2014) – Monitoring Wells Coordinates

3-5 Baseline (2012) and Basewide (2015) Monitoring – Wells list and Analytical Plan

3-6 Monthly Groundwater Monitoring Events (2012-2015) – Wells list and Analytical Plan

5-1 Head Differences in Nested Well Pairs (2012-2015)

5-2 Chemical-Physical groundwater data recorded during purging activities (2012-2015)

5-3 Time-trend analysis – Summary results (2012-2015)

All tables are presented at the end of the document

Figures

2-1 Site Setting

2-2 Site Layout

3-1 Groundwater Monitoring Wells Location and Sampling Frequency

5-1 Geological cross-section across injection area

5-2 Shallow Unconfined aquifer – Groundwater level fluctuations (2012-2015)

5-3 Baseline Groundwater Sampling (November 2012) - Groundwater Surface Map

5-4 Basewide Groundwater Sampling (January 2015) - Groundwater Surface Map

5-5 Groundwater Monthly Sampling (20 October 2015) - Groundwater Surface Map

5-6 2012-2015 - TPH distribution maps, time-trend fluctuations and summary statistics of measured concentrations

5-7 2012-2015 - Benzene distribution maps, time-trend fluctuations and summary statistics of measured concentrations

5-8 2012-2015 - MTBE distribution maps, time-trend fluctuations and summary statistics of measured concentrations

5-9 2012-2015 – Manganese distribution map, time-trend fluctuations and summary statistics of measured concentrations

6-1 2012-2015 - Time-trend of BTEX, TPH and MTBE concentrations in the injection area

6-2 Baseline Groundwater Sampling (November 2012) - TPH and Benzene distribution maps

6-3 Baseline Groundwater Sampling (October 2015) - TPH and Benzene distribution maps

All figures are presented at the end of the document

[458084-FINAL] CH2M HILL SRL V

Acronyms and Abbreviations amsl above mean sea level bgs below ground surface

BTEXS Benzene, Ethylbenzene, Toluene, Xylenes, Styrene

COC Constituent Of Concern

COE Corp Of Engineers

CSC Environmental Screening Level (Concentrazione Soglia di Contaminazione)

CSR Site-specific Risk-Based Clean up Goal (Concentrazione Soglia di Rischio)

D.Lgs 04/08 Legislative Decree n. 04, dated 16 January 2008

D.Lgs 152/06 Legislative Decree n. 152 dated 3 April 2006

DPT Direct Push Technology

DTW Depth to Water

GW Groundwater

HHRA Human Health Risk Assessments

HASP Health and Safety Plan

IDW Investigation Derived Waste

MDL Method Detection Limit

MTBE Methyl tert-butyl ether

MK Mann-Kendall

ORC Oxygen Releasing Compounds

ORC-A ORC-AdvancedTM

P&T Pump & Treat

PID Photo Ionization Detector

POL Petroleum, Oil & Lubricants

PP Project Plan / Treatability Engineering Assessment

QC Quality Control

RAWP Remedial Action Work Plan

RR Remediation Report

SAP Sampling and Analysis Plan

TPH Total Petroleum Hydrocarbons

USACE U.S. Army Corps of Engineers

USAG U.S. Army Garrison

UST Underground Storage Tank

UTM Universal Transverse Mercator

ACRONYMS AND ABBREVIATIONS

VI CH2M HILL SRL [458084- FINAL]

UXO Unexploded Ordnance

SECTION 1

[458084-FINAL] CH2M HILL SRL 1-1

Introduction This Remediation Report was prepared for U.S. Army Corps of Engineers (USACE) Europe District (EUD) by CH2M HILL, (CH2M HILL) and describes all the activities conducted under Contract Number W912GB-

10-D-0032, Task Order (TO) 0004, associated with the injection of Oxygen Releasing Compounds (ORC) at the Petroleum, Oil & Lubricants Point 83 (POL 83) site at the Caserma Del Din, former Dal Molin airfield, located in Vicenza, Italy.

1.1 Project Scope and Objectives

The overall project goal was the implementation of the Selected Remedy, consisting in an in situ enhanced bioremediation, based on the injection into the shallow aquifer of ORC products within the

Source Area and in the Plume area.

The site-specific project objectives included:

• Preparatory activities, including pre-survey of drilling locations, utilities clearance, site clearing, and

Unexploded Ordnance (UXO) avoidance;

• Soil drilling and upgrading the current groundwater monitoring network by installing five wells at locations selected within the Source Area, across-gradient the Source Area and south of the hydraulic barrier;

• Conduct a Baseline groundwater sampling to assess local aquifer conditions before the implementation of the remedial strategy selected for the Site;

• Injection of Oxygen Releasing Compound (ORC) aimed at the enhanced bioremediation of the site, both into the Source Area and within the Downgradient Plumes; the ORC compound that CH2M HILL adopted is the ORC-AdvancedTM (ORC-A) compound provided by the teaming company Regenesis;

• Conduct Monthly Groundwater Monitoring campaigns, including groundwater level measurements, purging and sampling operations and groundwater samples collection focused on monitoring the

ORC injections outcomes;

• Laboratory analysis of the collected samples and data validation of analytical results;

• Analytical data evaluation and assessment against applicable regulatory screening levels as well as risk based concentrations and evaluation of the effectiveness of injections.

A Remedial Action Work Plan (RAWP - CH2M HILL, 2012a) was prepared, together with a site specific

Health and Safety Plan (HASP) covering areas and activities included in the RAWP (CH2M HILL, 2012b).

Extraordinary safety measures had to be implemented during the course of field activities, to prevent unexpected hazardous energy release. In fact, proper lockout/tagout (LO/TO) practices and procedures were developed, concurred with the Base Health and Safety Manager to safeguard workers from the release of hazardous energy.

Directions on Management of remediation waste were also included in the RAWP.

After the completion of the selected activities, and based on an aquifer Mass Budget Analysis evaluation

(February 2015, Appendix G), an optimized remediation strategy was developed, tailored to the specific critical areas and compounds. The goals of the additional activities, concurred with the U.S. Army Corps of Engineers, were to both improve the site conceptual model and to conduct the bioremediation using less ORC compound but focusing on site-specific areas that still required attention.

SECTION 1 – INTRODUCTION

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The specific objectives of the project integrations included:

• Conduct a Baseline groundwater sampling to assess local aquifer conditions;

• Six additional Monthly Groundwater Monitoring campaigns, including groundwater level measurements, purging and sampling operations and groundwater samples collection focused on monitoring the new ORC injection outcomes;

• Laboratory analysis of the collected samples and analytical results;

• Analytical data evaluation and assessment against applicable regulatory screening levels and evaluation of the effectiveness of the focused injection.

Some deviations occurred to the above detailed plan (detailed in the following paragraph), which included a further extension of the monthly monitoring events to allow gathering sufficient data required to support statistical analysis and confirm concentrations decreasing trends and exclude the need for additional use of ORC compounds.

This Remediation Report provides a summary description of the environmental background of the Site, an overview of site conditions prior to the implementation of the ORC injections, and a description of all the field and laboratory activities associated with the remedial strategy delineated to address the site

Constituents of Concern (COCs).

The findings of the groundwater monitoring activities performed under this project are presented in terms of time-trends, distribution maps and diagrams, to provide lines of evidence of the ORC injection effectiveness. The natural attenuation capacity of the aquifer is also discussed in this Remediation

Report (RR), based on the environmental data analysis. Suggested follow up actions required for the Site are provided at the end of the document.

1.2 Deviations from Remedial Action Work Plan

Field and laboratory activities conducted under this project were in line with the RAWP, with the exceptions detailed below.

1.2.1 Screened sections and well type

Well pairs were designed with screened sections positioned at different depths with respect to the intervals initially indicated in the RAWP [2.0-9.0 and 11.0-18.0 m. below ground surface (bgs)]; the actual screened sections were defined based on site-specific lithology observed during drilling.

Well NWP-07 was installed as a single well instead of a nested well pair due to local absence of the aquitard layer.

1.2.2 Optimization of the second ORC injection design

Based on the first five rounds of Groundwater Monitoring Events, the contaminated area appeared to be less extended than the treatment area and a very complex vertical anisotropy of the aquifer was observed (with the lower part of the aquifer showing a higher capability to receive ORC (less backpressure) compared to the upper).

Consequently, the second injection cycle designed was modified to focus remediation on the shallow part of the aquifer, approximately 2 meters vertical thickness starting from maximum groundwater level, as summarized below:

• A smaller treatment area was considered (approx. 850 m2 instead of 1.100 m2);

• The injection loading mass per each point was re-evaluated considering GW monitoring results;

[458084- FINAL] CH2M HILL SRL 1-3

• The number of injection steps was reduced due to reduced injection layer thickness.

Details are provided in Section 3.3.

1.2.3 Extension of the project duration to allow implementation of an optimized remediation strategy, tailored to the specific critical areas and compound

Upon completion of the monthly monitoring events, a general decreasing trend was observed for all

COCs, with the exception of Methyl tertiary butyl ether (MTBE), which showed erratic trends (results were already anticipated in a Technical Memorandum: CH2M HILL, July 2014).

A new baseline groundwater sampling campaign was conducted in January 2015, also including eight wells belonging to the Base monitoring network but installed in other areas of the Base, not related to the ORC injection intervention.

A Mass Budget Analysis was then conducted, based on the results of the additional sampling event conducted in January 2015 (focused on a specific analytical set, detailed in Section 3.5) that was combined to the normal analytical set applied to the other monitoring events conducted on site.

An optimized remediation strategy was then developed, initially including:

• The installation of an additional monitoring well;

• The injection of an additional ORC-A compound; and

• Six additional monthly monitoring events (from April 2015 to October 2015).

Based on actual aquifer conditions, the installation of a new well and another injection cycle were not deemed necessary, hence monitored natural attenuation only was considered adequate to support evidence of enhanced bioremediation of the aquifer.

1.2.4 Confirmatory sampling – duplicate batches for October 2015 events and focused sampling in November 2015

During the last two monthly events conducted on 1 October 2015 and 20 October 2015, in order to strengthen the conclusions of the study on natural attenuation of the dissolved constituents of concern, two batches of samples were collected at selected wells, installed within the source area (PZ.83.2, PZ83.3, PZ83.6 and PZ.83.7), and sent to two laboratories: R&C Lab and Theolab.

One focused sampling event was conducted on 27 November 2015, when one well was sampled

(PZ.83.3, within the source zone area); laboratory analyses focused on selected constituents only (as further specified in Section 3.5).

1.3 Regulatory Framework

The scope of work was implemented in accordance with the Legislative Decree n. 152 dated 3rd April

2006 – “Norme in materia ambientale” (D.Lgs.152/06), Legislative Decree n. 4, dated 16th Juanuary 2008

“Ulteriori disposizioni correttive ed integrative del Codice dell'Ambiente” (D.Lgs. 4/08) and Ministerial

Decree 22 October 2009 “Procedure per la gestione dei materiali e dei rifiuti e la bonifica dei siti e delle infrastrutture direttamente destinati alla difesa militare e alla sicurezza nazionale”. Onsite actions such as monitoring well installation, groundwater sampling and substrate injection complied with those substantive requirements that were deemed applicable or relevant and appropriate. Offsite actions, such as offsite waste disposal, complied with both administrative and substantive requirements.

Italian legislation requirements were addressed by field and laboratory activities performed at the Site.

In particular, the legislative framework for this project is represented by:

1-4 CH2M HILL SRL [458084- FINAL]

• Legislative Decree n. 152 dated 3rd April 2006 – “Norme in materia ambientale” (D.Lgs.152/06);

• Legislative Decree n. 4, dated 16th Juanuary 2008 “Ulteriori disposizioni correttive ed integrative del

Codice dell'Ambiente” (D.Lgs. 4/08); and

• Ministerial Decree 22 October 2009 “Procedure per la gestione dei materiali e dei rifiuti e la bonifica dei siti e delle infrastrutture direttamente destinati alla difesa militare e alla sicurezza nazionale”.

Field activities were conducted based on the regulatory requirements described in Attachment 2, Title V, Part IV of D.Lgs 152/06, potential contamination of groundwater was evaluated against the screening values indicated in Table 2, Attachment 5, Title V, Part IV of D.Lgs 152/06. Based on the characteristics of the target area, the reference limits considered are those set for commercial and industrial sites. Finally, during the investigation activities a limited amount of waste was produced (consisting of soil extracted during drilling, decontamination wastewater and water purged from the wells). These materials, which are now considered as a waste by current Italian regulation, were temporarily stored in dedicated containers and subsequently disposed of in agreement with applicable Italian regulations.

The field activities has been conducted following the H&S Italian legislation in charge (D.lgs. 9 aprile

2008, n. 81.).

1.4 Document Organization

This report is structured as follows:

• Section 1 presents the project scope and objectives, deviations from the RAWP, the applicable regulatory framework and the document outline;

• Section 2 provides the general environmental setting of the Base area summarizing geology, hydrology, hydrogeology, and groundwater background conditions. A description of the selected

Remedial Approach is also given;

• Section 3 summarizes field activities conducted at the site (ORC injection cycles, groundwater monitoring wells installation and groundwater sampling and analysis);

• Section 4 describes management of wastes associated with the activities conducted as part of this project;

• Section 5 presents, combined with an update of the hydrogeological site model, the results of the remedial activities, including a statistical evaluation of chemicals concentrations in groundwater;

and

• Section 6 presents conclusions and recommendations.

SECTION 2

[458084-FINAL] CH2M HILL SRL 2-1

General Environmental Setting and Site

Background

2.1 Site Setting

The subject site is located within the Dal Molin Airfield, approximately 2 kilometers (km) north of the city center of Vicenza, in the Italian Region of Veneto. Site POL Point 83, located in the western portion of the airfield, to the west of the former runway and to the south of Building 76 (Figure 2-1), has been used as a vehicle refueling station before being demolished as part of the construction activities for the development of the new multiple facility complex at the former Dal Molin Airfield.

When the site was active, fuel was stored in two Underground Storage Tanks (USTs), having capacity of

15’000 (UST 83a) and 10’000 (UST 83b) liters, which were used to store diesel fuel and unleaded gasoline for vehicle refueling. Both USTs were cleaned and gas-free certified in June 2009, and subsequently removed in June 2009.

Results of direct surveys conducted at POL Point 83 before 2012 indicated that the site potentially interested by environmental issues covers a total area of approximately 500 square meters (m2).

2.2 Local Geological and Hydrogeological Features

Local geology consists of sequences of sandy clays with peat deposits from a depth of 0 to 130 m bgs, thickening with increased depth. A sequence of conglomerates and pebbles, decreasing in thickness towards the South, is present from 135 to 145 m bgs. A primarily clayey sequence, with intercalated and possibly non-continuous conglomerate/pebble beds, is present from 145 to 220 m bgs. Soils encountered during execution of the preliminary investigation can be generally categorized as brown / grey medium fine grain sandy, interbedded with clayey silt, sometimes sandy. The maximum depth drilled as part of the preliminary investigation was 7.2 m bgs. In particular, the stratigraphy of POL Point

83 area is hereafter described:

• “Stratum R” and “Stratum I” – Fill material consisting in medium-coarse (sand and gravel – “stratum

R”) to medium fine soil (silty sand and silt with sand – “stratum I”) from ground surface to a depth varying from 0.3 m bgs;

• “Stratum II” – brown/grey silty clay or silt, clayey sandy or slightly sandy silt, from a minimum of 1.0 m bgs to a maximum depth of 6.0 m bgs; and

• “Stratum III” – from a minimum of 3.0 m bgs to the maximum investigated depth (11 m bgs):

brown/grey medium to fine grain sand, sometimes silty gradually turning up to gravelly sand at 8-10 m bgs.

The hydrographic element of highest interest is the Bacchiglione River. The river is formed by the springs in the Dueville and Villaverla Municipalities, and is initially called “Bacchiglioncello”.

Immediately upstream of the Vicenza town it receives the water from the Leogra-Timonchio basin (from

Mount Pasubio) and changes its name to Bacchiglione. After Vicenza, it also receives water from the

Retrone River, the Astichello stream, the Astico-Tesina stream and the Tesina Padovano River.

As far as groundwater is concerned, the preliminary investigation implemented in the POL Point 83 area revealed that groundwater table’s elevation fluctuates between 31.95 and 33 m amsl, with average depth to water ranging between 3.6 and 5.6 m bgs.

SECTION 2 – GENERAL ENVIRONMENTAL SETTING AND SITE BACKGROUND

2-2 CH2M HILL SRL [458084- FINAL]

The results obtained from the elaboration of the above data indicate a main groundwater flow direction from East-South-East to West-North-West (on average approximately 75° counter clockwise from a

North direction).

2.3 Historical Environmental Background

A short summary of the environmental background for POL83 site is provided below.

Characterization activities

The initial environmental investigation activities at the Site were performed at the USTs removal time, and included soil samples collection from the USTs excavation sidewalls and bottoms.

Subsequent environmental investigation activities were performed in 2009 by drilling of seven soil borings and installation of three piezometers, combined with the collection and laboratory analysis of soil and groundwater samples, which resulted in regulatory screening levels (CSC) exceedances for:

• Light Hydrocarbons (C≤12), Heavy Hydrocarbons (C>12) and Lead in soil;

• Total Petroleum Hydrocarbons (TPHs), Benzene, Ethylbenzene, Toluene and Xylenes. Methyl tertiary butyl ether (MTBE) was also detected in concentrations above the limits set by the Istituto Superiore di Sanità prot. N. n. 0043699/I.A.12 del 12/09/06, equal to 40 μg/l).

Further investigations, driven by the outcomes of the 2009 characterization, allowed delineating the subsoil contamination extent and magnitude (for details: AMEC, 2009). Based on the geological, hydrogeological and chemical data gathered for the Site, secondary sources of potential contamination were identified (Figure 2-2):

• In soil: two sources being located in the USTs removal excavation area (COCs: Lead and heavy hydrocarbons) and one source located in the vicinity of former Building 84 (COCs: light and heavy hydrocarbons);

• In groundwater: two sources, with plumes extending in the area underneath and downgradient the residual sources in soil. The two sub-areas were identified as Area 1 (300 m2) and Area 2 (158 m2, comprising the original excavation -now backfilled) for USTs removal.

The plume area in the shallow aquifer was defined as the most impacted portion of the plume, located near the excavation area, in the proximity of monitoring wells PZ83-2, PZ83-3, PZ83-6 and PZ83-7.

Human Health Risk Assessment

A site-specific Human Health Risk Assessments (HHRA) was conducted, and Risk Based Clean up Goal

(CSR, Concentrazione Soglia di Rischio) were calculated, which resulted in the following conclusions:

• The residual contamination in soil was associated with acceptable risks to human health (for future workers on site), also in relation to the soil-to-groundwater leaching and groundwater transport pathways;

• Groundwater concentrations indicated the need for a prompt remedial effort to guarantee the respect of the applicable limits (CSCs and/or Italian Health Institute threshold values) at the Point Of

Compliance (POC1).

Details on the site-specific HHRA can be found in AMEC, 2010a, AMEC, 2010c and AMEC 2014 reports.

Since Project Plan/Engineering Assessment (“Progetto Operativo di Bonifica” – POB) and Site-Specific

1 Piezometer located next to the downgradient boundary of the site assumed, as per Italian legislation, as the point where groundwater quality meets the regulatory screening levels criteria.

[458084- FINAL] CH2M HILL SRL 2-3

HHRA was approved by the local Italian authorities following the beginning of the project, achieving clean up goals following the ORC injections was not guaranteed.

Safety measures

Safety measures, implemented in order to avoid migration of contaminated groundwater outside the site (plume control), consisted in the installation of a Pump and Treat (P&T) system, designed considering the characteristics of the identified constituents in groundwater, their concentrations and distribution in the monitoring wells, and the results of pumping tests conducted in one of the extraction wells.

The P&T system consisted of:

• Four extraction wells (GW83-1; GW83-2; GW83-3 and GW83-4) located close to the western boundary of the site;

• Mutual distance between extraction wells was set equal to 10 m, allowing in favor of precaution the overlapping of well capturing ranges;

• Each well, 220 mm in diameter, 10 m deep, was equipped with a PVC tube (DN 160 mm) and with a submersible pump, operating with a maximum flow rate of 1 m³/h;

• A treatment plant was designed to treat a total flow rate of 4 m³/h of groundwater.

The system started its operation in August 2010 and was stopped in January 2015.

An exhaustive description of the safety measures realized can be found a dedicated document (AMEC, 2010b).

Field pilot test of ORC injection

To evaluate the actual feasibility and effectiveness on a site-specific basis, in September 2010 a field pilot test of ORC injection was performed at five locations in the surroundings of PZ83-3 (covering an area of 25 m2). Monthly monitoring for the target analytes (BTEX, TPH and MTBE) and for performance indicators (such as pH, redox, dissolved oxygen, conductivity, temperature, nitrates, sulfates, divalent iron and methane) was then conducted between October of 2010 and May 2011.

Prior to injecting the slurry, a soil boring with continuous core recovery down to 9.6 m was realized in the vicinity of monitoring well PZ83-3, in order to identify site-specific stratigraphy and define the optimal injection depths.

The overall objective of the pilot test was to assess the performance of ORC on a site-specific basis, with respect to the following aspects:

1) Achievement of sufficient oxygenation in the target zone (increase of dissolved oxygen following injection) and assessment of the effectiveness of oxygen delivery to the target treatment zone;

2) Shifting of the oxidation-reduction potential towards more aerobic conditions following the injection;

3) Assessment of the reduction in MTBE, BTEX and TPH concentration achieved over time;

4) Gathering information for full-scale treatment design (e.g. time to ORC exhaustion; effective area of influence of the injection, etc.).

2.4 Selected Remedial Approach

The remedial approach for the site was designed based on the site characteristics, compound properties and contamination spatial distribution, as well as considering the good results of the pilot test

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conducted in 2010 combined with the results coming from the groundwater flow model developed for the site.

The following remedial actions were proposed (AMEC, 2011), in order to reduce the concentration of the COCs within the Risk Based Threshold Concentrations (CSRs) calculated with the site-specific HHRA:

• Source zone: implementation of a full scale ORC injections intervention, following a tiered strategy based on three cycles of ORC compound delivery, with the second and the third cycles to be adjusted according to the monitoring results of the first one;

• Groundwater plume: operation and monitoring of the existing P&T plant to prevent contaminant diffusion outside the site boundaries and to reduce the residual contaminant mass (plume control);

• Optimization of the monitoring wells network, through the installation of five additional monitoring wells for the monitoring of the ORC intervention and COCs and for the in depth examination of local flow direction and the plume delineation. The integration of the monitoring network was also designed to better develop the target areas, the number of injections and the mass of ORC product to be used after the first round of injections;

• Implementation of a dedicated groundwater monitoring program, developed aimed at achieving different frequency and target analytes, depending on the monitored area:

• To verify effectiveness of P&T system: monitor on a monthly basis the inlet and discharged water at the treatment plant, and conduct sampling and analysis of groundwater extracted at both the four extraction wells and from selected monitoring wells, to be conducted with quarterly frequency.

• To assess the efficiency of the ORC full scale intervention: conduct sampling and monitoring on selected monitoring wells on a monthly basis, with a dedicated analytical program, focusing on the site-specific COCs, as well as the indicators required to confirm ORC action on enhanced bioremediation. The analytical program also included Lead, for which ORC injections do not provide active treatment. Only one exceedance of CSR limits was, in fact, recorded for this parameter, for which continuous monitoring is considered sufficient to evaluate potential trends, also considering the presence of the hydraulic barrier.

SECTION 3

[458084-FINAL] CH2M HILL SRL 3-1

Field Activities Summary Description

This section provides a summary description of all the activities conducted as part of the remediation project of POL 83 site, which are also listed in chronological order within Table 3-1.

3.1 Utility Avoidance and UXO Avoidance Activities

Utility avoidance activity was conducted with Soil vacuum excavation method at each injection point and new monitoring well locations down to a maximum depth of two meters. Excavated soil was temporarily containerized and then used for backfilling once underground utilities inspection is completed. Actual locations of injection points and new wells are shown on Figure 2-2.

An Unexploded explosive ordnance (UXO) avoidance investigation was also performed in proximity of five drilling points (INJ_30, INJ_38, INJ_39, INJ_40 and NWP-05), located in the Source Area A1 (see

Figure 2-2), in proximity to but external to the area that had already been remediated. The purpose of this investigation was to ensure that drilling activities, required to implement the ORC injection system and to install new monitoring wells, could be safely completed.

The avoidance activity was, conducted under supervision of a CH2M HILL representative.

A shallow survey (down to 1 m bgs) was first conducted by means of a metal detector equipment, centered on drilling locations. Once completed the shallow survey, a deep UXO avoidance was also performed for each one of the drilling points, previously indicated. The first meter was drilled by means of a screw auger: a FEREX magnometer probe was then inserted in the drilled hole, to allow performing avoidance of the subsequent 2 m, in order to advance with the auger. This procedure was then repeated down to the maximum investigated depth. Deep UXO avoidance was conducted down to 7 m bgs, with an avoidance range up to 8 m bgs. Field activity were recorded on related filed forms reported in

Appendix C.

In addition to the activities above described, at one drilling location (INJ_24, located in the Injection plume area A3) an additional safety procedure, not initially planned but covered by the HASP, was applied. Because the planned location of the injection point, during field work advancement, resulted to be too close to an energized underground line, proper lockout/tagout (LO/TO) practices and procedures were adopted to safeguard workers from the release of hazardous energy.

3.2 Wells Installation

The existing monitoring network was integrated by the installation of five new monitoring wells, which took place between 23 and 29 October 2012.

Drilling, conducted using a dry continuous coring roto-percussion technique2, reached the depths defined in the RAWP; boreholes features (including corer and temporary casing diameters) are detailed in Table 3-2.

Borehole locations, shown on Figure 3-1, as well as the new wells completion schemes were defined to coverall critical zones and confirm the effectiveness of the selected remedial approach:

• NWP-05: nested well pair, installed within the Source Area;

2 To avoid cross contamination and/or percolating water through potentially impacted areas, fluids were not used during drilling operations;

drilling activities were thus in compliance with D.Lgs 152/06 requirements

SECTION 3 – FIELD ACTIVITIES SUMMARY DESCRIPTION

3-2 CH2M HILL SRL [458084- FINAL]

• NWP-06: nested well pair, installed upgradient of the Plume Area but cross-gradient the Source

Area;

• NWP-07: single well installed cross-gradient the P&T system;

• NWP-10: single well, installed upgradient of the Source Area; and

• NWP-11: nested well pair, installed cross-gradient the Plume Area.

Each wellhead was finished with a flush mounted, cast-iron traffic box. Details on wells diameter and screen position are provided in Table 3-2. Boring logs are included in Appendix A; a photographic documentation of field activities is presented in Appendix B.

Well development was conducted on all new groundwater monitoring wells, in order to remove sediments from the casing and filter pack, and to ensure their maximum yield. For this purpose, water was extracted from the well using a submersible pump, operated at a flow rate of 1 liter per minute. The pump used for well development was decontaminated between each well, to avoid cross-contamination occurrence. Field activity was recorded the field forms reported in Appendix C.

3.3 Topographic Surveys

A first topographic survey was conducted on 10 April 2013 by Adastra S.r.l., to provide a homogeneous set of X-Y-Z coordinates of 50 locations, including the newly installed monitoring wells and the 40 injection points. Measurements were as follows:

• X and Y coordinates were determined with 1 cm accuracy. Geographical coordinates were defined according to the UTM (WGS843) Zone 32 reference system;

• Z elevation of the groundwater monitoring wells was taken at both the top of the casing and the ground surface and measured values were referred to the mean sea level. Accuracy was 1 mm.

A second topographic survey round was the conducted by the same firm on 23 October 2014, based on the same coordinates reference system and applying the same precision and accuracy criteria. The purpose of the new survey was to define X, Y and Z coordinates of all wells belonging to the Base monitoring network (73 points, including the new wells installed in October 2012 under this project, in order to obtain a homogeneous set of data).

Coordinates for all the surveyed points are provided in Table 3-3 (injection points) and Table 3-4

(monitoring wells).

3.4 Injection Activities

3.4.1 Injected compound

As described in the RAWP, CH2M HILL used the ORC-AdvancedTM compound (ORC-A) provided by the teaming company Regenesis, which possesses a higher oxygen content (17% O2) and slower release when compared to the one adopted by AMEC during the pilot test (14.5% O2).

The purpose of adopting ORC-A compound was to minimize the amount of product to inject and the possibility to perform two injection campaigns instead of originally planned three.

3 UTM: Universal Transverse Mercator

WGS: World Geodetic System

[458084- FINAL] CH2M HILL SRL 3-3

3.4.2 Injection Methodology

In order to ensure proper substrate distribution and contaminant loading, the Oxygen-Release

Compound-Advanced was introduced into the subsurface matrix via Direct Push (DP) methods, using the bottom-up method and a 30 cm screen interval.

Potable water needed for diluting or solubilizing the ORC-A was provided by the Base. Documentation of field activities is provided by Appendix B (photographic documentation) and Appendix C (field forms).

During injection activities, when excessive mounding occurred and reagent surfacing was observed, a temporary interruption of the injection operations was necessary.

This methodology was applied in both the first and the second injection cycles.

3.4.3 First Injection Cycle Design

The first injection cycle (December 2012) occurred via 40 injection locations, distributed among three injection areas (see Figure D1 of Appendix D), delineated in accordance with the AMEC, 2011 remedial design:

• Source Area A1 (300 m2): 11 injection points;

• Source Area A2 (150 m2): 7 injection points;

• Plume Area A3 (635 m2): 17 injection points;

• Zone between Source Area A2 and Plume Area A3: 5 injection points.

A total of 3,945.8 kg of pure product (approximately 16,000 to 20,000 liters of slurry) has been injected;

the injection loading mass, which was modified from the AMEC, 2011 remedial design, increasing the injected material from 65/74 kg per point to approximately 98 kg per point, was delivered by means of 12 injection steps covering an injection layer four meters thick (starting from max groundwater level, thus extending from 4.5 to 8.5 m bgs).

Appendix D summarizes the most relevant technical data characterizing the first ORC injection cycle and provides details on the number and location of injection wells.

3.4.4 Second Injection Cycle Design

Based on the outcomes of the first group of monthly groundwater monitoring events, the second ORC injection cycle (June 2013) was modified with respect to the first one, so that the new design was better targeted to the actual aquifer portion requiring remediation. In fact, intensive treatment of areas upgradient of the former USTs location and downgradient of monitoring wells PZ.83-6 and PZ.83-7 was deemed not necessary, being those areas not impacted or with a very low impact.

Furthermore, the local anisotropy pattern of the aquifer, as inferred from field observations, was quite complex, with deeper aquifer strata characterized by a higher permeability (hence a higher capability to receive ORC) if compared to shallower aquifer strata.

Consequently, the second injection cycle occurred via 30 injection locations, located as shown on

Figure D2 of Appendix D:

• Source Area A1 (300 m2): 7 injection points;

• Source Area A2 (150 m2): 7 injection points;

• Plume Area A3 (635 m2): 12 injection points;

• Zone between Source Area A2 and Plume Area A3: 4 injection points.

3-4 CH2M HILL SRL [458084- FINAL]

Appendix D summarizes the most relevant technical data characterizing the second ORC injection cycle, including details on injection wells used for the purpose.

The total amount of injected product was the same as the one used for the first inject cycle (3,945.8 kg of pure product), but was more focused on the Source A2 area (which received 1.150 kg of product) and on the Plume Area A3 (1.350 kg of product). A total surface of 850 m2 was covered, instead of 1.100 m2, distributing the product along a thinner interval (between 4.5 and 6.5 m bgs).

3.5 Groundwater Monitoring and Sampling Activities

In order to evaluate the effectiveness of ORC injections and assess progress of the enhanced bioremediation intervention, groundwater quality was monitored adopting the following strategy:

• Execution of a baseline monitoring campaign, to depict aquifer conditions before the implementation of the selected remedial approach;

• Completion of groundwater monitoring campaigns, with monthly frequency, to assess the effects of the first ORC injection cycle and tune subsequent remediation steps accordingly;

• Completion of a second group of monthly groundwater monitoring campaigns, subsequent to the second ORC injection cycle.

Based on concentration time-trends and on a mass budget analysis, the prosecution of monthly monitoring campaigns was deemed necessary, as well as a new baseline monitoring campaign required to depict aquifer conditions also in Base areas upgradient of the intervention zone.

3.5.1 Baseline Groundwater Monitoring (November 2012)

The first Baseline Groundwater monitoring and sampling campaign took place between 13 and 15

November 2012. A total of 20 samples were taken, at the following locations (see Figure 3-1):

• Monitoring points, including both single wells and nested well pairs, located in the Source Area

Plume: PZ.83.1, NWP-05A and NWP-05B; NWP-06A and NWP-06B; and NWP-10;

• Four single wells located in the Plume Area: PZ.83.2; PZ.83.3; PZ.83.6 and PZ.83.7;

• Three single wells located downgradient of the Plume Area: PZ.83.5; PZ.83.12 and PZ.83.13;

• One nested well pair located cross-gradient the Plume Area: NWP-11A and NWP-11B;

• Three single wells installed in line with the P&T system: PZ.83.8; PZ.83.10 and PZ.83.11; and

• Two single wells installed cross-gradient of the hydraulic barrier: PZ.83.9 and NWP-07.

The analytical plan applied to all samples (also summarized in Table 3-5) included:

• Site Specific CoCs: BTEXS, TPH, MTBE;

• Lead, which is a site-specific constituent but is not addressed by the ORC compounds injected as part of the selected remedial intervention;

• Geochemical indicators: pH, Iron (Fe2+), Nitrates (NO3-), Sulfates (SO4 2-), Manganese; Ammonium and

Total Phosphorus (Total P).

[458084- FINAL] CH2M HILL SRL 3-5

3.5.2 Monthly Monitoring Events (December 2012 - October 2015) Three groups of monthly-spaced events were completed at the site, for a total of 20 campaigns (against the15 events that were anticipated in the RAWP):

• First group of monthly-spaced events: six campaigns, between December 2012 and May 2013

(sampling dates reported in Table 3-7) conducted to assess the effects of the first ORC injection cycle;

• Second group of monitoring events: eight campaigns between July 2013 and May 2014 (sampling dates reported in Table 3-7), conducted to assess the effects of the second ORC injection cycle;

• Last group of monthly-spaced events: six campaigns, between April and October 2015 (sampling dates reported in Table 3-7), conducted as an extension of the monitoring program, to confirm the time-trends of measured concentrations.

The analytical plan included the site-specific COCs for each of the 20 events; lead and the geochemical indicators were then tested for in five of the events (applying approximately a quarterly frequency – see

Table 3-6 for details).

3.5.3 Focused Confirmatory Event (November 2015)

The analytical plan applied to the sample collected from PZ.83.3 included a selection of site-specific

COCs (TPHs, with petroleum hydrocarbon fractions fingerprinting, and BTEXS).

3.5.4 Basewide Groundwater Monitoring (January 2015)

The second Baseline Groundwater monitoring and sampling campaign took place between 21 and 23

January 2015. A total of 27 samples were taken (see also Table 3-5), including:

• All monitoring points (single wells and nested well pairs) already sampled during the November

2012 baseline campaign, with the exception of NWP-10, which was not sampled;

• Eight single wells installed in other areas of the Base, not related to the remediation site: PZ4, PZ7, PZ8, PZ9, PZE11, PZE12, PZ15, and PZ16 (see Figure 3-1 for wells location).

The analytical plan applied to all samples included:

• Site Specific COCs: BTEXS, TPH, MTBE;

• Lead;

• Geochemical indicators: pH, Iron (Fe2+), Nitrates (NO3-), Sulfates (SO4 2-), Manganese; Ammonium and

Total Phosphorus (Total P);

• Additional parameters: Alkalinity; Ca; Mg; K; Na; Fluoride; chloride; bromide; methane.

3.5.5 Field Operations

Prior to the beginning of sampling operations, measurement of water level were conducted at all accessible locations during the groundwater monitoring events. Depth to water was measured with respect to the well head point on the top of the casing, for which Z elevation was surveyed (see Section

3.3). Manual measurements were conducted using an electronic level indicator, with 1 cm accuracy, and recorded on dedicated field forms (Appendix C).

3-6 CH2M HILL SRL [458084- FINAL]

Groundwater purging at the well selected for sampling and analysis was then conducted (R&C LAB) applying the US EPA low-flow protocol: water was extracted from the well at a pumping rate of approximately 1 liter/minute to minimize disturbance and turbidity. A multiparametric probe calibrated according to manufacturer’s instructions was connected to a flow-through cell and used to continuously measure chemical-physical parameters required to characterize aquifer conditions (dissolved oxygen, field measured oxidation-reduction potential (ORP), pH, specific conductance, and water temperature).

Upon stabilization of these parameters, which were recorded on the field forms (Appendix C), groundwater samples were collected using the laboratory-prepared containers (vials and bottles, with preservative if required), which were then placed in designated containers and stored at 4°C.

In order to ensure a unique identification of all samples, for correct tracking of sample containers from the field to the laboratory, a labeling protocol was applied for all the samples collected under this project; as an example: PZ83.2_12-1 indicated the normal sample collected at well PZ83.2, in 2012, during the first round of sampling events.

Field Duplicate (FD) samples were taken during each sampling event, based on 10% of all collected samples and were tested for the full set of analytes previewed for the normal samples; analytical results were used to assess precision of the sample collection process.

SECTION 4

[458084-FINAL] CH2M HILL SRL 4-1

Waste Management

Drilling cuttings and soils, considered by the law as waste because extracted from contaminated sites, were designated for off-site disposal.

Water generated during decontamination procedures as well as purged water extracted as part of monitoring wells sampling procedures was also collected and stored in dedicated containers, labeled as follow: “Water potentially contaminated, waiting for characterization, keep away, potentially hazardous”.

The collected Investigation Derived Waste (IDW) was properly disposed of at an off-site, licensed treatment and/or disposal facility at the end of the investigation activities. Waste disposal certificates are included in Appendix E.

SECTION 5

[458084-FINAL] CH2M HILL SRL 5-1

ORC Injection Results

5.1 Local Geological and Hydrogeological Features

5.1.1 Geological Characteristics

Appendix A presents the boring logs recorded during drilling activities associated with the installation of the new…