S P Assessment of contamination by petroleum hydrocarbons ...migrate and contaminate groundwater,...

STUDY PROJECT

Assessment of contamination by petroleum

hydrocarbons from oil exploration and

production activities in Aguarico, Ecuador.

Supervisor: Dr. ret. nat. Gabriele CHIOGNA

Author: B.Eng. Pablo MERCHÁN-RIVERA

Mat. No.: 03668714

TECHNICAL UNIVERSITY OF MUNICH

FACULTY OF CIVIL, GEO AND ENVIRONMENTAL ENGINEERING

CHAIR OF HYDROLOGY AND RIVER BASIN MANAGEMENT

Technische Universität München 2017

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Disclaimer

I hereby certify that this Study Project titled "Assessment of contamination by

petroleum hydrocarbons from exploration and production activities in Aguarico,

Ecuador" has been composed by me and is based on my own work, unless stated

otherwise.

The information and statements asserted in this report are based on technical data,

as well as available information and materials which are part of arbitration processes. All

references and verbatim extracts have been quoted, and all sources of information have

been specifically acknowledged.

Date: _________________________ Signature: _________________________

Pablo Merchán-Rivera


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Content 1. ABSTRACT .............................................................................................................................................. 6

2. INTRODUCTION ....................................................................................................................................... 7

3. SITE OF STUDY ....................................................................................................................................... 9

3.1. Site history and configuration ....................................................................................................... 9

3.1.1. Climate ............................................................................................................................... 9

3.1.2. Geology ............................................................................................................................ 10

3.1.3. Hydrology and hydrogeology ........................................................................................... 11

3.1.4. Vegetation and fauna ........................................................................................................ 12

3.2. Socioeconomic conditions .......................................................................................................... 12

3.3. Contaminant sources, fate and transport ..................................................................................... 13

3.4. Human health and ecotoxicology ............................................................................................... 17

3.5. Environmental remediation strategies ......................................................................................... 17

3.6. Legal and regulatory framework ................................................................................................. 18

4. MATERIAL AND METHODS .................................................................................................................... 22

4.1. Environmental site assessment ................................................................................................... 22

4.1.1. Soil and water sampling ................................................................................................... 22

4.2. Conceptual site model ................................................................................................................. 24

4.3. Remediation technology selection .............................................................................................. 25

4.3.1. Decision making tree ........................................................................................................ 26

5. RESULTS AND DISCUSSION.................................................................................................................... 27

5.1. Contamination levels and source analysis .................................................................................. 27

5.1.1. Generic conceptual model ................................................................................................ 31

5.1.2. Exposure pathway conceptual model ............................................................................... 31

5.2. Remediation technology ............................................................................................................. 33

5.2.1. Soil and sediment remediation technology ....................................................................... 34

5.2.2. Groundwater remediation technology .............................................................................. 36

6. CONCLUSIONS ...................................................................................................................................... 38

6.1. Recommendations....................................................................................................................... 39

7. REFERENCES......................................................................................................................................... 41


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List of Figures

Figure 1. Structural section across the Orient Basin ........................................................................... 10

Figure 2. Typical values of hydraulic conductivity and permeability ................................................ 11

Figure 3. Generalized vertical cross section illustrating the infiltration of LNAPL and DNAPL ...... 15

Figure 4. API gravity of some hydrocarbon compounds .................................................................... 16

Figure 5. Flowchart of remediation technology selection process ..................................................... 26

Figure 6. TPHs average concentrations on different media according to analytical results ............... 30

Figure 7. Exposure pathway model .................................................................................................... 32

Figure 8. Decision making tree for soil remediation technologies ..................................................... 34

Figure 9. Decision making tree for groundwater remediation technologies ....................................... 36

List of tables

Table 1. Meteorological data of the study area.................................................................................... 9

Table 2. Characteristics of crude oil reserves on the field Shushufindi-Aguarico ............................ 10

Table 3. Life conditions in San Roque District, Shushufindi. ........................................................... 13

Table 4. General characteristics of crude oil ..................................................................................... 16

Table 5. Concepts of remedial strategies by function ........................................................................ 18

Table 6. Permissible levels for surface water and groundwater ........................................................ 19

Table 7. Permissible levels for soil and sediments ............................................................................ 20

Table 8. Permissible levels to muds and wastes from drilling........................................................... 21

Table 9. Characteristics of the multiparameter sensor ....................................................................... 23

Table 10. Characteristics of the photoionization detector (PID) ....................................................... 23

Table 11. Location of soil and water samples ................................................................................... 24

Table 12. Judgements in development of conceptual site models ..................................................... 24

Table 13. Identified reserve pits ........................................................................................................ 27

Table 14. Expected volume of reserve pits........................................................................................ 28

Table 15. Analytical results of soil samples ...................................................................................... 28

Table 16. Analytical results of sediments samples ............................................................................ 29

Table 17. Analytical results of groundwater samples ........................................................................ 29

Table 18. Analytical results of surface water samples ...................................................................... 29

Table 19. Analytical results of soil and surface water samples ......................................................... 30

List of annexes

Annex 1. Base map and location of AG-06

Annex 2. Site configuration well-site Aguarico 06

Annex 3. Sample location and suspected pit area

Annex 4. Screening Matrix for Soil Remediation Technologies

Annex 5. Screening Matrix for Groundwater Remediation Technologies

Annex 6. Detailed evaluation of possible remediation technologies for soil

Annex 7. Detailed evaluation of possible remediation technologies for Groundwater

Annex 8. Generic conceptual model of the site

Annex 9. Photographic record

Annex 10. Laboratory results


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1. Abstract

Contamination from oil exploration and production activities was investigated in

the site Aguarico 06, a well site in the northern Ecuadorian Amazon. An environmental

site assessment was performed to assess the pollution and to propose a remediation

technology. Soil and water samples were taken and included in the general assessment.

Concentrations above the permissible levels of petroleum hydrocarbons in soil, sediments

and groundwater are the main concern. Four reserve pits are considered as the main source

of contamination because the content of the pits have seeped underneath the pit limits,

reaching lower soil layers and the groundwater table. Additionally, LNALP spreads

vertically as result of fluctuation on the water table during rain periods. 53 in situ and ex

situ technologies were evaluated to remediate both soil (28 technologies) and

groundwater (25 technologies). Biopiles are recommended to treat soil. To remediate

groundwater, it is recommended air sparging. The performance of most of the

technologies evaluated in this study is reduced due to geological and hydrogeological

condition of the study area.


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2. Introduction

The eastern Ecuadorian region is a significant zone for oil exploration and

production activities since the 1970s (Baynard, Ellis, & Davis, 2013; Falconí, 2002; San

Sebastián & Hurtig, 2004). Most of these economical activities are found within Napo,

Pastaza, Orellana, and Sucumbíos Provinces (Moolgavkar, Chang, Watson, & Lau,

2014). In addition, the region consists of more than 100000 km2 of tropical rainforest,

contains one of the most diverse collections of plants and animals in the world, and is

home of about 500000 people (San Sebastián & Hurtig, 2004, 2005).

During oil exploration and production activities, accidents, spills, and leaks from

processes and byproducts from oil industry are produced and discharged into the

environment (Ou, Zheng, Zheng, Richardson, & Lam, 2004; Teng, Feng, Song, Wang, &

Li, 2013). The impact of the polluting processes depends on the environmental practices

and the technology used by oil companies. In Ecuador, oil industry practices have been

questioned (San Sebastián & Hurtig, 2004). More than 30 billion gallons of toxic wastes

and crude oil have been discharged in Ecuadorian eastern region (Moolgavkar et al.,

2014).

Human health and ecosystems can be in risk due to released hydrocarbons (Teng

et al., 2013) and produced wastes by the oil industry (Vidaković, Papeš, & Tomić, 1993).

Petroleum hydrocarbons and heavy metals can impact in ecosystems reducing the quality

of resources and affecting them due to their toxicological and health implications into the

food chain (Adeniyi & Afolabi, 2002). Depending on local conditions, contaminants can

migrate and contaminate groundwater, which could be a source of drinking water (Teng

et al., 2013). Organic contaminants, such as non-aqueous phase liquids or dissolved

solutes, may pollute the environment as contamination plumes from the source zone

(Essaid, Bekins, & Cozzarelli, 2015).

From 1964 to 1990, Texpet Company (Texaco), which merged with a Chevron

subsidiary in 2001, operated in east Ecuador exploring and producing petroleum

(Procuradoría General del Estado, 2015). During that time, Texpet drilled and operated

356 oil wells and opened 1000 oil pits (Ministerio de Relaciones Exteriores y Movilidad

Humana, 2015). As part of the Concession Area, Aguarico 6 was one of the oil field sites

where Texpet operated exclusively (Procuradoría General del Estado, 2015). Drilling and

workover wastes discharged to well site pits and the oily produced water discharged from

production stations where the most damaging activities performed by the company

(Goldstein & Garvey, 2014). Practices followed by the oil company were contrary to

environmentally protective methods at that time in both the United States and Latin

America (Kaigler, 2013). The balance in social and environmental terms is criticized by

environmental organizations and human rights defenders (Jochnick, Normand, & Zaidi,


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1994; Kimerling, 1993). Numerous litigation process began since 1993 between local

communities and the company (Fontaine, 2013; Ministerio de Relaciones Exteriores y

Movilidad Humana, 2015; Procuradoría General del Estado, 2015). Additionally, several

investigations have demonstrated that the place was polluted by oil exploration and

production activities and it is still present in the zone and migrating from the source point,

impacting negatively to close localities (Goldstein & Garvey, 2013, 2014; Kaigler, 2013;

Ministerio del Ambiente, 2017).

To remediate and evaluate the conditions of the place it is important to develop

an assessment of contamination based on the actual information, only therefore we can

propose effective remedial actions. Remediation actions will depend on many factors and

their efficiency will significate the improvement of life conditions of people, and the

regeneration to acceptable levels of the whole ecological system. However, none

exhaustive environmental assessment about this place has been published, and the

information may be complex to contrast and evaluate.

The objective of this project is to investigate and assess concerns with respect to

contamination by petroleum hydrocarbons in the site Aguarico 06. This is expected to

screen potential environmental risks and pollution sources related to the activities of oil

industry, which may be affecting neighboring communities. Ecuadorian legal framework

is assessed and in order to define tolerable contamination limits and action mechanisms.

Additionally, based on the assessment, the project pretends to identify and recommend

an appropriate environmental remediation technic as an alternative to clean up the

identified pollution.

The study project was executed together with the Chair of Hydrology and River

Basin Management of the Faculty of Civil, Geo and Environmental Engineering.

Database of environmental liabilities was formally given by the Ministerio del Ambiente

del Ecuador (Ministry of Environment of Ecuador) and is a fundamental part of this

research. Likewise, bibliographic information and documents from arbitration processes

were reviewed and evaluated during the development of this study.


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3. Site of Study

3.1. Site history and configuration

The well site named Aguarico 06 (AG-06) was drilled in 1974 to be used as an

extraction well. Subsequently, it was temporally closed in 1986 by Texpet, and re-opened

by the company as a reinjection well (Worldwide Reporting, 2015) and no other company

operated on the platform (Procuradoría General del Estado, 2015). The site is part of

Shushufindi Canton in the province of Sucumbíos.

The platform is located at the northern zone of the Concession Area (Annex 1),

and placed at the top of a small hill and has polygonal shape of 2300 m2 with 200 m of

perimeter, approximately. The wellhead is located in the center of the platform). No

barriers or fences close the platform and the access is done through a dirty road. The

access to AG-06 can be done by car at approximately one hour from city of Nueva Loja

(also known as Lago Agrio). Annexes 1 and 2 include a location map and a map of site

configuration, respectively. Annex 7 contains a photograph record.

3.1.1. Climate

The study area is part of the Amazon region, which is a tropical rainforest climate

(megathermal). It is characterized by an average temperature around 25°C and an annual

precipitation over 3000 mm (INAHMI, 2016). The relative humidity is over 90% and the

solar irradiance is low (Municipio de Shushufindi, 2015). Table 1 summarizes the general

meteorological data of the place.

Table 1. Meteorological data of the study area (INAHMI, 2016)

Parameter Value

Annual precipitation

(annual variation)

3277.4 mm

(5%)

Days with precipitation during the year 256

Maximal precipitation in 24 hours

(month)

105.0 mm

(November)

Annual average temperature

(anomaly)

26.2°C

(-0.4)


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3.1.2. Geology

The platform is part of the field Shushufindi-Aguarico located in the Oriente Basin

of Ecuador. The regional geology of the Oriente Basin is characterized by Sub-Andean

foothills and foreland basin between the Putumayo Basin (Colombia) and the Marañon

Basin (Peru). AG-06 is located in the center of the Shushufindi-Sacha Corridor, which is

the result of an inversion of a trend of Upper Triassic to Lower Jurassic half-grabens

(Baby, Rivadeneira, Christophoul, & Barragán, 1999).

Figure 1. Structural section across the Orient Basin

(Baby, Rivadeneira, & Barragán, 2004)

Shushufindi and Sacha fields are the most important reserves of light and medium

crude oil (Baby et al., 2004). General characteristics of the field and crude oil, shown in

Table 2, are a key factor in order to understand the contaminant and its behavior into the

environment.

Table 2. Characteristics of crude oil reserves on the field Shushufindi-Aguarico

(Baby et al., 2004)

Discovery year 1969

API gravity1 [°API] 24° – 32°

Sulfur content 0.52 – 0.64 % and 1.10 – 1.22 %

Proven oil reserves [barrels] 1590 millions

Extraction [barrels] > 1000 million (until 2002)

1 API gravity is a hydrometer scale used to measure how heavy or light a petroleum liquid is

compared to water the density of petroleum. It was established by the American Petroleum Institute. If API

gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.


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The local lithology is characterized by sediments from Curaray Formation,

Chambira Formation, Mera Formation and recent alluvial deposits. Curaray Formation is

made up of sandy-to-silty soils with deposition in a tidal environment. Chambira

Formation is formed by: quartz pebble-bearing conglomerates; a basal part of trough

cross-bedded and matrix supported conglomerates; and, an upper part of conglomerates

with horizontal and trough cross-stratifications grading up to trough cross-bedded and

ripple cross-laminated sandstones and massive siltstones. Mera Formation is covered by

volcaniclastic deposits, with a lower part composed of well-sorted rounded clasts

included in a volcanic sandy matrix, and a middle part composed by unsorted angular

andesitic clasts included in an ash-rich silty-to-sandy matrix (Hoorn & Wesselingh,

2011).

The soils in the place are classified as R and B units, according to Custode &

Sourdat (1978). The R units are developed soils in colluvial and alluvial deposit from

volcanic origins. The profiles are shallow (an average of one meter of depth) and little

differentiated soils. The textures are ranged as clay, silty-clay, and clayey loam. These

soils are compacted and low-permeable. Additionally, B units are red clay soils,

developed in weathered tertiary sediments. The profile depths vary from one to a few

meters and the morphology is ranged from coarse sand to silt. Figure 2 shows typical

values of hydraulic conductivity and permeability according to soil type.

Figure 2. Typical values of hydraulic conductivity and permeability (Bear, 2013)

3.1.3. Hydrology and hydrogeology

With regards to hydrological characteristics, the area is located in the catchment

area of Napo River and Aguarico River. Aguarico River is the closest major water body

and is located at approximately 350 meters to the North. Aguarico River rises south of

Tulcán Province, in the Andes Mountains near the border of Ecuador and Colombia, and

flowing about 390 km (Ziesler & Ardizzone, 1979) east-southeast to outlet on the Napo

River at Pantoja in the frontier between Ecuador and Peru A minor tributary stream is

located at 60 meters to the West from the platform (Annex 1).


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Along the Aguarico River the aquifers are unconfined and confined with medium

to high permeability, and they produce from small to large quantities of fresh water. These

aquifers are alluvial, consisting of sand, gravels, and cobble (US Army Corps of

Engineers, 1998). According to soils, lithology and hydrogeology units, the physical

properties include a medium permeability with discontinuous shallow aquifers. The local

aquifers have limited extension and they are hard to be exploited. Groundwater from these

aquifers transfer water to superficial water bodies (Cardno ENTRIX, 2013).

Sand has been found as a common deposit and subsurface material in the

Concession Area, and groundwater spread out across an area of aproximatly 2000 km2.

Shallow aquifers occur throughout the region, between 0.2 to 6.0 (Goldstein & Garvey,

2013).

3.1.4. Vegetation and fauna

Most of the richness in natural resources in Ecuador is found in the Amazon

(Mejía & Pacheco, 2014) with very high levels of alpha biodiversity (Pitman et al., 2002),

and characterized as a hotspot of biodiversity (Myers, 1990). The region consists of more

than 100000 km2 of tropical rainforest, contains one of the most diverse collections of

plants and animals in the world, and is home of about 500000 people (San Sebastián

& Hurtig, 2004, 2005).

The ecoregion is classified, according to the major habitat type, as a tropical moist

broadleaf forests (Dinerstein et al., 1995), and as a tropical rainforest according to the life

zone system (Cañadas, 1983). The land uses in the concession area has anthropogenic

intervention and include landholdings with permanent and temporary crops.

AG-06 is surrounded by secondary forest, crops, and pastures. According to the

biotic base line made by (Cardno ENTRIX, 2013) in the zone where AG-06 is located,

different species of terrestrial and aquatic fauna may be found, including mammals,

amphibians, reptiles, birds, fishes and invertebrates. Finally, it is important to state that

the study place is not located into a Biosphere Reserve, nor a Natural Protected Area.

3.2. Socioeconomic conditions

As Mena, Walsh, Frizzelle, Xiaozheng, and Malanson (2011) states, complex

interactions occur in the northern Ecuadorian Amazon due to the participation of

important and diverse stakeholders. The region is occupied by spontaneous colonists,

newly emerging communities, market centers, indigenous people, oil companies, and

government agencies. AG-06 is placed in the Precooperativa Los Vencedores, a colonial

settlement, which is part of San Roque District of Shushufindi Canton. Colonists accessed

the region via the roads built by oil companies that made isolated areas. The development


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and expansion of communities encouraged the distribution of service centers and

employment nodes in the place.

The main economic activity in Shushufindi is the oil exploitation that signifies the

94% of the gross value added (GVA) in the district. However, only 6% of the

economically active population is furnished the supply of labor in this activity. Most of

them are enrolled in agriculture, livestock farming, forestry, and fishing, followed by

activities such as trade and manufacture (Municipio de Shushufindi, 2015).

There is not a clear differentiation in the productive activities within peasants and

indigenous groups because of the scarce social division of work based on an economy of

self-subsistence. The occupancy is significant, even though the remuneration is low.

Therefore, the unemployment cannot be treat in the regular terms (Cardno ENTRIX,

2013). Table 3 includes social and economic data of San Roque District, which are

considered as unsatisfied basic needs indicators (INEC, 2010).

Table 3. Life conditions in San Roque District, Shushufindi (INEC, 2010).

Total of

households

Households

without basic

services

Households

with critical

overcrowded

conditions

Extreme

poverty

Non-extreme

poverty

Households

with satisfied

basic services

470 464 206 272 194 4

100% 99% 44% 58% 41% 1%

According to the last census of population and housing (INEC, 2010), indigenous

groups such as Kichwa, Shuar, Siekopai and Siona, live in Shushufindi. Cardno ENTRIX

(2013) developed a more particular study in Cooperativa Los Vencedores, where 80% of

the population self-identify as mixed race, and 20% as white race.

3.3. Contaminant sources, fate and transport

The evaluation of the nature and the particular mixture is an important step in

order to assess petroleum contaminated sites and recognize what kind of products are

being cleaned up to select an optimal remediation technology (Cole, 1994). Petroleum is

a liquid mixture of organic compounds, which can be obtained at certain regions of the

upper strata of the earth (Irwin, 1997). Crude oil is the source material of most of

petroleum products (Potter, 1989) and contains thousands of different chemical

compounds with a composition that varies from one region to another and, also, within a

particular formation (National Research Council, 1985).

Because of the many different chemicals in crude oil and petroleum products and

the associated analytical difficulties, the term total petroleum hydrocarbons (TPHs) is


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used to describe all of them. Some common chemicals that may be found in TPHs are

hexane, mineral oils, benzene, toluene, xylenes, naphthalene, and fluorene, as well as

other petroleum products and gasoline components (ATSDR, 1999a; Potter, 1989). Also,

crude oil may contain concentrations of trace metals as vanadium (V), nickel (Ni), iron

(Fe), aluminum (Al), sodium (Na), calcium (Ca), cupper (Cu), and uranium (U) (National

Research Council, 1985). The potential contaminants associated with oil exploration and

production activities in the study site include petroleum hydrocarbons and metals which

may impact soil, groundwater and surface water. Potential sources of these contaminants

include; leaking tanks; leaking well heads; interaction between groundwater and

petroleum; and, overflowing, failing, or unlined reserve pits.

Reserve pits is a low-cost method widely used in petroleum industry, which do

not required waste transportation from the well site (Islam, Khan, & M., 2013). Pits are

surface impoundments or excavations built adjacent to the site of operation. On-site pits

have different application according to the type of waste or function, such as: drilling

reserve pits, workover pits, produced water pits, evaporation pits, among others. In

modern rigsites, reserve pits have to be isolated from the surrounding environment and

are closed after well completion (Wojtanowicz, 2016). The contents of reserve pits may

vary and cause local environmental impact, particularly if they do not comply regulations.

One major concern with burial methods is the potential for heavy metals, hydrocarbons,

and salts to migrate (Reis, 1996).

Migration, transport mechanisms, volatilization and adsorption tendencies are

some of the main product characteristics that must be taken in account beforehand to

evaluate contamination (Cole, 1994). The particular nature of petroleum products is

simple to understand, however, the product formulation is often complex. Once the

petroleum hydrocarbons have been released, the relative product composition may

change due to both environmental conditions and transformation processes as

volatilization, dissolution, and biotic and abiotic degradation (Potter, 1989). According

to Irwin, van Mouwerik, Lynette, Seese, and Basham (1998), less than 5% of the crude

oil will dissolved in water. Aromatic hydrocarbons, such us benzene, toluene,

ethylbenzene, and xylene (also known as BTEX), tend to be the most water-soluble

fraction of crude oil and petroleum compounds (Williams, Ladd, & Farmer, 2006).

Dissolved organic contaminants are often observed to degrade in groundwater

environments into carbon dioxide, methane, or intermediate organic compounds through

biological transformation reactions. Such transformations are closely tied to local

geochemical conditions, favorable redox conditions, thermodynamic constraints and the

availability of appropriate microbial populations (McNab & Narasimhan, 1995).

Organic contaminants can enter the subsurface in the form of a nonaqueous phase

liquid (NAPL) immiscible with water or as dissolved solutes. The NAPL is a longterm

source of contamination transferring soluble or volatile constituents from the NAPL to

the subsurface, air, water and solid phase. Emanating contaminant plumes are


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consequence of changes in concentration due to mass transfer progress in time. Fluid

density influences the fate of a NAPL in the subsurface. NAPLs, such as petroleum

hydrocarbons, are less dense than water (LNAPLs), whereas others are denser than water

(DNAPLs), such as chlorinated solvents (Essaid et al., 2015). Depending on whether the

contaminant is dissolved in water or is carried in an LNAPL or DNAPL, the mechanics

of migration for contaminants will vary greatly and follow a particular mechanism

(National Research Council, 1994; Sellers, 1999).

When the LNAPL, such as petroleum hydrocarbons, enters the subsurface, it

migrates downward through the unsaturated zone due to the influences of gravity,

pressure gradients, and capillary forces. Due to variations in unsaturated hydraulic

properties, it may spread laterally, forming a “lens” which float on the top of the water

table. Changes in water table can also spread vertically enhancing the area of LNAPL

contamination. This changes can be produce because of seasonal fluctuations or the

pumping of water. LNAPL will accumulate and spread at the water table, once it reaches

the saturated zone (Essaid et al., 2015; National Research Council, 1994). Interaction with

the soil particles affects dissolved concentrations when the plume of dissolved

constituents moves away from the floating bulk. The rate of movement varies according

to the attraction of the compounds to the aquifer material. Compounds more attracted

move at a slower rate than the groundwater and are found closer to the source. On the

other hand, compounds less attracted to the soil particles are found in the leading edge of

a contaminant plume and move most rapidly and are found (EPA, 2002). Figure 3

illustrates the migration process reviewed in this section.

Figure 3. Generalized vertical cross section illustrating the infiltration of LNAPL and

DNAPL in the subsurface (Essaid et al., 2015)

Volatile LNAPL compounds partition into the air phase and the contaminant may

follow different behavior paths. Vapor-phase transport can be followed by dissolution in

groundwater or aqueous-phase contaminants can be expected to volatilize into the pore


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spaces. A vapor plume of compounds with high vapor pressures and high aqueous

solubilities can be produced (EPA, 2002).

Oil physical properties have an important influence on toxicology and

biodegradability. Density is one of the properties used to determine the potential effect of

the contaminant in the environment, and it is measured often as API gravity (Morales-

Bautista, Adams, Guzmán-Osorio, & Marín-García, 2012). Table 4 indicates general

characteristics used to classify crude oil according to density and sulfur content. As shown

in Figure 4, when the API gravity is greater than 10, the petroleum liquid is lighter and

floats on water; if the liquid petroleum is heavier than water, it sinks and its API gravity

is less than 10.

Table 4. General characteristics of crude oil (Jones, 2010; Jukić, 2013)

Property Classification Value

Sulfur content [weigtht %] Sweet 0.1 – 0.5 %

Semi-sweet 0.5 – 0.8 %

Sour 0.8 – 5 %

Density [° API] Light > 31.1°

Medium 22.3° – 31.1°

Heavy 10° – 22.3°

Extra heavy <10°

Figure 4. API gravity of some hydrocarbon compounds (Railsback, 2015)


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3.4. Human health and ecotoxicology

A basic understanding of petroleum properties is necessary to define the public

health implications associated with the exposure (ATSDR, 1999b). Due to the

complexity of TPH, to evaluate accurately the impact on human health and ecosystem it

is needed to emphasize the route and duration of exposure and on type of health effect.

The level of exposure and concentrations of the contaminant lead to health impacts for

different agents.

Among the affections for TPHs exposure are headaches and dizziness, peripheral

neuropathy, and harmful effects on the blood, immune system, lungs, skin, and eyes.

Furthermore, animal studies have shown effects on the lungs, central nervous system,

liver, and kidney and also affections on reproduction and the development of fetus

(ATSDR, 1999a). The International Agency for Research on Cancer (IARC, 1982, 1987)

defines that benzene is carcinogenic to humans, and benzo[a]pyrene and gasoline are

probably and possibly carcinogenic to humans.

Concretely, human affections in the Amazon basin of Ecuador have been

evaluated numerous times. Eye irritations and headaches increased risk of spontaneous

abortions (Instituto Manuel Amunárriz, 2004; San Sebastián, Armstrong, & Stephens,

2002), higher risk of cancer (as leukemia and liver cancer) and cancer mortality rates

(Instituto Manuel Amunárriz, 2004; Maldonado & Narváez, 2003; San Sebastián et al.,

2002) and, increased frequency of fungal skin infections and fatigue (Instituto Manuel

Amunárriz, 2004) are some of the reported results in these investigations.

The usability of lands is reduced by petroleum contaminated soils and weathered

petroleum residuals in soil may remain bound for several years in the soil matrix (Kisic

et al., 2009). Additionally, petroleum contamination exerts multiple toxicological effects

on nitrogen assimilation of plants (Nie et al., 2011).

3.5. Environmental remediation strategies

Remediation of hydrocarbon contamination is handled by a variety of remediation

technologies which act over different distribution paths between free, adsorbed, and

dissolved phases in both the vadose and saturated zones (Ram, Bass, Falotico, & Leahy,

1993). The impacts of physical, chemical, biological, and hydrogeological heterogeneity,

pore-scale interactions, and mixing on the fate of organic contaminants are challenges to

achieve for selecting successfully a remediation technique (Essaid et al., 2015).

The treatment strategies may be primary categorize according to their functions:

(1) destruction or alteration of contaminants; (2) extraction or separation of contaminants

from environmental media; or, (3) immobilization of contaminants (EPA, 2002). Table 5

summarizes the main concepts and representative technologies.


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Table 5. Concepts of remedial strategies by function (EPA, 2002).

Remedial strategy by

function Concept

Destruction or alteration

of contaminants

Thermal, biological, and chemical treatment methods capable of

altering the chemical structure of contaminants. These destruction

technologies can be applied in situ or ex situ to contaminated

media.

Extraction or separation

of contaminants from

environmental media

Technologies based on extraction and separation of contaminants

from environmental media, such as thermal desorption, soil

washing, solvent extraction, and soil vapor extraction (SVE) and

ground water treatment by either phase separation, carbon

adsorption, air stripping, ion exchange, or some combination of

these technologies.

Immobilization of

contaminants

Technologies for stabilization, solidification, and containment,

such as placement in a secure landfill or construction of slurry

walls.

The definition of a remedial strategy should be site and incident specific, and an

optimum remediation may require the combination of procedures (Riser-Roberts, 1998),

given that, generally, a single technology cannot remediate an entire site (EPA, 2002).

For instance, at highly heterogeneous sites, such as sites characterized by variable

subsurface flow rates, soil types or an uneven distribution contamination, technology

coupling may be an effective alternative. (Camenzuli, Freidman, Statham, Mumford, &

Gore, 2013; Filler et al., 2006). Christ, Ramsburg, Abriola, Pennell, and Löffler (2004)

state that coupling physical-chemical remediation treatments may provide a synergism to

remove significantly contamination. Coupling technology can increase the efficiency and

spectrum of contaminated site management (Tomei & Daugulis, 2013) being also

particularly favorable at co-contaminated sites with metals and petroleum hydrocarbons,

where the use of a single technology is challenged by the chemistry, toxicity and

remediation requirements of individual pollutants (Dong, Huang, Xing, & Zhang, 2013).

3.6. Legal and regulatory framework

Regulations have significantly reduced the frequency of new point-source

contamination problems; but, remediation at many legacy plumes is still a great challenge

(Essaid et al., 2015). To define remediation goals and to assure the successful

implementation of remediation strategies, the assessment has to be considered taking

place within the legal, policy and institutional frameworks established by the country and

pertinent international agreements.

Environmental rights are clearly outlined in the Ecuadorian Constitution

(Constitución del Ecuador, 2008), which is the supreme law of the land and prevails over

any other legal regulatory framework. It states that nature has the right to integral respect


19

for the maintenance and regeneration of its life cycles, structure, functions and

evolutionary processes. The Ecuadorian Constitution provides a particular framework to

base environmental policies and management and raises the nature as subject of rights

(Gudynas, 2009; Neto & Lima, 2016).

As part of Ecuadorian legislation, the Ley de Gestión Ambiental (Law of

Environmental Management) establishes the principles and guidelines of the

environmental policy, and it determines the obligations, responsibilities, levels of

participation and indicates the permissible limits, controls and sanctions in this matter

(Ley de Gestión Ambiental, 2004).

Permissible limits are mainly regulated by the following two regulatory texts:

Reglamento Sustitutivo del Reglamento Ambiental para las Operaciones

Hidrocarburíferas en el Ecuador, also known as RAOHE (Decreto No. 1215); and, Texto

Unificado de Legislación Secundaria del Ministerio del Ambiente2 (Unified Text of

Secondary Legislation of the Ministry of Environment), also knonw as TULSMA. Tables

6 to 8 include the criteria and maximum permissible levels for different parameters, in

order to compares these values with the current Ecuadorian regulations. Remediation

goals and actions has be defined according to those requirements.

Table 6. Permissible levels for surface water and groundwater

Parameter RAOHE 1215

TULSMA

Domestic uses and

human consumption

Agricultural

irrigation

Temperature [°C] 3.0 - -

pH [-] 6.0 - 8.0 - 6.0 - 9.0

Conductivity [µS/cm] 170 - -

TPHs [mg/L] 0.5 - -

COD [mg/L] 30.0 < 4 -

PAHs [mg/L] 0.0003 - -

Barium [mg/L] - 1.0 -

Cadmium [mg/L] - 0.02 0.05

Copper [mg/L] - 2.0 0.2

Chromium [mg/L] - - 0.1

Lead [mg/L] - 0.01 5.0

Nickel [mg/L] - - 0.2

Vanadium [mg/L] - - 0.1

Dissolved oxygen [mg/L] - - 3.0

2 Updated by the Ministerial Agreement 097-A


20

Table 7. Permissible levels for soil and sediments

Parameter RAOHE

1215

TULSMA

Residential Commercia

l Industrial Agricultural

TPHs [mg/kg] 2500 230 620 620 150

Bencene [mg/kg] - 0.08 5 5 0.03

Ethylbenzene [mg/kg] - 0.1 20 20 0.1

Styrene [mg/kg] - 5 50 50 0.1

Toluene [mg/kg] - 0.37 0.8 0.8 0.08

Xylene [mg/kg] - 2.4 11 20 0.1

PAHs [mg/kg] 2 - - - -

Anthracene [mg/kg] - - - 100 0.1

Benz(a)anthracene [mg/kg] - 1 1 10 0.1

Benz(a)pyrene [mg/kg] - 0.7 10 0.7 0.1

Benzo(b)fluoranthene [mg/kg] - 1 0.7 10 0.1

Benzo(k)fluoranthene [mg/kg] - 1 10 10 0.1

Dibenz(a,h)anthracene [mg/kg] - 1 10 10 0.1

Indeno(1,2,3-cd)pyrene

[mg/kg] - 1 10 10 0.1

Fluoranthene [mg/kg] - - 10 100 0.1

Naphthalene [mg/kg] - 0.6 - 22 0.1

Pyrene [mg/kg] - 10 22 100 0.1

Chrysene [mg/kg] - - - 100 0.1

Phenanthrene [mg/kg] - 5 50 50 0.1

Cadmium [mg/kg] 2 - - - -

Nickel [mg/kg] 50 - - - -

Lead [mg/kg] 100 - - - -

Conductivity [uS/cm] - 200 400 400 200

pH [-] - 6.0 - 8.0 6.0 - 8.0 6.0 - 8.0 6.0 - 8.0

Barium [mg/kg] - 500 2000 2000 750

Cadmium [mg/kg] - 4 10 10 2

Copper [mg/kg] - 63 91 91 63

Total Chromium [mg/kg] - 64 87 87 65

Nickel [mg/kg] - 100 100 50 50

Lead [mg/kg] - 140 150 150 60

Vanadio [mg/kg] - 130 130 130 130


21

Table 8. Permissible levels to muds and wastes from drilling when the disposal place

has no impermeable barrier

Parameter RAOHE 1215

pH [-] 6.0 - 9.0

Conductivity [µS/cm] 4000

TPHs [mg/L] 1.0

PAHs [mg/L] 0.003

Cadmium [mg/L] 0.05

Total Chromium [mg/L] 1.0

Vanadium [mg/L] 0.2

Barium [mg/L] 5.0

Although this project is align to the current legal and regulatory framework to

advocate compliance with laws and regulations, it is important to mention that

environmental regulations and standards were operative and governed oil exploration and

production during Texpet’s activities. The regulations included variety of environmental

obligations to protect the natural resources in the Concession Area from adverse impacts

(Goldstein & Garvey, 2013). According to Aráuz (2009), the governing regulations were

the following: from 1921 to 1937, Ley sobre Yacimientos o Depósitos de Hidrocarburos

(Hydrocarbon Deposit Law); from 1937 to 1971, Ley de Petróleo (Law of Petroleum);

from 1971 to 1975, Ley de Hidrocarburos (Law of Hydrocarbons); and, from 1975

onwards, Reforma a la Ley de Hidrocarburos (Amendment of the Law of Hydrocarbons).


22

4. Material and methods

4.1. Environmental site assessment

A preliminary investigation based on an environmental site assessment was

performed in order to predict the possibility of hazardous substance contamination on the

property or around it (Hess-Kosa, 2008). The assessment was divided into three activities.

The first activity was a descriptive characterization in order to understand the physical

site setting, including geology, hydrogeology and hydrology conditions. Secondly, a

historical assessment of record reviews based on preliminary studies, photographs, land

uses and multi-temporal analysis of digital satellite images. Thirdly, to complete the

preliminary phase and understand underlying facts, trial documents (as pleadings,

motions, supporting memoranda, and special reports, among others) were reviewed and

considered. To define background concentration data, previous studies were assessed.

Furthermore, a specific investigation was performed in order to corroborate

historical findings and evaluate in situ potential sources of impacts. The visit included the

recognition of platform AG-06, the Station Aguarico, sensitive water bodies and nearby

human settlements. Additionally, both surface water and soil samples were taken at the

site in order to approach background levels.

4.1.1. Soil and water sampling

Two surface water samples were taken from a small creek. One was taken to

measure basic quality parameters (temperature, dissolved oxygen, conductivity, pH, ORP

and salinity) with a handheld multiparameter. Additionally, volatile organic compounds

(VOCs) were measured with a photoionization detector (PID) in the same sample. A

second sample was taken in a brown glass jar of 1 L and was completely filled with water

from the same water body. Then, a standard seal and label process was performed. The

sample was refrigerated at 4 °C and transported to a laboratory in the city of Quito. Table

9 indicate details about the multiparameter sensor used during field activities.

A soil sample was taken with a regular soil auger from 1.3 to 1.6 m of depth. The

sample was homogenized and collected in a re-sealable zipper plastic storage bag. As

with the water sample, VOCs were measured with the PID from the plastic bag. The

sample was then sealed, labeled and stored at 4 °C, and subsequently transported to the

laboratory. Table 10 shows characteristics of the PID.


23

Table 9. Characteristics of the multiparameter sensor (YSI Inc., 2017)

Brand YSI - Professional Plus (Pro Plus)

Description Handheld multiparameter meter for the measurement of a

variety of water parameters

Operating Temperature 10 to 60°C

Other characteristics 100 GLP files of memory

USB 2.0 for data transfer

Graphic display

Parameter Units Accuracy

Temperature

Dissolved oxygen

Conductivity

pH

ORP

Salinity

°C

%

mS/cm,

pH units

ORP-mV

ppt

±0.2°C

± 2% of reading or 2% air saturation

±0.5% of reading or 0.001 mS/cm

±0.2 units

±20 mV in redox standards

±1.0% of reading or ±0.1 ppt

Table 10. Characteristics of the photoionization detector (PID) (RAE Systems, 2015)

Brand RAE Systems - MiniRAE 3000

Description Handheld VOC monitor

Range detection From 0 to 15,000 ppm

Other characteristics Three-second response time

Correction factors for more than 200 compounds

Both water and soil samples were delivered to an accredited laboratory3. Total

petroleum hydrocarbons (TPHs) were considered as compounds of interest. To determine

quantitatively the concentrations of the compounds, the laboratory analytical system used

was gas chromatography through the method 8015C (EPA, 2000), Location of samples

are shown in Table 11, and displayed in Annex 3. Lab certificate can be found in the

Annex 6.

3 Laboratorio Lasa with accreditation N° OAE-LE-1C-06-002 certified by the Servicio de

Acreditación Ecuatoriano (Ecuadorian Accreditation Service)


24

Table 11. Location of soil and water samples

Medium Codification Location

East (X) North (Y)

Soil AG-06-S-01 985426.64 9993854.68

Surface water AG-06-W-01 985396.48 9993826.63

Surface water AG-06-W-02 985396.48 9993826.63

4.2. Conceptual site model

To characterize the past, present, and future conditions at the site, a conceptual

site model has to be done making subjective judgements and simplifying assumptions.

The construction of this model is a crucial first step for risk assessment and subsequent

environmental remediation (Wiersma, 2004).

The understanding of what information and the quality of the data are required to

develop the conceptual site model. The conceptual site model incorporates: background

information; geologic and hydrogeologic data; contaminant source; distribution, fate and

transport data; major migration pathways and groundwater flow gradient; and, risk

assessment information (Battelle Memorial Institute, 2010; The Colorado Department of

Labor and Employment, 2007; Wiersma, 2004). Therefore, the model is constructed with

source term properties, site conditions, transport processes and properties of possible

receptor were including to develop the model. For practical purposes, the model is

represented through a drawing developed in SketchUp Make 2017. Table 12 includes the

judgements used for the construction of the model.

Table 12. Judgements in development of conceptual site models (Wiersma, 2004)

Type of judgement Parameters and factors

Source term properties Spatial distribution of contaminants; transport pathways of

interest; flux of contaminant; release rate; and presence of

barriers preventing or restricting release of contaminant.

Site geometry Topography; location and dimensions of contaminated area; and,

depths of saturated and unsaturated layers.

Transport properties Subsurface geology; physical and chemical characteristics of

media (e.g., soil porosity, organic matter content, bulk densities,

pHs, hydraulic conductivity); seasonal conditions; and, direction

and velocity of groundwater flow.

Receptor properties Land use; location of exposure; and pathways of exposure.

Exposure factors Population distribution; exposure duration; ingestion rates; and,

bioaccumulation and toxicity factors.


25

Moreover, considering that different activities from crude oil operation expose

human beings (Lambert, Molenaar, Clark, & Ryer-Powder, 2001), an exposure pathway

is modeled and focused on the current situation due to the identified contamination and

the presence of native communities. Since the risk depends not only on the contaminant

characteristics or its concentration into the environment but also on the exposure, an

exposure pathway allows identification of a list of potential remedial alternatives

applicable to the situation and priorities at a given site. By developing this model, the

logistic actions and the cost treatments can be projected in general notions for remedial

actions.

4.3. Remediation technology selection

Once the site characterization and the closure goals were defined, the technologic

applicability and the remediation criteria can be adequately assessed (Ram et al., 1993).

The EPA (2002) provides practical reviews and compilations of several treatment

technologies based on field applications, which are used in this project. Two categories

are defined in the reports: soil, sludge, and sediment media, and groundwater media. Both

of them are grouped into technology types: ex situ biological, in situ biological, ex situ

physical/chemical, and in situ physical/chemical. A total of 53 in situ and ex situ

technologies for either soil or groundwater remediation are included for a first screening.

Presumptive remedies, which their feasibility was determined by previous studies

compiled by EPA (2002), are classified to accelerate site-specific analysis of remedies.

Contaminants are classified into eight groups: nonhalogenated VOC’s, halogenated

VOC’s, nonhalogenated SVOC’s, halogenated SVOC’s, fuels, inorganics, radionuclides,

explosives (EPA, 2002). Due to pollution conditions and the remedial objectives,

technologies which did not demonstrated effectiveness to treat the petroleum

hydrocarbons, at pilot or full scale, were neglected for this evaluation.

As Achieng (2007) recommends about the assessments of projects, the selection

procedure should cover both the construction and the operation phases of the project,

because the construction may causes greater impacts than the operations. Therefore, the

matrix method identifies interactions between various technologies and contaminants and

application conditions. Technologies are evaluated according to the following

characteristics: excavation requirement; operation and maintenance; capital; system

reliability and maintainability; and, relative costs. Considering positive and negative

characteristics, reasonable technologies are preferred and the analysis is extended to the

next evaluation.


26

4.3.1. Decision making tree

The use of treatment technologies can have a significant impact on the natural

resources, careful consideration should be made (EPA, 2002). Therefore, feasibility was

scrutinized through a decision making tree without probabilities. Performance limitations,

level of treatment effectiveness, and required time to clean up were considered as

fundamental conditions for the decision tree. The decision tree includes two types of

nodes: decision and chance. Decision nodes (represented as squares) are used to remark

the existence of more than one similar alternative in the evaluated parameter. On the other

hand, chance nodes (represented as circles) are used when only one option exist under

evaluated characteristics.

The final phase was focus on the identified remediation strategy. This phase

contains an evaluation of suitable remediation goals as well as procedures to be include

into implementation and management plans. To summarize the whole process applied in

Chapter 4.3, the Figure 5 contains a flowchart clarifying the procedure.

Figure 5. Flowchart of remediation technology selection process


27

5. Results and discussion

5.1. Contamination levels and source analysis

The observed pollution pattern suggests that the site was contaminated during oil

exploration and production activities. The assessment revealed that the most significant

contamination comes from drilling and workover wastes, and oily produced water, which

were discharged to well site pits. Although typical contaminants in oilfield pits are heavy

metals, chloride salts and hydrocarbons, most of the studies in the area primarily warn the

presence of petroleum hydrocarbons as main concern.

(Goldstein & Garvey, 2013) indicates that Texpet operation documents expose

that 4 to 6 pits were required for its typical well drilling process. Four pits have been

clearly identified in AG-06 (Ministerio del Ambiente, 2017). All of them are located

around the platform and their area vary between 288.56 to 2479.95 m. Surface extension

and location of each pit is shown in Table 13.

Table 13. Identified reserve pits

Code

Type

of

liabilit

y

East

(X)

North

(Y)

Area

[m2]

Operator

company

Opening

year

Source

reference

AG06-PIT1 Pit 985317.6 9993984.0 2479.95 Texpet 1974 MAE,

2016

AG06-PIT2 Pit 985321,1 9993915.0 288.56 Texpet 1974 MAE,

2016


2016


2016

Assuming a depth of 3 m, the total volume of the pits is 19186.26 m3. The biggest

pit is located at the northwest part of the platform. Table 14 shows the expected volumes.

Annex 3 include the location of the pits and their possible distribution.


28

Table 14. Expected volume of reserve pits

Code Area

[m2]

Assumed depth

[m]

Expected volume

[m3]

AG06-PIT1 2479.95 3.00 7439.85

AG06-PIT2 288.56 3.00 865.68

AG06-PIT3 1600.00 3.00 4800.00

AG06-PIT4 2026.91 3.00 6080.73

Total 6395.42 19186.26

High concentrations of TPHs have been previously disclosed in AG-06 (Goldstein

& Garvey, 2014; Ministerio del Ambiente, 2017; Procuradoría General del Estado, 2015;

Worldwide Reporting, 2015). Reported concentrations by Winston & Strawn, LLP and

The Louis Berger Group (2014) exceed the permissible limits established in the

Ecuadorian legislation, and, moreover, every groundwater and surface water sample

analyzed showed signs of crude oil contamination.

Contamination is observed more than 60 meters from the pits. Therefore, the risk

of contaminate surface water bodies is high. Disposal into rivers and estuaries of water

contaminated with petroleum, residual gas, and chemical products were reported in

volumes of 30.8 L/s in the fields Shushufindi and Aguarico (DIGEMA & Fonseca, 1989).

Tables 15-18 and Figure 6 summarize the reported results for soil, sediments,

groundwater, and surface water.

Table 15. Analytical results of soil samples (Winston & Strawn, LLP & The Louis

Berger Group, 2014)

Parameter AG06‐SL001

AG06‐SL002

AG06‐SL003

AG06‐SL004

AG06‐SL005

AG06‐SL006

AG06‐SL007

AG06‐SL008

AG06‐SL009

Total PAH 7.70 0.18 0.15 0.35 12.00 31,00 13.00 126.00 75.00

Total

n-Alkanes 5.70 1,90 1,20 7.80 12.00 11,00 6.70 - 20.00

TPH 230.00 18.00 16.00 26.00 360.00 580.00 390.00 2300.00 1600.00


29

Table 16. Analytical results of sediments samples (Winston & Strawn, LLP & The

Louis Berger Group, 2014)

Parameter AG06‐SE001 AG06‐SE002 AG06‐SE003 AG06‐SE004 AG06‐SE005

Total PAH 0.52 2.10 0.59 0.33 0.63

Total

n-Alkanes 29.00 2.70 4.20 11,00 5.80

TPH 66.00 100.00 34.00 34.00 31,00

Table 17. Analytical results of groundwater samples (Winston & Strawn, LLP & The


Parameter AG06‐GW005

AG06‐GW007

AG06‐GW008

AG06‐GW009

AG06‐GW010

AG06‐GW011

Total PAH 5.50 0.60 26.00 3.20 214.00 7.20

Total n-

Alkanes 6.60 4.50 10.00 21,00 86.00 13.00

TPH 130.00 220.00 2800.00 320.00 3500.00 490.00

Table 18. Analytical results of surface water samples (Winston & Strawn, LLP & The


Parameter AG06‐SW001 AG06‐SW002

AG06‐SW003

AG06‐SW004

AG06‐SW005

Total PAH 0.09 0.08 0.10 0.09 0.09

Total

n-Alkanes 1,00 9.70 0.51 0.48 0.85

TPH 42.00 39.00 40.00 40.00 50.00


30

Figure 6. TPHs average concentrations on different media according to analytical

results from Winston & Strawn, LLP and The Louis Berger Group (2014) investigations

Results of the analysis of soil and water samples taken as part of this project are

presented in Table 19. The presence of TPHs in the sample AG06-S-01 gives evidence of

the migration of the contaminant beyond the pit boundary, for the reason that the sample

was not taken directly above the pit (see Annex 3). The analytical evaluation of surface

water sample AG-W-02 does not reveal contamination, and the TPHs concentration is

under the detection limit (< 0.30 mg/L). Contamination was also observed in the field as

oil sheens on water puddles and petroleum odor, which warn the presence of free product

around the platform.

Table 19. Analytical results of soil and surface water samples

Parameter Sample

AG-S-01 AG-W-01 AG-W-02

TPH 44.00 [mg/kg] - < 0.30 [mg/L]

VOC [ppm] 16.3 - -

pH [-] - 5.18 5.10

Conductivity [mS/cm] - 0.122 0.122

Dissolved oxygen [%]

[mg/L] - 53.2 ; 4.13 53.2 ; 4.13

Salinity - 0.05 0.05

Temperature [°C] - 28.4 28.2

ORP/Redox [mV] - -116.4 -114.0

613,33

53,00

1243,33

42,20

0

200

400

600

800

1000

1200

1400

Soils

TP

Hs

conce

ntr

atio

n [

mg/L

]Soils

Sediments

Groundwater

Surface water


31

5.1.1. Generic conceptual model

Even after decades, the pits are still capable of releasing their harmful content out

of their boundaries. Pit content has seeped underneath the pit limits, reaching lower soil

layers and the groundwater table. When the contaminant reaches the groundwater, water

soluble constituents may be dissolved and migrate as a contamination plume. The plume

of dissolved constituents may move away from the floating bulk of LNAPL constituents.

The rate of the movement, which depends on the geological conditions and the attraction

of the compounds to the aquifer material, is considered low (between 10-3 to 10-7 cm/s)

due to the presence of semi-pervious soils (clay, silty clay, and clayey loam). However,

nearby hand dug groundwater wells give evidence contamination due to the transport of

the pit content through more porous soils (coarse sand to silt). Most of the lower-

molecular weight petroleum hydrocarbons are subject to volatilization, oxidation,

dissolution and biotransformation processes once they are released into the environment

(Howard et al., 2005; Pollard, Hrudey, & Fedorak, 1994). The conceptual site model is

sketched in the Annex 8.

One of the main issues to take into account is the seasonal shift in groundwater

elevation. As was reviewed throughout Chapter 3.1, periods of long and heavy rainfall

are a distinctive attribute of rainforests, and, particularly in the region. Seasonal

fluctuations saturate the soil and vary groundwater elevation. Consequently, the LNAPL

may spread vertically and the affected zone may be expanded. Additionally, due to

fluctuations of the water table, LNAPL can rise and fall with it and leave a smear of

NAPL as residual saturation on the soil.

These mechanism analyzed can corroborate the presence of free product in the

surface after heavy rainfalls. Successively, runoff mobilizes the LNAPL into nearby

streams, rivers and sediments. The high circulation of contaminated water through the

soil may increase contaminant mobility requiring the treatment of underlying

groundwater. These mobilization pathways of the contaminants could explain the

reported pollution in houses, on the floors and furnishings, after bathing, laundry or

fishing (Kaigler, 2013).

5.1.2. Exposure pathway conceptual model

Contaminated media presents potentially exposure pathways for people living in

the area and for domestic animals. The most harmful exposure pathway for human beings

is the ingestion of water from contaminated aquifers as well as contaminated surface

water, considering the results of sampling campaigns (Goldstein & Garvey, 2013), which

suggest the presence of high levels of petroleum hydrocarbon. Similarly, household

activities and food consumption are considered as important potential exposure scenarios

because, as was corroborated during field activities, inhabitants use waterbodies for

fishing, bathing, cooking and cleaning.


32

Home-ground production and recreational activities are considered as exposure

pathway of partial risk. Two situation define this assumption. Firstly, crops and pastures

are irrigated totally by rainwater. Secondly, most of the recreational and agricultural

activities are accomplished considerably distant from the pollution source.

Finally, inhalation of vapors due to outdoor activities is not considered as a

significant source of exposure, however, due to the presence of volatile compounds, it

has to be considered in the evaluation of remedial actions. Figure 7 includes the flowchart

for the exposure pathway conceptual model including transport mechanisms

(volatilization, lateral spreading, uptake, infiltration and dilution) that the identified

contaminant can take to generate the different scenarios to affect human health

Figure 7. Exposure pathway model


33

5.2. Remediation technology

Due to the reported presence of contamination in soil and groundwater, the

application of remediation technologies are recommended for both them. Further

alternatives are analyzed in this Chapter in order to evaluate the possibility of coupling

technologies and to increase the grade of contaminant remotion and the achievement of

remedial goals under the permissible limits determined in Ecuadorian regulations.

As was explained in Chapter 4.3, after of neglecting technologies with “non-

demonstrated effectiveness” (EPA, 2002) to treat petroleum hydrocarbons, a total of 21

soil remediation technologies were evaluated according to five parameters (excavation

requirement, operation and maintenance, capital, system reliability and maintainability,

and relative costs). Similarly, 21 groundwater technologies were evaluated according to

four parameters (operation and maintenance, capital, system reliability and

maintainability, and relative costs). Annex 4 and Annex 5 contain the results of the

evaluation and explanation of the parameters for both soil and groundwater technologies,

respectively.

Subsequently, the most feasible technologies were assessed according to three

parameters (required time to clean up, primary limitations, and treatment target) for soil

(11 remediation technologies evaluated) and groundwater (14 remediation technologies).

The results and descriptions of these treatment technologies are shown in Annexes 6 and

7. With this information the decision making trees were built to discern the most feasible

technologies. The results are discussed in Chapters 5.2.1 and 5.2.2.


34

5.2.1. Soil and sediment remediation technology

Figure 8. Decision making tree for soil remediation technologies


35

Four remediation technologies are observed as feasible technologies for applying

in AG-06: biopiles, bioventing, enhanced bioremediation and thermal treatment. Due to

the time required to clean up the site, biopile treatment is the most satisfactory. Biopiles

is a full-scale technology based on the excavation soils, which means that the effect would

be immediate in the site and the remediation of the contaminated soil can be completed

in a short-term. On the other hand, it is an ex situ treatment that requires excavation and

transportation, which are important constraints considering the volumes of contaminated

soil.

Since reserve pits are the main source of contamination, the removal of the soil

appears as a favorable alternative in order to stop further pollution due to contaminant

migration, not only of soil and sediments but also of groundwater. This should be taken

into account in spite of the associated costs. Biopiles can be considered as a cost-

competitive technology compared to thermal desorption or landfilling (Fahnestock, 1998)

and require less area than landfarming for the treatment (Kuppusamy, Palanisami,

Megharaj, Venkateswarlu, & Naidu, 2016).

Biopile technology degrades most of the potential petroleum constituents and it is

possible to control the factors to enhance the biodegradation (such as moisture content,

heat, nutrients, oxygen and pH). Biopiles permit rapid ex-situ treatment of petroleum

hydrocarbons and avoid an important limitation that other treatments may face: the low

permeability of soil of the study site. Biopiles are being applied increasingly to remediate

petroleum products through biodegradation, however, to achieve degradation levels

above 95% is very difficult (Kuppusamy et al., 2016).

It has to be considered, if the aim is to replicate the technologies for different

contaminated sites in in the Concession Area, the economic charge that represents an ex

situ technique, due to the removal of big volumes of soil. This consideration applies for

groundwater remediation as well. Therefore, in situ remediation are proposed as

alternative option.

Bioventing, enhanced bioremediation, chemical oxidation and thermal treatment

are feasible alternatives if the ex situ treatment is not adequate. Bioremediation treatments

could reduce their performance due to the presence of heavy metals, which have not been

assessed sufficiently. Thermal treatment could be used as a pre-treatment to enhance the

application of other technologies based on biodegradation. However, three major

concerns present in the area restrict its effectiveness: the grade of saturation, the high

moisture content, and the high organic content. On the other hand, the application of

chemical oxidation is a short-term treatment. But, it may represent a high risk for human

beings and ecosystem due to the activities in the zone and sensibility of the medium.

Additionally, the aquifer heterogeneities and the short persistence may reduce the

oxidation performance.


36

5.2.2. Groundwater remediation technology

Figure 9. Decision making tree for groundwater remediation technologies


37

The treatment of contaminated groundwater is recommended by the application

of air sparging. The periodicity of the application has to be defined according to seasonal

events. Air sparging is based on the air injection into the saturated zone to remove

contaminants through volatilization. This technology is recommended to be coupled with

vacuum extraction systems to remove stripped contaminants. Special considerations on

contaminants and specific site geology reinforce the necessity of new data.

Similarly to air sparging, thermal treatment and chemical oxidation are feasible

alternatives. The limitations presented in Annex 7 may be solved through appropriate

engineering designs if more information about geology and contamination conditions are

collected. In the case of chemical oxidation the associated risks has to be considered and

managed to consolidate its use. The large range of associated crude oil contaminants that

can be treated through this method permit to consider the chemical oxidation as an

important alternative, even though its application has not be reported in Ecuador.

Most of the technologies evaluated during this study deal with one common

constrain to treat the contamination: the low permeability of soils which are characteristic

in the region. These methods are limited due to poor mixing and the difficult incorporation

of oxygen, nutrients or agents to enhance the degradation or volatilization. Furthermore,

the high level of saturation due to meteorological conditions is another circumstance to

be considered in the technology selection, especially to remediate groundwater

contamination.

The treatment of groundwater can be made by several physical and chemical

methods. In contrast, soil can be reasonable remediated mainly by biological methods.

Enhanced natural attenuation is not recommendable for this study case. Even after three

decades the negative effects in the area are observed. Furthermore, it has to be considered

that similar case of pollution can be found in several well-sites in the region.


38

6. Conclusions

Regardless the legal responsibilities, significant volumes of harmful wastes were

disposed in AG-06 during oil exploration and production activities. Petroleum

hydrocarbons (reported as TPHs and PAHs) have been detected in concentrations above

the permissible levels. Several investigations give evidence of the toxicity of the

identified pollution and the consequent risk to human health. Remediation goals must be

defined in order to satisfy no less than these limits and requirements.

Reserve pits in the site have no protective impermeable layers. Due to this fact,

percolation is a latent issue and liquid content may drain or seep through the bottom, top,

and the sides into surroundings soils. Additionally, climatic periods of the area cause a

particular transport process of surface water and groundwater. Long and strong periods

of rain saturate the subsurface frequently during the year and modify the water table.

LNAPL may be mobilizing in vertical direction, making possible the observation of oil

in the surface. Furthermore, runoff processes may transport the LNAPL into near water

bodies in a relatively short period of time.

Two major sets of technical information are needed to select a suitable

technology: contaminant information and site information (site characteristics). The

importance of detailed site assessment is emphasized previous any further step. The

chemical analysis for all individual compounds in crude oil is generally unrealistic

because of the complexity of the mixtures of hydrocarbons and the laboratory costs.

Therefore, the evaluation of TPHs fractions is recommendable.

For soil remediation, biopiles are proposed as the most feasible alternative in AG-

06 to remediate the identified contaminants in soil. Furthermore, bioventing and enhanced

bioremediation are proposed as efficient alternatives to be applied in situ; if due to

economical constrains and the volumes in various platforms make an ex situ treatment

non practical. At this point it is important to indicate that the selection treatment will

depend also on the number of platforms and pits which are expected to be remediated.

As has been discussed in this study, strengths and weaknesses of any remediation

technology will depend strongly on hydrogeological conditions. Hydrological

characteristics are not uniform, across the sites on the Concession Area. Air sparging is

proposed as technology to remediate groundwater mainly because of its capacity to act

on the saturated zone. However, limitations, especially due to geological conditions, such

as permeability, have to be faced.

Coupling of technologies represents one strategy for effective, long-term

management of petroleum hydrocarbon contaminated sites. Thermal treatment is a

possible non-biological alternative for both groundwater and soil; however; limitations


39

presented on Annex 7 should be considered. In situ thermal treatment is suitable when

the site is polluted by significant volumes of contaminant. After application of this

process, it can be coupled with a biological for the biodegradation of residual

contaminants.

One of the major limitations faced during this study for selecting the remediation

technologies was the use of previous field studies as background reference. These

previous studies were applied in different site conditions, particularly two major

concerns: geological and climate conditions. Consequently, due to the lack of information

and pilot studies in the country, and especially in the region, the study considers these

different investigations in order to include and evaluate as many treatment technologies

as possible

6.1. Recommendations

For successful treatment application, the challenge is the understanding of

physical, chemical, biological and hydrological heterogeneity. The intervention has to be

determined considering the specific hydrogeological formations where the reserve pits

are placed. A meticulous analysis of pit locations and contaminant concentrations,

defining several sampling points, is also suggested. This analysis will allow defining

accurately volumes, depths and type of pits. Therefore, the evaluation of both

applicability and the cost effectiveness will improve. Additionally, a site-specific

evaluation of the potential impact of heavy metals should be conducted to evaluate

whether groundwater monitoring for these metals is needed.

Despite the proven impact and the evident demand of inhabitants, technical and

reliable information about the contaminated sites is insufficient or, in other cases, the

access is not allowed, mainly due to the intricate litigation process. For that reason, it is

recommended to investigate the place technically and independently from the trial

process.

The implementation of coupling technologies, through sequential configurations,

can improve the decontamination of the site. The evaluation and application of treatment

technologies recommended in this study, may mean a starting point to solve the

contamination by petroleum hydrocarbons in the place, and also in other platforms in the

Concession Area. However, the application of remedial techniques and the introduction

on the contaminated places is constrain to the judicial instances. Academic institutions

can support by studying independently the situation in the place.

Mitigation actions are compulsory since several studies have demonstrated the

affection to communities. The actions have to be focus on the limitation or reduction of

the magnitude and impact over the inhabitants while the technologies are applied. Then,


40

the problem has to be faced not only by applying environmental remediation technologies

but also by the implementation of a holistic management plan.

(Antizar-Ladislao & Russell, 2007)(Friend, 1996; Grasso, op. 1993; Khan, Husain, & Hejazi, 2004; Leeson, Hinchee, & Alleman, 1997; Sandrin & Hoffman, 2007; Snape et al., 2008; Soares,

Albergaria, Domingues, Alvim-Ferraz, & Delerue-Matos, 2010; van Eyk, 1997)(Harper, Stiver, & Zytner, 1998)

(EPA, 2005, 2013)(Brown, 1995; Hoeppel, Chaudhry, Kelley, & Place, 2000; Huling & Pivetz, 2006; Stroo, Leeson, & Ward, 2013; Suthersan, 2016)


41

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