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Chapter 1. Introduction

1.1 Background

A potential hydrocarbon leak was reported at Tondiarpet in the press in July 2013. In

response to this Bharat Petroleum Corporation Limited’s (BPCL) whose pipeline is in the

vicinity of the reported spill at Tondiarpet requested IITMadras to carry out a detailed

investigation. The study was intended to identify the source of spill, extent of contamination

and environmental damage and to suggest possible remediation methods. This report

summarizes the findings of the study to ensure that the future land-use will be at its best.

The results of this study will thus enable the stake holders to make an informed decision to

revive the site for future uses. Prior to initiation of field activities IIT, BPCL and TNPCB

had preliminary meetings to finalize study methodology, borehole locations and plume

mapping techniques.

The study area for environmental site assessment is located in Chennai District of

Tamilnadu State and falls under Fort–Tondiarpet Taluk. The site is a congested area located

in Tondiarpet and lies close to the junction of Tiruvottiyur high road (T.H. road) and

VaradarajaPerumalKoil street (VPK street). At the request of Tamilnadu Pollution Control

Board (TNPCB), our team consisting of faculty members Dr. IndumathiNambi and Dr. Ravi

Krishna visited the worst affected bore wells in the site shown below

Figure 1a Location of Site

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1.2 Preliminary Site Investigation

Based on the complaints received, the team visited door nos. 221 to 228 and 231 on

T.H. Road and a few houses on VPK street who had reported oil smell or floating oil at

some earlier time - Door no 13/1, 3/19/2 and 7/2 as indicated in the map below. Samples

taken from bore wells 222, 223, 227, 228 showed significant quantity of fuel oil in the

bailers with almost 60% to 30% of volume of fluid recovered as oil. Preliminary hypothesis

is that there could be both diesel and petrol spilled at this site. One bore well did not have

Figure1b. Location of Bore Wells Sampled during Preliminary Investigation

any product but had sewage smell. The locals recalled that they have slotted pipe only in the

lower part of the bore well. Houses on VPK street did not have product but people

complained of petrol smelling water. The house 7/2 with large open well also had a bore

well where the water was clean. The open well did not have any water but the residents

complained of petrol odor from the well.

The site is a heavily congested area located in Tondiarpet and lies close to the

junction of Tiruvottiyur high road and VPK street. The BPCL pipeline (buried at ~1m

depth) runs parallel to VPK street. Domestic houses and commercial properties lay on either

side of the pipeline. It is located at a distance of 870 m west of the Coastal line and 680 m

west of Kasimedu. It is bounded by Thiruvottiyur high road on the west and Kannakarstreet

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running parallel in the East (Figure 2). Bharath Petroleum Corporation limited (BPCL) is

located at a distance of 600 m west of the contaminated area. MM theatre lies 60 metres

north of the pipeline and Agsatya Theatre lies 70 metres south of the pipeline.

The contaminated area is near to Eureka forbes premises which is located at a

distance of around 30 m in the north west, Tondiarpet Cholera hospital in the north at a

distance approximately 200 m, SNR Dhall mill and ESI Hospital at a distance ranging from

40 – 220 m in the South and South East direction, Agasthya theater, Empower Education

Tech, Devi Polymers, Lotus convent lie at a distance ranging from 70 – 150 m in the

southern direction. Agasthya Flats and Tondiarpet police station is located at a distance

ranging from 200 – 280 m in the south direction. Government peripheral hospital and 110

KV RK Nagar substation is located at a distance ranging from 300 – 380 m in west

direction.

1.3 Conceptual Model of Oil-Subsurface Interactions

The hydrogeology of the area when investigated showed altering layers of sand of

different grain sizes each 10 feet deep up to a depth of 30feet beyond which the sand layer

alternates with clay layers upto 60 feet. Below sixty to eighty feet, it was hard rock. The

pipelines are at a depth of 1.5m below the ground level. The thickness of the sand layers

may vary from place to place.

Ground water has a natural hydraulic gradient toward the east due to the seashore

but it can also be influenced by the localized hydraulic gradients due to pumping. The water

table fluctuates up and down due to rain water infiltration and pumping. When an oil spill

occurs it infiltrates the soil and reaches the groundwater table where it floats like a pool

since it is lighter than water. In summer there is excessive water withdrawal in wells which

causes water table to drop and during monsoon, the recharge of freshwater causes the water

table to rise. Due to water table fluctuation the oil layer also is pulled up and down which

causes the smearing of the oil and trapping of the oil in the soil pore spaces due to capillary

pressure as indicated in Figure 3. The oil layer can also move horizontally along with the

groundwater based on local hydraulic gradients

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Figure 2.The Study Area and its Surrounding Landmarks. The Pipelines Traversing

the Study Area has been highlighted.

The bore wells in the area extend up to the rock bed to a depth of 60 feet with slotted

pipes placed from 20 ft. The depth of the slotted pipe could have varied from one well to the

other. The oil pool will be drained into the bore well only when it intercepts the slots as

Pipe line Potential leak area

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shown in Figure 3c. This could be the reason why in some bore wells the product was seen

as early as November 2012 and some of them do not have any oil even now. This

information has to be confirmed from the bore well drillers. Water depth is at 40 feet in all

the bore wells. The unique feature of this site is that the bore wells are placed at very close

intervals approximately 10 ft from each other since the property is highly fragmented and

each owner has his own bore well in his/her piece of land. This high well density could have

also led to the lowering of the water table in their vicinity due to excessive withdrawals, thus

pulling the oil into their bore wells as indicated in the Figure 3cbelow.It was also noted that

the water and product (oil) yield from the bore wells were very less, about 4 to 5 barrels

(100 litre capacity barrels) a day based on the estimates provided by the BPCL personnel. It

was also observed that when the bore well in House 13/1 was pumped, the water flow

stopped in about two minutes.

(a) (b) (c)

Figure 3 (a) and (b) Smearing of the Floating Oil Layer in the Unsaturated and

Saturated zone(c) Bore well with slots with respect to different water and oil levels

Pre-monsoon/ post pumping water table

Bore well with screens

Post-monsoon/No pumping water table

Floating oil Smeared/trapped oil

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2. Literature Survey

2.1 History of Oil Spill

BPCL officials revealed that there were three pipelines operating in the area running

through VaradarajaPerumalKoil street at a depth of about 1.5 m. One which was dedicated

for carrying petrol was abandoned in July 2010 since it did not pass the pressure test.

Between July 2010 and November 2012 the second line was used to carry both petrol and

diesel, depending on the requirement and shipment from port. About 5 tankers of products

per month (about 40 MT of oil) were transported through this pipeline. In November 2012,

again when the pipeline did not pass the pressure test, a smart ball technique was used to

detect the location of the leak and a section of the pipe near the port was replaced. But this

fix did not help when the pressure test was repeated the pipeline failed again. These pressure

tests were done typically by filling the pipe with pressurized water up to twice the operating

pressure and check for water leaks. Hence, the second line was abandoned sometime

between November 2012- January 2013. It was also understood from the discussions that

such pressure tests are done once in a year or when they observe significant pressure drop

while pumping. The BPCL have reported that they have noticed a pin hole sized crack

during the water testing in the junction of VPK street and TH road which was fixed

immediately in November 2012.

Various products like diesel, kerosene and motor spirit were pumped to different

outlets such as CPCL, IOC and BP terminals. In the month of October 2012, 35,000KL of

High speed diesel, 7300 KL of Motor spirit (petrol) was pumped through the pipeline. In

November 2012, a vessel was due to pump from an oil tanker named ‘MT Jag Pushpa” (as

per the BPCL record) but only water flush was run through the pipeline. It is not clear when

the pipeline was abandoned.

2.2Geology and Hydrogeology of the Site

The site falls under Chennai district as per Central Ground Water Board. Chennai

district is underlain by various geological formations from ancient archaean to the recent

alluvium. The geological formations of the district can be grouped into three units, namely i)

the archaean crystalline rocks ii) consolidated gondwana and tertiary sediments and iii) the

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recent alluvium. The archaean crystalline rocks of the district comprise chiefly of

charnockites, gneisses and the associated basic and ultra-basic intrusive.

The crystalline rocks are weathered and jointed/fractured. The degree and depth of

weathering varies from place to place and the thickness of weathered mantle varies from

less than a metre to about 12 m in this district. The successful bore wells drilled tapping the

deeper fractured aquifers are in Saidapet, Adyar, Kasturba nagar, Gandhi nagar and Ashok

nagar revealed the existence of fracturing down to depth of 60 m below ground level.

The Gondwana shale is black to dark grey in colour and is jointed/fractured. They are

encountered in a number of boreholes and their thickness varies from 24 m in Kilpauk area

through 20 m in Ashok Nagar area to more than 130 m in Koyambedu area.

The occurrence of Tertiaries in Chennai district is not well demarcated. However,

the sandstones encountered in some of the boreholes below alluvium in Binny Road, Poes

Garden, Anna Nagar and Royapuram areas, which belong to Tertiary group. The granular

zones below the Kankar layer in the depth range of 20-28 m bgl in Poes Garden probably

represent tertiary sandstones and tube wells tapping these granular zones yield 2 to 3 lps.

Ground water in Chennai district occurs in all the geological formations namely, the

archaean crystallines, gondwanas, tertiaries and alluvium and is developed by means of ring

wells, dug wells, filter point wells, bore wells and tube wells. The yield and depth range of

aquifers is given in the Table 1.

Table 1. The Yield and Depth Range of Chennai Aquifer

Formation Type of Well Depth Range

(Metres below ground level)

Yield in LPS

(Litres per second)

Alluvium Tubewell

Dugwell

10 to 30

6-11

1-12

0.058 to 1.16

Sandstone Tubewell 20 to 28 2 to 3

Gondwana Tubewell 20 to 60 1 to 3

Crystalline Borewell 10 to 15 Upto 4

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The alluvium covers the major part of the district. The alluvium consists of sand,

silts and clays. The thickness of alluvium varies from place to place and a maximum of 28

m is encountered in north Chennai near Perambur. Kilpauk water works area has 24 m thick

alluvium. The yield of the wells at Kilpauk and Tirumangalam tapping the productive

granular zones met within the alluvium is 25 lps and 6 lps for a drawdown of 7.21 and 0.22

m with a specific capacity of 206.35 and 40 lpm/m of drawdown respectively. In

Tondiarpet ground water is tapped mainly in the alluvium which extends to 80ft depth from

the surface and the depth of borewells in alluvium ranged between 60 to 80 ft and the yield

ranges from 4 to 6 lps. The permeability of the aquifer material obtained at a depth of ca.

20ft. ranges between 1.3 m/day to 2 m/day. The ground water is potable.

2.3 Existing Operations of Properties Adjacent to the Contaminated Site

A reconnaissance survey of properties adjacent to the site to assess the existing

operations around the site was conducted. Residential settlements and commercial small

scale industries lie on all sides of the site. Some of these industries use small quantities of

diesel for running diesel generators. There are no reported leaks from diesel storage tanks

from these industries.

2.4 Receptors Downstream of the Site

The site and the environment can be categorized as belonging to predominantly

domestic set up. The nearest receptors downstream of the site are domestic settlements and

small scale manufacturing industries. The coast lies at a distance of 600 metres eastward to

site. Groundwater is of potable quality and is extracted in the area for domestic use.

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3. Methodology

3.1 Soil Borings and Ground Water Sampling Locations

Following a close review of the topographical characteristics and the existing

features in the site, around 20 soil and groundwater boring locations were identified. The

aspects considered while locating the 20 soil boring locations were:

• Topographical characteristics

• Regional and local ground water flow direction

• Presence of stationary structures like metal structures/buildings etc.

It is to be mentioned drilling of boreholes could not be carried out in grid pattern due to

congested nature of the area, absence of open space and presence of roads with live electric

cables, sewer pipes, telephone cables, drinking water pipelines etc. These were field

limitations.The site map showing the soil and ground water bore locations are shown in the

figure 4 below.

3.2 Well Gauging and Inventory

We conducted an inventory of wells to map the plume i.e. to map wells that had

hydrocarbon contamination and wells that were free of hydrocarbon contamination. A

Solinst interface meter was used to identify the presence and depth of free phase

hydrocarbons in groundwater. The interface meter provides a continuous beep when free

phase hydrocarbons are present and an intermittent beep sound when water is detected. The

sensitivity of the interface probe is 0.5 cm. About 30 borewells around the contaminated

site were identified to map the free phase hydrocarbon plume. The well inventory is shown

in plate 1 and 2 of the Appendix 1. The existing borehole locations where well gauging was

carried out is shown figure 5. Also, the contaminated borewell locations were identified

and shown in figure 6.

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Figure 4. Locations of Exploratory Bore Wells (EBW)

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Figure 5. Location of Bore Wells Examined for Hydrocarbon Contamination

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Figure 6. Identification of Hydrocarbon Contaminated Bore Wells

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3.3 Drilling of Exploratory Borehole Location and Sampling Frequency

In addition to well inventory we identified 20 boreholes in open areas to determine

the presence of soil and ground water contamination and designated the 20 soil borings

with ID EBW 2 to EBW 21. A field GPS kit was used to map the borehole locations. The

coordinates of soil and ground water sampling locations were marked using the WGS UTM

Datum. Trial pits (Refer Appendix, Plate 3) were taken to make sure there were no live

cables and pipes to ensure safety.

3.4. Drilling of Boreholes for Soil Sampling

We conducted soil borings using 6 inch and 3 inch hand auger bits to a depth of 30

ft till water table was encountered. Representative samples were collected at every 1ft

depth that ran upto 30 ft. Trial pit was used to identify buried objects, live electric cables,

etc. The samples were collected and lithological observations were recorded such as odour,

moisture, contamination characteristics, lithology, extent of visible contamination etc. Use

of hand auger is shown in plate 4of the appendix.

3.5 Gas Sampling

When each boring reached the bottom of each 1ft interval representative soil

sample was collected using hand auger and as the sample was retrieved in a plastic bag, a

sampling tube with a silt filter was inserted that was attached to a gas monitoring device

into the plastic bag. The end of the tube was held at this depth for one to two minutes and

the maximum concentration of the parameters tested for was recorded. To minimize loss of

volatiles during the transfer of gas samples to a lab, we tested for the following gases in soil

in-situ.

• Volatile organic carbon (measured in ppm)

• Lower explosive limit (measured in %)

• Carbon monoxide (measured in ppm)

• Hydrogen sulphide ( measured in ppm)

All parameters were measured using gas /VOC monitor (AreaRAE) which is a multi-gas

detector. Soil sampling activity is shown in photographs 5 and 6 of the appendix. The gas

monitor used for gas measurement is shown in photograph 7 of the appendix.

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3.6 Drilling of Boreholes for Water Sampling

We drilled the boreholes through hand auger without using water or foam and by

this method representative samples were taken. These boreholes were the pre-selected sites

for the required sampling of ground water. Borings were drilled to a depth of 30 ft below

ground level using 6 inch drill bit. Once ground water samples were collected, we

backfilled the boreholes to at the surface to avoid potential surficial contamination from the

surface to reach the ground water. The hand auger with drill tools is shown in Photographs

7 and 8 of the appendix. Although water was initially encountered in the subsurface from

moisture in the interstitial pore-space at saturated zones, the boreholes are often incapable

of producing water adequate for sampling until deeper zones are exposed. Initially, we

attempted to collect ground water samples after drilling 1 m down below water table.

However due to collapse of soil and the presence of sand with poor permeability and slow

recuperation rate of ground water in to the borehole adequate volume of water could not be

retrieved from the well. We spent time and resources but failed to retrieve ground water

sample. Subsequently, we decided to drill to additional depths (approximately 4 ft) from

the water table to collect ground water sample.

3.7 Ground Water Sampling

The ground water samples were collected from the exploratory bore wells using a

disposable bailer. Prior to ground water sample collection from the borings, product and

water level measurements were collected from the borings using Solinst interface meter

probe. A disposable string was used to lower each bailer at each boring. Samples were

subsequently collected using these bailers. The hand auger was decontaminated prior to

use and between sample locations. To avoid cross-contamination of samples, first the

equipment was scrubbed with detergent and then by potable water to remove visible

contamination. Second, the equipment was thoroughly rinsed and scrubbed with potable

water prior to moving to new location. The QA/QC procedures mentioned in the sampling

protocol was followed. Each lab-supplied soil/ground water sample bottle was properly

labeled with the site ID, bottle number and date. The collected samples were packed with

adequate ice and were placed into a laboratory-supplied cooler and taken to the lab for

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further analysis. After sample collection, the boreholes were backfilled with cement to

prevent surficial contamination seeping below.

3.8 Field Analysis

The purpose of the site assessment is to ascertain the presence or absence of various

parameters using the most representative sample. To the extent possible, the samples were

analyzed in the field as quickly as they are first exposed. Elaborate transfers and shipping

procedures geared towards laboratory testing often cause loss of volatiles and in some

instances, change the sample matrix. Bearing this in mind, we field screened the soil and

ground water samples for certain parameters and obtained the results in the field.

3.9 Laboratory Analysis

The preliminary analytical studies at IITMadras were intended to qualitatively

assess the product and groundwater collected from the site. The free oil collected at the

borewells were diluted with Dichloromethane and analysed in Gas Chromatograph with

Mass Spectrograph. The groundwater samples were extracted with Dichloromethane as the

solvent and run in the GCMS. In addition commercially available Petrol and Diesel were

run in the GCMS for comparison. The GCMS can identify the different compounds based

on a library search as the peaks elute through the GC column and reach the detector.

Each petroleum product is a mixture of hundreds of different hydrocarbons which

makes quantitative analysis challenging. The product can be identified based on the typical

finger print it produces in GCMS chromatograms which varies depending on the density of

the compound. The lighter range of compounds like petrol with smaller number of carbon

atoms will have a distinct fingerprint compared to heavier range of product such as

lubricant oil. This can be used to identify the products. In addition different refineries may

have some specific signature chemical or ratios of specific compounds which is a useful tip

to identify the source of the products spilled.

3.10 Electrical Resistivity Tomography Survey

Electrical Resistivity Tomography (ERT) survey is usually conducted following the

various arrangements of four electrodes, two current and two potential, depending upon the

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specific purpose. Electrical resistivity of the rocks or sediments depends on the resistivity

of their mineral matrix and the fluid contained in its pore spaces. The electrical resistivity

of the soil can be considered as a proxy for the variety of soil physical properties that

includes the nature of the solid constituents (particle size distribution , mineralogy) ,

arrangement of voids (porosity , pore size distribution , connectivity) , the degree of water

saturation (water content),electrical resistivity of the fluid (solute concentration) and

temperature. Field data were collected at two cross sections (ERT1 and ERT 2) both

running in the east-west direction. The data were gathered to obtain a continuous coverage

of the subsurface along the line of investigation. A Wenner electrode configuration was

employed in the present study.

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4. Results and Discussion

4.1 Interpretation of Field Results

Well inventory was carried out in about 30 wells surrounding the contaminated

area. Solinst interface meter was used in the borewells which are basically domestic

borewells used by local people. It is understood that BPCL over the last 3 months has been

periodically recovering free phase hydrocarbons. Despite the recovery residents complain

about the presence of hydrocarbon product and VOC emissions in some of the borewells.

Free Phase Hydrocarbon contamination was observed in all the 9 wells of the Lane located

in Plot No. 225 TH road, few houses in VPK street. The wells in plot number 225 lie very

close to each other within distances of 2 metres. The product thickness was observed to be

in the range of 2 inches to 24 inches. The maximum product thickness was observed in well

number BW 222 with a thickness of 24 inches.

The nature of well construction could be the reason for varying thickness of product

in these borewells. Normally in a small area the product thickness should be uniform. For

monitoring product thickness in contaminated areas, the borewell must be constructed with

slotted casings from above water table to the bottom of the well (for the entire water

column). Floating product on ground water can then be accurately recorded in these wells.

In case of plain casings intercepting water level, product thickness will be very much

reduced than the actual.

In VPK street few houses on either side of BPCL pipeline exhibit high level of free

phase product contamination. House Number 5/20 has maximum product thickness of 2.75

ft (33 inches). Dhal Mill which has a borewell showed 3 inches. Similarly 4 other houses

in the lane have recorded 2 to 6 inches of product. One borewell in Devi polymers recorded

oil of about 4 inches and bailing-out has been conducted on and off in this well.

4.2 Field Observations During Soil Boring

Overall the top soil was filled material with graded gravels, cobbles of building

material mixed with brown to dark brown sandy silt. Boreholes were drilled to a depth of

30 ft. The local geology encountered was unconsolidated alluvium comprising

predominantly alternating layers of brown to light brown fine and medium silty sand. Clay

intercalations were not observed in any of the borewells. The particle size distribution

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indicated the soil to be medium to fine sand and the gradation does not vary significantly

over the study area (Figure 7).

Figure 7. Particle Size Distribution of Soil Collected from Borewell # 16

At depths of beyond 22 ft the colour of the sand changed from light brown to grey

to whitish grey fine sand. At depth of 27 to 28 ft fine sandy silt was encountered. Water

table was encountered at depth of 27 to 29 ft below ground level. Hydrocarbon

contamination in soil was observed in boreholes drilled in Devi Polymers, Plot No. 225 TH

road (lane), Agastya Theatre, Gayathri Nursing home, Dr.Aruns house and Dhal Mill. In

most of the wells, hydrocarbon contamination in soil was observed from depth of 19 ftto 28

ft (water table depth). In the case of EBW# 18, soil contamination was observed at a

shallow depth of 6 ft. and extended up to the water table (29 ft.) indicating that this location

(VPK street) could be closer to the source of the spill. In some boreholes moisture with

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Depth of borewell in feet

pan

> 0.075 mm

> 0.150 mm

> 0.212 mm

> 0.425 mm

> 0.600 mm

> 1 mm

> 2 mm

> 4.75 mm

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decomposed odour was observed between 15 to 20 ft depth probably indicating sewerage

pollution. Wherever soil contamination was observed heavy odour of hydrocarbon due to

release of Volatile Organic Compounds (VOC) was observed. MultiraeGas detector

equipment recorded high VOC readings in the range of 0 to 212 ppm of VOC’s. The soil

borelogs are shown in Figure 8. The VOC readings observed in different exploratory

boreholes are summarized in Table 2.

Figure 8. Soil Borelog Indicating Bore Well Contamination

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Table 2. Contamination Characteristics of Exploratory Wells

EBW No

Depth to Product

Depth to Water, ft

Status of Soil Contamination

VOC range(ppm)

Depth (feet)

2 ND 27.6 HC contaminated 98.9 - 212 15 - 30 3 ND 27.5 HC contaminated 10.5 - 11 29 - 30 4 ND 27.4 No HC contamination 0 0 5 ND 27.5 HC contaminated 3.1 - 61.7 18 - 28 6 28.0 28.2 HC contaminated 11.1 - 169 20 - 28 7 ND 27.5 No HC contamination 0 0 8 ND 28.5 No HC contamination 0 0 9 ND 29.0 No HC contamination 0 0 10 ND 27.2 HC contaminated 22.6 - 190 19 - 26 11 ND 27.6 No HC contamination 0 0 12 ND 26.7 HC contaminated 11.9 - 141 19 – 26 13 ND 28.0 No HC contamination 0 0 14 ND 27.0 HC contaminated 20.4 - 173 21 – 26 15 ND 27.0 No HC Contaminated 0 0 16 28.2 28.3 HC contamination 11 – 194 18.0 – 29 17 27.0 27.1 HC contamination 6.5- 129 11 - 29 18 27.6 27.7 HC contamination 29 – 195 6 – 29 19 ND 30.5 No HC Contaminated 0 0 20 ND ND HC contamination 10.5- 132 12- 25 21 ND ND HC contamination 2 -207 18 -27

HC – Hydrocarbon; ND – Not determined

4.3 Gas Chromatography Results

A comparison of chromatograms presented in Figures 9ato 9c and the overlay

image Figure 9e indicates that the oil collected from the borewell is matching with the

commercial diesel and not commercial petrol. Petrol has only the lighter fractions of the

crude with compounds having less than nine carbon atoms. These compounds have low

boiling point and elute out at shorter retention times. Diesel with a large range of

compounds with higher number of carbon atoms has a distinct signature as shown in Figure

9a.

The zoomed in images presented in Figures 9f and 9g indicate slight variations in

the commercial diesel and diesel from the site. The mass of lighter products (peaks at

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retention times 7.5 and 5.5) are slightly more in the oil collected at site compared to

commercial diesel. This could be due to slight variations in diesel grades or an earlier petrol

spill. It is likely to have petrol since petrol was also pumped through the pipeline

alternating with diesel. But the quantity is only seen as traces compared to large diesel

peaks. The groundwater extracts from bore well (Figure 9d) also indicate compounds from

both the lighter and heavier fraction dissolved in the groundwater.

Figure 9a.Chromatogram of Commercial Diesel.

Figure 9b. Chromatogram of Commercial Petrol

Figure 9c.Chromatogram of the Oil Collected from Borewell in House# 223

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Figure 9d. Chromatogram of Groundwater Collected from Devi Polymers

Figure 9e.Overlay of the Chromatograms of Commercial Diesel and Oil collected at Spill Site

Figure 9f.Chromatogram (First portion) with enlarged image of Lighter Fractions of the Oil.

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Figure 9g. Chromatogram (second half) with Enlarged Image of Heavier Fractions of the Oil.

4.4 Electrical Resistivity Tomography Results

The lithological section shown in figure 10a can be interpreted as four layer model.

In both ERT-1 and ERT 2 there are low resistivity contours up to the 1m depth from the

surface in the top part of the profile indicating the presence of saturated silty sand with

cobbles and pebbles. High resistivity contour suggests the presence of medium to fine

unsaturated silty sand up to the 4 m and 4.5 m depth for ERT-1 and ERT-2, respectively.

Saturated oil sands generally have low resistive value than the alluvium and some of the

value is overlapped between the two. Both ERT-1 and ERT-2 shows slightly low resistive

value of 100 - 400Ω suggesting the presence of the alluvium of fine to silty sand with oil

spill on the sands at a depth of around 9m. Most of the oil seepage is visible at chainage

16m and around 32 to 37m.The low resistive region with contour 10-100 Ω suggest the

presence of the ground water aquifer. The contrast in the resistivity of the sand at third and

fourth layer shows the presence of the oil only upto third layer, i.e. above groundwater

table.

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Figure 10a. Electrical Resistivity Tomography (ERT-1) of Tondiarpet Oil Spill Site

Figure 10b. Electrical Resistivity Tomography (ERT-2) of Tondiarpet Oil Spill Site

4.5 Delineation of Plume Extent

The site harbors a heavy cluster of residential and commercial units which poses a

huge challenge in the demarcation of contaminated plume and its subsurface movement.

One cannot rely fully on the collected data to quantify the extent of remediation since the

depth of the screening of the existing bore wells is an unknown. Plume delineation was

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done based on the collected free phase hydrocarbon product thickness in existing borewells

and newly drilled exploratory borewells. The plume outputs were created using 3D

analysis GIS software tools. The plume output for the free phase product floating on

ground water as of October 2013 is shown in figure 11a. The areal extent of the plume is

about 7141 m2 and its volume is estimated to be around 270 m3. These estimates are arrived

at using de Pastrovich et al. (1979) method wherein the oil in the formation is estimated to

be 1/4th of the oil in the monitoring wells.

When the trench was excavated below the pipeline, there was oil soaked soil at a

shallow depths. There wasn’t adequate time for allowing oil seepage in the exploratory

borewell. Assuming an equivalent amount of oil could be present there as in the adjacent

well, about 30 inches of oil right beneath the trench was assumed and a simulation was

performed (Fig. 11b). The simulation indicated the area and volume of contamination

plume to be around 7580 m2 and 320 m3, respectively. This scenario can be considered as

an upper bound of the contamination. Based on the data provided by BPCL, they had

bailed out about 3493 litres of oil from the contaminated wells as of December 7, 2013 .

Moreover, the available data indicates that the movement of the oil plume is

predominantly eastward during non-pumping periods following the ground water

gradient. During pumping times specifically in summer months, it is governed by

borewell pumping rates and spread slightly north and mostly south. Moreover, extraction

of the oil and oil mixed water has influenced the oil plume movement since the time the

recovery operations started. This indicates that the extraction of water from the aquifer

plays a huge role in the mobility of groundwater and hence remediation efforts should be

planned accordingly.

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Figure 11a. Map Showing the Thickness of Oil Plume Floating above the

Ground Water Table as of October 2013

Figure 11b. Map Showing the Thickness of the Oil Plume considering the presence of

oil in the trench

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4.6 Soil Contamination in the vadose zone

Shallow unconfined ground water table conditions prevail in the area. The water

level ranges from 18 ft during post monsoon and 28 ft below ground level during pre-

monsoon period. Soil contamination spread is predominantly due to initial downward oil

movement by gravity immediately after spill and horizontal plume movement due to

gradient. Subsequently due to monsoon fluctuation in water level the oil could have also

moved up and down vertically. Majority of the oil pools above the water table and the

maximum volatile organic carbon is expected close to the water table or in regions of

coarse sand with high permeability. Oil saturation in the soil was estimated onsite using

the VOC monitor. It was also cross checked with analysis of volatile suspended solid in the

soil samples brought back to the laboratory.

Figure 12a and b show the oil contamination in the vadose zone or the zone above

the water table. It is observed that in well EBW2 no VOC was measured upto 15 feet and

then the values increased level beyond that upto the water table. All borewells away from

the pipeline showed a VSS profile similar to EBW2. Close to the pipeline where the leak

could have originated, the VOC /VSS traces are likely to present in the top layers of the

vadose zone since the spilled free phase, hydrocarbons penetrate soil and reach

groundwater vertically. Subsequently plume moves along the direction where there is

greater groundwater abstraction if there were no recovery of oil. This was observed by the

borewells drilled below the pipeline ( EBW17 and 18). Unlike the other borewells, the oil

was observed in the soil just below the pipeline and extended all the way to the water table

(Figure 12). Maximum Volatile suspended solids was observed close to the water table in

the zone just below the pipeline indicating that the source could be somewhere below the

pipeline (Photoplate # 8-9, Appendix). The VSS value as are quite high in the range of 5-20

g/kg which may lead to large release of toxic /flammable compounds in the atmosphere

during excavation operations and slow release in unpaved areas under normal conditions.

It can also be noted that the VSS data is high at the zone where the coarse grained sand is

present. This confirms the capillary entrapment phenomena which is well established in

literature. The coarse sand will hold the oil to a larger extent because the fine sand below

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with the small pore size will exert a very high capillary resistance to the entry of oil into

their pores.

Figure 12a. Volatile Solids Extracted from the Contaminated Soils.

Note: EBW-17 is located beneath the Excavated Trench; EBW-2 away from the pipeline

The VOC data measured on field is given in the figure 12b below. From Figure 12 b it was

found that the VOC and VSS data closely corroborated indicating shallow contamination

close to the pipeline and deeper contamination away from the pipeline. But the VOC

values in the vadose zone were quite high in many layers close to the water table.

It must be noted that these values are only indicative of the presence and degree of

contamination and do not give the exact quantification. This is because they were measured

onsite and not under controlled conditions like the VSS presented in Table 12.

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Figure 12 b Volatile Organic carbons measured on site at different depths

Bore No/Depth

(ft) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 1 2 Legend 3 Not measured 4 No Contamination 5 1-50 ppm (VOC Value) 6 50 -100 ppm (Voc value) 7 101-150 ppm (VOC value) 8 151-240 ppm(VOC Value) 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

27 28

29

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4.7 Extent of Ground water Contamination

The groundwater samples were collected from regions within the oil contamination

and beyond. The samples were analysed for 60 VOCs including petroleum hydrocarbons at

SGS laboratories (Appendix II). The dissolved phase plume map for benzene and toluene

are shown below (Figures 13 and 14). Benzene is a well known carcinogen and toluene is a

potential neuro toxin. The USEPA set maximum contaminant level for benzene and toluene

are 5 ug/l and 1 mg/l, respectively. The dissolved plume map indicates a maximum

concentration of the benzene and toluene in groundwater as high as 23 ppm and 108 ppm,

respectively. Moreover, the maximum concentration for both benzene and toluene are

found at VPK street. It can also be noted that the Benzene and Toluene dissolved plume

extends beyond the oil plume. This is because it is in the dissolved phase and moved along

with water.

Figure 13. Dissolved Phase Plume Map of Benzene

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Figure 14. Dissolved Phase Plume Map of Toluene

The dissolved Benzene and Toluene plumes seems to be moving in the

North eastern direction which could be driven by local hydraulic gradients due to pumping.

The future predictions of these plume migrations is uncertain due to the extensive pumping

in the region with multiple borewells. But the contamination of the groundwater will be a

continuous phenomenon and long term as long as there is oil in the aquifer. Literature

suggests that immediate action must be taken if the water shows Benzene and Toluene

concentrations higher than permissible levels. The use of this water must be avoided until

the aquifer is cleaned up and alternative water supply should be provided.

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5. Conclusions and Suggestions for Remediation

A comprehensive evaluation of the site data were collected from existing boreholes

belonging to residents and by conducting resistivity survey and drilling of 20 new

exploratory boreholes in available open spaces.

5.1 Characterization of Spill Site

Based on the available dataset, we have found oil contamination of the aquifer in the

following forms:

1. A large volume of oil floating as a pool on top of the groundwater table as a light

non aqueous phase liquid

2. A significant volume of oil entrapped to the soil as blobs in the vicinity of the

water table both above and below in the vadose zone and saturated layer.

3. Dissolved phase in the groundwater in the vicinity of the oil blobs and oil pool

and moving downstream.

The spill event could be visualized as shown in the figure 15.

5.2 Transport Through Porous Media

Movement of petroleum compounds in the subsurface is controlled by several

processes described in the following simplified scenario (Figure 15). Upon release to the

environment, it will migrate downward under the force of gravity. If a small volume of

petroleum (Light Non Aqueous Phase Liquid, LNAPL) is released to the subsurface, it will

move through the unsaturated zone where a fraction of the hydrocarbon will be retained by

capillary forces as residual globules in the soil pores, thereby depleting the contiguous

liquid mass until movement ceases. If sufficient quantity of petroleum (LNAPL) is

released, it will migrate until it encounters a physical barrier (e.g., low permeability strata)

or is affected by buoyancy forces near the water table. Once the capillary fringe is reached,

the LNAPL may move laterally as a continuous, free-phase layer along the upper boundary

of the water-saturated zone due to gravity and capillary forces.

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Figure 15.Migration of a Petroleum Spill. Figure has been adapted from Delin and others, 1998, USGS Fact Sheet FS-084-98.

Petroleum components may exist in any of four phases within the subsurface. The

NAPL, aqueous, and gaseous phases were mentioned above. Contaminants may also

partition to the solid-phase material (i.e. soil or aquifer materials). In the unsaturated zone

contaminants may exist in all four phases (Figure 15). In the saturated zone NAPL-related

contaminants may be present in the aqueous, solid, and NAPL phases. NAPL constituents

may partition, or move from one phase to another, depending on environmental conditions

(Figure 15). For example, soluble components may dissolve from the NAPL into passing

ground water. The same molecule may adsorb onto a solid surface, and subsequently

desorb into passing ground water. The tendency for a contaminant to partition from one

phase to another may be described by partition coefficients such as Henry's Law constant

for partitioning between water and soil gas. These empirical coefficients are dependent on

the properties of the subsurface materials and the NAPL. A clear understanding of the

phase distribution of contaminants is critical to evaluating remedial decisions (Huling and

Weaver, 1991). It is important to note that this distribution is not static and may vary over

time due to remedial actions and natural processes

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Figure 16. Entrapment in Soil and Partition of Oil into Various Compartments

5.3 Transformations in the subsurface

The subsurface fate of chemicals in the four phases as illustrated in Figure 16is

largely determined by volatilization, dissolution, sorption, and degradation processes.

Dissolution, sorption and degradation of an LNAPL are discussed elaborately since they

are the transformation processes which determine the concentrations of pollutants in

ground water.

Dissolution

A NAPL in physical contact with ground water will dissolve (solubilize, partition)

into the aqueous phase. The solubility of an organic compound is the equilibrium

concentration of the compound in water at a specified temperature and pressure. For all

practical purposes, the solubility represents the maximum concentration of that compound

in water. The solubilities of the compounds most commonly found at Superfund sites range

over several orders of magnitude. Several parameters affecting solubility include

temperature, pH, cosolvents, dissolved organic matter, and dissolved inorganic compounds

(salinity). For a multicomponent NAPL in contact with water, the equilibrium dissolved-

phase concentrations may be estimated using the solubility of the pure liquid in water and

its mole fraction in the NAPL mixture (Feenstra et al., 1991). The maximum concentration

that can be achieved in this scenario is referred to as the effective solubility, as indicated in

equation (1).

Se i = Xi Si (1)

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Where Se i = effective aqueous solubility of compound i in NAPL mixture

Xi = mole fraction of compound i in NAPL mixture

Si = aqueous solubility of the pure-phase compound

For example, for petroleum containing numerous compounds (Johnson et al.,

1990b), the mole fractions of benzene are 0.0076 and 0.0021 in fresh and aged samples,

respectively. The solubility for benzene is 1780 mg/l (U.S.EPA, 1990). Yet, the predicted

effective solubility would be only 13.5 mg/l and 3.78 mg/l for fresh and weathered

gasoline, respectively. The more soluble compound will potentially partition into ground

water more readily than the less soluble compound. According, less soluble compounds

will primarily be associated with the NAPL phase and dissolution and transport in the

aqueous phase will be limited relative to more soluble components.

The effective solubility represents the concentration that may occur at equilibrium

under ideal conditions. Laboratory studies (Banerjee, 1984) indicate that effective

solubilities calculated using Equation 1 are reasonable approximations for mixtures of

organic liquids that are hydrophobic, structurally similar, and have low solubilities.

Effective solubilities of components in more complex mixtures, such as petroleum

products, appear to be in error by no more than a factor of two (Leinonen and Mackay,

1973). However, the degree to which these compounds partition to the water phase is a

function of many variables including cosolvency (Rao et al., 1991). Cosolvency effects

may occur in cases where dissolution of highly soluble components (e.g., alcohols)

significantly increase the solubility of other components. In general, higher dissolution

rates may be associated with higher ground-water velocities, higher LNAPL saturation in

the subsurface, increased contact area between LNAPL and water, and LNAPLs with a

high fraction of soluble components (Mercer and Cohen, 1990; Miller et al., 1990).

However, recent studies (e.g., Powers et al., 1992) indicate that nonequilibrium effects may

limit contaminant mass transfer by dissolution under certain conditions such as high

groundwater velocity. Laboratory and modeling studies conducted by many researchers

(e.g., Borden and Kao, 1992; Geller and Hunt, 1993; Powers et al., 1991) indicate that

complete dissolution of an LNAPL may require hundreds or thousands of pore volumes of

water under ideal field conditions. These studies observed initially high aqueous

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contaminant concentrations which were followed by a period of rapid decline and an

asymptotic period during which concentrations declined slowly.

Sorption

Sorption is defined as the interaction of a contaminant with a solid (Piwoni and Keeley,

1990). In soil or aquifer material contaminated with LNAPL, contaminants from the

LNAPL will partition onto solid phase material. The primary pathway in which this process

occurs is through the water phase, as indicated in Figure 16. For example, when LNAPL is

released into the subsurface, components will dissolve into the aqueous phase, then

partition onto aquifer material. Numerous parameters affect sorption at hazardous waste

sites including solubility, polarity, ionic charge, pH, redox potential, and the octanol/water

partition coefficient (Piwoni and Keeley, 1990). In general, solid-phase (adsorbed)

contaminants may represent a small fraction of the total contaminant mass in soil and

aquifer material where continuous phase or residual NAPL exists. The majority of the

contaminant mass in these systems is typically present in the nonaqueous liquid phase.

Desorption of the contaminant (i.e. mass transfer of contaminant from the solid phase to the

water phase) is often a rate-limited step and is partially responsible for the tailing effect

commonly observed in ground-water pump-and-treat systems.

Biodegradation

Many of the petroleum compounds are amenable to biological degradation in the

aqueous phase by naturally occurring microorganisms in the subsurface. However, there is

an important distinction between aqueous-phase and NAPL biodegradation. The distinction

is the inability to create and maintain conditions that are conducive to microbial activity

within a NAPL. In brief, biodegradation of pure phase hydrocarbon does not appear to be

practical and has not been demonstrated. Considerable research has focused on evaluating

aerobic and anaerobic biodegradation and transformation processes. These processes play

an important role in the ultimate fate of petroleum in the subsurface, both in the form of

naturally occurring and actively engineered remediation processes (Norris et al., 1994).

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5.4 Implications of Petroleum Contamination on Human Health

The partitioning of petroleum compounds in air, water and soil indicates that there is

a risk by inhalation, drinking and bathing with contaminated water and soil during

excavation scenario. The International Agency for Research on Cancer (IARC) has

determined that one major component of petroleum , Benzene is carcinogenic to humans.

IARC has also determined that other petroleum compounds such as benzo[a]pyrene are

probably and possibly carcinogenic to humans. Some of the petroleum compounds can

affect the central nervous system, can cause headaches and dizziness at high levels in the

air, nerve disorder called "peripheral neuropathy," consisting of numbness in the feet and

legs. Other compounds can cause effects on the blood, immune system, lungs, skin, and

eyes. Animal studies have shown effects on the lungs, central nervous system, liver, and

kidney from exposure to petroleum compounds. Some petroleum compounds have also

been shown to affect reproduction and the developing fetus in animals.

5.5 Major Findings from the Investigations

• Fill material to 3 ft followed by different grades of alluvial sand upto 30 ft was the

geology observed in the area.

• Free phase hydrocarbon is present in 15 existing borewells and 3 newly drilled

boreholes.

• The product thickness in borewells ranges from 1 inch to 33 inches.

• Free phase hydrocarbon is present on either side of the BPCL pipeline close to

junction of TH road and Varadaja Perumal Koil street. The plume is confined to a

limited area.

• A review of plume delineation map indicates that the source of hydrocarbon leak is

somewhere in VPK street close to TH Road. This was confirmed by drilling

borewells below the pipeline in that stretch of the road.

• The areal extent of the oil spread in the aquifer is around 7141 m2 – 7580 m2 and

volume of the free phase hydrocarbon spill is approximately 270 m3 - 320 m3,

respectively. These numbers are based on the interpolation of the oil depth data

measured on field.

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• The free product in the borewells in the residences indicated diesel range organics

whereas the free product in the borwells dug below the pipeline indicated a highly

viscous heavier fraction. This is quite possible since multiple products were

pumped in these pipelines.

• Soil contamination was observed in 12 out of 20 newly drilled exploratory wells.

• The depth of soil contamination starts from 19 to 20 ft below ground level in all

regions except the zones below the pipeline where it was much shallow and close to

the bottom of the pipeline.

• The contaminated soil thickness ranges between 10 to 12 ft spread over a limited

area. Contamination of soil in the range 5g/kg to 20 g/kg was observed above and

below the water table indicating the smearing of the oil pool due to water table

fluctuation.

• Ground water in the region was contaminated with many compounds as listed in the

Appendix III. Benzene and Toluene in groundwater as high as 23 ppm and 108

ppm, respectively

5.6 Future Directions and Challenges

Based on our results and observations it is recommended that the following steps

could be undertaken for complete cleanup of the area:

1. Installing recovery wells in the trench close to the source and in the locations which

show maximum standing oil depths

2. Removal of free product through a combination of proven techniques such as dual

phase pumping, surfactant enhanced removal or other proven technologies.

3. Removal of trapped oil from the vadose zone through proven techniques such as soil

vapour extraction

4. Insitu treatment of contaminated groundwater and removal of blobs in saturated

zone by chemical or biological methods.

5. Installation of monitoring wells at the higher contamination zones and periphery of

the dissolved plume to monitor the effect of oil removal and ground water

remediation.

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5.7 Description of Remediation Technology

Installation of Recovery/Monitoring Wells

Installation of monitoring wells will enable us to assess the changes in groundwater

characteristics and variation in the groundwater flow direction over a period of time.

Drilling of a monitoring well in a contaminated area should be done with caution to avoid

cross contamination of the aquifer material from one place to another. Moreover, a

lithologic log has to be recorded that documents the textural and visibly determinable

properties of the aquifer material with depth. Samples must be collected at regular intervals

especially when difference texture or geology is observed. A section of the typical

monitoring well for a shallow and a deep aquifer is shown in the figure below.

Figure 17: Monitoring Wells in a Shallow and a Deep aquifer.

Source: Alberta Agriculture and Rural Development.

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The well tube is typically made of PVC material. The length of the well screen is

dependent upon the thickness of the hydrogeologic unit, the vertical scale of investigation

and the specific requirements of the monitoring program. Moreover, the length of the

screen should be such that it allows for sufficient level of bentonite seal application below

ground level. The annular space between the screened section of the well and the borehole

is filled with sandy material up the depth of which covers the complete screened length.

Beyond the filter sand pack, watertight bentonite seals are applied which acts as a primary

seal. Above the primary seal, secondary hydrated bentonite material is filled. The top of the

monitoring well should be capped and a small air vent is provided to allow free air

movement. Finally, to protect the monitoring well, a steel casing with a lock provision may

be provided. Moreover, to avoid surface water from entering into the well a small mound is

created at the ground level. The monitoring wells should be installed with the help of

experienced personnel under professional supervision.

Removal of free phase oil The most common strategy for maximizing the recovery of free-phase LNAPL is

to pump (Figure 17) the LNAPL layer relatively slowly in order to keep the LNAPL mass

as a continuous flowing mass (Charbeneau et al., 1989; and Abdul, 1992). Water

pumping is avoided or carefully controlled to minimize smearing of the LNAPL layer,

although some water pumping may be helpful to prevent upconing of the water table.

Although high water pumping rates will initially yield a higher hydrocarbon recovery

rate, the ultimate recovery will be greatly reduced because much of the LNAPL that was

originally “flowable” (that is, a free phase) is smeared into uncontaminated soil as the

water table is depressed, converting it to an “unflowable” residual LNAPL.

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Figure 18. NAPL Recovery systems: (a)Two well - two pump (b) One well- two

pump

Soil Vapor Extraction (SVE)

Soil pore extraction is an important technology to treat spills of volatile organic

compounds in the unsaturated zone. Vacuum extraction involves passing large volumes

of air through or close to a contaminated spill using an air circulation system. The organic

compounds volatilize or evaporate into the air and are transported to the surface where

they are collected and treated. This technology is suited to remove volatile compounds

that are trapped at residual saturation and the free product layers. Hence this method

works well for the contaminants that have high vapor pressure and low water solubility.

Further, this method is more suited for subsurface system that is relatively permeable and

homogeneous. Since soil surface would lead to short-circuiting of the airflow, the site has

to be covered by an impermeable surface during operation (Suthersan, 1997). In

comparison to pump and treat and excavation, SVE can be cost effective and more

efficient.

A typical soil vapor extraction system is shown in Figure 18. The key design

parameters are the vapor pressure of the volatile chemicals in the NAPLs and the

permeability of the zone that will be used for vapor extraction. It consists of one or more

extraction wells, one or more injection wells, vacuum pumps or air blowers, flow meters

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and controllers and a vapor treatment unit. Extraction wells are typically designed to fully

penetrate the unsaturated zone to the capillary fringe. Vapor treatment may not be

required if the emission rates are low or if they are easily degraded in the atmosphere.

Typical treatment systems include liquid-vapor condensation, incineration, catalytic

conversion or granular activated carbon adsorption.

Figure 19. A Typical Soil Vapor Extraction System

The major design criteria for an SVE system are as follows: the required vacuum

to induce adequate airflow and its radius of influence, air flow rates to achieve adequate

mass removal, number of vent wells, well screen positioning, monitoring of soil moisture

content, passive well placement, off-gas treatment technology, maintenance, operation

and remote monitoring, underground piping and well design, closure SVE system

management. Some of the above criteria can be ascertained a priori by conducting field-

pilot study and bench-scale laboratory tests. Once the design parameters are obtained the

various design approaches to plan an SVE system are(1) empirical approach(2) radius of

influence approach and (3) modeling approach.

While soil vapor extraction is primarily directed at remediation of NAPLs in

unsaturated soils, it can be adapted to the removal of volatile hydrocarbons in NAPLs

from the saturated zone. First, there will be some transport of volatile organics from

contaminated ground water into an air stream being forced across the water table by a soil

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vapor extraction system. However, a much more important process occurs when the

water table is depressed, either intentionally or inadvertently, by a ground water pumping

system, thereby exposing the former saturated zone to the effects ofa soil vapor extraction

system.

Pump and Treat Remediation

In cases where the water table cannot be depressed to allow soil venting, clean

ground water can be drawn across the NAPL zone to dissolve soluble organic for

subsequent removal by a ground water pump-and-treat system. The treatment will be

done exsitu on the ground surface using air stripper or carbon adsorption towers. In most

cases this approach will remove some quantities of contaminant mass, but will be im-

practicable for restoring aquifers to drinking-water standards.

Insitu Chemical Oxidation

In situ chemical oxidation, also referred to as ISCO, is an aggressive remediation

technology that has been applied to a wide range of volatile and semivolatile hazardous

contaminants, including DNAPL source zones and the dissolved-phase chemicals

emanating from the source zones. Chemical oxidation typically involves

reduction/oxidation (redox) reactions that chemically convert hazardous compounds to

nonhazardous or less toxic compounds that are more stable, less mobile, or inert. Redox

reactions involve the transfer of electrons from one compound to another. Specifically,

one reactant is oxidized (loses electrons) and one is reduced (gains electrons). The

oxidizing agents most commonly used for treatment of hazardous contaminants in soil

and groundwater are hydrogen peroxide, catalyzed hydrogen peroxide, potassium

permanganate, sodium permanganate, sodium persulfate, and ozone. Each oxidant has

advantages and limitations, and while applicable to soil contamination and some source

zone contamination, they have been applied primarily toward remediating groundwater.

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Aerobic/Anaerobic in Situ Bioremediation

Before adopting the insitu bioremediation process the feasibility of the process

must be studied. The important factors to be evaluated are biodegradability of

contaminants, mineralization potential of the compounds, specific microbial substrate and

other conditions, availability of nutrients, hydrogeology of the site, extent and

distribution of the contamination, and biogeochemical parameters.

Existing literature on biodegradability studies indicate that in the case of LNAPL

contamination which includes a mixture of hydrocarbons, C1 to C15 compounds are

easily biodegradable. C12 to C20 hydrocarbons are biodegraded with moderate easiness

whereas polyaromatic hydrocarbons (PAH) are very difficult to degrade (Suthersan,

1997). Moreover, the mechanism of degradation of the above compounds can be vastly

different. Lighter hydrocarbons can undergo aerobic degradation with oxygen as a

terminal electron acceptor whereas PAHs are prone to be degraded under a

cometabolistic pathway. Since different pathways are involved in the contaminant

degradation process, the essential parameters (e.g., redox, nutrient availability, dissolved

oxygen) are to be maintained for the specific reaction to occur. Moreover, the site

hydrogeology in terms of hydraulic conductivity of the aquifer, depth to the water table

and thickness of the saturated zone should be ascertained. Further, microbial

characterization studies (viable bacterial counts) and contaminant plume demarcation will

aid in the proper design of insitu bioremediation system.

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Insitu bioremediation process can be achieved via two methods. They are

bioaugmentation and biostimulation. Bioaugmentation is the process of adding

exogeneous microbes to the subsurface that is targeted towards a specific contaminant.

Biostimulationinvloves the addition of electron acceptor or growth supporting nutrients

that could enhance the activity of microorganisms.The process is intended to stimulate

the indigenous subsurface microorganisms by the addition of nutrients and/or an electron

acceptor to biodegrade the contaminants of concern. For the aerobic degradation of the

organic contaminant, usually hydrogen peroxide is injected which could supply oxygen

for aerobic biodegradation.In the case of enhanced anaerobic degradation, nitrate

feedstockis injected. The nitrate feedstock is preferred as a terminal electron acceptor

because of it is high water solubility. Moreover, easily degradable organic substrate

(acetate, lactic acid, sucrose etc.) is injected in some cases to enhance the cometabolic

degradation of highly recalcitrant hydrocarbons such as PAHs. Hence in the case of

contamination of the subsurface by a mixture of contaminants a sequential aerobic and

anaerobic degradation design is preferred.

A typical bioremediation system is shown in Figure 20. In contrast to other

remediation techniques that transfer the contaminants from one phase to the other, in situ

biorestoration offers partial or complete destruction of the contaminants. Partial

destruction takes place usually because the chemicals may not all be available to the

microorganisms due to transport limitations or because the chemicals may not be

completely mineralized but rather biotransformed to other organic chemicals.

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Figure 20. Insitu Aerobic Bioremediation System

In situ bioremediation might offer attractive economic benefits because it

precludes the need for excavation, transportation, and disposal costs. Additionally, insitu

remediation can be used to treat contaminants that are sorbed to the aquifer matrix and

dissolved in the groundwater simultaneously. The disadvantage could be the slow rates of

biodegradation and the possibility of generating undesirable intermediate compounds

during the biodegradation process that are more persistent in the environment than the

parent compound.

In situ biodegradation can be considered to be a polishing step to the NAPL

dissolution process. In cases where large amounts of NAPL are trapped in the subsurface,

in situ biodegradation will proceed relatively slowly because of the limited solubility of

oxygen in the injection water. Application of biodegradation is most effective near the

end stages of a remediation process, where large volumesof ground water are required to

remove small masses of hydrocarbon. Aerobic biodegradation is applicable to sites

contaminated with most petroleum-related LNAPLs and some polyaromatic

hydrocarbons (PAHs).

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Air sparging: Air sparging is an in situ remedial technology that reduces concentrations of

volatile constituents in petroleum products that are adsorbed to soils and dissolved in

groundwater. This technology, which is also known as "in situ air stripping" and "in situ

volatilization," involves the injection of contaminant-free air into the subsurface saturated

zone, enabling a phase transfer of hydrocarbons from a dissolved state to a vapor phase.

The air is then vented through the unsaturated zone.

Air sparging is most often used together with soil vapor extraction (SVE), but it can also be

used with other remedial technologies. When air sparging (AS) is combined with SVE, the

SVE system creates a negative pressure in the unsaturated zone through a series of

extraction wells to control the vapor plume migration. This combined system is called

AS/SVE When used appropriately, air sparging has been found to be effective in reducing

concentrations of volatile organic compounds (VOCs) found in petroleum products at

underground storage tank (UST) sites. Air sparging is generally more applicable to the

lighter gasoline constituents (i.e., benzene, ethylbenzene, toluene, and xylene [BTEX]),

because they readily transfer from the dissolved to the gaseous phase. Appropriate use of

air sparging may require that it be combined with other remedial methods (e.g., SVE or

pump-and-treat). The airsparging can also trigger and enhance natural bioremediation of

contaminants in the ground water due to the injection of oxygen.

Figure 21: Air sparging for volatilization and Bioremediation of contaminants

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5.8 Concluding Remarks:

Oil spills are quite common in areas where oil is handled. Recent report of the American

petroleum Industry (2009) reports the following data ( Table 3) which indicates the

figures for volume of oil spilled in U.S.A from various sources in billion barrels. It is

important to take preventive measures to ensure that quantum spilled due to human

errors is minimum. Leak detection systems with online monitoring and alarm systems can

prevent major spills. The oil facilities should be located away from residential areas to

minimize disasters and health impacts. The spill response plan should be prepared and

action taken immediately in the event of a spill to mitigate environmental damage.

There is a need to create a similar data base on oil spills in India so that we can

consolidate the quantum of spills and draft a spill response plan. This transparency

necessitates a relook at the environment policy and regulation so that we can enable the

oil industry to report spills

Table 3: Estimated Average Annual U.S. Oil Spillage from Petroleum Industry Sources (bbl)

Source 1969-1977 1978-1987 1988-1997 1998-2007 PRODUCTION 31,435 8,701 15,183 9,938 Offshore Platform Spills 25,858 1,344 1,814 1,273 Offshore Pipelines 4,482 3,462 8,127 2,614 Offshore Supply Vessels 95 245 48 10 Inland Production Wells 1,000 3,650 5,194 6,041 REFINING 3,000 3,512 15,015 12,136 Refinery Spills 3,000 3,512 15,015 12,136 TRANSPORT 488,662 301,645 190,753 96,393 Coastal/Inland Pipelines 259,340 181,196 118,297 76,754 Tanker Trucks 3,000 4,888 5,213 9,181 Railroads 2,000 2,322 2,164 1,431 Tank Ships 192,492 60,250 42,197 3,598 Tank Barges 31,830 52,989 22,882 5,429 STORAGE AND CONSUMPTION 1,195 1,195 1,564 814

Gas Stations 1,195 1,195 1,564 814 TOTAL Petroleum Industry Spillage 524,292 315,053 222,515 119,281

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Clean up of inland spill sites is a long term process running into several years. It involves

a lot of expertise and a series of steps including detailed site characterization and

implementation of technologies in a sequential manner. It also requires a large and

continuous funding source and often supplemented by government funding sources. In

U.S.A superfund was created o support cleanups. Superfund Remediation Report

(2014).4th Edition focuses on the analysis of Superfund remedial actions from fiscal

years (FY) 2009 to 2011. The report includes remedies selected in 459 decision

documents signed in this three-year period. Air sparging coupled with Soil vapor

extraction, chemical treatment, multi-phase extraction, bioremediation and permeable

reactive barrier wall are the most frequently selected in situ treatment technologies for

sources as reported in the Superfund remedial report.

Figure 22: Popular Remediation Technologies in Superfund Sites of U.S.A

The choice of technology or a set of technologies has to be decided based on the site

conditions and nature of spill by experienced environmental engineers and

hydrogeologists. Monitoring of cleaned up sites for a much longer duration is also

essential to ensure that there is no rebound of contamination.

IITMadras Page 50

References

Banerjee, S., 1984.Solubility of organic mixtures in water,Environ. Sci. Technol., 18(8): 587-591. Borden, R.C., and C.M. Kao, 1992.Evaluation of groundwater extraction for remediation of petroleum-contaminated aquifers, Water Environ. Res., 64(1): 28-36. DiGiulio, D.C., and J.S. Cho, 1990. Conducting field tests forevaluation of soil vacuum extraction application, in Proc.Fourth Natl. Outdoor Action Conf. on Aquifer Restoration, Ground Water Monitoring, and Geophysical Methods, Natl.Ground Water Assoc., Dublin, OH, 587-601. Feenstra, S., D.M. Mackay, and J.A. Cherry, 1991. A methodfor assessing residual NAPL based on organic chemicalconcentrations in soil samples, Ground Water Monit. Rev.,11(2): 128-136. Geller, J.T., and J.R. Hunt, 1993.Mass transfer fromnonaqueous phase organic liquids in water-saturated porousmedia, Water Resour. Res., 29(4): 833-845. Huling, S.G., and J.W. Weaver, 1991.Dense nonaqueousphase liquids, Ground Water Issue, EPA/540/4-91-002,U.S.EPA, R.S. Kerr Environ. Res. Lab., Ada, OK, 21 pp.Johnson, P.C., C.C. Stanley, M.W. Kemblowski, D.L. Byers,and J.D. Colthart, 1990b.A practical approach to the design,operation, and monitoring of in situ soil-venting systems,Ground Water Monit. Rev., 10(2): 159-178. Leinonen, P.J., and D. Mackay, 1973. The multicomponentsolubility of hydrocarbons in water, Can. J. Chem. Eng., 51:230-233. Mercer, J.W., and R.M. Cohen, 1990. A review of immisciblefluids in the subsurface: Properties, models, characterization,and remediation, J. Contam. Hydrol., 6: 107-163. Miller, C.T., M.M. Poirier-McNeill, and A.S. Mayer, 1990.Dissolution of trapped nonaqueous phase liquids: Masstransfer characteristics, Water Resour. Res., 26(11): 2783-2796. Norris, R.D., R.E. Hinchee, R. Brown, P.L. McCarty, L.Semprini, J.T. Wilson, D.H. Kampbell, M. Reinhard, E.J.Bouwer, R.C. Borden, T.M. Vogel, J.M. Thomas, and C.H.Ward, 1994. Handbook of Bioremediation, Lewis Publishers,Boca Raton, FL, 257 pp. de Pastrovich, T.L.,Y. Baradat, R. Barthel, A.Chiaarelli, and D.R. Fussell. 1979. Protection of groundwater from oil pollution. CONCAWE, Report 3/79. Den Hagg, Netherlands. 61pp. Piwoni, M.D., and J.W. Keeley, 1990.Basic concepts ofcontaminant sorption at hazardous waste sites, Ground WaterIssue, EPA/540/4-90/053, U.S.EPA, R.S. Kerr Environ. Res.Lab., Ada, OK, 7 pp.

IITMadras Page 51

Powers, S.E., C.O. Loureiro, L.M. Abriola, and W.J. Weber,Jr., 1991.Theoretical study of the significance ofnonequilibrium dissolution of nonaqueous phase liquids insubsurface systems, Water Resour. Res., 27(4): 463-477. Rao, P.S.C., L.S. Lee, and A.L. Wood, 1991.Solubility,sorption, and transport of hydrophobic organic chemicals incomplex mixtures, Environmental Research Brief, EPA/600/M-91/009, U.S.EPA, R.S. Kerr Environ. Res. Lab., Ada, OK,14 pp Suthersan, Suthan. S 1997. Remediation Engineering: Design Concepts. Lewis Publishers. U.S.EPA, 1990. Subsurface contamination reference guide,EPA/540/2-90/011, U.S.EPA, Washington, DC, 13 pp. U.S.EPA, 1992a.Dense nonaqueous phase liquids –Aworkshop summary, Dallas, Texas, April 16-18, 1991, EPA/600/R-92/030, U.S.EPA, R.S. Kerr Environ. Res. Lab., Ada,OK, 81 pp.

IITMadras Page 52

6. Appendix I

Plate 1 : Well Gauging at Tondiarpet Contaminated Area

Plate 2: Assessment using Interface Meter at Tondiarpet Contaminated Area

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Plate 3:Trial Pit

Plate 4: Hand Auger Drilling at Tondiarpet Exploratory Bore hole

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Plate 5: Groundwater sampling atTondiarpet Contaminated Area

Plate 6: Soil Sampling at Tondiarpet Contaminated Area

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Plate 7: Soil and Gas Monitoring at Tondiarpet Contaminated Area

Plate 8: Drilling of Exploratory Borewell # 18 Right beneath the BPCL pileline

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Plate 9: Contaminated Soil Observed at a Shallow Depth of6 ft. in Exploratory Borewell # 18

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Appendix – II

Table AI1 1: Coordinates of Exploratory Borehole Locations

S.NO. BOREHOLE ID EASTING NORTHING

1 EBW 2 422967 1451047

2 EBW 3 422953 1451050

3 EBW 4 422928 1451016

4 EBW 5 422970 1451010

5 EBW 6 423008 1451096

6 EBW 7 423065 1451096

7 EBW 8 422838 1451028 8 EBW 9 422944 1451037 9 EBW 10 422967 1451117

10 EBW 11 423112 1450993 11 EBW 12

422979 1451120 12 EBW 13 422955 1451120 13 EBW 14

423007 1451092 14 EBW 15 422927 1451080 15 EBW 16 423024 1451074 16 EBW 17 422960 1451097 17 EBW 18 422960 1451097 18 EBW 19 422941 1450948 19 EBW 20 423002 1451090 20 EBW 21 423021 1451082

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Table AII 2: Well Inventory of Borewells with Free Phase Hydrocarbon: Measured with Interphase probe in October 2013.

S. No Location Easting Northing Depth to

product (ft)

Depth to Water (ft)

Product Thickness (ft)

1 Door No 231, TH Road

422987 1451045 28.56 28.9 0.34

2 Door No 225, TH Road

422980 1451070 27.56 29.23 1.67

3 Door No223 TH Road 422975 1451071 26.60 26.65 0.05 4 Door No 227 TH

Road 422967 1451072 32.56 32.59 0.03

5 Door No 222 TH Road

422963 1451073 26.9 28.9 2

6 Door No 228 TH Road

422954 1451079 27.0 27.2 0.2

7 Door No 221 TH Road

422948 1451079 26.69 26.79 0.1

8 5/20 VP Koil street 422990 1451109 25.15 27.90 2.75 9 3/1/19 Karpagam

Illam, VP koil street 422971 1451126 28.9 20 1.1

10 15/6 VP koil street 422998 1451091 31.4 31.5 0.1 ND: Not detected

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Table AII 3: Locations of water samples taken by IITM

Well # Easting Northing Address / Location Landmark 1 423058 1451107 Arun Hospital , Pillaiyar Koil Street.

2 423082 1451176

Lakshmi Nilayam , Old No.- 11/12 , New No. 36/1, Pillaiyar Koil

Street.

3 423006 1451090 Door No. 5/20 , V.P Koil Street, Next to Dr. Suhas Prabhakar House

4 423069 1451176 No. 671/206 , T.H Road / Loganathan Thirumana Mandapam

5 423069 1451312 No. 200, T.H Road / Madhav Pipes & Tubes

6 422919 1451070 N.Gajendran, 614/2 , New No.- 570 , T.H Road / Opp. Devi Polymer

7 422912 1450972 S.V .Complex, No. 233/1A ,T.H Road

8 423040 1451053 6/32 , Kanakar Street

9 423054 1450990 Old No. 6/2, New No. 25, Kanakar Street

10 422996 1450984 Door No. 24/3 , Old No. 31/7, Kanakar Street / Ganesh Colony

11 423055 1450950 Door No. 17, Kanakar Street / Near To Ganesh Colony

12 423024 1451074 Door No. 221, TH Road / Inside Narrow lane

13 422955 1451120 New Construction Building / next to Orthocare

14 423008 1451096 Inside Agastya Theater

15 422967 1451117 Orthocare / Parallel to TH Road , Opposite to Microfinance Building

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Table AII 4 Locations of Water samples taken by BPCL

Well # Address of the Location

1 Door No 221, TH Road

2 Door No 222, TH Road

3 Door No 223, TH Road

4 Door No 225, TH Road

5 Door No 227, TH Road

6 Door No 228, TH Road

7 Door No 229, TH Road

8 Door No 231, TH Road

9 Door No 681, TH Road

10 Door no 12/16, VP Koil Street

11 Door no 12/16A, VP Koil Street

12 Door no 13/1, VP Koil Street

13 Door no 13/2, VP Koil Street

14 Door no 15/6, VP Koil Street

15 Door no 3-2/19, VP Koil Street

16 Door no 5/20, VP Koil Street

17 Door no 667, VP Koil Street

18 Door no 671, VP Koil Street

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Appendix III TableAIII 1: Concentration of Dissolved Hydrocarbons in the Wells Sampled by IIT

Well no/Compound Units 1 2 3 4 5 6 7 Alkyl Benzene Benzene Ug/L BDL BDL 34588.34 25.1 7.49 2.72 2.28 Toluene Ug/L BDL 1.35 96257.22 50.48 27.26 9.88 8.51 Ethyl Benzene Ug/L BDL BDL 6967.29 4.87 3.19 1.17 1.02 m and p-Xylene Ug/L BDL 0.38 23951 18.65 11.08 3.88 3.12 O-Xylene Ug/L BDL 0.43 BDL 13.94 8.01 2.67 2.38 Isopropyl benzene Ug/L BDL BDL 430 BDL BDL BDL BDL 1,3,5,-Trimethyl benzene Ug/L BDL BDL 2613.54 1.59 0.99 0.24 0.25 1,2,4, Trimethyl benzene Ug/L BDL BDL 11716.21 10.34 6.34 2.12 1.57 sec-butyl benzene Ug/L BDL BDL 124.27 BDL BDL BDL BDL Straight Chain Alkanes Decane Ug/L 0.66 0.66 186.97 0.63 0.53 0.55 0.52 Undecane Ug/L 30.66 30.58 9262.88 29.24 24.97 26.26 25.45 Dodecane Ug/L 0.65 0.8 2620.16 BDL 0.69 0.54 BDL Tridecane Ug/L 9.1 BDL 3038 BDL BDL BDL BDL Tetradecane Ug/L 1.78 1.99 5728.98 1.7 1.73 1.54 BDL Pentadecane Ug/L BDL BDL 7765.32 BDL BDL BDL BDL Hexadecane Ug/L 5.87 5.88 9644.93 6.36 5.17 5.66 BDL Heptadecane Ug/L BDL BDL 14255.53 BDL BDL 37.84 34.36 Octadecane Ug/L 4.86 5 9340.54 5.46 4.26 4.28 5.75 Nonadecane Ug/L 12.88 11.09 14762.63 16.55 9.98 11.31 11.41 Eicosane Ug/L 8.01 6.76 6536.68 8.52 5.76 8.07 7.46 Poly Aromatic HC's Naphthalene Ug/L BDL BDL 918.05 13.31 6.72 2.45 2.02 Chlorinated Alkenes

Cis-1,2 dichloro ethene Ug/L 37.15 BDL BDL 13.2 BDL BDL BDL trans-1,2, dichloro ethene Ug/L BDL BDL BDL 1.47 BDL BDL BDL Trichloro ethylene Ug/L 1.06 BDL BDL 1.33 BDL BDL BDL Tetrachloro ethylene Ug/L 7.2 BDL BDL 4.77 0.98 BDL BDL Methylene Chloride Ug/L BDL 0.33 BDL BDL BDL BDL 0.21 Other compounds Styrene Ug/L BDL BDL 23357.6 BDL BDL BDL BDL Chloroform Ug/L BDL BDL BDL 0.7 1.15 0.76 BDL 1,2- dichloro propane Ug/L BDL BDL BDL BDL BDL 0.56 BDL 1,4-dichloro benzene Ug/L BDL BDL BDL BDL BDL BDL BDL

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Table AIII 1 (contd): Concentration of Hydrocarbons in the Wells Sampled by IIT Well no/Compound Units 8 9 10 11 12 13 14 15 Alkyl Benzene Benzene Ug/L 21.39 1.22 1.89 1.06 1644.32 BDL BDL 4814.28 Toluene Ug/L 6.52 4.23 6.1 3.81 5780.92 BDL BDL 32305.04 Ethyl Benzene Ug/L 0.74 0.52 0.72 BDL BDL BDL BDL 3544.06 m and p-Xylene Ug/L 3.96 1.52 2.12 1.25 BDL BDL BDL 9810.02 O-Xylene Ug/L 1.93 0.95 1.71 1.12 2754.58 BDL BDL 14196.88 Isopropyl benzene Ug/L BDL BDL BDL BDL BDL BDL BDL BDL 1,3,5,-Trimethyl benzene Ug/L 4.2 0.19 BDL BDL BDL BDL BDL 1003.62 1,2,4, Trimethyl benzene Ug/L 2.2 1.2 1.44 BDL BDL BDL BDL 4633.68 sec-butyl benzene Ug/L BDL BDL BDL BDL BDL BDL BDL BDL Straight Chain Alkanes Decane Ug/L 0.63 0.49 0.49 0.59 BDL BDL 0.37 BDL Undecane Ug/L 29.52 23.36 23.68 27.56 12495.85 4.83 2.86 13.61 Dodecane Ug/L 0.65 0.52 0.49 0.4 21575.9 0.38 0.36 7.06 Tridecane Ug/L BDL BDL BDL 11.5 35844.09 BDL BDL 6.39 Tetradecane Ug/L BDL 1.29 1.43 BDL 33731.79 0.96 BDL 17.45 Pentadecane Ug/L BDL BDL BDL BDL 49871.02 BDL BDL 24.84 Hexadecane Ug/L 6.55 5.04 5.35 6.4 53001.45 1.52 2.66 48.77 Heptadecane Ug/L 39.99 30.23 32.95 42.73 73618.65 BDL 6.75 BDL Octadecane Ug/L 6.98 4.57 4.05 6.85 45031.31 1.87 5.64 BDL Nonadecane Ug/L 13.06 9.95 11 12.51 74045.06 5.81 9.58 93.74 Eicosane Ug/L 8.77 6.41 6.33 9.63 28635.35 3.64 6 56.5 Poly Aromatic HC's Naphthalene Ug/L 1.61 1.65 1.26 BDL BDL BDL BDL BDL Chlorinated Alkenes

Cis-1,2 dichloro ethene Ug/L BDL BDL BDL BDL BDL BDL BDL BDL trans-1,2, dichloro ethene Ug/L BDL BDL BDL BDL BDL BDL BDL BDL Trichloro ethylene Ug/L BDL BDL BDL BDL BDL BDL BDL BDL Tetrachloro ethylene Ug/L BDL BDL BDL BDL BDL BDL BDL BDL Methylene Chloride Ug/L BDL 3.47 0.86 0.86 10750 6307.24 1370.84 6184.26 Other compounds Styrene Ug/L BDL BDL BDL BDL BDL BDL BDL 455.8 Chloroform Ug/L 3.22 BDL 2.11 2.63 BDL BDL BDL BDL 1,2- dichloro propane Ug/L BDL BDL BDL BDL BDL BDL BDL BDL 1,4-dichloro benzene Ug/L 0.14 0.69 BDL BDL BDL BDL BDL BDL

BDL: Below Detectable Level.

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TableAIII 2: Concentration of Dissolved Hydrocarbons in the Wells Sampled by BPCL

Well no/Compound Units 1 2 3 4 5 6 Alkyl Benzene Benzene Ug/L 5064.54 2720.18 3946.54 2162.9 2619.56 8332.54 Toluene Ug/L 13012.66 15460.22 53626.16 28912.34 12153.52 58901.4 Ethyl Benzene Ug/L 585.66 2506.9 7586.06 5253.74 4439.32 10849.76 m and p-Xylene Ug/L 3307.56 12026.24 17417.58 10653.68 11207.52 23752.34 O-Xylene Ug/L 3490.74 11446.6 17086.48 10396.54 11573.02 20440.48 Straight Chain Alkanes Octane Ug/L 3840.78 4288.66 1457.63 8582.41 7711.34 8344.72 Nonane Ug/L BDL BDL 285.84 152.35 BDL 418.07 Decane Ug/L 157.26 199.98 1585.29 863.2 319.65 1902.18 Undecane Ug/L 465.5 395.98 1750.26 1618.46 678.82 3379.62 Dodecane Ug/L 978.79 785.96 3424.52 1945.36 1259.93 4471.35 Tridecane Ug/L 1446.09 292.98 524.74 928.67 409.56 1424.73 Tetradecane Ug/L 1318.95 950.26 6306.65 4123.85 3946.39 17691.81 Pentadecane Ug/L 1852.1 1641.48 1905.06 3978.37 2136.66 11318.27 Hexadecane Ug/L 1824.94 1688.92 3583.89 4655.78 2267.41 10240.17 Heptadecane Ug/L 1852.89 1608.79 3382.82 4765.09 2436.45 9753.62 Octadecane Ug/L 1577.34 1591.24 3203.82 3850.51 1807.1 7583.13 Nonadecane Ug/L 2472.11 2253.53 5464.11 6093.37 2891.44 11182.69 Eicosane Ug/L 1328.56 1192.78 2402.52 3188.97 1534.89 5807.93 Poly Aromatic HC's Naphthalene Ug/L 131.58 967.5 1831.8 1486.08 1684.74 1829.22 phenanthrene Ug/L BDL BDL BDL BDL BDL BDL pyrene Ug/L BDL BDL BDL BDL BDL Benzo (a) Pyrene Ug/L BDL 0.5 BDL 0.32 0.26 0.43 Indeno(1,2,3-cd) Pyrene Ug/L BDL 0.18 BDL BDL BDL 0.12 Benzo(ghi)perylene Ug/L 0.12 0.23 BDL 0.16 0.1 0.17

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TableAIII 2 (cont): Concentration of Dissolved Hydrocarbons in the Wells Sampled by BPCL

Well no/Compound Units 7 8 9 10 11 12 13 Alkyl Benzene Benzene Ug/L 3582.76 2405.42 BDL BDL 10970.16 8071.1 16688.3 Toluene Ug/L 4865.02 13493.4 59.34 10.32 18702.42 34894.5 84345.36 Ethyl Benzene Ug/L 153.08 868.6 8.6 1.72 1308.06 4277.64 16082 m and p-Xylene Ug/L 2052.82 12137.18 116.96 34.4 1911.78 14008.54 36132.9 O-Xylene Ug/L 2481.1 13118.44 99.76 24.08 2593.76 12945.58 30958.28 Straight Chain Alkanes Octane Ug/L 2250.63 2364.78 2677.71 1469.3 2633.71 4393.95 3407.26 Nonane Ug/L BDL 569.98 BDL BDL BDL 451.13 1268.39 Decane Ug/L 148.96 113.16 70.45 0.81 88.89 1608.61 1934.02 Undecane Ug/L 296.24 1711.14 1375.82 1374.36 1580.57 3033.34 2430.51 Dodecane Ug/L 796.5 2054.94 83.25 98.48 111.29 3905.96 2702.15 Tridecane Ug/L 2.96 723.88 211.21 144.86 262.37 1265.01 892.95 Tetradecane Ug/L 1482.52 3841.46 98.53 113.27 125.79 12265.47 8054.52 Pentadecane Ug/L 1404.87 3684.83 707.2 792.82 1153.09 6862.98 4180.48 Hexadecane Ug/L 1829.65 3588.83 149.22 215.1 296.51 6479.64 3838.9 Heptadecane Ug/L 1826.44 3643.43 147.75 220.64 275.97 6708.01 3714.35 Octadecane Ug/L 1359.02 3295.58 120.95 17.7 265.15 5253.24 2876.23 Nonadecane Ug/L 2318.44 5120.25 215.77 354.42 354.72 7866.7 4987.22 Eicosane Ug/L 1189.01 2657.73 108.92 175.57 223.28 4055.75 2577.87 Poly Aromatic HC's Naphthalene Ug/L 371.52 1543.7 200.38 54.18 67.94 781.74 2016.7 phenanthrene Ug/L BDL BDL 2.55 0.52 0.16 BDL BDL pyrene Ug/L BDL BDL 0.93 0.15 BDL BDL BDL Benzo (a) Pyrene Ug/L 0.39 BDL BDL BDL BDL 0.4 0.28 Indeno(1,2,3-cd) Pyrene Ug/L 0.1 BDL BDL BDL BDL 0.1 0.25 Benzo(ghi)perylene Ug/L 0.16 0.1 BDL BDL BDL 0.2 0.4

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TableAIII 2 ( cont): Concentration of Dissolved Hydrocarbons in the Wells Sampled

by BPCL

Well no/Compound Units 14 15 16 17 18 Alkyl Benzene Benzene Ug/L 3787.44 15322.62 14970.02 88.58 3.44 Toluene Ug/L 18017 49017.42 124993.26 743.9 149.64 Ethyl Benzene Ug/L 1837.82 2982.48 41372.02 183.18 46.44 m and p-Xylene Ug/L 12311.76 8395.32 67933.12 496.22 121.26 O-Xylene Ug/L 11524.86 8016.06 78264.3 370.66 64.6 Straight Chain Alkanes Octane Ug/L 4066.93 4660.34 3535.76 4068.81 6629.15 Nonane Ug/L 568.78 633.07 375.98 BDL BDL Decane Ug/L 1128.07 1794.63 666.62 81.58 66.12 Undecane Ug/L 1580.93 3387.96 735.7 20.88 3891.63 Dodecane Ug/L 2043.32 4171.72 983.31 112.01 93.88 Tridecane Ug/L 735.36 1272.83 329.54 251.29 1094.71 Tetradecane Ug/L 5357.07 11206.5 1419.54 187.46 146.77 Pentadecane Ug/L 3009.38 6753.25 1060.55 1017.61 1858.71 Hexadecane Ug/L 585.37 6761.6 1537.34 318.94 405.78 Heptadecane Ug/L 3262.78 7068.14 1664.47 345.17 433.71 Octadecane Ug/L 2354.95 5416.03 1530.34 259.21 302.7 Nonadecane Ug/L 3986.23 8227.51 2154.03 504.82 478.82 Eicosane Ug/L 1978.16 4304.06 1108.71 254.03 275.18 Poly Aromatic HC's Naphthalene Ug/L 1000.18 612.32 5892.72 408.5 98.9 phenanthrene Ug/L BDL BDL BDL 2.94 0.67 pyrene Ug/L BDL BDL BDL 1.36 0.34 Benzo (a) Pyrene Ug/L 0.15 BDL BDL BDL BDL Indeno(1,2,3-cd) Pyrene Ug/L 0.07 BDL BDL BDL BDL Benzo(ghi)perylene Ug/L 0.14 BDL 0.08 BDL BDL