new horizon surveys (i ) pvt. ltd. and... · report dear sir, refer to ... conducting standard...

CIN: U74 900 MH 2008 PTC 185208

Ref.: NHS/MMB/046/2017-18Date: 01st January. 2018

To,Chief Executive OfficerMaharashtra Maritime BoardIndian MercantileChambers, BallardEstate, Mumbai

Kind Attn.:- Mr. Abhyankar

SUB: FORWARDING OF GEOTECHNICAL & BATHYMETRIC SURVEYREPORT

Dear Sir,

Refer to your Work Order No. MMB/MMB/SURVEYOR/SE/GEO-PHYSICAL ATMANDWA/901 dated 11/10/2017.

Please find enclosed herewith Survey Report is as follows:-

01. Survey Report 01 soft Copies,02. Survey Report 01 hard copies.

Kindly acknowledge the receipt of the same.

Thanking You,

Yours Faithfully,For New Horizon Surveys (I) Pvt. Ltd.

(Nandkumar Y.Vhanmane)Managing Director+91 9930 416 996Encl: As Above

New Horizon Surveys (I) Pvt. Ltd.E-24/10, Suryoday, Sector – 48,Nerul,, Navi Mumbai – 400 706Tel : + 91 22 32662704,Fax : + 91 22 27716265Email : newhorizon703@gmail

[email protected]

MAHARASHTRA MARITIME BOARDHOME DEPARTMENT (PORTS AND TRANSPORT)

GOVERNMENT OF MAHARASHTRA

GEOTECHNICAL INVESTIGATION REPORT

FOR PROPOSED DREDGING

AT MANDWA, TAL: ALIBAGH; DIST: RAIGAD

BY

M/S NEW HORIZON SURVEYS INDIA PVT. LTD.E-24/10 Suryaoday Sector 48 Nerul,

Navi Mumbai - 400 706Email: [email protected],

DECEMBER – 2017

1




CONTENTS

1.0 GENERAL

2.0 SCOPE OF INVESTIGATION

3.0 METHODOLOGY

4.0 FINDINGS OF INVESTIGATION

5.0 GEOTECHNICAL ASSESSMENT

ANNEXURES

A) LOCATION PLAN

B) BORE HOLE LOGS

C) LABORATORY TEST RESULTS

2




1. GENERAL

1.1. The Marine Engineer & Chief Surveyor - Maharashtra Maritime Board has proposed

to RO-RO Jetty at Mandwa, Taluka Alibagh, District Raigad.

1.2. It was decided to carry out Geophysical and geotechnical investigation to determine

subsurface ground condition. Ms. New Horizon Surveys (India) Pvt. Ltd. has been

appointed to conduct geophysical survey and geotechnical investigations.. M/s NHS

executed the field work between last week of October November -2017.

2.0 SCOPE OF INVESTIGATION

2.1 Scope of geotechnical investigation work consists of six bore holes estimated up to

(–) 4.0 m below CD level. Objective of investigation was to find out the subsoil

stratification in the project area and to collect data of subsoil stratifications for

Dredging purpose.

.

2.2 Scope of work also included the following:

I) Conducting standard penetration tests in-situ to obtain the shear strength

parameters of the soil at an interval of 1.5 metre and collect disturbed soil

samples in the SPT split spoon.

II) Collect and transport the selected samples in soil and rock testing laboratory and

prepare a geotechnical investigation report based on the data collected from field

and the results of the laboratory tests on the selected soil, water and rock

samples.

3

2.3 Fieldwork is summarised in the following table no. 1.

TABLE 1: SUMMARY OF BORE HOLE

Bore Hole NoR. L.

w.r.t. CD(m)

Rock Level(m)

Final Depth(m)

MBH-1 (-) 0.7 Not Encountered 4.08

MBH-2 (-) 0.8 0.3 4.3

MBH-3 (-) 1.9 0.6 3.1




3.0 METHODOLOGY

A brief methodology of geotechnical investigation is as follows:

3.1 Geotechnical investigation was planned to obtain the subsoil stratification in the

proposed project area and to collect soil and rock samples for laboratory testing to

determine the engineering properties such as shear strength, compressibility, along

with basic engineering classification of the subsurface stratum.

3.2 Location of the bore holes were selected in consultation with client. Data and results

obtained from this investigation will be used in Dredging of the proposed Area.

3.3 For geotechnical investigation work, standard rotary type drilling rig was used over a

pontoon. This rig is coupled with diesel engine and has tripod and all drilling

accessories. Drilling rig deployed is suitable for and has arrangement for driving as

well as extracting casing, boring drilling by mud circulation method, conducting

Standard Penetration Test (SPT) collection of Undisturbed Soil Sample (UDS) and

Disturbed or wash Soil Sample (DS).

4

3.4 Drilling rig with pontoon was shifted at the specified borehole locations. Pontoon was

stabilised by four mooring anchors. Initially casing of adequate diameter to suit boring

of 100 mm hole was lowered and boring was commenced.

3.5 Sampling in the bore hole was carried out generally as per the guidelines given in the

IS code. SPTs were conducted at regular intervals.

3.6 Generally Standard Penetration Tests (SPT) are conducted in bore holes to obtain

the ‘N’ values i.e. no. of blows of 63.5 kg hammer falling through 75 cm, required to

penetrate 30 cm of SPT split spoon. This test is conducted as per IS-2131. The ‘N’

values are correlated with the relative density of non-cohesive soils and consistency

of saturated cohesive soils. The test also collects samples in the split spoon

assembly, which are treated as disturbed samples. SPTs are taken @ 1.50 m

interval.

3.7 When the rock was encountered, size of bore hole was changed to Nx. i.e.75mm

diameter. A core barrel and Nx sized diamond bit fitted to double tube core barrel

was used for drilling and recovering rock cores. The recovered rock cores were

numbered serially and preserved in wooden core boxes. The core recovery and Rock

Quality Designation (RQD) were computed for every run length drilled. Four Rock

samples were selected for laboratory testing.

3.8 The bore holes are terminated as depths ranging between 3.6m and 4m below bed

level. On completion of bore hole selected rock samples were taken to the laboratory

for testing.

3.9 The field work was executed generally in accordance with the I. S. specifications

listed below:

a) IS-1892: Code of practice for subsurface investigation of foundations.

b) IS-1498: Classification and identification of soils for general engineering purposes.

c) IS-2131: Method for standard penetration test for soils.

d) IS-6926: Code of practice for diamond core drilling for site investigations.

e) IS-5313: Guide for core drilling observations.

3.10 Laboratory testing was done following the testing procedures given in relevant parts

of IS-2720. All the data is given in the Enclosures.

5

4.0 FINDINGS OF INVESTIGATION

Log of six bore holes drilled for the proposed dredge area was studied together with

laboratory tests. Following stratifications were seen from ground level to the depth of

termination of investigation.

Stratum One : Greyish Medium Dense to Dense Silty Fine SandStratum Two : Greyish Black Slightly Weathered Fractured Basalt

4.1 STRATUM ONE : GREYISH MEDIUM DENSE TO DENSE SILTY FINESAND

First stratum of generalised subsurface profile encountered below the existing bed

level was Greyish Medium Dense to Dense Silty Fine Sand with fragments ofshells.. This Stratum was observed in all the bore holes. Thickness of this stratum was

observed between 0.3m in MBH-2 and 3.6m in MBH-4, MBH-5 and MBH-6. In MBH-4,

MBH-5 and MBH-6 this stratum was observed below the existing bed level and

continued till the termination depth of bore hole i.e. 3.6m.

Ten SPT’s were conducted in this stratum. SPT ‘N’ values were observed in the

between 15 and 30 with a sole refusal observed in MBH-1. The possible reason for

this refusal could be presence of gravel which may prevented penetration of SPT

spoon sampler SPT ‘N’ values indicate medium dense to dense relative density of

cohesionless stratum. The soil encountered is basically silty fine sand with fragments

of shells. This stratum has medium shear strength to support the foundation load and

high potential to consolidate under sustained loadings.

In MBH-1, Greyish Sandy Gravel was observed between depths 1.7m to 4.1m. Two

SPT were conducted with both reporting as refusals.

4.2 STRATUM TWO : GREYISH BLACK SLIGHTLY WEATHEREDFRACTURED BASALT

Next and the last stratum encountered was Greyish Black Slightly WeatheredFractured Basalt. This stratum was observed in MBH-2 and MBH-3 only. The bore

holes were terminated in this stratum after penetrating 4m in MBH-2 and 2.5m in MBH-

3 as indicated in Table: 1.

6

Cores recovery in this stratum was observed between 70% and 93% with an

exceptionally low value of 50% observed in MBH-3. RQD was observed between nil

and 61. Range of CR and RQD indicates slightly weathered rock with very poor to fair

state of fractures in the rock mass.

Two rock samples recovered from this stratum were tested for unconfined

compression strength, which were observed as 543.11Kg/cm2 and 650.27Kg/cm2,

indicating medium to high strength quality of rock.

5.0 GEOTECHNICAL ASSESSMENT

5.1 Six bore holes were drilled to investigate the area under dredging. The data from the

bore holes and laboratory tests were studied together to understand characteristics

of subsurface stratifications..

5.2 The generalised subsurface profile consists of 0.3m to 3.6m thick Greyish Medium

Dense to Dense Silty Fine Sand with fragments of shells. This stratum has medium

shear strength to support the foundation load and high potential to consolidate under

sustained loadings. In MBH-1 Greyish hard silty clay with gravel was observed below

this stratum between depths 1.7m to 4.1m.

5.2 Greyish Black Slightly Weathered Fractured Basalt were encountered in MBH-2 and

MBH-3 below the silty fine sand stratum and continued till the termination depth of

bore hole. Based on unconfined compression strength, core recover and rock quality

designation observed, this stratum has medium to high shear strength.

5.3 The stratum encountered in BH-1, BH-4 to BH-5 are easy to dredge. The observed

SPT ‘N’ values, indicates medium to high shear strength and it will stable for a slope

of 1V : 1.5H after dredging. Where as in BH-2 and BH-3 slightly weathered basalt is

encountered upto termination depth of bore holes. Dredging in this rock require

controlled blasting.

For NEW HORIZON SURVEYS INDIA PVT. LTD.

ANNEXURES

BORE HOLE LOCATION PLAN

BORE HOLE LOGS

CH/Co - Ordinates : 276676.508 N, 2080968.802E Bore Hole No. : BH1

Depth of GWT : MARINE BORE HOLE Depth of Casing : 3

Methodology ROTARY DRILLING Date Commenced : 29/10/2017

Date Completed : 30/10/2017

RL Dia of CR RQ

m Hole Depth Type No 15 30 45 60 N % %

BOULDER (GREYISH BLACK BADALT) 0.4

1.0m 100 GREY FINE SAND 0.9 0.4/0.9 DS 1 5

BOULDER (GREYISH BLACK BADALT) 1.2 1.5/1.7 SPT 1 28 48 R

2.0m GREYISH YELLOW SILTY CLAY

WITH GRAVELLS AND PEBBLES 10 2

3.0m 3/3.12 SPT 2 40 50 R

5 3

4.0m 4.08 4.0/4.08 SPT 3 30 48 R

5.0m

6.0m

7.0m

8.0m

9.0m

10m

11m

BORE HOLE BH1 TERMINATED AT 4.08 MBBL

12m

13m

14m

15m

16m

17

D : Disturbed Sample

UDS : Undisturbed Sample Rock Quality Designation B

SPT : Standard Penetration Test Vane Shear Test P PENETRARTION IN MM

WS : Wash Sample Packer Permeability Test

PENETRATION

BLOWS

PENETRATION

BLOWS

PENETRATION

BLOWS

: BLOWS

NEW HORIZON SURVEYS (I) PVT. LTD

Job No. :

Page No. : 1

Project : GEOTECHNICAL INVESTIGATION WORK AT MANDWA

Client : MAHARASHTRA MARITIME BOARD

dept

h

Log Description

Sample SPT 'N' Value Remarks / OtherTests

Site Engg. Drawn. By Chkd. By Client Rept.

RL . : (-)0.70 Depth of Bore Hole : 4.08

CH/Co - Ordinates : 276690.306 N, 2081017.351 E Bore Hole No. : BH2

Depth of GWT : MARINE BORE HOLE Depth of Casing : 0.7



RL Dia of CR RQ


100 GREYISH SILTY CLAYEY SAND 0.3 0/0.3 DS 1

1.0m

Nx ROCK

2.0m 1.8

GREYISH BLACK FRACTURED

3.0m BASALT

3.3

4.0m

4.3

5.0m

6.0m

7.0m

8.0m

9.0m

10m

11m


12m

13m

14m

15m

16m

17





93 52

: BLOWS


70 49

92 61



dept

h

Log Description


Job No. :

Page No. : 1




Depth of GWT : MARINE BORE HOLE Depth of Casing : 0.9



RL Dia of CR RQ


100 GREYISH SILTY CLAYEY SAND 0.6 0.0/0.6 DS 1

1.0m

Nx GREYISH BLACK FRACTURED 1.6 ROCK

2.0m BASALT

2.6

3.0m 3.1 78 NIL

4.0m

5.0m

6.0m

7.0m

8.0m

9.0m

10m

11m


12m

13m

14m

15m

16m

17





: BLOWS


50 NIL

75 NIL



dept

h

Log Description


Job No. :

Page No. : 1



CH/Co - Ordinates : 276999.709 N, 2081219.330E Bore Hole No. : BH4




RL Dia of CR RQ


0.0/1.0 DS 1

1.0m 100 1.0/1.6 SPT 1 4 5 10 15 15

GREY SILTY FINE SAND WITH

2.0m FRAGMENT OF SHELL 2.0/2.6 SPT 2 5 9 15 19 24

3.0m 3.0/3.6 SPT 3 4 8 18 19 26

3.6

4.0m

5.0m

6.0m

7.0m

8.0m

9.0m

10m

11m


12m

13m

14m

15m

16m

17





: BLOWS




dept

h

Log Description


Job No. :

Page No. : 1


RL . : (-) 2.3 Depth of Bore Hole : 3.6





RL Dia of CR RQ


0.0/1.0 DS 1

1.0m 100 1.0/1.6 SPT 1 5 6 10 14 16



3.0m 3.0/3.6 SPT 3 6 10 16 18 26

3.6

4.0m

5.0m

6.0m

7.0m

8.0m

9.0m

10m

11m


12m

13m

14m

15m

16m

17





: BLOWS




dept

h

Log Description


Job No. :

Page No. : 1







RL Dia of CR RQ


0.0/1.0 DS 1

1.0m 100 1.0/1.6 SPT 1 5 6 15 24 23



3.0m 3.0/3.6 SPT 3 7 10 20 28 30

3.6

4.0m

5.0m

6.0m

7.0m

8.0m

9.0m

10m

11m


12m

13m

14m

15m

16m

17





: BLOWS




dept

h

Log Description


Job No. :

Page No. : 1



LABORATORY TEST RESULTS

Draft Report on

Geophysical Survey followed by Geotechnical Investigations at Mandwa, Dist Alibaug

Maharashtra Maritime Board

Indian Mercantile Chambers, Ballard Estate,Mumbai

Survey Contractor:

New Horizon Surveys (I) Pvt. Ltd.

E-24/10, Suryoday, Sector - 48, Nerul,Navi Mumbai - 400 706Tel.: +91 22 32662704/+91 9324112703/+91 9930416696Fax.: +91 22 27716265

Email: [email protected],[email protected]

Volume: 01 of 01

Survey Period: 13th Oct 2017 to 15th Oct 2017 and 19th Oct 2017

00 Draft Report 10th Jan 2018 MK NYV

Rev. Issue Date Prepared Checked

Reference No. NHS/MMB/JOB/009/2017-18

TitleGeophysical Survey followed by Geotechnical Investigations at

Mandwa, Dist Alibaug

ClientMaharashtra Maritime Board

Reference No. Rev Division Date Doc. Information Page

NHS/MMB/JOB/009/2017-18 00 Survey 01.01 2018Geophysical Survey followed by

Geotechnical Investigations at Mandwa Page 2 of 38

REPORT ARRANGEMENT

VOLUME 1: DRAFT REPORT ON SURVEY WITH CHARTS / DRAWINGS

Sl. No. Contents Page

1 INTRODUCTION 5

1.1 General 5

1.2 Objective 5

1.3 Scope of Work & Specification 5

2 SUMMARY OF SURVEY RESULTS 9

2.1 Survey Operations 9

2.2 Survey Boat 9

3 DATA ACQUISITION AND QUALITY CONTROL 10

3.1 Survey line Keeping 10

3.2 Event Marking 11

3.3 Processing of Data 11

4 QUALITY ASSURANCE AND HSE PROCEDURES 11

4.1 Bathymetry 11

4.1.1 Survey System 12

4.1.2 Control of survey 15

4.1.3 Calibration, Verification and Tests 14

4.2 Echo Sounder System 16

4.2.1 Single Beam Echo Sounder 18

4.4 Seabed Type and Features 18

4.4.1 Side Scan Sonar 18

4.4.2 Sub Bottom Profiler System 20

4.4.3 CODA Data Acquisition System 21

4.4.4 Magnetometer 22

5 RESOURCES FOR SURVEY WORK 22

5.1 Equipment summary 22

6 SURVEY DATA PROCESSING AND INTERPRETATION METHODS 24

6.1 Survey Data Processing 24





NHS/MMB/JOB/009/2017-18 00 Survey 01.01 2018Geophysical Survey followed by

Geotechnical Investigations at Mandwa Page 3 of 38

6.2 Bathymetry 24

6.3 Side Scan Sonar 24

6.4 Sub Bottom Profiler System 25

6.5 Magnetometer Data 26

6.6 Data Interpretation Method 27

6.6.1 Bathymetry 27

6.6.2 Seabed Classification 27

6.6.3 Seabed Features 27

6.6.4 Sonar Contacts 27

6.6.5 Shallow Geology 28

6.6.6 Magnetic Anomalies 28

7 RESULTS OF SURVEY 29

7.1 Bathymetry 29

7.2 Seabed Type and Features 29

7.3 Shallow Geology 30

7.4 Magnetic Anomalies 30



Client Maharashtra Maritime Board


NHS/MMB/JOB/009/2017-18 00 Survey 01.01 2018Geophysical Survey at

Mandwa, mumbaiPage 4 of 38

ABBREVIATIONS

CD Chart DatumCM Central MeridianCh ChannelCVT Calibration, Verification & TestDGPS Differential Global Positioning SystemDF Dual FrequencyDPR Daily Progress ReportGPS Global Positioning SystemHSE Health, Safety and EnvironmentkHz Kilohertzkm kilometreKP Kilometer Postm metrem/s metre per secondms millisecondsMP Multi PurposeNHS New Horizon Surveys (I) Pvt. Ltd.QA/QC Quality Assurance / Quality ControlQMS Quality Management SystemRel ReleaseRev RevisionSBES Single Beam Echo SounderSBP Sub-bottom ProfilerSSS Side Scan SonarSoW Scope of WorkUTM Universal Transverse MercatorWGS World Geodetic System

UNITS

UTM grid coordinates and all linear measurements are expressed in metres [m].

Angular values are expressed in degrees (°).





NHS/MMB/JOB/009/2017-18 00 Survey 01.01.2018Geophysical Survey at

Mandwa, mumbai Page 5 of 38

1.0 INTRODUCTION

1.1 General

Maharashtra Maritime Board (MMB client), intended to carry out Geophysical Surveys at

Mandwa. The Client has awarded the survey contract to NEW HORIZON SURVEYS (I) Pvt.

Ltd. (NHS), Navi Mumbai, to carry out the survey and do the technical report accordingly.

These survey services comprised of the provision of personnel and equipment in order to

obtain, interpret and report on the survey data obtained within the survey area. Quality control,

data acquisition and preliminary data interpretation was undertaken in the field for ensuring that

the survey scope and specifications are fully complied with.

This report on survey describes the scope of work, methodologies adopted and equipment’sused for collecting the data, interpretation and reporting of the results obtained from the survey.

1.2 Objective

The basic objective of carrying out the Geophysical survey within the Client specified areaswas:

• To obtain data on bathymetry, seabed topography and sub-seabed geology.

• To acquire magnetometer data and to identify magnetic anomalies, if any.

• To obtain seabed features.

1.3 Scope of Work & Specification

The survey work was conducted in accordance with the specifications and scope of work,

supplied by the Client and the standard survey procedures prepared by NHS. The mutually

agreed scope of work was as follows:

The Geophysical survey was carried out to cover the proposed location Mandwa. The limits

of survey area, as supplied by Client, were as given below.

Table 1.3: Limits of Survey Area

Limits of Survey AreaPoint ID Geographical Co-ordinates

Easting

(W)

Northing (N)1 276675.78 2080975.43







2 276890.43 2081193.393 276917.12 2081589.824 276678.09 2082199.805 276816.44 2082258.746 277066.91 2081598.217 277037.36 2081135.978 276935.03 2081028.629 277039.09 2081029.2610 277039.21 2080946.4911 276886.04 2080948.0112 276886.37 2080975.68

Extended Survey Area13 277074.24 2081600.0014 277243.05 2081169.2015 277036.09 2081029.2616 276822.71 2080918.0117 276739.91 2080843.0018 276674.71 2080868.4819 276626.65 2080964.9220 276645.80 2080987.14

EA

Figure 1: Survey Area







• Competent survey personnel, requisite survey equipment and a locally hiredsurvey boats were mobilised for the survey.

• Geophysical survey of above area was carried out at an 10m line interval byusing DGPS system, single beam echo sounder sub-bottom profiler (Pingersystems), side scan sonar and sea spy magnetometers were deployed on allsurvey lines.

• The Sea Bed Soil (BS) /Grab sample (GS) samples were collected from 7locations A Grab Sampler was used for collecting the surficial soil samples fromthe designated locations. The survey boat was positioned at the proposedsampling locations prior to the deployment of Grab Sampler and the same werevisually analysed in the field and correlated with the results obtained frominterpretation of side scan sonar records. Later, the collected soil samples weresent to a reputed laboratory for sieve analysis. The Locations of Sea Bed Samplesis as follows:-

GS - 1 Easting 276 919.0mE

Northing 2 080 952.0mN















GS – 6 Easting 276 902.93mE


GS – 7 Easting 276 807.7mE


• All survey data acquired from the survey field was processed and quality checkedat NHS Office, Nerul in Navi Mumbai.

• Comprehensive Report and Charts on geophysical survey are enclosed

herewith.







2. SUMMARY OF SURVEY RESULTS

The section below contains the summary of the results of Bathymetry and Geophysical

survey undertaken within the Client supplied survey area.

2.1 SURVEY OPERATIONS

Mobilisation

The survey equipment were mobilised on board on 13 October 2017. The survey equipment

calibrated on the 14 October 2017. After testing / calibration / verification of all survey

equipment, the survey was commenced on 14 October 2017 and extended area was

completed on 19 October 2017 .

2.2 Survey Boat

Locally hired boat was utilised for carrying out the Bathymetry and Geophysical survey.

Vessel Offset Diagram

The location of the various survey sensors on the survey vessel is given in the vessel

offset diagram on the chart accompanying this report.







3. Data Acquisition and Quality Control

3.1 Survey Line Keeping

Survey lines were planned as per scope of work and digital pre-plots for the area were

prepared prior to commencement of survey. These lines were run on the navigational

computer while executing the survey and this enabled the Navigator to guide the survey

boat along the planned survey line all the time.

Online Data Quality Control

The online navigation computer was interfaced to the Hypack 6.2b Navigation system

providing regular navigation updates and fix annotation strings. All computers

connected to the Navigation network were synchronised with the DGPS. Quality of

geophysical data being recorded was constantly monitored in Local time, and fine tuned

to obtain the best quality. The data was logged in raw Hypack format for replay under

various parameters required. In addition to this, the side scan sonar and sub-bottom profiler

data were recorded in .cod formats respectively for immediate availability of the data to the

geophysicist for interpretation.

Navigation

The DGPS system performed well at all times. The performance of the SPS-351 DGPS

system was continuously monitored.

Echo Sounder

The Odom Hydrotrac single frequency single beam echo sounder performed well

throughout the duration of the survey.

Seaspy Marine Magnetometer (Maggy)

Seaspy Marine Magnetometer performed well throughout the duration of the survey.

Side Scan Sonar Geo Acoustics SS 941

Geo Acoustics side scan sonar system performed well throughout the survey period. The tow

system was operated as per recommended manufacturers procedures. The tow fish was towed

astern of the survey vessel and its height above the seabed was maintained 10 to 20 % of the

horizontal range, providing optimum seabed return. The tow fish was tracked continuously

using conventional ‘layback Method’.

Sub-bottom Profiler (Pinger)







Sub-bottom Profiler (Geopulse pinger) system performed well during the survey. The

system was configured to the optimum settings so as to achieve maximum sub-seabed

acoustic signal penetration within the survey area.

CODA Octopus DA4G

The CODA Octopus Geosurvey suite DA4G geophysical digital data acquisition systemperformed well throughout the survey.

3.2 Event Markings

The on-line computer system was interfaced for closure to the analogue traces on the survey

vessel. Event marks corresponding to position fixes were generated automatically from the

on-line Navigation Computer interface and passed to the analogue recorders at regular

intervals of 1sec.

3.3 Processing of Data

The survey data pertaining to bathymetry survey was logged using Hypack. Logging

module and further processed in Hypack Processing software. The geophysical data was

processed and interpreted using CODA Octopus Geophysical suite and the results were

finally presented in drawing form using the Auto CAD for windows.

4. Quality Assurance and HSE Procedures

NHS has fully documented and duly audited Quality Assurance and Health, Safety and

Environmental System procedures in place. The same are followed during all surveying

tasks undertaken by the company.

Competent field survey staffs were provided by NHS to constantly monitor data quality as

the survey progressed, and duly documented.

4.1 Bathymetry

Bathymetry Survey was carried out by using SPS-351 DGPS, Odem Hydrtrac Single Beam

Echo Sounder, Hypack Navigation & data logging software. The survey lines are planned

10m line interval within the survey area.

Geodetic and Projection Parameters

The survey was conducted in WGS84 Datum and the results plotted in Universal Transverse







Mercator (UTM) Projection. Details of Spheroid and Grid system used for this survey are asfollows:

Table 4.1: Geodetic Parameters

Local Datum Geodetic Parameters

Spheroid WGS-84Datum Transformation None

Semi-major axis (a) 6378137.0000 m

Semi-minor axis (b) 6356752.3142 m

Eccentricity 0.0818 191909 28906

Inverse flattening (1/f) 298.257223563

Projection Parameters

Grid Projection Universal Transverse Mercator

Central Meridian (CM) 75 o East (Zone 43)

Origin Latitude (False Lat) 0.0o

Hemisphere North

False Easting (FE) 500000.0 m

False Northing (FN) 0.0 m

Scale Factor on CM 0.999600

Units International Metres

4.1.1 SURVEY SYSTEMS

6.1 Positioning System: Trimble SPS-351 dGPS NavigationThe Trimble® SPS-351 DGPS receiver is an ideal solution fordynamic real-time marine positioning operations such as harbordredging and for commercial positioning applications where it isintegrated as the positioning sensor component. The modular GPSreceiver with antenna options accepts GPS corrections from a varietyof sources allowing the user the choice of sub-meter to centi-meterperformance.

The SPS-351 receiver is a high-quality solution for applications thatrequire submeter, decimeter or centimeter positioning in demandingenvironments.







The SPS-351 receiver offers a wide range of GPS positioning methods and associated accuracies foroffshore and onshore marine construction applications.

Satellite Based Augmentation Systems (SBAS) such as WAAS, EGNOS and MSAS IALA compliant Navigation Beacon OmniSTAR VBS service1 RTCM from a site based DGPS Reference Station OmniSTAR XP/HP1 Real Time Kinematic (RTK) for maximum precision

The SPS-351 receiver is designed for easy integration into onboard systems. The built-in displayand keyboard offers fast configuration and status information. The position, velocity, correctionstatus and time is available from the data ports in NMEA 0183 or NMEA 2000®. The SPS-351receiver outputs position reports data at rates up to 10 Hz. The 3 serial ports can also be used forsetup, control, and data output using Trimble Standard Interface Protocol (TSIP) providingcompatibility with with previous DSM receiver model installations.

Specifications

Trimble EVEREST multi-path mitigation technology DGPS: 12 Channel L1 plus 2 channels for Beacon DGPS with SBAS (WAAS / EGNOS / MSAS): 11 GPS channels plus 1 for SBAS RTK or OmniSTAR VBS/XP/HP: 24 channel L1/L2 plus 1 channel L Band Code differential GPS

positioningHorizontal accuracy. . . . . . . . . . ±(0.25m + 1 ppm) RMS ±(0.8 ft + 1 ppm)

Vertical accuracy. . . . . . . . . . . . ±(0.50m + 1 ppm) RMS ±(1.6 ft + 1 ppm)

WAAS / EGNOS / MSAS1

Horizontal accuracy. . . . . . . . . . .Typically 1m (3 ft)

Vertical accuracy. . . . . . . . . . . . Typically <5m (<16 ft)

OmniSTAR Positioning

VBS Service Accuracy. . . . . . . . Horizontal typically better than 1 m (3 ft)

XP Service Accuracy. . . . . . . . . . Horizontal 10cm (.3 ft), Vertical 20cm (.7 ft)

HP Service Accuracy. . . . . . . . . . Horizontal 5cm (.2 ft), Vertical 10cm (.3 ft)

OmniSTAR XP/HP Convergence. . Cold start - Typically 10 to 40 minutes depending on satellitegeometry

Navigation System: Hypack 6.2b NAVIGATION SOFTWARE







HYPACK® 6.2b is a Windows™-basedNavigation software package used primarily forhydrographic surveying and data processing.

This all-in- one module provides the surveyorwith all of the tools needed to design their survey,collect data, process it, reduce it, and generatefinal products. Whether collecting hydrographicsurvey data or environmental data, or positioninga vessel in an engineering project, HYPACK®provides the tools needed to complete the job.

The standard package has everything needed todesign from carrying out survey, collect singlebeam data, process it and generate final products, such as contours, plotting sheets, output forCAD, fly-throughs, cross sections and volumes. The sides scan sonar collection and processingmodules are now standard features.

This software can be interfaced simultaneously to Echo sounders, attitude sensors,Environmental sensors, Acoustic, GPS and Total Station positioning and all the data acquiredcan be stored in Microsoft Access database. It also enables graphical data cleaning.

Software Preparation Procedures

The entire computer package with peripherals was set up in the workshop and the engineer usingdedicated test programs tested each unit. This also included the interfacing tests, which wereprovided in the Software. Once all the tests were completed Hypack 6.2b NAVIGATIONSOFTWARE online system was started and tested as a whole. The overall test included datastorage, video display, interfacing, printing and plotting of results.

Run lines, Job files and Survey Data Files

The validity of all input information to the survey online data file and run line files is ofparamount importance to each survey. The first check was the comparison of the Hypack 6.2bNAVIGATION SOFTWARE Nav printout with the supplied co-ordinate and /or delay listing.

4.1.2 Control of Survey







Horizontal Control (X,Y)

Surface Positioning:- SPS-351 DGPS Positioning System was used for positioning the

survey vessel during this survey by maintaining accuracy in Horizontal Control. Navigation

of the survey vessel was controlled by Hypack6.2b PC based Navigation system.

Hardware Preparation Procedures

The hardware used for the Hypack 6.2b NAVIGATION SOFTWARE navigation and dataacquisition package was interfaced with HP Laptop with appropriate peripheral devices. Toperform the office test procedures, the following items were interfaced:

HP Laptop

Hypack 6.2b NAVIGATION SOFTWARE

Oscilloscope

Hyper Terminal (Interfacing Test)

All computers and peripheral devices were tested by means of standard system firmware. Theinterfaces and devices were tested by means of Hypack 6.2b NAVIGATION SOFTWARE.Where it is not possible to connect devices in the office, the interfaces were tested usingsimulated data strings.

Hardware Mobilization Procedures

The following test procedures were carried out for installing the hardware in the boat:

The voltage and Frequency of the power supply were checked and proper grounding was done.

The computer was setup and interfaced to the survey sensor and devices. All interactions werechecked and confirmed that the interfacing is functional. Debugged any error if found in thecable connecting the systems and the data transfer was verified.

Check the validity of inputs via interfacing depths, positioning data, sensor data etc.

Check all back up interfaces, computers and peripherals and protocols.

Offshore Operating Procedures

The boat is having operating manual(s) on board for all Hypack 6.2b NAVIGATIONSOFTWARE modules in use. The surveyors makes references to these manuals on the correctmethod of the system operation if found necessary.







Fix Numbers & AnnotationA unique fix numbering system starting and increasing from 1 without duplication was used forthe project. A test was conducted to verify that the annotation of fixes is synchronized with thepositional fixes. This test also confirmed that the annotation is correct and is factual.

Check ProceduresThe surveyor ensured that the online data was of good quality and that the correct survey datawas being used. The points to be checked at the start of each shift would include the following:

Is the correct survey constants data file in use? Are all the pre-plots drawn? Are all the line data files at hand? Are sufficient consumables available?

When the above points are found satisfactory the field work commences. Processing was alwayscarried out accordingly to the guidelines as described in the processing procedure.

The survey gyrocompass, interfaced to the navigation computer, was aligned to the boatscentreline and calibrated. This provided the navigation computer with real time orientation andas a result, the selected offset positions’ co-ordinates were continuously computed

4.2 Echo Sounder System: Odom HYDROTRAC

Odom Echosounder was used during the entire survey to recordreferenced bathymetric data for measuring water depths. Digitizeddata was confirmed by the inspection of analogue records.

Pre-mobilization Checks

The Echosounder system was bench-tested prior to mobilization. Theoutboard transducer pole was marked, from the base of the transducershoe, at 0.6 metre intervals (these marks were then used to confirmtransducer draft once the equipment was deployed in the field).

The Bar-check/Hand Lead line was then used to confirm the marks atregular one meter intervals and that the marks were readilyidentifiable.

The Echo-sounder was then interfaced with the Navigation and Data Logging computer to confirm thatthe digitisation of depths was actually correct and to check the system was completely operational.







Installation and Calibration

The Echo-sounder system was installed and operated in accordance with the manufacturers instructions.Portable transducer was installed rigidly to a bracket at suitable location on the survey vessel. Thetransducer shoe was sufficiently deep not to experience turbulence and aeration when the vessel steamsat survey speed. The depth of the transducer below water line was ascertained by reference to presentmarks on the pole.

Prior to commencing survey work in the filed, the Echo-sounder was calibrated against a bar check. Theprocedure was to confirm the following constants:

Tx =To establish index error (combined effect of transducer depth and delays in the

recorder)

Vp = To confirm velocity of propagation of sound in saline water

With the vessel stationary in the water, the bar-check bar was lowered to at least 2m below thetransducer and the nearest mark on the chain set at the water line. Once the transmission mark was setthe apparent depth of the transducer was noted on the analogue record and recorded in the deck log forfuture reference. Great care was taken to ensure that the transmission line did not shift thereafter.

The bar was then lowered at regular intervals to the maximum practical depth. The bar was allowed tosettle at each depth. On recording the maximum obtainable depth the Bar was similarly stepped back tothe surface. The digitised depths were also checked during the Bar-check calibration.

Data Reduction and Presentation

The system was operated following recommended manufacturer procedures. The vertical paper scalewas at 1:10 and the appropriate phase was selected to display the seabed at all times. Transducer offsetwas logged and applied during subsequent processing. Event marks corresponding to position fixes weregenerated automatically from the on-line navigation computer interface, and passed to the analoguerecorder at a regular interval. Prior to the processing, all raw-data files were backed up.

ODOM HYDROTRAC SETTINGS

Frequency 210 Kilo Hertz

Range on record Auto

Vertical Scale 1:10.1:20 and 1:40

Positioning / Tracking Fixed offset

Transducer Depth 2.0 m below water line

• All raw water depths were reduced to Chart Datum using observed tide data.

• The seabed within the survey area was gently sloping down towards North west.

• No significant bathymetric undulations were recorded within the survey area except

the uneven seabed observed on the rock outcropping areas.







• Water depths from CD within the survey area were ranging between a minimum of

-0.7 m and a maximum of 3.0 m.

4.2.1 Single Beam Echo Sounder

Odom Hydrotrac single frequency single beam echo sounder, with transducer operating at210 kHz frequencies was used for measuring water depths. Sound velocity measurementswere carried out on a regular basis and the average sound velocity was fed into the echosounder accordingly. Digitised data was confirmed by inspection of analogue records.Prior to commencing survey works the echo sounder was calibrated against a ‘Bar Check’.The summary of the results of‘Bar check’ is givenbelow:

Table 4.3 Results of SBES Bar Check – M/B YANN

SBES Bar check Results Summary

Date, Time[UTC]

SerialNumber

NameDraftSet [m]

WaterColumnVP [m/s]

FrequencyLogged[kHz]

Bar checkResults [m]

High[210]

Low[33]

MeanDifference

SD

14-10-2017,12:10

257035 SBESHydrotrac

0.60 1539 √ -0.01 0.004

The offsets of the echo sounder transducer from Central Reference Point on the survey

vessel were measured, recorded and reported in the mobilisation report.

On completion of successful Mobilisation, Calibration, Verification, and Testing of all

equipment as per the relevant work practices, the bathymetry survey task was commenced.

4.4 Seabed Type and Features

4.4.1 Side Scan Sonar: Geo Acoustic SS 941The Geo Acoustic SS 941 dual frequency sides scansystem capable of producing high quality records ineither tow fish or ROV mount configuration. Thesystem can output analogue sonar records to a varietyof Graphics Recorders. These Sonar signals are alsoavailable for recording on DAT Tape Recorder or to aSonar Digital Acquisition System for further







processing. The fish can be configured as an electronics pod and 2 transducers for easy integration ontoother platforms such as Sub-bottom Profilers or ROVs. Either a short (up to 200m) soft tow cable or alonger double armoured cable on winch can tow the fish.

The side scan sonar 159 D tow fish was operated at a frequency of 100 KHz. The tow fish height wasmaintained at approximately 5 to 10% of the range setting, from the seabed when possible. A side scansonar range of 50 meters was set for the entire survey.

The side scan sonar system, along with the navigation system was interfaced to CODA DA 4G for realtime Digital Data Acquisition. The acquired data was geo-referenced and time stamped. All the acquireddata was recorded onto DVD’s in CODA digital format for future processing.

Survey speed was maintained between 3.5 and 4.5 knots.

GEO ACOUSTICS SIDE SCAN SONAR SETTINGS

Frequency 100 kHz / 500kHz

Range 50m

Beam width 1 degree (variable)

Recorder CODA DA 4G Digital Recording

Positioning/Tracking Ship referenced layback

Table4.5.1: Geo Acoustics Side scan Sonar Settings

• Three types of seabed reflectivity were observed on the side scan sonar records.

Type 1: Low Reflectivity (Soft Clay)

Type 2: Low to Medium (Silty Clay)

Type3: Medium (Compacted sediments)

• Type 1and Type 2 sediments were predominant within the survey area.

• Type 3 sediments were predominant at south side of the survey area.

• Hard seabed was observed in two locations within the survey area.

• No other significant seabed features were identified within the survey area.

Sonar Contacts

• Six (6) debris were observed within the survey area.

Side Scan Sonar

Dual-channel dual frequency GeoAcoustics side scan sonar system and industry best known

Geo-Octopus CODA DA4G geophysical digital data acquisition system were used for

acquisition of side scan sonar data within the area.







Rub Test:- The side scan sonar system was set up on the deck of the survey vessel and a

‘rub test’ was carried out on both the port and starboard transducers of the tow fish. The

gain and grey-scale settings were adjusted to balance the port and starboard channels of the

side scan sonar system.

Wet Test:- The tow fish was thereafter, lowered into the water and a ‘wet test’ was

performed to check that echo from targets were returning to both the channels. Side scan

sonar settings used in the field were as follows

Position of the side scan sonar tow fish was continuously logged during the survey

following conventional ‘layback method’. The side scan sonar data was digitally recorded

on system hard disk using CODA DA4G digital data acquisition system.

Shallow Geology

• The maximum acoustic signal penetration achieved within the survey area was

approximate 10 m below seabed.

• The order of super position of the sedimentary units within the survey area and

its textural characteristics interpreted were as follows.

- soft clay

- silty clay( with shell fragments/gravels/boulders)

- compacted sediments

• Soft clay and soft to silty clay units were the topmost geological unit throughout the

survey area except in areas wherever rock out crops was recorded. Isopachs at 1 m

interval, showing the thickness of this unit, are depicted on the charts.

• Interpretative geological profiles along all the longitudinal survey lines are

depicted on the charts.

4.4.2 Sub Bottom Profiler system: Geo Acoustic 5430 A

Sub-bottom profiling was carried out by a GeoacousticsGeopulse profiler system consisting of a Geopulsetransceiver (Model 5430 A) and over the side-mounttransducer (Model 132) Geopulse profiler system TheGeoPulse Sub-bottom Profiler is a tried and tested,industry standard sub-bottom profiling system for shallowgeophysics. It provides versatility both in sub-bottomprofiling and pipeline detection. It is highly flexibleallowing operation as either a hull mounted deep water







system, an "over-the side mount" system for small boat operations or as a towed system.

The system consists of a transducer with a tow cable, and an interconnecting cable from the winchto the transmitter or transducer. The Transmitter (Model 5430A) allows control of the outputpower, frequency and the number of full cycles included in the outgoing pulse. The frequenciesavailable are in the range of 2 to 12 kHz.

Seabed returns can be conditioned by analogue means using the GeoPulse Receiver (Model 5210A)or digitally using a wide range of third party processing systems.

The transducer can be side mounted, mounted on a keel of the boat or towed with a tow cable. Thestreamlined vehicle produces little flow noise from interfering with signal reception. Thetransducers are thus operated in an optimum noise environment, where machinery noise and theeffects of flow and bubbles around the ship’s hull are minimized.

Data was recorded on to DVD’s CODA format on CODA DA 4G digital recording system.

GEOPULSE PINGER

Resolution 0.1 metersPenetration Achieved Maximum 10 meters below seabedDelay ZeroPulse frequency 3.5 kHzPulse Width 2 ms / AutoBand Width 2 kHz /AutoRepetition Rate 2500 ms (4 pps)Sweep Time 35 msRecorder CODA DA 4G Digital RecordingPositioning / Tracking Fixed offset

Table 1: Geoacoustics Pipeliner 5430 A transceiver settings

4.4.3 CODA DA4G Data Acquisition system

The side scan sonar data and sub-bottom profiler data was

logged in digital format using geophysical data

acquisition system running the CODA DA4G Octopus

software. The SSS and Sub-bottom profiling data was

logged in .cod format

The CODA DA4G Data Acquisition system allows acquisition of







data from a number of sources and records them simultaneously on DVD RAM disks/ DAT Tapes. Ithas the ability to record data in high-resolution digital format, which does not degrade with time, andallows the data to be recorded on DVD’s.

Coda DA4G Data Acquisition system was interfaced to the Side Scan Sonar/ Sparker Systems. Theinternal trigger of DA4G was used to trigger the side scan sonar and sparker system and record thesonar data digitally using three digital channels, one for seismic and two for sonar data.The Coda System was interfaced with the Hypack Navigation for Navigation data overlay.

4.4.4 Magnetometer

Marine Magnetics Sea SPY Marine Magnetometer was

deployed for the magnetometer survey for identifying the

magnetic anomalies within the survey limits . The

system is an Over hauser magnetometer system which

measures the ambient magnetic field using ‘Nuclear

Magnetic Resonance Technology’. The high sensitivity

of the system enabled to detect even small targets at

quite large distances, depending on the background

magnetic noise level.

The system was interfaced to the SeaLink computer and the magnetometer data was logged as

‘XYZ’ files. The online monitoring of the magnetometer data was achieved utilising C-Nav 3050

Navigation control. The magnetometer tow fish position was logged continuously following

conventional ‘Layback Method’. The cycling rate for the magnetometer was at 1 Hz

throughout the survey.

Magnetic Anomalies

• No unknown Magnetic Anomalies were observed in the survey area.

5 RESOURCES FOR SURVEY WORK

5.1 Equipment Summary

Following equipment and systems were mobilised for the survey work. The equipmentsetup and configuration diagram on the survey vessel is placed at Figure 2.1.

Table 5.2: List of Survey Equipment Mobilised for Survey Work







Equipment /System

Description / Make / Model/Resolution /Accuracies

Software /Navigation

HYPACK Survey PC based data acquisition and survey vesselnavigation package

Positioning GPS Trimble SPS351

Single beam EchoSounder

Bathy 500DF

Side scan sonar GeoAcoustics Side Scan Sonar System(SS941 Transreceiver + 159 DF towfish 100 / 410 kHz transducers +soft tow cable + associated consumables & spares).The side scan sonar data was logged digitally into a hard disk usingGeoOctopus CODA DA4G Series Digital Data AcquisitionSystem

Equipment /System

Description / Make / Model/Resolution /AccuraciesSub-bottom Profiler(Pinger)

Geopulse pinger. The sub-bottom profiler data was logged digitallyinto a hard disk using CODA DA4G

Geophysical DataAcquisition System

Geo Octopus CODA DA4G Geophysical Data Acquisition System

Magnetometer Marine Magnetics Sea SPY Marine Magnetometer system + associatedconsumables & spares.

Magnetometer DataLogger

Sea Link Magnetometer Data Logging System to Log the MagneticField

Soil Sampling Grab Sampler + associated consumables & spares







6 SURVEY DATA PROCESSING AND INTERPRETATION METHODS

6.1 Survey Data Processing

General

The survey data were logged in Hypack Raw file format (.raw), and processed using

the Hypack Processing software. Heading, motion and position data were

processed and checked to ensure good data quality. The position data for the various

geophysical instruments were processed and plotted to allow commencement of the

interpretation of the geophysical data.

Navigation and Positioning

The measured offsets for all survey sensors were entered into the navigation system

and processed using Hypack to enable track charts to be plotted and ‘corrected’navigation files to be integrated with other sensor data during post processing. These

included:

• DGPS position absolute of the primary positioning system

• Common Reference Point

• Single beam echo sounder

• Side scan sonar layback derived position

• Pinger layback derived position

• Hydrophone layback derived position

• Magnetometer layback derived position

6.2 Bathymetry

Hypack processing suite was used to import, quality check, and process the

navigation, bathymetry, tides and sound velocity data. The data was filtered,

cleaned, and combined to create geographically positioned bathymetric data set that

has been corrected for tides and sound speed.

6.3 Side Scan Sonar Data

Side scan sonar data was acquired and processed using CODA Geo survey

processing suite, Side scan sonar mosaics were created for interpreting seabed

features.







The Geo survey software provided real time processing of CODA raw files created

during acquisition of side scan sonar data which was stored in hard disk. CODA

Da4G is a real time data acquisition system for sonar and seismic data. The data

was logged to hard disk and was directly sent to the data processing system called

Geo survey.

CODA was also interfaced to Hypack Real time navigation system that provided the

time stamp for the geophysical data, the vessel position, heading, water depth, and

line name information.

Output was controlled by specifying or editing various parameters, e.g., filter

settings, automatic bottom tracking settings for knowing the fish height at any given

point of time, time variable gain settings, output file format (CODA / CAMOS)

settings.

CODA files had navigation populated in them and was merged with post-processed

navigation data (.nav files) later on. The Navigation files contained the original

Easting and Northing positions as well as the processed and traced position data

field with the name Corrected Easting and Corrected Northing.

The data was processed further and interpreted using Geo survey. It has two main

functions, one is making side scan sonar mosaic imagery and another is allowing the

user to perform graphical interpretation / digitization of the sonar data. Individual

COD files were grouped together as a mosaic to interpret the seabed features. The

interpretation was exported as report text / vector file. The interpreted features

were then plotted / opened in Micro station / AutoCAD software and saved as .dgn /

.dwg file for charting.

6.4 Sub-bottom Profiler Data

Sub-bottom Profiler Data (Seismic Data) was processed using G eo s u r v e y to

interpret sub seabed geology within the survey corridor.

The Geo survey software provided real time processing, or post processing from

CODA files of seismic acoustic signals.

Geo survey provided real-time processing or post processing of acoustic data, which







had been collected by CODA DA4G. CODA was interfaced directly to Hypack via

Moxa connection. The Geo survey software allowed to process and display the

acoustic data on the computer screen and to record it in .cod format.

Output was controlled by specifying or editing various parameters, e.g., filters

settings, automatic bottom tracking settings, swell settings, time variable gain

settings, output file settings and printer settings.

Seismic .COD files had navigation populated in them and could be upgraded with

post-processed data with Navigation. The Navigational and depth data, with which

the .COD files were updated, was stored in files. These contained the original

Easting and Northing positions as well as the processed and filtered, Corrected

Easting and Corrected Northing positions.

The interpretation of the sub-bottom profiler data (.COD format) was done using Geo

survey seismic processing software. Various "filters", "data enhancement" and

"display options" were applied to the data until the best visual representation was

PL,MPLPLK digitised interpretation. Similarly, the software appends the

coordinates and other navigation information to the digitised sub- seabed reflectors of

each .COD files. The digitized points were then exported to a data file containing the

XYZ (Easting, Northing, and Depth) information. These points were plotted using

Microstation / Auto Cad for charting.

6.5 Magnetometer Data

The Sea spy Marine magnetometer was interfaced to the S e a L i n k software

computer and the data was logged as ‘XYZ’ files using Sea Link. Logging. The

online monitoring of the magnetometer data was achieved by using Auto tun ing .

The magnetometer tow fish position was calculated using conventional ‘Layback

Method’ and was logged as separate ‘XYZ’ files.

Later on, the data in the ‘XYZ’ files were processed and the navigational data was

merged using Maggi processing software. The magnetometer data was reviewed and

interpreted from the processed files using Maggi Processing software which could

display the data graphically.

The magnitude of the anomaly and duration (width in meters) were measured from







the graph and plotted in AutoCAD. The results were presented in the seabed

features panel of the chart and tabulated in the text report.

6.6 Data Interpretation Methods

6.6.1 Bathymetry

The recorded depths within the survey area were reduced to chart datum usingreal time tide data which is recorded within the survey area

The following classification was generally adopted to definebathymetric gradients:

<1° Very gentle

1° - 5° Gentle

5° - 10° Moderate

10° - 15° Steep

>15° Very steep

6.6.2 Seabed Classification

The nature of the seabed sediments within the survey area was classified primarily

based on the reflectivity pattern of the seabed observed in the side scan sonar

records. Appropriate references from single beam echo sounder data, sub-bottom

profiler data and soil samples taken by Grab samples were taken as and when

required.

6.6.3 Seabed Features

Attributes of different seabed features within the survey were established primarily

from the side scan sonar data. Appropriate references from single beam echo

sounder data and sub-bottom profiler data were taken wherever required.

6.6.4 Sonar Contacts

Individual features with high reflectivity with specific texture and pattern on the side

scan sonar records were termed as sonar contacts. These include, but are not limited

to the following:

Debris : Defined as most probable manmade object. Object having

length and width or length, width and height. It has got definite

shape and outline on the side scan sonar records.







Hard Contact : Defined as an object with a high acoustic reflectivity on the

acoustic records with no measurable height above seabed. This

can be manmade or objects with geological origin.

Linear Contact : High reflective linear feature observed on the side scan sonar

records, generally of unknown origin, with their length being

prominent compared to width and height.

6.6.5 Shallow Geology

All sedimentary units defined in the chart and respective sections of the text report

are based on an assessment of the recorded acoustic characteristics of the seabed and

sub-seabed nature of sediments. A constant primary-wave velocity of 1600 m/sec

was used for the two-way travel time to depth conversion. The different sedimentary

units were interpreted and digitized in the sub-bottom records.

Isopachs of the topmost sedimentary unit are depicted on the charts. Isopachs

are contours connecting points of equal thickness. Isopachs are true stratigraphic

thicknesses; i.e. perpendicular to bedding surfaces.

6.6.6 Magnetic Anomalies

The cycling rate for the magnetometer was kept at 1 Hz throughout the survey.The value of the magnetic anomalies depends on several factors such as distance

from the source causing the anomaly, direction of magnetisation of the source with

respect to the earth’s field, ferrous content of the object, ambient magnetic noise etc.

No conclusions could be drawn from the value of the magnetic anomaly alone

regarding the nature or type of the source causing the anomaly. The positional

accuracy of the interpreted magnetic anomalies depends on a combination of the

vessel positioning, layback calculations for the tow fish relative to the vessel.







7. RESULTS OF SURVEY

The results of geophysical survey carried out for the area as defined in Table 2 are detailed inthe following sections.

7.1 Bathymetry

All raw water depths were reduced to Chart Datum using observed tides.

In general, the seabed within the survey area was gently sloping down towards North west,

i.e. from shore line towards sea. No significant bathymetric undulations were recorded within

the survey area except the uneven seabed observed on the rock outcropping areas.

Water depths from CD within the survey area were ranging between a minimum of -0.7 m

(at the southern extreme of the survey area, near to shore line) and a maximum of 3.0 m.

Isobaths at 1 m interval are depicted on the charts. Generally, Isobaths within the survey area

are oriented parallel to the coast line, except the unevenness observed at the rock outcropping

areas.

7.2 Seabed Type and Features

Seabed sediments within the survey area was classified into following types based on the

acoustic reflectivity observed on the side scan sonar records.

Type 1: Low ReflectivityType 2: Low to Medium ReflectivityType 3: Medium Reflectivity

Low reflective seabed – Interpreted as soft clay.Low to Medium reflective seabed –Interpreted as silty clay (shells/gravels).Medium reflective seabed – interpreted as outcrop (Compacted sediments).

As the Side Scan Sonar image is inverted, it is to be noted that the high reflectivity may berepresented as dark tonal values on the side scan sonar mosaic map and vice-versa.

Seabed Features:

Area disturbed seabed due to vessel/barge anchorage were observed with in the area.

Sonar Contacts:







Apart from the above six (6) debris were observed within the survey area those derbis aredepicted on seabed features charts.

7.3 Shallow Geology /Sub Bottom Profiling / Seismic

The sub-seabed acoustic signal penetration achieved was variable within the survey area and

the maximum penetration achieved was approximate 9 - 10 m below seabed. Scattering

of the acoustic signals due high acoustic impedance offered by the shelly layers were the

limitations in achieving better acoustic signal penetration within the area of interest.

From the sub-bottom profiler records, the stratigraphic sequence within the surveyed area canbe broadly classified into four major sedimentary units

Unit A bound by seabed at the top, R1 at bottom, it interpreted to be soft clay, locally someinternal reflectors were observed within this unit.

Unit B interpreted to be soft to silty clay, this unit bound by reflector R1 at the top and R2

at bottom.

Unit C is interpreted to be silty clay, this unit bound by reflector R2 at the top and R3 at

bottom.

Unit D is interpreted to be comprised consolidated sediments such as dense sediments

(possibly stiff clay/rock). This unit bound by reflector R3 at top and down to the limit of

penetration.

Note: Internal Reflector (IR) was observed with in unit A. In some areas unit A, unit B and

unit C were absent where outcrop is present and it was observed only in three locations

(presented in seabed features chart) within the survey area.

The thickness of this unit was varying between 0 m and 4 m within the survey area.

Isopatches at 1 m interval, showing the thickness of this unit, are depicted on the charts.

7.4 Magnetic Anomalies

A SeaSpy marine magnetometer was deployed in all lines within the survey area to detect ferrousobjects on the seabed and within the shallow sediments.

No unknown magnetic anomalies were observed with in the area of interest. The anomalies whichare observed are due to existing infrastructures.







DIARY OF EVENTS

Diary of EventsDate Events12th October 2017 Work Order Received from MMB13th October 2017 Mobilisation of equipment.14th October 2017 Survey started, survey in progress15th October 2017 Survey in progress, survey completed.18th October 2017 Survey area extend by the client.19th October 2017 Mobilisation, survey, demobilisation completed.







Side Scan Sonar Field Record - Extract No. 1

Project Geophysical Survey, Mandwa

Location :Mandwa

Survey Type : Geophysical Survey

PL Route : NA Survey Line No : 7

KP No : NA Fix No : NA

`General Information Results of InterpretationDate ofSurvey

14th to 15th Oct 20172013

Observed outcrop with in the survey areaVessel SmallboatSurveyEquipment

GeoAcoustics SideScan SonarRecording

MediumCODA DA4G System

Frequency 500 kHzRange 40 m







Side Scan Sonar Field Record - Extract No. 2

Project Geophysical Survey

Location : Mandwa Survey Type : Geophysical Survey



General Information Results of InterpretationDate of Survey 14th to 15th Oct 2017 Observed outcrop within the survey areaVessel Small BoatSurvey Equipment GeoAcoustics Side Scan

SonarRecording Medium CODA DA4G SystemFrequency 100 kHzRange 50 m







Sub Bottom Profiler Field Record - Extract No. 1




KP No : NA Fix No : 2988-3025

General InformationDate of Survey 14th to 15th Oct 2017 outcropVessel Small BoatSurvey Equipment Geopulse PingerRecording Medium CODA DA4G SystemFrequency 3.5 kHzRange NA









Location : Mandva Survey Type : Geophysical Survey


KP No : NA Fix No : 8937-9028

General InformationDate of Survey 14th to 15th Oct 2017 Compacted sedimentsVessel Small BoatSurvey Equipment Geopulse PingerRecording Medium CODA DA4G SystemFrequency 3.5 kHzRange NA












General InformationDate of Survey 14th to 15th Oct 2017 Observed rock outcrop within the survey areaVessel Small BoatSurvey Equipment Geopulse PingerRecording Medium CODA DA4G SystemFrequency 3.5 kHzRange NA







Magnetometer Field Record - Extract No. 1





General InformationDate of Survey 14th to 15th Oct 2017 Magnetic anomalies due to existing infrastructuresVessel Small BoatSurvey Equipment Geopulse Pinger

Recording Medium CODA DA4G SystemFrequency 1kHzRange NA







Sr.No.

Drawing Title Drawing Reference No. ScaleNo ofcharts

1 Bathymetric Chart- Sounding NHS/MMB/Bathy/01/2017-18 1:2000 1

2 Survey Line plan chart NHS/MMB/Line/02/2017-18 1:2000 1

3 Seabed Features Chart NHS/MMB/Seabed/03/2017-18 1:2000 1

4 Geo profile Chart NHS/MMB/GP/01/2017-18

1:2000 &Vertical scale

1:2005

For New Horizon Surveys (I) Pvt. Ltd.

(Nandkumar Y.Vhanmane)

Managing Director

+91 9930 416 996

Encl: As Above

new horizon surveys (i ) pvt. ltd. and... · report dear sir, refer to ... conducting standard...

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