From Land to Sea UXO detection surveys in the intertidal and nearshore environments

THS UXO Survey Seminar 19th June 2015

David Rider MSc

Outline

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• Introduction

• Welcome

• Company Overview

• What is the intertidal zone.

• Land Techniques and Equipment

• Case Studies

• The Gap

• Survey Design

• Lessons Learned

• The Future

Introduction David Rider MSc

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Project Geophysicist with Bibby HydroMap Ltd. for over 5 years

Bangor University Applied Marine Geosciences Masters

Hydrographic Surveyor for 2 years

Background in Outdoor Education and Water Safety

David Rider MSc

Introduction Company Overview

7 About Bibby HydroMap Committed to Quality and Innovation

Established in 1997

Since 1997, we have worked closely with clients

from the oil and gas, offshore renewables,

submarine cables, ports and harbours,

aggregates and utilities industries to provide

efficient and cost-effective survey services.

100+ Personnel

Bibby HydroMap employs over 100 personnel

with a wealth of experience and expertise

covering the disciplines of hydrography,

engineering geophysics, marine geotechnics,

engineering geology, oceanography and

maritime archaeology.

Own Fleet and Equipment

With a focus on innovation, we invest in the

custom-build survey vessels and the latest

offerings from industry leading

manufacturers.

8 Survey Services A summary of our core offering

Multibeam Bathymetry Side Scan Sonar Sub-bottom Profiler

Multichannel Seismic UXO Geotechnical Sampling

What is the intertidal zone?

10 Intertidal Zone

Highly Changeable

Tide cycle, Springs and Neaps

Weather

Accesses Time

“Intertidal zone” (noun)

the area between the land and sea that is covered by water at high tide and uncovered at low tide.

Dictionary.com

No man’s land, not quite marine, not quite land.

Muddy Different Sediments

Wet Creeks

Beach Slope Vegetation

Land Techniques and Equipment

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Geometrics G858 Mag Mapper – Industry Standard

Rapid sampling rate 10Hz

Very high sensitivity

Portable Caesium vapour magnetometer

Can be set up with 2 sensors as either a vertical or horizontal gradiometer.

RTK DGPS compatible so topography data can also be collected.

Pros - Collects any where a human can go. Ideal for small survey areas

Cons - Slow even with a small array of 2 sensors. Lines ideally need to be “set out” and

very hard to check coverage on site.

Hand held magnetometer survey

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Pros- Increased coverage, More productivity, Real Time QC, Accurate positioning and safer

Cons- Not suited to small areas. Limited by terrain.

Combination of:

ArgoCat 8 wheeled ATV

Geomatrix’s GEEP survey platform

4 x G880 Caesium vapour magnetometers

CNAV 3050 Real time PPP

QPS QINSy

The “Land Ship” approach

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The Argo Cat ATV is an 8-wheeled, independent drive vehicle and has a fully marinised engine and drive system, which is steered by a simple push-pull braking lever system and a twist grip accelerator. The vehicle has a standard tow bar to pull sleds and carts.

Weight: 0.31 tonnes

Ground Pressure: 1.5-2.5psi

Max Gradient: 45 degrees

Speed: 20mph(Land), 2mph(Water)

Capacity: for 6 persons or 1 geo, driver and a shed load of kit!

Argo Cat

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Geophysically invisible tow sledge

Allows 4 G880 caesium vapour magnetometers at 1m spacing. Self concatenating

Interface box- containing a heading, pitch and roll sensor. Multiplexer

Kevlar reinforced tow cable carrying power and data back up.

DATEM- powers the GEEP systems via battery and de-coding

Controlling laptop running QPS QINSy

CNAV 3050 using C-Nav corrections real time PPP or Leica RTK receivers using Leica

Smart net.

Post processing the CNav 3050 data with PPK techniques can give a topo surface.

Geophysical Exploration Equipment Platform GEEP

Case Studies East Coast Pre lay cable landing UXO Survey

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Cable route landfall

Intertidal, beach and salt marsh terrain

High probability of UXO

Detailed magnetometer and topographic survey- 50m corridor along a route with

1m mag spacing. Requirements provided by a UXO consultant.

Surrogate trial required to prove methodology

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Surrogate trial required to prove methodology

Trial steel cylinders to represent suspected site UXO

Trial items buried to approx 30cm

Processing in Oasis Montaj

Items calculated position within ± 0.5m of recorded position

Surrogate Item trial

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Data processed using Geosoft Oasis Montaj – industry standard software

Navigation QC’d - Raw total field data de-spiked - removal of long wavelength component using Oasis’ non-linear filter

No need for diurnal corrections or base station data, Regional geological effects removed and short wavelength anomalies enhanced

Magnetic anomaly enhanced

21 A head scratcher!

• Suggestions ranged from processing artefacts to pipelines, fences, wires and even ancient field boundaries!

• Anomalies clear even in raw data – not artefact

• Anomalies discreet, not continuous – not fences/pipelines/wires

• Anomaly strengths of the order of 100-1000nT – too strong to be related to post holes/field boundaries

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Answer found through internet search!

Archaeological Research Services Ltd - North West Rapid Coastal Zone Assessment – undertaken for English Heritage2

“This block, with it’s [sic] lack of urban conurbations, contains very little archaeological evidence from the World Wars, although there were extensive anti-glider obstacles placed within [the local area] and mapped as part of the APM exercise for this project. These appear to have been long since swallowed by the shifting sands.”2

No clues from aerial photographs

Admiralty charts mention “numerous stakes”

Locals also mentioned poles

WW2 tank traps or other beach defences?

Interpretation

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Anti-glider defences as placed by German troops in France (1944)3

Remains of posts at Burntisland Bay, Scotland4

• Wooden stakes used extensively in WW2 as anti-glider traps

• Set in reinforced concrete

• Barbed wire strung between poles

Poles still in situ at Culbin Sands, Scotland1

Case Studies Normandie 3 Pre lay cable landing UXO Survey

25 Normandie 3 Cable UXO Survey

Since the failure of the Normandie 1 Cable in 2012 increasing amount of the electricity is needed to be produced on the islands of Jersey and Guernsey.

Normandie 3 will allow cheap electricity from France and in Guernsey's case increase its imported supply from 30%to 90%.

Normandie 3 is a 32km long HVDC cable from Armanville to Gorey

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Flat and sandy beach part of Rommel’s “Atlantik Wall”

Fast tides and creeks

4 hours of work

Cable route, barge set down, anchor locations

Armanville Plage, Normandie, France

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Ideal Conditions for the “Land Ship” method

Had to be careful with daylight and tide came in

fast!

Difference in springs and neaps

Not all areas of the site were accessible with the

GEEP

G858 data spliced in.

Day two and a local dog walker finds this!

A good reminder as to why this survey was

needed!

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Creeks!

Need for good communication with the boat team.

Land support Example of QINSy helm

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Same hard compacted sand.

The public and their four legged friends!

High likelihood of UXO

Gory Beach, Jersey

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WW2 German garrison beach defences

Thought to have been cleared.

Possible WW1 French artillery shell also found.

Beach data, Processed in the same as before also depths and weights calculated from AS grid

in Oasis Montaj

Mag survey in a compound?

The Gap Very Near Shore Marine UXO Surveys

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Geometrics G882 Marine Caesium Vapour Magnetometer – Industry Standard

Rapid sampling rate 10Hz

Very high sensitivity

Pros – Can be combined with an altimeter, light weight - can be towed from a RIB

Cons – Needs to be towed in water! Very sensitive needs to be kept 2-3 time boat length

Marine Magnetometer survey

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Acquired with G858 and G823 hand held sensors.

Coverage needed to meet with existing marine data

Required a boat survey in the surf zone

POSITIONING The most important factor of any marine geophysical survey.

5m water at the maximum.

To noisy and shallow for USBL. Too dynamic for GPS on a floating sled

Layback can work!

Kentish Flats Extension

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Expect Infill so reduce Line spacing!

Key to good layback navigation

Good communication between survey crew and the helm

Always go into the dominant current and try and get cross lines

RTK GPS with receiver as close to the TP as possible.

Use a navigation package like QINSy with heading and level inputs (accurate heights)

Lowest towing angle as possible

KISS we only used one fish to get the best position from it.

RIB towing a G882

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On this site there where close to 2000 mag anomalies

Side scan sonar data for the marine and topography and photos proved invaluable for

interpreting the site.

Beaches can be cluttered!

Not just Magnetometers

Survey Design What is needed and where

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Survey Design

Unlike most other types of marine survey UXO surveys need to be targeted.

Active as apposed to passive surveys.

What are you looking for?

What is the risk and who to?

What level or accuracy is needed?

These will all drive survey design!

Beaches can be dangerous!

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UXO consultants, clients and survey contractors can provide this information but it has to

be a two way street. GOOD COMUNICATION IS KEY

Client requirements:

Anchor locations, ship laid or man dug

Corridor width

UXO Threat:

Line Spacing and type of sensor

Survey/Environmental limitations:

Which techniques are needed to full fill the above. Can it be done safely with the type of

beach.

Survey Design

Client Requirements

Survey/Environmental Limitations

UXO Threat

Lessons Learnt Conclusions

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Always recce the beach

Walk the route if needed

Local knowledge – RNLI

What does the tide do can you be cut off?

Communication

NEVER WORK ON RISING TIDES!

Plan for the worst and hope for the best

Every beach is different!

The Future What’s next for near shore survey

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Hovercrafts

Legislation?

Weather restrictions high winds and line keeping?

Access?

Drones

Legislation?

Endurance?

Public preconception/safety?

Questions