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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.


News & Views

News Archive

December 7, 2016

Geosoft introduces IP and resistivity inversion in VOXI Earth Modelling

Geosoft has added induced polarization and resistivity data inversion to its VOXI Earth Modelling 3D inversion software service. Geoscientists are now able to create detailed 3D models of conductivity and chargeability from IP and resistivity survey data with VOXI. The resulting models can assist in interpreting and targeting regions for mineral and environmental applications...

December 5, 2016

Mexico's Deepwater Round Exceeds Expectations

Some of the world's biggest oil companies showed up Dec. 5 and agreed to invest on the Mexican side of the Gulf of Mexico, proving that deepwater exploration still has a pulse despite challenging market conditions...

November 30, 2016

Magnetic inversion results for Ngamiland available for download

A regional-scale geophysical inversion of magnetic field data in the Ngamiland region of northwestern Botswana is now available for download from the Botswana Geoscience Portal, a partnership initiative of the Botswana Geoscience Institute, industry sponsors and Geosoft...

November 30, 2016

LIGO Resumes Search for Gravitational Waves

After a series of upgrades, the twin detectors of LIGO, the Laser Interferometer Gravitational-wave Observatory, have turned back on and resumed their search for ripples in the fabric of space and time known as gravitational waves. LIGO transitioned from their engineering test runs to full science observations at 8 a.m. Pacific Standard Time on November 30...

November 9, 2016

International Volcano Scientists Unite

For the first time, the United States will host the international Volcano Observatory Best Practices workshop, previously held only in Italy. The workshop will take place this month in Vancouver, Washington. It is designed specifically for volcano observatories around the world and their staff to exchange ideas and best practices with each other...

October 4, 2016

USGS Assesses Mineral Potential for Sagebrush Habitats in Six Western States

USGS has completed a comprehensive assessment and inventory of potential mineral resources covering approximately 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah and Wyoming...

October 3, 2016

Uganda Targets Up to U.S.$100 Million for Mineral Exploration

Uganda is well endowed with mineral resources and, like many naturally-gifted African countries, is becoming keen on ensuring that these resources play a transformative role in its long-term structural transformation dream - the Vision 2040...

September 9, 2016

Small-Scale Fishers Get A Big Boost With First-Of-Its Kind Impact Investment Fund

Conservation organization Rare announces the Meloy Fund for Small-Scale Fisheries at Our Ocean Conference. The Global Environment Facility, one of the largest funders of conservation worldwide, will be investing $6 million into the fund...

September 1, 2016

Scientists take to the skies to track West African pollution

Scientists operating research aircraft over West Africa have detected organic materials in the atmosphere over a number of urban areas, contributing to concerns of the rise in pollution across the region...

August 17, 2016

New IGS Xplore prospectivity maps for Botswana

International Geoscience Services have released a series of base metal prospectivity maps for the Ngamiland District of northwestern Botswana using free geodata available on the recently-launched Botswana Geoscience Portal, hosted by Geosoft. The maps identify favorable areas for copper, zinc and lead mineralization using geological, geochemical and geophysical datasets downloaded directly from the portal.

August 11, 2016

NexGen Makes New High Grade Discovery

NexGen Energy reported the discovery of a new high grade zone of mineralization 4.7 km northeast of the Arrow Deposit as part of an on-going summer drilling program on its 100% owned, Rook I property, Athabasca Basin, Saskatchewan...

August 10, 2016

Rampion UXO Disposal to Take Place This Week

E.ON has confirmed that the two unexploded devices, detected along the Rampion offshore cable route will be safely disposed this week following the consultation with the Marine Management Organisation...

August 9, 2016

Diamonds In The Rough: E&Ps Find New Reserves In Mature Basins

The oil industry’s history demonstrates clearly that new plays and prospects have long been found in mature basins that were thought to be well on the way to being squeezed dry. Through the acquisition of new data, developing new concepts and coming up with fresh interpretations, long-producing basins around the world from the North Sea to Malaysia have continued to reveal new riches...

August 8, 2016

Northern Shield Identifies High Quality VTEM Targets at Séquoi

Northern Shield Resources announced the results of the interpretation and modelling of the VTEM survey from the Séquoi Property in the Labrador Trough of Quebec . Séquoi is owned 100% by Northern Shield and is being explored for Noril'sk style Ni-Cu-PGE massive sulphides. After geophysical modelling and interpretation of the VTEM data from Séquoi, six VTEM anomalies of significant interest have been identified...

August 3, 2016

Rio Tinto tailors big data drive to copper

Rio Tinto will put the weight of an exploration big data push and its newly-formed Growth and Innovation group behind its desire to identify a "tier 1" copper asset. Speaking at the annual Diggers & Dealers conference in Kalgoorlie, Growth and Innovation group executive Stephen McIntosh said Australia was "overdue for a tier 1" mineral discovery of any type...

August 1, 2016

Tetra Tech Awarded $200 Million Navy CLEAN Contract

Tetra Tech announced that it has been awarded a $200 million, single-award contract by Naval Facilities Engineering Command (NAVFAC) Atlantic. Through the Comprehensive Long-term Environmental Action Navy (CLEAN) contract, Tetra Tech will provide environmental engineering support services to installations within the NAVFAC Atlantic Area of Responsibility...

May 3, 2016

NATO Science for Peace and Security (SPS), MODUM Partners announce "Young Scientist Summer School on Sea Dumped Chemical Weapons"

This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...

April 12, 2016

Monday mad rush for gold stocks

Renewed optimism about the outlook for gold saw investors pile back into gold stocks, pushing many stock to 52-week highs in heavy volumes...

April 11, 2016

Medgold Resources: Continues to Expand the Boticas Gold Project, Portugal; Proposes $200,000 Private Placement

Medgold Resources is pleased to announce new assay results from contiguous rock-chip sampling from the Limarinho South zone at its Boticas gold project in Portugal, which include a highlight of 6.0m @ 5.7 g/t Au...

April 8, 2016

De-carbonizing our energy sector

Nuclear energy currently provides around 11 percent of the world's electricity. China, the European Union, the United States, India, Russia, South Korea, and other nations’ have major existing fleets...

April 1, 2016

Follow-Up Drilling Results Indicate Wide Gold Zones at Hendricks Gold Discovery

Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...

March 26, 2016

The Oil Market Is Finally Hitting Its Breaking Point

After a significant reduction in investments over the past two years, oil companies can no longer overcome the production declines from legacy wells...

March 15, 2016

N-Sea Expands into the French Offshore Wind Industry

Subsea IMR provider, N-Sea, has signed a letter of intent with CERES Recherches & Expertise Sous-Marine and TechSub Industrie Environement, to provide subsea survey, installation and remediation services to the French offshore wind industry...

March 9, 2016

PDAC 2016 Convention Exceeds 22,000 Attendees

Optimism and opportunity abounded at the PDAC 2016 Convention of The Prospectors & Developers Association of Canada in spite of recent industry challenges...

March 3, 2016

6 Alpha Launches EOD Contracting Division

6 Alpha Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...

Geophysics in Urban Brownfields


Virginia Heffernan

If ever there was a candidate for accurate site characterization, the contaminated parcel of land that will host the London Olympics in 2012 is it. Lurking below the site's surface is a mix of unexploded bombs, radioactive waste and industrial toxins that pose serious obstacles to redevelopment.

Selected for its proximity to central London and good access to transport, the 500-acre site in the Lower Lea Valley of East London has been the centre of industrial activity for years. Aside from the resulting industrial contamination, the site could contain as many as 200 bombs that failed to detonate during the Second World War as well as radioactive nuclear waste dumped there in the 1950s.

As a result, the subsurface will need to be carefully remediated to the tune of £1.7 billion before construction of an urban park – the largest to be built in Europe in the last 150 years – begins.

But although the Olympic Delivery Authority is already preparing the site for remediation, the British Geological Survey (BGS) says the subsurface should be thoroughly investigated first to prevent expensive, potentially dangerous and/or environmentally damaging mistakes. The characterization would not only help Olympic planners, but would direct future development in the surrounding area, one of the many brownfields slated for regeneration worldwide as the trend towards urbanization continues apace.

"Investment now in the management of geo-information and the development of 3D geological models of the shallow subsurface will provide benefits not only to the development of the Olympics but for the development of the whole of the Thames Gateway for decades to come," say researchers from the BGS in a recent issue of Geoscientist.

While the BGS is mainly concerned with geology, geophysical techniques routine in mineral exploration could be used to detect both natural and manmade features beneath the surface of the Olympic site. The properties of density, elasticity, magnetic susceptibility, electrical conductivity, and radioactivity that identify mineral deposits can also provide a snapshot of the urban subsurface including dangers such as unexploded ordnances and nuclear waste, sources of contamination, or remnants of earlier structures that could cause engineering challenges.

Rapid advances in 3D modelling software allow these properties to be displayed in a meaningful way to non-geophysicists involved in regenerating and developing urban brownfields, allowing them to pinpoint problems and target their remediation accordingly.

Yet, civil engineers continue to rely on much more expensive, and potentially more disruptive, borehole drilling to characterize brownfield sites, even though problem areas between drill holes are often missed using a conventional grid pattern.

"I've waged a 20-year campaign to try and convince engineers not to reach for the drill, because drilling can be like trying to find a needle in a haystack, says Peter Styles, Professor of Applied and Environmental Geophysics and Geography at Keele University in the United Kingdom. "But engineering is driven by litigation in this country, and it is defensible in court to investigate using drilling on a grid. So that is the conventional technique, even if it is not always the best technique."

Styles points out that even if geophysics cannot replace drilling for legal reasons, it should at least be used to target the drilling so that discrete hazards, such as hidden cavities, are not missed and exposure to toxic chemicals is minimized. The survey findings can also help compliance with environmental legislation surrounding clean-up of contaminated sites. And detect those unexploded bombs without setting them off.

For example, Zetica, a London-based site characterization firm consulting on the Olympic site, used non-invasive geophysical techniques to identify the source and pathway of serious contamination below the site of a major car park development in central England. Previous drilling had failed to detect the contamination, but within half a day, Zetica had identified a sump containing volatile waste as the source, and a concrete culvert as the pathway. The culvert was closed and the sump removed before redevelopment got underway.

Styles says the choice of geophysical technique is site dependant. If information about the subsurface is scanty, a first pass with electrical resistivity to detect contamination and find the water table, gravity to detect cavities or underground storage tanks, or ground-penetrating radar (GPR) to detect buried pipelines, power lines, and even hazardous liquid wastes is advisable.

"You have to have a first good guess at where these objects are before you use more sophisticated techniques," he says. "Techniques like electrical resistivity, gravity and GPR have been really useful tools for homing in on areas."

Often investigators will use a combination of methods to reflect the complex nature of the urban subsurface: electromagnetic techniques to detect changes in conductivity and find fault zones; spectral IP to trace hydrocarbon contamination; magnetic profiling to detect buried ferrous objects such as unexploded ordnance and archaeological artefacts; radiometric measurements to locate faults or caves or to map contamination; and seismics to characterize fill material.

Increasingly, geophysicists are combining not only technique but interpretation. For instance, Styles might mix gravity data with electrical data and view them in a mathematically integrated way to detect contamination within an underground cavity. Advancements in GIS and 3D modelling facilitate this integration by providing a means to visualize several different types of data at once. Styles says time domain techniques are also becoming more popular as urban planners recognize the importance of not only detecting contamination and other obstacles to brownfield development, but monitoring those hazards as they change over time: migration of contamination, for instance, or the expansion of an underground cavity towards the surface.

Applying geophysical techniques traditionally used for oil and mineral exploration to the urban environment is more advanced in Europe and the UK, where land shortages are more acute than in North America.

"In the UK, we're running out of space," says Styles. "We've been through our industrial cycle and we are starting to dismantle our gas works, our chemical works, and our factories and rebuild on top of them. Almost all land which becomes available for building in the UK has a previous industrial history."

But the practice is starting to catch on in North America, where more and more people are gravitating to urban centres. In Canada, the number of people living in metropolitan areas jumped by 45% between 1971 and 2001, more than three times the rate of growth of rural areas.

Brownfields are providing the space to house these new urban dwellers, while geophysical techniques are helping to detect unexpected surprises below the surface, prevent project delays, and allow better estimates of remediation costs.

A purchaser who wanted to redevelop a parking lot in an unspecified downtown core, for instance, was able to calculate the cost of removing contaminated soil from the site, and therefore adjust the purchase price, by using a combination of electromagnetics, resistivity and test pits to characterize the subsurface, according to Mundell Associates, an environmental consulting firm based in Indianapolis, IN. At another Mundell project, cost estimates for waste removal from a brownfield redevelopment dropped from US$1 million to US$550,000 after the company completed geophysical surveys over the site. Final removal numbers were within 5% of the revised bid.

However, using geophysics in the urban environment is challenging because the anomalies are often subtle while the surrounding clutter is loud. Overhead power lines, rebar in concrete, electrical lines in buildings and electrical currents can interfere with measurements.

To minimize the effects of this "cultural noise", researchers at a brownfield site in East Chicago concluded that line and station spacings should be one foot or less, instruments should run in orthoganal directions, and a combination of methods should be used. But more work is needed at the data interpretation stage to weed out these distractions.

"My vision is to be able to take a model of the city and do all the corrections for it so that we can remove those effects from what we want to look at," says Styles.

Reference

Holt, J., Daniels, J., Vendl, M., Baumgartner, F., and Radziviscius, S (1998). Brownfield Site Investigation Using Geophysics: A Case History from East Chicago. In Proceedings: SAGEEP 1998 Environmental and Engineering Geophysical Society.

Mundell, J. A., and Buyer, G. B. (2002), Geophysical Characterization of Brownfield Sites for Better Development Evaluation and Construction Planning. In Proceedings: SAGEEP 2002. Environmental and Engineering Geophysical Society.

Royse K., Entwisle D., Price S., Terrington R. and Jo Venus (2006). Gateway to Olympic Success. Geoscientist 16 (5)

Styles, P. (2003) Environmental geophysics: a site characterization tool for urban regeneration in the post-mining era Geology Today 19 (5).