Archives: Case Studies

LOCATION:   Swavesey, Cambs

PROJECT TYPE:   Geoenvironmental investigation

VALUE:   £13K

BACKGROUND

Land developers, as part of their due diligence, need to check, before construction commences, for the presence of ground gas such as methane and carbon dioxide, which can be hazardous to human health.

Bloor Homes commissioned Harrison Group to carry out such an investigation and report the findings on a 4.7ha agricultural site in Swavesey, near Cambridge. The site was earmarked for mixed-use residential development of 99 homes.

The results would be used in the design of roads and sewers, foundations, pavement construction and to conclude if any remediation measures would be required.

SCOPE OF WORK

Phase 1 Assessment (Desk Study) to produce a hazard assessment and conceptual ground model.

Phase 2 Investigation (Intrusive) to include:

• Soil sampling and standard penetration testing using a dynamic continuous sampling dual-purpose rig
• Machine-excavated trial pits with infiltration testing
• CBR testing
• Return visits for ground gas and flow monitoring
• Physical soil analysis to UKAS mCERTS standards
• Chemical analysis, general suite to include TPH, PAH and asbestos screening
• Interpretative report

Follow-on investigation for further ground characterisation:

• Continuous sampling boreholes with ground gas monitoring
• Detailed quantitative risk assessment with conceptual ground model, incorporating geology, potential ground gas sources & migration and exposure pathways

OUTCOME

Initial results indicated elevated levels of carbon dioxide and carbon monoxide, coupled with a high flow rate, requiring gas protection measures – subfloor venting and gas membranes.

Harrison Group recommended additional monitoring to assess the ground gas risk. Further characterisation of the ground would reduce overall construction risk, with the potential for reducing development costs. By combining the site model with proposed construction details and estimating ground gas equilibrium concentrations in the sub slab void, the ground gas risk was shown to be lower than originally envisaged. As a result of this, Bloor Homes was able to use the original design of precast concrete beam and block floors being in the construction.

There was no requirement for any further gas protection measures, saving considerable time and costs during construction.

 

LOCATION:   Preston

PROJECT TYPE:   Geotechnical site investigation

VALUE:   £150K

BACKGROUND

Whittingham Hospital, near Preston in Lancashire, treated thousands of psychiatric patients every year and had its own railway, brewery and sewage works.

The main hospital closed in 1995, and following several unsuccessful attempts to promote development, the site was purchased by Homes England in 2005.

A Tibbalds Campbell Reith JV was appointed by Homes England in December 2017 to develop a new masterplan for the site; the current proposal is for 750 homes to be built in four phases.

Harrison Group was awarded the ground investigation contract by the Tibbalds Campbell Reith JV in order to assess ground conditions and contamination risk beneath demolished buildings and parts of the site deemed to present potential risk, that had been identified during previous investigations. These included historic landfills, areas of soft ground and asbestos containing material from the hospital buildings.

SCOPE OF WORK

Harrison Group acted as the Principal Contractor for the ground investigation works, which due to the size of the site included over 200 exploratory locations.

Investigations included almost 50 boreholes, drilled using cable percussive and dynamic continuous sampling methods, in excess of 150 machine and hand-excavated trial pits, extensive sampling and in-situ testing and installation of monitoring wells.

Post-intrusive works included comprehensive gas and groundwater sampling, chemical and geotechnical testing and the production of a GIR.

Data Management

In addition to the large quantity of data collected through the investigation, the company were also asked to convert historic investigation records and reports into AGS format, to allow production of a more detailed ground model and to enhance data assessment.

The historic data included an additional 200 exploratory locations across 4 different investigation phases. The data also included over 10000 chemical analysis results and numerous geotechnical test reports in paper format, which were digitised and converted to AGS data format.

The large volume of data created, enabled us to compile detailed 3D models of the geology, contaminants and geotechnical properties, using our award-winning data management team.

OUTCOME

All site work, testing and reporting was carried out on time and to the satisfaction of the client.

LOCATION:   Great Blakenham, Suffolk

PROJECT TYPE:   Geotechnical site investigation

VALUE:   £45K

BACKGROUND

SnOasis is a proposed indoor winter sports resort, a project that will be unique in the UK.

Location of SnOasis is the 123ha former chalk quarry, near Great Blakenham in Suffolk.

The plans include:

• Indoor snow facility with a 74m high ski-slope – one of the largest in the world
• Bobsleigh run, ice wall and other leisure facilities
• Hotel, ski lodges and apartments
• New homes with a new railway station on the Norwich to Ipswich line

Harrison Group was commissioned to carry out a ground investigation, in order to gather information on groundwater levels and soil permeability across the five different geological formations present.

The results of this would enable consultant BuroHappold Engineering to carry out a flood risk assessment and drainage design for the commercial element of the proposed development.

SCOPE OF WORK

Fieldwork was carried out over just nine days and comprised:

• Two cable percussive drilling crews, completing 10 cable percussive boreholes to depths of up to 20m, with the installation of monitoring standpipes
• Two pitting crews completing 41 machine-excavated, gravel-filled BRE365 soakaway tests up to 2.6m depth
• Post-fieldwork groundwater level monitoring using in-situ dataloggers

Soakaway tests were completed with 3 infillings, or left over 24 hours at locations where infiltration was poor. Datalogging equipment was used for tests in remote areas of the site.

Work was carried out during the winter months when the ground surface was particularly soft, and, in places, impossible to traverse with 4×4 vehicles. As a result, specialist equipment was used to move the drilling rigs and transport materials to the required locations.

OUTCOME

Fieldwork data was provided to the engineer within a day of fieldwork completion and the factual report provided to the client/engineer within two weeks.

David Palmer from BuroHappold Engineering said, “We have been delighted with the support we have received from Harrison Group and grateful for the timely release of the report”.

LOCATION:   Newmarket, Suffolk

PROJECT TYPE:   Geotechnical site investigation and UXO survey

VALUE:   £12K

BACKGROUND

Peter O’Sullevan House, on the site of the British Racing School in Newmarket, houses state-of-the-art rehabilitation and fitness facilities for injured jockeys.

Built by the Injured Jockeys Fund, the centre has treatment rooms, hydrotherapy pool and a gym; meeting and educational facilities for British Racing School students; a multi media and communications room and also serves as the Fund’s head office. Construction of the centre was completed in 2018 by contractor RG Carter at a cost of about £6m.

SCOPE OF WORK

Harrison Group Environmental was commissioned to carry out a desk study and geotechnical investigation to provide engineering data for construction of the new centre.

The desk study confirmed the site was within the perimeter of the World War Two RAF Snailwell airbase, which meant there was a risk of unexploded ordnance [UXO] being present. As a result, magnetometer scanning was carried out at investigation locations before work began, to ensure each was clear of UXO.

The ground investigation comprised:
Four dynamic continuous sampler boreholes
Three trial pits with soakaway testing (BRE DG 365, 2016)
Seven insitu CBRs
Geotechnical testing at Harrison’s in-house laboratory.

Environmental testing was undertaken at an accredited chemical laboratory and, following completion of the main investigation, ground gas concentration/flow monitoring was carried out.

Although UXO was not encountered during the investigation, Harrison advised the client that further work would be required to fully mitigate the risk before the site could be developed. So, after the main investigation was completed, Harrison worked with explosive ordnance contamination specialist MACC International to complete a full magnetometer survey of the development area.

OUTCOME

The geotechnical investigation was completed safely and, while the UXO survey identified 137 buried ferrous objects, all of these turned out to be scrap metal that had been buried when the airbase was demolished.

The survey also identified the presence of a backfilled Stanton air raid shelter in the centre of the site. However, as this obstacle was identified in the early stages of the project, any unexpected design changes or delays during construction were avoided.

Results of the investigation enabled the client to proceed with construction, with a focused package of geotechnical data to inform the final foundation designs, without the risk of encountering buried explosives.

LOCATION:   Trinity College, Cambridge

PROJECT TYPE:   Geotechnical site investigation

VALUE:   £2,000

BACKGROUND

As part of the activities to mark the 700th anniversary of the early origins of Trinity College, a striking sculpture by Sir Antony Gormley OBE has been installed on the historic Backs at Trinity College, opposite the Wren Library and near the edge of the River Cam.

Antony Gormley has links with the college, having read History of Art there between 1968 and 1971. His best known works include the Angel of the North, Another Place on Crosby Beach, Liverpool and Event Horizon at the UEA in Norwich.

The work at Trinity College – Free Object – is part of the sculptor’s ‘Blockwork’ series. It is 5.5m in height, and being constructed from spheroidal graphite iron, weighs 11.2 tonnes. The sculpture is bolted to a concrete base and will remain on loan to Trinity College for 12 months.

Trinity College needed to carry out a ground investigation at the location in order to design the foundation for the installation.

SCOPE OF WORK

The site is very sensitive – this was the first time that permission had been given to dig on the Backs – and it was a requirement to leave the site in a pristine condition on completion. As an additional element of the investigation bearing in mind the ancient nature of the site, the ground investigation team was accompanied by two archaeologists from the University of Cambridge.

The study comprised sinking a number of Dynamic Continuous Sampling boreholes, testing samples from the boreholes in the company’s UKAS accredited laboratory and producing a report on the findings with recommendations for appropriate foundations.

OUTCOME

The investigation revealed that ground conditions comprised 1.5m of made ground over very soft cohesive alluvium to a depth of 4.8m. As a result of the presence of weak subsoils, the original shallow pad foundation design would have been inadequate to support the required bearing capacity of 25kN/m2, with the additional prospect of wind-loading giving rise to the risk of differential settlement. Instead, the use of small diameter displacement piles was recommended, end bearing in the river terrace deposits below 5m.

All work was carried out to the satisfaction of Trinity College and the sculpture has now been installed.

Tim Waters, Capital Projects Manager at Trinity College:

‘I was very pleased with the service received from the Harrison Group. Important factors when procuring services from our sub-contractors for successful projects are reliability, communication, value for money and service delivery. The Harrison Group delivered on all accounts. Happy to work with them and continue our relationship into the future.’

 

LOCATION:   Thessaly Panagia, Greece

PROJECT TYPE:   Ground investigation

VALUE:   £290K

BACKGROUND

Between 2003 and 2005 Harrison Group Environmental carried out geotechnical investigation work on the Egnatia Odos project which is one of the largest road projects ever constructed in Europe.

It has been integrated into the priority projects of Trans-European Transport Networks (TEN-T). The 670 km long motorway crosses Northern Greece, connects most of its major urban centres, links 4 major harbours and 6 airports.

Over 25 Industrial Areas / Parks &developmental zones are located within a radius of 5km on either side of the Egnatia Motorway and each of its vertical axes.

Harrison had to be registered by the Greek government to undertake projects of Degree E, a level given only to the highest profile projects.

Tunnels

Construction of a number of long tunnels was required so that the Egnatia Motorway could negotiate the more hilly & mountainous areas along its route.

The longest was the Epirus Dodoni tunnel at 4.59km. Harrison Group carried out the investigation for the Thessaly Panagia tunnel – length 2.7km.

SCOPE OF WORK

A number of rotary holes were drilled along the proposed Panagia tunnel route to depths of up to 120m.

The findings were used for highway, bridge and tunnel design.

Initially the route of the site investigation was forested and this had to be cleared to open up access for lorry mounted rotary drilling rigs and other essential plant and equipment.

OUTCOME

All work was carried out within allowed timeframes and to the satisfaction of the client.

LOCATION:   Great Yarmouth

PROJECT TYPE:   Ground investigation – flood defences

VALUE:   £140K

BACKGROUND

Great Yarmouth has a history of devastating floods, with major events in 1953 and most recently in 2013. Flood defences have been upgraded on a number of occasions, with the most recent scheme completed in early 2016.

This £28.6M Environment Agency project aimed to protect more than 2,000 homes and businesses, upgrading sea defences in Great Yarmouth harbour by refurbishing and raising quay walls along the River Yare. Harrison Group Environmental, working for contractor BAM Nuttall, carried out the ground investigation for design of new sheet pile walls and 94 permanent Single Bore Multiple Anchor (SBMA) ground anchors (installed by Keller Geotechnique) to support raised quay walls.

Ground conditions comprised 20m of unconsolidated made ground, deep organic soils and very soft clay over medium dense to dense sand. The SBMA anchors were some of the longest ever installed in the UK, at up to 62m long, allowing them to be founded in the sand, as the soft material above could not provide sufficient bonding capacity.

Harrison Group used its extensive experience of working in Great Yarmouth’s challenging ground conditions, to design an investigation that would gather the high quality data essential to ensure the anchors could meet the high axial loads required to support the quay walls.

SCOPE OF WORK

The ground investigation began in 2014 and comprised 16no., 40m deep, cable percussive boreholes to provide data for the anchor and sheet pile wall design. Harrison Group also carried out plate bearing tests and a Ground Penetrating Radar (GPR) survey to confirm the ground could support loads from heavy construction plant. Shear vane tests and piston sampling were carried out in the boreholes to depths of 21m, along with standard SPTs and sampling to 40m. Geotechnical testing was carried out by Harrison Group’s in-house laboratory in Norwich.

The site has a long industrial history, so stringent environmental protection was put in place during the investigation. This meant that drilling had to be ‘clean’, with environmental seals used between drill strings to prevent cross-contamination between strata. Work was carried out in bunded areas with borehole arisings and groundwater stored and tested before being sent for disposal off-site.

The GPR survey was used to identify any shallow voids beneath the quayside that could present a hazard to machinery tracking over the area during construction. Plate Bearing Testing confirmed appropriate CBR values had been achieved by the compaction of loose and soft quayside material before construction began.

OUTCOME

The ground investigation was completed safely, within the programme and to budget, to the satisfaction of the client. In recognition of the professionalism of their work on site and follow-on reporting, the client commented.

“Harrison’s expertise, combined with its experience of Great Yarmouth’s challenging ground conditions, ensured the investigation delivered the best possible data for the design of both the temporary and permanent works.”

LOCATION:   Various – eastern Scotland

PROJECT TYPE:   Geotechnical site investigation

VALUE:   £30K

BACKGROUND

About 40% of Scotland’s electricity demand is currently met by renewable sources and by 2020, the Scottish Government wants this to be 100%.

 

Solar power is seen as a key part of the renewable mix but accounts for just 2% of energy generation, with the focus having been on onshore wind in recent years. As a result (and with technology becoming cheaper), the solar power market looks set to grow dramatically in the near future.

 

This change of focus is attracting interest from global investors, developers and operators of solar farms. Eastern Scotland, in particular, is seen as a key area for solar energy generation. Aberdeenshire, Angus, Fife, Perth and Kinross receive similar levels of sunshine to countries such as Denmark and Germany, which are already well-served by solar power.

 

Harrison Group Environmental carried out geotechnical investigations as part of site appraisals for six solar farm sites in eastern Scotland for two major UK solar energy providers – Lark Energy and Geometris – in Summer 2016.

 

Working to tight timescales – all six investigations were carried out in two weeks to meet planning deadlines – Harrison mobilised a team of engineers from its Norwich and Cambridge offices to carry out the work.

 

SCOPE OF WORK

Each investigation included a desk study to identify potential geotechnical hazards, and to develop site-specific intrusive investigations. Along with gathering ground condition data, buried structures were investigated using geophysical techniques.

 

Fieldwork included dynamic continuous (window) sampling, in situ testing and trial pitting, with soil and rock samples tested at Harrison’s in-house UKAS accredited laboratory in Norwich. Testing was used to classify soil and rock and to determine key geotechnical parameters.

 

Harrison Group provided recommendations for shallow and deep foundations for the solar arrays and ancillary buildings and for access road pavements. It also helped meet requests for information from local authorities, as part of the planning process.

 

OUTCOME

Engaging Harrison Group to manage and carry out all six site investigations meant mobilisation was faster and costs were cut by 15%. Communications were also far simpler, as Harrison assigned one project manager to act as a single point of contact.

 

Harrison Group ensured investigation results were delivered in time for key planning documents to be submitted and produced preliminary results (borehole logs, in-situ testing, ground conditions and foundation recommendations) ahead of final reporting, to speed up site assessments.

 

Client quotes

 

“Having Harrison Group manage all six sites meant the entire investigation process was faster, simpler and more cost-effective, giving us more time to appraise the sites and to develop cost projections.”
Emma Rafaluk, Land and Development Director, Lark Energy

 

“Harrison Group has been a reliable partner over the past two years. The company’s engineers cope well with the fast-paced nature of the solar industry and having one project manager for all six projects proved to be very effective, helping to avoid communications issues.”
Alexandros Katsakos, Project Manager, Geometris

 

LOCATION:   Stratford – London

PROJECT TYPE:   Contaminated land investigation

VALUE:   £3.75M

BACKGROUND

HARRISON GROUP ENVIRONMENTAL was appointed as one of three companies to carry out the geotechnical ground investigation on approximately 70No. sites across the Olympic Park area . We were the first site investigation company on the project to break ground in December 2005, with a cable percussive drilling rig on Hackney allotments.

SCOPE OF WORK

By working closely with the client, we were able to successfully overcome a number of challenges in order to meet the deadlines set. These involved:

• Unexpected ground conditions
• Liasing with landowners and occupiers
• Access difficulties
• Scheduling fieldworks to cause least disruption to breeding kingfishers

Intrusive work across the Olympic Park area included:

• Borehole drilling with cable percussive rigs
• Machine dug trial pits
• Borehole drilling with hollow stem auger rigs
• Small diameter boreholes using window sampling rigs

Standard soil sampling regimes were followed and in addition to this, piston sampling and continuous undisturbed samples – U100’s – were incorporated into the works.

In addition to the drilling crews, we also had a dedicated team on site to carry out continuous gas and water monitoring, permeability testing and in-situ water quality testing.

Environmental Considerations

There was the potential for a wide range of contaminants across the Olympic Park area. As a result of this, we assumed at the time, that all sites on this project would be category ‘RED’ for ground investigation purposes, and that the specific PPE and welfare/decontamination facilities associated with this were made available on site. More specifically this meant that:

• Drillers and engineers go through decontamination procedures each time they left site and used clean gloves for all sampling procedures
• Clean method techniques were applied to all drilling operations, drilling initially with 250mm diameter casing, with reductions in diameter at the base of made ground and again at the base of the river terrace deposits. In order to prevent cross-contamination a 2.0m bentonite seal was placed at each reduction
• Rigs were checked daily and audited weekly and all tools cleaned between borehole positions. A gas alarm was located at every drilling rig, with both engineer and driller being trained in its use. A head space test using a PID was also carried out on every sample
• All site staff had available personal, universal fitted vapour masks as part of their standard PPE
• Occasional monitoring for radiation was required

Health and Safety

This was a high profile project for the industry and presented an opportunity to fine tune the health and safety standards for industry drilling operations. As a result of working closely with the HSE we successfully took on board new recommendations to enhance the safety of drilling crews on site. We also commissioned an in-depth assessment of manual handling issues on behalf of the Olympic Delivery Authority, which has been reviewed by the HSE.

OUTCOME

We are proud to report that we had zero reportable incidents in over 1400 drilling, monitoring and surveying days on the Olympic Park Site. All work was completed in the timescales that were set and to the satisfaction of the clients that we were working for.

LOCATION:   Stratford

PROJECT TYPE:   Ground investigation – red site

VALUE:   £260K

BACKGROUND

Redevelopment plans for this 10 hectare site located in Stratford, East London, include for open streets with new shops, cafés, hotels, over 1,200 residential units and 58,000m2 of commercial office/business space. The site has had a long and diversified industrial history, resulting in a legacy of known and unknown areas of ground and groundwater contamination.

SCOPE OF WORK

Harrison Group were instructed to undertake the ground investigation to provide geotechnical and environmental information to aid in design of the development. Ground investigation works included:

Trial pits
Cable percussive boreholes

Dynamic continuous sampling boreholes
Static cone penetration testing
Sampling
In-situ testing

Installation of multilevel groundwater and ground gas monitoring wells
Subsequent rounds of low-flow groundwater sampling and monitoring

Working closely with the demolition contactor, Harrison Group installed in excess of 50nr. cable percussive boreholes to depths of up to 35mbgl, the majority having single or nested monitoring wells installed to allow for comprehensive monitoring of ground gas and groundwater. Almost every geological unit that can be found in the London area was encountered at the site, the near surface geology of which has been complicated by deep areas of made ground associated with relic dock features and naturally by river channels cutting through the solid geology.

Prior to breaking ground, service location was undertaken and UXO clearance using downhole and CPT push magnetometers was undertaken due to the risk of encountering unexploded ordnance.

High levels of contamination were encountered during the investigation which resulted in the site being re-designated as ‘RED’, with a short pause in the works during which decontamination units were mobilised and working practices and PPE levels modified accordingly to ensure contained safe working for all site users. Hydrocarbon contamination within the ground needed to be better defined and the CPT rig utilising a membrane interface probe (MIP cone) was used to determine the extent of the hydrocarbon plume within the ground.

OUTCOME

Careful planning and consideration of existing site users was essential to reduce the impact on residents and ensure full utilisation of all of the teams working on the site. This resulted in weekend and unsocial hours working, the investigation being undertaken 7 days a week for part of the programme, which was completed to the satisfaction of our client and within the allocated timeframe.