Archives: Case Studies

Harrison Group case studies

Norwich Castle Keep Restoration


 

Norwich Castle Keep Restoration

LOCATION:   Norwich

PROJECT TYPE:   Geotechnical site investigation

VALUE:   £15K

BACKGROUND

Harrison Group was contracted by Morgan Sindall to carry out several phases of site investigation work at Norwich Castle during 2020 and 2021.

The work was part of the ambitious project to restore the castle keep back to the original layout that existed in the 12th century.

As the proposed alterations to the building’s structure would increase loadings on internal walls and foundations, the investigations were required to provide ground information to aid pile design, give clearance to proceed at a number of proposed piling locations and for the safe construction of temporary works.

Previous site investigation at Norwich castle had identified granular made-ground with cohesive bands up to 10m depth, forming the structure of the castle mound. Also, a Saxon burial site may have been encountered, with historical investigation findings revealing the presence of bone fragments at around 8.5m depth. Underlying this, sand and gravel of the Crag Group and Norwich Chalk had been encountered.

SCOPE OF WORK

For this current phase of work, a number of investigative techniques were employed, including: –

  • Cable percussive borehole (electric-powered low-headroom rig), depth 25m
  • Dynamic Continuous Sampling (DCS) boreholes
  • Dynamic Probe Testing (DPT)
  • Plate Bearing Testing (PBT), completed within the Castle Meadow area of the site in order to provide information for construction of a temporary crane base
  • In-situ California Bearing Ratio tests for temporary works
  • Archaeologists worked alongside Harrison Group as they were required to pre-dig the drilling locations, in order to check for artefacts, prior to the intrusive works being undertaken.

    Due to the large quantity of made-ground encountered, which is inherently variable, geotechnical laboratory testing was considered of limited use in yielding meaningful results.

    However, potential reaction of the soil with buried concrete was a consideration, and soil samples were sent to a UKAS/MCERTS accredited laboratory for testing.

    Pile installation was programmed as part of the development works, to be undertaken (by others) around the castle keep. To assist with this, Harrison Group provided factual data as their works progressed, to allow the piling contractor to assess the suitability of anticipated piling locations and as an aid to their pile design before mobilising to site.

    OUTCOME

    All site operations were carried out successfully whilst respecting COVID-19 rules.

    Harrison Group was also flexible with the site works and liaised closely with Morgan Sindall to prioritise their needs, completing the work on time and within budget.

    Setting up low-headroom drilling rig

     

    DPT rig setup

     

    CBR testing

     

    Happisburgh


     

    Happisburgh

    LOCATION:   Happisburgh, Norfolk

    PROJECT TYPE:   Geotechnical site investigation

    VALUE:   £100K

    BACKGROUND

    Harrison Group was contracted by Vattenfall to undertake a site investigation over a section of Happisburgh beach to provide information on ground conditions for the design of the cable landfall for the Norfolk Vanguard and Norfolk Boreas offshore windfarms. These sites will have a combined generating capacity of 3.6 GW, providing the equivalent electricity needs of 3.9 million UK homes per year.

    SCOPE OF WORK

    The site comprised a part of Happisburgh beach situated below a cliff section which was inaccessible to road vehicles without extensive enabling works. It was therefore decided to access the site by sea, utilising a landing craft to transport all plant, equipment and materials onto the beach. The timing of the site work was chosen specifically to coincide with neap tides (when the tidal range is the smallest), so the fieldworks did not run the risk of inundation by the sea.

    MTS Group Limited provided the landing craft MTS Terramere to transport the plant and equipment from the Port of Lowestoft directly to Happisburgh beach. Equipment was then transported between the vessel and the worksite by tracked plant.

    A UXO supervisor was present onsite to verify that the work area was clear of shallow buried ordnance prior to setting up drilling and testing equipment. A paleoarchaeologist was also present to ensure that the fieldworks did not disturb potential archaeological artefacts.

    The site works comprised drilling a single cable percussive borehole and undertaking five cone penetration tests across the proposed cable route. The cable percussive borehole was advanced to a depth of 21.5m utilising specialist tooling and several casing diameters – reduced through bentonite seals – to minimise the effect of ‘blowing sand’ conditions.

    Closely spaced sampling and in-situ testing was undertaken throughout the borehole and the soils were logged onsite by both a senior geotechnical engineer and the paleoarchaeologist. Cone penetration testing was undertaken to depths of between 8.5m and 15.7m, using a 15-tonne capacity hydraulic ram set mounted on a tracked unit.

    Upon completion of the works, all plant and equipment was removed from the beach by the landing craft and the area was reinstated to an ‘as found’ condition.
    Samples recovered from the borehole were transported back to the company’s laboratory for subsequent testing with results included in the ground investigation report.

    OUTCOME

    Despite the unusal challenge of mobilising to and from a site with restricted access, Harrison’s innovative and proactive approach allowed these works to be completed safely and successfully, on time, with due care to minimise inconvenience to other beach-users and to Vattenfall’s satisfaction.

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    Mobilising to site

     

    Drilling compound

     

    Typical Vattenfall wind turbines

     

    Site set up across Happisburgh beach

     

    ExCel Exhibition Centre, London

     

    ExCel Exhibition Centre, London

    LOCATION:   ExCel Exhibition Centre, London

    PROJECT TYPE:   Geoenvironmental Ground Investigation

    VALUE:   £100K

    BACKGROUND

    The site investigation took place in the eastern car park of ExCel Exhibition Centre in order to provide information on ground conditions to inform foundation design, contamination assessments, and any remedial measurements required for the construction of a two-storey, 40,000m2 extension.

     

    The site was immediately adjacent to the Royal Victoria Dock, and had an extensive industrial history with multiple historical foundations. It also had a very high UXO risk, with more than 8 bomb strikes recorded as having occurred on-site and a further 5 within 25m.

     

    The geology consisted of made ground over superficial deposits including cohesive and granular soils and peat overlaying Lambeth Group deposits.

     

    At the time of the investigation, Covid-19 restrictions were in place and the ExCel Centre was host to a Nightingale Hospital.

    SCOPE OF WORK

    OUTCOME

    No items found

    Great Yarmouth, Third River Crossing


     

    Great Yarmouth, Third River Crossing

    LOCATION:   Great Yarmouth, Norfolk

    PROJECT TYPE:   Supplemental site investigation, risk and waste assessments

    VALUE:   £40K

    BACKGROUND

    The proposed Great Yarmouth Third River Crossing scheme will provide an additional route over the River Yare. This will involve the construction, operation and maintenance of a new bascule bridge.

    It will provide a connection between the strategic road network (A47) and the businesses and commercial parks located on the South Denes Peninsula

    In order to gain a Development Consent Order the Planning Inspectorate is required to submit a report and recommendations to the Secretary of State.

    As part of this, Harrison Group were employed to carry out a supplemental site investigation, risk assessment, and waste assessment interpretative report for environmental data, in addition to a wider geotechnical site investigation.

    SCOPE OF WORK

    The interpretative report builds combines the information gathered from a number of different documents.

    These are prepared as part of the Environmental Statement and other design documents regarding site history and land use, groundwater and soil testing, baseline geology and hydrogeology, designation of stratigraphy and water bearing units, critical receptors, and Conceptual Model and Detailed Quantitative Risk Assessment (DQRA).

    The specific tasks completed were:

  • Compilation, integration, and summarisation of historical borehole and chemistry data into a quality controlled georeferenced electronic data set
  • Gap Analysis
  • Supplemental data collection
  • Spatial analysis – data overlayed with historical and proposed land use, site zoning, spatial coverage, initial screening values, traffic light plots
  • Traffic light plot – benzo-a-pyrene in groundwater
  • Statistical analysis – normal probability plots, statistical summaries, assessment of probability distribution, outliers and hot-spots
  • Waste assessment and management based on WM3 waste classification, WAC analysis, and potential for pyritic soils.
  • Once completed Harrison Group were able to:

  • Produce an updated and integrated risk assessment report based on data from all site investigation phases.This reviewed and updated site conditions, development plans, and engineering design and implementation
  • Identify hot-spots and baseline environmental chemistry of different geological units and materials
  • Classify waste and assess re-use and potential material management as per the waste hierarchy – reduce, re-use, recovery and disposal.
  • OUTCOME

    The work is ongoing.

    Site location and environmental information

     

    Traffic-light plot – benzo-a-pyrene in groundwater

     

    AQIA, Cringleford, Norwich


     

    AQIA, Cringleford, Norwich

    LOCATION:   Cringleford, Norwich

    PROJECT TYPE:   Air Quality Impact Assessment

    VALUE:   £10K

    BACKGROUND

    As part of the planning requirements for two proposed residential developments (650 houses over 6 phases) in Cringleford, Norfolk, Harrison Group was commissioned to carry out an Air Quality Impact Assessment (AQIA) on behalf of Kier Living and Big Sky.

    The potential impacts from air emissions and dispersion of pollutants from traffic flows and construction were modelled and compared with relevant legislation, planning policies and Regulatory Air Quality Standards (AQS) and Objectives for the local area.

    SCOPE OF WORK

    The AQIA was completed in accordance with the latest Institute for Air Quality Management (IAQM) and Defra guidance.

    Levels in air of NO2 and Paticlate Matter M10 from road traffic were derived using the Atmosheric Dispersion Modelling System-Roads version 5 emission and atmospheric dispersion model based on traffic density, type and average speeds, source emissions factors, meteorological data, road layout, and location of sensitive receptors.

    Impact was assessed based on modelled changes in local air quality and comparison with AQS and Objectives at sensitive receptor locations, and cumulative effects from other planned or proposed developments in the local area.

    Emissions were calculated using the latest emissions factors from Defra, based on the 2013 and 2026 emission factors respectively within the Emission Factor Toolkit v8.0 incorporated into ADMS-Roads.

    Model verification was completed based on the South Norfolk District Council diffusion tube monitoring data and available co-located traffic data at the following locations.

    OUTCOME

    All work was carried out to the satisfaction of the client.

    • Contour plots showing the ground level concentrations of NO2 for the 2021 With Development and Committed Development scenario were derived
    • All modelled levels at sensitive receptor points were shown to be less than 75% of AQS with less than 2% change relative to AQS compared with baseline levels
    • As per the Institute of IAQM Guidelines the development effects were assessed as having a negligible impact on air quality.

    Road links and sensitive receptors

     

    Modelled NO2 contours

     

    Greenyard Frozen, King’s Lynn


     

    Greenyard Frozen, King’s Lynn

    LOCATION:   Greenyard Frozen, King’s Lynn

    PROJECT TYPE:   Environmental Permitting

    VALUE:   £50K

    BACKGROUND

    Greenyard Frozen, King’s Lynn, is an 80,000 tonnes/pa facility which processes, packages, and distributes a variety of vegetables including, peas, beans, brassicas and a variety of root vegetables.
    The installation includes a main processing factory, two modern packing halls, cold stores and associated infrastructure. In addition to this, process effluent is channelled to an on-site 500,000m3/pa Effluent Treatment Plant (ETP).
    Based on it’s production capacity, Greenyard is required to have an Environmental Permit (EP) for the site in order to meet the requirements of environmental regulations for the food processing sector.
    Harrison Group Environmental provided comprehensive consultancy services, guidance and assistance, from preparing the initial Permit Application, Improvement Conditions, Permit Variations, Site Condition Reports, and Permit Surrender Reports.

    SCOPE OF WORK

    Harrison Group has worked with Greenyard Frozen (originally Pinguin Foods) since 2005. At this time we provided consultancy services to the company, resulting in the successful application for the initial EP (known at the time as a PPC permit) covering the installation.
    We worked closely with our client to ensure a cost-effective response, appropriate to the needs of the facility. This included consideration of Best Available Techniques (BAT), environmental emissions and impacts, Environmental Management Systems (EMS) and resource efficiency audits.

    Since 2005, Harrison Group has provided full support for the EP Improvement Programmes including:-

    • Waste minimisation audits
    • Noise management plans
    • Odour management plans.

    Also substantial variations to the EP were negotiated and secured for the following:-

    • Land acquisition for a new Cold Store and Permit Surrender of a parcel of land to a large supermarket chain. Harrison Group provided site investigation Due Diligence reports, Site Closure Plans, pre-purchase & post-closure soil and groundwater investigations and remediation assessments for formal permit surrender
    • Addition of a Combined Heat and Power Plant to process biogas from the effluent treatment plant and recover energy via a biogas engine. The application included detailed air quality emission and dispersion modelling to demonstrate compliance with Air Quality Standards as well as production of Management Plans for Environmental Emergency and Accident & Odour.

    OUTCOME

    • Harrison Group ensured that Greenyard Frozen had a successful application for their initial Environmental Permit
    • Future substantial variations to the Permit were negotiated and secured.
    • Harrison Group is supplying ongoing support for the Permit Improvement Programmes.

    Nitrogen level contours from biogas emissions

     

    Biogas engine

     

    Great Yarmouth, Proposed Third River Crossing

     

    Great Yarmouth, Proposed Third River Crossing

    LOCATION:  

    PROJECT TYPE:  

    VALUE:  

    BACKGROUND

    The proposed Great Yarmouth Third River Crossing scheme will provide an additional route over the River Yare. This will involve the construction, operation and maintenance of a new bascule bridge.

    It will provide a connection between the strategic road network (A47) and the businesses and commercial parks located on the South Denes Peninsula

    In order to gain a Development Consent Order the Planning Inspectorate is required to submit a report and recommendations to the Secretary of State.

    As part of this, Harrison Group were employed to carry out a supplemental site investigation, risk assessment, and waste assessment interpretative report for environmental data, in addition to a wider geotechnical site investigation.

    SCOPE OF WORK

    The interpretative report builds combines the information gathered from a number of different documents.

    These are prepared as part of the Environmental Statement and other design documents regarding site history and land use, groundwater and soil testing, baseline geology and hydrogeology, designation of stratigraphy and water bearing units, critical receptors, and Conceptual Model and Detailed Quantitative Risk Assessment (DQRA).

    The specific tasks completed were:

  • Compilation, integration, and summarisation of historical borehole and chemistry data into a quality controlled georeferenced electronic data set
  • Gap Analysis
  • Supplemental data collection
  • Spatial analysis – data overlayed with historical and proposed land use, site zoning, spatial coverage, initial screening values, traffic light plots
  • Statistical analysis – normal probability plots, statistical summaries, assessment of probability distribution, outliers and hot-spots
  • Waste assessment and management based on WM3 waste classification, WAC analysis, and potential for pyritic soils.
  • Once completed Harrison Group was able to:

  • Produce an updated and integrated risk assessment report based on data from all site investigation phases.This reviewed and updated site conditions, development plans, and engineering design and implementation
  • Identify hot-spots and baseline environmental chemistry of different geological units and materials
  • Classify waste and assess re-use and potential material management as per the waste hierarchy – reduce, re-use, recovery and disposal.
  • OUTCOME

    The work is ongoing.

    No items found

    Needham Market Quarry, Suffolk


     

    Needham Market Quarry, Suffolk

    LOCATION:   Needham Market Quarry, Suffolk

    PROJECT TYPE:   Ground investigation, supplementary contamination & geotechnical assessments and validation

    VALUE:   £165K

    BACKGROUND

    Needham Market Quarry in Suffolk was operated by Needham Chalks Ltd for more than 50 years, having previously been farmland. Hopkins Homes purchased the site for redevelopment, to provide 266 homes.

     

    Harrison Group was employed at the pre-acquisition stage by Hopkins Homes, to provide factual ground investigation information for consultant Coffey Geotechnics Ltd, and continued to provide geotechnical services throughout design and construction.

    SCOPE OF WORK

    The objective of the main ground investigation, carried out in October 2013 while the quarry was still operational, was to provide geotechnical, groundwater and contamination information. It comprised:

  • 27 cable percussive boreholes, to a maximum depth of 26m, with groundwater and gas monitoring standpipes installed at 15 locations
  • 20 cone penetration tests, to a maximum depth of 15m
  • 20 dynamic continuous sampling boreholes (for investigation next to buildings, vegetation and along the edge of the quarry lake), to a maximum depth of 4.1m
  • 14 machine-excavated trial pits to 3.5m depth and four trial trenches, to 4m depth, to gather data on shallower ground conditions, including material stockpiles
  • Six soil infiltration tests to 1.8m, to provide an overview of drainage potential
  • Geophysical surveys: resistivity and electromagnetic tomography profiling
  • Monitoring ground gas and groundwater levels, plus groundwater sampling.
  •  

    Investigations revealed most of the site was covered with between 0.1m and 13.8m of variable made ground, typically reworked from glacial sand & gravel and Diamicton. This material was excavated to expose the underlying Newhaven Chalk and used as backfill after quarrying or was stockpiled. Ground gas and low levels of soil contamination were also recorded.

     

    Based on its assessment of the investigation results, Coffey Geotechnics recommended:

  • Ground improvement of an area of thick fill, to mitigate differential settlement
  • Slope remodelling
  • Excavation through an embankment for a new access road
  • Installation of ground gas protection measures
  • Drainage and backfilling of the quarry lake with engineered fill (a new drainage basin was installed as part of the development’s drainage strategy).
  •  

    Hopkins Homes engaged Ingent Consulting Engineers (formerly JMS Consulting Engineers) to develop the engineering design and J Breheny Civil Engineering to undertake groundworks. We were employed to carry out further ground investigation and assessments, between 2015 and 2020, including:

  • Slope stability modelling and assessment, comprising further investigation, laboratory analysis; modelling carried out using Slope/W
  • Advising on the safe working and development of slopes, considering drainage and planned construction of roads and houses
  • Reviewing slope, drainage and earthworks design
  • Assessing ground gas, advising on protection requirements and reducing the area requiring protection
  • Further investigation of the chalk in one area, reducing the need for piling
  • Additional soil infiltration testing, to support detailed soakaway design
  • Site visits to sample and analyse waste generated during groundworks
  • Contamination investigations after earthworks exposed organic and potentially volatile material. Laboratory analysis of samples revealed low levels of PAH contamination
  • Development of the remediation strategy and method statement (agreed with the Regulator), comprising a simple cover system over exposed contaminated material. We also provided validation and verification reports for the client, regulator, warrantee provider and homeowners
  • Assessment of a pocket of asbestos exposed during groundworks to the Control of Asbestos Regulations 2012. Development of the remediation method statement, incorporating asbestos risk in the few plots affected.
  • OUTCOME

    The ground investigations and assessments were completed safely, within the timescales and programme budget and to the satisfaction of the consultants and the client. Hopkins Homes continued to request our involvement at critical stages during design and construction of the homes.

     

    Gavin Houghton, Head of Technical Services at Hopkins Homes, said:

    “Your investigations allowed a technically challenging site to reach an earthworks strategy conclusion, which facilitated a site, that has stood for many years, coming to fruition as a housing development and this is through the merit of the work of the Harrison’s team. From our experience on this and many other sites, we would recommend the Harrison Group for works of this nature.”

    Machine excavated trial pit

     

    Geophysical surveying

     

    CP drilling

     

    Hopkins Homes staged house construction on the site

     

    Fen Drayton Road


     

    Fen Drayton Road

    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.

     

    Ground gas monitoring

     

    Site location – Swavesey, Cambs.

     

    Former Whittingham Hospital


     

    Former Whittingham Hospital

    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.

    Former Whittingham Hospital pre-demolition

     

    Artist’s impression of the completed development