Archives: Services

Harrison offers a range of geotechnical monitoring services to complement in-situ and laboratory testing and computer modelling. Monitoring can help ensure structural safety and to develop economical designs.

Geotechnical instrumentation is installed in boreholes, in the ground or within structures and includes:

• Piezometers to measure ground water level or pressure
• Inclinometers to measure ground displacement
• Borehole extensometers to measure movement along the borehole axis
• Vibrating wire settlement gauges to measure settlement or heave
• Digital hydrostatic profile gauges to measure the horizontal and vertical rotation of ground and structures and the heave and shrinkage of clay soils. They can also be used to monitor the short and long term effects of imposed loads.

Harrison Group has extensive experience of providing groundwater modelling and risk assessment, plus remediation services, for contaminated land projects in the UK and overseas.

We have completed the design, installation, monitoring, regulatory sign-off and decommissioning of remediation systems on brownfield sites, industrial and commercial facilities (landfills, chemical works and manufacturing plants) as well as private homes.

We use a range of methods and software to model contamination of groundwater, including:

• Risk Based Corrective Action (RBCA)
• R&D P20 (UK Environment Agency)
• MODFLOW
• BIOPLUME

Staff also have extensive experience with use of field equipment and chemical tests including:

• Gas chromatography
• Infra-red absorption spectroscopy
• Mass spectroscopy
• NMR spectroscopy
• Geoprobe
• Window sampling
• Membrane interface probe

Geophysics offers a rapid, non-invasive way of characterising the ground and can help ensure optimum targeting of key sub-surface features during intrusive investigations.
Various methods of geophysics can be utilised including:

• Seismic

• Resistivity/conductivity
• Gravity
• Electromagnetic
• Magnetics
• Ground probing radar

There are numerous applications including:

• Mapping underground workings / voids or obstructions
• Strata characterisation and bedrock profiling
• Landfill characterisation
• Contamination plume delineation
• Locating buried utilities
• UXO detection

Penetration testing is used to provide a rapid assessment of ground conditions.

Dynamic Penetration Testing (DPT) is carried by a wheeled- or track-mounted percussion hammer which drives a cone into the ground, providing a measurement of the relative density of the ground. DPTs can be carried out to a maximum depth of about 20m and more than 100m of testing is achievable in a day.

Cone Penetration Testing (CPT) involves hydraulically pushing a cone into the ground at a constant rate to provide geotechnical data that can be used directly in design. The technique is fast, with up to 150m of testing per day, with minimal soil disturbance.

A number of different cones are available, including those able to measure hydrocarbons, gamma rays and electrical conductivity, plus magnetometers for detecting buried UXO.

Trial pits and boreholes are the most common techniques used in ground investigations.

Trial Pits can be excavated either by hand or machine depending on project requiremenrts.

• Machine excavated pits

  are a cost-effective way of making rapid assessment of the shallow ground and groundwater conditions across a wide area. Samples can be obtained and in-situ testing carried out, including:

• Hand shear vane
• In-situ density
• CBR / plate bearing
• Soakaway (to BRE Digest 365)

• Hand excavated trial pits

  are used in sensitive locations to minimise the risk of damage to foundations or services.

Boreholes

Harrison Group uses a range of drilling techniques for investigation and monitoring purposes, on land and over water. Our site personnel have NVQ drilling qualifications, along with CSCS and PTS training, and all equipment complies with current health and safety requirements.

Boreholes allow soil and water samples to be taken for geotechnical and environmental testing. A range of in-situ tests can be carried out and instrumentation installed to monitor groundwater, leachate, gases and ground movement.

• Cable percussive drilling

  is used for boreholes in superficial deposits such as clays, sands, gravels and weak rock.

• Rotary drilling

  , using wheeled or tracked rigs, can penetrate very dense materials or rock. The technique allows continuous core samples to be taken for logging and testing.

• Dynamic continuous (‘window’) sampling

  is a versatile method of drilling small diameter boreholes using hand-held, wheeled or tracked equipment, which is ideal for limited access locations.

Harrison Group’s geotechnical engineers, geologists, hydrogeologists and environmental engineers work together to carry out site appraisal and due diligence, helping clients to assess the risks relating to the purchase of land and buildings quickly and cost-effectively.
Our reports provide an evaluation of the geotechnical and environmental risks and detail work needed to provide due diligence if the purchase goes ahead. Areas covered:

• Contamination and pollution
• Environmental health
• Flood risk
• Utility resourcing
• Geotechnical issues
• Ecological protection