Expert Geotechnical & Environmental Consultants in Cornwall
Ground Consultants Limited offer a range of services across the environmental and geotechnical sector, to enable your development get off the ground as smoothly as possible
Experience
With over 70 years of combined experience across the team, we have the technical knowhow to overcome any ground issues your site may present, from stability to contamination.
Our clientele range from one-time developers to national house-builders, as well as architects, civil/structural engineers, public sector organisations and ground investigation consultancies.
We are proud to be listed as an Accredited Agent under the Accredited Agents Scheme with Cornwall Council.
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Frequently Asked Questions
Environmental Risk Assessment
How long does a Phase 1 desk study usually take?
At Ground Consultants a Phase 1 Desk Study typically takes around 7-10 working working days, providing we can access the site for a walkover survey within that time. Its always best to request a free bespoke quote, as timescales vary based on workload.
What is a walkover survey and what does it involve?
As part of the Phase 1 Desk Study, and engineer from GCL will visit the site and take general site photos and notes. The walkover survey is a requirement of Cornwall Council, and is included with all GCL Phase 1 Desk Studies.
The walkover survey can take anywhere from half and hour to 2 hours, depending on the size and complexity of the site. Generally, for small residential developments, the survey should take no more than half an hour.
We do not need anyone present, unless there are access restrictions or indeed unless you’d prefer to be there.
What comes after a Phase 1 desk study? Will further investigation be required?
The flow-chart below helps explain what might come next:
In what format will I receive my completed report?
All reports are provided in PDF format. Cornwall Planning Portal limit file sizes to 10mb, so all PDFs are compressed to less than 10mb, or split into smaller files. Hard copies can be purchased on request.
How much does a Phase 2 investigation cost?
The cost of a Phase 2 investigation varies based on the findings of the Phase 1 desk study. A basic Phase 2 investigation involving hand-pits can cost as little as £750 + VAT, while an investigation involving gas monitoring (to investigate ground gas risk from a nearby landfill for example) can cost upwards of £3,000 + VAT.
An average cost for a “typical” site would be between £1,500 and £2,000 + VAT.
What is the CLEA Model?
CLEA stands for Contaminated Land Exposure Assessment, and is a piece of software used to help assess the risks of contaminated land exposure for human health. The CLEA model is used to generate site specific risk levels following specific chemical testing.
I’ve been told I need soil sampling, what is this?
Soil sampling generally involves testing shallow soils for a range of contaminants identified during a phase 1 desk study. Soil is collected into small glass and plastic containers and sent to a laboratory specialising in soil analysis.
Why have I been asked by the local authority for a Phase 1 desk study?
Phase 1 desk studies are requested by Cornwall Council (though often referred to as ‘contaminated land risk assessment’) based on the site’s proximity to potential sources of contamination. Examples are electricity substations, industrial land uses (petrol filling stations etc), landfills and cemeteries to name just a few.
Is my site likely to be contaminated?
This depends on your site’s location and the proximity of any contamination sources. In Cornwall, the most common source of contamination is Arsenic, derived naturally or as a biproduct of historic mining activity.
You can check the Arsenic levels in your area here. Be sure to select Arsenic in the drop-down menu in the top right, and then enter your postcode on the left of the page. Arsenic levels are shown when the map is clicked on. To find out if the levels in your area are likely to require soil sampling, get in touch here.
What is bioaccessibility testing?
Bioaccessibility testing is a laboratory test which essentially simulates the conditions inside the human digestive system, to determine how much Arsenic is actually absorbed by the body.
For example, soil samples on site may indicate Arsenic levels of 100mg/kg (greatly exceeding the 37mg/kg threshold for residential land use). Bioaccessibility may indicate that only 20% of the 100mg/kg of Arsenic is actually absorbed by the body. We can then use this data, along with the CLEA tool, to reduce the risk.
Do I need a mine search alongside my Phase 1 desk study?
Many areas of Cornwall have seen extensive historic mining which present a risk to development in terms of stability and contamination. At Ground Consultants we check each site at the quotation stage to assess the potential need for a mine-search and will advise accordingly. We work closely with a number of trusted mine search providers across Cornwall to provide mine searches alongside our phase 1 desk studies.
Geotechnical / Site Investigation
What is a plate bearing test?
Plate bearing tests, commonly referred to as “plate load tests” or “CBRs” are a quick and effective way to simulate an imposed load on the ground. The test has a range of implications, with the most common being to determine likely settlement under a specified load (for example for a crane mat), or to obtain a CBR value for road/pavement design.
More information can be found here
What are SPTs?
Standard Penetration Tests (SPTs) are a simple test completed in a borehole or window sample hole that give an indication of the density of the underling soils and thus their strength. SPT test results are often used alongside geotechnical laboratory testing to aid foundation design. Foundation design in the absence of empirical strength data, such as SPTs results, should be avoided.
Can I supply my own excavator for trial pits?
Yes, however we recommend that the operator is fully trained and is competent in the excavation of trial pits. Generally we use our own trusted sub-contractors local to your site.
How long does a site investigation take?
This depends largely on the scale of the investigation and development proposals. Most greenfield development sites in Cornwall can be investigated in 1-2 days, with 10-15 working days for laboratory testing and a further 5-10 working days for data analysis and reporting. Long term gas/groundwater monitoring will of course extend the date of final reporting.
What is a percolation test?
A percolation test is used for foul drainage and follows the procedures set out in BS6297. A small excavator is required along with a water source (for example an outside tap).
An infiltration test is for surface water drainage and follows the procedures set out in BRE365. A standard excavator is required (e.g. JCB 3CX) as well as a large water bowser (a standard water supply will not be sufficient).
Do you provide detailed foundation design?
Yes, we offer preliminary design guidance on foundations (type, dimensions and allowable bearing capacity), floor slabs, retaining walls and concrete class.