Our services encompass all of the Geotechnical and Geo-environmental disciplines.


Phase 1 Preliminary Risk Assessments (Desktop Studies)

  • Contaminated Land Risk Assessment (Conceptual Site Model)
  • Environmental Impact Assessment
  • Geotechnical and Geological Hazards
  • Hydrological Hazards
  • Mining Related Hazards
  • Unexploded Ordnance (UXO) Assessment
  • Radon Assessment

Phase 2 Site Investigation

Site investigation encompasses a wide variety of intrusive and non-intrusive ground investigative techniques to facilitate the collection of samples, to perform in-situ geotechnical testing or to install specialist instrumentation.

The objective of site investigation is to explore the outcomes of the preliminary risk assessments to realise, reduce or eliminate the inevitable element of risk associated with any development. Site investigative techniques include but not limited to, trial pitting, trenching, dynamic sampling, rotary drilling, cable percussive boring, dynamic probing, geophysical surveying and static cone penetrometer testing (CPT).

Terra Firma Wales Ltd have extensive expertise in the design, management and safe supervision of all site investigation techniques and maintain steady and reliable relationships with a wide variety of approved contractors.

Phase 3 & 4 Site Remediation and Validation

  • Remediation Options Appraisals
  • Remediation Strategy Reports
  • Groundwater Modelling
  • Mining Stabilisation Works Design and Supervision
  • Validation Works Supervision and Certification
  • Earthworks Performance Validation
  • Ground Gas Protection Systems Verification

Geotechnical Engineering/ Consultancy

  • Slope Stability Investigation & Assessment
  • Foundation Recommendations
  • Earthworks Specification and Supervision
  • Geological & Geomorphological Mapping
  • Earth Retaining Structures
  • Expert Witness Services
  • Working Platform Design

Soakaway Investigation (SuDS)

  • Soakaway testing to BRE DG 365:2016
  • Percolation Testing for Field Drains BS 6297:2007+A1:2008
  • Infiltrometer testing to BS EN 12616:2013
  • Deep Borehole Variable Head Permeability Testing BS 5930:2015+A1:2020

Drone Surveys

The use of drones in the construction industry is quickly becoming the preferred way to produce surveys and inspections of sites large and small in the most inaccessible areas eliminating the need to provide access for personnel.

Surveys undertaken with drones use photogrammetry which utilises a series of overlapping photos that once processed produce a 3D point cloud from which a mesh model and topographic survey can be derived. The applications are many including monitoring, measurements, volume estimations and many more.

For inspection high resolution photos and video can be collected or even viewed live on site as the survey is being undertaken. This allows for greater flexibility and for the client to direct to the flight to specific areas of interest identified during the flight.

Data can be collected at all points of a project with initial surveys undertaken during the design and planning stage to high light potential issues. Regular survey during construction can be used to provide as built information, progress updates and records and identify possible future issues. On completion of the project for inspection and maintenance.

Terra Firma are able to undertake flight planning and risk assessments, on site surveys and data processing with two qualified pilots operating under a Permission for Commercial Operations from the Civil Aviation Authority.

Coal Mining Risk Assessment

  • Desk Based Assessment and Intrusive Surveys of Historical Mining Features
  • Acquisition of Coal Authority Reports, Mine Abandonment Plans and Permits
  • Interpretation Undertaken by Experienced Engineering Geologists

In-Situ Field Testing & Monitoring Services

  • California Bearing Ratio (CBR) Testing
  • Plate Load Settlement Testing
  • In-situ Sand Replacement Density Testing
  • Moisture Content Testing
  • Dynamic Sampling (Dando Terrier Drilling Rig) – SPT and Dynamic Probe Testing
  • Soakaway Testing Bowser and Licenced Standpipe
  • Ground Gas Monitoring
  • Volatile Organic Compound (VOC) Monitoring
  • Concrete Coring
  • Land Surveying
  • Buried Utility Avoidance
  • Groundwater Monitoring
  • Water Quality Monitoring

Waste & Material Management Plans

The disposal of soils can form a significant portion of development project costs and developers are required to operate within the associated regulations.

Terra Firma Wales Ltd offer a number of services enabling developers to identify the most cost-effective means of Material Management and Soil Waste Disposal. In addition to landfill disposal, Terra Firma Wales Ltd have wide experience in helping clients identify other means of soil disposal, treatment and re-use.

Waste Services include;

  • Chemical Analysis of Waste Soils
  • Classification of Waste Soils to WM3
  • Practitioners with valid Advanced Hazardous Waste Classification Training
  • Preparation of CL:AIRE DoW:CoP Material Management Plans
  • CL:AIRE Qualified Person (QP)
  • Recycled Aggregate Testing
  • Preparation of Earthwork Specifications
  • Supervision and Validation of Earthworks

Ground Gas Protection Systems Verification

Terra Firma Wales Ltd are proud to offer a comprehensive in-house Ground Gas Protection System Verification service. Services comprise the preparation of Pre-Verification Plans to CIRIA C735:2014, C748:2014 and BS8485:2015+A1:2019, as well as on-site gas membrane integrity testing, including Air Lance Testing to ASTM D4437-08, Dielectric Testing & Tracer Gas Testing.

Terra Firma Wales Ltd ground gas verifying officer holds an NVQ Level 4 – Diploma in Verification of Ground Gas Protection Systems and is an accredited person under the CL:AIRE Gas Protection Verification Scheme (GPVS) approved as a Specialist in Gas Protection Verification (SGPV). Through the GPVS Scheme the specialist accredited person is able to provide Declaration Certificates which are a recognised Quality Mark, indicating the SGPV has verified the work to have been carried out in accordance with industry standards. Terra Firma Wales Ltd ground gas verifying officer is also a full member of the British Verification Council (BVC).

Retrofitting of hazardous ground gas protection measure in existing or refurbished buildings is fraught with challenges and not suitably manged could cause significant delays and additional cost to the development. Terra Firma Wales can provide practical solutions to remedy the situation and verify its suitability in accordance with CIRIA C795:2020.

On sites where the ground gas regime is not fully understood or classified, Terra Firma Wales Ltd are experienced in Detailed Ground Gas Risk Assessment for Methane, Carbon Dioxide, VOC’s and Radon gasses, focused at quantitating risk with the aim of reducing client construction fees and subsequent validation costs.

Terra Firma Wales are independent from membrane manufactures and suppliers and able to provide impartial advice with regards to ground gas protection product selection and suitability.

For help and advice, please get in touch:

   CL:AIRE Gas Protection Verification Accreditation Scheme htt3ps://

   British Verification Council