Site Investigation Safety

Site investigation (SI) involves drilling boreholes, excavating trial pits, and sampling soil and groundwater.
SI work can encounter unexpected hazards including contaminated ground, buried services, and ground gas.
Drilling rigs are heavy plant with rotating parts, hydraulic systems, and high-pressure water feeds.
Trial pits expose workers to collapse risk if they enter without adequate support or battering.
Contaminated land may contain toxic chemicals, asbestos, heavy metals, or explosive ground gases.
Groundwater encountered during SI may be contaminated and require specialist handling and disposal.
SI sites are often remote brownfield locations with limited welfare and emergency access.
Underground services including gas, electric, and water may not be accurately shown on record drawings.
CDM 2015 applies to site investigation works and requires a construction phase plan.
All SI personnel must be competent and hold relevant training for the tasks they are undertaking.

Unknown hazards	Site investigation deliberately explores unknown ground conditions, meaning hazards cannot always be predicted in advance.
Contamination risk	Disturbing contaminated soil releases toxic dust, fibres, and vapours that cause serious illness and long-term health damage.
Service strikes	Drilling and excavating without proper service checks has caused gas explosions and electrocutions on SI sites.
Legal duty	CDM 2015 and COSHH 2002 require risk assessments and safe systems of work for all site investigation activities.

Do

Don't

Complete a desk study and service search before any intrusive investigation.
Use CAT and Genny to scan for buried services before every borehole position.
Wear appropriate PPE including gloves, overalls, and RPE on contaminated sites.
Monitor for ground gases using calibrated portable gas detectors during drilling.
Support or batter trial pit sides before anyone enters for logging or sampling.
Dispose of contaminated arisings and water in accordance with waste regulations.
Establish an exclusion zone around drilling rigs during operation.
Brief all SI team members on the emergency plan and nearest medical facility.
Ensure the drilling rig is set up on stable ground away from edges.
Record all unexpected finds including contamination, asbestos, or services.

DON'T drill or excavate without confirming buried service locations first.
DON'T enter trial pits that are unsupported or deeper than 1.2 metres.
DON'T handle contaminated soil samples without appropriate protective gloves.
DON'T ignore unusual smells, discolouration, or visible contamination in the ground.
DON'T work near a drilling rig without understanding the exclusion zone limits.
DON'T dispose of contaminated water or soil without proper waste classification.
DON'T allow unqualified personnel to operate drilling rigs or sampling equipment.
DON'T assume service plans are accurate; always verify on site with detection.
DON'T continue work if gas monitoring indicates hazardous atmospheric conditions.
DON'T leave open boreholes or trial pits unattended without barriers and covers.

See also: Contaminated Land Safety Awareness | CAT and Genny Safe Use

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