In-Situ Chemical Treatment

In-situ chemical treatment injects or mixes reagents into contaminated ground to neutralise pollutants.
Methods include chemical oxidation, reduction, stabilisation, solidification, and pH adjustment.
Reagents used can include hydrogen peroxide, sodium permanganate, zero-valent iron, and lime-based products.
Many treatment reagents are themselves hazardous, requiring COSHH assessment and specialist handling controls.
Exothermic reactions during chemical oxidation generate heat and can produce toxic or explosive gases.
Injection under pressure creates risks of ground heave, reagent surfacing, and injection injuries.
Workers must wear full chemical PPE including face shields, chemical suits, and appropriate RPE.
Environmental monitoring is required to confirm the treatment is working and not causing secondary contamination.
Emergency spill response equipment must be immediately available whenever chemical treatment is in progress.
The Environmental Permitting Regulations and COSHH 2002 both apply to in-situ chemical treatment operations.

Chemical hazards	Treatment reagents including strong oxidisers and acids cause severe burns, respiratory injury, and eye damage on contact.
Uncontrolled reactions	Exothermic reactions in the ground can generate toxic gas, explosive atmospheres, and sudden ground heave.
Environmental protection	Incorrect application can mobilise contaminants, spread pollution, and create secondary contamination of groundwater.

Do

Don't

Complete a COSHH assessment for every treatment reagent before it is used on site.
Wear full chemical PPE including face shield, chemical suit, and appropriate RPE.
Monitor for toxic and explosive gases continuously during chemical injection operations.
Have emergency spill response equipment positioned at the treatment work area.
Follow the treatment design specification for reagent type, concentration, and injection rate.
Monitor groundwater quality to confirm treatment effectiveness and detect migration.
Train all operatives in chemical handling, first aid, and emergency decontamination.
Maintain emergency eyewash and shower stations within immediate reach of the work area.
Record all treatment volumes, injection pressures, and monitoring results accurately.
Obtain environmental permits before starting any in-situ chemical treatment works.

DON'T handle treatment reagents without completing the COSHH assessment first.
DON'T mix chemicals without following the exact design specification and sequence.
DON'T inject reagents at pressures exceeding the design limits for the ground conditions.
DON'T ignore exothermic reactions; monitor temperatures and gas generation continuously.
DON'T allow unprotected workers near the injection area during treatment operations.
DON'T discharge treatment water or reagent residues without environmental permit approval.
DON'T store incompatible chemicals in the same area or secondary containment.
DON'T begin treatment without emergency decontamination facilities in place.
DON'T assume the treatment is working without groundwater monitoring confirmation.
DON'T skip first aid training for chemical burns and reagent splash injuries.

See also: Contaminated Land Safety Awareness | Chemical Spill Response

Presenter		Project
Location		Date

Toolbox Talk Record