Contaminated Land

Land contamination can vary markedly over a vast range of pollutants.  Investigation into land contamination from surface to underground can be provided.  Sample collection will enable a wide range of chemical and physical hazards to be clearly identified.

Sites where asbestos contamination has been identified can create a special technical requirement to assess the true nature of the levels and hazards of the contamination.  Highly trained technical staff are available to support these types of investigation.

The investigation team will be able to designate waste or land under several categories as grossly contaminated, special waste, slightly contaminated, below 0.01% or clean.  During the investigation the site and the perimeter will be monitored and asbestos fibre migration measured, to protect the people and the environment.  Remedial works where necessary will be conducted under controlled air mist conditions, the maximum dust control and suppression. This will ensure the project continues with adhesion to current site legislation and Environment Agency standards.  Onsite analysis of materials and airborne fibre levels will be provided.

Site personnel, tools, equipment, vehicles will all be decontaminated at the end of the process and the final clean air certificate issued.

There are 3 levels of contamination

1) General Waste. No asbestos material is detected visually or by analysis in the soil / rubble concerned.

2) Soil / Rubble contaminated with asbestos. Generally only asbestos cement will be accepted in this category as other varieties can break down so as to prevent a visual assessment. Asbestos content by mass is >0% < 0.1%. Note this is asbestos content, not asbestos-containing material (for example, asbestos cement could have as little as 5% asbestos content). A number of ‘normal’ landfill sites can accept this material but will not accept Special Waste. This is less expensive to be disposed of than Special Waste.

3) Special Waste. >0.1% asbestos content by mass. Requires section 62 (Special Waste Consignment Note) from the Environment Agency and disposal at a Special Waste Licensed tip. This is now very expensive as the number of facilities has been vastly reduced. The client must retain the bottom copy of the documentation indefinitely when the carrier returns it to him.

If a supervising analyst controls the dig directly, materials excavated can be visually assessed and separated into each form to control the cost of disposal by limiting the amount of material needlessly disposed of as Special Waste. MIS Ltd Environmental has carried out this process on a number of occasions

As mentioned above, asbestos can contaminate nearby areas, workers and members of the public in two ways

1) Airborne fibre release- asbestos dust being released and blown off-site.

2) Cross-contamination- asbestos-containing materials being carried off site on worker's boots, clothes, or transport.

1) Airborne Fibre release- using a water bowser and fine spray nozzle, a mist of water or water pva mix can be drifted over the material during excavation, lifting and deposition on the wagon or dumper (this is a fine balance between over-weighting the material affecting tipping costs and dust suppression. Some training and experience will be required by the site operative involved but this takes a fairly short time to perfect. See photographs for this system in action at Paradise Tip, Witton Park, an 8 month long contract for One Northeast.

A mist spray or spray curtain can also be employed to down any airborne dust which positioned correctly. Any haul roads or areas of the site where contaminated machines are like to raise dust must be sprayed with a bowser to prevent any visible dust release. Airborne dust blowing across site is the most likely source of complaints from members of the public- they cannot tell whether it is asbestos or not, therefore its suppression must be regarded as essential.

To measure the effectiveness of these measures, the site analyst carries out continual long-term background monitoring at established sampling points on the site’s perimeter fence and personal monitoring on himself, plant operatives and any banksmen / spray operators.

2) Cross-migration- Control is achieved by fencing the site into Dirty (contaminated and work area) and Clean (parking, office and public access) areas and directing all access and egress between the two via a decontamination unit (people) and Wheel-washing facility (vehicles). A specialised metal trough with numerous nozzles to either side can be acquired for wagons to drive through and have wheels and bodies washed off as they pass through it. All site machinery (excavators, dumper trucks etc. remain on the Dirty side of the site until all work is completed. They are then power washed, allowed to drive and then swab tested and have reassurance air testing in their cabs prior to being allowed off site.

All site personnel must wear disposable PPE and suitable P2 or P3 RPE depending on the material being excavated. It is possible to acquire nylon overalls that can be re-used and sent to a specialist laundry for long-term jobs where the cost of disposables will become prohibitive. Regular reassurance air monitoring should be undertaken by the site analyst in the DCU’s clean end to ensure the system is working.

In order to prevent the work site itself becoming cross-contaminated by vehicles carrying asbestos waste as parts become completed, it is common practice to commence excavation down to clean at the farthest end of the site from the Clean area and work gradually back towards the entry / exit point- vehicles travel only over ‘dirty’ material. Otherwise, haul roads will need to be constructed from hard-core fill either from material crushed on-site or brought in at cost from elsewhere.

Transport of contaminated / special waste could prove extremely costly and where possible (with the consent of the client and the environment agency) retaining the waste on site (for example inside bunds or banks or under roads) should be investigated as the best environmental option. Remember that the waste will only end up underground anyway and if you can save the damage to the environment by transportation of the material by road as well as the cost of haulage and tipping, then this should be pursued. At the Seaham remediation site MIS saw the installation of contaminated waste beneath new roads being constructed and at Marske in Cleveland asbestos cement was used in the centre of newly constructed earthwork bunds. In all cases, the material must be capped (preferably with clay and some form of high visibility membrane to warn anyone potentially excavating in future) with at least 500mm of neutral material. The position of the waste along with depth and quantity must be carefully documented and the records retained indefinitely by the site owners.

Where waste must be taken off site (and with Special Waste this is usually the case) wagons must be covered (most have a removable cover anyway) and pressure washed after use. They can then be swab tested and verified as clean before commencing other work. The wagon can be sheeted out with polythene to prevent contamination if this is deemed practical based on the material being transported. Whilst on site and at the landfill, wagon drivers must keep windows closed and wear a disposable mask. Regular personal and reassurance air monitoring should be carried out in random wagons by the site analyst.

• Establish asbestos presence (trial pits and sampling)
• Draw up a specification and site plan
• Fence off site (warning signs) and designate clean and dirty areas
• Install DCU and wheel-wash across the barrier between clean and dirty
• Suppress dust release while excavating material.
• Visible dust or winds >20 knots stop work until problem subsides
• Visually identify the type of waste and treat accordingly
• Waste off site via wheel-wash with appropriate documentation
• Excavation works from the back of the site towards the wheel-wash leaving clean material behind
• All machinery jet-washed and tested prior to leaving site
• Final sampling to establish site cleanliness
• Leave site