Oil Rem Case Study 2

Phase 1 Assessment:
Like all Phase 1 assessments, a number of indicators such as ground fall, drainage, sewage runs, foundations, age of property, composition of the property, soil texture, quantity of released oil and run of the land were used to give a more accurate account of the incident and possible migration path of the pollutant.

Phase 2 Assessment:
During the Phase 2 assessment of the site, small bore holes were drilled through internal floors and analysed for volatile hydrocarbons using a Photo-Ionisation Detector (PID), readings in excess of 1240ppm were recorded. Externally samples were taken and analysed for Hydrocarbon (TPH) levels ranged from 44mg/kg to 372 mg/kg.

With these types of levels BELFOR recommended that an extensive remediation programme be performed on the property in order to decontaminate the site. If remediation was not undertaken then it was likely that there would be further migration of the contamination within the property.

Due to the intrusive nature of the work that had to be undertaken which included removal of the driveway and floor in the lounge, kitchen and porch, access to the property was severely restricted and therefore alternative accommodation had to be found for the occupier whilst the work was being carried out.

The work undertaken included:
- Removal and storage of all carpets in the lounge and dining areas, and cupboards from kitchen
- Excavation of all floors within the property and driveway to a depth of 1 metre.
- Checking for any damage caused to foundation block-work and seals within drainage pipes

Excavation
As a large amount of contaminated soil had to be removed, skips were being filled and removed on a continual basis. Any waste contaminated with oil has to be treated as Special Waste under Section 62 of the Environmental Protection Act 1990. This means the Environment Agency requires pre-notification of movements of Special Waste by consignment notes. These have to be kept for a minimum of three years and the Environment Agency may ask to see them at any time. This phase of works took 2 weeks, and then further site inspections were carried out to establish whether there had been further migration of the contaminant. As tests showed that the oil had been virtually eliminated, specifically cultured bacteria were used to digest any remaining hydrocarbons.

When it was clear that all oil contamination had been removed, reinstatement of the property to its pre-incident condition could begin. This involved:

- Replacing the water main from the back of the kerb of the footpath to under the kitchen sink at the rear of the property (approved by Welsh Water).
- Adding stone to all external excavated areas with approximately 100 tonne of crusher-run stone. - Replacing all rainwater drainage around the entire house.
- Replacing the removed external and internal brickwork.
- Adding stone to all internal trenches, then laying new 100 gauge membrane and 100mm of concrete.
- Re-laying all slabs around the rear and one side of the property.
- Putting back kitchen units and re-piping the kitchen as necessary.
- Redecorate the entire downstairs floor.
- Supplying and fitting new vinyl to the kitchen area and re-fitting existing carpets.
- Supplying and laying approximately 90 metres of paving. Self-level compound was then applied to the entire downstairs floor When this was completed the homeowner could return and resume normal life in the property.

Spread into the Neighbouring Property

At the same time as BELFOR were called to the first property with the leak, we were also requested to undertake a site investigation next door. Oil had started to appear through the block-work of their drive as well.

On inspection of the site we found that:

- There was a strong smell of oil with visible signs of oil within the driveway and garden area.
- Upon excavating areas to obtain soil samples these swiftly filled with water and oil.
- The storm drain to right-hand side of the property was exposed and was found to run the along the front of the property down which the contaminant had tracked into the front garden.
- A small bore hole was drilled in the lounge area and analysed for volatile hydrocarbons using a photo ionisation detector (PID), readings in excess of 400ppm were recorded.
- Following analysis of the samples taken from the driveway the Total Petroleum Hydrocarbon (TPH) levels ranged from 275mg/kg to 995mg/kg.

Once approval had been gained from the appointed Loss Adjuster, to go ahead with remediation work, immediate measures had to be taken to lessen the spread of the oil. Excavation of a trench at the end of the driveway and the side and front of the property was carried out and absorbents were placed in the trench to reduce the amount of contaminant migrating in these directions.

Other remediation work continued:
- Excavation of driveway and front garden to a depth of 1 metre. - Removal of contaminated water from excavated areas.
- Excavation of an area of floor in lounge, kitchen and porch to expose foundations.
- Replacement of water pipe.
- Replacement of storm water pipe.
- Installation of a concrete barrier between the two drives to prevent the adjacent driveway falling in as we excavated

After this phase of work further site inspections and testing were carried out and it was found additional works were required due to the extensive spread of this spill. Unfortunately the second property had more serious contamination than the first.

Phase two works included:
- Taking up paved patio area, dismantling shed and store. Digging to the depth of footings across rear and side of house including the removal of all storm drainage.
- Taking out all remaining flooring in porch area and digging down to expose brickwork to level of footings. - Removal and storage of all remaining kitchen base units.
- Extending trench in kitchen area along rear wall and adjoining lounge wall to the depth of the footings.
- Replacing contaminated brickwork, internal and external, from Damp Proof Course down to footings along the front elevation of the porch and along the side elevation of the porch down to the rear corner of the house. This was achieved by replacing 1 metre at a time so as not to affect the structural stability of the building.

Reinstatement
Following this extensive excavation testing now showed that we had been successful in removing the contaminated soil so bio-remediation could now take place to finish this part of the project.

At both properties, at the request of the water company, we had to replace the water main with Protecta-line, a unique polyethylene pipe system developed specifically for carrying drinking water through contaminated land. Reinstatement of this property was virtually identical to that of the first property

Following the completion of the project, the owner of the second property, wrote to BELFOR saying, 'Here are just a few lines to thank your company. You always kept my wife and I informed and up to date with the progress on our house. It may not sound much but I can assure you when you have been moved out of your home it is comforting to know people are still working on your case'.