Ash Remediation Management were contacted by a Midlands based construction firm regarding approximately 1000m³ of contaminated soil that was encountered on their site. It was assumed that this material would have to be disposed of off site with clean fill imported, this however, was not the case.

Ash Remediation Management analysed the contaminated material and confirmed that a bioremediation process would be an effective and viable remediation route. The material was conditioned with compost and fertiliser before being laid on a bunded aeration system. The aeration system facilitated more efficient contaminant breakdown allowing the post treatment material to be available for use sooner. During the treatment phase biopile ‘health indictors’ (e.g. contaminant, O­₂, CO₂ concentration and temperature) were monitored to ensure the effectiveness of the treatment process.

The remediation programme was completed in 9 weeks.

The former gasworks is located in Shropshire and it was purchased by a midlands based house builder. The site was polluted with typical gasworks contaminants (namely polycycic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), lead and cyanide) and in order to comply with planning regulations a detailed remediation programme was undertaken.

Ash Remediation Management provided a full remediation scheme including chemical stabilisation/solidification, bioremediation and the removal of contaminated waters. This case study discusses the ex-situ bioremdiation aspect of the project.

Material undergoing ex-situ bioremediation was conditioned with agricultural fertilisers and compost. In order to control internal biopile conditions as well as environmental releases, a closed aeration system was utilised. Coupled to this was regular interpretive monitoring, used to optimise the efficiency of the biopile. A total of 1400m³ of material underwent a 15 week treatment programme and the bioremediated soils were used as subsoil in the residential and landscaped garden areas.

All phases of the project were achieved within budget and the bioremediation work was concluded 8 weeks inside the project deadline.

Client – National Grid Properties

Principal Contractor – BAM Nuttall

Consulting Engineer – Amec

Location – Wallasey

Contract Value – £200K

Wallasey Gasworks were commissioned in 1861 and it is currently divided into operational and non operational areas. Measuring 4.4 hectares, the site is owned by National Grid Properties and under a voluntary remediation scheme large parts of the non operational site underwent bioremediation treatment.

Intrusive site investigation identified several contaminants including benzene and phenol at intolerable concentrations. The remedial objective ‘to reduce the contaminant concentrations to QRA derived acceptable levels’ evolved from this and prompted Ash Remediation Management’s involvement with the project. Ash Remediation Management designed and implemented an aerated ex-situ bioremediation solution for the treatment of around 6500m³ of impacted material.

Prior to site mobilisation a series of trials were completed to maximise the efficiency of the on-site stage of works. These investigations included analysis of microbial populations, the contaminant profile and site geology.

Initially, material was conditioned (based upon the findings of the trials) with a combination of composts, fertilisers and microbes. From here material was transferred to a bunded biopile area with associated drainage, sump and aeration systems. The aeration system facilitated the removal of volatile contaminants through the negative pressure generated by the fan or blower unit. Rather than simply discharge these volatile compounds to the atmosphere, an activated carbon unit was used to adsorb these harmful gases.

During the treatment stage of the programme, several biopile monitoring parameters were routinely evaluated to help maximise the efficiency and effectiveness of the biopile. The measurements included contaminant, O₂ and CO₂ concentrations as well as temperature and RH levels. The findings of the monitoring were frequently interpreted and reported to the client providing evidence of the efficacy of the bioremediation.

Although many other earthworks activities were taking place in and around the Ash Remediation Management working areas, the scheme completed ahead of the agreed project timeframes providing a high standard of health and safety throughout.

Client – PXP West Midlands Limited Partnership

Principal Contractor – Ash Remediation Management

Consulting Engineer – Wardell Armstrong

Location – Bromsgrove

Contract Value – £200K

The site was previously occupied by an electricity substation and site investigations identified elevated concentrations of Total Petroleum Hydrocarbons. This lead to the formulation of the remediation objective “ to ensure future site occupants are not exposed to unacceptable levels of soil and groundwater contamination and that risks to controlled waters are reduced to an acceptable level”.

Ash Remediation Management was appointed the Principal Contractor and the objective was addressed via a two stage demolition and remediation programme. Firstly, the decommissioning of the substation was completed and secondly, the hydrocarbon impacted material underwent aerated ex-situ bioremediation.

Ash Remediation Management is committed to WRAP’s initiative ‘Halving Waste to Landfill’ and throughout the project huge emphasis was placed on recycling and reuse. During the decommissioning work >95% of material was recycled on site and the bioremediation process again proved to be a successful, more sustainable alternative to landfill.

The bioremediation programme was completed ahead of the anticipated schedule in a little over 10 weeks. During the bioremediation treatment phase numerous parameters were monitored and controlled to maximise the contaminant breakdown rate. This high degree of management also had the indirect benefit of controlling the geotechnical properties of the material undergoing treatment. This was demonstrated by the ease at which the treated material was reinstated and compacted to achieve the required plate bearing and nuclear density gauge levels.

The project was completed on time, on budget and continued Ash Remediation Management’s zero health and safety accidents record. Ash Remediation Management strive to minimise the impact of their work on residential and commercial neighbours by completing projects in as sensitive an approach as possible. The Bromsgrove remediation scheme was no exception to this and the project was completed without causing disturbance to the public or others users of the industrial park.

Client – Major House Builder

Principal Contractor – Ford Civil Engineering

Consulting Engineer – Ashdown Site Investigation

Location – Dorchester

Contract Value – £50K

Ash Remediation Management has completed another successful bioremediation contract for a major house builder at a site in Dorchester with approximately 3000 tonnes of hydrocarbon impacted soil undergoing treatment.

As with all bioremediation projects carried out by Ash Remediation Management, a treatability study was completed. This early stage analysis provides specific background information on the soil to undergo treatment and gives important details on how best to condition the soil to maximise the contaminant breakdown. Based upon the findings of this, soil was homogenised with compost and a precise blend of agricultural fertilisers before being placed within the bunded treatment bay.

Working closely with the client on what was a highly congested site, Ash Remediation Management achieved the desired target levels within the timescale and budget whilst maintaining a safe working environment.

Ash Remediation Management also worked in an advisory role to help ensure that the conditions of planning were fully implemented. The success of the project meant that the client could progress the construction works to their originally specified timescale.