Home Remediation Case Studies Case Study E4: Biopiling - Bioremediation and Groundwater Treatment of Former Plastics Factory
Case Study E4: Biopiling - Bioremediation and Groundwater Treatment of Former Plastics Factory


Plymouth City Council



Remediation Value




As part of the development proposals to regenerate the former Tail Mill Plastic Factory into a residential redevelopment, Churngold Remediation Ltd (CRL) have undertook the remediation phase of works to prepare the site ready for construction. The works took place in two phases:

  • Excavation and windrow construction
  • Soil treatment



The remediation works had to be split up into phases due to ecological planning reasons (bats).


Churngold Solution

Excavation and Earthmoving operations:

The excavation areas were set out by the site engineer based on the plans provided in the remediation strategy. A 360 Slew with arm mounted hydraulic breaker was used to undertake breakout of concrete slabs and foundations within the designated dig areas.  Broken up concrete was then set aside on site for crushing into a cap. All hardcore removal works were overseen by an experienced remediation engineer undertaking a watching brief to identify any contamination present on the hardcore arisings. A known cyanide contaminated area was selectively removed prior to the bulk excavation works commencing. Material was removed directly off site by a licenced waste contractor Excavation works were undertaken with a 13ton 360o excavator to remove identified  contaminated subsoils. All waste was hauled to the licenced on site treatment area for treatment via bioremediation.

Groundwater Remediation:

Following excavation of impacted soils within delineated zones, the groundwater residing within the excavation was treated. Firstly any Light non-aqueous phase liquids (LNAPL) or free product was targeted for removal using surface skimming. Concurrently, a pump and treat system was used to remove dense non-aqueous phase liquid (DNAPL) as well as treat the dissolved phased hydrocarbons within the groundwater. Following pump and treat operations CRL added an Oxygen Release Compounds (ORCs) to provide ongoing treatment of groundwater by enhanced aerobic biodegradation.

Free phase product recovery using a Vikoma© unit, (Komara 30 model) was used where visual product was observed. Oil was collected using oleophilic disk technology and transported to collection drums for disposal offsite.

Where struck, groundwater was abstracted from each open excavation area in turn and pumped to a water treatment facility where contaminants were stripped from the water prior to discharge to foul sewer. Groundwater abstractions were limited to a maximum of 20m3 per day and therefore negate the requirement to obtain a ground water abstraction licence from the EA.

Soil Treatment

Soils were homogenised and treated with bio nutrients before being placed into windrows to facilitate the bioremediation process. The windrows were periodically turned during the treatment process to help with aeration. All soils undergoing treatment were sampled and tested prior to during and after treatment to provide evidence that the remediation technique was successful.

Technologies/Methods Employed

  • Excavation and Screening
  • Groundwater Treatment
  • Free Product Skimming
  • Biopiles
  • Backfill and Re-profiling

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