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Soil & Water Risk Assessments

Overview

LEAP believes that in using the most up to date techniques both in the field and in the office, clients can be provided with the most accurate and reliable results, in the most timely and cost effective manner. This case study highlights the use of quantitative risk assessment to provide a robust and cost effective remediation scheme for the redevelopment of a former gas works.

Description and Investigation Design

Historically the site comprised part of a gas works and was more recently a builder’s yard. Contamination associated with the site’s former use and buried structures including gas holder bases and liquor tanks were anticipated on site. The site is located on a principle aquifer (Chalk) and adjacent to a sensitive tidal river. Redevelopment of the site with housing was proposed.
LEAP was appointed to carry out a review of the previous investigation reports carried out by others and to produce quantitative risk assessments for both human health and controlled waters for the site to provide remedial targets for site clean-up.
Seven intrusive investigations undertaken by various parties had identified elevated levels of petroleum hydrocarbons (TPH), phenols, cyanide and Polyaromatic hydrocarbons (PAH) as well as heavy metals in the shallow soils. Groundwater sampling detected similar contaminants in the shallow groundwater. Slightly elevated levels of TPH, PAH, phenol and metals were also detected in the deep groundwater within the chalk. River water samples both up and downstream of the site contained traces of cyanide.

Historically the site comprised part of a gas works and was more recently a builder’s yard. Contamination associated with the site’s former use and buried structures including gas holder bases and liquor tanks were anticipated on site. The site is located on a Principal Aquifer (Chalk) and adjacent to a sensitive tidal river. Redevelopment of the site with housing was proposed.

LEAP was appointed to carry out a review of the previous investigation reports carried out by others and to produce quantitative risk assessments for both human health and controlled waters for the site to provide remedial targets for site clean-up.

Seven intrusive investigations undertaken by various parties had identified elevated levels of petroleum hydrocarbons (TPH), phenols, cyanide and polyaromatic hydrocarbons (PAH) as well as heavy metals in the shallow soils. Groundwater sampling detected similar contaminants in the shallow groundwater. Slightly elevated levels of TPH, PAH, phenol and metals were also detected in the deep groundwater within the chalk. River water samples both up and downstream of the site contained traces of cyanide.

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LEAP Solution

LEAP is experienced in the use of the latest risk assessment tools to provide Site Specific Assessment Criteria (SSAC) for contamination to meet the approval of the local regulators. In this instance the previous reports had identified several “hotspots” of heavy metal, TPH and PAH contamination with the shallow soils to be removed from site.

LEAP employed the latest modelling techniques to provide a set of SSAC for the site to mitigate risk to human health. In addition, LEAP undertook a groundwater risk assessment to establish that the levels of contamination encountered within the groundwater did not pose a significant risk to controlled waters.

LEAP assisted the client in gaining regulatory approval for the proposed site remediation, and established a program of continued monitoring during the remedial works to confirm the groundwater model findings and to negate the need for costly groundwater treatment.

Project Overview


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Client

Remediation Contractor

Location

SE England

Sevices Provided

  • Review of Previous 11years of site investigation reports, desk studies and risk assessments carried out by others.
  • Detailed quantitative risk assessment for human health and controlled waters.
  • Risk Assessment Report with recommendations for remedial work and targets.
  • Waste Characterisation Report with recommendations for handling of surplus soils.
  • Foundation works risk assessment.
  • Negotiation with local regulators.

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Added Value

  • Detailed assessment of existing data, negating the need for further intrusive investigation
  • LEAP has extensive experience with risk assessment modelling; having been involved with the production of the Generic Assessment Criteria produced by LQM and with the production of SPOSH targets for Part IIA work. This in-depth knowledge enables LEAP to use the most up to date modelling techniques to provide cost effective solutions and to gain regulatory approval.
  • LEAP understand that risk assessment is a holistic process and not just “number crunching” which helps to ensure that our solutions are pragmatic, and cost effective, whilst meeting regulatory requirements

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