Human Health Risk Assessment - Former Gasworks

CASE STUDY - HUMAN HEALTH RISK ASESSMENT FOR EXISTING PROPERTIES ON A FORMER GASWORKS SITE, COMPRISING FURTHER ASSESSMENT OF CONTAMINATED LAND UNDER PART IIA OF THE ENVIRONMENTAL PROTECTION ACT, SOUTH MIDLANDS

WD Environmental was commissioned to undertake further assessment of potentially contaminated land under Part IIA of the Environmental Protection Act.  The work comprised quantitative human health risk assessment for the existing residents of properties that were built in the 1950s.  They were located on the site of a former gasworks that, as far as the Local Planning Authority were aware, had not undergone appropriate remedial works prior to construction of the properties.  The LPA required a decision on whether there was significant possibility if significant harm to the residents (as defined under Part IIA) and whether the site could be determined as contaminated land.

The LPA also required assessment of the site to determine whether:

•·          Urgent remedial action was required

•·          There was a risk to water services

•·          Vapour inhalation pathways were significant pollutant linkages

And also to:

•·          Generate SSAC for the development as remedial targets if required

•·          Advise on the extent of possible remediation

  

The risks from the following parts of the site were separately assessed:

•·          Topsoil, at 0.6m depth in gardens

•·          Deeper subsoils, at >0.6m depth in gardens

•·          Subsoils beneath houses, at 1m depth

•·          Subsoils beneath permanent, non-porous hardstandings

•·          Subsoils beneath semi-permanent hardstandings

The results indicated that urgent remedial action was unlikely to be required.  However it was concluded that shallow contamination could be sufficient to permeate water pipes and further information as to the location and composition of the pipes was required.  Inhalation of indoor air was recognised as a potentially significant pathway and indoor air monitoring was recommended.  It was concluded that further, more detailed site investigation data should be obtained before the site could be determined under Part IIA but that the site was not a Special Site.