Site Investigation Works

Current Investigation Works

There are currently no site investigation works taking place under Part 2A of the Environmental Protection Act 1990.

Completed Site Investigation Works

Darlington Borough Council has carried out and completed site investigation works at four former landfill sites in accordance with the Contaminated Land Inspection Strategy:

Summerhouse Landfill site

Map showing the site investigation area of the former Summerhouse Landfill site [pdf document]

This site was used for refuse disposal between 1934 and 1974.

Site investigation works commenced on Monday 29 September 2008. The soil sampling and installation of the boreholes and probeholes were completed on Thursday 2 October 2008. Gas monitoring, ground water and surface water sampling was carried out over six months.

Darlington Borough Council has formally determined the former Summerhouse landfill site as not contaminated land under Part 2A of the Environmental Protection Act 1990

Highside (Heighington) Landfill site

Map showing the site investigation area of the Highside (Heighington) Landfill site [pdf document]

This site was used for refuse disposal between 1947 and 1978.

Site investigation works commenced on Wednesday 18 March 2009. The soil sampling and installation of the boreholes and probeholes were completed on Thursday 26 March 2009. Gas monitoring, ground water and surface water sampling is to be carried out at the site over a six month period.

Darlington Borough Council has formally determined the former Highside (Heighington) Landfill site as not contaminated land under Part 2A of the Environmental Protection Act 1990.

Shearwater Landfill site

Site investigation plan - Shearwater Landfill Site [pdf document]

Summary report - Shearwater Landfill Site [pdf document]

The Council identified a former landfill site in Shearwater Avenue as potentially contaminated land. In order to establish that the site does not pose a risk to human health or the environment a site investigation was completed. The investigation involved taking soil and groundwater samples for analysis from residential gardens and the recreational land on Shearwater Avenue. Ground gases were monitored in probeholes installed in residential gardens and the recreational land. Indoor air monitoring was also carried out at selected properties.

The Council received and reviewed the consultant’s reports. The report concluded that there is no concern with the results of the groundwater and soil sampling, both in the residential gardens and on the recreational land. Consequently no further works were recommended with regards to the groundwater and soils.

The investigation established that the level of gas generation from the landfill is very low and the rate at which it would migrate into properties is negligible. Ground gas was not detected in any residential property during the three rounds of indoor air monitoring. However, there was uncertainty concerning the results of one internal ground gas monitoring survey carried out at a residential property in the 1990’s.

In order to deal with this, and confirm the conclusions of the ground gas investigation the consultant recommended a further three rounds of indoor air monitoring at selected residential and commercial properties. This work was completed between April and July 2011. The results confirmed the minimal risk from ground gas ingress into properties. This has enabled the Council to conclude the investigation and make a decision that the site does not meet the definition of “Contaminated Land” under Part 2A of the Environmental Protection Act 1990.

Bensham Park (former Salters Lane North Landfill site)

Map showing the site investigation area of Bensham Park (formerly Salters Lane North landfill site) [pdf document]

Summary Report - Bensham Park [pdf document]

The site was formerly a brick works with an associated clay pit between approximately 1887 and 1939. By 1948 the pit had been infilled with waste. The current site use is recreational, allotment gardens and club house.

The Council commissioned Buro Happold, a specialist environmental consultant, to plan the site investigation works. This work involved installing ground gas and groundwater monitoring points within the recreational ground and taking soil samples from the recreational ground and allotments. The site investigation works started on Monday 15 November 2010.

Buro Happold provided the Council with the results of the investigation and risk assessment that shows there are no concerns with regard to the soils on Bensham Park and the majority of the allotments, with the exception of two areas (north of Plot 62 allotment and the area known as the south-western allotments). There are no risks to controlled waters associated with the landfill, and no risks to the club on site and the surrounding properties from landfill gas migration.

Buro Happold suggested three options for the two areas of the allotments to further investigate/mitigate any potential risks:

  • Further sampling and analysis within both areas to allow statistical analysis to be undertaken to better quantify the potential risks and; and/or
  • Bioavailability testing of some soil samples from the two areas to enable more accurate site specific assessment criteria to be derived and to better quantify the potential risks; or
  • Import clean inert topsoil to the two areas to provide a cover layer.

The Council considered the recommendations from the consultant and decided to spread approximately 450 mm of clean topsoil onto the two areas to act as a cover layer. The topsoil was delivered on Wednesday 4 and Thursday 5 May 2011. This has the additional benefit of improving soil conditions for growing plants. Validation of the spreading of the topsoil will be completed towards the end of the summer.

The Council has now determined that Bensham Park (former Salters Lane North Landfill site) as not Contaminated Land under Part 2A of the Environmental Protection Act 1990.