Housing Development on Contaminated Land
Current government guidance requires all proposed housing development sites, that are to be built on or near potentially or known contaminated land, to undergo a Preliminary Risk Assessment to identify the potential risk from land contamination. As in the case studies highlighted on this page, this assessment may conclude that further testing is needed in order to determine the levels of risk present at the new build site, this is the point when further investigation, usually some form of Intrusive Site Investigation, should be carried out for the proposed housing development.Get In Touch
How To Assess Contamination Risk For a Residential Housing Development
Step 1 - The first step in assessing the risk posed by building a residential housing development on contaminated land involves carrying out a Phase 1 Preliminary Risk Assessment (Desk Study). This step includes consulting current and historical map data to identify any potential contaminant sources, on or nearby the site, that may have contaminated the land. Some contaminant sources may also be considered a potential receptor of contamination originating from the site, such as nearby rivers. Past on-site activities are often the main contamination source to consider when assessing the contamination risk posed to residents of a housing development.
Step 2 - The next stage of the desk study then involves assessing, in more detail, the potential sources, pathways and receptors present at the proposed housing development. This is then used to develop an initial Conceptual Site Model which allows us to identify 'contaminant linkages'. For a contaminant linkage to be present there must be a contaminant source for contamination to come from, a pathway for the contamination to travel through and a receptor to be affected by the contamination. If one of these is not present, there is no contaminant linkage and, therefore, no significant risk from contamination.
Step 3 - Following completion of a Phase 1 Preliminary Risk Assessment (Desk Study), a Phase 2 Intrusive Site Investigations may need to be carried out for a new build housing development on contaminated land. This will allow the assessor to measure the levels of contamination in the ground and therefore assess the risk to nearby receptors (i.e. residents, water bodies, wildlife etc). An Intrusive Site Investigation will generally involve a site visit to take soil samples, assessment of ground conditions, chemical analysis of the samples and analysing results with reference to industry standard screening levels. This final step will provide a clear picture of the contamination risk and, therefore, the requirement for any remediation at the proposed residential site.
The need for conducting an assessment into potential or known contaminated land for a new housing development may arise for a range of reasons, based on different specific requirements and desired outcomes and each project will be very specific to each individual case. For example, the scope of work for a Contaminated Land Investigation requested through a condition on a planning application for new build houses may be different to that required for land valuation, when buying/selling land for a housing development. Housing developments are particularly sensitive sites because of their residential end use, meaning it's especially important to ensure that the land being built on is free from contamination and a thorough investigation is the only way to determine whether contamination is present at the site of a new build housing development.
Housing Development on Potentially Contaminated Farm Land Case Study
Our client required a detailed assessment of contamination risk for a proposed housing development on potentially contaminated farm land. Contaminated land conditions were applied to the client's planning application which needed to be complied with, in order for the project to continue. The project involved building five new detached residential houses on existing farm land, also previously used as a small holding for farm machinery and various other materials. Our reporting identified potential risks, most notably, from hydrocarbon contamination of shallow soil in areas where farm machinery had been stored as well as asbestos contamination from asbestos roof sheets and, therefore, recommended that further investigation should be carried out to quantify these risks.
The complex and varied use across the long and narrow site meant that our investigations needed to include a targeted sampling strategy in order to appropriately sample soils on the farm, while avoiding unnecessary costs from excessive sample taking. On this farm land our sampling strategy involved a higher sampling density in the areas where more contamination was expected. Samples from 0.6m deep were taken, to account for the clearance of the top ~0.5m during site preparation, representing shallow soil at the site which was the area of soil most likely to be contaminated. As part of the project, we also created borehole logs to describe the soil types identified in the holes that were dug on site to help assess the contamination pathways that could be present at the site. For example, sandy soil will allow vapours to more easily migrate through the soil, while clay soil is more impermeable and will often mitigate the spread of contamination through soil.
How We Helped - Through soil sampling and assessing the ground conditions at this farm site, we were able to conclude that the site did not classify as contaminated land and, therefore, posed a low risk to human health and the environment. This was then confirmed with the local council allowing the client's housing development project to go ahead.
Housing Development on Contaminated Land Case Study
Our client's proposed project involved the construction of 10 residential dwellings along with a block of serviced apartments on the site of abandoned plant nurseries and an active storage and logistics yard. A desk study identified multiple contamination sources from the previous uses of the site and recommended that further investigation would be needed, in order to more accurately assess the contamination risks at the site. When a site is proposed for residential use the acceptable risk levels from land contamination are particuarly strict, especially when applying for planning permission, so it's quite common for detailed assessments of land contamination to be needed for a housing development of this kind.
How We Helped - We were able to advise on, and carry out all work required to satisfy planning conditions for the proposed housing development project, including desk studies, site investigation, UKAS & MCERTS accredited laboratory testing and comprehensive reporting. Following our identification of heavy metal and hydrocarbon contamination at the proposed housing development site, we were able to provide well informed recommendations to our client on how to proceed with the proposed housing development project.
Planning a Residential Development Project on Contaminated Land?
Whether it's to support a planning application or simply to ensure your site is uncontaminated, we can carry out detailed Contaminated Land Investigations for a range of housing developments and other similar construction projects.
1. Contact us and let us know your requirements
2. Following initial consultation we can provide an outline proposal detailing how we can help and the costs involved
3. Our environmental consultants will then get to work on enabling the smooth commencement of your housing development project
4. We generally complete contaminated land assessments for new build houses within days of your initial enquiry, allowing you to stick to schedules and minimise any disruption to your project