Radon risk assessment and monitoring, former school

The former school was identified as being within a radon affected area. Owing to the development stage and current unoccupied use of the building, a short-term monitoring assessment using multiple lines of evidence was considered appropriate.

GGS attended site to undertake a detailed site walkover, noting all observations relevant to radon mitigation and entry, including; building design and construction, current use, surrounding area and topography, ventilation systems and any potential below ground preferential pathways.

During the initial site visit, GGS also undertook:

• A Thoron survey – Thoron is usually found together in soil with Radon. As Thoron has a short half life (55 seconds), it is often detected very close to its point of entry, thus providing an indication of where Radon ingress may be occurring.
• Real time radon monitoring – Considering walkover and survey results, GGS selected discrete locations for real time Radon monitoring using a RAD7 Professional Electronic Radon Detector.
• Periodic measurements of Radon activity in soil – To provide an indication to the level of Radon activity within the near surface soils, close to the building footprint.

To provide an additional line of evidence to real time measurements, GGS strategically placed passive Radon detectors for short-term exposure. Following a two-week exposure of passive detectors, GGS returned to site to systematically repeat the lines of evidence approach.

GGS presented the multiple lines of evidence within a concise report, which included an appropriate mitigation options appraisal. The recommendations of the assessment were accepted by the local authority.

The short-term assessment enabled the developer to avoid significant delay and costs, whilst ensuring radon risk was managed for future receptors.