Video Transcription

Simon: So the site we’re gonna talk about today is a petrol filling station that’s situated in London, United Kingdom. It was previously decommissioned about seven years, previously. There’s a workshop on site. This proposed residential development, we knew that potential sources remained on site. We knew that it was situated on a Secondary A Aquifer, which is a moderate risk really in the UK, 350 meters from a surface water body and in the mainly residential setting.

So when we were looking at the site, we had a guide that there was existing sources, potential sources of contamination on the site. These were underground storage tanks, above ground storage tanks, fuel lines, and interceptors . There’s also the form of forecourt area and workshops. We knew from published data that the geology comprised gravels over London Clay. And on the site walkover, we saw that there are residents situated on the north, south and western boundaries of the site.

So we developed a conceptual site model which identified, really, where the main areas of concern were. So, for this site, it was gonna be a residential redevelopment, so a very high-risk classification was given to human health, residential land use. There was also a high risk for the residents off-site if there was a plume migrating off site. There was a high risk to the controlled waters as well. So checkpoint really, is, have I developed a good conceptual site model? Do I understand what is gonna drive the remediation?

Onto the site investigation, so for this site, we initially targeted the potential areas of concern, i.e., the underground storage tanks, the above-ground storage tanks. Then locations were placed for site coverage and to enable a triangulation of groundwater flow and gradient to be determined. We also wanted to make sure that we had boundary monitoring wells adjacent to the residential dwellings that were on the site boundaries, so we wanted to try and establish whether there was a plume migrating to the residential receptors off site.