Its been a while since we posted anything due to being rushed off our feet with project work following the recovery from lockdown.
We have been working extensively all over the north of England, from Halifax up to the top of Northumberland just in recent weeks.
One project that has been interesting and ongoing through this period is the investigation and characterisation of a Petrol Filling Station (PFS) in Sunderland that we have now been working on since 2019.
The project has been challenging for several reasons:
1. The PFS has been closed over 20 years and was left by the operator in a semi-derelict condition.
2. The Petroleum Officer of Tyne & Wear Fire and Rescue Service had no records of the fuel storage and dispensing operations / record drawings for tank configurations etc, and none were available from the original operator.
3. The site is located above Magenesian Limestone geology, a Principal Aquifer (sensitive water resource).
DBS prepared a Phase 1 Desk Study report for the site in 2019 to support a planning application for a change of use to residential, with several pollutant linkages identified and deemed significant requiring investigation for human health, controlled waters (Principal Aquifer) and property receptors.
Planning consent was awarded by Sunderland City Council, subject to the satisfactory discharge of a number of pre-commencement conditions placed on the planning consent by both the LPA and the Environment Agency for contaminated land.
Ahead of completing a Phase 2 ground investigation, we appointed a specialist company to undertake a subsurface scan of the PFS forecourt to record subsurface infrastructure including fuel tanks and lines. This was needed before any investigation could proceed to ensure H&S issues did not arise, and that a pollution incident could be avoided, for instance by puncturing of the fuel tanks with a drilling rig.
Once the subsurface was accurately mapped we designed a ground investigation around the existing infrastructure. The work comprised the sinking of Window Sample boreholes to depths of around 5m bgl, and cable percussion boreholes to depths of 10.0m bgl, with installations for a subsequent gas/vapour and groundwater monitoring programme installed.
The resulting work was reported in a Phase 2 Geoenvironmental Ground Investigation report for agreement with the regulators, this was then followed on by a Controlled Waters Risk Assessment, Decommissioning & Remediation Strategy report following an extensive period of groundwater monitoring on site.
The work proceeded to plan without incident, and all pre-commencement planning conditions have now been discharged allowing the client to move on and start decommissioning / demolition and remediation work.
Following the closure of many PFS in the 1990s due to competition from supermarkets, PFS investigation has gone from something that was considered fairly routine at that time to now being quite rare. They have their own challenges and really need a detailed review and methodical approach to get the work delivered to the satisfaction of all stakeholders, without incident.
It will also be satisfying for local residents to have this site brought into residential use as the site had been left derelict in an established residential area for a long time now.