DBS assisted The Northumberland Estates with the geoenvironmental appraisal of a new eleven hectare development site located at Alnwick, Northumberland.
- Client: The Northumberland Estates
- Date: September 9, 2014
- URL: Northumberland Estates
The site was to be redeveloped for residential use comprising a new residential housing estate, along with a new highway linking the development with Alnwick Town Centre and the A1 highway.
DBS’s brief was to prepare Phase 1 and Phase 2 reports to support the planning process for a change of land use, to identify potential contamination constraints to development, and to provide geotechnical information to support foundation design for new dwellings and infrastructure.
We also worked with Northumberland County Councils Highways Department with regards to providing geotechnical information for the new highway.
Our appraisal work commenced with the preparation of a Phase 1 Desk Study report to support the planning application, complete with a site walkover survey (a requirement of planning), this report identified potential sources of contamination based on the sites location and historical use, and established the sites initial Conceptual Model.
Potential contamination sources associated with the site were limited, comprising agricultural use (farming, sheep dipping, fuel/pesticide storage and septic tanks), a smithy and railway land; the former N.E.R Alnwick and Cornhill Branch line railway formed a boundary to the site that was dismantled in the 1960s following the Beeching report.
Due to limited potential for significant contamination, a robust CM established at desk study stage allowed a subsequent cost effective Phase 2 Ground Investigation (GI) to be designed. The investigation was based on a combination of a highly targeted approach to quantify localised areas of the site potentially impacted by industry, with a site wide grid system (non-judgmental) also used.
The grid system was set out on site by the DBS engineer using a hand held GPS receiver pre-programmed with exploratory hole co-ordinates, this ensured that there was no downtime when supervising the drilling subcontractors on site, the holes were set out accurately on the grid, and the delivery of the investigation proceeded to budget.
The GI involved a combination of cable percussion boreholes sunk across the site to 10m bgl, installed with combined gas and groundwater provisions, as well as trial pitting to 4.5m bgl with a JCB 3CX Sitemaster.
A DBS geoenvironmental engineer supervised all works on site, including the taking and packing of all environmental and geotechnical samples for delivery to the respective testing laboratories.
Following completion of the site works, and receipt of all testing data from the labs, a Phase 2 Geoenvironmental Ground Investigation interpretative report was prepared that updated the sites CM and provided a final risk assessment that identified that risks to receptors comprising human health, controlled waters and property were not present, and that the site could be taken forward without any need for a remediation options appraisal and/or site remediation.
The site is being taken forward to provide quality new housing for the town of Alnwick, and the new highway will improve the local transport links.