Windy Edge, Alnwick, Northumberland – Geoenvironmental Appraisal

Windy Edge, Alnwick, Northumberland - Geoenvironmental Appraisal

Windy Edge, Alnwick, Northumberland – Geoenvironmental Appraisal

DBS supported our developer client with the geoenvironmental appraisal of the site; this comprised a contaminated land appraisal of the entire site to support a planning application for a change of use (Phase 1/Phase 2), and obtaining geotechnical information within Phase 1 of the development to identify foundation requirements for future properties and infrastructure.

Client:  The Northumberland Estates

Summary

Windy Edge is located at the eastern fringe of Alnwick, Northumberland, covering a total area of approximately 30 hectares. The site is located next to the River Aln.

The site is predominantly greenfield comprising several large fields and paddocks divided by single track lanes, with an area at its centre that was formerly in use as an abattoir. A sewage treatment works borders the site to the north that discharges polished effluent to the river, otherwise the site is generally surrounded by residential dwellings and farms/agricultural land.

Redevelopment proposals comprised a change of use to residential, with housing to be constructed in several phases due to the large size of the site. In addition, grass paddocks, a cycle track, allotments and SUDS ponds were also proposed.

DBS supported our developer client with the geoenvironmental appraisal of the site; this comprised a contaminated land appraisal of the entire site to support a planning application for a change of use (Phase 1/Phase 2), and obtaining geotechnical information within Phase 1 of the development to identify foundation requirements for future properties and infrastructure.Windy Edge, Alnwick, Northumberland - Geoenvironmental Appraisal

Potential contamination sources associated within the site were limited, comprising agricultural use and an abattoir, with a sewage treatment works located off site and other historical off site features such as depots and a gas works.

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 GI involved a combination of cable percussion boreholes sunk across the site to 10m bgl, installed with combined gas and groundwater provisions, window sample boreholes sunk to 5.0m bgl, and trial pitting to 4.5m bgl with a JCB 3CX Sitemaster. In situ testing was undertaken including SPTs and hand shear vane measurements.DBS geoenvironmental engineers supervised all works on site, including the taking and packing of all environmental and geotechnical samples for delivery to the respective testing laboratories.

The work included specialist biological sampling of the former abattoir area for Bacillus Anthracis (Anthrax); the samples were forwarded to the Public Health England Laboratories at Porton Down, Wiltshire (Rare & Imported Pathogens Laboratory), and common biological samples were also taken at the boundary of the site next to the sewage treatment works and scheduled for coliforms, e coli and salmonella.

Following completion of the site works, a post works environmental monitoring programme was undertaken for ground gas and groundwater levels over a period of three months.

Upon receipt of all testing data from the labs, and the completion of the monitoring programme, 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.

DBS supported The Northumberland Estates to successfully deliver the site for residential use.

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