Combined Phase I-II Environmental Assessment – Ringwood 

Background: 

Omnia were commissioned by our client to undertake an intrusive geo-environmental site investigation at a vacant brewery in Ringwood, Hampshire which is due to be developed into commercial office space and associated infrastructure. 

The purpose of Omnia’s intrusive investigation was to provide information on potential sources of contamination on site as well as providing geotechnical characteristics of the soils beneath the site. These works were undertaken through a combined geo-environmental report.

Scope of Works

A Phase I-II Combined Geo-Environmental Study was completed with a Conceptual Site Model which identified multiple potential active contaminants and pathways such as heavy metals, PAH and TPH from landfill, historical development of the land using made ground, gas works, potentially infilled land and various historical land uses which required further intrusive investigation.

The ground investigation was undertaken utilising five (5no.) window sampling locations to investigate the potential sources of contamination identified within the Phase I and to obtain sufficient information on: 

• Geotechnical characteristics of the soils.

• Chemical concentrations and composition of soils within areas of identified potential contamination sources.
• Ground gas monitoring to assess potential sources of ground gas.

Ground conditions within all locations were logged and recorded in accordance with British Standard BS5930:2015+A1:2020 (Code of Practice for Ground Investigations) by an Omnia engineer. 

Soil samples were tested for a range of determinants which did not identify any elevated concentrations over the residential with Home Grown Produce Tier 1 GAC values. Ground gas was monitored over six (6no.) return visits across three (3no.) locations for ~5 weeks to assess the potential contaminant sources. Elevated methane and carbon dioxide was found, and the site was classed as requiring CS-2 level gas protection.

Outcome

Omnia’s Geo-Environmental Site Investigation concluded:

• Soil analysis did not identify any elevated concentrations of any determinants when screened against residential with home grown produce.
• Ground gas monitoring was carried out which indicated the site was classified as a CS-2, and appropriate gas protection measures should be installed.
• Geotechnical testing of the locations resulted in the recommendation of further investigations once the proposed development was finalised due to encountered groundwater potentially altering the bearing capacity of the soil.

The site was deemed suitable for the proposed end use with gas remedials. However, Omnia did recommend the implementation of a discovery strategy, and that winter groundwater monitoring would be beneficial to assist calculating the year-round bearing capacity of soil for foundations.