With respect to the redevelopment of land, our geoenvironmental reports typically include:
- a geotechnical assessment - including the derivation of pragmatic foundation solutions, the assessment of slope stability etc;
- an assessment of land contamination – including potential risks to both human health and controlled waters;
- consideration of hazardous gas issues - including landfill gas, radon and mines gas;
- a mining risk assessment in accordance with Coal Authority guidance;
- design of appropriate site preparatory (and where necessary remediation) earthworks.
Our comprehensive site investigation reports contain all the data necessary to satisfy ground-related planning conditions, NHBC, Building Control, the Coal Authority etc.
We speak to our Clients prior to submission of a costed proposal, in order to establish what they require and why. We take pride in the issue of robust, fixed-price proposals. In order to minimise the likelihood of further work, our proposals are based on a review of available information (geological & historical maps, Coal Authority & Environment Agency data etc), and often a site visit.
Ground conditions can be investigated by a number of techniques; those most commonly used by Lithos include:
- machine excavated trial pits;
- cable percussive (shell & auger) boreholes;
- window or windowless sampling boreholes;
- rotary boreholes.
Ground investigation typically includes:
- exploratory holes excavated by appropriate techniques, to appropriate depths, and at appropriate spacings;
- appropriate in-situ tests;
- detailed description of the ground encountered;
- retrieval of representative soil and groundwater samples.
A sufficient number of soil samples are collected from each exploratory hole at regular intervals to allow selected laboratory testing (contaminant and geotechnical) to be performed.
Soakaways provide a way to dispose of stormwater run-off from buildings and paved areas to ground, rather than to public sewer or watercourse.
Soakaways must store the immediate stormwater run-off and allow for its infiltration into the adjacent soil sufficiently quickly to provide the necessary capacity to receive waters from a subsequent storm. The time taken for discharge depends upon the soakaway size, and permeability of the ground in which it is built.
Lithos undertake soakaway tests in general accordance with BRE Digest 365 “Soakaway Design”. A trial pit is part-filled with water from a bowser and allowed to drain to near empty. Each test can take up to 5 hours, but it is generally possible to complete about 6 tests in a day.
Geoenvironmental Due Diligence
We are able to review existing data (including previous site investigation reports) and identify potential environmental liabilities associated with ownership of a site. Such work is usually undertaken in order to inform prospective purchasers and funders of a proposed acquisition. In essence, our report provides a due diligence environmental audit with respect to ground-related issues.
- See casestudies - Tees Alliance Group and Elland Power Station
Our report might include a description of current operations, although it is not a compliance audit (i.e. an assessment of whether or not the company is in compliance with applicable UK environmental legislation), nor is it intended to review the site’s Environmental Management System.
A preliminary investigation (desk study or Phase 1 report) includes the following works:
- an assessment of the land use history;
- determination of the site's environmental setting (by reference to geology, mining/quarrying, risks associated with hazardous gas (including radon, landfill gas, mines gas etc), proximity to landfilled ground, proximity to COMAH or explosive sites, hydrology, flood risk, and hydrogeology);
- a site walkover and inspection;
- assessment of anticipated ground conditions, including potential contaminants;
- assessment of anticipated foundation and engineering issues associated with redevelopment for a residential end-use;
- preparation of a conceptual ground model and design of an appropriate ground investigation.
Primary aims of the desk study are to identify key ground-related issues that may affect the site, thereby enabling the design and costing of an appropriate intrusive ground investigation.
For small scale development, a desk study may be all that is required to satisfy the Local Planning Authority; especially where the site has not been subject to any potentially contaminating previous uses.
A desk study might also enable “ballpark” assessment of abnormal redevelopment costs associated with the ground.
Conceptual Site Model
A conceptual site model (CSM) is often summarised in a drawing that shows a cross-section through the ground, identifying potential geotechnical and contamination hazards. The CSM is initially prepared after review of geological maps, environmental data, historical plans etc, and is subsequently refined in light of data obtained during a ground investigation.
In the context of land contamination, there are three essential elements to any risk: (1) a contaminant source, (2) a receptor (eg controlled water or people), and (3) a pathway linking the (1) and (2). Risk can only exist where all three elements combine to create a pollutant linkage. Risk assessment requires the formulation of a CSM which supports the identification and assessment of pollutant linkages.