Category Archives: Contaminated Land

Is 3% to 5% Radon Dangerous?


It means that between 3% and 5% of the home in your area are above 200 Becquerels m-3 .The conclusion of this page is “if in doubt” test. Get a testing kit from UK Radon (Part of Government) and follow their instructions. Our professional advice is not to test for less than 3 months. It is quite likely to give and inaccurate result. Read on for more delicious boffin waffle:


You are reading this because Radon is dangerous. Radon is a radioactive gas, and  small percentages in the air that you are breathing can be disaster. But how small? And what does 3 to 5 % mean?

Every building contains radon but the levels are usually low. The chances of a higher level depend on the type of ground. UK Health Security Agency has published a map showing where high levels are more likely.

Above from UK Radon.It is boradley correct, but as well as the “type of ground” the type of building is very important.


The “action” level for Radon is 200 Becquerels m-3   At this point we don’t really need to understand what that means, just that is exists.

What Does 3% to 5% Mean?

It means that between 3% and 5% of the home in your area are above 200 Becquerels m-3  (the action level). The worst it could be is 30% over the level, and best is 1% or less.

So that is a bit confusing isn’t it. Is you home dangerous or not? Well really we would need to know a lot about you building before we could make a guess. Not only what radon was coming out of the ground (difficult to measure), but also how much of it leaks out (also difficult to measure).

Type of Building

Good – If the house is a modern building with a radon protection barrier, sump, and other features then chances are that you indoor air quality will be good (with regards to radon) and you will be below action level. But the bottom line is you do not know if you are safe unless you test. Perhaps the builders made some mistakes, perhaps they didn’t follow the plans, or the building inspector forgot to check. . . .

Bad – If the house is old, and maybe has a suspend timber floor, with no damp proof course, then radon can get in to the house from the ground. However, if the house also has old leaky windows and drafts coming under the door, then this may help keep radon levels lower, as they will have less chance build up. Things like positive input ventilation, or a wood burner, or a vented tumble drier can also affect air flow through the house, and affect radon levels. But the bottom line is you do not know if you are safe unless you test.

Ugly – An old house, with no damp proof course which as be subsequently upgraded to include double glazing, draft proofing and uses combustion appliances with balanced flues, will experience very little air flow, whilst allowing ground gases (including radon) in to the building. Very very much worth urgently doing some testing if you are in this situation.


The bottom line is you do not know if you are safe unless you test.

There are too many variables to predict accurately what the radon level in a house will be. All we know from the 3% to 5% bracket, is that “some” houses in your area have a problem.

Construction techniques, building age, choice of appliances, choice of heating systems, and user behaviour all play a role in radon levels. The bottom line is you do not know if you are safe unless you test.

When you do the test get you kits direct from UK radon:

They are the official government labs, and will not recommend test period of less than 90 days. Do not test for less than 90 days because of all the variables, as mentioned above, you need to measure for a long period to make sure results are representative.

Planning Consultants Bristol 


Desktop Study – Wotton-under-Edge

Desktop Study – Wotton-under-Edge

Southwest Environmental Limited have been commissioned to write a Desktop Study for a Site in Wotton-under-Edge.

Wotton-under-Edge is a market town within the Stroud district of Gloucestershire, England. Located near the southern end of the Cotswolds, the Cotswold Way long-distance footpath passes through the town. Standing on the B4058 Wotton is about 5 miles from the M5 motorway.

The proposed development is an extension to a property, and is adjacent to some in-filled land. This has flagged the requirement for a Site Contamination Assessment, the first stage of which is a Desktop Study. We aim to deliver the report on a 5 Working Days turnaround.

We are happy to discuss you site free of charge over the phone, so please give us a call. We try to be as quick as possible, and if you require a report quickly please say and we will do our best to get it to you for your required deadline. 

Contaminated Land Land Advice

Desktop Study – Slough

Desktop Study – Slough

Acting on instruction from a client in Ealing Southwest Environmental Limited have prepared a desktop study fro site in Slough.

The desktop study has been made of the site and this revealed that historically the site was of primarily back garden use. But more recently had been used for other purposes.

As is normally the case SWEL order a comprehensive data set, so as to make a review of the site.

It was established that a Phase 2 Investigation is required, owing to current on site use, which is mixed between storage and vehicle repairs etc. 

The report was turned around in 5 days.

Site Investigation & Phase 2 Assessment – Islington, London. N19

Site Investigation & Phase 2 Assessment – Islington, London. N19

Acting on instructions from a corporate client Southwest Environmental Limited have carried out an Environmental Site Investigation in connection with a property acquisition / purchase. 
SWEL managed to deliver a reduced scope report, sufficient for our client’s needs within a 3 week period, despite having trouble on site with buried services. 
The scope included the collection of 20 soils samples, with breaking out at each position. There were 3 deeper holes drilled, for installation of boreholes for gas and ground water monitoring. Although this was not carried out owing to time frame. 
Statistical Analysis of Results 
The site was operational at the time of the investigation, with high level of vehicular and pedestrian traffic,  despite this SWEL managed to complete site works within 2 days.
Soil testing was conducted on a rapid turnaround, and results were published as part of a contamination assessment (Phase 2). The site was found to have elevated levels Benzo-a-Pyrene, are carcinogen and as such will require remediation. 

Site Investigation Bristol

Site Investigation Bristol

Southwest Environmental Limited were commissioned to undertake a reduced scope geo-environment assessment at a site in Bristol. The investigation was retrospective in that construction work had already started.

Bristol City Council  are one of the few council nationally who will accept a reduced scope investigation for geo environmental risk assessment. Ordinarily it is required to take a high frequency of samples even of smaller sites, often including ground gas investigations including deep boreholes which can prove very costly. The cost of such investigations when considering build costs for smaller projects can be approaching 10% of project value, which is some cases in inhibitive.

Below is a panoramic photograph of the site at the time of the investigation. The bedrock has been exposed to some depth by excavations for the foundations. You can clearly see the angle of the bedding and the more coal rich bed to the left of the photograph.

Photograph of Outcrop (or Incrop!)

Just 2 samples were requested by Bristol Site Council. This is a very low number. The samples retrieved showed no exceedances of established “safe” levels. Although Total Organic Carbon Levels in one sample were above those mentioned in CIRIA guidance, likley owing to the presence of coal.

The whole of Bristol is now considered a brown field area. This may seam an overreaction, but SWEL have been surprised by contamination found on “innocent” looking sites in the past. Despite best efforts to categorise a site as low risk without soil sampling it is often the case that if SWEL are pushed to investigate, post Phase 1 Desktop Study will find high levels of some contaminants.

Contaminated Land Advice during Corporate Acquisition

Contaminated Land Advice during Corporate Acquisition

SWEL were approached by a company in Cardiff who were in the process of selling to a large multi national. The purchaser was seeking to drive down the acquisition cost using poor land quality as justification.

SWEL were called in to justify whether this was the case.

The purchasers had engaged their own consultants to establish ground quality, and it was observed that they were acting in line with appropriate guidance.

The land in question although of lowered quality was suitable for end use / continued use and as such the the price should not have been affected.

Contaminated Land Cardiff

Desktop Study – Dunsford, Exeter

Desktop Study – Dunsford, Exeter

A farmer was looking to satisfy various pre-commencement planning conditions listed on his planning approval for an agricultural dwelling in Dunsford near Exeter.

SWEL were not sure why a desktop study was requested as the site was green field . . . although it was adjacent to some existing farm buildings. Discussions with Dartmoor National Park Authority had not resulted in the condition being removed and as such the desktop study was carried out, with the obvious recommendation that conditions relating to contaminated land were discharged.

 Desktop Study Exeter

Contaminated Land Review – Exeter

Acting on instructions from a development company SWEL are to review data relating to the restoration of development site which has seen considerbale quantities of materials imported for use as fill.

Records of imported materials have been well kept and cross referenced with laboratory analysis.

Using our standard generic quantitative assessment methods SWEL are producing a report to assess whether the site is fit for intended use, based on the provided data.

Contaminated Land Consultants Exeter

Contaminated Land Site Investigation – Epsom and Ewell

Southwest Environmental have recent been commissioned to undertake a contaminated land  site investigation within the London borough of Epsom and Ewell. The site investigation was commissioned on Wednesday the 30th April, and work began on the 6th of May. Making for a very prompt start.

I addition to the soil sampling of a car park area, vapour monitoring was also undertaken in the existing building which is ear marked for conversion under the new permitted development rights.

Another riveting photo!

The samples are currently with the labs on a very quick 3 day turnaround meaning the draft (soils only) report will be issued just two weeks after commissioning.

Contaminated Land Site Investigation – Newton Abbot

Southwest Environmental had previously carried out a Phase 1 Contaminated Land Desktop Study for a site in the Teign Valley. The site had been extensively worked as mine over the last 100 years or so, before being developed for residential use, probably around 40 years ago.

Soil sampling was undertaken using hand dug trial pits across the site, with a total of 10 sampling locations. Gas monitoring wells were also installed under the proposed extension foot print, ground water was close to the surface.

Sub soils conditions were varied, bedrock was encountered in the first 1 meter below ground level in some holes, whilst other were fill.

Plan Annotated During Field Work

We are awaiting results from the labs but there were no odorous materials detected during the ground investigation.

Site Investigation Devon