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As part of our SuDS strategies we often recommend soakaways as mitigation for surface water run-off. The feasability of a soakaway at a site needs to be determined prior to installation by undertaking infiltration testing.

Infiltration Testing is a type of field test to determine the infiltration rate of a particular area’s soils and explore the subsurface conditions underneath the soil or pavement surface. The “infiltration rate” refers to the speed at which water enters into the soil.

To do this we excavate a trial hole (typically 1.0m length * 0.5m breadth * 1.5m depth) in an area of ground before filling it with water, in order to calculate the infiltration rate.

This process may seem simple at first, however many sites issues with respect to availability of running water. Even when water is available, a normal tap can take hours to fill the trial hole.

To solve the problem, we have recently acquired a new water bowser and water extraction licence from Thames Water. Our site crew have also been trained in using excavators. As a result, our soakaway test capabilities have grown massively enabling us to undertake more Surface Water Assessments.


test bowser


STM was recently appointed by a concerned home owner who wanted to redevelop his property which is partially located within a functional floodplain in Chertsey. However, the EA informed that the current best available flood modelling of the site was considered to be out of date and therefore insufficient for site specific designs.

STM  were requested to undertake detailed modelling at the site. STM undertook detailed topographical surveying  of the channel and surrounding area and produced a new hydraulic model which showed the flood risk at the site could be adequately managed. The output from the model was also handed over to the EA who were able to use it to update their flood maps.

As part of the works, we provided a level for level, storage for storage compensation scheme. We also undertook soakaway testing in line BRE 365 and provided SuDS recommendations to reduce surface runoff and  recommended flood resilience construction methods to make the development flood resistant.

STM firmly believes in collaboration, understanding and participation between all parties throughout the project. We worked closely with the EA and came up with a flood mitigation and resilience scheme for the new development. The client was over the moon with the works as it saved him from having to construct his finished floor levels at a much higher elevation.


A Client recently contacted us requesting that we carry out a Phase 1 on a Brownfield site which they wished purchase in order to develop residential dwellings.

Although planning permission for the development had been granted, the Local Authority had placed a Contaminated Land Condition requiring Contaminated Land Risk Assessment to be undertaken prior to the commencement of the development.

STM carried out the Phase 1 Report, which identified that the site had previous contaminative uses including  a Builders Yard. The results of the subsequent intrusive site investigation revealed elevated concentrations of Lead and Asbestos in soils in the area that was intended for use as a communal garden. This meant that Remedial works were required in order to render the site suitable for the proposed residential end use.

STM further assisted the Client by undertaking the remedial works, saving them tens of thousands of pounds. As the risk assessment had been conducted pre-purchase, the Client was also to negotiate a reduction in price for the property with the seller.

This case study serves as a stark warning of the dangers of not conducting your Environmental Due Diligence prior to acquisition of any Brownfield property.


Flood Risk Assessments measure the likelihood of flooding within your local area. As well as this, it explores what measures you can take to mitigate when it happens.
The Environment Agency (EA) and Local Lead Flood Authorities (LLFA) are the organisations involved with flooding. They decide which areas are at the highest risk of flooding. They do this using complex computer modelling, based upon historical floods.


After flood-modelling, the EA ranks areas in order of severity. These ranked areas are then mapped, to indicate what areas are at risk of flooding, and what severity the flood risk is. Using the mapped areas, consultants like us, can assess the risk of flooding to your project.
This involves projecting flood risk over time, to determine if your project is vulnerable, as flood risk is likely to increase with time. As well as this, we determine how changes of your development will affect the local area.
There are three levels of Flood Risk Assessment:

  •  A Level 1 FRA involves screening the development to see if a Level 2 FRA is needed.
  •  A Level 2 FRA involves a qualitative assessment of flood risks to the site.
  •  A Level 3 FRA involves a detailed quantitative assessment of flood risks to the site, which may include hydrological and hydraulic modelling

We as consultants, then write a report, which you submit to the Local Authority. Our tailored reports have been honed to ensure the highest level of successful application.


We hope you’ve enjoyed this article. For more information on Flood Risk Assessments, or to request a quote, visit our contact page here!



STM is proud to announce that we have purchased a new Dando drilling rig

The new rig will enable us to complete more complex investigatory works, having been designed specifically for site investigation and environmental analysis. The rig has an ultra-small footprint and crawler mounted design to enable the user to carry out various sampling methods in confined spaces where access is limited.

The staff here at STM are all excited to begin using the new kit, which has already been utilized on some of our more recent site investigations.

tight squeeze rounded


STM is proud to announce that this years User Group Meeting was a successful event.

Having moved towards a predominantly online meeting, we are now looking to host these far more regularly to create greater engagement between our users.

Our next user group webinar is going to be hosted on the 24th November 2017.  


We are always on the look out for talented people with a passion for all things geoenvironmental and a thirst for knowledge. Currently we have roles available for

  • Flood Risk Consultants
  • GeoEnvironmental Consultants
  • GIS and Data Management Specialist

Click here to be taken to Career Opportunities page for further details.


STM were recently requested by an IPPC Company owner (Client) to undertake a Environmental Due Diligence Assessment (EDD) for their operational industrial site. The company, a very successful operational metal works, was due to be sold to foreign investors. The transaction had stalled due to the potential that the land may have been contaminated. As a result the purchaser was reluctant to take the next step.

Read more about this in the Case Study


A developer recently successfully appealed against a Contaminated Land Determination Notice served on him by Walsall Council in respect of a gas works that had been redeveloped to housing in the 1970’s.

In only the second determination by the Secretary of State since the contaminated land regime came into force, this determination shows that Local Authorities need to follow the guidance to the letter when making determinations.

Click here to access the full details of the case on Walsalls homepage.


The framework for setting up the brownfield registers is now firmly in place. The Government recently enacted Regulation 3 of the Town and Country Planning (Brownfield Land Register) Regulations 2017 and published the associated  planning guidance.  In an effort to make development land more easily accessible, Local Authorities have been tasked with the job of maintaining registers of  Brownfield land that they consider to be appropriate for residential development. Local planning authorities (LPA) will be able to trigger a grant of permission in principle for residential development for sites in their registers giving developers and lenders more certainty in their development projects. LPAs need to publish these registers before 31 December 2017.

STM have developed the GeoEnviron Contaminated Land Management System which is essentially a Brownfield Register. Over 85 Local Authorities are  currently using the system. The system was designed to allow Contaminated Land Officers (CLOs) to collate and manage diverse information on previously developed land (land that may be contaminated). The system is fully integrated with GIS and includes a site prioritisation system to allow CLOs to decide which sites need to be further investigated as a matter of priority.

Having been developed over the last 15 years, we believe that the system is ideal for use as Brownfield Register. We will be running a webinar on the Thursday 7th September 2017 at 10.30am to provide an introduction to the system and its capabilities in relation to the Brownfield Registers. You can register for the webinar  using the following link:

Register for Brownfield Register Webinar


Webinars to run through What’s New in GeoEnviron 8.1 have been announced. 

The first of these webinars will take place on Tuesday 18th July to feature a whole host of new features. Join us to learn how to utilise GeoEnviron to its full capacity.

To sign up for the first webinar – click here 


Introducing GeoEnviron 8.1 – a new way of doing things.
For those who have used GeoEnviron before, this software needs no introduction. It’s the only bit of software you need to manage all your environmental assets. 8.1 is efficient and sleek. Designed by environmentalists for environmentalists.

Read the full article here

STM is delighted to announce, as part of our continued expansion, that we’ve moved to the centre of Twickenham.

Our new office is a signal of the growing tide that is STM, and we’re really making waves in the Environmental Consultancy field. Why not join us in the next chapter of our journey?
office new rounded

Read the full article here 


STM Environmental was recently approached by a local council to map out areas of potentially contaminated land within the local region. This project spanning a number of epochs ranging over 200 years involved sifting through old maps with a fine tooth comb in order to pick out sites of potential contamination, ranging from old industrial factories to more modern hospitals.

Read the full article here 


STM was recently approached by Hounslow Council to geo-rectify some aeiral maps of the council district. Hounslow provided a wealth of old aerial photo scans, taken from planes throughout the last few decades, with the task of mosaicking the images so that they alligned with Ordnance Survey MasterMap data.

Getting to know Hounslow from the skies over the years proved to be an interesting project, with well known sites being visible from the aerial photos, such as the old Twickenham Stadium, as shown below!

Read the full article here 


Continued servicing of both the public and private sector. Due to our continued expansion and growth, the STM team feel our new clientele will appreciate the knowledge that our consultancy expertise is being utilized within both the public and private sectors.

Read the full article here


STM was approached to undertake a Flood Risk Assessment and create Surface Water Drainage Strategy for La Reserve Hotel London. The Flood and Drainage team utilized their experience of flood risk within central London and their knowledge of surface water drainage SuDS systems enabled a quick turn-around and allowed for flexibility and alterations to the design and drainage strategy.

 Read the full article here 


Welcome to our new website! We hope you will find it easy to navigate. We are still updating the site  so please let us know if you come across any issues or have any comments or suggestions.


We have recently launched the Landcheck Environmental Search Service as a service for individuals that wish to obtain information on contaminated land, ground stability, Radon and flood risk.

Landcheck has a direct online ordering portal which includes the ability to order searches directly from Local Authorities.

Visit the Landcheck website to find out more….



We would like to extend a warm welcome to the following new Local Authority clients using the STM software:

  • London Borough of Lewisham (Contaminated Land)
  • Selby District Council (Contaminated Land)
  • Durham County Council (LLFA)
  • Kent County Council (LLFA)

This has brought the total number of authorities that we are working with to over 80 across the UK.