A day in the life of a GRM Geotechnical Engineer

Today I am undertaking an intrusive investigation on a former Garden Nursery. The project is for a nationwide housing developer, who is looking to buy the land to build 75 houses. It's obviously going to be a costly project, so they've employed GRM to investigate the site before the sale goes through, to make sure it's suitable for what they have in mind.

The previous days leading up to the ground investigation I spent time looking at historical Ordnance Survey maps, to see what changes have occurred to the site from the late 1800's. The historic maps revealed a former railway cutting adjacent to the site to have been backfilled. The environmental report for the area indicates it to be a BGS recorded landfill site. This highlights a possibility for the migration of landfill gas to the site. A check of the geological map for the area confirms this may occur as the site is underlain by a superficial deposit of Glacial Till overlying a solid geology of the Middle Lias. We've got maps in the office specifically for this, covering the whole country. The Middle Lias is described as comprising mudstone, siltstone and thin limestone beds. The limestone beds are considered to be of concern as they are normally fractured and therefore, may be a pathway for the migration of landfill gas. This indicates that the site will require gas monitoring standpipes to be installed across the site. The site is not in a mining area, so there are no shafts or workings to worry about. The environmental report indicates the site will require Radon protection due to the geology, no further environmental hazards from natural or local factories/businesses are shown to be of concern to the site. While I'm in the office I have to gather as much information as possible to help me while I'm on site, and I call on all kinds of sources and databases in order to find out. It's amazing what information we've got access to.

The previous week I conducted a site walkover, a portion of the site was noted to be covered by a Christmas tree plantation. This area was to be investigated, however, a local bird society indicated that there were nesting birds, so this will have to be investigated at a later date. It's surprising what can disrupt plans for investigation and development and needs to be checked out during the site walkover i.e. badgers, great crested newts, Japanese knotweed etc. There's more to site investigation work than just geology!

We've had people working on this project for a week or so now, so it's drawing to a close. Tomorrow afternoon I'll have a meeting with some colleagues to discuss our findings, and we'll draw up a report of hazards and potential risks detected, and list our recommendations - things that need to be done before the client can proceed with the planned development. The client can then make an accurate assessment of the costs involved and determine whether they think it's worth it. If they decide to go ahead, GRM will be involved in providing solutions to the problems identified, and also providing structural engineering services.

Environmental concerns noted at the site were two unbunded heating oil tanks used for the residential house and green houses, together with a underground septic tanks.

Armed with this information site specific areas were targeted for intrusive investigation in addition to a general spread of the site to obtain as much geotechnical information as possible for the proposed development.

The day starts well with all the trial pits excavated following the anticipated geology from the BGS maps. No limestone was encountered, which is a good sign, as the cohesive strata will impede the migration of any potential landfill gas from the adjacent landfill. However, gas monitoring standpipes were installed to determine the ground gas regime across the site.

Ground contaminated with hydrocarbons was encountered adjacent to the heating oil tanks, samples were taken for analysis as further work can be expected. At around dinner time the heavens opened up with a heavy snow fall, but this does not deter the work in hand as it's just part of the job, it's not all sunshine and shorts.

The next day the trial hole logs are written up on to a computer program. Samples are decided upon to send for laboratory analysis, to give a representative spread across the site and to determine geotechnical properties and potential contaminates within the soil. After a couple of weeks the results come back and the report can be finalised with all the hazards and potential risks detected and assessed we can list our recommendations. The client can then make a budgetary assessment of the costs involved and determine whether they think its worth it. If they go ahead, GRM will be involved in providing more accurate design solutions, and can also provide structural engineering services.

Head Office

South Midlands Office

A day in the life of a GRM Geotechnical Engineer