Holdfast Training Services Trial Blog

Recently, I have been on the periphery of some environmental work by RPS and I thought it may be vaguely interesting for the blog.

A9 Upgrades – Proof that the sun does shine in Scotland

As part of highway improvement works north of Perth, a Joint Venture of Wills Bros/John Paul is upgrading a 7.5km section of the A9 between Kincraig and Dalraddy.  The scheme passes through the Cairngorms National Park, Alvie SSSI (site of specific scientific interest) and a tributary of the River Spey SAC (special area of conservation).

The project has required the management of numerous protected habitats and species during the construction schedule and RPS has provided Environmental Clerk of Works (ECoW) services.

My involvement has been compiling some reports but I thought it was interesting how much effort was expended on a relatively small contract (value £35m).  The ecological highlights of the project included:

• Translocation of some 45 Hairy Wood Ant nests in collaboration with the Cairngorm National Park Authority. Hairy Wood Ants are included on the Scottish Biodiversity List as a priority species for conservation. They are a key stone species of woodland ecosystems and are threatened through habitat loss.
• Sensitively felling of mature Scot’s pine forestry containing Red Squirrels in consultation with Scottish National Heritage. Red Squirrels are protected both under UK and European legislation.
• Installation and monitoring of Otter fencing surrounding the development to protect this qualifying species of the adjacent River Spey SAC.

RPS ECoW services involved monitoring of compliance with all relevant environmental documents.  In short, RPS was the contractor’s own environmental police.  The environmental element of the project was considered a great success.  The successful translocation of the Hairy Wood Ants was praised by the National Park Authority and the sensitive removal of forestry ensured a negligible impact to the local Red Squirrels population.  Whilst the Otter fencing monitoring gave confidence to SNH that the development caused no likely significant effect to the nearby SAC.

From my cynical perspective it is interesting to note that the effort expended in aid of the environment has been rewarded.  RPS site team have received high praise resulting in a score of 9/10 (“exceptional”) for environmental protection under the Considerate Contractor Scheme.  The benefit of the full time environmental presence was recognised by the stakeholders.  They had confidence that regulations were being followed; the site achieved a very high score for “Protection to the Environment” in the Considerate Contractors audit which rated the site as “Excellent”.

Maybe some of the environmental sustainability initiatives do work?

Monty python-Holy Grail

In my last blog I mentioned building a basement in a swamp. The tender is on a brown field along a tributary of the Brisbane river known as Breakfast Creek.  The site that has recently been cleared (ish).    On my recce I began to feel a sinking sensation in the pit of my stomach.  The ground here is truly awful but, the client is adamant that he wants his basement.

recce-autohaus-findings

Broken heritage wall from old bridge

Looking East on site

Look closely and you will see Skywalker’s X-wing

Design.  The structure is a 6 storey Mercedes show room/car museum with a single storey basement.  The client’s design calls for a temporary retaining wall and then a concrete bath tub to keep it watertight constructed on the inside temp retaining wall.  The structure itself will be supported by pile footings. It was originally tendered as a Traditional construct only package but, due to the risks is now being let as a Design and Build.

Boundary.  Argillite bedrock between -7 and -31  m.  Level of Bedrock varies across the site from -7 m in West to -31 m in the East.

Properties. Very Soft Alluvial Clay φ’ = 25 ° and c’ = 0 until Hard Argillite Rock.

Groundwater.  Tidal range of RL +0 to 2 m (+3.5 m flood level)

Contamination.  You guessed it ASS is back.  With some potential hydrocarbon contamination.

Issues.  The client wants this basement even if it costs him $5 Million.

1. It is a swamp!  It is possible to cantilever 5 m in this rubbish but the toe stability is the problem.  The solution at the moment for sheet and contiguos piles is to have every 3rd pile down to the base rock which can be up to 31 m.
2. The pile loads for earthquake loading are massive.  Brisbane isn’t in a seismic zone but like all building it needs to be design to withstand a basic seismic.  The problem is that because the neighbouring soil isn’t worth a damn the tension loads carried by the pile foundations are over and above what you would expect of a 6 storey building.
3. Hydrostatic slab.  Given the high ground water level, the basement needs to be designed for a hydrostatic slab.  The original design calls for beams to carry this load but, this will be a nighmare for something that cannot achieve a batter of 1:2.
4. Heritage structure.  An existing heritage bridge abutment (not in use) is on the perimeter of the site and it cannot be damaged, despite the fact that it has failed.
5. Existing retaining walls. The client also wants to keep any existing retaining wall structures that have been left in place.  Unfortunately, the existing retaining walls from the previous structure show signs of distress.  It appears that their is disproportionate settlement in at least one part of the retaining wall.  To make matters worse there are no as-builts of the retaining wall structures.

Upside – The hotel where I took this photo does massive steaks and great red wine – so that’s how I spent the afternoon.  If all recces were this good

View South from opposite bank (bar).  Failed heritage abutment on left.  (Note high tide)