Piling strategies

[Steven]

quote:Originally posted by Sparky

Hi Steven,
Not wanting to go off the thread and agreeing mostly with what you write, I am slightly concerned about how an archaeological evaluation can evaluate archaeological deposits without actually excavating them. Sondages don't really tell you much about pits or ditches, can be terribly small and fiddly and sometimes misleading on both urban and rural sites. Furthermore, a characterisation of the achaeology, such as dating material, is required for a decision on mitigation. Perhaps you din't quite mean what I thought you did.

A good example of a bad archaeological approach to the sympathies of piling was an outrageous excavation of the pile-holes...yes the holes...at a monastic site in Lincoln. Don't know what was going through the city archaeologist's head; the requirements of the council to develop cheaply, maybe...?

Who is 'Cornflake Man'?

Cheers
S

Hi Sparky
I'll start with your last question, first, Cornflake man is what people call an engineer who has given two papers at Preservation of Archaeological Remains In-Situ conferences 2 & 3, which concern the impact of foundations on archaeological deposits. Unfortunately I can't remember this chaps real name, sorry.

In terms of what I meant by evaluation strategy. Lets take an example, a trench in an urban site which the stratigraphy is natural with cut features, sealed by a cultural deposit also cut through by features, sealed by a further cultural deposit also cut through. In the evaluation you would sample excavate some of the cut features in the top layer (thereby dating etc them), perhaps take an enviro sample from the top layer Hopefully then you would know about the underlying layer from observations whilst excavating the cut features. So in order to assess these underlying layers/features you would either dig a sondage to sample underlying strat or find an appropriate feature which cuts all the way through to natural so giving you an idea of the charater of underlying archaeology. In almost all evals I like to see a deep hole somewhere in at least one trench to ensure all layers etc have been assessed.

I think that you assumed I meant no investigation of features within trenches didn't you, hopefully the above concurs with your basic strategy.

Unfortunately I have also had to deal with piling impact with a flexible strategy, if you want details you'll have to get Hosty to email me your email or something so we can talk off this forum and still preserve our secret identities :face-huh:.

Anna,
That's a fair point, but 25m deep piles tend to have a rather serious impact on waterlogged material both within the development area and on adjacent sites as they act like sumps. However, not dealing with the actual threatened site in order to preserve possible adjacent sites is not really a solution. There are ways of bunding a site after excavation to avoid water loss from surrounding areas.

Steven

[Sparky]

Hi Steven,
Yep. I didn't think you meant what I initially thought you did. Glad to know it.
S

[beamo]

Stephen

Many thanks for the response - it deals directly with one of the questions that I asked in my initial post, i.e. is the 'acceptable loss' regarded as acceptable if unrecorded, or acceptable but only if recorded? Clearly in your view it is the former - I am still interested to know other peoples views on this.


I went to the two London PARIS conferences but not the Amsterdam one - don't know who 'cornflake man' is - perhaps Mat Davis of Hunting Technical Services.


Beamo

[Anna Stocks]

Thanks for the response Stephen. I don't doubt piles have a signficant impact on waterlogging as well - I was merely trying to flag up that the impact of excavation on waterlogged deposits has to be considered when devising a mitigation strategy, and that it isn't as risk free as perhaps it is sometimes considered. I certainly wasn't trying to sugest that "not dealing with the actual threatened site in order to preserve possible adjacent sites" was a appropriate strategy!

Anna

[Steven]

quote:Originally posted by Anna Stocks

Thanks for the response Stephen. I don't doubt piles have a signficant impact on waterlogging as well - I was merely trying to flag up that the impact of excavation on waterlogged deposits has to be considered when devising a mitigation strategy, and that it isn't as risk free as perhaps it is sometimes considered. I certainly wasn't trying to sugest that "not dealing with the actual threatened site in order to preserve possible adjacent sites" was a appropriate strategy!

Anna

Anna
Sorry [:0]

Steven

[mercenary]

It was no surprise that the recent EH piling guidance fell short of endorsing the Arup 5% loss concept. Many of us who do work in York have come to hate this particular bit of oft quoted Guidance. There even appears to be a growing acceptance of the problems with the practicalities, if not the theory, of preservation In-situ among EH types.

I agree wholeheartedly with Historic building that the problem with piling is the removal of obstructions. This is quite often done with no archaeological monitoring, and covers a much larger area than the pile positions. This can be mechanical excavation to natural along all pile lines. In the worst case I have seen the financial incentives/penalties to remove all obstructions (in this case all masonry and rubble bigger than a brick) were such that the contractors repeatedly ignored threats of enforcement action by the curator. This activity would have gone unobserved had archaeologists not been called out to record other remains on the site. My suspicion is that this activity goes on unobserved on many sites.

Archaeological excavation around pile positions or lines may be a limited way of understanding a site, but surely it is better than the undocumented destruction that seems to happen on top of the "acceptable loss" percentage of the piles themselves?

I'm also reminded of the horrific scene witnessed by a friend in York where a screw pile caught a waterlogged timber and spun it through a few metres of strat to the surface.

[BAJR Host]

How did this one go?

"I don't have an archaeological imagination.."
Borekickers

[beamo]

Discussion still on-going


Beamo

[oldgirl]

The client wants to let out the piling contract as a traditional Design & Build, whereas I would see the piling layout as being driven more through a series of pre-designed layouts aimed at minimising the impact on the archaeological deposits. Does anyone have any recent experience in understanding how piling is procured on sites where archaeology is critical?

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I've had two sites recently where there were areas which were considered to be 'nationally important'. In one case we have avoided that area completely (we managed to convince the client that if they wanted to go ahead rapidly in this then the fastest and cheapest way would be to avoid the serious archaeology altogether). On the other one the piling has been designed in advance and will be some distance from the remains and 'bridge' over them. In both cases, however, we had to undertake limited evaluation/excavation in order to define the nature, location and preservation of the remains.

It sounds like you have a more lmitied space to work in though?