Cawdor geology report - a summary
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Dic Dastardly
Dec 14, 2009, 6:05:02 AM12/14/09
to Newcastle Emlyn Action Group
I spent about 3 hours last night ploughing through the geological
survey which accompanies the application. It's quite complicated
stuff, and the company which did it seems to have done a professional
job. However....
The history of the site is interesting, and there are some
uncertainties about it.
The tannery is believed to have been in use up to about 1940, and it
was located roughly where the showrooms are now. They took some soil
samples from just behind the existing showrooms (obviously they could
not dig into the existing floor), and the results were negative, with
no signs of hides, carcasses or anthrax spores. Presumably, however,
they would only know for certain when it's possible to dig on the site
occupied by the showrooms.
The site itself is crossed by a stream, which runs roughly diagonally
under the showrooms across to the car park. The stream is believed to
have been filled in in stages, and in some places they estimate over 6
metres of in-fill (mainly building rubble)!
Cawdor staff, who were some of the main informants, said they believed
the stream ran in a culvert, and the surveyors accepted this, but no
evidence was found. Where the culvert would be expected to exit on the
slope going down to the riverbank, they found water emerging, but no
signs of a culvert, which they believe may have disappeared as a
result of land slippage.
This is one of the things which makes the site very unstable, and the
public car park is apparently the most unstable part of the whole
site. The surveyors believe that water from the stream may not be
running properly through the supposed culvert, and that an underground
reservoir of water has built up under the site.
This was one of the main factors which made drilling very difficult.
The surveyors were unable to complete drilling of their test boreholes
because of the wet, unstable conditions.
The main conclusions are as follows:
1. Contamination - from the limited testing done, they did not find
high levels of contamination, although there was some caused by
leakage from the petrol station's tanks. They did not look for
evidence of a rubbish dump, and did not seem to find any evidence.
However, interestingly they noted that an old aerial photograph from
the 1950s/1960's showed a large area of what looked like recently
introduced landfill. Could that have been the bulldozing of the
rubbish dump?
2. A lot of work will be required to stabilise the N.E. corner (i.e.
the car park), with the slope being shored up by revetments, etc. More
worryingly, they conclude that a great deal of pile driving will be
needed for the supermarket itself. They looked at different ways of
doing this, but concluded that the best way would be to drive piles
down 20+ metres into the bedrock. They acknowledge that this will need
to be done very carefully in order to prevent damage to surrounding
buildings.
I will ask a retired geologist I know if he would take a look at this
for us, because there are very likely things which a layman would not
pick up. What does seem certain, however, is that if and when a
supermarket is built, it will be a very expensive place to build on.
survey which accompanies the application. It's quite complicated
stuff, and the company which did it seems to have done a professional
job. However....
The history of the site is interesting, and there are some
uncertainties about it.
The tannery is believed to have been in use up to about 1940, and it
was located roughly where the showrooms are now. They took some soil
samples from just behind the existing showrooms (obviously they could
not dig into the existing floor), and the results were negative, with
no signs of hides, carcasses or anthrax spores. Presumably, however,
they would only know for certain when it's possible to dig on the site
occupied by the showrooms.
The site itself is crossed by a stream, which runs roughly diagonally
under the showrooms across to the car park. The stream is believed to
have been filled in in stages, and in some places they estimate over 6
metres of in-fill (mainly building rubble)!
Cawdor staff, who were some of the main informants, said they believed
the stream ran in a culvert, and the surveyors accepted this, but no
evidence was found. Where the culvert would be expected to exit on the
slope going down to the riverbank, they found water emerging, but no
signs of a culvert, which they believe may have disappeared as a
result of land slippage.
This is one of the things which makes the site very unstable, and the
public car park is apparently the most unstable part of the whole
site. The surveyors believe that water from the stream may not be
running properly through the supposed culvert, and that an underground
reservoir of water has built up under the site.
This was one of the main factors which made drilling very difficult.
The surveyors were unable to complete drilling of their test boreholes
because of the wet, unstable conditions.
The main conclusions are as follows:
1. Contamination - from the limited testing done, they did not find
high levels of contamination, although there was some caused by
leakage from the petrol station's tanks. They did not look for
evidence of a rubbish dump, and did not seem to find any evidence.
However, interestingly they noted that an old aerial photograph from
the 1950s/1960's showed a large area of what looked like recently
introduced landfill. Could that have been the bulldozing of the
rubbish dump?
2. A lot of work will be required to stabilise the N.E. corner (i.e.
the car park), with the slope being shored up by revetments, etc. More
worryingly, they conclude that a great deal of pile driving will be
needed for the supermarket itself. They looked at different ways of
doing this, but concluded that the best way would be to drive piles
down 20+ metres into the bedrock. They acknowledge that this will need
to be done very carefully in order to prevent damage to surrounding
buildings.
I will ask a retired geologist I know if he would take a look at this
for us, because there are very likely things which a layman would not
pick up. What does seem certain, however, is that if and when a
supermarket is built, it will be a very expensive place to build on.
Jeremy Clulow
Jan 4, 2010, 6:49:22 PM1/4/10
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