Dover Rural...Texas East Kent UK.?
- 29 October 2013 09:18250514Some info about the sinking of the Stonehall colliery shafts from a 1960s book -
- 29 October 2013 14:10250537Another one Ray and there are many more in the objection letters...
http://qjegh.lyellcollection.org/content/13/2/105.abstract - 29 October 2013 18:23250549At last Reg - something real. I trust that you are aware of the later papers as well, the one you posted was written and published in 1980. There are far more recent papers that show contamination levels in the aquifer back to near natural since the end of mining activity in our area. But, as I have consistently written, mistakes were made with our water during the mining era and we need to be sure that they will not be repeated.
- 29 October 2013 19:36250554Neil your Flaffing...your research is wanting to say the least...just another for you to chew on..
Tracas and Modelling in Hydrogeology (Proceedings of the TraM '2000 Conference
held at Liège, Belgium, May 2000). IAHS Publ. no. 262, 2000. 347
Measurements and models of solute behaviour in
the dual-porosity Chalk aquifer of the UK: the
applicability of tracer tests
SALLY WATSON, WILLIAM BURGESS, JOHN BARKER
Groundwater Tracing Unit, Hydrogeology' Group, Department of Geological Sciences,
University College London, Gower Street, London WC1E 6BT, UK
e-mail: sally.watson@ucl.ac.uk
JULIO CARNEIRO
Universidade de Evora, Dep. Geociências, Col. Luis Verney, Apartado 94,
7002-554 Evora Codex, Portugal
SARA HAZELL
Dames & Moore, Wimbledon, London SW19 4DR, UK
Abstract Tracer tests provide direct observations of solute transport in
groundwater, but how relevant are small-scale tests to the prediction of longterm
behaviour of contaminants in a dual-porosity aquifer? To address this
question for the Chalk aquifer of the UK, a catchment at Tilmanstone
(southeast England) is being investigated; disposal of coalfield brine directly
to the Chalk aquifer took place over many decades and a large plume of
contamination has developed. Transport properties of the Chalk are being
established across a range of space and time scales. Results of laboratory-scale
diffusion experiments, single-borehole dilution tests, and borehole-to-borehole
tracer tests in the Chalk are reviewed in the context of observations of chloride
flux through the Eastry valley at Tilmanstone over several decades. Modelling
of groundwater flow and chloride transport, using a dual-porosity framework,
provides both the context and the criteria for judging the applicability of the
field-scale tracer tests.
INTRODUCTION
Groundwater-mediated solute transport in fractured porous media is dominated by advection
in fractures and diffusive exchange between fracture water and the matrix pore water (e.g.
Barker, 1993), their relative significance depending on the scale and duration of transport.
Limited knowledge of the complexity of aquifer properties and flow geometry severely
restricts our ability to predict solute migration at the field scale. Tracer tests have the
advantage of revealing aquifer transport characteristics directly, but there is a discrepancy
between the scales and durations of practicable tracer tests and of contaminant plumes.
To address this issue, we present observations at various scales of solute transport
in the Chalk aquifer, the epitome of the dual-porosity aquifer. We concentrate on the
Tilmanstone catchment in Kent, southeast England, where disposal of coalfield brine
in open lagoons over many decades has resulted in a large plume of contamination of
over 25 km2 in area (Fig. 1). Results of historical reviews and field investigations in
the 1970s (Ffeadworth et al, 1980) and predictions of an early model (Bibby, 1981),
form the basis for our current research.
348 Sally Watson et al.
^ D i s c h a r g e lagoon ©Town o 4km
y- Stream
"150 Chloride concentration mg/l (1994)
Fig. 1 Site location , indicating the extent of the saline plume.
The Tilmanstone catchment
A number of deep coalmines were active in southeast Kent from the early 1900s until
final closure in 1986. The Tilmanstone mine is situated at the head of a valley in the
Upper Chalk, which dips to the northeast and drains to springs in the northeast (Fig. 1).
The hydraulic gradient along the valley is approximately 0.008.
Brine pumped from the deep coalfield was discharged to unlined lagoons on the
Chalk surface at the head of the valley between 1906 and 1974. Flow rates and
chloride concentration increased from 1.4 Ml day"1 and 45 mg l"1 in 1906 to
11.8 Ml day"1 and over 2000 mg l"1 in 1958; thereafter the flow remained approximately
steady as the concentration increased further to 5200 mg l"1. About 190 Mm3
of brine, close to 320 x 106 kg of chloride, entered the Chalk aquifer over a 68 year
period. The resultant contaminant plume provides an opportunity to test the value of
tracer tests at different scales in predicting the long term plume development.
OBSERVATIONS OF CHLORIDE MOVEMENT IN THE CHALK
Catchment-scale chloride transport
The background chloride content of the Chalk aquifer is low: 30-40 mg l"1. By 1929,
chloride had reached 200 mgl"1 immediately to the north of the mine. By 1949 the
maximum chloride concentration in the aquifer was 900 mg l"1. By 1977, groundwater
chloride concentration had increased to 5000 mg l"1 within 1000 m of the lagoons, and
1000 mg l"1 at Eastry (Fig. 2). The aquifer was considered polluted over an area of
27 Ion", the plume being 8 km long in the direction of the valley and 2 to 5 km wide.
Headworth et al. (1980) estimated that 98 x 106 kg of chloride (30% of the total load),
had been discharged at the springs by the early 1970s. A fairly steady concentration of
slightly above 200 mg l"1 corresponds to an annual flux of 2-3 x 106 kg of chloride to
the streams since then. Since 1977 the centre of the plume has moved 2 km down the
Measurements and models of solute behaviour in the dual-porosity Chalk aquifer of the UK 349
SW NE
Tilmanstone
settling lagoons
Lower Venson ^
Farm E a s t rV
\1000 f..._2I>be „_,.____, ^
~ I 1 ™ / ; ; / -»
d o o '• I / :
- - i ~ f- Y
» - —JQQ. -
V * - : —
Key
Lined borehole
Unlined borehole
Borehole ID numbers
Porewater chloride (mg/l)
Fissure water chloride (mg/l)
\ 5 0 0
••-,200
Scale
1
500
20
- 10
- 0 S
•150
metres
0 250 _
metres
Fig. 2 Extent of contamination (1974) with pore water and fissure water profiling (after
H e a d w o r d s a/., 1980).
valley and the maximum chloride content (in pumped groundwater) has declined to
1500 mgl"1 , yet the total extent of pollution, as defined by the 150 mg F1 contour
(Fig. 1), has expanded, (Peedell, 1994; Ffazell, 1998).
A chloride pore water profile determined in 1999 (Fig. 3) suggests that the active
fractures are quite closely spaced, since the profile is locally smooth. The low
CI concentration mg/l
0 500 1000 1500
•
1
•
1 *
* t
•
Fig. 3 Chloride pore water profile 1999. Data collected as part of EU FRACFLOW
project (www.fracflow.dk) by British Geological Survey.
350 Sally Watson et al.
concentrations between 45 and 58 m b.g.l. and below 80 m b.g.l, at which depths bulk
permeability is low (Fig. 4), indicate that less chloride was transported into these zones.
Permeability variation with elevation EastryBHA
Permeability m/d
0 20 40 60 80 100 120
E
TO
Q
-20
S -30
<
E
i X
MX.
f•• • i
x A A
A à •- *
• 1
A
A K A
A X
•f
°n
®BH3
• BH4
ABH5
*BHA
ABH8
OBH7
I
Ct-Cb/Co-Cb
0 1
-50
/ .7
/ ,•;
- i - . . . -'-.\
" - \ - n.
\\ vw
/ 4
\ tj
\ v
Minutes since start
• 45
-165
915
Fig. 4 Single borehole dilution test results.
Borehole-to-borehole tracer tests
Natural-gradient borehole-to-borehole tracer tests are currently underway at the site.
Such tests provide information most effectively at the intermediate scale (Ward et al.,
1998), where the significance of diffusion depends on the distances between the
boreholes and the characteristics of the rock. For tracer residence times of a few
minutes, diffusion is negligible. The tracer test reveals the kinematic porosity of the
fractures but nothing about the matrix. For tracer residence times of a few hours, there
will be time for diffusion of a few millimetres into the matrix, which is significant in
comparison to the fracture apertures. The test will reveal behaviour characterized by
the fracture porosity and the area for diffusive exchange which is only significant
during early plume development. Where channelling is important the effective
apertures may be of the order of 1 cm and diffusion will have less effect. It is unlikely
that borehole-to-borehole tracer tests will provide suitable information to assess
pollutant transport over distances of kilometres and time scales of years or decades.
Single-borehole dilution tests
Interval dilution tracer tests can yield vertical profiles of the Darcy velocity of
groundwater flow (e.g. Hazell, 1998). With knowledge of the local groundwater head
Measurements and models of solute behaviour in the dual-porosity Chalk aquifer of the UK 351
gradient these can be interpreted as profiles of hydraulic conductivity which are more
appropriate for solute transport modelling than values from pumping tests, as they
involve smaller volumes of aquifer. Dilution tests at six boreholes at Tilmanstone
(Fig. 4) show that the Chalk becomes more permeable down-valley, and a marked
reduction in hydraulic conductivity is evident at a depth of 40 m. Our results show
considerably more detail than previous pumping tests and are consistent with
geophysical logs, which confirm a greater degree of fracturing in the upper 40 m.
Laboratory scale diffusion experiments
Diffusive exchange occurs between matrix pore water and mobile groundwater in
fractures and fissures at the sub-metre scale: the kinematic porosity, fracture and
matrix porosities, and the diffusion coefficient of the saturated matrix are the key
parameters (Barker et al, 2000; Fretwell et al, 2000). Diffusion coefficients for
chloride in the Chalk of southern England, summarized in Fretwell (1999), range from
5.2 x 10"11 to 1.3 x 10 - 9mV, but none relate specifically to Tilmanstone. Tests are
being conducted on recently acquired core material.
MODELLING CHLORIDE FLUX IN THE TILMANSTONE VALLEY
A finite-element dual-porosity model, calibrated against the field observations up to
and including the surveys of the 1970s, was developed by Bibby (1981). Transport was
described according to a parallel plate representation, and diffusion within the matrix
water was described by Fick's second law. The model was two-dimensional, it ignored
density effects, and transmissivity and storativity were independent of saturated
thickness. It was probably the first catchment-scale dual-porosity model applied to a
groundwater contamination incident.
The Bibby model predicted the future development of the plume, the chloride
concentration at the Eastry borehole (Fig. 5) and of the springs, and the flux of chloride
from the springs up to the year 2008. However, the parameters of the calibrated
transport model were far from realistic (Carneiro, 1996), and the aquifer is
rehabilitating at a rate considerably slower than the model predicted. The effects of the
seasonal desaturation of fractures (Fretwell et al, 2000), accentuated by droughts, and
1600
1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060
Year;
[ Model prediction •» Field data |
Fig. 5 Comparison of 1970s numerical model predictions and recent field data.
352 Sally Watson et al.
the three-dimensionality of the plume due to density effects, aquifer heterogeneity and
vertical hydraulic gradients, are considered the most likely causes of discrepancy.
A new model of chloride transport in the Eastry valley is being developed that will
incorporate these features, and include recent pore water chloride profiles and tracer
test results in its calibration and validation. The model will be used to assess the value
both of the tracer tests and of the various observations of plume development, in
making predictions.
We anticipate a particular challenge will be to make predictions on time scales
which are intermediate between those of tracer tests (weeks) and plume development
(decades).
Acknowledgements A Research grant from the Natural Environment Research
Council (no. GST/2/1811) under the DAEC/Envirorrmental Diagnostics Programme is
gratefully acknowledged. The matrix chloride profile illustrated in Fig. 3 resulted from
collaboration with the British Geological Survey, working on the EU FRACFLOW
project (www.ffacflow.dk), which is also gratefully acknowledged. - Brian Dixon
- Location: Dover
- Registered: 23 Sep 2008
- Posts: 23,940
29 October 2013 19:40250555reg,that makes you sound desperate.can you post something that people can read and understand.cheers.
- 29 October 2013 19:47250556thanks for that reg i hadn't realised the issue was so simple and easy to understand.
others try to confuse us with a load of geological stuff which goes over most of our heads. - 29 October 2013 20:00250557Howard there is so much evidence against drilling in our neck of the woods to prove our water is in danger
and the Environment Agency has it all....as they did on the ``Maison Dieu site ``............ - 29 October 2013 20:09250559Its cut and paste gone mad !
- 29 October 2013 20:16250561So Reg having read, digested and analysed that long piece you posted up what, in your opinion, are the most pertinent aspects of the report and it's impact on the proposed drilling in the area?
- 29 October 2013 20:19250562Serves you right Barrie.......
You said...
..``So I thought I'd check the websites of the local villages, and they have lost all credibility,
and the sensationalism is going to let the exploration company walk straight in because
there are no sensible objections.``
Do you want some more? - 29 October 2013 20:58250563For those that are unfamiliar with Flicks Law.
Fick's first law relates the diffusive flux to the concentration under the assumption of steady state. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative). In one (spatial) dimension, the law is
\bigg. J = - D \frac{\partial \phi}{\partial x} \bigg.
where
J is the "diffusion flux" [(amount of substance) per unit area per unit time], example (\tfrac{\mathrm{mol}}{ \mathrm m^2\cdot \mathrm s}). J measures the amount of substance that will flow through a small area during a small time interval.
\, D is the diffusion coefficient or diffusivity in dimensions of [length2 time−1], example (\tfrac{\mathrm m^2}{\mathrm s})
\, \phi (for ideal mixtures) is the concentration in dimensions of [amount of substance per unit volume], example (\tfrac{\mathrm {mol}}{\mathrm m^3})
\, x is the position [length], example \,\mathrm m
\, D is proportional to the squared velocity of the diffusing particles, which depends on the temperature, viscosity of the fluid and the size of the particles according to the Stokes-Einstein relation. In dilute aqueous solutions the diffusion coefficients of most ions are similar and have values that at room temperature are in the range of 0.6x10−9 to 2x10−9 m2/s. For biological molecules the diffusion coefficients normally range from 10−11 to 10−10 m2/s.
In two or more dimensions we must use \nabla, the del or gradient operator, which generalises the first derivative, obtaining
\mathbf{J}=- D\nabla \phi .
The driving force for the one-dimensional diffusion is the quantity - \frac{\partial \phi}{\partial x} which for ideal mixtures is the concentration gradient. In chemical systems other than ideal solutions or mixtures, the driving force for diffusion of each species is the gradient of chemical potential of this species. Then Fick's first law (one-dimensional case) can be written as:
J_i = - \frac{D c_i}{RT} \frac{\partial \mu_i}{\partial x}
where the index i denotes the ith species, c is the concentration (mol/m3), R is the universal gas constant (J/(K mol)), T is the absolute temperature (K), and μ is the chemical potential (J/mol).
If the primary variable is mass fraction (y_i, given, for example, in \tfrac{\mathrm kg}{\mathrm kg}), then the equation changes to:
J_i=- \rho D\nabla y_i
where \rho is the fluid density (for example, in \tfrac{\mathrm kg}{\mathrm m^3}). Note that the density is outside the gradient operator.
Fick's second law[edit]
Fick's second law predicts how diffusion causes the concentration to change with time:
\frac{\partial \phi}{\partial t} = D\,\frac{\partial^2 \phi}{\partial x^2}\,\!
where
\,\phi is the concentration in dimensions of [(amount of substance) length−3], example (\tfrac{\mathrm{mol}}{m^3})
\, t is time [s]
\, D is the diffusion coefficient in dimensions of [length2 time−1], example (\tfrac{m^2}{s})
\, x is the position [length], example \,m
It can be derived from Fick's First law and the mass conservation in absence of any chemical reactions:
\frac{\partial \phi}{\partial t} +\,\frac{\partial}{\partial x}\,J = 0\Rightarrow\frac{\partial \phi}{\partial t} -\frac{\partial}{\partial x}\bigg(\,D\,\frac{\partial}{\partial x}\phi\,\bigg)\,=0\!
Assuming the diffusion coefficient D to be a constant we can exchange the orders of the differentiation and multiply by the constant:
\frac{\partial}{\partial x}\bigg(\,D\,\frac{\partial}{\partial x} \phi\,\bigg) = D\,\frac{\partial}{\partial x} \frac{\partial}{\partial x} \,\phi = D\,\frac{\partial^2\phi}{\partial x^2}
and, thus, receive the form of the Fick's equations as was stated above.
For the case of diffusion in two or more dimensions Fick's Second Law becomes
\frac{\partial \phi}{\partial t} = D\,\nabla^2\,\phi\,\!,
which is analogous to the heat equation.
If the diffusion coefficient is not a constant, but depends upon the coordinate and/or concentration, Fick's Second Law yields
\frac{\partial \phi}{\partial t} = \nabla \cdot (\,D\,\nabla\,\phi\,)\,\!
An important example is the case where \,\phi is at a steady state, i.e. the concentration does not change by time, so that the left part of the above equation is identically zero. In one dimension with constant \, D, the solution for the concentration will be a linear change of concentrations along \, x. In two or more dimensions we obtain
\nabla^2\,\phi =0\!
which is Laplace's equation, the solutions to which are called harmonic functions by mathematicians.
Example solution in one dimension: diffusion length[edit]
A simple case of diffusion with time t in one dimension (taken as the x-axis) from a boundary located at position x=0, where the concentration is maintained at a value n_0 is
n \left(x,t \right)=n_0 \mathrm{erfc} \left( \frac{x}{2\sqrt{Dt}}\right).
where erfc is the complementary error function. This is the case when corrosive gases diffuse through the oxidative layer towards the metal surface (if we assume that concentration of gases in the environment is constant and the diffusion space (i. e., corrosion product layer) is semi-infinite - starting at 0 at the surface and spreading infinitely deep in the material). If, in its turn, the diffusion space is infinite (lasting both through the layer with n\left(x,0\right) = 0, x >0 and that with n\left(x,0\right) = n_0, x \le 0 ), then the solution is amended only with coefficient ½ in front of n0 (this might seem obvious, as the diffusion now occurs in both directions). This case is valid when some solution with concentration n0 is put in contact with a layer of pure solvent. (Bokshtein, 2005) The length 2\sqrt{Dt} is called the diffusion length and provides a measure of how far the concentration has propagated in the x-direction by diffusion in time t (Bird, 1976).
As a quick approximation of the error function, the first 2 terms of the Taylor series can be used:
n \left(x,t \right)=n_0 \left[ 1 - 2 \left(\frac{x}{2\sqrt{Dt\pi}}\right) \right]
If D is time-dependent, the diffusion length becomes 2\sqrt{\int_0^{t'}D(t')dt'} . This idea is useful for estimating a diffusion length over a heating and cooling cycle, where D varies with temperature.
Generalizations[edit]
1. In the inhomogeneous media, the diffusion coefficient varies in space, D=D(x). This dependence does not affect Fick's first law but the second law changes:
\frac{\partial \phi(x,t)}{\partial t}=\nabla\cdot (D(x) \nabla \phi(x,t))=D(x) \Delta \phi(x,t)+\sum_{i=1}^3 \frac{\partial D(x)}{\partial x_i} \frac{\partial \phi(x,t)}{\partial x_i}\
2. In the anisotropic media, the diffusion coefficient depends on the direction. It is a symmetric tensor D=D_{ij}. Fick's first law changes to
J=-D \nabla \phi \ , \mbox{ it is the product of a tensor and a vector: } \;\; J_i=-\sum_{j=1}^3D_{ij} \frac{\partial \phi}{\partial x_j} \ .
For the diffusion equation this formula gives
\frac{\partial \phi(x,t)}{\partial t}=\nabla\cdot (D \nabla \phi(x,t))=\sum_{j=1}^3D_{ij} \frac{\partial^2 \phi(x,t)}{\partial x_i \partial x_j}\ .
The symmetric matrix of diffusion coefficients D_{ij} should be positive definite. It is needed to make the right hand side operator elliptic.
3. For the inhomogeneous anisotropic media these two forms of the diffusion equation should be combined in
\frac{\partial \phi(x,t)}{\partial t}=\nabla\cdot (D(x) \nabla \phi(x,t))=\sum_{i,j=1}^3\left(D_{ij}(x) \frac{\partial^2 \phi(x,t)}{\partial x_i \partial x_j}+ \frac{\partial D_{ij}(x)}{\partial x_i } \frac{\partial \phi(x,t)}{\partial x_j}\right)\ .
4. The approach based on the Einstein's mobility and Teorell formula gives the following generalization of Fick's equation for the multicomponent diffusion of the perfect components:
\frac{\partial \phi_i}{\partial t} =\sum_j {\rm div}\left(D_{ij} \frac{\phi_i}{\phi_j} {\rm grad} \, \phi_j\right) \, .
where \phi_i are concentrations of the components and D_{ij} is the matrix of coefficients. Here, indexes i,j are related to the various components and not to the space coordinates.
The Chapman-Enskog formulas for diffusion in gases include exactly the same terms. It should be stressed that these physical models of diffusion are different from the toy-models \partial_t \phi_i = \sum_j D_{ij} \Delta \phi_j which are valid for very small deviations from the uniform equilibrium. Earlier, such terms were introduced in the Maxwell-Stefan diffusion equation.
For anisotropic multicomponent diffusion coefficients one needs 4-index quantities, for example, D_{ij\, \alpha \beta}, where i, j are related to the components and α, β=1,2,3 correspond to the space coordinates.
Sorry I could not help myself.
Serious question.
Reg/ Neil.
You are both right to state that mine water has caused saline contamination to our aquifers but is there any evidence that it has been harmful to humans?"My New Year's Resolution, is to try and emulate Marek's level of chilled out, thoughtfulness and humour towards other forumites and not lose my decorum" - 29 October 2013 21:15250565Just so you can make sense of Reg's c&p, here's the original synopsis of the research paper he cites.
http://ks360352.kimsufi.com/redbooks/a262/iahs_262_0347.pdfI'm an optimist. But I'm an optimist who takes my raincoat - Harold Wilson - 29 October 2013 21:31250569GaryC, Flick's law is all well and good but relates only to diffusion whereas much of the water transit through the aquifer is due to percolation or flow through fractures in the chalk and other strata. The maximum concentration of chlorides is noted in Reg's article as 5000 mg/litre. A dessertspoon of salt contains about that amount of chloride. That's how much you salt the water when you cook pasta.
From the various scholarly articles I have read, it's clear that the scientific community is by no means united. So it's hardly surprising that we don't have a consensus on here.
Just reflect on the fact that if new drilling does pollute the aquifer, we shan't know for ten years and it will take another fifty years to fix. The key seems to be removal from the site of the saline waste water, as the cause of the pollution from coal mining was the brine lagoons. It's unlikely that test drilling per se will cause fresh pollution.I'm an optimist. But I'm an optimist who takes my raincoat - Harold Wilson - 29 October 2013 21:36250571Interestingly (or cynically!), one of the report authors Reg cites gives her affiliation as Dames and Moore, who in 1999 were absorbed into this corporation - http://www.urscorp.com/
I wonder why they were interested in lil' old Kent. - Keith Sansum1
- Location: london
- Registered: 25 Aug 2010
- Posts: 23,922
29 October 2013 23:01250580well looks like questions to be answered thenALL POSTS ARE MY OWN PERSONAL VIEWS - 29 October 2013 23:03250581You can cut and paste whatever you like Reg, it won't make any difference to the point I was making that there are no serious objections or reasoned arguments.
You can cut and paste the bible if you like, won't turn me into a christian, and when they bleat about their patio slabs shaking, it puts it into perspective.
Mr. Wiggins has told me more about the consequences of exploratory drilling that I would need to know to form an opinion, all your cut and paste has done is clog up the forum.
Do you actually have an opinion of your own about anything, or do you just select various items to cut and paste that suit your general world view ? - Keith Sansum1
- Location: london
- Registered: 25 Aug 2010
- Posts: 23,922
29 October 2013 23:04250583Barrie
even Neil whos a supporter of this drilling has concerfnsALL POSTS ARE MY OWN PERSONAL VIEWS - 29 October 2013 23:17250589Keith s., that was the point I was trying to make. Mr. Wiggins has not sensationalised the exploratory drilling, he has put forward a rational point in words that we can all understand that show his concern for the consequences, most of which are much more serious than the patio slabs. Reg's cut and paste tirade was a total waste, because I already think that before it goes ahead there should be lots of questions answered, and if the villages had used Mr. Wiggins' comments as their arguments, they would be taken much more seriously.
- 29 October 2013 23:22250590Gary - as posted before, when the contamination was at its height some years ago, us ordinary folk were not even aware of it (although it might explain the tendency to eccentricity of some of the locals). Didn't seem to have done any damage to livestock or agriculture either.
Reg - I read the paper that you have copied and pasted above some time ago along with about half a dozen others, some of which indicated contamination levels back down near background levels today. I've posted my views, arrived at after much research, in simple terms because posting complexities is toooo often a tool used by the unscrupulous to hoodwink the gullible. Keep it simple, keep it clear, keep to the subject, keep to what is true. - 29 October 2013 23:24250592Yeah ! What he said.........
