Mixed use urban extension comprising residential development up to seven hundred dwellings (20 ha), employment development within use classes B1,B2 and B8 (7.5ha), land for the expansion of Huxlow Science College (5.79ha), open space (8.9ha) and structural landscaping (10.3ha) and associated highway and drainage infrastructure including new roundabout junction on Finedon Road (A6).

REASONS WHY THIS OUTLINE PLANNING APPLICATION SHOULD BE REFUSED

History
In the spring of 2005 East Northamptonshire District Council, in its ‘Three Towns Proposed Options’ document, designated an area west of Huxlow School in Irthlingborough for the placement of 500 houses. ENDC was evidently unaware, at the time, of the existence of underground mine workings directly beneath the site.
As the former Chief Mines Surveyor of Richard Thomas & Baldwin’s Northamptonshire Properties, of which Irthlingborough Mine was the major part, and having unique knowledge of the nature and extent of the underground workings, I presented a report to ENDC, dated 19 September 2006, entitled  “Report on Stability of Land in Areas 3,4 and 6 etc.”.  This report dealt with the mine workings in broad terms, the existence of underground water and the probability that there would have been numerous roof falls in the mine since closure in 1965. Hallam Land Management saw this report, and indeed included it in their Outline Planning Application 10/00857/OUT dated 4 May 2010. Subsequent to my 2006 report I produced a plan for ENDC to indicate the actual extent and varying depths of the underground ‘lake’ in the area under consideration (Plan 1).

HLM, acting for the British Steel Pension Fund, engaged Rogers Leask Environmental Ltd. to investigate the methodology of remediation to enable the surface to be built upon. They, in turn, engaged M & J Drilling Services Ltd. to sink boreholes over the area, and to produce a report based on their series of borehole logs. (Plan 2)



 Following this, HLM, in a report in 2007 to ENDC, declared that “It was the initial intention to use mine waters to mix the grout.   However, since the mine was found to be dry it will be necessary [to] use mains supply“.  At the same time they suggested that the mine workings were   “somewhat less deep than published records“. Both statements were completely untrue. It suggested that the Abandonment Plan, required by law, was inaccurate. Whereas a written statement validating the accuracy of the plan which should have accompanied the plan was unaccountably destroyed. A copy of that statement has since been supplied to the Northamptonshire Record Office where the Abandonment Plan now resides.


Brookbanks, who submitted the Flood Risk Assessment on behalf of  HLM have, from the outset, maintained that the published record ( i.e. the Abandonment Plan) is incorrect, and as recently as March 2014 have submitted a document to ENDC which still maintains that the mine workings are shallower than shown on the official record.  It is this incorrect statement which is at the root of the problem regarding the assumption that the proposed flowpaths would be workable.
  I was astonished to read these two highly inaccurate statements, which showed a complete misinterpretation of M & J Drilling’s borehole information. I could not, in fact, reconcile much of the information contained in these borehole logs with my own knowledge of the true situation. For instance, one log indicated a thickness of 1.9 metres of ironstone where I know that the thickness is at least 3 metres, and could be considerably more. Another log located limestone as lying below the ironstone; which is, of course, geologically impossible; below the ironstone there lie 60 to 100 metres of clay. None of the boreholes, moreover, recorded surface levels, so that it was impossible to correlate accurately data from adjacent borehole logs, which I attempted to do without success.
  
Subsequent to their report, Hallam Land Management were asked, by the Environment Agency, to produce an effective solution to the problems of the standing water and storm water drainage; after six years no satisfactory solution has been offered. The proposals presented by them are fundamentally flawed for reasons which I will enumerate; until a satisfactory solution has been found to these problems it is most inadvisable that the Outline Planning Application be approved.  The District Council have stated the need  "to ensure that the proposed methodology for remediating the mines and drainage provisions is robust". The proposals are far from robust and this what I am trying to emphasise.  There are so many factors which remain unexplored, mostly arising from a complete lack of understanding of the underground conditions.
I would suggest that the method of dealing with these problems, from a planning point of view, is not so much different from that for contaminated land.
Norfolk County Council’s Planning Policy with regard to Outline Planning Applications for Contaminated Land states
"Extreme caution should be taken in the granting of outline planning permission unless the LPA is satisfied that it has sufficient information from the applicant about the condition of the land and its remediation and the full range of environmental impacts arising from the proposals to be able to grant permission in full at a later stage.  A grant of outline planning permission that cannot be sustained at the detailed approval stage because it becomes apparent that the necessary remedtiation is not viable could leave the LPA vulnerable to a claim for compensation."
 I was unable to find a similar statement by Northamptonshire County Council, but no doubt one exists.
Hallam Land Management’s Proposed Remediation Scheme
The basic proposal of the developers for dealing with the underground standing water and storm water drainage is that, rather than fill all the tunnels with pulverised fuel ash, certain tunnels would be designated as “flowpaths”, (Plan 3).  

 The tunnels (shown in blue) would be partially filled with a porous material to allow storm water to infiltrate the mine workings and to drain in a controlled manner to the main mine tunnel and thence to Lakeside (S2). (This outflow point was recommended by Atkins in their report dated 4 February 2011 (Plan 4).

 Atkins reported

“Discharge at S2 [Lakeside] appears to be similar to the volume that was reportedly pumped from the mine when it was in operation.   This would therefore appear to be the main discharge  point from the area of mine workings and should be the focus both of calibration effort if modelling is to be pursued and of the design of grouting works, i.e. grouting and drainage channel emplacement should ensure that this discharge pathway remains viable”.
Atkins did not, however, explain the mechanics of how this could be achieved. From S2, (that is, from Lakeside) the water at present overflows naturally to the river, and has done so since 1918.

 So far, however, not a single borehole has actually been driven into any of these designated “flow paths” (See Plan 2 above). Nothing is therefore known of the extent of roof falls in these tunnels. In addition, no account has been taken of the existing barriers of brick or stone, built from floor to roof across some of the proposed “flowpath” tunnels. These were placed to control the flow of air during the working of the mine (See Plan 3 above). They will of course still be in place and will present an impermeable barrier to water flows.  The Developers maintain that, when water encounters a barrier, such as these, or falls of roof, the water will simply flow around them in the ironstone.  That may be so, but nothing will induce the water to flow uphill to the point where it should overflow into the main mine tunnel.
The most important problem arising from the proposed scheme is that the final “flowpath”, intended to drain the water to the Main Mine Tunnel (Plan 3 above), rises at a gradient of 1 in 126 (A-B on the plan 3) such that there is a difference in level of some 4 metres from one end to the other of the tunnel, against the intended flow. Water will not naturally flow uphill and will therefore be forced to find an alternative route to the river.
Hallam Land Management's cross-section, illustrated in their “Lay Person’s Guide”, (Section1)


 
completely ignores this fact, and shows the seam of ironstone, wrongly, as being level. This is presumably based on Brookbanks' inaccurate assertion that the mine workings are shallower than as shown on The Abandonment Plan. It is evident that the Environment Agency has also overlooked this error. The Agency stated, in a letter to ENDC on 3 March 2012.

“We find the guide to be an honest and accurate assessment of the grouting proposals.  The geology is explained in sufficient detail with the movement of water”.
Both the Environment Agency and the Developers have stated that there is a "gentle syncline" or "basin" in the ironstone.  This is not borne out by the evidence on the Abandonment Plan.  It was for this very purpose that an Abandonment Plan was required to be produced by law, and the accuracy of the plan is impeccable.  The plan is supported by a written statement which establishes that the accuracy of the levels shown is to +/- 0.03 of a foot (0.93 cms.).
I have produced a more accurate cross-section (Section 2) below.





This section is derived from actual floor levels of the mine as recorded on the Abandonment Plan (produced for H.M. Inspector of Mines in 1966 when the mine was closed), together with surface levels taken from contours shown on Ordnance Survey records. This cross-section I have superimposed on the “Lay Person’s Guide” (Section 3)

This section clearly shows the discrepancies between HLM's diagram and the true facts. There is, in fact. a drop in the ironstone seam from north to south, and the point at which the water would drain into the Main Mine Tunnel is on the left of the section, not on the right as illustrated in HLM's "Lay Person's Guide".
 
Yet another gross error in their Laypersons' Guide has recently come to light; this not only shows the developers' lack of knowledge of conditions underground but also leads them to the mistaken idea that their 'flowpaths' could work.  Their illustrations suggest that only part of the seam was extracted and that the greater portion, possibly 12 feet, of ironstone was left unworked in the roof.  This, if it were so, would indeed allow water to flow through the ironstone to the disharge point. It is, however, most definitely not the case. I observed, in the late 1950's, that, where roof falls had occurred, about one foot only of ironstone was left to form a roof.  Immediately above that is a thick layer of impermeable clay, not of ironstone, as wrongly indicated in the Laypersons' Guide. This fact is also confirmed by the Mines Manager's Report, dated January 1942, which states :-
"The top 12 inches, 11% of the bed, is usually high in silica, and not of the best quality; this 12 inches is therefore left up to support the overlying strata [clays] which are extremely weak."


The suggestion by the Environment Agency of placing monitoring boreholes at strategic positions, to test the effectiveness of the proposed drainage and grouting system, is astounding. By the time these proposals are found to be wanting, it would be too late to act. The PFA filling could not, by then, be extracted and the consequences would be catastrophic.
A further aspect of the proposals, I suggest, is that, were a scheme to be devised to deliver storm water effectively to the Main Mine Tunnel, the 25 cm. diameter outfall pipe at Lakeside (Photo 1)

must surely be completely inadequate to cater for the fast run-off which would result from the hard standings of a large developed area particularly in times of spate; it would lead to a back-up of water in the Main Mine Tunnel. (Cross-Section 1).
 
To use that tunnel as a flood relief reservoir must be avoided at all costs; to do so would cause the wooden sleepers, left there when the rail tracks were removed, to float down the tunnel and to form a “beaver dam“ where the tunnel passes under Wellingborough Road. For this reason, the water channel in the tunnel must never be allowed to overfill. It must be borne in mind that the outfall is also still taking additional water from the adjacent Thingdon Mine, which closed in 1946, after which pumping ceased in that mine. I have little written evidence for this fact, just the knowledge that this is so, and the weekly report for 7 December 1946, shortly after the closure of Thingdon Mine, recorded, that,
“Water feeders have increased considerably in the last two weeks and in B2 West robbing area [which was adjacent to Thingdon Mine] it has become necessary to pump the full 16 hours from 7 am till 11 pm.”

Filling of All Voids
A further important aspect regarding the required infilling of  ALL voids prior to building, is that the Abandonment Plan shows some areas of pre-1938 workings as being completely robbed (collapsed).  This information was transferred from old, pre-1938, mine plans, but it cannot be assumed that all workings were in fact collapsed.  Owing to safety requirements, in places where weak roofs occurred, ironstone may have been left unrobbed.  The surveyor at the time (pre 1938) marked them as being fully robbed on the basis that the areas were no longer available for ironore extraction.  Where access was possible, in the late 1950's, a few areas, shown as robbed on the earlier plans, were re-entered and the true facts were recorded. It was found that the tunnels had all collapsed leaving a void above roof height and that consequently the areas were no longer available for mining. After 1938, where possible, robbed areas were indicated more accurately to show the ironstone that was not completely extracted.
 Recorded Evidence
1. The Abandonment Plan, required by law to be presented to the Mines Inspector after the mine closure in 1965, was marked with the positions of pumps in use below ground at the time of closure, together with the amount of water being pumped annually. This should, without doubt, have alerted the developers to the presence of water. In my report to ENDC in 2006 I highlighted the fact that much of the underground area would be waterlogged (Plan 1 above).
2. The OS levels of the tunnel floors shown on the Abandonment Plan indicated that the tunnels dip to the south.
　
3. On the 8 January 1944 the manager stated briefly in his weekly report that

”The Old Irthlingborough Pump has been stopped to form a reservoir of water underground in case of water shortage in the spring“.
This, is part of the area under consideration.
4. The fact that there may well be numerous roof falls is indicated in the manager’s weekly report, dated 24 July 1948, where he stated
“It is proposed to reopen the Main East B4 Pillar district [the area under consideration].   The track is laid throughout to the working places.  Several falls have occurred [roof falls] along the roadways and if the district is left for any length of time longer, the cost of re-opening is likely to be considerable”.
There will, without doubt, have been numerous roof falls since the closure of the mine nearly half a century ago, making it impossible to be assured of a continuous flow of water through any of the chosen 'flow path' tunnels to the main discharge point.




The Possible Reason for HLM’s Report that the Mine was Found to be Dry.
Cross section 2 illustrates the successive stages in the development of a typical roof collapse.

  Towards the left-hand side of the diagram is shown the initial collapse of a tunnel, where the strong Estuarine Limestone, approximately 2 metres above the roof of the mine, prevents the tunnels from collapsing further, leaving a void at about the original roof height. Many of the tunnels will be in this state. It is this fact that leads me to suspect that some of boreholes sunk by M&J Drilling penetrated this void, and that they mistakenly believed these to be the actual mine tunnels. If this were so, it would lead to the erroneous conclusion that the mine workings were somewhat less deep than as shown on the Abandonment Plan. It would also appear that the mine was dry because these voids would be above the level of the standing water which would be at about the original roof height of these waterlogged workings. This diagram was included in my report to ENDC which the developers accepted but chose to ignore.
　




Conclusion


If storm water cannot drain to the Main Mine Tunnel using the proposed “flowpath” system, then it can do no other than to pass through Irthlingborough, in an uncontrolled way, to reach the River Nene.


Few people are aware that the levels of the mine workings are higher than the parts of Irthlingborough which lie in a direct line to the river.
In view of the unpredictable outcome, and bearing in mind the warning from Norfolk County Council, quoted above, then to defer remediation proposals for inclusion in "reserved matters" could leave the LPA open to substantial claims if a satisfactory remediation scheme could not then be achieved.
There is also the added danger, with the limits of present technology, of being unable to locate every void which may occur in the areas shown as robbed on the abandonment plan.
A remediation scheme which puts parts of Irthlingborough town at risk of flooding must not be allowed to proceed further. In addition, houses must never be constructed over potential voids.

A foot note
On Monday 24th November 2014, at a special meeting of the of ENC Development Control Committee, the Outline Application  was discussed and passed 8 votes to 6 with one abstention.  Myself, a member of Irthlingborough Council, a member of IRE and The County Councillor were each given five minutes to speak against the proposals. A member of the Govenors of Huxlow School & Hallam Land spoke for the proposals.  Basically the decision was swayed by the threat of the huge costs which ENC would encounter if an inevitable appeal were to be upheld. A few months  after the Outline Application was approved a sink hole appeared on the surface over one of the critical Flow Paths. In fact, in this instance, it was the only flow path that could have been  used for this part of the area under consideration making the developer's proposals Null & Void. Another solution would have to be sought before development could proceed safely.