w clifford watts ltd park farm quarry plans for yorkshire … · 2016. 5. 25. · css pipeline...

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W Clifford Watts Ltd

Park Farm Quarry

PLANS FOR YORKSHIRE HUMBERSIDE CCS CROSS-COUNTRY PIPELINE

Report on Alternative Route for Pipeline Across Quarry

DCA 2 Mayors Walk Close Pontefract WF8 2SP

December 2014

CSS Pipeline Across Park Farm Quarry

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Contents 1. INTRODUCTION .............................................................................................................. 3

1.1 General ....................................................................................................................... 3 1.2 Personal Details .......................................................................................................... 3 1.3 Instructions ................................................................................................................. 4 1.4 Disclosure of Interests ................................................................................................. 4

2. SITE CONDITIONS........................................................................................................... 4 2.1 General ....................................................................................................................... 4 2.2 Geology ...................................................................................................................... 5

3. HISTORY OF EMBANKMENT ........................................................................................ 5 4. EMBANKMENT ................................................................................................................ 6

4.1 General ....................................................................................................................... 6 4.2 Stability of Embankment ............................................................................................. 7 4.3 Monitoring .................................................................................................................. 7 4.4 Site Investigation ........................................................................................................ 7 4.5 Potential Remedial Works ........................................................................................... 8 4.6 Alternative Route ........................................................................................................ 8

5. CONCLUSIONS ................................................................................................................ 8 6. DECLARATION ................................................................................................................ 9 7. REFERENCE ..................................................................................................................... 9


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W Clifford Watts Ltd Park Farm Quarry

Report on Alternative Route for Pipeline Across Quarry

1. INTRODUCTION

1.1 General W Clifford Watts Ltd currently extracts sand and gravel from Park Farm Quarry to the south of Kelk Lane to the west of Gransmoor village in East Yorkshire. They also operate a waste recycling plant in an old sand and gravel quarry known as Gransmoor immediately to the north of Kelk Lane. These two current quarry operations form a narrow band about 200m wide and 2.2km long running approximately northwest to southeast. They are separated by 670m of unworked land. This land between the two quarries currently contains an S-bend in Kelk Lane which occupies about 120m of the land and Barfhill Wood which occupies a further 300m. There is also a small old sand and gravel pit in this area. W Clifford Watts Ltd is to work reserves at Turtle Hill north of Gransmoor Quarry. They then intended to work the reserves between Park and Gransmoor Quarries. This would involve straightening Kelk Lane and re-locating Barfhill Wood. From Figure 1, National Grid now propose constructing a pipeline running parallel to and south of Kelk Lane towards the south of the barrier between Park Farm and Gransmoor Quarries. This will sterilise significant quantities of sand and gravel and therefore reduce the reserves against which to offset the capital cost of diverting Kelk Lane and moving the wood making further extensions uneconomic.

There is insufficient time to remove the sand and gravel from the route prior to the construction of the pipeline. W Clifford Watts Ltd has therefore proposed that the pipeline be re-routed across the quarry workings to the south on an existing embankment carrying Nutholmes Dike. The total length of the route across the quarry is 190m but only 130m is across land which has been quarried to a significant depth.

This report covers the stability of the Nutholmes Dike embankment.

1.2 Personal Details I am Dr David Thomas Carter, a civil engineer currently employed as the Principal of D Carter Associates, a specialist civil engineering, geotechnical and mining consultant set up in 1991. I have over forty years of varied post-graduate civil engineering, geotechnical and hydrology experience. Since 1991, I have had extensive experience in treatment of problems caused by mining including the settlement of backfill on opencast coal sites and of mining refuse. I graduated from the University of Leeds in 1965 with a BSc in Civil Engineering and was awarded a PhD in Soil Mechanics by the same university in 1969 for research into the soil moisture suction characteristics of clay soils.


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I became a Chartered Engineer and a Member of the Institution of Civil Engineers in 1972 and a Fellow of the Geological Society in 1973. I was a Fellow of the Institution of Mining Engineers until its merger with the Institution of Mining and Metallurgy and am now a Fellow of the merged institution. In 1968, I joined L M Shand first as a Soils Engineer on an earth dam but then as joint Company Soils Engineer, Bridge Engineer and Materials Engineer on motorways. I subsequently had experience for consultants, site investigation specialists and nationalised industries on site investigations, civil engineering and mining. In 1978, I was appointed Deputy Area Civil Engineer for the then National Coal Board and Group Civil Engineer for British Coal in 1989.

I have carried out project work in UK, Peru, Canada, Turkey, India, Spain, Russia, Kazakhstan, Ukraine, Korea, Kosovo, Macedonia, Mauritania, Albania, Armenia, Jordan, South Africa, Australia and Indonesia. This work has mainly been hydrological and geotechnical. In 2014 for example I have written reports on the slope stability and hydrology of two mine projects in Indonesia and on the hydrology of a proposed mine in Eritrea.

1.3 Instructions I received instructions from Mr Long, a consultant to W Clifford Watts Ltd on 12 November 2014 to prepare a report on the stability of the embankment. Mr Long also commissioned a site survey which was carried Latitude Surveys in November 2014. A site inspection was carried out on 18 November 2014 in overcast weather after heavy rainfall on the previous day.

1.4 Disclosure of Interests I have carried out periodically face and waste heap inspections for various W Clifford Watts Ltd quarries since 2002. This has given me a knowledge of the site over many years and helped in the preparation this report.

2. SITE CONDITIONS

2.1 General Park Farm Quarry lies 11km to the southwest of Bridlington at Grid Reference TA 120 580. Access is along a private road running south from Kelk Lane to the west of the village of Gransmoor. The site is bounded by the private access road from Kelk Lane in the north and east and by farmland in the south and west. Park House is present to the west at the north of the quarry. Prior to quarrying, Nutholmes Dike ran north-eastwards north of Park House to join Gransmoor Drain at the east of the site (See Figure 4) This water course was temporarily disrupted by a flooding of the quarry workings in 2007. In 2011, the drain was reinstated to the south of its original course at its original level on an embankment (See Plate 1). The drain continues to run along this embankment (See Plates 2 and 3). Quarrying is currently taking place to the north of the reinstated drain about 16 m below the level of the drain embankment.


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2.2 Geology Figure 2 shows the outlines Park Farm and Gransmoor Quarries superimposed on Sheet 64 of the 1 inch to one mile Geological Survey of Great Britain dated 1954. The two quarries closely follow the line of alluvium of the geological map but the workings are wider than the outcrop on the map. The map shows the same outcrop of alluvium continuing through Barfhill and under Kelk Lane to link Gransmoor and Park Quarries together. There is also an old sand and gravel pit in the area between Gransmoor and Park Farm Quarries. It therefore seems reasonable to assume that the deposit continues between Park Farm and Gransmoor Quarries. This deposit has been worked since the 1940’s and continues to be worked commercially. The deposit is therefore self-evidently of commercial quality. The pipeline is also shown running over a deposit of glaciofluvial deposits to the west of Park Farm Quarry.

3. HISTORY OF EMBANKMENT From the 2002 Survey of the site shown superimposed in red on the 2014 Survey in Figure 4, quarrying at that time had only taken place south of the original course of Nutholmes Dike. No quarrying had taken place within 25m of the current route of the dike. The floor of the quarry at the north was at a level of about -11 mOD. The 2004 inspection report by the author states that quarrying was continuing at the north of the quarry south of the original line of the dike. The 2009 survey suggests some quarrying had taken place on the line of the diverted dike over a width of about 70m to a level of about -0.2 mOD at the east and 0.2 mOD at the west. The main quarry floor was at a level of about -11mOD and this seemed to encroach within about 10m of the line of the current line of the dike over a width of about 30m. The August 2007 inspection could not be carried out because the site was flooded. It is understood that heavy rains and the possible mismanagement of a sluice gate elsewhere had caused the site to flood and had led to a failure of both banks of Nutholmes Dike over a length of about 28m. The upper levels of sand and gravel were subsequently removed but the lower band of cobbles was left in place to act as a drain connecting the two parts of the quarry. Reinstatement of the embankment to carry the dike was started in 2008. The 16 September 2009 survey drawing shows the line of the embankment had been quarried at a level of about 0.2mOD over a length of 70m and to a level of -11mOD over a length of 25 m at the top of batter. Some further excavation could possibly have taken place after the survey, locally increasing the width of the deeper excavation. Only 2-3m of excavation had taken place at the west.


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The deep part of the quarry on the line of the dike seemed to have been filled to a level of minus 4mOD working from east to west. At the time of the June 2010 inspection, an embankment had been built east to west across the quarry. The top level of this embankment was about 4m below the level of the adjacent ground. At the west, a 600mm diameter culvert located 2.5m below the level of the perimeter road carried the dike under that road to discharge into the base of the quarry. The water was then pumped out with the quarry dewatering pumps. The water level was maintained just below the level needed for quarrying in the dry. Work continued on building up the level of the embankment. It is understood that the embankment was completed to its current level and Nutholmes Dike re-instated in July 2011. At the time of the February 2013 inspection, Nutholmes Dike ran across the site on its current course. The new course was on the original course at the west but about 35m south of the original course at the east. The embankment width at the top was similar to its present width. At the time of the inspection for this report, fill had been placed against the south of the embankment. The fill was being delivered in dump trucks and spread in layers (See Plate 5). From discussions with Mr Long, the embankment was founded on a layer of in-situ boulders. From the 2009 survey, the level was brought to above water level by placing fill from east to west using quarry waste. The lower part of the embankment was then built in relatively thin layers using an orange clay excavated on site. Finally, the upper part was constructed of boulder clay placed in thin layers. From discussions with Mr Long, it is understood both the orange clay and boulder clay were both compacted using a Bomag BW213 sheepsfoot roller (See Plate 6).The author has inspected the W Clifford Watts Ltd plant records. These show that the Bomag roller worked 21 weeks at Park Farm Quarry between 18 August 2009 and 10 December 2010. These dates correspond to the construction of the embankment and no other work requiring a roller is understood to have taken place at Park Farm quarry during this period. The Bomag specification shows that the roller will compact between 110 and 220 m3/hour of clay. The time that the roller spent working at Park Farm Quarry is therefore more than sufficient to have compacted the clay in the embankment. The original embankment was understood to have been about 16m wide. The current width is typically about 24m wide. Fill is now being placed against the south side of the embankment to prevent any movement of this flank (See Plates 6 and 7). At the time of the inspection, the new fill was about 50m wide and about 3m below the top level of the embankment. Fill is also to be placed against the north flank.

4. EMBANKMENT

4.1 General The main eastern part of the embankment is 130m long and generally about up to about 5m high. The central part is up to 16m high in the area where the quarry has been worked to its full depth. Construction of the dike started in 2008 and the level had sensibly been raised to above the water


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level by the time of the September 2009 survey. The level was then built up in layers over 2 years. The dike on the completed embankment has been in operation for 3½ years. The edges of Nutholmes Dike ran 5.4m from the northern crest of the embankment and about 16m from the southern crest. Fill was being placed at the south about 3m below the top level. At 4m wide berm was present on the north flank of the berm. Minor movement was occurring on the north flank but this was not affecting the upper bench (See Plate 4). The northern flank is to be buttressed with quarry waste.

4.2 Stability of Embankment The clay in the main part of the embankment in the vicinity of the dike is understood to have been compacted using a Bomag BW213 sheepsfoot roller. From the Bomag specification, using this roller, a clay needs to be placed in 200-250mm thick compacted layers and mixed soil in 400 to 500mm thick layers. Investigations into the settlement of loose thickly tipped opencast backfill1 have shown that most settlement occurs within two years and that settlements after 5 years are generally very small. All measurable settlement is generally complete after 10 years. For fill settling under its own weight, two years should be left between completion of backfill and start of building. It is considered that the fill on this site will act in a similar manner. All of the clay on this site was compacted in layers with a sheepsfoot roller. With clay fills, consolidation can also occur. Construction of the embankment started 6 years ago and was completed 3½ years ago. Nutholmes Dike had been running for 3½ years without leaking or any settlement visible to the eye in the base of the dike. Using the opencast coal site analogy, it is considered that most significant settlement due to the expulsion of air should therefore be complete.

4.3 Monitoring As a check on the settlement potential of the site, level monitoring stations could be established on the embankment and the levels checked prior to the construction of the pipeline. Monitoring could continue after the completion of the pipe to ensure settlement is acceptable. If insufficient time is available to check the settlement potential of the embankment by site levelling, as an additional precaution, a site investigation could be carried out.

4.4 Site Investigation If insufficient time is available to complete the level monitoring, the density and hence settlement potential could be tested by a site investigation consisting of shell and auger boreholes with SPT’s carried out at frequent intervals. If the investigation shows that the embankment is stable, no further action is required and the pipeline may be safely constructed across the embankment.


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Samples of spoil will also need to be tested to design any remedial works. If the site investigation shows that the density of the embankment is insufficient and some further settlement could potentially occur, some remedial works could be required.

4.5 Potential Remedial Works If the site investigation shows that some remedial works are necessary, these works could consist of vibroflotation. This consists of constructing “piles” at relatively close centres along the route by inserting a vibrating probe into the ground. Probes at 1.8 to 3m centres with depths of the 2.5-4m are typically used to form a raft. The probe holes could need to be backfilled with clean stone or gravel and the surface rolled after treated. Deep compaction by dynamic consolidation could also be considered.

4.6 Alternative Route If the site investigation shows that some further settlement could occur and National Grid will not accept in situ treatment of the fill, an alternative route across the quarry could be considered. The fill could then be placed under controlled conditions to ensure to significant settlement occurs.

5. CONCLUSIONS 1. W Clifford Watts Ltd currently operates sand and gravel quarries to the north and south

of Kelk Lane at Gransmoor in East Yorkshire. These quarries are both on the same outcrop of alluvium shown on the relevant geological map. This same outcrop is shown continuing through the 670m of unworked land between the two quarries.

2. National Grid intends to build a pipeline across this unworked land, sterilising some reserves of commercial sand and gravel.

3. Even with pre-extraction and stockpiling, there may be insufficient to time to obtain the necessary approvals to remove the sand and gravel prior to the construction of the pipeline. W Clifford Watts Ltd has therefore proposed an alternative route for pipeline across an existing embankment running across the worked out part of the quarry. This embankment already carries Nutholmes Dike across the quarry void.

4. From checks on the plant records, a Bomag BW213 sheepsfoot roller was working on site for sufficient time to compact the clay in the embankment. It is understood the existing embankment was constructed by placing fill in layers with orange clay placed above the water level in the quarry and boulder clay placed in the upper section. All of the clay was compacted using the Bomag BW213 sheepsfoot roller.

5. Even if the compaction had been insufficient, previous work at Newcastle University has shown that most settlement of opencast backfill occurs within two years and that settlements after 5 years are generally very small. All measurable settlement is generally complete after 10 years. They suggest for fill settling under its own weight, two years should be left between completion of backfill and start of building. It is considered that this study is relevant to the settlement of any part of the embankment insufficiently compacted on this site. Construction of the embankment started in 2008 and was complete by 2011. It is now 6 years since the start of construction of the embankment. Most settlement by the removal of air should therefore already have occurred.


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6. The pipeline will not impart any additional loads and should not therefore increase consolidation.

7. Nutholmes Dike had been running for 3½ years without leaking or any settlement visible to the eye in the base of the dike. This tends to confirm significant settlement is complete.

8. The settlement of the embankment could be checked by installing survey points. 9. If insufficient time is available for the monitoring to be conclusive, as a check, the

density of the fill in the embankment could be confirmed by carrying out a site investigation using shell and auger rigs with SPT measurement. If the site investigation suggests that further settlement could occur, the embankment could be treated by vibroflotation or dynamic consolidation.

10. If the site investigation and monitoring shows that the embankment could still be subject to some settlement, a new embankment could be built across the quarry working founded on dry natural ground. The compaction of the fill could then be checked as the fill is placed.

6. DECLARATION

I, David Thomas Carter confirm that insofar as the facts stated in my report are within my own knowledge I have made clear which they are and I believe them to be true and that the opinions I have expressed represent my true and complete professional opinion.

7. REFERENCE 1 W M Kilkenny: A Study into the Settlement of Restored Opencast Coal Sites and Their

Suitability for Building Development. University of Newcastle upon Tyne Department of Civil Engineering Bulletin No 38 May 1968

D T Carter BSc, PhD, MICE, FIMMM, C Eng, FGS. 9 December 2014

Alternative Route for Pipeline

Figure 1 General Layout

Park Farm Quarry

Proposed PipelineGransmoor

Quarry

Barfhill Wood

Figure 2: Outline of Quarries Overlain on Geological Map

Park Quarry

Gransmoor Quarry

Alternative Route for Pipeline

AC

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511200E

511100E

511000E

Top

S oil

Top

S oil

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W Clifford Watts LtdPark Farm QuarryNutholmes Dike Embankment

Figure 4: History of Workings Near Dike

Original Line of Dike

Top of Batter in 2002 SurveyTop and Bottom of Batter in 2009 Survey

Current Line of Dike


Plate 1: Reinstated Dike February 2013

Plate 2: Reinstated Dike November 2014


Plate 3: Reinstated Dike November 2014

Plate 4: North Flank of Embankment


Plate 5: Spreading Fill in Layers South of Main Embankment in November 2014

Plate 6: South Flank of Embankment


Plate 7: South of Main Embankment

Plate 8: Bomag BW 213 Roller

w clifford watts ltd park farm quarry plans for yorkshire … · 2016. 5. 25. · css pipeline...

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