WHITWELL QUARRY, DERBYSHIRE

Transcription

1 WHITWELL QUARRY, DERBYSHIRE PROPOSED NORTH, NORTH EAST, EAST AND SOUTH EAST EXTENSIONS TO WHITWELL QUARRY SOILS AND AGRICULTURAL LAND CLASSIFICATION REPORT March 2016 CONTENTS 1. Introduction 2. North East extension area soil survey 3. Impact of the movement of soils stockpiled in the North, East and South East extension areas 4. Soil Resources and their use in restoration 5. Soil Handling Criteria and Methodology 6. Management of Soil Stockpiles 7. Conclusions APPENDICES Appendix 1 Description of the Agricultural Land Classification grades and subgrades Appendix 2 Agricultural Land Classification map and auger boring and pit locations for the North East extension Appendix 3 Pit description for the North East extension Appendix 4 Soil handling criteria and tests Appendix 5 Sheets 1 to 4 of MAFF Good Practice Guide for Handling Soils Appendix 6 Description of the Peninsula method for soil placement Appendix 7 Sources of reference Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 1

2 1. INTRODUCTION 1.1 This report is prepared to support the planning application for the extraction of mineral from four extension areas at Whitwell Quarry as well as the revision of the restoration scheme for the site. The impacts of the proposed development on soil resources is assessed. The site is an active quarry which has been operated since the 1950s. In the early days of quarry operations soils resources were not husbanded in common with typical quarries of this era. Under the current planning consents the soils stripped from newly excavated areas of the site are handled in accordance with current good practice guidelines and are stored at various locations at the site. It is intended that the soil stripped from the site will be re used in the restoration of the site. 1.2 The locations of the current soil stores together with the proposed extension areas are shown on Figure ES4 of the Environmental Statement which accompanies the application. 1.3 The currently consented quarry extraction areas have already been walked with their soils removed and the impacts of the quarrying activities on soil resources have been assessed as part of previous studies and applications. 1.4 Each of the four proposed extension areas has a different current land use. The North extension is covered with soil storage mounds and most of the area was stripped of soils prior to the construction of the soil mounds. The North East extension comprises rough grassland which may be an artificial landform created as part of the construction of the adjacent disused railway sidings. The East extension is partly on the location of a former railway siding and the South East extension is covered with closely planted woodland. Limited areas of soil storage mounds are located on the East and South East extension areas. 1.5 An Agricultural Land Classification Survey has been carried out of the soils in the North East extension area and an assessment has been made of the impact on the quality of the soils in the existing stores where they are to be moved as part of the development proposals. The use of the soils in the restoration of the site is also assessed. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 2

3 2. NORTH EAST EXTENSION AREA SOIL SURVEY 2.1 A detailed Agricultural Land Classification (ALC) survey was carried out of the 2.5ha area of land comprising the proposed North East extension at Whitwell Quarry. The survey was completed on 16 th July The survey was carried out by Adrian Rochford (Adrian Rochford Land Management) for Tarmac as part of the assessment of soils and agricultural impacts in connection with the proposed North, North East, East and South East extensions to the existing quarry. 2.2 The land in the North East extension has been graded in accordance with the published ALC guidelines and criteria (MAFF, 1988). A description of the ALC grades and subgrades is given in Appendix The surveyed area consisted of a single field, which at the time of survey was mostly rough grassland. About one third of the field, in the south eastern part, appeared to have been grazed by sheep and topped. The findings of the survey of the North East extension are shown on the ALC map at Appendix The approximate areas and proportions of the ALC grades and subgrades on the surveyed land are summarised in Table 1. Table 1: Area of grades and other land Grade/Other land Area (hectares) % surveyed area 3a 3b Total surveyed area The fieldwork was conducted at an average density of approximately 3 auger borings per hectare. A single representative soil pit was dug at the location of auger boring 4 to confirm the typical soil physical characteristics within the survey area. In total, 7 auger borings and a single pit were described. The locations of the auger borings and pits are shown on the ALC map at Appendix 2 and the description of the pit is provided at Appendix Most of the North East extension has been assessed as subgrade 3b (Moderate quality agricultural land) and is typically equally limited by gradient and droughtiness. The gradient limitation applies where the land slopes more steeply than 7 o (1:8). The droughtiness constraint corresponds with soil profiles where there is only a shallow soil resource over limestone. A small area of sub grade 3a (Good quality agricultural land) has been identified and mapped at the base of the slope adjacent to the middle part of the north east boundary. Here, the gentle gradients of around 3 o do not impose any limitation, and the slightly deeper soil resource above the limestone has a higher available water capacity and the land is therefore only moderately droughty. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 3

4 2.7 A number of factors influence the ALC grade comprising climate, site specific geography, geology and soils each of which are addressed below. Climate 2.8 Climate affects the grading of agricultural land through the assessment of an overall climatic limitation and also through interactions with soil characteristics. The climatic variables used for grading the North East extension are set out in Table 2 below. These were calculated from the published 5km grid dataset values using standard interpolation procedures (Met. Office, 1989). Table 2: Climatic and altitude data Units Values Grid reference N/A SK Altitude m, AOD 90 Accumulated Temperature day C (Jan June) 1336 Average Annual Rainfall mm 684 Field Capacity Days days 99 Moisture Deficit, Wheat mm 87 Moisture Deficit, Potatoes mm 147 Overall climatic grade N/A The climatic criteria are considered first when classifying land as climate can be overriding. This is because a severe climatic limitation will restrict land to low grades irrespective of favourable site or soil conditions. The main parameters used in the assessment of an overall climatic limitation are average annual rainfall (AAR), as a measure of overall wetness, and accumulated temperature (AT0, January to June), as a measure of the relative warmth of a locality This site is located in an area of relatively warm and dry climate, where the combination of low rainfall and mild temperatures impose no climatic limitation. The site is therefore of climatic grade 1. Site 2.11 The North East extension consists of a single field which currently supports rough grassland. The field slopes from a high point of about 95m AOD in the north west to the lowest parts of the field in the south east where the altitude is about 85m AOD. Gradients of 7 to 8 o were measured in the north west, but slopes slacken to 3 o or less towards the northeastern boundary and in the south eastern half of the site. The North East extension is bounded to the south west by plantation woodland beyond which is the quarry, to the north by the railway in a cutting before it inters the tunnel, to the north east by a tree lined disused railway siding and to the south east by the quarry plant site. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 4

5 Geology and soils 2.12 At a scale of 1:50 000, the British Geological Survey s Geology of Britain Viewer maps the area as Cadeby Formation Dolostone. This is a type of Magnesian Limestone. At a reconnaissance scale of 1: , the Soil Survey of England and Wales (Sheet 3, Midland and Western England) maps the site as the Aberford Association. This Association is briefly described as: Shallow, locally brashy, well drained calcareous fine loamy soils over limestone. Some deeper calcareous soils in colluvium The soil survey found soils which correspond with the Aberford Series, which is the main component series within the Aberford Association. The Aberford Series comprises clay loam or silty clay loam topsoil and subsoil extending to 30 to 80cm before limestone is encountered. In more detail, the soils identified in the North East extension during the survey on 16 th July 2014, are described below. Although some variability in depth to limestone was noted, the soils have not been delineated into two or more separate Soil Types because the variation is small and appears to occur over short distances. Delineation is not therefore considered to be appropriate as the boundaries of any mapping units could be spurious. Soil Type A corresponding with the North East extension survey area 2.14 Topsoils range in thickness from 22cm to 32cm (26cm average); they are noncalcareous, very slightly stony and have medium silty clay loam texture. Topsoil depth was slightly deeper in the north west half of the site (26 32cm) than in the south east half of the site (22 to 25cm). The typically non calcareous, medium silty clay loam upper subsoil extends to variable depth, ranging from 34cm to 60cm (below the land surface). The upper subsoil is typically slightly stony, containing small and medium limestone fragments. In three of the seven auger borings, limestone was encountered directly beneath the upper subsoil. At the other four auger borings, a thin, very stony, slightly calcareous, typically sandy loam lower subsoil occurred between the upper subsoil and the limestone. Across the survey area, depth to limestone ranged from 35 to 60cm, but showed no clear pattern The location of the auger borings and pits and the details of the classification of the site are shown on the ALC map at Appendix 2. The areas of the North East extension formed of each grade are given in Table 1 above. Subgrade 3a The subgrade 3a mapping unit occupies a small strip adjacent to the north east boundary of the extension area. This corresponds with the deeper soil profiles encountered on gently sloping land where neither drought nor gradient restricts the land to subgrade 3b. In this area, the limited soil depth due to the occurrence of limestone below 45 60cm still restricts the ability of the soil to retain water for crop growth, and therefore imposes a moderate droughtiness constraint. This restricts the land to subgrade 3a. Subgrade 3b Most of the land mapped as subgrade 3b corresponds with shallow soils over limestone where the rootable depth of soil is less than about 45cm. The amount of water accessible by crop roots in these shallow soils is therefore very limited and this imposes a Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 5

6 significant drougtiness constraint, which precludes the land from a higher grade. In the northwestern half of the North East extension, gradients of greater than 7 o impose an equally limiting constraint to the land quality. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 6

7 3. IMPACT OF THE MOVEMENT OF SOILS STOCKPILED IN THE PROPOSED NORTH, EAST AND SOUTH EAST EXTENSION AREAS Background 3.1 There are three soil storage mounds situated within the proposed North extension area, and in order to gain access to the quarry stone beneath, some of these storage mounds need to be moved to a suitable place within the quarry, from where they will ultimately be moved and placed in final restoration of agricultural areas. In addition, storage mounds located in the East and South East extension areas are likely to contain some soil resources, and where these occur they will be used beneficially in the final restoration of the site. 3.2 The exact physical characteristics of the content of the soil stores is not known, but with respect to those in the North extension area, from the nature of their vegetative cover and a cursory examination of the soil texture at two auger boring locations per bund, it is believed that the central bund is likely to be mostly topsoil, and the western and eastern bunds subsoil. Proposed new location 3.3 It is proposed to translocate the soil stores from the North extension to an area in the north west corner of the main quarry void, immediately to the south of the railway tunnel. This storage area lies approximately 10m above the ground water level, and the soil stockpile will be graded to allow drainage from the storage bunds and their immediate surroundings. This proposed new location should therefore be suitable for the soil bunds. Considerations to ensure structural damage is avoided or minimised when handling soil resources Handle soils when they are dry and friable 3.4 To minimise the risk of causing structural damage to soil resources when they are moved or otherwise handled movement will be carried out when the soils are as dry as possible. To help in this respect, vegetation on storage mounds will be flailed periodically to encourage vigorous growth, which will help dry out the soil. Care will be taken to time such work to avoid disturbing ground nesting birds and/or potentially damaging habitat for invertebrates at critical times of the year. In any event, the aim will be to schedule the handling of soils to coincide with a prolonged dry period in mid to late summer, when actively growing vegetation is likely to have dried out the soil to significant depth. Correct choice of machinery and methodology 3.5 The choice of machinery and its method of use will also be a key to ensuring that the soil resources are not damaged during the handling operations. For this reason, the methods described in sheets 3 and 2 of the Good Practice Guide for Handling Soils (GPG) (Appendix 5) will be followed. These methods specify a method whereby there is no trafficking of the soils other than by the tracks of the 360 o excavator, which will exert minimal pressure to the soil surface. In Sheet 3, the excavator progressively digs the soils from the bunds, and loads it into dump trucks which only traverse on overburden Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 7

8 and haul routes. In Sheet 2, the dump trucks back tip the transferred soils, which are formed into the new storage bund by a 360 o excavator, which is either standing on the overburden layer or on the top of the bund. The bund sides and top are slightly consolidated using the excavator bucket and/or tracks; this assists the shedding of rainwater during the lifespan of the bunds. The top of the bunds will be shaped with a convex surface; this is to ensure that rainwater is shed from the surface rather than ponding/soaking into the bund core. 3.6 If soils are directly placed in their final restoration position, soil placement will follow the methodology described in Sheet 4 of the Good Practice Guide for Handling Soils. 3.7 Provided these methodologies are adopted, and there is no loss of soil resources, or contamination of soil resources, the proposed movement of the soil stores should not degrade or compromise the soil resources. Indeed it could give the opportunity to loosen them, and by forming bunds with a slightly convex top, seeding them with vigorously growing grass, and ensuring at least annual topping, could even improve their condition. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 8

9 4. SOIL RESOURCES AND THEIR USE IN RESTORATION 4.1 All topsoil resources from the North East extension area will be stripped and stored for use in agricultural restoration. During stripping, care will be taken to observe changes in topsoil depth and to minimise the amount of contamination of topsoil with subsoil. 4.2 As much as possible of the very slightly to slightly stony subsoil resource will be stripped and stored for use in agricultural restoration. The subsoil resource within the North East extension area is of variable depth, but also generally of shallow depth. As its boundary with a very stony lower subsoil or limestone rock is likely to undulate/have a wavy surface, during stripping changes will be observed carefully and only material with a relatively low stone content e.g. <15% stone will be included in the subsoil resource material. 4.3 The proposals for the restoration of the site are shown on Figure ES5 of the Environmental Statement and the indicative phased restoration proposals are shown on Figures ES9 to ES12 of the Environmental Statement. The soil depths that will be established in order to optimise the use of the soil resources stored at the site are set out in Table 3 below. Table 3. Soil depths for restored site areas. Restoration land use Arable Calcareous Grassland Agricultural Grassland Wet Grassland/Fen Woodland Soil profile 250mm topsoil over 400mm sub soil, preferably over 500mm of rootable overburden / quarry waste material 150mm subsoil (mixture of soil/overburden from old screening bunds) over 500mm overburden/quarry waste material 200mm topsoil over 500mm overburden/quarry waste material 200mm topsoil over 500mm overburden/quarry waste material 300mm topsoil/subsoil over 500mm overburden/quarry waste material Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 9

10 5. SOIL HANDLING CRITERIA AND METHODOLOGY 5.1 Soils can suffer from structural damage due to trafficking with heavy machinery and through handling during stripping and stockpiling operations. The damage that can occur includes smearing and compaction, both of which reduce the soils ability to provide a good growing medium for crops. This is because compaction and smearing reduces the permeability of the soils, causing poor or slow drainage, and makes soils more dense which impedes root penetration, worm activity and other processes. Such damage is likely to be difficult and expensive to remedy during the aftercare period and so it is best avoided. 5.2 Generally, damage to soil structure and smearing is more likely to occur, and is more likely to be severe, if soils are handled when they are too wet. To reduce damage, soils should therefore only be handled when they are in a dry and friable condition, which should be assessed on site using the method presented at Appendix 4. Soil handling methodology 5.3 The soils identified in the North East extension by the Agricultural Land Classification Survey, i.e. medium silty clay loams, will be vulnerable to structural damage if they are handled inappropriately. 5.4 To minimise damage to soil structure and achieve a high standard of restoration, all soils will only be handled when they are in a dry and friable condition and using loosetipping methods with backactors and dumptrucks. The methodology is set out in MAFF s Good Practice Guide for Handling Soils (GPG) and will be carefully followed on site with appropriate supervision. Sheets 1 4 from the GPG cover soil stripping, forming and taking down soil storage bunds, and soil replacement, are provided as Appendix As an alternative to Sheet 4 of the GPG, the Modified Loose Tipping Method can be used for soil replacement. This includes the so called Peninsula and Lateral Heap methods, which are used successfully at other Tarmac sites (e.g. Swarkestone), and are well known by Tarmac s Restoration Managers. A description of the Modified Loose Tipping Method is provided as Appendix 6. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 10

11 6. MANAGEMENT OF SOIL STOCKPILES 6.1 Topsoil and subsoil are and will continue to be stored separately, in bunds constructed and managed as set out below. 6.2 Topsoil bunds will not exceed 3 metres in height and subsoil bunds will not exceed 5 metres in height. Their profile will allow them to be seeded with grass, and allow cutting and other maintenance to be carried out. Soil storage bunds will be placed like upon like. Therefore, topsoil bunds may be placed upon in situ topsoil, but topsoil will be stripped from the footprint area of subsoil bunds. 6.3 Bunds will be constructed with the minimum amount of compaction to ensure stability and shaped with a slightly convex top, to avoid the collection of water on their surface. Bunds will not be traversed by heavy vehicles or machinery, except where this is essential for their construction or for subsequent maintenance of the bund. 6.4 Bunds that are in place for more than 6 months, or over winter, will be seeded with grass and managed to prevent weeds from seeding and spreading to adjacent areas. The grass seed mixture will where possible be based on long lived, vigorously growing perennial ryegrasses, and include a small amount of white clover. The seed rate will depend upon the seed mixture, soil and weather conditions, but is likely to be around 30kg/ha for topsoil bunds and 40 kg/ha for subsoil bunds. 6.5 To maintain the vigour of the grass cover and minimise the establishment and seeding of injurious weeds such as docks and thistles, bund vegetation will be topped periodically. The timing will depend on the extent of vegetation growth. Care will be taken to avoid disturbing ground nesting birds or destroying their nests. 7. CONCLUSIONS 7.1 Where present, topsoil and subsoil will be stripped prior to the commencement of quarrying in each extension and stored for use in the restoration. The soils from the North East extension will be stored for use in restoration of areas of the site to agriculture. The soils will be stored in areas of the quarry that have already been worked in accordance with best practice for soil management. 7.2 The mitigation measures proposed to minimise the impact on soil resources comprise the use of best practice in the stripping, movement and storage of the soils. The soil will be stripped, stored and placed in restoration areas in accordance with MAFF Guidelines for handling soil. Soils stripped from the site will be used in restoration resulting in no net loss in soil resources at the site. 7.3 As a result of the proposed development there will be no overall loss of grade 3a or 3b agricultural land as suitable agricultural soils will be stripped and stored in a manner which will maintain their condition and they will be used to generate agricultural land as part of the restoration of the site. Adrian Rochford April 2016 Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk Page 11

12 Appendix 1 DESCRIPTIONS OF THE GRADES AND SUBGRADES Grade 1: Excellent Quality Agricultural Land Land with no or very minor limitations to agricultural use. A very wide range of agricultural and horticultural crops can be grown and commonly includes top fruit, soft fruit, salad crops and winter harvested vegetables. Yields are high and less variable than on land of lower quality. Grade 2: Very Good Quality Agricultural Land Land with minor limitations which affect crop yield, cultivations or harvesting. A wide range of agricultural or horticultural crops can usually be grown but on some land of this grade there may be reduced flexibility due to difficulties with the production of the more demanding crops such as winter harvested vegetables and arable root crops. The level of yield is generally high but may be lower or more variable than Grade 1 land. Grade 3: Good to Moderate Quality Land Land with moderate limitations which affect the choice of crops, the timing and type of cultivation, harvesting or the level of yield. When more demanding crops are grown, yields are generally lower or more variable than on land in Grades 1 and 2. Subgrade 3a: Good Quality Agricultural Land Land capable of consistently producing moderate to high yields of a narrow range of arable crops, especially cereals, or moderate yields of a wide range of crops including cereals, grass, oilseed rape, potatoes, sugar beet and the less demanding horticultural crops. Subgrade 3b: Moderate Quality Agricultural Land Land capable of producing moderate yields of a narrow range of crops, principally cereals and grass, or lower yields of a wider range of crops or high yields of grass which can be grazed or harvested over most of the year. Grade 4: Poor Quality Agricultural Land Land with severe limitations which significantly restrict the range of crops and/or the level of yields. It is mainly suited to grass with occasional arable crops (e.g. cereals and forage crops) the yields of which are variable. In moist climates, yields of grass may be moderate to high but there may be difficulties in utilisation. The grade also includes very droughty arable land. Grade 5: Very Poor Quality Agricultural Land Land with severe limitations which restrict use to permanent pasture or rough grazing, except for occasional pioneer forage crops. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

13 Appendix 2 Agricultural Land Classification map and location of auger boring and pit locations for the North East extension Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

14 Appendix 3 Pit description for the North East extension at Auger Boring 4 Topsoil: 0 24cm Brown, non calcareous, medium silty clay loam with 2% small and medium limestone fragments. Abundant very fine and fine roots, good porosity, friable consistence, sharp wavy boundary to next horizon. Upper subsoil: 24 45cm Strong brown, very slightly calcareous, medium silty clay loam with inclusions of very pale brown, weathered sandy limestone; very stony, containing 50% large pieces of limestone rock. Many very fine and fine roots, few earthworm holes and other small pores, friable consistence. Moderately well developed, coarse sub angular blocky structure. Lower subsoil: 45 50cm+ Fissured, calcareous limestone rock, initially about 10% strong brown, sandy loam infill between rocks, but this is likely to decrease to negligible or no infill by about 60cm. Few very fine roots within infill. Comments: Significant droughtiness constraint restricts to sub grade 3b. Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

15 Appendix 4. Soil handling criteria and tests Closed season and definition of dry and friable A closed season for handling soil should be applied between the months of November and March inclusive, unless otherwise agreed in writing with the Mineral Planning Authority. At all other times soils should only be handled when they are in a dry and friable condition. Broadly speaking, a soil is dry and friable when it breaks and shatters when disturbed rather than smears and deforms. The following tests describe the methods which will be used on site to objectively differentiate between these two conditions. Soil tests Soil tests will be undertaken in the field, on representative samples taken from the full depth of the soils which are to be handled. The tests will include visual examination of the soil and physical assessment of soil consistency. Visual examination test: If the soil is wet, films of water are visible on the surface of soil aggregates (e.g. clods or peds) and/or when a clod or ped is squeezed in the hand it readily deforms into a cohesive ball, this indicates that the soil is not in a dry and friable condition and no handling will take place. If the sample is moist (i.e. there is a slight dampness when it is squeezed in the hand) but it does not significantly change colour (darken) on further wetting, and clods break up/crumble readily when squeezed in the hand, rather than forming into a ball, this indicates that soil handling can take place. If the sample is dry, it looks dry and changes colour (darkens) if water is added, and it is brittle this indicates that soil handling can take place. Consistency test First Test Attempt to mould a sample of soil into a ball by rolling it between the palms of your hands: If it is impossible because soil is too dry and hard HANDLING OK If it is impossible because the soil is too loose and dry HANDLING OK If it is impossible because the soil is too loose and wet DO NOT HANDLE SOIL If it is possible to roll the soil into a cohesive ball GO TO NEXT TEST Second Test Attempt to roll the ball of soil into a 3mm diameter thread using the palm of your hand on a ceramic tile, the back of a spade or a similar smooth surface: If it is NOT possible because the soil crumbles or collapses HANDLING IS OK If it is possible, the soil is in a plastic state and too wet to handle DO NOT HANDLE SOIL Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

16 NB: It is impossible to roll most coarse loamy and sandy soils (e.g. sandy loam or lighter texture) into a thread even when they are wet. For these soils, the result of the visual examination test alone should be adhered to. Weather and ground conditions Soil handling should stop during rain, sleet or snow. The following criteria should be applied: In light drizzle soil handling may continue for up to 4 hours unless the soils are already too moist In light rain soil handling should stop after 15 minutes In heavy rain and intense showers, soil handling must stop immediately After rain has ceased, soil tests should be applied to determine when handling may restart No soil handling should take place when there are pools of water on the land surface Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

17 APPENDIX 5 SHEETS 1 TO 4 OF MAFF GOOD PRACTICE GUIDE FOR HANDLING SOILS Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

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64 Appendix 6. Soil Handling - Modified Loose Tipping Procedure for Soil Replacement. (The Peninsula or Lateral Heap Methods) The following describes two methods of loose tipping originally devised by John Jones (Excavation) Ltd and Stoke Plant Hire to whom due acknowledgement is made. 1. In order to avoid compaction and other structural damage to soils during restoration operations a so-called "loose tipping" method is normally recommended. The basic principle of the method is to minimise or even totally avoid trafficking over replaced soils, particularly by wheeled vehicles. 2. Two loose tipping" methodologies are described in the DEFRA Good Practice Guide for Handling Soils, hereafter referred to simply as the Guide. This is available on the internet at webarchive.nationalarchives.gov.uk/ / environment/land-use/soilguid/index.htm (note there is no e at the end of soilguid ) 3. One method, often referred to as the "dump-truck and back-acter" method is described in Sheet 4 Soil Replacement with Excavators and Dump Trucks and is illustrated in Figures 4.1 to 4.4 below, taken from the Guide. 4. In this procedure the subsoil is delivered to the area being restored by dump-trucks which are only allowed to travel on the substrate. It is then levelled out with the blade of an excavator which is itself situated on the substrate. This means that the restoration has to be carried out in strips or beds, the widths of which are determined by the maximum reach of the excavator arm. 5. Topsoil is then tipped alongside the strip being restored, with the dump trucks again restricted to running only on the substrate. The topsoil is then lifted by the excavator and spread out to the required thickness over the strip of previous laid subsoil. 6. Criticisms of this method are that it is slow, requires very skilled personnel and can lead to losses of topsoil since not all the delivered topsoil can be cleanly picked up by the excavator. Also the substrate is compacted by the dump truck trafficking and this may be a marked disadvantage if the substrate is required, like the over-lying soils, to be permeable to assist overall site drainage.

65 7. However, loosening operations on the substrate can be carried out before the soil is placed but has again to be done in narrow strips or beds. Methods of achieving this are provided by the Guide, Sheets 18 Soil Decompaction by Excavator Bucket and 19 Soil Decompaction by Bulldozer Drawn Tines. 8. A second kind of "loose tipping" methodology uses bulldozers rather than excavators to spread the soils. It is described Sheet 15 Soil Replacement with Bulldozer & and Dump Trucks and is illustrated in Figures 15.1 to 15.3 below, taken from the Guide. 9. This procedure differs from the dump truck and back-acter method in that the subsoil is levelled out not by an excavator standing on the substrate but by a light, tracked bulldozer running over and pushing out the delivered subsoil to the required thickness. 10. The operation of the bulldozer compacts the surface over which it runs but often the next push re-loosens the material. Thus it is only the final surface which has some compaction and then only in the surface few centimetres. This has to be removed by the loosening methods mentioned above i.e. Sheets 18 Soil Decompaction by Excavator Bucket and 19 Soil Decompaction by Bulldozer Drawn Tines. 11. The topsoil is then delivered by dump trucks which attempt to tip it onto the edge of the subsoil. In practice, however, they usually have to reverse some way onto the subsoil layer, hence causing compaction and collapse of the edge of the subsoil layer. The sharp self-standing edge of the subsoil layer shown in the uppermost diagram of Figure 15.3 is never achieved in practice. 12. The delivered topsoil is then spread out to the required thickness by a light, tracked bulldozer. There is again the likelihood of some surface compaction but this can readily be corrected, often as part of the agricultural operations carried out for the first crop. 13. The description of this procedure in Sheet 15 implies that, like the dump-track and back-acter method, this is also carried out in relatively narrow strips. This is, in fact, not necessarily the case. The limiting factor is the distance to which a bulldozer can push out a heap of soil into a thinner covering and, in practice, this can be done over a much wider area than the narrow strips which are a necessity of the dump truck and back acter method (Sheet 4).

66 14. Of the two methods, the one using excavators to lift and spread the soil is relatively complex and may result in loss of topsoil, while the one using bulldozers, although simpler, can cause some compaction and can also involve topsoil losses. The compaction is, however, not so severe as would be caused by wheeled traffic and much of it is removed by the spreading action of the bulldozer. Only slight surface compaction has to be dealt with and this is easily achieved. 15. A modified version of the dump truck and excavator/bulldozer methods is outlined below which overcomes the problem of potential soil loss as well as being operationally easier to carry out. It differs from these methods essentially in the way in which the topsoil is delivered to and spread over the area being restored. 16. It is described for topsoil and subsoil replacement but could be further modified to deal with substrate replacement particularly where it is required that the substrate, as well as the soil layers, should be free of significant compaction. Figures RPS 1, RPS 2 and RPS 3 illustrate the procedure. 17. The procedure for subsoil replacement is the same as described above i.e. subsoil is delivered by dump-trucks running over the substrate and end-tipping the soil in heaps. These are then levelled out either by an excavator or light tracked bulldozer as per Sheets 4 or 15 of the Guide. Figures RPS 1, RPS 2 and RPS 3 show a bulldozer being used and the sequence of operations described below also assumes this, and should be re-interpreted for a situation where an excavator is used instead. 18. If a bulldozer is used to level out the subsoil, there may be some residual surface compaction. This can either be removed by deep subsoiling after topsoil replacement or preferably before topsoil replacement either by a light tracked bulldozer fitted with tines or by an excavator whose bucket has been replaced by a tined implement. These are described in Sheets 18 Soil Decompaction by Excavator Bucket and 19 Soil Decompaction by Bulldozer Drawn Tines of the Guide respectively. 19. If compaction is restricted to only the surface few centimetres, as is likely to be the case, then sufficient loosening can normally be achieved simply by "combing" the surface with a toothed bucket on an excavator arm (Sheet 18).

67 20. The modified method differs from the dump truck and excavator/bulldozer methods described in the Guide in the method of topsoil placement. This is done in the modified method by delivering topsoil with dump trucks. However, instead of tipping it alongside or attempting to drop it onto the edge of the replaced subsoil strip, they build a relatively thick "peninsula" of topsoil progressively out over the centre of the area of respread subsoil. This is done by the dump trucks reversing along the topsoil "peninsula" and loose tipping the topsoil at the end, thus progressively extending the "peninsula" (see RPS 1). 21. Accordingly the method is often referred to as the Peninsula Method, assuming that the heap is constructed down the centre of the area being restored, as on RPS 1, 2 and 3, and the soils pushed to either side. However, the method is equally applicable to a situation where the heap of topsoil is built along the entire edge of the area being restored and is then pushed out over it. Thus the method might usefully be referred to in future as the Peninsula or Lateral Heap Method. 22. The amount of topsoil to be built into the peninsula must be calculated in advance from the area of the section being re-instated and the final spread thickness of topsoil required. If the topsoil is in a lateral heap then the volume does not necessarily have to be calculated in advance. It can simply be spread out as far as possible to the specified thickness before the operation is repeated. 23. When all the topsoil needed has been delivered, a light tracked bulldozer is used to spread out the soil from the "peninsula" or lateral heap to the required thickness over the rest of the section being re-instated in the same way as described in Sheet 15 of the Guide and as shown in RPS This operation will largely remove any compaction caused to the topsoil during the building of the "peninsula" or lateral heap but any remaining compaction can be removed by loosening with a tined implement (see Sheet 19 of the Guide), by using an excavator bucket fitted with tines (see Sheet 18 of the Guide) or as part of the subsequent agricultural operations. 25. It should be noted that although some compaction will be caused by the operation of the bulldozer during both subsoil and topsoil spreading this will be far less than if trafficked by wheeled machinery. In many cases, the moving around of the soil by the bulldozer blades will loosen the soil sufficiently. If deemed necessary the de-compaction methods mentioned above can be employed.

68 26. In many cases, the slightly consolidated, but not compact, surface left after blading out with a dozer is beneficial as its greater load bearing strength helps in the early years of arable cropping whereas completely loose tipped subsoil may be too loose and result in wheel sinkage and rutting. 27. It should also be borne in mind that, in general, topsoil is a more robust material than subsoil. It is regularly disturbed and run over during normal agricultural operations and is always sufficiently near the surface that any deliberate loosening can be easily carried out. 28. The sequence of operations in the modified procedure is as follows, assuming that no loosening of the substrate is required (see RPS 3):- Ensure that the soils which are to be respread are in a suitable condition for mechanised handling Mark out the section of the site to be re-instated. This is normally about 1-2 hectares in area and need not be in a narrow strip. Bring subsoil by dump-truck to the section being restored and loose tip it at the edge of the working area. Work back from the furtherest point to be restored so that dump trucks only run over substrate and not over any replaced subsoil. Spread out the tipped subsoil to the required thickness as indicated by marker boards using a light tracked bulldozer which will be the only machinery allowed on the respread subsoil. If it is considered necessary, remove any surface compaction either by bulldozer drawn tines or by tines fitted to an excavator arm. Calculate the amount of topsoil required to cover the section being worked on to the required thickness.

69 Progressively bring this volume of topsoil by dump-truck to the section being restored and begin to build a peninsula of topsoil out towards the furthest point of the section being restored (i.e. the reverse direction to which the subsoil replacement was done). Alternatively, build a lateral heap along the entire edge of the area in the same general manner. Make the dump trucks reverse along the topsoil "peninsula" and loose tip the topsoil at the end, thus progressively extending the "peninsula". If the lateral heap method is used it should be build up by dump trucks reversing across the heap and loose tipping at the edge. In either case do not allow the dump trucks to travel over any of the respread subsoil. Depending on circumstances it may be necessary to use a light tracked bulldozer to create a suitable running surface for the dump-trucks. When all the soil needed has been delivered, use a light tracked bulldozer to spread out the soil from the "peninsula" or lateral heap to the required thickness over the rest of the section. Inspect the soils and institute any soil loosening operations considered necessary. 29. If a loose, permeable substrate is required, then running over it with dump trucks must also be avoided. In such a case then the same peninsula or lateral heap method should be used for subsoil delivery and spreading as for the topsoil method described above.

70 Adrian Rochford HND (Agric.), MI Soil Sci., FQA

71 Adrian Rochford HND (Agric.), MI Soil Sci., FQA

72 Adrian Rochford HND (Agric.), MI Soil Sci., FQA

73 Adrian Rochford HND (Agric.), MI Soil Sci., FQA

74 Adrian Rochford HND (Agric.), MI Soil Sci., FQA

75 Adrian Rochford HND (Agric.), MI Soil Sci., FQA

76 Figure RPS 1 Modified loose tipping method: Topsoil delivery and peninsula building Figure RPS 2 Modified loose tipping method: Topsoil spreading Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

77 Figure RPS 3 Modified loose tipping method: Sequence of operations Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk

78 Appendix 7 SOURCES OF REFERENCE Ministry of Agriculture, Fisheries and Food (1988) Agricultural Land Classification of England and Wales: Revised guidelines and criteria for grading the quality of agricultural land. MAFF: London. Meteorological Office (1989) Climatological Data for Agricultural Land Classification. Meteorological Office: Bracknell. Soil Survey of England and Wales (1983) Sheet 3, Soils Midland and Western England, 1983: Harpenden. Soil Survey of England and Wales (1984) Soils and their Use in Midland and Western England SSEW: Harpenden British Geological Survey, Geology of Britain Viewer, 1: Geology map Adrian Rochford HND (Agric.), MI Soil Sci., FQA adrian.rochford@live.co.uk