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DEPARTMENT OF TRADE AND INDUSTRY Safety Engineering Works – Abandoned Mine Entries General Method Statement
June 2003
Received 5.11.03 DOLGE 03 1641 Town and Country Planning Fits 1924 to 1999 PLANNING and BUILDING CONTROL DIRECTOR:
| Decision | |
|---|---|
| Initial Decision |
Review Decision
Appeal Decision
Amended
DOLGE 03 1641
Wardell Armstrong Engineering & Environmental Solutions
Engineering & Environmental Solutions DATE ISSUED: June 2003 JOB NUMBER: CA02141
PREPARED BY:
Richard J Gaunt Associate & Principal Mining Engineer
APPROVED BY:
Stephen C Wyatt Partner
This report has been prepared by Wardell Armstrong with all reasonable skill, care and diligence, within the terms of the Contract with the Client. The report is confidential to the Client and Wardell Armstrong accept no responsibility of whatever nature to third parties to whom this report may be made known.
No part of this document may be reproduced without the prior written approval of Wardell Armstrong.
22 Windsor Place, Cardiff CF10 3BY U.K. Tel: +44 (0)29 2072 9191 Fax: +44 (0)29 2038 7261 www.wardell-armstrong.com
Wardell Armstrong is a Partnership and a list of the Partners and their professional qualifications is open to inspection at our offices.
Wardell Armstrong is a member of the Wardell Armstrong Consulting Group which comprises Wardell Armstrong, Wardell Armstrong China Limited, Wardell Armstrong Laird Menzies Limited, CSMA Consultants Limited.
Head Office: Newcastle-under-Lyme. Other Offices: Camborne, Cardiff, Edinburgh, Hong Kong, Leigh, London, Newcastle upon Tyne, Sheffield, West Bromwich.
1.1 Background 1.2 Outline of Proposed Works
2.1 Introduction 2.2 Excavations 2.3 Construction of Concrete Cap or Plug 2.4 Backfilling Operations and Reinstatement 2.5 Fencing
3.1 Introduction 3.2 Measurements and Preparation 3.3 Installation of Grille/Gates 3.4 Installation of Stone, Brick or Blockwork Seal 3.5 Access Provisions 3.6 Warning Signs and Reinstatement
4.1 General 4.2 Site Supervision and Management 4.3 Duration of the Works 4.4 Hours of Work 4.5 Site Access 4.6 Water and Electricity 4.7 Fencing and Security 4.8 Protection of Existing Buildings and Services 4.9 Photographic Record 4.10 Environmental Management 4.11 Reinstatement of Sites 4.12 Health and Safety 4.13 Notices to Landowners and Other Bodies
| NO. | DESCRIPTION | SCALE |
|---|---|---|
| CA02141/01 | General Arrangement for Shaft Cap founded on Rockhead above lined shaft | Not to scale |
| CA02141/02 | General Arrangement for Shaft Cap founded on Rockhead above un-lined shaft | Not to scale |
| CA02141/03 | General Arrangement for Shaft Cap founded above Rockhead and lined shaft | Not to scale |
| CA02141/04 | General Arrangement for Shaft Cap founded above Rockhead and un-lined shaft | Not to scale |
| CA02141/05 | General Arrangement for Mass Concrete Shaft Plug founded on Rockhead | Not to scale |
| CA02141/06 | General Arrangement for Mass Concrete Shaft Plug founded above Rockhead | Not to scale |
| CA02141/07 | General Arrangement for Adit Grille, Gate or Seal | Not to scale |
| CA02141/08 | General Arrangement for Fencing | As shown |
| CA02414/09 | Warning Signs | Not to scale |
The Isle of Man has a long history of mining, evidence of which can be found throughout the Island. Surface and underground mining for a variety of metalliferous ores (including, lead, copper, zinc and iron) was carried out from the Bronze age up to the first half of the 19th century.
Under the provisions of the Minerals Act 1986 (an Act of Tynwald) ownership of all mines and minerals (with minor exceptions) is vested in the Department of Trade and Industry (DTI). Inspections have been carried out 166 mine entries (including both shafts and adits) out of a total of nearly 300 that are shown on Ordnance Survey topographic mapping and archive mine plan records for the Isle of Man. The inspections identified some mine entries that have been treated to make them safe, for example by placing secure caps on shafts, and also a significant number of untreated mine entries where physical works are required to prevent accidental or unauthorised entry and to make the site safe.
This General Method Statement describes the works proposed to make untreated mine entries safe and the measures which will be taken to ensure that the work is carried out safely and with the minimum possible environmental disturbance. The General Method Statement has been prepared in connection with the submission to the Department of Local Government and Environment of applications for planning permission in respect of the necessary engineering works. The General Method Statement provides a description of the proposed works and associated measures but is not intended to be specific to each mine entry that it is proposed to treat. Each planning application is therefore also accompanied by a Site-specific Method Statement which, for each mine entry, give details of the particular engineering works proposed, the proposed means of access to the site and any particular measures which are to be taken to protect the environment.
Where possible, the preferred method of treatment for a mine shaft is to construct a cap or plug over the shaft that will be founded, where practicable, on bedrock. Construction of such a structure requires excavation of the soil around the shaft and the casting, in-situ, of a reinforced concrete cap or plug, which is then covered with soil and the surface reinstated to its original condition. In some cases it may not be possible to found the cap on bedrock, for example where the soils or superficial deposits are very deep. In such cases an alternative design of concrete cap or plug is used.
Department of Trade & Industry, Isle of Man Government
Abandoned Mine Entries
In most cases, the abandoned mine shafts which are to be treated are obstructed with unconsolidated fill materials and there are no open voids near the surface which can be used by important wildlife such as bats or nesting birds. In such cases the cap will be constructed as a solid slab or plug and covered with soil. If there are voids present which may be used by bats or nesting birds, an opening in the cap can be constructed, with a suitable steel grille to allow wildlife to enter.
In some cases it is not practicable to construct a shaft cap. In such instances shafts will be made safe by the erection of a secure steel fence, accompanied by signage warning of the danger.
Adits
Adits are level or inclined mine entry tunnels and many are in an open condition. Adits may be made safe by a number of methods, including filling with concrete, but they are frequently refuges for wildlife and can be important for industrial archaeology. It is therefore proposed that each adit will be made safe by the construction of an engineered steel grille or blockwork wall at the entrance, securely fixed to the surrounding rock or tunnel lining. The design of the steel grilles will allow wildlife, including birds and bats, to enter freely. Where appropriate a secure gate will be incorporated into the grille to provide access for the purposes of future monitoring or study.
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The principal stages in constructing an engineered cap or plug over an abandoned mine shaft are as follows:
Excavations are required to investigate the position of the abandoned mine shaft. Once the location, dimensions and orientation of the shaft have been confirmed, together with the thickness and nature of rockhead and the overlying madeground/superficial deposits, excavations will continue until a shape is formed capable of receiving a concrete cap or plug as shown on general arrangement drawings CA02141/01 to CA02141/06 inclusive.
The excavations will be carried out using a mechanical excavator with a reach of at least 5 metres. A banksman will be present and attending the excavations at all times when an excavator is in use. Initially excavations will commence at the location of the surface collapse and continue to sufficient depth to confirm the presence of the shaft, its dimensions and any evidence of lining. Once the shaft is proven excavations continue immediately adjacent to the shaft to prove rockhead or the overlying materials to a depth of 5.0 metres. If it is proved to be impracticable to excavate to rockhead because of the presence of an excessive thickness of madeground and/or superficial deposits the engineer may instruct that a cap or plug be formed at a level above rockhead. The excavations will then be extended laterally as directed by the engineer and in accordance with one of the general arrangement drawings CA02141/01 to CA02141/06 inclusive, so that:
i) if necessary, a detailed examination of the shaft and surrounding ground can be carried out; and ii) an excavation, of the correct dimensions and orientation, can be formed to receive a cap or plug.
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Department of Trade & Industry, Isle of Man Government Wardell Armstrong Abandoned Mine Entries It is not envisaged that excavations will extend over an area greater than 10 metres in diameter from the centre of the shaft.
Topsoil and subsoil recovered during the course of excavations will be carefully stockpiled separately for use in subsequent reinstatement of the site.
Where excavations proceed more than 1.2 metres below existing ground levels or there are signs of instability it will be necessary to batter the sidewalls back to a stable angle or install temporary shoring/support.
The Contractor will provide pumps and pumping equipment to keep excavations free from water.
The Contractor will supply, fix and remove on completion any support to the sides of the excavations necessary to protect anyone entering and working in the excavation and so that construction of the cap or plug is not impaired by collapse of the surrounding ground.
Depending upon the findings from excavations, the contractor will construct a shaft cap, in accordance with one of the general arrangements shown on Drawing Nos. CA02141/01 CA02141/02. CA02141/03 and CA02141/04, or a shaft plug, in accordance with one of the general arrangements shown on Drawing Nos. CA02141/05 and CA02141/06. Typically the cap or plug will be in the order of 3 to 5 metres square.
Where filling of any open shaft or mine workings is required the supervising engineer will inspect and approve the materials to be used. The preference will be for the use of rock fill, free from soil and other organic matter. Fill materials will be picked up from a remote stockpile and placed in the shaft using an elevator/conveyor or mechanical grab/bucket attached to a machine with a horizontal reach of not less than 5.0 metres. Direct tipping will not be allowed.
Where necessary in order to form a suitable shape and surface for construction of the cap or plug, the base of the excavation can be in-filled with granular sub-base crushed rock (Type 1 material in accordance with BS6543) to reduce the excavation void.
Timber or plywood boards (formwork) will be used to form the shape of the cap or plug within the excavation. Then steel bars or fabric reinforcement will be fixed prior to placement of the concrete. Concrete will be supplied ready mixed to site, either
direct into the excavation, pumped or transported by way of a small dumper to the point where it is required.
All excavations will be backfilled as soon as possible after the completion of the works. Backfilling will normally be done with the excavated materials followed by the careful replacement of subsoil and topsoil to restore former ground levels. Some suitable, surplus, excavated material may be left slightly mounded over the excavated area to allow for any further possible settlement that may take place. In some instances a marker post may be erected above the cap in order that the shaft may be relocated, if necessary, in the future.
The Contractor will be responsible for the safe and proper disposal of any surplus or unsuitable excavated material or waste/scrap material from site, together with the importation of any additional material necessary to restore former surface levels.
Where it is not practical for a mine entry to be treated by way of shaft cap/plug or adit grille, gate or seal, a secure fence may be constructed in accordance with the general arrangement shown on Drawing No. CA02141/08.
Fence post uprights will be in galvanised 'T-section' steel, epoxy primed and powder coated (in dark green), set in 'FND 4' concrete mix as per BS5328 in a mass plug, 0.3 metres diameter and extending to 0.5 metres below ground level. The height of the fencing will extend no higher than 2.0 metres above existing ground levels. The chain link fencing (grade A, green, plastic coated, 50mm mesh, 4.75mm wire diameter, as per BS4102:1990 section 3) will be supported on tensioning wire (4mm diameter zinc coated spring steel as per BS4102:1990 section 2) run through holes drilled in the upright posts.
Every corner post will be supported by two braces set at 90° from each other and every second fence upright will be supported by a single brace in accordance with the general arrangement on Drawing No. CA02141/08. All the bracing will be constructed within the fence boundary and bolted to the upright post.
The fencing will encircle the mine entry so as to prohibit access by the public. The precise line of the fencing will depend on the particular site circumstances. In the main however the fencing will follow a line no more than 3.0 metres beyond any area of collapse associated with the mine entry.
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Department of Trade & Industry, Isle of Man Government Abandoned Mine Entries
Wardell Armstrong Engineering & Environmental Statistics
On completion of fencing a mine shaft warning sign (printed on aluminium), in accordance with the design shown on Drawing No. CA02141/09, will be firmly fixed to the fencing on all four outward facing sides.
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The principal stages in constructing a grille/gate or stone/brick/blockwork seal in an abandoned mine adit are as follows:
The Contractor will make detailed measurements of the adit entrance in order to determine its dimensions for the fabrication of the grille/gate or for constructing a blockwork/stone seal in accordance with the general arrangement Drawing No. CA02141/07. Prior to making measurements, loose rock material and/or debris will be removed from around the floor and sides to fully expose the adit entrance and prepare a clean sound surface to receive the grille or seal. Removal of vegetation will be the minimum required.
In the case of a grille/gate the bars will be of either mild steel, if fabricated on site, or toughened steel if pre-fabricated. The grille/gate will be treated to be resistant to rusting, either galvanised, epoxy primed and powder coated (dark green in colour) at the time of manufacture or coated with a dark green coloured anti-rust preparation on site.
The means of fixing of the grille/gate to the rock or lining at the entrance and the number of anchor points will depend on the particular site circumstances. The grille/gate will be anchored at each angle or corner and, if necessary, anchored along the roof line, sidewalls and floor. It may also be necessary to concrete the steel uprights into the floor or use concrete/stone block footings. The grille/gates will be designed to resist reasonable force in order that they are not susceptible to vandalism.
The grille/gate can be fitted to the rock by drilling a series of holes around the entrance and cementing in steel rods, which are then welded to the main grille/gate. Another method is to fit the grille/gate with angle irons or a rim of steel and pin it to the walls using rawl bolts. The heads of the bolts can either be rounded off or spot welded for additional security.
Where an adit is to be permanently sealed a plug is constructed inside the entrance comprising free draining stone ( 75 to 150 mm nominal size), packed tightly against the adit sidewalls and roof. The entrance to the adit is then sealed with grey concrete brick/blockwork walling or locally won stone, incorporating drainage arrangements to deal with any water discharge.
As illustrated on the general arrangement Drawing No. CA02141/07 it may be necessary to allow provision for man access in the adit grille/gate or seal. Such security measures will include the supply and fitting of a lockable padlock.
On completion a mine adit warning sign (printed on aluminium), in accordance with the design shown on Drawing No. CA02141/09, will be firmly fixed to the grille/gate or seal. Any excavated material or rock debris will be spread out evenly at the site, mounded against the adit entrance or removed and disposed of at an approved/authorised tip.
The contractor appointed to carry out the work will be instructed to take all reasonably practicable steps to minimise harm to the environment and prevent nuisance, in the form of noise, vibration, dust and water pollution. Prior to the commencement of work at each site the contractor will submit a detailed method statement and health, safety and environmental risk assessments for the approval of the supervising engineer.
The contractor will be required to use, wherever possible, materials from recycled or sustainable sources that will interact favourably with the existing environment.
On behalf of the DTI an experienced engineer from Wardell Armstrong will supervise the works on a full-time basis. The supervising engineer will monitor the works and ensure that they are carried out in accordance with the approved method statements and any other requirements.
The following contractual requirements will be placed on the contractor and enforced by the supervising engineer:
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The time required to complete site works in each case will depend upon the particular works to be carried out. It is expected that each adit which is to have a steel grille installed will require approximately 1 to 2 days of site work. Where a concrete cap or plug is to be installed over a shaft, the following work may be required:
The duration of these site works will typically be from 12 to 15 days.
Subject to any particular requirements of the Department of Local Government and the Environment the hours of working will be from no earlier than 0800hrs to no later than 1800hrs Monday to Friday and 0800hrs to 1300hrs on Saturday. No work will be carried out on Sundays, Public Holidays or during the hours of darkness, including any hours between 0800hrs and 1800hrs. Any working on Sundays and Public Holidays shall be subject to the approval of the Department of Local Government and the Environment and in any event no Sunday working will be outside 1000hrs and 1600hrs.
Where possible, access will be gained via existing roads or tracks and the minimum of temporary access tracks will be constructed. Such temporary tracks will only be necessary where heavy plant needs to be taken to a works site, over land where no suitable track or road is available, in order to avoid damage to soils. In such cases, it may, by agreement with landowners, be necessary to construct a temporary road by removing topsoil and laying crushed stone to form a temporary track.
Temporary access tracks where necessary, will be of the minimum practical width, typically 3.5 to 4.5 metres and will be provided with temporary stockproof fencing if required. The crushed stone will be laid over a geotextile layer to facilitate its efficient removal when the temporary track is removed. Following
removal of the stone and geotextile, the soils will be replaced, cultivated as necessary and, subject to the landowner's requirements, sown with an appropriate grass seed mix.
If supplies of water are required for site works, such as mixing concrete or grout/cement, the contractor will provide this either from a convenient local supply main, by agreement with the Department of Agriculture, Fisheries and Forestry and the Isle of Man Water Board, or by use of portable containers or bowsers.
Electricity for portable plant or power tools will be provided as required from portable generators.
The site of the works at each mine entry will be secured by the erection of temporary security fencing at all times when work is in progress. Notices will also be posted warning of any dangers.
The contractor will be responsible for consulting with the relevant statutory undertakers and establishing the location of all underground and overhead gas, electricity, water, chemical, telephone, storm water and foul drainage services, etc. likely to be affected by the works at each mine entry. The contractor will ensure that the position of any excavation is clear of all known existing underground structures, sewers, water and gas pipes, cables etc. In the absence of satisfactory information from the appropriate authorities the contractor will excavate a starter pit, by hand, prior to commencing excavation by mechanical means.
In some areas the works will be carried out adjacent to buildings and on grassed and hard standing areas. The contractor will therefore identify, prior to the start of any site works, such protective measures as are necessary to protect any buildings or surfaces from the effects of water, oil, diesel, trafficking, deposition of excavated material etc.
The contractor will be required to make a photographic record of the works at each location, to include all key stages of work, including:
i) Prior to the start of any site works, the condition of the mine entry and any surrounding area likely to be affected, including the access;
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ii) Excavation works, including the finished excavation prior to the emplacement of formwork and reinforcement;
iii) Construction of concrete shaft cap/plug, including placement of formwork, placement of steelwork, pouring of concrete and finished cap/plug immediately prior to backfilling;
iv) Clearance works to expose an adit entrance prior to measuring up for fixing an adit grille/gate or constructing a seal; v) Fixing of adit grille/gate and signage; vi) Construction of adit seal; vii) Erection of fencing and signage; viii) Completed site works, including backfilled excavations and reinstated areas. The photographic record will include the date when taken, the mine entry reference number and an indication of scale.
All work on site will be carried out in such a manner that the noise and vibrations emitted do not amount to nuisance. The Contractor will be instructed to employ the best practical means of minimising noise and vibration produced by site operations, including the following:
CAD2141
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duration and, in conjunction with the supervising engineer, dealing quickly with any complaints that may arise.
The contractor will employ the best practical means of preventing or minimising dust arising from site operations, including the following measures:
No burning of surplus materials will take place on site.
The contractor will employ best practical methods to protect all watercourses, including water in underground strata, against silting, erosion and/or pollution so as to not adversely affect the quality or appearance of the water or cause injury or death to animal, aquatic or plant life and/or damage to property and land, including the following:
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No trees will be felled, cut or otherwise disturbed without the prior approval of the Department of Agriculture, Fisheries and Forestry.
The Wildlife and Conservation Office of the Department of Agriculture, Fisheries and Forestry has been consulted about the proposed works and specific measures to mitigate effects on wildlife or habitats have been incorporated into the proposed works as necessary. Disturbance licences have been obtained to carry out works at certain sites and copies of these together with any other related details are included with the separate Site-specific Method Statements.
On completion of the works at each mine entry the contractor will be required to reinstate the site to its condition prior to the start of the works.
Site operations will be undertaken having full regard to the health and safety of all persons (i.e. workmen, supervisors, visitors and members of the public) involved with or affected by the works.
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Prior to commencing work at each mine entry a method statement and health and safety risk assessment that relates to the site specific circumstances and work to be carried out will be prepared. The method statement will describe, in as much detail as possible, the activities that will be undertaken and their sequence, the personnel who will be involved and their responsibilities and the equipment and materials that will be used. The risk assessment should identify the potential hazards that may be encountered and detail what systems of work and measures (e.g. gas monitoring equipment, use of safety harnesses, security fencing and notices) are proposed to secure the health and safety of all persons involved with or affected by the Works, including members of the public.
The permission of all landowners whose land is affected by the proposed works will be obtained before any work is commenced. All affected landowners will be given at least 5 working days notice of the start of work.
The following will also be given 5 working days notice of the start of work:
Access to the works for the purpose of inspection will be made available to officers of any of the above bodies at all reasonable times.
If any protected species or suspected archaeological remains or artefact is discovered in the course of the works the appropriate officers from these bodies will immediately be notified by the supervising engineer, who will have available relevant contact details at all times. A photographic record of the works to each abandoned mine entry will be supplied to Manx National Heritage.
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