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| Reserve 1 (Southern Quarry) | Volume (m³) | Conversion Factor (Tonnes/m³) | Gross Tonnage |
| 10,212 | 2.65 | 27,000 |
In producing a final quarry profile, I first took account of the 10m standoff from Raad ny Foillan and the 5m standoff from the adjacent field boundaries. These standoffs are referred to the Mining Agreements from the DED.
As you will be aware, there are areas of the quarry where workings have encroached within such standoffs. As a result, in these areas I have utilised the existing quarry slopes. However, in other areas where the standoffs can be observed, I have designed the quarry walls with a 1 in 2 slope (1V:2H) through the superficial deposits until they intersect rock head and then used a 1 in 1 (1V:1H) batter through the solid rock. Normally I would use a steeper slope such as 1:0.5 (1V:0.5H) in solid rock but as the intention is leave the geology exposed then given the height of the face in the southern part of the quarry, I thought it advisable to slacken off the overall slope.
I have shown the base of the quarry at c. 1.5m AOD which is based on the level of the outfall from the quarry. Naturally there will be areas where the quarry floor will be above and below this datum due to the configuration of the bedding planes.
Please note that I have split the reserve into two areas, Reserve 1 (southern quarry) and Reserve 2 (northern quarry). I have used as the dividing line the igneous dyke intrusion which bisects the quarry and marries in with the intrusion observed in the Bay.
Reserve 1 is fairly simple to quantify as much of the existing limestone is exposed. Comparison of the Limestone Reserve Area 1 to the final quarry profile yields an in-situ volume of 10,212m³ (SEE ATTACHED VOLUME REPORT) I am aware from our royalty audits that you apply a conversion factor of 2.65 tonnes/m³.
The estimate of Reserve 1 is shown in the Table below:
Reserve 2 was more difficult to quantify as much of the area is overlain by overburden mounds and in-situ superficial deposits and the actual top surface of the limestone is largely unknown. In order to create a surface model for Reserve 2, I looked at contour information in our archives which reflects the original ground profile before quarrying began. This data allowed me to produce a profile representing the original surface where the main overburden mound in the north of the quarry rests. Measurements taken in the quarry indicated that the average in-situ depth of superficial deposits and weathered rock overburden to rock head was c. 1.2m thick. The original ground levels were then lowered by 1.2 metres to create a limestone surface profile. Naturally, the model is entirely conceptual but is probably the best we can do at the moment in the absence of any data to confirm the depth of overburden beneath the mounds.
Comparison of the Limestone Reserve Area 2 to the final quarry profile yields reports an in-situ volume of $31,818\mathrm{m}^3$ (SEE ATTACHED VOLUME REPORT)
However, given the uncertainty regarding the thickness of overburden in this area, it might be sensible to apply a recovery factor to account for potential losses. My recommendation would be to use a $90\%$ recovery factor – hence, the in-situ volume reduces to $28,636\mathrm{m}^3$ (i.e. $31,818\mathrm{m}^3 \times 90\%$).
The estimate of Reserve 2 is shown in the Table below:
Estimate of Remaining Reserves = 102,880 tonnes.
A comparison of the latest topographical survey against the final quarry profile yields a Gross volume of overburden and limestone on site of $74,400\mathrm{m}^3$. (SEE ATTACHED VOLUME REPORT)
From the limestone reserve assessment, we know that the volume of limestone to be c. $42,000\mathrm{m}^3$ (i.e. $31,818\mathrm{m}^3 + 31,818\mathrm{m}^3$).
Hence the volume of overburden is c. $32,400\mathrm{m}^3$. Please note that this volume comprises in-situ soils; in-situ weathered overburden; Scarlett Volcanic Series rocks and screened overburden and overburden already in storage.
It is assumed that DOI Planning will allow the complete removal of overburden from the site. You will see below that I have incorporated into the Restoration Plan a buttress which is located along the eastern wall of the quarry adjacent to the Raad ny Foillan footpath. The purpose of this buttress is a safety feature to 'mask' the existing wall. I estimate that approximately $3,100\mathrm{m}^3$ of overburden material is required (SEE ATTACHED VOLUME REPORT) to construct the buttress. I am conscious of the commercial arrangement you have with James Cubbon regarding the removal of screened overburden and waste limestone and it will be necessary for such a quantity of overburden to be retained. If the intention is to continue developing the southern part of the quarry then once the limestone has been removed in the vicinity of the eastern wall the buttress can be constructed fairly early on in the development of the quarry. This can form part of the progressive restoration of the site.
Neil Hughes
Technical Director Wardell Armstrong LLP 22 Windsor Place
Cardiff
Wales
CF10 3BY
Tel: 029 2072 9191
Fax: 029 2038 7261
www.wardell-armstrong.com
| Reserve 2 (Northern Quarry) | Volume (m³) | Conversion Factor (Tonnes/m³) | Gross Tonnage |
| 28,636 | 2.65 | 75,880 |
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