Minerals Advisor Recommendations

Wardell Armstrong Tudor House, 16 Cathedral Road, Cardiff, CF11 9LJ United Kingdom Telephone: +44 (0)29 2072 9191 www.wardell-armstrong.com Our ref: DNH/PA18-01205-B/01 Date: 20 December 2018 Your ref: Mr Dave Roberts Department of Environment, Food and Agriculture Thie Slieau Whallian Foxdale Road St. Johns Isle of Man IM4 3AS Dear Dave, 18/01205/B – Creation of a swimming pool, Thie Y Chleree, Church Road, Garff

BY EMAIL

I refer to the above planning application, the letter dated 13th December 2018 from Mr. I. K. Bleasdale addressed to J. Callow and our recent telephone conversation concerning the same.

Mr Bleasdale makes some valid points, namely:

• 1. The proposed swimming pool development lies in close proximity to a shallow mining tunnel;
• 2. There has been a suggestion of past instability associated with the tunnel;
• 3. There is potential risk that the weight of the water in the pool might cause a collapse; and
• 4. The tunnel is known to drain former underground mine workings.

We have reviewed the map of Maughold Village showing the believed position of the mine workings provided by Mr. Bleasdale.

The map extract has been scanned and superimposed onto the Ordnance Survey digital map of Maughold. The alignment of the adit to which Mr Bleasdale refers has been digitised onto the digital map as well as the approximate location of the swimming pool. A pdf copy of the plan is attached.

We have no information to confirm the accuracy of the position of the mineworkings, hence the position should only be taken as being approximate. You will see that the mine adit lies to the north of the proposed swimming pool. The linear distance between these features is approximately 5 metres.

In order to establish whether the mine adit is a potential risk to the proposed development we would ideally need to know:

• a) the actual position if the mine adit;

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• b) the depth to the floor of the adit;
• c) the depth to the roof of the adit;
• d) the nature of the rock overlying the adit; and
• e) the level of the existing surface of the proposed swimming pool and the depth of the pool.

Information on items a) – d) is not known and hence it is not possible to establish whether the swimming pool lies within the ‘zone of influence’ from the mineworking and is at risk.

The worst case scenario is that the pool lies within the ‘zone of influence’ and if there is insufficient depth of cover between the base of the pool and the roof of the adit, plus the intervening strata is not of sufficient strength, then there is a risk that a potential collapse could occur.

As Mr Bleasdale has alluded to, the adit drains old mineworkings and if a collapse were to occur there is the potential for the mine water to build up behind the collapse and a ‘blowout’ could occur. The location of the blowout could occur at any location ‘upflow’ of the collapse and could put properties in the location at risk.

Recommendation DEFA holds information which suggests that the proposed development could lie within close proximity to old mine workings. Prior to any site development, appropriate site investigation should take place to ascertain the presence of any mine workings that could underlie the property in which the development is to take place. We would recommend a non-intrusive investigation in the form of geophysical survey. If the results of the investigation reveal the presence of mine workings then appropriate measures will need to be incorporated into the design of the proposed development.

Liability Under the Minerals Act 1986, ownership of all mines and minerals is vested with the Department of Environment, Food and Agriculture (DEFA). The developer is advised that in accordance with the provisions of the Minerals Act 1986, should a collapse of the mineworkings occur as a consequence of the proposed development, DEFA will not be held liable for any damages caused.

Regards Yours sincerely for Wardell Armstrong LLP D N HUGHES TECHNICAL DIRECTOR [email protected] DNH/PA18-01205-B/01 2 20 December 2018