Drainage of the Lake in Marden Quarry

Email added 18 December, 2016

 Marden Quarry - Sandbags

This page, added 21 February, 2016, illustrates the effect of North Tyneside Council (NTC) putting sandbags over the lake outlet grille in mid-July, 2015. There are two sets of photographs; the first set of 6 are with the sandbags left in place; the second set of 8 photographs were taken after they had been removed and the outlet cleared in mid September, 2015. An exchange of emailed messages with the Project Engineer responsible for having the sandbags placed over the lake outlet grille is given below the sets of photographs. More information about the photographs will be shown by floating a mouse cursor over eaxh of them.


After the sandbags had been removed.

Sent: Tuesday, July 21, 2015 2:35 PM
Subject: RE: Sandbags Blocking Outlet (Marden Quarry) [Scanned]

Dear Mr Smith,

For your information the sandbags have been placed in front of the culvert grille in order to keep the water level in the Quarry at a constant depth. This follows a request from the Park Wardens who had raised concerns about the low water level. As you are aware the outlet pipe has a sluice gate which has an issue on it which prevents the gate being raised. This gate allows the water level of the lake to be controlled during the Winter & Summer periods. The intention is to remove these sandbags at either the end of Summer or once the Sluice Gate has been repaired whichever comes first.

Regards

Andrew Burnett
Project Engineer

Sent: Wednesday, July 22, 2015 6:26 PM
Subject: Re: Sandbags Blocking Outlet (Marden Quarry) [Scanned]

Andrew,

Thanks for your note (above) re the sandbags.

At the end of this note I have copied in the most recent entry I made to the page www.oldexmothians.co.uk/rls/temp4/MardenPark.htm. The lake level has remained low since the middle of May and there has been no sign since of the blanket weed that caused problems of blockage of the wire mesh during late spring and summer last year. This has been attributed to low rainfall earlier this year and lower than usual Spring temperatures.

Anglers would prefer a greater depth of water than when the jetty at the NW edge is uncovered - the deeper the water - the bigger the carp grow! It has been estimated that the water depth is 1 - 2 ft less than it was 40 years ago when the lake was created, due to organic debris from the surrounding vegetation and settlement of silt from the water fed into the lake over this long period. In addition, the unauthorised blockage of the outlet towards the end of November, 2012 caused a prolonged period of flooding that eroded the banks of the lakeside and islands, causing the depth adjacent to these to decrease. The greatly reduced depth of the lake increases the risk of swans in particular, reaching down to bait/hooks lying near the bottom.

Anglers report that some 20 -30 years ago the lake level would normally be such as to uncover the jetty and with a depth great enough to avoid risks to wildfowl due to angling (which has been allowed since the park was opened in the early 1970s).

With the sluice gate stuck in its current position, the lowest level is determined by the bottom of the hole where the old grille was fitted. From the measurements recorded below the "normal" low level would just cover the jetty leaving (only) 10 cm rise in level before there is a risk of water spilling over the rebuilt wall along the NW edge. Bearing in mind the problem of blockage of the wire mesh due to blanket weed and the future addition of water from a flood prevention scheme upstream of Rake Lane (that NWL have yet to design) it would be worthwhile to raise the NW edge by another 10 cm # or so using stones with backfill, but incorporating one or two ramps for the birds to gain easy access to the (formerly) grassed area.

One of the BWAC (Big Waters Angling Club) bailiffs has learned of an alternative to dredging to remove silt and other organic material by discussion with the operator of fisheries in the NW of England. I have suggested he approach the council at senior management level to explain the process.

I have advised Jerry Dronsfield that clearance of any outlet grille blockage by such as blanket weed should be done according to need rather than routinely as frequently as twice a week. The need can be judged at present as when the jetty is fully covered - a rise of only 8 cm above the current minimum.

Hope these notes are helpful!

Regards,

Robin Smith

# This is far less than will be required to avoid frequent flooding taking into account the increased water flow into the lake from surface water drainage due to developments beyond Rake Lane.

Lake Level

This North Tyneside Council internal email # from Mr. Burnett (Project Engineer) to Mr MacDonald (Complaint investigating officer) gives some answers to questions raised in connection to the reason for installing sandbags. The level of the lake reported was not unusual for a dry period if the outlet grille is kept clear. It is this level that is needed to reduce the risk to flooding of the surrounding area were there to be a storm or a sustained period of rainfall.

To: Colin MacDonald
From: Andrew Burnett
Sent: 30 November 2015
Subject: RE: Stage 2 Complaint Ref: 101370770: Management of Marden Quarry

Colin

In answer to the questions relating to Marden Quarry:

lb. Siltex is used in improving the quality of the water as such it would be our Biodiversity Officer & Asset Team to advise on its suitability.

1c. The Sluice Gate is currently inoperable, we initially thought the problem was down to the mechanism being seized shut so we employed a contractor to attempt to free it. Unfortunately when carrying out this work we discovered it was a more substantial issue which would involve the installation of a new sluice gate mechanism. The last I heard on this was that Richard Martin was going to get a quote to carry out the repair which he was then going to go back to lan Lillie to see if he had any money in his budget to undertake the repair. Subsequently we have started discussions with Northumbrian Water who are looking to make improvements to the drainage network in the area which may involve the quarry and as part of there proposals its more than likely a new culvert and grille would be installed though these discussions are still in the early stages.

1d. The only part of the Quarry which I am responsible for is the point where the water discharges into the culvert so the state of repair of the embankments is not something I would be involved with.

2f. The mesh grille was installed at the request of lan Lillie's team and the Park Wardens, to prevent wildlife from becoming trapped within the culvert.

3. As the sluice gate is not working the only method we have for controlling the height of the water in the Quarry is by placing sandbags across the entrance to the culvert. During the Summer a request came in from the Park Wardens to raise the height of water in the quarry as the wildlife was suffering due to a lower level of water in the quarry due to evaporation and low rainfall. Before installing the sandbags I contacted Pixie Phelan & Sam Dand to verify the method we were proposing to artificially raise the height of the water was suitable and they confirmed that this acceptable. I also made everyone aware that this wasn't a permanent solution and the sandbags would be removed by the end of September. Regarding raising the height of the lake edge or dredging the Quarry this would be something the asset team would need to comment on as this falls within their jurisdiction. Unfortunately if we are required to raise the level of the lake again next year the same issue with flooding around the edge will happen again. The sluice gate if working will allow the level of water to be raised but doesn't allow us to empty the lake or even to drop the level of the water beyond the level of the outlet point.

Regards
Andrew Burnett
Project Engineer

# Obtained via a Freedom of Information (FOI) request.