The Water Tower

The Water Tower
The Water Tower at Dusk

Tuesday, September 30, 2014

Extract from IF Report on Ironmills Steps. Vegetation Assessment


VEGETATION ASSESSMENT

General
As part of the study, a vegetation assessment was undertaken to identify whether the existing vegetation was contributing to or negating against failure of the slope and whether there was opportunity for landscape related works to contribute towards a potential solution. The following section summarises the results of this assessment.
Roger Clark MCLI, a Technical Director of Ironside Farrar with over 20 years practical experience, visited the site on 21st March. Weather conditions were dry following heavy rain earlier in the day.
It is noted the existing topographic survey records the position of areas of slippage but does not record the position and girth of all trees in the study area. This will be required if the project progresses to a further stage together with a tree survey to record species and condition.

Site Assessment
The site is steep with a path down to the river and sits over an exposed rock face gorged out by the River Esk. Tree cover is not particularly dense and comprises mix of mature specimens over 1.5m girth with some new growth. There are a few intermediate sized trees.
Most trees are deciduous, and although a few conifers and evergreen species are present in the area, new growth appears to be mainly birch. Understorey vegetation is well developed, notably ivy. Many trees are in poor condition and much deadwood was noted, but this is not seen as a contributor to the slope stability issue.
The paths are enclosed by fences. These are in the main concrete post and wire, although some vertical bar fences are also present. It was noted that the mature tree at the upper dogleg bend appears to have arrested further slippage from above by the way the vertical bar fence and path have both slewed into the side of the tree. See photograph overleaf. The immediate area to the downslope side of the tree showed no sign of slippage, suggesting the tree was stable when the slip occurred.

Conclusions
Felling the trees will not assist in overcoming slope stability problems at this locus as the soil is not stable. Trees are not the problem and are possibly assisting in maintaining ground stability, particularly on slopes less than 50% (1:2).
There is nothing to suggest that the trees are a problem on the steeper slopes (80%) above the dogleg path where there is at present no slippage visible.
It is considered that removing trees may increase the potential for slippage to occur as an unvegetated slope offers far more opportunity for surface water runoff to develop momentum which may lead to scour of the surface and different type of stability problems.

Trees will always fall off the cliff face into the river as the overlying clayey sands and gravels erode and slide toward the cliff. This is a naturally occurring feature of gorges overlaid by softer material.

It is recognised that trees in good health may have better root systems than those in poor condition and dead wooding and canopy thinning of mature trees may assist in promoting healthy vigorous roots and stimulate regeneration. Coppicing of smaller suitable trees such as birch may also assist in stimulating root development.

Bioengineering techniques should also be considered such as brush layering at the base of slip areas using live willow whips possibly in conjunction with live willow stakes and fascines made from woodland thinnings. There has been a resurgence in the use of this traditional and low cost method of stabilising ground in recent years. Drawing 8162_701 identifies a typical arrangement for this type of technique.

The photograph below shows a rudimentary facine made by utilising the concrete post and wire fence and woodland thinnings already exists at the base of the steep slope above the dogleg path. ***


Recommendations
- No felling of trees to occur.
- Dead wooding and crown thinning of mature trees is recommended.
- Coppicing of smaller trees less than 500mm girth is recommended
- Bioengineering opportunities to be further examined for implementation in next plant dormant season (autumn).


*** - this is the wood pile created on water tower wood…….ahead of our time! photograph could not be copied over though.



Update from Midlothian Council re Ironmills Steps



Council agrees Ironmills steps repairs


The council has agreed to spend around £58,000 in total to tackle the continued landslip problems affecting the steps at Ironmills Park in Dalkeith. 
Published on 
ironmills damage to steps
At a full council meeting today (Tuesday), councillors heard the findings of a report by a specialist engineer, Ironside Farrar on the state of the slope and possible options for the reinstatement of the steps and path.
 Councillor Derek Rosie, cabinet member with responsibility for parks, said: “The steps have been closed and off limits to pedestrians since March 2013.
 “We’d like to thank pedestrians for their patience as this is the main pedestrian access route from Cemetery Road in Dalkeith to the park.
 “Hopefully, we are now on our way to tackling the issue of this closed access route. As the landslip is currently still moving, it is not possible to put a definite timescale on when the steps will reopen, however we are hopeful that the work can be completed by early summer 2015.”
 The money will be spent on halting the landslip and fixing the steps.
 Councillors were told there were three options, the first was to do nothing, the second was to spend a total of around £58,000 on carrying out a series of smaller works (localised solutions) while the third option was to spend between £225,000 and £675,000 on a full engineered solution to the landslip.
 Councillors agreed the second option was the way forward as the third option was beyond the £50,000 initial repair estimate and would also look unsightly in an important historical area.