From the table of sites presented in Section 3.2, a total of 19 were examined, the three detailed ones have already been considered, the remaining 16 are now dealt with on a rapid assessment basis.
The tombolo that links the area of the school to the main Vatersay settlement is a very interesting landform. In addition to various natural sand slopes, wave action and effects of wind blown sand, there are on the western coast some examples of small backfilled sand quarries and general blow-outs where rubbish has been dumped.
From Plate 21 which is the junction of the dunes and machair grassland (to the West of the Road) it can be seen that former hollow and pits have been filled and re-vegetated. The only evidence to suggest that fill exists beneath the site is a slight degree of settlement, and the old rim of the pit is seen at ground level.
In Plate 22 which is the same pit but looking south east, fill can be seen at the base and consists of cars, building blocks, steel, batteries, fish boxes, tyres and wood. It would appear that the capping fill has not been sufficient and has been blown away over time. It is uncertain whether vegetation was used in this locality, but this is a good example of the extremes from successful revegetation to wind erosion.
Also on Vatersay there is a larger infilled hole with cars, but this was not located during the brief time available.
Summary
Generally the reinstatement at the main site is beginning to fail due to the inadequate fill and capping along the graded slope back into the sand hollow. The surface reinstatement appears intact although has slightly settled.
The Tangasdale Beach and adjacent sand pit perhaps deserves further detailed studies in the future up to a discussion paper.
The Landowner for this area, Mr. Hector MacNeill has been pro-active and instrumental over the past 20 years in reforming the beach dune system and reinstating the back dune area in addition to his own sand pit.
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From discussions with Mr. MacNeill, it would appear that the main emphasis for reinstating large pits and blow outs is to firstly create a barrier at the front end of the pit and secondly have an adequate supply of capping material to immediately cover any fill material.
This 'barrier' was formed at Tangasdale Beach using 45 gallon steel drums during the 1970's; to slow down wind blown sand movement and encourage deposits around and inland of the drums. Although some of the lines of drums have become re-exposed the amount of sand deposition and subsequent marram planting has stabilised this once eroding beach (Plate 23).
In addition at the beach, larger blow outs towards the rear of the beach were filled with crushed scrap cars and buried with inert fill. The fill at the time was in plentiful supply due to local civil engineering projects, however there has been a steady decline in the amount available during the 1990's.
The beach and adjacent burn are still fairly active eroding agents. The local Council has had to reinforce the eastern end of the beach (adjacent to the burn exit) with rock armouring to the south east of the hotel to prevent undue erosion at the toe of the sand dune? Further erosion appears adjacent to this rock armouring where the burn meanders around the sand bluff. Should the erosion from the burn increase, this sand slope with the nearby A888 may become eroded in the future (Plate 24).
To the east of the A888 and very well hidden from public vantage points is a large sand quarry and car dump belonging to Mr. MacNeill. The pit is still in operation and is expected to 'mine' approximately 7,000 tonnes of sand this year (declining from 11,000 tonnes in 1994).
The cars are initially dumped as 'shells' and are subsequently crushed when a large tracked machine becomes available, they are then buried with builders inert fill and capped with sandy topsoil and reseeded. The quarry is declining in output as the owner does not really want to exploit the steep sloped western edge adjacent to the A888 due to stability reasons. It was also noted that the water table was seen during our visit, which will obviously effect the quarry's operations (Plates 25 and 26).
A standard "MacNeill" reinstatement is expected here, although the fill and capping material would appear to be in short supply at present.
It is interesting to note with these sites (1 & 2) that more erosion has been detected on these west facing beaches, this could be attributed to the construction of the Vatersay causeway (Sound of Vatersay) which has increased the wave action on the beaches to the north and south of the sound (pers. comm Mr. MacNeill).
Summary
The reinstatement at the main beach site has been successful due to the amount of fill and capping material which was available at the time of the reinstatement works.
However, in places the original 'barrier' core of 45 gallon steel drums have been re-exposed although the landforms landward do not seem to have suffered.
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It was locally reported that backfilled sand holes existed near the beach. However there was no real evidence seen on the ground of these holes. The beach and machair appeared generally very tidy.
Adjacent to the main sand pit at Traigh Mhor for about 300 metres to the west exists a complex dune and blow out system (detailed description given in University of Glasgow, Coastal Research Group Report, February 1995). The general features have been mapped and are shown in Figure 12 of the above report. Adjacent to the main sand pit lies a long "blow out" measuring some 130 m long and varying in width from 22 m at the north end, 30 m wide in the centre, and 24 m wide at the south end. Although not a 'sand pit' under the terms of reference for this report, there are physical processes occurring here which are of direct relevance to the main sand pit (Plates 2 and 7).
The bottom of this blow out has a water main laid through it (probably in the last 20/30 years). This main has been originally an asbestos one although now it has been locally replaced and repaired using HDPE piping.
This water main has been exposed due to wind erosion in several places along its route in the blow out. It can be seen from Plates 2, 7, 8 (Main Report) that an elevated line of ground follows the pipeline.
This elevated ground may be the result of compacted backfill and general ground compaction during trench excavation which has made the general wayleave harder than the ground around, which has subsequently been lowered by continuous wind erosion. In terms of the wind erosion which has lowered the floor of the blow out, this is now effecting the adjacent slopes which are readjusting to match the lower floor. The eastern slope of the main blow out has developed a breach which joins the actual sand pit through the turfed crest of the dune (Plate 4).
Wind blown sand is spread over the area both to the north and the south. Although the Glasgow report recommends that these are natural processes occurring and should be left alone, it can be argued now, that both the water pipe and the reinstatement of the adjacent sand quarry are threatened.
Summary
The council have started to tip peaty material (believed to originate from local ditch clearance) into the blow out in an effort to begin to stabilise the southern end of the blow out and pipe track (Plate 9), the success of this should be monitored.
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Due to the proximity of the site to Traigh Mhor it was considered necessary to quickly view the various methods of sand and slope stabilisation along the sand dunes in this area. There have been various methods employed for catching sand, e.g. chestnut paling, wooden slatted fence, wooden fence with geotextile, and actual geotextile pillows. The former three have been used to catch sand at the entrances to dune blow outs while the later has been employed to both catch sand and stabilise a slope.
Summary
All methods have been quite successful with sand trapped to the top quarter of the sand fences. With the geotextile bags/pillows (Plate 27), the pillows have been successful in trapping sand, however there is no sign of any marram growth (as seen in the Stewart Angus & Mary M. Elliot Report) and also the wind has now managed to start eroding to the direct south of the top of the feature. If this erosion continues there will be just the geotextile feature left with a west-east blow out immediately to the South (Plate 28). None of these techniques should be used at the main sand pit sites.
Local contacts suggested a brief survey to be carried out at the various forms of reinstatement at Eoligarry jetty.
The land and dune system immediately north of the jetty comprises a dune system directly abutting the sea. At the southern end of this there is evidence of earth works, and reprofiling taking place (Plate 29).
The reinstatement consists of general builders rubble which has been profiled to match the surrounding dunes and then stabilised with marram grass, seeded grass and in places seaweed as a binder. In various places some clods of topsoil with grass have been placed on the slopes, which range from 45 to 65 in repose angles.
Directly infront of the reinstated dune face lies a well established sand toe (Plate 29) with marram grass established, and marram trapping sand (Plate 30).
Further along the beach to the north, the dunes are under wave attack and during the visit were seen to have vertical faces and slumped marram clods.
Whether these earth works are to replace wind and wave eroded sand or even quarried sand is unsure, but the reinstatement has been quite successful.
Summary
The site has been reinstated very well from a stability view point with vegetated landforms created. In addition a small sand toe has established on the seaward side of the 'dunes' which helps prevent wave erosion. Again it would appear that stability has been helped by having adequate fill and capping material.
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Although not a sand pit, this rock quarry has been used for rock aggregate and judging from its weathered appearance probably as a sand and gravel aggregate. The pit at present appears to be undergoing reinstatement and is generally being backfilled with inert fill e.g. rockfill, dirty peaty sandy gravel. Some topsoil and turves have been separated presumably for the final ground reinstatement.
Situated at the seaward end of the farm track and in an old sand pit of the dune system, this pit is a classic example of a "before" and "after" situation.
The "before" scene is really quite an eyesore and consists of scrapped cars, corrugated iron sheet, scaffold uprights, cookers, fridges, freezers, wheels, tyres, wooden pallets, window frames, mattresses and plastic.
The "after" situation to the north consists of regraded land which is now being cultivated and improved. To get to this situation the fill must have been crushed and then capped with an inert fill (probably similar to the piles on site, rockfill peat sand and gravel) and then further capped with perhaps sand and seaweed.
Much of the rubbish at this site could easily go to council owned landfills and really should not have found its way to this location.
Summary
If the landowner reinstates the remainder of the pit to match existing reinstatement then it will be barely detectable from a brief walkover. The advantage of the pit in this area is that it is some distance inland and well above the highwater and tidal action The main concern really will be achieving a sufficient depth of capping layer to prevent the fill protruding through the surface which is seen at other Western Isles sand pits.
Similar to Garrynamonie (Site 9) the Drimsdale site is situated at the seaward dune end of the farm access track. To the north of the track at the approx. location of 754,377 there are two sand quarries which have been backfilled and reinstated. The reseeding has been generally successful but the problem of the final capping layer not being sufficient is evident again. Surface debris in the form of stone, metal, plastic and wood is seen at the surface (Plate 33). One of the pits an old metal container (fridge?) corrugated iron sheet and a tractor battery are seen to litter the surface.
It would appear that little attention has been paid to the former quarry faces which are generally bare sand with slumped turves.
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Closer to the track there are two areas of fill without capping although one of them is quite old that vegetation has grown around the fill (Plate 34) whilst the second (Plate 35) is more fill than vegetation.
Summary
It would appear in this area that backfilling operations have suffered due to lack of fill. The reinstated pits both have surface debris appearing, whilst the smaller pits remain as surface dumps.
Situated midway between the two track ends of Grogarry and Drimore Farms at approximately 759,404. This area consists of a sand pit which has been recently used although it has now been left with no fill or no attempt to reinstate. A further pit nearby has been backfilled and reinstated.
The first pit has reached the water table and stopped, there is evidence of wind blown sand to the west and north, with the remaining sand slopes ranging from approx. 35 to vertical. Some slumped and eroded turves are seen with no attempt been made to replace then or reprofile the slopes.
To the north of this pit is an area of poor growth which marks the upfill and levelling of a frame pit. Again fill and rubble can be seen sticking through the thin topsoil and grass, the thickness and quality of the topsoil only supporting the poor growth. Adjacent to the pit there are piles of old tyres which may have originally been salvaged for re-use although now are just left on the ground surface.
The dunes in this area of the base are characterised by having infilled blow outs and former sandpits. It is uncertain if the blow outs were further exploited for sand during the construction of the base, however the resulting "reinstatement" is a further good example of how not to backfill sand dunes.
From Plates 36 and 37 the general fill is seen to consist of concrete, brick, block, iron, and occasional plastic. Some of the surface has sparce vegetation growing through, but in the main there is no cover at all.
Summary
It may have been the case that the fill was originally capped with sand that has blown away, and serves as a good example that all fill in these coastal areas should be well buried and well capped.
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At the northern end of the base there are two areas of interest, one a backfilled pit and the other general engineered slope reinstatement.
The sand pit is located at approximately 752,435 and is surrounded by the northern curve of the access road. It would appear to consist of general builders rubble and demolition material which has been subsequently capped with sand. Sitting immediately adjacent are piles of sandy topsoil ready to be used in the final capping. This is generally a well backfilled site. (Plate 38)
At the northern seaward end of the base the foredunes have been successfully reinstated using steel net gabions and rockfill. The angle of repose matches the adjacent sand dunes at 35. There is good sand cover to the gabion baskets and in places marram is seen to become established. Although not strictly a sand pit this is a good example of hard engineering works that has blended into the natural landscape. (Plate 39)
Summary
Both these sand workings appear to have been successful, the first due to the adequate supply of fill and future topsoil capping, and the second due to the accurate matching of sand slope to engineered (gabion) slope.
Culla was suggested by the SNH office at south Uist as an area where there may be backfilled sand quarries.
About midway along the beach and at the upper part of the dunes evidence of backfill started to emerge. Similar to the M.O.D. Base, it would appear fill has been placed in blow outs/sand quarries as a handy way to prevent the blow outs increasing in size. However the capping material has been insufficient and the fill once more is re-exposed. In general the fill consists of metal, wood and plastic, eg. 45 gallon drums, cookers, roofing, bicycles. (Plate 40) In this area at the crest of the dune there is surface fill again, mainly metal that has not been capped, although natural vegetation is seen to be growing through it.
Finally over the crest to the east there is a sand pit that has been backfilled and capped. It is identified by surface hummocks where the spoil heaps have not been spread, with occasional surface rocks and boulders. (Plate 41)
Summary
The dune component of this site is particularly ugly, and again illustrates the need for adequate fill and capping at a site. Further inland a pit has been backfilled although the cap has not been levelled and contoured yet. If there is surplus material here it should be used to bury the unsightly rubbish nearby.
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Sitting on the headland to the north west of the main Horgabost site is the present sand quarry.
From Horgabost village the impact of this development does not appear too drastic, however when viewed from the east on the A859 Tarbert road the extent of the wind blown sand is readily seen. (Plate 42)
The sloping sides of the sand pit need some form of capping to decrease the action of the wind. The vertical working face is only a small area of the whole exposed quarry and probably does not contribute more then 5% - 10% of the wind blown material. In places there are many cobbles and boulders exposed from the underlying till, the sand and till matrix has been stripped away from around the cobbles and boulders, leaving them as surface debris. (Plate 43)
The former surface vegetation could have been stored at this locality to use as a binder of the sand, but was not evident during this visit.
Summary
In the future the erosion of the site could cause problems and it may be prudent to encourage the landowner to begin thinking about some stabilisation methods.
The site was briefly walked over to gain views back to Horgasbost, and to appreciate the actual scale of the features of this part of the SSSI. A small dump is reported by (Ritchie 1989) near the graveyard, but time did not allow a visit.
The whole of the Opinan Machair system was surveyed during the 1970's and was included in the University of Aberdeen "Beaches of Wester Ross" for the N.C.C. At that time there were severe erosional problems here with large tracts of wind blown sand and sparse vegetation cover.
The picture now has somewhat changed with a good vegetation cover to the machair and only localised erosion.
From chatting with several of the locals and comparing the quarry and car photo from the N.C.C. report the actual former sand face was identified.
This former vertical face has been successfully reinstated for the majority of its length and now has established marram grass planted throughout. The repose angles of the reinstated slopes vary from 35 to 65 and do appear quite steep (Plate 44), however for the most they are stable.
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At the western end of the former quarry face over a distance of approximately 22m exists bare red brown sand with slumped and undercut slopes. It is unsure if this western end was originally reinstated or not. as there are no signs of any slumped vegetation on the slopes.
The adjacent burn which flows very close to the base of the sand slopes may in fact be responsible for instigating instability during flooding. This burn has now been re-routed away from the sand slopes as can be seen in Plate 44.
It is suggested therefore that the 22m of the sand quarry face and the adjoining section of the dune to the south is reprofiled to eliminate the vertical face and then replanted with marram grass to match the existing vegetation. It is seen that there are fairly steep angles to the already reinstated area however to minimise slumping it is recommended to go for an angle between 35 and 45 for this section of the face.
In addition further work is needed on the adjacent dune (some slope regrading and some organic rich sand/sandy topsoil to be spread on the bare sand surface). Further excavation works may be necessary on the adjacent burn in particular the "meander" at the base of the dune. If flooding continues at this location some form of toe may need to be engineered for the reinstated face.
Summary
Generally a good example of long term reinstatement. Future reinstatement should be carried out in the near future before for the erosion of the slopes and vegetation occurs. There is no 'dumped' material to complicate this site, and the reinstatement should include burn diversion, slope grading and re-seeding during the near future.
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