gwent farmers renewable solar scheme ltd...• safe design level in 2060 (1 in 200 year defended...

Gwent Farmers Renewable Solar Scheme Ltd

Wentlooge Renewable Energy Hub Scheme, Newport, NP10 8SR

Flood Consequence Assessment

20th March 2020 V2

This report is based on the instructions given by our client. It is not intended for use by a third party, and no responsibility will be given to any third party. The consultant has followed accepted procedure in providing the services, but given the residual risk associated with any prediction and the variability which can be experienced in flood conditions, the consultant takes no liability for and gives no warranty against actual flooding of any property (client’s or third party) or the consequences of flooding in relation to the performance of the services.

18022 – Wentlooge Renewable Energy Hub, Newport - Flood Consequence Assessment

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Contents

1 Introduction

2 Site Location and Setting

3 Existing Site and Ground Conditions

4 Proposed Development

5 Flood Risk and Hydrology

6 Surface Water Drainage

7 Construction

8 Safe Access

9 Management and Maintenance

10 Policy

11 Conclusions and Recommendations

Report prepared by Hayley Burke – BSc (Hons) Approved by Clive Onions – BSc CEng FICE FCIWEM MIStructE MCIHT

Version history

Version Date Prepared by Approved by Comment

V1 13.11.19 HB CO Issued for Comment

V2 20.03.20 LJ CO Revised layout and response to NRW

comments dated 24.02.20

Issue history

Version Date Issued to Method

V1 13.11.19 Savills Email pdf

V2 20.03.20 Ditto Ditto


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1. Introduction

Gwent Framers Renewable Solar Scheme Ltd is proposing to develop a Renewable Energy Hub to

generate renewable energy from a site located southwest of Newport. The project is classified as

a Development of National Significance (DNS) within the application.

The proposed Renewable Energy Hub comprises a solar farm with a maximum total output of

49.9MW on a site of 129.9 ha.

The site is within Flood Zone C1, defended against tidal flooding but protected by significant

infrastructure, including flood defences. The proposed lifetime for the project is 40 years and flood

levels with appropriate climate change allowance have been made.

Natural Resources Wales (NRW) has been consulted and has provided the latest flood level

predictions, which was received on 17th April 2019 (NRW Ref: ATI-17266a).

This FCA has also been prepared to consider the impact of the solar farm on the existing hydrology

in the area, to show that flood risk is not increased off-site and that the solar farm is safe to

operate for its lifetime. It considers the construction and operation stages. This will not change

depending on the lifetime of the development.

The author advised on the approved Llanwern solar farm and the same principles agreed with

NRW and Newport City Council have been incorporated into this Flood Consequence Assessment,

but adjusted to be site-specific.

This V2 FCA follows receipt of the NRW consultation response CAS-107058-K8Q6 dated 24th

February 2020. A clarification telephone conversation has also been held with the author of the

NRW response. This V2 contains an updated site layout with modified boundary and an

environmental enhancement area. It omits the previously proposed wind turbines, and so some of

the concerns of NRW in their consultation response are overcome.

2. Site Location and Setting

The site is located between Newport and Cardiff, at NP10 8SR, approximately 350m southeast

from the edge of Marshfield and located below a pylon mounted electricity transmission line

which links the two conurbations. The site is approximately 435m northwest of the Bristol

Channel sea defences. The site lies entirely within the Caldicot and Wentlooge Levels Drainage

District.


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Fig 1 Solar farm site location outlined in red (Streetmap).

Fig 2 Site location showing low lying land, relationship with coast and pylon line running

diagonally across site – shaded to show the perimeter drainage. The blue land is dedicated

to Lapwing mitigation. (Streetmap).


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The area occupied by the proposed solar farm is rural low-lying farmland, mainly used for

grasskeep and grazing drained by man-made reens and ditches. The site and surrounding area lie

within the Wentlooge Level area, which comprises farmland with supporting farms, mainly along

the southern edge, served by the B4239.

The site is in the following setting:

• Northwest of the site is the main Cardiff-Newport railway line on shallow embankment,

beyond which the low-lying farmland continues, drained by reens and ditches. The fields are

divided by hedges and occasional trees. The community of Marshfield is located 350m

northwest of the site, and is being developed with new housing. The land rises beyond

Marshfield towards the A48 and A48(M)/M4.

• Northeast of the site is Hawse Lane. A new railway bridge has recently been constructed by

means of a small diversion of Hawse Lane. Beyond the lane is a reen, fields and the village of

St Brides Wentlooge, within continuing low lying farmland.

• Southeast of the site is bounded by the B4239 which serves many farm buildings, beyond

which is a reen and continuing low-lying land with several lakes, Peterstone Lakes Golf Club

and the Wales Coast Path, Breakwater and Bristol Channel. The site excludes Greenacre Farm.

• Approximately 430m south of the site is the coastline, which includes marshland which is

denoted as a nature reserve and a Site of Special Scientific Interest (SSSI). This is the boundary

to the Severn Estuary. Peterstone Great Wharf is also located south of the site. The land is

gently sloping downwards towards the estuary.

• The low lying farmland continues south west of the site, with Peterstone Wentlooge 1km

southwest, and many farms along the coastal edge, leading into caravan parks, business and

industrial estates at the edge of Cardiff.

The site setting can therefore be described as within a rural low lying area, some 850m from the coastal defences, with many farms and businesses nearer the coast, and new houses being built in Marshfield.

3. Existing Site and Ground Conditions

The proposed renewable energy hub occupies an area comprising fields with boundary hedges

and drainage ditches. The fields are accessed from the nearby roads, and then either through

fields or along tracks to give access to each field. The ditches are crossed by use of culverts. The

central southern part of the site includes ponds, as shown in the Streetmap plan above

The fields are used predominantly for grazing and for grass – there is little sign of arable crops

being grown. The total area of the proposed panelled area site is approximately 129.9ha.

An overhead electricity transmission line passes northeast-southwest linking Newport and Cardiff.


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Fig 3 Site superimposed on Satellite image, showing predominantly grazing land and grass keep.

Yellow broken line represents the high power electricity transmission line. (Google Earth).

According to the British Geological Survey (BGS) Viewer, the superficial geology comprises tidal flat

deposits of clay and silt; the underlying geology is Mercia Mudstone. The soil is recorded by the

Cranfield University Landis Soil Viewer as loamy and clayey, and is naturally wet. The plans below

show a uniform character of underlying soil, consistent with its location close to the coast and

historic reclaimed land. With the presence of many drainage ditches within and surrounding the

site, this would suggest that the underlying soil and geology generally has a low permeability with

high groundwater level.


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Fig 4 BGS superficial geology.

Fig 5 BGS bedrock geology.


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Fig 6 Cranfield University soils characteristics.

4. Proposed Development

The proposed development comprises pressed steel post mounted solar panel arrays positioned in

an east-west alignment.

The arrays are approximately 2.9m in height, with the lower edge approx. 1.0m above ground,

which varies with local undulations in the ground surface and flood levels (see later). The solar

arrays contain joints up and along the arrays to allow the individual panels to manage thermal

movement along the array, which are fundamental for thermal movement. These joints, combined

with the dominant slope of the arrays, break the smooth surface and encourage rainwater to be

dispersed off the array edge and avoids concentrated flows landing on the ground.


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Fig 7 Typical view of arrays, showing expansion/movement joints which distribute runoff. The

panels at Wentlooge will be further above ground level.

Fig 8 Typical cross-section through arrays. The height of the panel above ground level varies

with the terrain and flood level – it can be lower than 1m – often 0.8m height - provided

the array is above the design flood level.


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Fig 9 Plan of proposed renewable energy hub. Solar arrays are indicated in east-west grey lines.

The generous distances to all ditches/reens/main rivers can be seen. The green are ais an

ecological enhancement area.

The layout will include inverter units and occasional substations in cabins on concrete pads within

the site, which will be connected to cables in backfilled trenches. Each inverter is positioned on

legs raised above the base.

The cabin plinths will be founded on concrete pads with a 350mm thick granular base and

surround to ensure that runoff mimics the existing rainfall management characteristics and

infiltrates into the underlying soil.

Fig 10 Image of cabin on concrete bases and permeable gravel bed and surround (Hendre Fawr,

Merthyr Tydfil, July 2015).


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In the northeast of the site is the main grid connection to the overhead pylon mounted cables. To

the south of the connection compound will be a battery store area to satisfy the modern needs of

solar farms. The battery store is made up of batteries in sealed shipping type containers,

supported on legs on pads.

Fig 11 Typical high-quality sealed containers with batteries, on legs, with permeable gravel

surfacing (SAFT website).

The lines of raised batteries lead to a simple system for the batteries to be on two long 350mm

thick permeable granular strips, 300mm wider than the battery units to gather drips, with

grass/vegetation each side.

Fig 12 The Grid connection yard and two lines of batteries on two lines of permeable gravel,

located in the southwest of the site, both areas based on permeable gravel bed, with grass

surrounds.


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Underground cables will link the inverters, battery storage and grid connection. Where cables pass

under ditches a ‘no-dig’ technique method will be adopted, with the cable 1.5m below the bed of

the ditch. The proposed ‘No-dig’ techniques and depth below the ditches results in Land Drainage

Consent not being required. Where possible existing farm access ditch crossings will provide the

route for the cables.

Fig 13 Typical section of ditch crossing by cable.

In accordance with NRW guidance, deer fencing with large open mesh will be installed around

each of the solar farm groups. The fence will be raised 150mm above the general ground level, to

allow localised movement of surface water and to allow small fauna to move freely. The fences

will span ditches and allow free flow within the ditches.

Fig 14 Typical stock fence detail showing 150mm bottom gap for water movement and bridging

of reens and ditches.

In accordance with NRW guidance a buffer zone of 12.5m will be provided between the NRW main

reens and the solar farm equipment, including fences. The fence will be set not less than 7.5m

from non-main reens and ditches to comply with ecological considerations. A 5m access zone will

then be maintained between the fence and array structures, and between the fence and any

hedges, to allow for routine maintenance.


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Fig 15 Plan showing main reens in dark blue and site in broken red line. Plan supplied by NRW in

24th February 2020 consultation response.

The fields on which the solar arrays are located will be prepared and seeded to encourage

vegetation with native grasses and restored where construction has caused damage. The area

within the fence will become a haven for invertebrates, reptiles, amphibians, small mammals and

birds.

The site will be grazed seasonally by sheep at low density to prevent tall plants shading the panels.

The solar farm will be inspected and managed, and bare areas of earth will be seeded and

protected to encourage growth; tall plants will be controlled.

Vehicular access will use the existing access tracks where possible. New tracks will be formed in

permeable material. The extent of new tracks will be minimised. Access to the solar farm is for

maintenance and for safety reasons this will only be done when the weather forecast and

prevailing weather is dry and calm and safe for working. This will minimise the impact on the

ground conditions and reduce the risk to people from flooding. Access will be by suitable light

vehicles.

The tracks tend to green over due to low usage, thus maintaining permeability and providing a

varied habitat.


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5. Flood Risk and Hydrology

According to the Product 4 data (Ref ATI 17266a) obtained from Natural Resources Wales (NRW),

the site is located in Defended Flood Zone 3.

Fig 16 Site Specific Flood map from NRW, showing site mainly in Defended Flood Zone 3, but the

southwest are in undefended Flood Zone 3 (note the yellow line is the actual site

boundary).

According to the TAN 15 Development Advice Map (DAM), the site is vulnerable to tidal flooding,

and is categorised as being in Flood Zone C1, at risk of flooding but served by significant

infrastructure, including flood defences.

The source of the flooding is tidal and the area is protected by substantial registered defences for

which Natural Resources Wales (NRW) is responsible. The character of the defences shows that

they are at or above their target condition, with normal maintenance, and it is understood that

the concrete top is generally at 9.8m AOD. They protect the key commercial areas of Marshfiled,

Tredegar Park, and St Mellons.

There is no record of flooding in the area in recent times.


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Fig 17 Extract from TAN15 DAM showing the area at risk of tidal flooding protected by the NRW

managed defences (ie in Zone C1), with the solar farm in red.

Fig 18 Typical character of defences along Wales Coast Path in the vicinity of Peterstone

Wentlooge (adjacent the golf club, immediately southeast of site) (Geograph).

NRW was contacted for site specific flood data and responded in their correspondence (Ref: ATI-

17266a – Wentlooge, Newport). Predicted water levels have been provided for defended and

undefended scenarios. The defended scenarios take account of the existing robust defences. The

undefended scenarios take no account of the existing defences, in the case of failure, and assume

level terrain.


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The data includes predicted flood levels for 2015, 2090 and 2115 as well as interpolated results for

2019, 2094 and 2119. The information provided by NRW states that future levels were derived

using the model base year (2015) and adding the sea level rise values to the elevation values from

the model results. The sea-level rise predictions applied are reproduced below.

Fig 19 Extract from NRW data, Defended scenario, Median values (the site-specific values for this

site, for the flood characteristics NRW as advised for Llanwern).

Given that the lifetime of the solar farm is 40 years, the design level at the end of the lifetime

would be the level with climate change until 2059. The table below gives the climate change

allowances and the depth between 2090 and 2059 should be deducted from the 2090 level of

5.37m AOD.

Fig 20 Sea level rise values provided by NRW.

So the deduction is as follows;

Sea level rise 2090 – 2085 = 14.5mm x 5 = 72.5mm

Sea level rise 2085 – 2060 = 11.5mm x 25 = 287.5mm

Sea level rise difference between 2090 and 2060 = 360mm

Based on a design flood level of 5.37m AOD in 2090, the safe design level for 2060 would be 5.37m

AOD – 360mm = 5.01m AOD.

So the design flood level for sensitive equipment, based on the lifetime of the project at this site

is recommended as 5.01m AOD.

It is important to recognise that the sea level rise figures are estimates based on climate change

considerations by specialist Agencies, and these are used as a guide for planning – the actual

implications of climate change and the potential man-made mitigation measures are unknown.


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The fact that the solar farm has a design life of 40 years is significant in this context, and analysis

emphasises the reduced risk of flooding due to the customary short lifetime of the solar farm

installation and clearly the estimates for shorter lifetimes are more reliable and have less impact.

Fig 21 Defended interpolated results by NRW at the site.

For completeness, the present day (2019) defended flood level has been calculated by NRW to be

4.08m AOD during the 1 in 1000 year event, with no flooding in the current day 1 in 200 year

event.

These levels have been considered in light of the existing terrain, using Lidar, which is also the

survey NRW uses to inform its flood modelling.

Fig 22 Lidar image of the site giving levels. Note levels are generally above 4.0m AOD and the

Grid yard and batteries are in an area at 4.25m AOD.


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Summary of levels:

• Robust coastal flood defences 9.8m AOD

• Predicted sea level in 1 in 200 year tidal event 2020 8.415m AOD



• Current day 1 in 200 year defended tidal flood level Does not reach site

• Current day 1 in 1000 year defended tidal flood level Does not reach site

• Safe design level in 2060 (1 in 200 year defended event) 5.01m AOD

• Existing ground levels 4.0m – 5.75m AOD

• Proposed base of solar panels (low edge), battery containers, etc 5.01m AOD

• Proposed lowest level for sensitive equipment 5.31m AOD

• Height of arrays above ground level (low edge) Varies approx. 1.01m and shorter

• Minimum height of sensitive equipment above ground 300mm

The above summary shows that the robust sea defences are over 1m above the predicted flood

level in the design 1 in 200 year tidal event, at the end of the lifetime of the development in 2060.

The site is therefore considered to be safe from flooding for its lifetime and the proposed

development is at low risk of flooding.

The solar panels, associated equipment and battery container units will be located above the 1 in

200 year flood level, at the end of the lifetime of the proposed development (ie 2060).

The arrays will be on legs usually about 1.0m high, but this will vary with the undulating ground.

The freeboard for the arrays is therefore from 0mm to potentially about 1.7m; the freeboard for

the batteries, transformers and other sensitive equipment will be 300mm in the localised lowest

ground conditions to over 1.7m in the high ground to the east. The minimum height above ground

for all such sensitive equipment will be 300mm.

Given that the terrain undulations are smoothed out by the long arrays, the lowest edges of the

arrays etc will vary.

The transformers, grid equipment and batteries will all be located above 5.01m AOD. These units

are generally containerised and sensitive equipment will be set no less than 300mm above the

design flood level of 5.01m AOD.

As the site will not require the presence of personnel should flooding occur the proposals will not

put people at risk. The proposals will result in very limited development within the area predicted

to flood and will therefore have a negligible effect on flooding in the area.

The units would be within the flood water for the short duration of the tidal event, but the

robustness and sealed nature would ensure the contents are adequately protected against

damage or being moved.


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In their consultation response, NRW has requested consideration of TAN 15 Table A1.15, shown

below. The introduction to A1.15 specifically refers to the concern related to structural damage or

the risk to people, from the flood velocities and depth.

The coastal defences are more than 1m above the highest predicted tide level, so the mechanisms

for water entering the site area are wave overtopping or a breach.

Wave overtopping could not reach the 430m to the site. Overtopped water is also unlikely to

reach the site, and if so it would be shallow and slow rising, well below any of the criteria in the

table below.

A breach in the defences would only occur in a storm, and arising from wave damage. The site is

controlled remotely, and there are no staff routinely on site – they tend to visit every fortnight or

so for safety and maintenance inspections (of the equipment, vegetation, reens etc). Staff will only

visit site if the weather is suitable – this is for normal hearth and safety reasons. Staff would not

visit site in a storm or if a storm was predicted – this is not conducive to safe operations on the

site.

The table relates to events beyond the threshold, ie a breach and/or a 1 in 1000 year event. A

breach is a localised feature and at 430m minimum from the site the water could rush into the

whole area. The water will enter rapidly, but disperse within the whole Wentlooge levels area

spreading out as it enters. By engineering judgment the rise in floodwater during a single localised

tide-cycle breach would not be travelling at 0.3m/s at the site, it would not rise 0.3m in a single

tide cycle and therefore would not reach 1000mm deep at the site. The duration would depend on

the stage of the tide when the breach occurred, but the Seven estuary has a high tide range and

these event s usually occur at the peak, and the duration is limited by the curve of the tide; 2

hours seems a prolonged period.

Coupled with the evident robust defences, the risk of inundation is low.

The panels are supported on robust legs to transfer wind loads to the ground – this load is much

higher than the loads of slow moving water on the slim pressed steel legs on a grid of approx. 6m

by 3.5m.

The 1 in 1000 year event (from Fig 19) would be 6.31m AOD in 2090, and therefore and 5.95m

deep in 2060. The arrays are set at a minimum of 5.01, and therefore the depth criteria for the

arrays and equipment would be less than 1000mm. The author if this report has investigated solar

farms which have been inundated with water and the arrays submerged, but the arrays have

remained operational and no serious harm done. Given that parts of the site are at 5.75m AOD,

and the arrays are supported on 1m high legs, parts of the site and its equipment would be above

the 1 in 1000 year flood event in 2060 and therefore protected from flooding. And it remains that

people would not be ion site is such an event.


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In summary;

• The scenario beyond the threshold would be a localised breach in the defences

• The defences are robust and resistant to tidal forces

• The lifetime of the site is limited to 40 years, less than the design period of the defences.

• A breach would occur during stormy weather

• Staff will not be on site if the forecast or prevailing weather is stormy – it is not conducive

to safe activities on the site.

• The supports are robustly designed to manage high wind loading on the arrays

• The supports are slim pressed steel, and with low resistance to wind and water

• The site is 430m from the nearest potential breach, by which distance the velocities, rise

in water level and total water level would be lower than the criteria in the table during a

single tide cycle.

• The 1 in 1000 year event is likely to damage equipment, but people would not be at the

site

The table below advises that judgment should be applied to site specific circumstances and given the above criteria the proposal satisfies the ‘beyond the threshold’ measures referred to in Table A1.15.

Fug 23 Table A1.15 from TAN 15.


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6. Surface Water Drainage

In terms of the hydrology, the area has been recovered from the sea in ancient times and the

drainage is managed by NRW with sluices etc to retain water in the ditches for irrigation during dry

periods, usually summer, and discharging water in wet periods to control flooding, usually winter.

This management system aids the farmland productivity and vegetation quality, and has created

the habitat and ecology which flourishes in this area. There is no NRW or other Agency plan to

change this arrangement, and the solar farm will not result in a change to this process.

The land in this area is very flat with shallow undulations. Some land is used for grazing, which

results in close cropped grass, and some is ploughed, prepared and used for crops, after which the

land is harvested and the ground left unvegetated until the new crops become established. A wide

range of conditions therefore occur during current normal farming activities at this site.

Rainfall lands on the fields and because it is generally flat with local gentle undulations, tends to

percolate into the soil and be managed locally where it lands by evaporation, evapotranspiration

and infiltration into the soil, moving through the soil to the receiving waters – this is the normal

process in low lying ground. And the successful management of the water levels in the reens has

proved over the centuries that the groundwater level is varied by the water in the reens. In

exceptional wet periods localised ponding occurs in low areas, while the above processes manage

the water. This has also been managed by farmers introducing ‘ridge and furrow’ features, which

will remain in place.

The ridge and furrow features have prevailed during all the times of modern farming, as they can

be seen today. The construction of the solar farm will use low pressure wheel load farm type

machinery, and will undertake construction in suitable weather to enable safe access. This is no

different to the farming activity, and on completion the land will not be traversed by any

machinery, preserving the ridge and furrow more reliably than during farming and particularly

ploughing practices. The consequence of the solar farm will therefore be to preserve the ridge and

furrow for the 40 year lifetime of the solar farm.

The narrow gravel access tracks for the large equipment will generally follow existing farm tracks,

which would have already damaged any ridge and furrow features years ago.

The introduction of solar arrays also make the vegetation more uniform through the year, and

make management flows in the reens more predictable.

The removal of arable farming will cease the application of fertilizers and pesticides, so the water

entering the environment will improve in quality. Arable farming also causes rutting and localised

compaction (tramlines) which results in high levels of soil erosion, adversely affecting the water

quality and capacity of the reens – this problem will cease in the solar farm area. (As researched

by MOPS1, and by Lancaster University).

The site will be seeded to allow a mixture of grasses to flourish, mimicking the existing pasture.

Within the boundary fence, sheep will seasonally graze the site at low density to manage plants

sustainably and avoid plants causing shading over the solar panels. The solar farm area would

therefore be categorised as pasture, providing the same water management characteristics as at


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present on grazing land managed by farming practices, but at lower density and therefore

generating longer vegetation and more virtuous conditions.

Bare areas will be treated, protected and seeded. No specific drainage channels or pathways will

be introduced.

The proposed solar farm will allow the vegetation to flourish, and the fields will not be harvested

and will not therefore be left bare. The consequence of the solar farm will be the following virtues:

• Pasture/meadow will be encouraged.

• Following completion, the area will be restored to create a pasture suitable for grazing,

replicating the existing grazing areas.

• No harvesting will be done and therefore no soil left bare in autumn and winter periods.

• Compaction by intense grazing will cease.

• The soil will improve in quality and character and restore the natural characteristics.

• Pesticides and fertilizers will no longer be added, thus improving the water quality in the

receiving watercourses.

The overall benefit of the solar farm will be a continuation of the virtuous hydrological characteristics provided by the pasture at present, and none of the penalties of arable land with varied rates of runoff, silt and chemicals through the seasons. The site will become an even better haven for wildlife, as has been seen on many completed solar farms in Wales. The flows in reens and main rivers will become more uniform, predictable and manageable and related to the climate patterns and seasons rather than the localised short-term weather and farming (particularly arable) practices. Tracks will be minimised, narrow and formed in permeable granular material which will infiltrate rainfall into the underlying soil and adjacent vegetation. Equipment will be on legs or pads which will be located within a wider area of permeable gravel material. The 350mm thick permeable material will have 30% voids, and therefore capable of containing a rainfall depth 116mm, which exceeds the predicted extreme daily rainfall, even ignoring the infiltration characteristics. This accommodates an allowance for 40% increase due to climate change and is a robust arrangement to manage rainfall, replicating the current characteristics of evaporation and infiltration, and meeting the highest target in the SuDS hierarchy.


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Fig 23 Permeable gravel area within areas of the battery and grid connection areas, to store and infiltrate rainwater. Cable runs will be formed in trenches with protective bedding, and then the excavated material replaced to match the character of the adjacent material. NRW has expressed concerns about rain shadows and bare earth below the arrays. The author of this report has advised on over 100 solar farms across Wales and England, and there is absolutely no evidence of this occurring. On completion and restoration of the soil and seeding, the vegetation establishes quickly across the solar farm, including below the arrays. There is no evidence of bare earth from drips off the panels, and the area becomes a haven for wildlife including insects and birds, which are particularly visible. The monoculture of the former field becomes a biodiverse area. The mechanism is that water drips off the panel edges – from the low edge and the movement features, so is restricted in area. It lands on the soil and provides moisture for the vegetation. Prior to the vegetation establishing, local ponding can occur, but once the vegetation has established, it flourishes and has a slightly different character below the panels, enhancing biodiversity.


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Fig 24 Recently constructed solar farm on 1 in 8 slope showing continuous vegetation across the

farm (Merthyr Tydfil). This was particularly attractive almost immediately to butterflies,

bees and skylarks.

Fig 25 Recently completed solar farm at Avonmouth, Bristol, on low lying land. Note rhyne with

bulrushes and no evidence of nuisance from drips off the arrays.


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Fig 26 Avonmouth solar farm showing continued vegetation under panels. Note these are only

about 450mm off the ground, reducing the light to the underside, but with no lack of

flourishing vegetation. The nature of low-lying land is that the moisture/groundwater

remains level across the site, continuing to feed the vegetation under the panels.

7. Construction

To minimise damage to the soil structure within the solar farm site, deliveries to site will be made

by tracked or low ground pressure machines (i.e. with large tyres), to impose low pressures on the

soil – analogous to farming machinery. A delivery sequence by vehicles will be devised which

minimises repeat journeys over the pasture to reduce rutting and damage to the pasture and soil

structure. This information will be contained within the Construction Management Environmental

Plan (CEMP), which will be approved by the Developer’s representative prior to start on site.

Steps will be taken during construction to protect the watercourses – the proposed distances to watercourses will be protected to prevent access and to provide a natural buffer. Disturbance to the existing soil will be restricted to a minimum, and precautions will be introduced to prevent silt and other contaminants reaching the watercourses using features such as silt fences, geofabrics, straw etc. The routes will be considered carefully to prevent damage the ridge and furrow features, where they exist.

On completion of the works the pasture will be restored using light farming machines and

prepared appropriately for seeding to encourage early growth, restoration of the soil structure

and natural creation of an environment to encourage native pasture plants to flourish.

An inspection and monitoring system will be agreed with NRW to ensure that watercourses are

protected from contamination by silt or other products during and after the works until the

pasture is established. A water quality assessment will be undertaken prior to the construction,

and targets set to enable monitoring and reference during construction – this is the subject of a

separate technical report.


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NRW expressed concern about potential adverse groundwater effects caused by the wind turbine

foundations, related dewatering, etc. The wind turbines have been removed and so the concerns

about adverse groundwater effects are therefore removed.

8. Safe Access

The NRW tables show that there is unlikely to be flooding in the area during the lifetime of the development, given the robust nature of the maintained defences. The mechanism of flooding in the area could arise from overtopping of the defences, or in the

worst case, a breach. The timing and scale of an extreme event will be known, from the following:

• Tide tables.

• MET Office weather forecasts beginning some 5 days before extreme event.

• National Tidal and Sea Level Facility Centre of Excellence for sea level monitoring and surge

prediction.

• News feeds

• Social media

• Natural Resources Wales warnings.

The minimum distance to the coastal defences is over 630m (in the southeast), so there will be significant warning of a potential hazardous condition arising, and the timing of such a hazard will also be predictable – the warnings will be loud and clear through all the news services, and it will not be a surprise. And given the distance of the site from the coast, and the large area of the floodable cell, a failure of the defences will not pose a risk for people on the site, given that for safety reasons their weather check would have advised them the conditions (eg storm) were unsafe for maintenance. Given the small increase in sea level rise of about 280mm in the 40 year lifetime of the development, the site remains at very low risk of flooding – the risk should not change significantly during the lifetime of the development. The existing roads are generally raised about 600mm above the neighbouring fields. The roads will therefore be last to suffer flooding, allowing safe access to be judged on arrival, if flooding has occurred from a previous event. Moreover, the solar farm is controlled remotely and attendance at the site in adverse weather conditions is not conducive to safe maintenance activities etc. So if the weather is inclement, or a warning of flooding is issued, the solar farm will not be visited. It is recommended that the operator is registered with the NRW flood warning service and that if a warning is issued, all visits are cancelled until the risk and/or hazard have passed. Return to site should not be attempted until the roads are declared clear and safe, and the senior management for the Operator has declared the site safe.


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9. Management and Maintenance

The solar farm will be managed by the operator of the solar farm. It is controlled remotely, so the farm will be visited routinely when conditions are appropriate for the inspection and maintenance activity to be undertaken. Insofar as this report is concerned, it is important that the drainage is effectively monitored and that the drainage works effectively, to avoid causing increased nuisance on and off site. This will take the form of the following:

• Annual formal inspections of the ditches/reens which fall into the Riparian Ownership of the

solar farm operator, when the vegetation has died back, in autumn.

• If blockages are encountered, these should be removed.

• Tree growth or animal activity which could adversely affect conveyance of flow or storage

should be rectified and the former channel section restored.

• Vegetation should be inspected, to ensure that it is flourishing. Bare earth areas should be

treated and vegetation re-established.

• Tracks should be inspected to ensure they remain permeable; the cause of ponding should be

investigated and rectified.

• New channelling or streaming is unlikely to be a problem on such a flat site, given that solar

farms at 1 in 8 slopes in Wales are preforming well with no sign of streaming.

• Inspect the Battery Store area and if ponding occurs on the permeable surfaces, inspect and

rectify the problem.

• Arrange for 24 hour access to NRW and its nominated representatives for maintenance of the

reens and sluices.

The above annual monitoring, supplemented by a watchful eye during routine site visits, should ensure that the solar farm functions properly and drainage behaviour mimics the characteristics of existing pasture, enabling easier and more manageable control of the reens. 10. Policy

Flood Policy relates to the protection of people and property. The Welsh Assembly Government’s

Planning Policy Wales and its Technical Advice Note 15 (TAN 15) give guidance on flood risk and

steers development away from areas at risk of flooding.

The site is shown to be in defended Flood Zone 3 and Flood Zone 3, but this site specific FCA

shows that the whole site is in a defended area, confirmed by its status as being in C1 according to

NRW. C1 is defined by NRW as ‘areas of floodplain which are developed and served by significant

infrastructure, including flood defences’.

Figure 1 of TAN 15 confirms that development can take place subject to the application of the

justification test including acceptability of consequences. This FCA shows that that the

consequences are acceptable. The justification test is described elsewhere.


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The site will be routinely inspected to monitor the farm and undertake essential maintenance,

usually every fortnight or so. People will not visit the site during intense storms or floods because

the weather and conditions would not be conducive to safe activities and servicing.

The solar panel equipment is resilient to wet weather, and is designed to operate in all predicted

weathers, subject to normal maintenance. The material from which the panels, supporting

structure, cabling and transformers is all durable and will not cause any level of pollution in the

ground. The fences and solar farm infrastructure will be set back from watercourses, except where

they need to cross for security reasons.

The cessation of arable farming, which results in bare earth in the autumn and high levels of runoff

– potentially with silt – will be eliminated by the proposed pasture.

The removal of intense grazing and compaction of the soil by animals and farming machinery will

be significantly reduced, resulting in improved soil conditions adding to the overall betterment of

hydrological performance. The flourishing grassland will also prevent silt runoff, and the

elimination of fertilizers and pesticides will improve water quality entering the environment.

The proposal is in harmony with the objectives of the Newport Local Biodiversity Action Plan,

which on page 14 describes in its vision statement; ‘The overall vision of this plan is to maintain,

extend and improve the conditions of wetland habitats within Newport and the BAP species

associated with them.’ This proposal contributes significantly to delivering the objectives of this

plan on the solar farm site, and downstream.

The beyond threshold conditions have been considered in terms of the site-specific characteristics,

and it has been shown that the criteria in TAN 15 A1.15 will be satisfied.

The proposed renewable energy hub therefore brings significant betterment in terms of

management of runoff bringing the virtuous characteristics of pasture to the solar farm area and is

therefore in accordance with the guidance given and the objectives of TAN 15.

11. Conclusions & Recommendations

The change in use of these fields from arable and pasture to solar farm delivers the following:

• An important and significant source of renewable energy for the community.

• The site is in Flood Zone C1, safely served by significant flood defence infrastructures.

• The flood defences are modern and robust and above their target condition.

• The lifespan of the solar farm is 40 years (ie to 2060), within which time sea level rise is not

predicted to be significant.

• The Design Flood Level (1 in 200 year level in 2060) determined from the NRW data is 5.01m

AOD in 2060

• The 1 in 200 year flood in 2060 (Design Flood) will not cause any flooding of the panels which

are set at 5.01m AOD minimum, which is also recommended for the bases of transformers,

battery units, etc.


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• A 300mm freeboard is recommended for the level of sensitive equipment within transformer

units, battery containers, etc.

• The proposals will not impede flood flows or increase flood risk elsewhere.

• There is no risk to visitors from flooding or excessive surface water flows.

• The equipment and associated infrastructure is robust, resilient to wet weather and will not

cause pollution.

• Some existing fields are arable and cause high levels of runoff carrying silt in storms after

ploughing, which will be eliminated by the proposed use.

• The elimination of intense grazing will allow the soil to improve and manage rainwater better.

• The water quality entering the environment will improve through eliminating the application

of pesticides and fertilizers.

• The removal of pesticides encourages the site to become a haven for bees and other insects.

• The creation of pasture will perpetuate the virtuous conditions for soil quality, infiltration and

evapotranspiration.

• The resulting ecology will be a haven for a range of invertebrates, reptiles, amphibians, small

mammals and birds.

• The improvement in the soil structure through the changed ecology will therefore be

beneficial to the hydrology.

• The virtues described above are in harmony with the Newport City Council Local Biodiversity

Action Plan, through improving the wetland habitats end encouraging species to thrive.

• The flat land prevents channelling and streaming from developing, and so intense overland

surface flows will not occur.

• Tracks will be permeable and tend to grass over, adding to biodiversity.

• Construction will use farm type machinery, thus not causing damage to ridge and furrow

features, and thereafter the ridge and furrow features will be preserved for the lifetime of the

development.

• Permeable areas below and around cabinets will provide greater storage than the existing

soil, will aid evaporation and infiltration, and allow evapotranspiration by the adjacent

vegetation.

• A maintenance regime is described which will maintain the virtues of the proposed design.

• The heavy machinery associated with farming will be eliminated, and only light vans will be

used after completion, thus preventing further compaction of the soil.

• Watercourses will be monitored before and during construction to manage the potential risk

of silt pollution and keep it within acceptable limits.

• A CEMP will be required from the Contractor and will be approved prior to commencement,

to ensure the construction is undertaken safely with regard to the environment.

The site will therefore be safe for people and property, and in conclusion the proposed change of

use will provide a positive contribution to soil characteristics, water characteristics and

biodiversity, and allow a more manageable approach to the control of the reens through the

seasons bringing significant overall benefits to the environment. The proposal complies with the

guidance given in TAN 15 and the Local Biodiversity Action Plan.

gwent farmers renewable solar scheme ltd...• safe design level in 2060 (1 in 200 year defended...

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