Appendix C: Delivery guidance and costing
This Appendix provides further detail to understand how some of the ‘tools’ in the GBI toolbox could be delivered in Carmarthenshire. It provides indicative costings for a number of components that might form part of each tool.
It is important to recognise that the indicative costs provided here are high level in nature. They are generally presented as a “low to high” range and are intended to be used only as a guide.
Costs have been identified using recognised industry rates and pricing resources (including Spon’s External Works and Landscape Price Book and the John Nix Pocketbook), or have been developed using case study examples of similar works, or provisional sum allowances.
They focus on capital and maintenance costs and no allowance has been made for professional fees or land purchase costs.
Individual projects would need to be subject to more in-depth feasibility studies to inform any potential future funding bids.
Likely rises in inflation over the life of this GBI Strategy should also be taken into account when costing individual projects.
Tool 1: Depave and create Rain Gardens
Costs for these features will depend to a significant degree on scale.
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Rain gardens (small scale suds feature) – provisional sum. | m2 | £100 – £150 | £5 – £7 | None. |
| Creation of wetland areas (e.g. constructed wetland, wet grasslands, marshes, reedbed). | ha | £10,000 – £17,000
£300,000 high level indication of approx. cost for a SuDS wetland serving an area of 10 Ha. |
£150 – £600 | From new and for the first 2-3 years, maintenance will be more frequent to aid development of the asset. Maintenance costs will become relatively low once the wetland has established but will still require regular checks on hydraulic controls/inlets/outlets to ensure blockages are minimised and operation adequate. Occasional 10 – 20 (or more years) sediment/siltation control will be required if catchment causes this. Natural catchment will need this less frequently. Any significant management de-silting/striping of plants/reeds should only be across one third of the asset in any one year. |
Tool 2: Restore River Corridors and Wetlands
Costs for these features will depend on scale.
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Daylighting of watercourses (e.g. within settlements). | linear m | £500 – £1,500 | – | In an urban setting this could be very expensive to overcome urban infrastructure and utilities. This will be less of a concern in more open settings. |
| Flood storage (detention basin £ /m3 stored volume). | m3 | £30 – £80 (per m3)
£350,000 high level indication of approx. cost for a storage pond serving an area of 10 Ha for a low-medium storm return period. £200,000 high level indication of approx. cost for a basin serving an area of 10 Ha for a low-medium storm return period. |
– | Critical to the success of flood storage areas is ensuring that hydraulic structures inlets/outlets/controls are functioning as designed and blockages are minimised. This will require frequent inspections, perhaps monthly and before and after any large storms.
|
| Creation of wetland areas (e.g. constructed wetland, wet grasslands, marshes, reedbed). | ha | £10,000 – £17,000
£300,000 high level indication of approx. cost for a SuDS wetland serving an area of 10 Ha. |
£150 – £600 | From new and for the first 2-3 years, maintenance will be more frequent to aid development of the asset. Maintenance costs will become relatively low once the wetland has established but will still require regular checks on hydraulic controls/inlets/outlets to ensure blockages are minimised and operation adequate. Occasional 10 – 20 (or more years) sediment/siltation control will be required if catchment causes this. Natural catchment will need this less frequently. Any significant management de-silting/striping of plants/reeds should only be across one third of the asset in any one year. |
| Re-surface cycle route (e.g. canal side / green corridor). | km | £150,000 – £200,000 | Whole life replacement cost: assume 10-15% capital cost per annum. | Maintenance – Fairly limited for many years, assuming no erosion from the river. |
| Informal mixed-use path (self-binding gravel – 1.2m wide). | lin m | £75 – £150 | Whole life replacement cost: assume 10-15% capital cost per annum. | Fairly limited maintenance for many years, assuming no erosion from the river. |
| Boardwalks. | m2 | £250 – £400 | Whole life replacement cost: assume 10-15% capital cost per annum. | Maintenance required – Inspections to ensure structure is robust enough for purpose. This includes posts and surface/decking. Replacement when necessary, probably at least 10 years if wooden parts are originally treated. |
| Benches / site furniture. | Item | £750 – £1,000 | Whole life replacement cost: assume 10-15% capital cost per annum. | Minimal maintenance – except for monitoring of vandalism and weathering. |
| Recreation impact study. | Item | £60,000 – £100, 000 | – | None. |
Tool 3: Protect and Connect Coastal Places
Individual large-scale coastal restoration projects would need to be costed on a site-by-site basis. However the below gives an indication of assets which would improve accessibility of coastal areas to supplement these schemes.
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Benches / site furniture. | Item | £750 – £1,000 | Whole life replacement cost: assume 10-15% capital cost per annum. | Minimal maintenance – except for monitoring of vandalism and weathering. |
| Informal mixed-use path (self-binding gravel – 1.2m wide). | lin m | £75 – £150 | Whole life replacement cost: assume 10-15% capital cost per annum. | Fairly limited maintenance for many years, assuming no erosion from the sea. |
| Recreation impact study. | Item | £60,000 – £100, 000 | – | None. |
Tool 4: Green the Places where People Live, Work and Visit
Costs will vary significantly depending on the nature of the features.
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Footpath creation (Informal mixed-use path (self-binding gravel – 1.2m wide). | Lin m | £75 – £150 | Whole life replacement cost: assume 10-15% capital cost per annum. | Maintenance – Fairly limited for many years, assuming no erosion.
|
| Urban street tree planting. | Item | £100 – £1,000 (in soft landscaped areas)
£1,900 – £3,900 (trafficked areas) |
Assume £15 – £30 | Maintenance for monitoring of vandalism, unsafe branches, management of tree size and path/road root impact |
| Pocket Park i.e. less than 0.2 ha (seating, planting, surfacing, boundaries). | m2 | £350-500 | £15 – £20 | None. |
| Linear park (access routes, habitat areas, entrance treatments). | ha | £1 million – £2.5 million | £2,000 – £10,000 | None. |
| Green walls. | m2 | £500 – £750 | £80 – £200 | None. |
| Biodiverse roof (excluding any structural work). | m2 | £130 – £140 | Assume £3,000 – £5,000 annual average / roof | None. |
| Planters (timber street planters 1m high – ornamental planting). | m2 | £250 – £500 | £10 – £50. | None. |
Tool 5: Interpret, Educate and Tell Stories about the Environment
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Interpretation trail (interpretation boards along a defined route, manufacture, installation). | km | £15,000 – £20,000
(depending on size and vandal proofing) |
Whole life replacement cost: assume 10-15% capital cost per annum. | Minimal maintenance – except for monitoring of vandalism and weathering. |
| Directional signage. | Item | £150 – £750 | Whole life replacement cost: assume 10-15% capital cost per annum. | Minimal maintenance – except for monitoring of vandalism and weathering. |
Tool 6: Expand and Enhance Tree Cover
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Woodland creation. | ha | £4,000 – £9,000 | £500 – £3,500 | None. |
| Hedgerow planting. | lin m | £20 – £35 | £8 – £20 | None. |
| Ranger grade staff / support staff – provisional sum. | FTE | £35,000 + | – | None. |
| Site finding study for suitable woodland creation sites. | Item | £20,000 – £40,000 | – | None. |
Tool 7: Provide Green Routes to Walk and Cycle
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Mixed strategic cycle route (mixture of on/off road, segregated and non-segregated sections). | km | £500,000 – £1.3million | Whole life replacement cost: assume 10-15% capital cost per annum. | Maintenance – Fairly limited for many years, assuming no erosion.
|
| Cycle parking facilities. | Item | £10,000 – £12,000 (for small under over facility)
|
Whole life replacement cost: assume 10-15% capital cost per annum. | Minimal maintenance – except for monitoring of vandalism and weathering. |
| Footpath creation (Informal mixed-use path (self-binding gravel – 1.2m wide). | Lin m | £75 – £150 | Whole life replacement cost: assume 10-15% capital cost per annum. | Maintenance – Fairly limited for many years, assuming no erosion.
|
| Directional signage. | Item | £150 – £750 | Whole life replacement cost: assume 10-15% capital cost per annum. | Minimal maintenance – except for monitoring of vandalism and weathering. |
Tool 8: Create a Green Setting for Heritage Assets
N/A (see other tools for indications of cost for components which contribute to this tool).
Tool 9: Rethink the Functions of Park and Grass Areas
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Wildflower verges. | m2 | £2 – £5 | £600 – £800 (£/ha) | NB this may represent a cost saving when compared to /hectare costs for conventional mowing regimes for these spaces. |
| Creation of species rich grassland / meadow. | ha | £2,000 – £7,000 | £600 – £800 | Costs associated with limited mowing regime. |
| Interpretation board. | Item | £2,500 | Whole life replacement cost: assume 10-15% capital cost per annum | Minimal maintenance costs – except for monitoring of vandalism and weathering.
|
Tool 10: Find Space for Community Growing
N/A (costs not available and would vary significantly depending on the location and nature of growing space)
Tool 11: Create Playful Spaces
As noted in the description of this tool, playful spaces vary significantly in scale, nature and design. However the below provides a very indicative costing for delivering a small-scale play space.
| GBI asset or component | Unit | Indicative cost range | Annual maintenance costs once established | Comments |
| Small play area. | Item | £50,000+ | Whole life replacement cost: assume 10-15% capital cost per annum | None. |