The information presented in this appendix has been taken from version 3 of a document titled "Structural Stormwater Quality BMP Cost / Size Relationship Information from the Literature" (Taylor, 2005b). Check the toolkit web site (www.toolkit.net.au) to ensure that this is the latest version available.
This appendix summarizes cost-related information for structural stormwater quality best management practices (BMPs) that was found in the literature.
This information has been summarized to provide guidance to urban stormwater managers who are seeking additional costing information to that provided in MUSIC’s life cycle costing module. For example, a music user may wish to estimate the total acquisition cost of a very large plastic rainwater tank (e.g. 30 kL). As the size / cost algorithm for this cost element in MUSIC’s life cycle cost module has been derived from a data set involving metal tanks that are 1 to 15 kL in size, the user is likely to use estimates from this appendix in preference to MUSIC’s default value.
Basic BMP cost / size relationships from the literature should be used with caution. The CRC for Catchment Hydrology’s work involving BMP costing has found a very high degree of variability in most cost elements. Despite this variability, very few cost-related studies report the degree of uncertainty associated with their cost estimates.
The dollar values quoted in this report have not been adjusted for inflation. For example, if the referenced source of a cost estimate is "CRC (2002)", the dollar values are in 2002 Australian dollars. At time of writing, 2% is a suggested annual inflation rate that is relevant to these types of assets.
An in-ground GPT supplier undertook a survey of its units in NSW from October 1997 to September 2000. The study looked at 334 maintenance events involving the removal of 1,345 tonnes of gross pollutants (in total). This survey found that typical annual maintenance costs ranged from $0.13/kg (in 2001 dollars) for larger units to $0.28/kg for smaller units. This range equates to approximately $0.17/ha/day to $0.78/ha/day.
The NSW EPA (2002) developed a spreadsheet that lists approximate unit prices (i.e. capital costs) for a wide range of proprietary GPTs. This spreadsheet also provides some information on typical maintenance costs associated with these units. A summary of these costs is provided below:
WBM Oceanics has undertaken a review of the capital costs, operating costs and performance of a range of proprietary stormwater treatment measures for the NSW Stormwater Trust. This material is yet to be published, but maintenance costs associated with the collection and disposal of wastes collected by various gross pollutant traps are reported within a broad range of $160 to $700 per cubic metre of waste (S. Barter, pers. comm., 2004).
In addition to this cost range, WBM have estimated a $/yr figure for typical BMP inspection costs (i.e. ~$120 - 720/yr) and an annual administration fee ($10 - 100/yr). Note these cost estimates are based on unit rates and predictions of expended time, not real expenditure.
The WBM estimates are based on summarised costing data from NSW Councils in the late 1990s and also estimates of what maintenance should be done and what it should cost (based on unit rates). It makes no allowance for the time value of money, whether GST is (or isn't) included, and does not consider parts of the life cycle (e.g. defining the need for the BMP, renewal / adaptation costs, decommissioning).
Hornsby Shire Council (2002) produced a "Catchment Remediation Capital Works Program: Annual Performance Report 2001-02" which includes some costing information for 2001-02:
Based on a limited data set from Brisbane, Weber (2001 and 2002) reported the following cost estimates:
Walsh (2001) reported that the typical capital cost in Melbourne for vortex type in-ground GPTs that are operated by local government authorities was $100,000 per m3/sec (when the flow is at its peak treatment rate).
A ‘rule of thumb’ for BMP costing in Penrith / Blacktown (based on 10 years experience): Big GPTs ≈ $10,000 p.a. for typical maintenance (Hunter, 2003).
Information from Frankston City Council (Victoria):
A study by the NSW Department of Public Works and Services (2001) assumed typical annual maintenance costs for GPTs (e.g. CDS, Ecosol, Rocla, etc.) as being ~ 7% of capital cost (the rationale for this figure is not explained in the report). The study also estimated typical annual maintenance costs for nine types of GPTs (probably based on the ‘7% relationship’):
Lloyd et al. (2002) developed some BMP size/ cost relationships for "litter and sediment traps" (combined):
Leinster (2004) reported the following construction costs associated with wetlands in greenfield developments within South East Queensland:
Small-scale wetland with an inlet pond, macrophyte zone, bypass weir and channel:
Larger-scale wetland to treat recirculated lake water:
The Centre for Watershed Protection (CWP, 1998), Weber (2001) and US EPA (2001) reported annual maintenance cost ≈ 2% of construction cost.
A ‘rule of thumb’ for wetland costing in Penrith / Blacktown (based on 10 years experience): ~$500,000 per ha of surface area for design and construction cost, ~$10,000 per ha (p.a.) for routine maintenance in the first 2 years (i.e. ~2% of design and construction cost, or ~1.96% of total acquisition cost) then ~$5,000 per ha p.a. for routine maintenance (i.e. ~1% of design and construction cost, or ~0.98% of total acquisition cost), then major corrective maintenance very 10 years (~5% of construction cost). (Primary source: Geoff Hunter, 2003.)
Weber (2002) reported typical construction cost ≈ $500,000 each or ~$3,400 - $17,900/ha (of area treated) or ~$730,000/ha (of wetland area). Also, typical annual maintenance cost ≈ $8,200. This is information from Brisbane, based upon a very limited data set.
Walsh (2001) reported typical construction cost for greenfield wetlands in Melbourne ≈ $120,000/ha of area treated.
Fletcher et al. (2005) suggested that the macrophyte zone needs to be replaced every 20-50 years at a cost of ~50% of the initial construction cost.
Melbourne Water (2003a) has a basic construction cost estimation model for large greenfield wetlands in Melbourne. It allows for typical site characteristics to be used as factors that determine overall construction cost. The cost relationships appear to be based on a limited data set (i.e. tender information for ~8 BMPs).
Lloyd et al. (2002) developed some BMP size / cost relationships for "wetlands and vegetated swales" (combined):
A unit cost of $75/m2 (of wetland area) was used for the construction of a wetland with a 1 ha catchment during a desk-top water sensitive urban design project in the Snowy Monaro region (Lane, 2004). This rate did not include any costs associated with an up-stream gross pollutant trap which was included in the design (i.e. $11,000 for the design and construction cost of a CDS unit), or construction work on the outlet of the wetland (estimated at $5,000).
Earthtech Engineering Pty Ltd (2003) in Melbourne used an estimate of ~$46-48 per linear metre for construction costs.
The Centre for Watershed Protection (CWP, 1998) and US EPA (2001) reported typical annual maintenance cost ≈ 5-20% of construction cost.
Fletcher et al. (2005) suggested that the construction cost of an infiltration trench is ~$60-80/m3 of trench (assuming the trench is 1 m wide and 1 m deep).
URS (2003) estimated the unit rate for the construction of a 1m wide, 1m deep infiltration trench in Sydney as $138/m. This cost estimate included: excavation, installation of geofabric liner, installation of perforated pipe, installation of gravel layer, installation of filter layer, application of top-soil, application of grass seed, application of fertiliser and watering.
Costing information from Boral (2003) in NSW for five types of design:
Fletcher et al. (2005) reported that the typical annual maintenance costs of permeable paving in California (when converted from US dollars) were approximately $9,700/ha.
URS (2003) estimated the cost of supplying permeable pavement blocks to be approximately $30 to $50/m2 in Sydney. The total construction cost was estimated to be $98.4/m2, which includes excavation and profiling, supply of blocks, installation of blocks, installation of geofabric liners, installation of gravel and installation of sand.
Boubli and Kassim (2003) reported costs associated with the Pioneer Street project in Sydney for ‘permeable pavers’ as being approximately $120/m2 of paving. This estimate includes costs associated with supplying and placing the pavers.
Walsh (2001) reported:
URS (2003) reported that the construction cost of a typical grass buffer strip would be approximately $10 to $15/m2 in the Sydney area (includes surface preparation, top-soiling and seeding with grasses). This cost estimate increases to approximately $20 to $50/m2 if native grasses and shrubs are used as vegetation.
Lloyd et al. (2002) suggested grassed swales cost ~$2.50/m2/yr to maintain (but if residents do regular mowing there is less cost to local authorities). For vegetated swales the routine maintenance cost starts at ~$9/m2/yr, then after ~5 years decreases to ~1.50/m2/yr.
Fletcher et al. (2005) suggested the typical construction cost of grassed swales and buffer strips (based on advice from contractors) is ~4.50/m2 which includes earthworks, labour and hydro-mulching. If rolled turf is used the cost is ~$9.50/m2. The cost of a vegetated swale system using labour, earthworks and indigenous vegetation is between ~$15 to 20/m2 (based on information from Indigenous Gardens Pty Ltd in Melbourne).
Bryant (2003) reported that it cost ~$120/m2 for planting (excluding trees), excavation, soil, swale cross-overs, initial maintenance and irrigation of swales.
Leinster (2004) reported the construction cost associated with ‘swale bioretention systems’ in greenfield developments within South East Queensland as approximately $100 - 120/linear metre including vegetation. For this system the filter zone / swale base has a width of 1 m and a swale top has a width of 3-4 m.
Lloyd et al. (2002) developed some BMP size / cost relationships for "wetlands and vegetated swales" (combined):
URS (2003) estimated unit rate construction costs for vegetated swales:
Beecham (2002) estimated vegetated swale maintenance costs for Sydney conditions as $3.13/m2, based on the following unit rates: $1.62/100m2 for mowing (required 2 - 3 times a year), $16.20/100m2 for general grass care, $0.95/m2 for litter removal, $0.65/m2 for reseeding and fertilisation (1% of the total area is revegetated per year), and $1.35/m2 for annual inspections and administration.
A unit cost of $100 per linear metre was used for the construction of a road-side grassed swale during a desk-top water sensitive urban design project in the Snowy Monaro region (Lane, 2004). Roadside swales are typically 3m wide.
Leinster (2004) reported the following construction costs associated with bioretention systems in greenfield developments within South East Queensland:
The Centre for Watershed Protection (CWP, 1998) and US EPA (2001) reported the typical annual maintenance cost ≈ 5-7% of the construction cost.
Fletcher et al. (2005) suggested that a grassed bioretention system forming part of a residential nature strip costs ~$135 per linear metre to construct (based on costings from the Lynbrook Estate in SE Melbourne). The suggested maintenance cost for mature systems is reportedly similar to that of swales ~$2.50/m2 for grassed systems and ~$1.50/m2 for vegetated systems using native vegetation.
URS (2003) estimated unit rates for the construction of 3m wide, 1m deep bioretention trenches as $410/m or $137/m2 of surface area. This estimate included: excavation and installation of geofabric liner, drainage pipe, drainage layer, filter media, sand, top-soil and vegetation.
A unit cost of $350 per linear metre was used for the construction of a road-side bioretention system during a desk-top water sensitive urban design project in the Snowy Monaro region (Lane, 2004).
Boubli and Kassim (2003) reported quotes supplied by three tenderers for the Heritage Mews project in Sydney for ‘biofiltration trenches’ as being approximately $150/m3 of trench. This estimate excludes costs associated with plants and landscaping.
The Centre for Watershed Protection (CWP, 1998) and US EPA (2001) reported in Taylor and Wong (2002): Annual maintenance cost ≈ 11-13% of construction cost.
WBM (2003) estimated costs for supply and installation as $5,000 to $50,000 (cited in URS, 2003). Maintenance costs were estimated to range from $1,000 to $5,000 p.a. depending on the scale of the device.
Gibbs (2003) reported that a sand filter and storage basin in Sydney with a catchment area of 60,000m2, a sand filter size of 32m2, and a ‘storage plus filter area’ of 150m2 cost $167,815 to construct (i.e. $1,500 per m2 of sand filter including storage capacity).
Newcastle City Council (2002) reported that the construction cost (in 2001 Australian dollars) for a sand filter that treated a catchment approximately 5,000m2 in size was $28,004 (or $36,153 including site establishment, survey, design and supervision costs).
Weber (2001 and 2002) reported in Taylor and Wong (2002): Typical annual maintenance cost ≈ 6% of construction cost. Also, typical construction cost ≈ $50,000 and typical annual maintenance cost ≈ $2,800.
The Centre for Watershed Protection (CWP, 1998) and US EPA (2001) reported typical annual maintenance cost ≈ 3-6% of construction cost.
Fletcher et al. (2005) suggested that a rough estimate for pond construction cost (based only on 1 case study) is ~$2,000/ha of catchment.
Weber (2002) reported typical construction cost ≈ $30,000/ML of pond volume (based on limited data).
Walsh (2001) reported typical construction cost ≈ $60,000/ha of pond area.
Kuczera and Coombes (2001) reported that the typical annual maintenance cost ≈ $70 for above ground tanks.
Gardner et al. (2003) reported that operation and maintenance costs for a 22 kL tank on the Gold Coast, where water was used for toilet flushing and garden watering, were $101.43/year (i.e. $66.43 for electricity and $35 for maintenance). Water savings from the use of the tank (for a detached residential development) was 124 kL/year or $136.40/year in avoided costs (or mains water). The purchase and installation cost was $2,600 (this includes a 1 kw pump and plumbing costs).
An estimate of rainwater tank pump electricity use is 3,000 kwh/ML (T. Gardner, pers. comm., 2004). This equates to a cost of approximately $410.40/ML (using the electricity cost provided by Grant and Hallmann, 2003).
Cardno BLH (2002) reported additional costs associated with above ground steel tanks from 2 NSW case studies (i.e. the Heritage Mews and Pioneer Street Projects):
In addition, URS (2003) estimated the on-going cost of running an electric pump associated with water tanks that are plumbed into a house (e.g. for toilet flushing) would be $150 p.a. It is assumed that this estimate includes pump maintenance as well as electricity.
Boubli and Kassim (2003) reported the following plumbing costs associated with aboveground tanks for a development in Sydney's north-west:
The Institute for Sustainable Futures (2002) reported estimated costs for additional plumbing that would be required to supply treated stormwater for toilet flushing at the Kogarah Town Square Redevelopment Project as $350 per apartment.
Lane (2004) estimated the cost of retrofitting rainwater tanks to existing residential properties using three case studies in Snowy Monaro region. The conclusion of this work was that a total of $3,000 to $4,000 would be adequate to fully retrofit a 9 kL above ground rainwater tank. This cost included purchase and supply of the tank (the average cost was approximately $1,288), the purchase of the pump (the average cost was approximately $577), plumbing materials (the average cost was approximately $1,010), the plumbing labour (varied greatly from $580 to $3,807) and the cost of the electrician (the average cost was approximately $187).
Coombes (2002) estimated typical rainwater tank supply costs: Aquaplate = $540 (4.5 kL) and $860 (9 kL); Galvanised iron $440 (4.5 kL) and $640 (9 kL); Polymer $670 (4.5 kL) and $1,150 (9 kL); and Concrete $1,300 (4.5 kL) and $1,800 (9 kL). Note that up-to-date purchase prices for tanks are readily available from suppliers, many of whom have web sites. The typical installation cost for 5-10 kL tanks was estimated by Coombes (2002) to be $1,600 (estimate includes pump, pressure controller, stand, fittings including float system and installation).
SIA (2004) reported cost estimates associated with Aquaplate above ground tanks, shown in Table 1:
| Item | Approximate cost for each tank size (in $2001) | ||
|---|---|---|---|
| 5kL | 10kL | 15kL | |
| Aquaplate rainwater tank | 540 | 870 | 1200 |
| Pump + pressure controller | 200 + 160 | 200 + 160 | 200 + 160 |
| Plumber and fittings | 500 | 500 | 500 |
| Float system | 100 | 100 | 100 |
| Concrete base | 200 | 200 | 200 |
| GST (10%) | 170 | 200 | 240 |
| Total (incl. GST) | $1,910 | $2,230 | $2,600 |
| Tank size | Tank type | Tank shape | Approximate tank supply cost |
|---|---|---|---|
| 1.5kL | Galvanised steel, aboveground | Round Rectangular / ovular | $2,470 $2,870 |
| Colorbond finish with a polymer type liner, aboveground | Round Rectangular / ovular | $2,570 $2,970 | |
| 3kL | Galvanised steel, aboveground | Round Rectangular / ovular | $2,970 $3,470 |
| Colorbond finish with a polymer type liner, aboveground | Round Rectangular / ovular | $3,320 $3,820 | |
| 5kL | Galvanised steel, aboveground | Round Rectangular / ovular | $3,170 $4,280 |
| Colorbond finish with a polymer type liner, aboveground | Round Rectangular / ovular | $3,620 $4,600 | |
| 9kL | Galvanised steel, aboveground | Round | $3670 |
| Colorbond finish with a polymer type liner, aboveground | Round | $4,120 | |
| 5kL | Below ground (Rocla Eco Rain) | - | $7,800 (plus $800 for reticulation to toilets) |
| 10kL | Below ground (Rocla Eco Rain) | - | $11,050 (plus $1,050 for reticulation to toilets) |
| Tank size (L) | Tank type | Approximate tank supply cost ($) |
|---|---|---|
509 | Slim line (aboveground) | $491 |
700 | Tall round (aboveground) | $418 |
720 | Slim (aboveground) | $501 |
758 | Round (aboveground) | $511 |
1,074 | Slim (aboveground) | $766 |
1,179 | Round (aboveground) | $521 |
1,250 | Round (aboveground) | $550 |
1,400 | Tall slim (aboveground) | $792 |
1,615 | Round (aboveground) | $551 |
1,800 | Under house (aboveground) | $1,122 |
2,100 | Tall slim (aboveground) | $1,144 |
2,281 | Slim (aboveground) | $1,271 |
2,499 | Squat (aboveground) | $601 |
2,500 | Round (aboveground) | $682 |
2,500 | Twin under-deck (aboveground) | $1,122 |
2,542 | Tall (aboveground) | $601 |
2,800 | Tall slim (aboveground) | $1,496 |
3,600 | Twin rectangular under house (aboveground) | $2,244 |
4,125 | Squat (aboveground) | $901 |
4,885 | Medium round (aboveground) | $901 |
5,000 | Round (aboveground) | $968 |
9,000 | RT poly tank (aboveground) | $1,595 |
9,609 | Large squat (aboveground) | $1,850 |
10,478 | Large tall (aboveground) | $1,500 |
10,500 | RT poly tank (aboveground) | $1,705 |
13,500 | RT poly tank (aboveground) | $2,024 |
15,064 | Large (aboveground) | $1,850 |
22,500 | Low profile (aboveground) | $2,376 |
22,500 | RT poly tank (aboveground) | $2,640 |
24,180 | Large tall (aboveground) | $2,551 |
25,090 | Large low profile (aboveground) | $2,551 |
29,560 | Very large (aboveground) | $2,950 |
38,334 | Very large (aboveground) | $4,170 |
| 47,950 | Monster (aboveground) | $5,152 |
Grant and Hallmann (2003) estimated the costs associated with a 2,250 litre plastic tank with a life span of 30 years as: $510 purchase; $38.50 (delivery); $270 (for plumbing costs that allow toilet flushing and garden watering to use tank water); $350 (for the pump); $100 (electrician costs). They also assumed the pump would last for 15 years, and the cost of running the pump (in Melbourne) was estimated to be $0.1368/kwh.