This section provides guidance on undertaking life cycle costing analyses for ‘generic’ GPTs (i.e. when the type has not yet been determined), in-ground GPTs (e.g. the common types of proprietary devices that are available in Australia), open GPTs (i.e. a sediment basin with a trash rack), trash rack GPTs, release net GPTs and side entry pit trap (SEPT) GPTs.  For descriptions of these types of GPT, refer to the document titled ‘Urban Stormwater: Best Practice Environmental Management Guidelines’ (Victorian Stormwater Committee, 1999).

The process for undertaking a life cycle costing analysis for gross pollutant traps is the same as described in Life-Cycle Costing - Constructed Wetlands and Life-Cycle Costing - Bioretention Systems. The only significant differences are:

The desired volume of the GPT (VU) is calculated automatically and provided as the 'Suggested Volume (m3)'.  You can click the button to access the parameters of the calculation as shown below and make any changes.  These will be then reflected back in the suggested volume.

Each of these parameters are outlined below in the process to undertake a manual calculation of VU, if required.

To manually estimate the desired volume of the GPT (VU), undertake the following steps:

The origin of all of the ‘expected’ values and algorithms in MUSIC’s costing module, as well as the statistical operations used to generate ‘upper’ and ‘lower’ estimates for GPTs are explained in Table 1 (generic designs), Table 2 (open GPTs), Table 3 (in-ground GPTs), Table 4 (trash racks and litter baskets), Table 5 (release nets) and Table 6 (side entry pit traps).

Table 1. Summary of cost-related relationships for ‘generic’ GPTs.


Element of Life Cycle Costing Model

Default Option for Estimation in music

Alternative(s)

Notes

Life cycle

63 years.

n = 2

No alternative in music.

Upper and lower estimates derived using a 84th and 16th percentile, respectively.

Total acquisition cost (TAC)

TAC ($2004) = 22460 x (VU)0.4702

R2 = 0.59; p < 0.01; n = 72.

Where: VU = total volume of all stormwater and trapped pollutants in the unit when it is operating at its peak design flow (m3).

TAC ($2004) = 31430 x (C)0.3971

R2 = 0.34; p < 0.01; n = 121.

Where: C = area of the GPT’s catchment in ha.

For literature values, see Taylor (2005b) - Included in Appendix H: Costing information.*

Warning: The default algorithm has been derived from data involving in-ground, proprietary GPTs with no unusual cost elements.

The alternative algorithm has been derived from a combined data set involving in-ground proprietary GPTs and open GPTs with no unusual cost elements.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

If users want to manually enter their own TAC value in music but only have a total construction cost estimate, they can use the following approximate relationships that have been derived from the CRCCH’s data set for all types of GPTs: Total construction cost ≈ 94% of TAC.

Typical annual maintenance (TAM) cost

TAM ($2004) = 698.3 x (V)0.7766

R2 = 0.72; p < 0.01; n = 57.

Where: V = average annual volume of removed trapped material (i.e. gross pollutants, coarse sediment and TSS) in m3.

See Table 1 for alternatives.

For literature values, see Taylor (2005b).*

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Currently music estimates V using the combined estimated volume of gross pollutants, coarse sediment and TSS that are trapped in the GPT per year. To adjust this manually (i.e. to include only one or two of these three elements), use the procedure provided in the tip box within Ponds and Sedimentation Basins (Costing).

Annualised renewal / adaptation cost (RC)

RC ($2004) = 0.70% of TAC p.a.

n = 34

No alternative size / cost relationships in music.

For literature values, see Taylor (2005b).

Warning: The default relationship has been derived from data involving in-ground GPTs, trash racks and litter baskets and release nets (as there was no data available for open GPTs).

Upper and lower estimates derived using a 68% confidence interval around the mean.

Renewal period

1 year

No alternative in music.

Default position due to lack of high quality data supporting an alternative period.

Decommissioning cost (DC)

DC ($2004) = 23% of TAC

n = 1

No alternative size / cost relationships in music.

Warning: This estimate is derived from only one high quality data set.

General caveats / notes for this type of device

* There are several estimates of capital and maintenance costs reported in the literature for open GPTs (see Taylor, 2005b or Appendix H: Costing information for a summary).

Table 2. Summary of cost-relationed relationships for open GPTs (ie. sediment basins with trash racks)
Element of Life Cycle Costing ModelDefault Option for estimation in MUSICAlternative(s)Notes
Life cycle

63 years.

n = 2

No alternative in MUSIC

Upper and lower estimates derived using a 84th and 16th percentile, respectively.

Total acquisition cost (TAC)

TAC ($2004) = 22460•(VU)0.4702

R2 = 0.59; p < 0.01; n = 72.

Where: VU = total volume of all stormwater and trapped pollutants in the unit when it is operating at its peak design flow (m3).

TAC ($2004) = 22460•(VU)0.4702

R2 = 0.34; p < 0.01; n = 121.

Where: C = area of the GPT’s catchment in ha.

For literature values, see Taylor (2005b) – Included in Appendix H: Costing information

Warning: The default algorithm has been derived from data involving in-ground, proprietary GPTs with no unusual cost elements.

The alternative algorithm has been derived from a combined data set involving in-ground proprietary GPTs and open GPTs with no unusual cost elements.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

If users want to manually enter their own TAC value in music but only have a total construction cost estimate, they can use the following approximate relationships that have been derived from the CRCCH’s data set for all types of GPTs: Total construction cost ≈ 94% of TAC.

Typical annual maintenance (TAM) cost 

TAM ($2004) = 698.3•(VU)0.7766

R2 = 0.72; p < 0.01; n = 57.

Where: V = average annual volume of removed trapped material (i.e. gross pollutants, coarse sediment and TSS) in m3

See Table 1 for alternatives. 

For literature values, see Taylor (2005b).*

 

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Currently music estimates V using the combined estimated volume of gross pollutants, coarse sediment and TSS that are trapped in the GPT per year. To adjust this manually (i.e. to include only one or two of these three elements), use the procedure provided in the tip box within Ponds and Sedimentation Basins (Costing).


Annualised renewal / adaptation cost (RC)

 

 RC ($2004) = 0.70% of TAC p.a.

n = 34 

No alternative size / cost relationships in MUSIC.

For literature values, see Taylor (2005b).

Warning: The default relationship has been derived from data involving in-ground GPTs, trash racks and litter baskets and release nets (as there was no data available for open GPTs). 

Upper and lower estimates derived using a 68% confidence interval around the mean.

Renewal period

1 yearNo alternative in MUSIC

Default position due to lack of high quality data supporting an alternative period.

Decommissioning cost (DC) 

DC ($2004) = 23% of TAC

n = 1 

No alternative size / cost relationships in MUSIC

Warning: This estimate is derived from only one high quality data set.

General caveats / notes for this type of device

*There are several estimates of capital and maintenance costs reported in the literature for open GPTs (see Taylor, 2005b or Appendix H: Costing information for a summary).

Table 3. Summary of cost-related relationships for in-ground GPTs.

Element of Life Cycle Costing Model

Default Option for Estimation in music

Alternative(s)

Notes

Life cycle

50 years.

n = 66

No alternative in music.

Upper and lower estimates derived using a 84th and 16th percentile, respectively.

Total acquisition cost (TAC)

TAC ($2004) = 22460 x (VU)0.4702

R2 = 0.59; p < 0.01; n = 72.

Where: VU = total volume of all stormwater and trapped pollutants in the unit when it is operating at its peak design flow (m3).

TAC ($2004) = 31430 x (C)0.3971

R2 = 0.34; p <0.01; n = 121.

Where: C = area of the GPT’s catchment in ha.

For literature values, see Taylor (2005b) - Included in Appendix H: Costing information.*

The default algorithm has been derived from data involving in-ground, proprietary GPTs with no unusual cost elements.

The alternative algorithm has been derived from a combined data set involving in-ground proprietary GPTs and open GPTs with no unusual cost elements.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

If users want to manually enter their own TAC value but only have a total construction cost estimate, they can use the following approximate relationships that have been derived from the CRCCH’s data set for all types of GPTs: Total construction cost  ≈ 94% of TAC.

Typical annual maintenance (TAM) cost

TAM ($2004) = 1202 x (C)0.3130

R2 = 0.36; p < 0.01; n = 77.

Where: C = area of the GPT’s catchment in ha.

See Table 1 for alternatives.

For literature values, see Taylor (2005b).*

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Annualised renewal / adaptation cost (RC)

RC ($2004) = 0.54% of TAC p.a.

n = 23

No alternative size / cost relationships in music.

For literature values, see Taylor (2005b).*

Upper and lower estimates derived using a 68% confidence interval around the mean.

Renewal period

1 year

No alternative in music.

Default position due to lack of high quality data supporting an alternative period.

Decommissioning cost (DC)

DC ($2004) = 20% of TAC

n = 18

No alternative size / cost relationships in music.

Upper and lower estimates derived using a 68% confidence interval around the mean.

General caveats / notes for this type of device

* There are several estimates of capital and maintenance costs reported in the literature for in-ground GPTs (see Taylor, 2005b or Appendix H: Costing information for a summary).

Quotes on ‘supply and install costs’ (the main component of total acquisition costs) can also be readily obtained from suppliers of GPTs with propriety designs.

Table 4. Summary of cost-related relationship for trash racks and litter baskets.

Element of Life Cycle Costing Model

Default Option for Estimation in music

Alternative(s)

Notes

Life cycle

25 years.

n = 8

No alternative in music.

Upper and lower estimates derived using a 68% confidence interval around the mean.

Total acquisition cost (TAC)

TAC ($2004) = 22460 x (VU)0.4702

R2 = 0.59; p < 0.01; n = 72.

Where: VU = total volume of all stormwater and trapped pollutants in the unit when it is operating at its peak design flow (m3).

TAC ($2004) = 31430 x (C)0.3971

R2 = 0.34; p <0.01; n = 121.

Where: C = area of the GPT’s catchment in ha.

For literature values, see Taylor (2005b) - Included in Appendix H.*

Warning: The default algorithm has been derived from data involving in-ground, proprietary GPTs with no unusual cost elements.

The alternative algorithm has been derived from a combined data set involving in-ground proprietary GPTs and open GPTs with no unusual cost elements.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

If users want to manually enter their own TAC values but only have a total construction cost estimate, they can use the following approximate relationships that have been derived from the CRCCH’s data set for all types of GPTs: Total construction cost ≈ 94% of TAC.

Typical annual maintenance (TAM) cost

TAM ($2004) = 421.7 x (V)0.6890

R2 = 0.66; p < 0.01; n = 75.

Where: V = average annual volume of removed trapped material (i.e. gross pollutants, coarse sediment and TSS) in m3.

See Table 1 for alternatives.

For literature values, see Taylor (2005b).*

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Currently music estimates V using the combined estimated volume of gross pollutants, coarse sediment and TSS that are trapped in the GPT per year.  To adjust this manually (i.e. to include only one or two of these three elements), use the procedure provided in the tip box within Life-Cycle Costing - Ponds and Sedimentation Basins.

Annualised renewal / adaptation cost (RC)

RC ($2004) = 0.85% of TAC p.a.

n = 8

No alternative size / cost relationships in music.

For literature values, see Taylor (2005b).

Upper and lower estimates derived using a 68% confidence interval around the mean.

Renewal period

1 year

No alternative in music.

Default position due to lack of high quality data supporting an alternative period.

Decommissioning cost (DC)

DC ($2004) = 7.3% of TAC

n = 7

No alternative size / cost relationships in music.

Upper and lower estimates derived using a 68% confidence interval around the mean.

General caveats / notes for this type of device

* There are some estimates of capital and maintenance costs reported in the literature for trash racks and litter baskets (see Taylor, 2005b or Appendix H: Costing information for a summary).

Table 5. Summary of cost-related relationships for release of net GPTs.

Element of Life Cycle Costing Model

Default Option for Estimation in music

Alternative(s)

Notes

Life cycle

10 years.

n = 5

No alternative in music.

Upper and lower estimates derived using a 68% confidence interval around the mean.

Total acquisition cost (TAC)

TAC ($2004) = 22460 x (VU)0.4702

R2 = 0.59; p < 0.01; n = 72.

Where: VU = total volume of all stormwater and trapped pollutants in the unit when it is operating at its peak design flow (m3).

TAC ($2004) = 31430 x (C)0.3971

R2 = 0.34; p <0.01; n = 121.

Where: C = area of the GPT’s catchment in ha.

Warning: The default algorithm has been derived from data involving in-ground, proprietary GPTs with no unusual cost elements.

The alternative algorithm has been derived from a combined data set involving in-ground proprietary GPTs and open GPTs with no unusual cost elements.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Typical annual maintenance (TAM) cost

TAM ($2004) = 652.6 x (V)0.4920

R2 = 0.93; p < 0.01; n = 7.

Where: V = average annual volume of removed trapped material (i.e. gross pollutants, coarse sediment and TSS) in m3.

See Table 1 for alternatives.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Currently music estimates V using the combined estimated volume of gross pollutants, coarse sediment and TSS that are trapped in the GPT per year.  To adjust this manually (i.e. to include only one or two of these three elements), use the procedure provided in the tip box within Ponds and Sedimentation Basins (Costing).

Annualised renewal / adaptation cost (RC)

RC ($2004) = 31% of TAC p.a.

n = 3

No alternative size / cost relationships in music.

Upper and lower estimates derived using an 84th and 16th percentile, respectively.

Renewal period

1 year

No alternative in music.

Default position due to lack of high quality data supporting an alternative period.

Decommissioning cost (DC)

DC ($2004) = 4.3% of TAC

n = 1

No alternative size / cost relationships in music.

Warning: This estimate is derived from only one high quality data set.

General caveats / notes for this type of device

Quotes on ‘supply and install costs’ (the main component of total acquisition costs) can also be readily obtained from suppliers of GPTs with propriety designs.

Table 6. Summary of cost-related relationships for side entry pit trap GPTs.

Element of Life Cycle Costing Model

Default Option for Estimation in music

Alternative(s)

Notes

Life cycle

5 years.

n = 10

No alternative in music.

Upper and lower estimates derived using a 84th and 16th percentile, respectively.

Total acquisition cost (TAC)

TAC ($2004) = 22460 x (VU)0.4702

R2 = 0.59; p < 0.01; n = 72.

Where: VU = total volume of all stormwater and trapped pollutants in the unit when it is operating at its peak design flow (m3).

TAC ($2004) = 31430 x (C)0.3971

R2 = 0.34; p <0.01; n = 121.

Where: C = area of the GPT’s catchment in ha.

For literature values, see Taylor (2005b) - Included in Appendix H: Costing information.*

Warning: The default algorithm has been derived from data involving in-ground, proprietary GPTs with no unusual cost elements.

The alternative algorithm has been derived from a combined data set involving in-ground proprietary GPTs and open GPTs with no unusual cost elements.

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Typical annual maintenance (TAM) cost

TAM ($2004) = 292.2 x (V)0.7353

R2 = 0.87; p < 0.01; n = 11.

Where: V = average annual volume of removed trapped material (i.e. gross pollutants, coarse sediment and TSS) in m3.

See Table 1 for alternatives.

For literature values, see Taylor (2005b).*

Upper and lower estimates derived using a 68% (or 1 standard deviation) prediction interval for the regression.

Currently music estimates V using the combined estimated volume of gross pollutants, coarse sediment and TSS that are trapped in the GPT per year.  To adjust this manually (i.e. to include only one or two of these three elements), use the procedure provided in the tip box within Ponds and Sedimentation Basins (Costing).

Annualised renewal / adaptation cost (RC)

RC ($2004) = 0.70% of TAC p.a.

n = 34

No alternative size / cost relationships in music.

For literature values, see Taylor (2005b).

Warning: The default relationship has been derived from data involving in-ground GPTs, trash racks and litter baskets and release nets (as there was no data available for side entry pit trap GPTs).

Upper and lower estimates derived using a 68% confidence interval around the mean.

Renewal period

1 year

No alternative in music.

Default position due to lack of high quality data supporting an alternative.

Decommissioning cost (DC)

DC ($2004) = 16% of TAC

n = 28

No alternative size / cost relationships in music.

Warning: The default relationship has been derived from data involving in-ground GPTs, trash racks and litter baskets, and release nets (as there was no data available for side entry pit trap GPTs).

Upper and lower estimates derived using a 68% confidence interval around the mean.

General caveats / notes for this type of device

* There are some estimates of capital and maintenance costs reported in the literature for side entry pit traps (see Taylor, 2005b or Appendix H: Costing information for a summary).

Quotes on ‘supply and install costs’ (the main component of total acquisition costs) can also be readily obtained from suppliers of GPTs with propriety designs.