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- Trash racks (n = 17): average capital cost ≈ $966/ha; average annual maintenance cost ≈ $2,346; and average annual maintenance cost per ha ≈ $39.
- Large trash baskets (0.5 m3 m3 capacity) (n = 9): average capital cost ≈ $2,117/ha; average annual maintenance cost ≈ $708; and average annual maintenance cost per ha ≈ $42.
- Proprietary in-ground devices (n = 19), not including SEPTs: average capital cost ≈ $6,122/ha; average annual maintenance cost ≈ $765; and average annual maintenance cost per ha ≈ $156.
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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 m3m3/sec (when the flow is at its peak treatment rate).
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Melbourne Water (2003a) has a basic construction cost estimation model for large greenfield wetlands in Melbourne. It It allows for typical site characteristics to be used as factors that determine overall construction cost. The The cost relationships appear to be based on a limited data set (i.e. tender information for ~8 BMPs).
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Fletcher et al. (2005) suggested that the construction cost of an infiltration trench is ~$60-80/m3 m3 of trench (assuming the trench is 1 m wide and 1 m deep).
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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 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 Roadside swales are typically 3m wide.
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