Melbourne Water STORM Help

Treatment Types


Rainwater Tank

Rainwater tanks are connected to houses to capture stormwater running off the roof for reuse on the property. Once captured this water is generally used for watering gardens or for toilet flushing.

Design Tips

The size of the rainwater tank should be based upon the amount of use. The STORM calculator assumes the tank is connected to the toilet with a water use rate of 20 litres per person per day. For residential properties the number of bedrooms is used as a surrogate for the number of people using the tank. For industrial and commercial properties an estimate of the number of occupants using the building is required.

The supply reliability of a rainwater tank is directly influenced by:

Results of analysis using MUSIC led to a procedure for determining the reliability of water supply from tanks of different sizes for toilet flushing.

More detailed technical advice on the design on these systems can be found in the WSUD Engineering Procedures which can be purchased from www.publish.csiro.au

STORM options and assumptions

There is only one option available in STORM for rainwater tanks - ie connection of tank for toilet flushing. Different sized tanks and different number of people using the tank can be entered. If only a portion of the roof is connected to the tank the remaining area needs to be entered as a separate entry.

STORM should not be used if the tanks are intended to be part of a treatment train.

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Pond

Ponds are often used as storage areas for water as well as a first step in a treatment train (multiple stormwater treatment measures). Pollutants are removed from the water through natural processes and the settling of solids over a period of time.

Design Tips

It is important that ponds are designed so that water does not stagnate and cause problems such as algal blooms. A water detention time of 72 hours is generally suitable.

More detailed technical advice on the design on these systems can be found in the WSUD Engineering Procedures which can be purchased from www.publish.csiro.au

STORM options and assumptions

STORM assumes a permanent pool volume equal to 0.6 times the surface area of the pond (a pond depth of 0.6 metres).

STORM should not be used if the pond is intended to be part of a treatment train.

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Wetland 200mm
Wetland 400mm

Wetlands consist of a number of different zones that filter and treat pollutants in stormwater using vegetation and natural processes, as well as the settling of suspended solids.

Design Tips

Wetlands systems can be sensitive to large amounts of nutrients that can cause algal blooms, or stagnate water and encourage mosquitos. A detention time of 72 hours should be designed for to help prevent these problems from occurring.

More detailed technical advice on the design on these systems can be found in the WSUD Engineering Procedures which can be purchased from www.publish.csiro.au

STORM options and assumptions

STORM contains two standard options for wetlands, an extended detention depth of 200mm or 400mm. The extended detention depth is the depth between the permanent pool volume surface level and the overflow level. A larger extended detention depth will result in a higher reduction in pollutants.

STORM should not be used if the wetland is intended to be part of a treatment train.

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Raingarden 100mm
Raingarden 300mm

Raingardens consist of a filter area that typically drains into a porous pipe. Raingarden work by treating pollutants and filtering out solids before discharging into the stormwater system.

Design Tips

A larger extended detention depth will result in more pollutant treatment, however it is important that the detention depth is designed to suit the expected flows into the system.

More detailed technical advice on the design on these systems can be found in the WSUD Engineering Procedures which can be purchased from www.publish.csiro.au

STORM options and assumptions

There are two types of raingardens to choose from in STORM, an extended detention depth of 100mm or 300mm. The extended detention depth is the depth between the surface level of the system and the top of the overflow weir.

STORM should not be used if the raingarden systems are part of a treatment train.

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Infiltration Sand
Infiltration Sandy Loam

Infiltration measures are designed to encourage stormwater to infiltrate into surrounding soils. Treatment efficiency is highly dependent on local soil characteristics.

Design Tips

It is important that catchment characteristics and pollutant types and loads are taken into consideration in the design of the infiltration system to ensure it is appropriate.

More detailed technical advice on the design on these systems can be found in the WSUD Engineering Procedures which can be purchased from www.publish.csiro.au

STORM options and assumptions

There are two types of infiltration systems available in STORM relating to the type of soil medium ie either sand or sandy loam. Sand will result in a faster seepage rate (180 to 360 mm/hour) then sandy loam (36 to 180 mm/hour). Greater treatment will result from the sandy loam system.

STORM should not be used if the infiltration systems are part of a treatment train.

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Buffer Strips

Buffer strips are vegetated strips that convey runoff from a hard surface to a downstream drainage system. Buffers are effective in removing coarse and medium sized sediment from stormwater.

Design Tips

Ensure levels are correct so that runoff can enter the buffer unimpeded.

Buffer strips are typically grassy areas although a range of species could be used.

More detailed technical advice on the design on these systems can be found in the WSUD Engineering Procedures which can be purchased from www.publish.csiro.au

STORM options and assumptions

The one option in STORM assumes (like other systems) that 100% of the impervious area is connected to the treatment. STORM also assumes that seepage loss through the buffer is zero.

STORM should not be used if the buffer strips are intended to be part of a treatment train.

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