Upper parramatta river catchment trust osd handbook

From pump types and components, to precautions for viscous liquids, to life cycle costs, you will find answers to your technical questions about pumps in our Pump Handbook. Livoti has co-authored two books with the Hydraulic Institute Pumps System and Scheduling Handbook published in and now in its third edition The fourth edition of the Pipe Friction Handbook is now available and has been thoroughly reviewed and updated to conform to the latest Australian Standards.

The friction losses relative to each pipe type and its sizes are covered in the friction tables. It is designed to allow the reader to readily calculate the friction losses in a pump system using the most commonly used pipes and fittings.

The water use to shorter time scales. The single dwelling scenario consists of a m2 The percentage of rainwater tank volume that can allotment, a house with a roof area of m2 and be counted as part of the overall site OSD storage a paved surface area of m2 Figure 6.

The Detention Handbook to this site results in a site average percentage of rainwater tank volume that storage volume of Hot water, toilet and Scenario Outdoor outdoor uses 0. Hydrographs of stormwater discharge insignificant peak discharge reduction from the from rainwater tanks and OSD from a single storm allotment and small reductions in OSD site event storage requirement for all ARIs greater than 2 years.

The reason for this result is simple. Analysis of urban subdivisions by Coombes et al. Rainwater tanks only intercept roof runoff whereas and a revealed that the use of source all stormwater runoff from the roof, pervious and control measures including rainwater tanks impervious areas is directed to the OSD tank that produced substantial peak discharge reductions also provided more storage space than the from the subdivided catchment that will reduce the rainwater tank prior to the annual maximum need for centralised stormwater infrastructure.

A storms. An analysis of the However, focussing on peak discharge obscures performance of a subcatchment that contains a significant benefit attributable to rainwater tanks.

The OSD tank scenario is shown to have a significantly lower peak discharge than the two Other benefits are attributable to the rainwater rainwater tank scenarios. However, the important tank scenarios. The rainwater tank provides retention as The townhouse case study, illustrated in Figure 8, well as detention storage, while the OSD tank only consists of 9 double storey townhouses with roof provides detention storage.

Water levels in areas of 98 m2 each and paved surfaces with an rainwater tanks used to supply domestic toilet area of m2 situated on an allotment with an flushing, outdoor and hot water uses are area of m2.

This ensures that the to this site results in a site storage volume of The importance of reducing stormwater runoff Stormwater peak discharges from the townhouse volumes rather than peak discharges from development for the different scenarios are individual allotments for stormwater management reported in Table 5.

Table 6 presents for the OSD and rainwater tank scenarios the OSD volumes required to ensure that there are no significant overflows from the 1 allotment up to the year ARI. Figure 8. Schematic of the townhouse Table 7.

Percentage of rainwater tank volume development. Conclusions Nonetheless, stormwater discharges from the rainwater tank scenarios are dominated by In view of the fundamental limitations of the discharges from the impervious areas not design storm approach, continuous simulation connected to the rainwater tanks. In combination was used to evaluate the contribution of rainwater with a policy to minimise impervious areas directly tanks to manage stormwater runoff from connected to the street drainage system the use allotments located in the Upper Parramatta River of rainwater tanks could produce equivalent Catchment.

Pumping Station. Roof areas in the townhouse development DRIP was used to generate years of occupy a greater proportion of the site area than pluviograph data which was input to the allotment the roofs in the single dwelling case study. Rainwater tanks revisited: storage. Unpublished PhD. For a management. The Coombes P. Tank variation depends on the number of occupants Paddock: A comparison between WSUD and and the amount of tank airspace reserved for traditional approaches.

Research Report for detention storage and the fraction of allotment Newcastle City Council. Department of Civil, drained by the rainwater tank s. As the number of Surveying and Environmental Engineering. Nikinba available on average at the beginning of a storm. Similar to Baulkham Hills. Note that an accredited PCA must issue the stormwater construction certificate which is generally council.

On average 12,L is required to achieve the effective 10,L. Warringah Council, has updated policy on OSD compensation. Lane Cove Council, will now allow OSD requirements to be removed on a single dwelling site where a 10,L raintank is proposed. Lane Cove Council, to adopt new code very shortly.

All Single dwelling that require OSD will be given the option to replace it with a larger rainwater tank. Watch this space for further details as it comes available. Canada Bay City Council, adopts new code. All Single dwelling now require OSD unless an absorption system can be designed to accommodate the required runoff. Storage volume of approx. Strathfield council has taken up the policy of NO charged systems to rainwater tanks.

The implication are numerous, and will cost the average single dwelling considerably more than what Basix had estimated. Basix has taken a side line and is not willing to enforce the roof collection system as being part of the conservation system, and hence allowing council to enforce its no charged system policy to the harvesting system, which Basix has relied upon.

Please ensure that you contact our offices before any design work commences for any applications to Strathfield Council, to ensure the design proposed can be achieved. Bluescope Water's revised rainwater tank schedule of available tanks, which was effective on the 12th of December Bluescope has advised that their older tanks will be available till the end of the month. Any existing jobs that have not yet been ordered, and were using tanks sizes no longer being produced, will have to refer to the approved design drawings, to check if alternatives were allowed for, and what limitations exists.

Another note to mention is that the Bluescope schedule refers to a Nominal storage and an AS storage. We have spoken to Basix, who are now updating their definitions, to state that the volumes required under Basix are the Nominal storages, and not that referred to as AS ISC makes major improvements to website to assist clients.

Design Phases and downloads added. Low Level Properties explained. Chapter 11, now requires that all dual occupancy proposals that fall away from the street that cannot obtain a drainage easement and require an alternative method of stormwater drainage will require OSD, subject to a council assessment. Basix now implemented in all NSW councils. Multi unit assessment tool available and compulsory from 1st of October Lane Cove Council to issue new stormwater code.

Now anticipated for late The amendment is mainly to correct some discrepancies with Basix, and some minor additional areas noted below:. Storage tank for pump out is high. Rainwater tanks will now be considered as part of the OSD subject to a number of variables such as no of occupants. Failure to act could create enormous problems within the next generation. Water Sensitive Urban Design WSUD is a process by which a development is designed so as to mimic the natural pre-development water cycle.

In an undeveloped site rainwater may fall on vegetation or pervious ground surfaces. Typically there will be some infiltration into the topsoil, ponding on flat areas from where the water may evaporate and absorption by vegetation. Any overland flow that results is likely to be sheet flow over a vegetated surface which means that velocities are low and the stormwater may take a considerable time to reach the nearest watercourse. This extended period of flow to watercourses reduces the risk of flooding because a significant portion of the rainfall takes a long time to reach the watercourse.

Rainwater which has infiltrated into the topsoil may also find its way to local watercourses but this takes much longer again. This water may also flow into ground water if the subsoil is sufficiently pervious. After development however there is less vegetation, more impervious area and a more efficient means of collecting and transporting flows off site. This increases the volume of flow into the watercourses and reduces the time taken to reach the waterway.

This leads to greater flow depths in the creek and the likelihood of flooding. OSD is one way that stormwater can be temporarily detained close to where the rain falls to help overcome the quickening of flows to the creek systems.

The same volume of stormwater will reach the waterway but at least it takes several hours longer which, in this catchment, helps reduce the risk of flooding downstreami.

The OSD solution should create a sustainable solution for peak stormwater flow management, which complements any WSUD aspects of the development. However, there should be no reduction in the volume of storage provided,nor increase in the site discharge to the downstream drainage system.

Section 4. The policy, control standards, procedures and approval processes detailed in this Handbook apply throughout the km2 of the upper Parramatta River catchment. The catchment boundaries are shown in Figure 3. For areas outside the catchment, interested parties should contact the relevant local council.

An approximate procedure for applying the methodology outside the catchment is given in Appendix Giii and the parameters for the design of OSD systems in other catchments within the four councils are given in Appendix Fiv.

On-site Stormwater Detention OSD systems temporarily detain stormwater on a site, in order to limit the discharge leaving the property to a pre-determined rate which will ensure that the development does not increase downstream flood discharges for storms up to the year ARI event. Any existing obligation to provide and maintain an OSD system will be found in the development consent applicable to the property or on the property title itself.

In the case of a proposed development, the guidelines given below in sections 3. For residential subdivisions, OSD was not generally required on lots created by subdivision until when the common OSD policy was adopted by the four councils in the upper Parramatta River catchment. However, all lots created after that date have a requirement for OSD applied as a condition of development consent for the subdivision.

OSD requirements generally apply to all types of development and redevelopment on both flood liable and flood-free sites. These include the following:. This exclusion is aimed principally at small areas within large commercial or industrial sites. It does not apply to any developments where the development area is greater than m2 nor to dual occupanciesii;.

Generally, OSD applies to the entire site, but there may be exceptions in certain circumstances. On an already-developed property, the OSD requirements apply only to the area of the new development, provided runoff from previously developed areas can be excluded from the OSD storage. Where an additional dwelling is proposed on a lot with an existing dwelling, the OSD requirements will relate to the additional dwelling and a curtilage for anticipated paths, driveways and paved areas.

Where two or more dwellings are constructed on the same lot at the same time, the OSD requirements will be applied to the entire site. When an existing residential property is subdivided to create a single additional lotii, the OSD requirements will relate only to the area of the new allotment.

The OSD storage facilities may be located on the remainder of the original property, provided the combined peak discharge from both lots is no greater than if the OSD systems were located on the new lot. The OSD requirements apply to the whole development area including roads and paths, not just the individual lots. The best solution will normally be for the detention storage to be located on one lot for the whole subdivision.

However, if individual storages are provided on each lot, the discharges should be adjusted to provide the equivalent storage for the area of roads or paths. Portions of large lots which are unaffected by the development may be excluded from the area to be controlled by the OSD systems, provided flows from these areas can be diverted around the OSD system.

Council approval must be obtained before excluding portions of a lot from the OSD requirements. Creeks, waterways and drainage swales that carry major concentrated flows around the storage area are defined as floodways. The area of the floodway can be excluded from the site area for the purpose of calculating the site storage requirements, provided that the area is protected from development by an appropriate covenant or easement.

Note: Overland flowpaths, which cater for minor flows cannot be excluded from the site area for the calculation of OSD. Where the proposed development is of a vacant site or a complete redevelopment of an already-developed property, the OSD requirement will relate to the whole property. The access driveway to battle-axe blocks shall be included in the site area used for calculation of the site storage requirements.

In some situations, where the site is flood prone and the watercourse flows through the site, the council may accept the provision of additional mainstream flood storage in lieu of OSD. In these cases, the storage must be available over the full range of storm events and allow for the fact that mainstream flood levels will tend to decrease over time. This will need to be adjusted in accordance with the procedures set out in Section 5.

This will need to be adjusted where either full high early discharge HED is not achieved or the permissible site discharge is reduced according to Section 5. It is emphasised that these are general guidelines that will be varied according to the nature of the development and the location of the storage.

The maximum depth of ponding in above ground storages is mm. Council may approve deeper ponding in individual cases where the applicant demonstrates that safety issues have been adequately addressed. For example warning signs and or fencing should be installed where the depth exceeds mm or adjacent to pedestrian traffic areas.

A maximum gradient of ie 1 vertical to 4 horizontal will be required on at least one side to permit safe egress in an emergency. Where steep or vertical sides are unavoidable, due consideration should be given to safety aspects such as the need for fencing, both when the storage is full and empty.

Note: The OSD system must be constructed at the time of subdivision and not deferred until the construction of the individual dwellings except where the subdivision is up to seven lots, if it is proven there are site restrictions. See Section 4. When the OSD requirements are implemented through the development approval and construction certificate process, the approval is in three stages:.

Development Application - submission and approval of a conceptual layout of the OSD system Stormwater Concept Plan Except at Holroyd City Council where detailed design required with development application;x. Construction certificate - submission and approval of the detailed design, including calculations and construction plans and details;. Final Approval - submission and approval of work-as-executed drawings, certificates of hydraulic and structural, if required compliance and legal instruments protecting the OSD system.

Note: If the OSD system was constructed at the subdivision stage, the system may need to be re-certified at final approval to ensure it will still function as designed.

OSD Designer addresses consent conditions and prepares maintenance schedule. Plans forwarded to Council or private certifier. Work-as-Executed drawings prepared. OSD Designer certifies hydraulic performance of construction. This sectioni sets out the steps in the approval process from the Stormwater Concept Plan through the detailed design to the construction and final approval.

OSD is best considered as early as possible in the development process, particularly where the proposal includes WSUD principlesii, so that the most efficient and effective system can be designed and installed. There are a number of issues to be addressed at the conceptual stage which will have a significant impact on the final solution:. Underground storages should be the option of last resort. The use of surface storage reduces the cost of the system and improves accessibility for maintenance See Section 4.

Council approval will only be considered for subdivisions of up to 7 lots where there are demonstrable site restrictions. The purpose of a SCP is not to provide a detailed design, but to identify the drainage constraints and to demonstrate that the OSD system can be integrated into the site's overall water management and proposed layout.

The steps involved in preparing a SCP are summarised in Figure 4. It should be noted however, that Holroyd City Council no longer accept SCPs in conjunction with the development application and require a detailed OSD design because in many parts of the City, detailed levels are required to show that the OSD facility will function correctly.

An OSD system is an integral part of the entire development and can be expensive to retro-fit once the site layout has been established. The control of stormwater flows through the OSD facility may facilitate the provision of water quality improvements on sites where these are required by the development consent. Treatment of the stormwater will often be easier once the discharge has been controlled by the OSD facility.

An OSD storage is designed to deal with stormwater runoff from only a particular area. If external flows enter the storage, it will fill more quickly, causing a greater nuisance to occupiers and it will become ineffective in terms of reducing stormwater flows leaving the site.

The OSD design must therefore cater for external flows which can enter the storage. This is done by either increasing the size of the storage, or by diverting the external flows around the storage. It is important to ensure that the by-pass flow is directed to a suitable outlet point and not directed onto an adjoining property. It is preferable if the diversion drainage can be designed to avoid unnecessarily concentrating the flow and in some instances it may be possible to respread the flow to sheet flow.

The diversion may be achieved with a grass swale or raised garden bed in many instances. This will provide a. In addition, the use of a landscaped solution will often be more attractive and cheaper. For the purposes of the OSD policy, the external flows can be divided into two categories: overland flowpaths and floodways.

These are surface drainage systems which cater for relatively minor sheet flow from upstream properties and convey it around the storage or allow it to pass across the site without interference eg. The area of the flowpath must be included in the site area when determining the site storage requirements. These surface drainage systems convey relatively major concentrated mainstream, surface or surcharge flows from an upstream catchment around the storages eg.

Where an existing easement is insufficient to cater for the year ARI flow from the upstream catchment, it may need to be widened to cater for the flow. This would reduce the area for calculating the storage requirements. There are a small number of situations where part of the external flow would not enter the storage. This portion of the flow need not be collected nor diverted.

For example: dual occupancies where a second dwelling is proposed on a lot with an existing dwelling; OSD is required for the area of the additional dwelling plus a curtilage to cover paths and paved areas.

Runoff from the remainder of the lot need not be directed to the OSD storage nor is it necessary to divert external flows affecting this portion of the lot. Here again external flows affecting the undeveloped areas need not be diverted. Where possible, the drainage system should be designed to direct runoff from the entire site to the OSD system. Sometimes, because of ground levels, the receiving drainage system or because of other circumstances, this will not be feasible.

For areas not draining to an OSD storage, the storage volume is still calculated on the entire site area while the PSD is adjusted downwards according to procedures in Section 5. This makes sure the storage is fully used in the design storm. In practice this does not occur and an adjustment to the storage volumes is necessary after the discharge characteristics have been fixed. This approximate volume is refined at the detailed design stage. From 1 May xii, design and certification will only be accepted from persons having acceptable professional accreditation.

A detailed design submission is required to support an application for a construction certificate or the engineering plans of a development. The specific site drainage constraints will have been identified and addressed conceptually in the SCP, thereby simplifying the detailed design. The purpose of the detailed design submission is to finalise the design of all components of the OSD system, provide a set of plans and details for construction of the system, and detail the maintenance procedures necessary to ensure the long-term effectiveness of the system.

The steps involved in a typical detailed design submission are outlined in Figure 4. One of the concerns raised by OSD designers is that they may not see the approved OSD plans if they are not the applicant. Council may not be entitled to send a copy to the designer unless the applicant gives permission. If the applicant authorises release of a copy of the plans, this will allow designers to adjust future designs to better suit the councils requirements.

It will also ensure that the designer has the approved plans if engaged to provide the hydraulic certification for the OSD facilityxiii. Where WSUD components are proposed, calculations and details of both the OSD and WSUD components are required which clearly demonstrate that the designer has integrated the systems so as to allow for the impact of each on the design of the other.

For further information on the details to be submitted for the WSUD components please contact the local council. Copies of the report or the final report which supersedes it will be available from the Trust web site www.

Distribute final storage volumes to minimise nuisance to property owners Check underground storages for - access Design of Storage - maintainability in Detail Determine maximum water surface levels Ensure sufficient weir capacity for excess flows. Ensure year flows are conveyed to basin for areas designed to Design Internal drain to storages Drainage Check flowpaths and floodways have adequate capacity to ensure external year discharges routed around basin.

The DCP is the key feature in regulating discharge from the site. Hydraulic model tests conducted on behalf of the Trust by Manly Hydraulics Laboratory established a set of generic design parameters for DCPs incorporating HED, screens and orifice control. Proprietary products or in-situ devices meeting these guidelines are not required to provide a laboratory-determined head-discharge relationship. Other forms of discharge control are commercially available and can be used in the catchment provided that:.

A typical discharge control pit with an orifice control is shown in Figure 4. The minimum orifice diameter is 25 mm. In determining whether an orifice is suitable, it will be necessary to demonstrate:. High early discharge HED is important in minimising the storage volume required.

In order that HED can be assumed:. The Discharge Control Pit will need to be maintained regularly. To assist with inspecting and cleaning, the minimum internal dimensions of the DCP should beii:. This means that inspections and maintenance are simpler and remain the responsibility of the joint owners rather than an individual. To ensure that free discharge is maintained the outlet needs to be well ventilated and the outlet pipe needs to be large enough to prevent submergence.

The orifice should be centred in the outlet pipe to avoid edge effects. See Section 6. A small aperture-expanded steel mesh, such as Maximesh Rh, is recommended for orifices less than mm in diameter. This type of screen retains relatively fine material eg. For orifices larger than mm, the screen area necessary for a fine mesh screen can make it difficult to fit in a DCP.

Where the grid mesh is used, a fine mesh screen should be installed upstream of the DCP, for areas likely to collect litter or debris. The inlet pipe to a DCP should direct inflows parallel or at a small angle to the screen.

Perpendicular inflows drive debris into a mesh screen making it difficult to dislodge. When inflows are directed parallel to the screen, the debris is layered on the screen but is blown off when the inflow exceeds approximately times the PSD.

This arrangement is illustrated in Figure 4. The performance of the orifice and screen is influenced by the orientation of the screen. To assist in shedding debris, the screen should be positioned as close to vertical as possible. This allows debris to fall off once the water level in the DCP drops. However, the screen must fit securely to the pit to avoid debris floating over or around the screen and blocking the orifice. See Figure 4. Blockages can occur if the screen is accidentally placed upside down.

Fitting a handle to the screen not only reduces the chance of incorrect placement but also makes removal for cleaning easier. Fixings need to be selected to suit the screen and to promote easy removal for maintenance. Reducing the screen size also facilitates cleaning by reducing the weight. Proprietary screens may be considered to achieve this end. After being cut to size, Maximesh screens need to be 'hot dipped' galvanised to prevent corrosion. All mesh screens deflect under high inflows and heavy debris loading and should be braced to stop debris being carried around the screen.

The selection of the most appropriate type of storage for the site is critical to the quality, effectiveness and cost of the OSD design. Every attempt should be made to provide the majority of the volume as surface storage rather than below ground.

Also, maintenance is simpler and generally safer. Designers should be aware, however, of the increased risk of subsequent alteration to the storage by future occupants and should try to provide a finished landscaping product which needs no further improvement.

It may be necessary to provide primary storage below ground to reduce the chance of ponded water causing problems for occupiers of the site. However, innovative design can reduce the volume of below ground storage required. See Appendix H for further details. Designers should also seek to provide larger common storages in multi-owner developments or subdivisions.

This removes the need for a large number of smaller storages which will have increased design, construction and maintenance costs. Particular problems have been experienced in multi-lot subdivisions where OSD storages on individual lots have proved to be considerably more costly to install than a single OSD storage would have been. Care should also be taken with the use of private courtyards considered to be yards less than 60 m2 in area for storage for safety reasons.

OSD storage in these courtyards will not be permitted if the area is less than 25m2 and Councils specific approval will be required for courtyards whose area is. Recommendations for allowable depths and the frequency of ponding are given in Table 6. OSD storages for subdivisions must be constructed prior to the release of the Linen Plan rather than deferred until the construction of the dwelling because of the problems faced by owners in deferred construction.

Deferral still requires the written approval of Council. The walls of each storage must be entirely within the property so as to avoid possible disputes with adjoining land holders if the common boundary fence was used as part of the storage. The relative location of the DCP and the storage is an important design consideration.

As shown in Figure 4. The design processes outlined in section 5 of this Handbook are generally not applicable for on-line storages. There are some specialised discharge control devices, such as float controlled discharge regulators that have different discharge characteristics.

These may be used on-line and still achieve HED and discharge rates independent of the shape of the storage. The characteristics of these devices should be checked with the manufacturer and verified with the Trust prior to preparation of a detailed design. Here the DCP discharge and the storage volume is independent of each other. On-line storage systems require more storage volume than off-line storages.

There are few absolute requirements when designing a surface storage. These guidelines have been framed to allow the designer maximum flexibility when integrating the storage in the site layout. A discussion of the general principles of storage design is included in Section 6. However the desirable minimum design parameters for surface storage systems are set out below.

The floor levels of buildings adjacent to surface storage areas should have a suitable freeboard to avoid the risk of water entering the building in storms more severe than the design storm or in the event of system blockage.

The free board is to be calculated from the top water level including the depth of flow over the overflow weir. The walls creating each storage must be entirely within the property so as to avoid possible disputes with adjoining land holders if the common boundary fence was used as part of the storage. The desirable minimum surface slope is 1. The absolute minimum surface slope is 1. Side slopes should be a maximum of 1V to 6H where possible. See also Section 3.

Sub-soil drainage should be provided around the outlet to prevent the ground becoming saturated during prolonged wet weather. Where the above ground storage is located in the same area as the childrens play equipment, pool type fencing, including a child proof gate, must be provided to ensure that young children can only enter the area under supervision.

Water levels can rise quickly in the basin and pictorial signage such as that shown in Appendix C must be installed to reinforce to need to leave the area when it rains. If using private courtyards for OSD storage, the area of courtyard must be between 25 and 60m2 and specific Council approval must be obtained. In this Handbook, private courtyards are considered to have an area of 60 m2 or less.

Areas greater than that are treated as gardens. The storage should generally not commence ponding more frequently than once every 5 years. Provision should also be made for the future installation of garden sheds and the like by leaving an area of the courtyard above the storage depth.

The maximum depth of storage should be limited to mm unless otherwise approved by Council and the area must be designed to allow safe egress as the storage fills with wateriii. The structural adequacy of retaining walls must be checked, including the hydrostatic loads caused by a full storage. Free standing timber log retaining walls should not be used to create a storage, but timber can be satisfactory as part of an earth retaining wall which prevents any significant leakage.

To avoid damage to vehicles, depths of ponding on driveways and car-parks should not exceed mm under design conditions. Where the storage is to be provided in a commonly used area where ponding will cause inconvenience eg.

The use of underground storages for total storage volumes should be avoided where at all possiblei. However, locating a small proportion of the required storage underground can often enhance a development by limiting the frequency of inundation of an open storage area. In very difficult topography, the only feasible solution may be to provide all or most of the storage volume underground. However the designer should recognise that underground storages:.

The optimal solution will generally be a system where the property owner is able to carry out the routine maintenance. Where the structure cannot be maintained by the property owner or occupier, this must be clearly identified in the maintenance schedule. When preparing a design for underground storage, designers should be aware of the provisions of AS Safe Working in a Confined Space. Where practicable, the design should eliminate the need to enter the confined space for maintenance or other purposesii.

A sign indicating that the storage is a confined space and that entry should be restricted to trained personnel should be fixed to each opening into the underground storage. A typical sign is included in Appendix C. The walls of each storage must be entirely within the property so as to avoid possible disputes with adjoining land holders if the tank or underground storage encroaches onto their land.

Concrete covers are to be avoided for this reasoni. Openings must be wide enough to allow easy entry to a storageii, ie: x storages up to mm deep x storages greater than mm deep. The minimum clearance height for accessible tanks is mmiii.