Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER PART 6.4: DEVELOPMENT ENGINEERING This Part of the CDCP provides a common set of engineering design, construction and management principles, which when implemented properly, will ensure a high standard of engineering design for all development in Canterbury. This Part applies to all development, including building work and subdivision, and is designed to ensure that the quality of Canterbury’s infrastructure and assets is consistent with the future needs the community. The engineering requirements in this document cover the following areas: their retention and protection can be incorporated into the design of the engineering infrastructure. The CDCP is intended to prevent or reduce the impact of increased development, through integrated design and the use of on-site detention of storm water. OBJECTIVES FOR DEVELOPMENT ENGINEERING O1. Infrastructure design and appropriate to each site. Site engineering requirements, Pedestrian access, Vehicular access, Stormwater, Submission requirements, Flood management, 6.4.1 Final certification. i. ABOUT DEVELOPMENT ENGINEERING O3. Possible engineering constraints to the development are considered at the first stage of the design of the development. O4. Public infrastructure managed by Canterbury City Council is not compromised by development. i. In the urban environment, stormwater drainage is rapidly changing with new challenges being encountered due to the ever changing climate and environment, and it is becoming ever more important to monitor the usage of stormwater and rainwater responsibly and economically. Design conflicts can be identified at an early stage in the processes involved in preparing engineering plans, and through intelligent use of driveways, parking areas and landscaping, costs can actually be reduced. Trees represent an important asset to the community, but could affect the layout or design of a development, and Submission requirements When submitting a development application, the information in Table 6.4.1 (following page) is required, according to the type of development: 6.4.2 The engineering infrastructure provided with development is often in the public domain, on land that is owned and managed by Council, or will affect Council’s engineering assets (that could already be on public or private land). Council, therefore, must ensure that all engineering infrastructure that is provided with development meets appropriate standards and will be complementary to its public infrastructure. With urbanisation comes the transformation of landscape, pervious areas of grass and vegetation into impervious surfaces such as roofs, concrete and paving. Such transformation results in less water being used by vegetation or naturally infiltrating into the ground and leads to an increase in the amount of stormwater runoff. is O2. Quality engineering works are produced for all developments. This Part will apply when assessing development applications and construction certificate applications where engineering work is required. construction Pre-lodgement requirements The applicant must satisfy the pre-lodgement requirements, as specified in the checklist in Table 6.4.1. In terms of engineering requirements, the applicant must obtain the following prior to the submission of the development application, with the exceptions listed in Table 6.4.1. Failure to do so will prevent the lodgement of the development application: Street alignment levels, Tree report, both internal and external. Street Alignment Levels ii. The street alignment levels are critical in the design of the development and incorporation of this information at the initial design phase could reduce the likelihood of redesign at a later stage. Tree Report iii. The tree report will provide information on the likely development conditions to be set in regard to trees, both within the property and adjacent to the property, in the road reserve. Consideration of the trees at the initial design could again prevent redesign at a latter stage. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-1 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Pre-lodgement Requirements Drainage Plan Traffic Traffic Plan Management Control Plan Traffic Generation Report Traffic Manoeuvrability Report Street Alignment Levels Tree Report No No No No No No No Extension to Single dwelling Yes, if new street access is proposed Yes Yes No No No No Yes, if new street access is proposed Yes Yes Single dwelling No, unless requested. No, unless requested. No, unless requested. No, requested. Yes Yes Yes No, unless requested. No, unless requested. No, unless requested. Yes Yes Yes Yes No, unless requested. Yes If 10 or more dwellings proposed. Yes Industrial Yes Yes Yes Yes Yes Yes Yes Commercial and Retail Yes Yes Yes Yes Yes Yes Yes Tourist facility Yes Yes Yes Yes Yes Yes Yes Aged Care Yes Yes Yes Yes Yes Yes DA Multi-unit housing Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No, unless requested. Yes Yes Yes Yes Yes Yes No, unless requested. No, unless requested. No, unless requested. No, requested. Transport links Yes Yes Yes Yes Yes Yes Yes Open Space Yes Yes Yes No, unless requested. No, unless requested. No, unless requested. No, requested. Internal change of existing premise Dual Occupancy Townhouse/ Villa Child Care Centre Heritage site Listed Table 6.4.1 6.4.3 i. ii. unless unless Submission requirements by development type Off-site engineering requirements Design the development to utilise and integrate with the existing infrastructure, and minimise any potential adverse effects on community assets – unless an applicant is required to undertake infrastructure improvement works adjacent to the property that may alter the existing level or location of the infrastructure. Consult with Council engineers prior to DA submission to ascertain the possible improvement to infrastructure required for the development. This is advice only, as the final determination of works required will be conditioned as part of the development application process. iii. Take into account the following in the design of proposed development: unless Finished road and footway levels, Location of proposed vehicular access with respect to drainage structures/infrastructure, traffic facilities, street trees, signs, power poles, utilities and other infrastructure. Council approval required to do work iv. In addition to any development consent, approval is also required from Council for any work that: Is external to the development site, Impacts on land that is under the ownership, care and control of Council, such as foot paths, public reserves, drainage easements and drainage reserves, Impacts on Council's roads and related infrastructure, street trees and stormwater system. Such works could include kerb and gutter reconstruction, footpath reconstruction, vehicular crossing construction, trunk drainage installation and drainage pit construction. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-2 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER v. These works must be constructed in accordance with Council’s specifications and requirements. Work Permit (WP) vii. A work permit issued by Council, is required in accordance with Section 138 of the Roads Act 1993 and Section 68 of the Local Government Act 1993, or any works carried out by a developer on Council’s road reserve, within public land, or on Council’s assets including stormwater pipes and pits. viii. The applicant must apply to Council for a WP to be assessed subject to appropriate fees and charges. It is very important for applicants to apply for a WP as early as possible at the construction certificate stage to seek Council’s approval. ix. Where construction of new Council infrastructure, excavation for vehicular crossing and/or works for utilities including stormwater, water, sewer, gas, electricity, communication network cables, occurs adjacent to or within the road reserve, the work must be carried out in accordance with an approved Council WP. x. Utility installations must be carried out in accordance with, and to the satisfaction of, the relevant utility authorisation. The restoration of Council’s assets must be carried out to Council’s satisfaction following installation: Note: for any other works in the road reserve not related to a development, a WP for road openings or vehicular crossing must be obtained subject to appropriate fees and charges. Traffic Management Plan (TMP) and Traffic Control Plan (TCP) xi. Submit a TMP for any development where the site work will interrupt or have a significant impact on road and footway activities on a regular basis – the plan is to assess the impacts on traffic flow, cyclists, pedestrians, local residents, businesses, parking stations, schools, hospitals, public transport and emergency services: Note: The TMP is often included in a construction management plan, which provides details of how the construction activities related to a development will integrate with the daily operation of the road network. xii. Submit a TMP and/or certified TCP for any work within Council road reserve, and involving temporary partial road closure and/or closure of the footway: Note: The TCP is a plan that is intended to ensure the safety of road users and road workers at the work zone area. The TCP specifies the signs, devices and illumination to be used to warn, instruct and guide road users in the safe negotiation of work sites on road reserves and provide a safe working environment. xv. The TCP must be prepared in accordance with the state road authority’s guidelines “Traffic Control at Work Sites” and AS 1742.3 “Traffic Control Devices for Works on Roads”, including proposed timelines of the above matters. Road Occupation Licence (ROL) xiii. An application for lane closure and/or partial road closure on regional roads, RTA State Roads, and within 100m of a traffic facility, must be submitted to the state roads authority for issue of a (ROL) traffic facilities include traffic signals, roundabouts, speed humps, kerb islands, refuge islands, pedestrian signals, pedestrian crossings. Submit documents xiv. Submit a copy of TMP, TCP and any ROL prior to issue of a WP. 6.4.4 Off-site engineering details Footpath and vehicular crossing levels i. It is a pre-lodgement requirement that street alignment levels be obtained from Council prior to lodgement of the DA. See Table 6.4.11 and Section 6.5.2 (ii). ii. These levels must be incorporated into the design of the proposed footpath/vehicular crossing for the site. Site levels at the street boundary must be compatible with footpath and driveway levels. iii. The consideration of the street alignment levels is particularly important at the initial design stage as the level at the street alignment could determine critical design elements in relation to floor levels, internal pavements, car parks, basement levels, landscaping and stormwater drainage systems. iv. A fee is payable for street alignment levels as per Council’s Annual Fees and Charges. Road, kerb and gutter and footpath design v. The development may be conditioned to include the reconstruction of the kerb and gutter, and or footpath paving along the frontage of the site. vi. The applicant shall arrange for a practicing Civil Engineer with suitable experience to prepare the design in accordance with this document, NatSpec and Council’s Standard Drawings and specifications. See appendices for Council’s standard construction details. vii. The design shall be drawn to a scale of either 1:100 or 1:200 scale drawing on A1 sheets. viii. Long-sections of works shall be drawn at a 10x exaggerated vertical scale. ix. The design shall indicate the following: Existing and proposed road, CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-2 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER x. Existing and proposed kerb and gutter, Existing and proposed footpath and boundary levels, Location of all services, Location of existing and proposed drainage structures. The design shall be submitted to and approved by Council prior to the release of the construction certificate. xi. The construction shall be undertaken in accordance with NatSpec and Council specification and the work certified by a qualified engineer on completion. A Works As Executed Plan shall be provided to Council. Failure to certify the works or provide a Works As Executed Plan may prevent progress of the application. Street trees xii. Street trees represent an important asset of the street landscape and consideration must be given to the location of the street tree in relation to the proposed layout of the development - to ensure this it is a pre-lodgement requirement that a tree report be obtained from Council prior to the lodgement of the DA. See Table 6.4.1 and 6.4.2 (iii). This report will provide information as to the likely conditions that would be placed on the street tree, both during and post construction. xiii. Council has a Street Tree Management Plan, which may require certain species to be retained, and accordingly proposed developments must incorporate these protected species into the final design. The report will specify clearances of proposed vehicular crossings and footpaths to existing street trees. These clearances shall be complied with in the proposed design of the development. Council’s requirements in relation to the street tree may affect the internal design of the development as a whole, from layout, accesses and landscaping. xiv. The consideration of this information in the initial design process could prevent expensive redesign should the street trees not be considered at the early stages of the development process. During both construction and on completion of the development every effort must be made to protect the street trees from damage, by the installation of suitable protection during construction and to adherence to appropriate clearances of the final development. xv. Removal of street trees will only be approved in accordance with Councils Tree Preservation Order. Applicants may be required to replace any removed trees with other suitable tree(s), as approved. All costs being borne by the applicants for the replacement of any removed trees. Stormwater drainage xvi. A development may require the installation of street trunk drainage where the conditions set for alternative stormwater disposal in Section 6.4.11 Disposal of Property Runoff cannot be met. xvii. Extension of the Council trunk drainage system will be required where the proposed drainage system from the development cannot connect to the kerb and gutter within 15m of the site or the discharge is in excess of 55 l/s. In this case the applicant will be required to extend the Council system to the site. The applicant shall arrange for a practicing Civil Engineer with suitable experience to prepare the drainage design in accordance with this document and AS/NZS 3500.3 Plumbing and Drainage – Part 3. xviii. The drainage plan shall be submitted to Council for approval and shall provide the following information. Plan at 1:200, Long-section at 1:200H, 1:20V, Plan and long-section of all services to be crossed, including proposed drainage line, Flow-rates and grades of all pipes, Invert, natural surface level at a minimum of 10m intervals. xix. The construction works shall be undertaken in accordance with NatSpec and Council specifications and the work certified by a qualified engineer on completion. 6.4.5 i. ii. On-site engineering requirements The on-site engineering requirements for development may involve several engineering disciplines, including: Drainage/Hydraulic Engineering, Traffic/Transport Engineering. Design development to utilise and integrate with the existing infrastructure and minimise any potential adverse effects on community assets: iii. When designing take account of the following: Road and footpath levels, Location of proposed vehicular access with respect to drainage structures, traffic facilities, street trees, signs, power poles and other infrastructure, Existing drainage infrastructure, Overland flow path of stormwater, Traffic requirements development. of the CANTERBURY DEVELOPMENT CONTROL PLAN 2012 proposed P6.4-3 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Traffic Generation Report (TGR) iv. For any development where the site work will interrupt or have a significant impact on road and footway activities on a regular basis, submit a Traffic Generation Report to Council. See Table 6.4.1 to determine if a TGR is required for the proposed development. v. Undertake the TGR in accordance with the state roads authority and best practice guidelines with an objective to assess the impacts the proposed development will have on traffic flow, cyclists, pedestrians, and local residents, businesses, parking facilities, schools, hospitals, public transport and emergency services. Traffic Manoeuvrability Report (TMR) vi. In any development vehicles may be required to execute specific turning movements to access garages, car spaces and visitor car parks – a report may be required describing and illustrating how the site is accessed from the road reserve as well as how specific locations within the site are also accessed. See Table 6.4.1 to determine if a TMR is required for the proposed development. vii. Undertake the TMR in accordance with Australian Standard AS 2890.1, to illustrate the turning paths into and within the development through the use of AustROADS documentation or computer generated turning paths (using software packages such as AutoTurn). Adopt design vehicles that are appropriate for the proposed development. viii. Unless stipulated otherwise in AS 2890.1, for domestic circumstances, adopt the B85 vehicle for assessment purposes. Notwithstanding, the AS shall specify the type of vehicle to be considered for respective development types. ix. For commercial and industrial development the size of the vehicle illustrated for accessing the site will be taken as the maximum proposed for the site, and may be conditioned as such. However, the size of vehicles permitted may be reduced through the approval process. Vehicular access, internal footpath and driveway levels x. Undertake the design of the proposed vehicular access and internal pavements must with consideration to the street alignment levels. xi. As described in Table 6.4.1 and section 6.4.2 (ii), the development application can’t be lodged without the prior application, payment and adoption of the street alignment levels - having obtained the street alignment levels from Council evidence must be provided on the plans that these levels have be adopted in the design of the development, including designs of the internal pavement, car parks, landscaping and stormwater drainage. xii. Show the proposed level of internal pavements on development application plans, indicating direction of fall to establish appropriate surface drainage and overland flow paths - the design and construction of the internal pavements shall be in accordance with NatSpec and the relevant Australian Standards. xiii. An application fee is applicable for the design, preparation of specifications, and for the inspections of the proposed vehicular crossing and if approved, the applicant must provide a concrete vehicular crossing across the full width of Council’s footway. xiv. Construct the vehicular crossing in accordance with plans, design levels and specifications issued by Council. Where a basement is proposed as part of the development, adequate manoeuvring area must be provided to allow vehicles exiting the site in a forward direction, reversing onto public roads is prohibited. 6.4.6 On-site engineering details Location and width of vehicular access i. The location and width of vehicular crossings is important in ensuring minimal conflict with existing infrastructure: ii. Where the proposed vehicular crossing in the road reserve is in conflict with existing utilities and civil infrastructure, any cost incurred in adjusting /removing/reinstating such structures will be borne by the applicant. iii. Position vehicular crossings so as to avoid conflict with existing street trees. The Tree Report will specify the required clearance from the tree to proposed vehicular crossings - (a separate application for tree removal will be required for Council’s assessment where the location of the proposed vehicular crossing will affect the existing trees. iv. Vehicular crossings, which do not comply with RMS guidelines, or those located in positions that require special assessment/consideration, will need specific approval from Council’s Traffic Committee. v. When determining the position and width of vehicular crossings, consider adequate sight distances for vehicles exiting driveways - in particular, provide clear sight lines to ensure adequate visibility between vehicles on the driveway and pedestrians within the property and on the footpath – (sight line information is available section 6.8 Vehicle access and car parking). CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-4 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Dual driveway access vi. Do not propose a second driveway or horseshoe driveway, as Council’s current policy will not support such a proposal unless: The proposal will not affect on-street parking demand, The area of paving within the property is minimised, There is sufficient landscaping being provided to compensate for the additional paved area, The proposal has merit on road safety grounds. Internal Driveway Profile vii. Design the vehicular driveway profile within private property to prevent vehicles from scraping and so that it will satisfy the requirements set out in AS 2890.1 with the following grade requirements: The maximum allowable grade is 25%, Transition grades for changes in grade in excess of 12.5%, Driveways with a grade in excess of 15% are constructed with a non-slip finish. viii. Provide a long-section of basement driveway accesses, drawn to the current scale described in AS 2890.1. Draw the long-section from a minimum of 3m inside the basement, along the driveway to the road shoulder, approximately 2.5m from the lip of the gutter. It is the designer’s responsibility to confirm access along the most difficult route into the basement. The long-section shall be confirmed using the AS 2890 B85 templates. This plan shall be provided at DA submission for Council approval. ix. Consider adequate sight distances for vehicles exiting driveways and provide clear sight lines. Note: The consideration of basement levels is a critical assessment point for a development. Non-compliance with this element could have adverse effects on the entire design process. xii. A practicing civil engineer with suitable experience is to prepare the drainage plan in accordance with the CDCP and AS/NZS 3500.3 Plumbing and Drainage – Part 3. xiii. Involve the drainage engineer in the site layout and initial concept design and integrate the drainage system with the design of the development (to avoid costly problems that may arise later on). xiv. Design the drainage system to collect and convey stormwater runoff from the site and into receiving systems with minimal nuisance, danger or damage to the site, adjoining properties or Council’s property. xv. Address all the issues outlined in Table 6.4.2, the Drainage Requirement checklist below, and the OSD design checklist shown in Appendix A. Note: In particular, sites that fall to the rear may have difficulty in discharging stormwater runoff to the street frontage the applicant will be required to negotiate a drainage easement through a neighbouring property to discharge their stormwater or use the discharge alternatives in section 6.4.8. Note: The designer is responsible for preparing adequate hydraulic plans to address any issues that may emerge with a particular site, as the DCP is not intended to cover all possible situations. 6.4.7 Drainage Stormwater drainage requirements i. Highlight any potential overland flow path throughout the development and the necessary measures taken to minimize the impact on the development, adjoining properties, Council’s stormwater system and any other authority’s drainage system. ii. Stormwater system is to be gravity fed, however; there are some provisions made allowing alternative methods to be used for single dwellings, only where gravity system can not be provided (See Table 6.4.2 in Appendix H). Stormwater drainage iii. Generally, approval of stormwater system to drain against the natural fall of the land will not be granted. Any proposed development on a site that slopes away from the street frontage will require a drainage easement through downstream properties, if one does not exist already. It is the applicant’s responsibility to confirm that a drainage easement can be obtained prior to lodging the development application. xi. Provide a detailed stormwater drainage plan (required with most development such as all new development, additions and alterations) to illustrate how stormwater runoff from the site will be managed. Note: In some cases where the development is proposed on unusual and difficult sites for drainage, the use of combination drainage methods might be considered, however; it is up to the applicant to present the necessary details and calculations to demonstrate that the proposed system is the most feasible one for Council’s consideration. Internal Trees ix Removal of trees will only be approved in accordance with Councils Tree Preservation Order (refer to Part 6.7). xi. Applicants may be required to replace any removed trees with other suitable tree(s). CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-5 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Drainage plan requirements iv. Provide a block plan of the property drawn to a scale of 1:100 showing the storm water service. Reduced scale plots of plans may be accepted (that is, A1 size reduced to A3) where the plans are produced using AUTOCAD and are legible at that scale: v. Show the following clearly on the stormwater plans: North point Street and site details Contours s of site and road to AHD Existing services within the site and in front of the site on the nature strip Roof plan of proposed and existing buildings Downpipes location and connection into the system Pipe sizes and grades indicated along all pipes All pit sizes, grate levels, invert levels, inlet & outlet pipe levels indicated adjacent to all proposed and existing pits Levels of all retaining walls throughout the site Finished floor levels of both existing and proposed Finished surface levels of courtyards, driveways pathways and detention basin 1.2 m high pool type fence barrier around detention basin where the ponding depths are greater than or equal to 500mm Detailed cross-section through the detention basin and the control pit Overland flow paths clearly indicated The detention basin clearly defined Permissible site discharge PSD Site Storage requirement SSR Detailed working volume calculations of the SSR Detailed orifice diameter calculation. 6.4.8 Property drainage Roof drainage i. Roof drainage systems are designed in respect to potential monetary loss, property damage (including contents of buildings) and injury to persons due to overtopping. The design of roof drainage system shall be carried out in accordance with the Australian Standard AS/NZS 3500.3:2003. Surface runoff ii. All surface runoff, regardless of type of surface (pervious - grassed and landscaped - or impervious - concreted or paved) must be appropriately collected into suitable drainage components (pits, grated drains and floor waste) and connected into a piped network. The design of surface drainage systems shall be in accordance with AS/NZS 3500.3. Piped drainage system iii. Incorporate a piped drainage system and an OSD storage system where applicable. The provision of OSD will be a major component of the stormwater system design, and accordingly, the design of the OSD system and Council's requirements for that design are detailed in Section 6.4.10. iv. Design the piped drainage system to cater for 1 in 20 year ARI storm rainfalls based on the IntensityFrequency-Duration tables and coefficients provided in Appendix B. v. In addition to the 20 year ARI event, design the piped drainage system to ensure that any potential overflows generated from system blockage, or overloads in storm events with an ARI of 100 years, do not present a hazard to people or cause significant damage to property (surface runoff or overland flow paths must be indicated on the design plans). vi. Pipes that are laid within a public roadway, or which drain public areas such as a road or public park, are to have a minimum diameter of 375mm. vii. Piped systems shall meet the minimum pipe diameter, cover and gradient criteria specified in AS/NZS 3500.3:2003. Such systems shall be arranged so that any potential overflows will not pond against or enter into buildings. Basement pump system viii. Pump out systems for basements are permitted 2 when the system is limited to the driveway– 50m maximum allowable driveway area draining to a pump system: Ix. Design any basement pump system in accordance with AS/NZS 3500.3 and as follows: Grade the basement car parking area to fall to the sump and pump system, Limit the contributing catchment area to the pump out system to the basement access ramps only - all other surface flows are diverted away from the basement, Design the two pumps to work in tandem to ensure that both pumps receive equal usage and neither pump remains continuously idle, Design the pump out pit to have sufficient volume for a 100 year ARI rainfall event for two hours duration so that a minimum volume of water can be retained in the sump when the pumps are in the off position, CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-6 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER x. 3 could not be created. (see Table 6.4.1) Applicants must provide relevant documentation to demonstrate to Council why an alternative drainage method (such as a pump system) should be considered. Minimum pump-out pit size 3m . Submit engineering details and manufacturers specifications for the pumps, switching system and sump for approval prior to the issuing of the construction certificate. xii. Indicate clearly the sequence and order of operation of the system, and associated alarm and light signal warning, on the plans. Multiple unit dwellings v. Sub-soil drainage system xiii. Design and construct subsoil drainage systems in accordance with Section 6 in AS/NZS 3500.3. xiv. Do not connect subsoil drains directly to kerb and gutter - they must first be connected to a pit – connect to a gravity fed system stormwater is disposed of in a manner that will not have an adverse impact upon adjacent properties. xv. Where proposed development will have substructures (such as a basement) in areas adjacent to a watercourse, or where a high water table is anticipated, tank/seal the substructure from underground water. 6.4.9 On-site detention (OSD) requirements by type of development Single dwelling and dual occupancy development i. ii. iii. Provide OSD with all detached dwellings (including alterations and additions), and all dual occupancies, regardless of whether the site slopes toward the street of away from it, where the proposed impervious area is greater than or equal to 70% of the total site area (impervious area includes roof, concrete driveways, concrete paths, paved and hard surface areas and swimming pools). OSD is not required when the proposed impervious area is less than 70% of the site; in this case the drainage system can be designed, without OSD, using gravity fed pipes and a silt arrestor pit, before the stormwater is discharged into the receiving system. Submit an OSD checklist (Appendix A) with the development application. Note: Driveways constructed with gravel, grasscrete or pervious pavers are considered to be impervious for drainage calculation purposes. Courtyards and pathways paved with pervious pavers will be considered to be 25% impervious. Provide OSD with all development consisting of multiple dwellings (where three units or more are proposed), regardless of the impervious area before and after the development, and regardless of whether the site falls toward or to the street. vi. Create a drainage easement if one does not exist already, through respective downstream properties where the site falls away from the street, only gravity fed system will be supported. Commercial and industrial vii. Provide OSD with all new commercial development and other non-residential development and sporting facilities, such as institutes, tennis courts net ball courts and car parks/major driveways, regardless of the existing impervious area on site and regardless of the slope of the site: viii. Create a drainage easement if one does not exist already, through respective downstream properties - where the site falls away from the street, only gravity fed system will be supported. ix. Where additions/alteration are proposed on sites with an existing impervious area equal to 70% or more, a maximum of 5% of additional impervious area will be permitted before OSD is required (hence the maximum impervious area in this instance is 75%): x. Collect stormwater from roofed and large paved areas within the property in a system of gutters, pits, grated drains and pipe lines, and then discharged into the street gutter or stormwater system approved by Council: xi. Where discharge of stormwater to the street gutter, common drainage lines, other authority’s drainage system or Council stormwater system is not possible, and an easement through downstream property could not be established by way of negotiation, Council may consider the use of alternative drainage methods such as charged line or absorption system subject to certain conditions (Refer to 6.4.15). iv. Where a dual occupancy development is proposed on a site sloping away from the street frontage, and a gravity pipe system to the street can’t be used, provide a drainage easement through downstream property. There are no provisions for alternative drainage methods similar to the single dwelling provisions when a drainage easement CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-7 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER 6.4.10 On-site detention system details Depth of ponding not to exceed 150mm under design conditions, Transverse paving slopes within storages not less than 1:50, Where the storage is located in commonly used areas where ponding would cause inconvenience, provide part of the storage required in an area that will not cause a nuisance. On-site detention systems have four main elements Temporary storage This may consist of an open surface area above ground to allow ponding of stormwater or a closed tank installed underground. It is designed to temporarily contain the excess volume of stormwater that is unable to pass through the discharge control during intense rainfall conditions. Discharge control pit This is the means of limiting the flow from the site. This may consist of a limited orifice (design outlet diameter) or other means of reducing the flow of stormwater from the site. iii. Use the following criteria for OSD systems located in underground tanks: Fix the hydraulic control for the storage, usually an orifice plate on an outlet pipe, firmly in place to prevent removal or tampering, Grade floor of tanks at a minimum slope of 1:140, towards the outlet, to minimise ponding and depositing of debris, Provide an inspection/access opening above the location of the outlet with dimensions at least 600mm x 600mm or 600mm Ø for storages up to 800mm deep; and 600mm x 900mm for deeper storages. Ensure there will be no impediment to the removal of debris through this opening and inspection will be possible without residents or owners having to remove heavy access covers, When storages are not sufficiently deep to work in (less than 1.5m), provide access at intervals of approximately 10m to allow the system to be flushed to the storage outlet, and adequate access at the outlet, Provide a sump (with the base level set below that of the main storage) at the outlet point to collect debris. Where a discharge control pit is included in the storage, this also contains a sump set at a minimum of 1.5 times the diameter of the orifice of the outlet below the centre of the orifice. Equip sumps with adequate weepholes to drain out to the surrounding soil - they shall be founded on a compacted granular base, Underground storage tanks must be constructed of concrete or rendered brickwork or other approved materials in accordance with AS/NZS 3500.3 - VERSITANK MODUALS will not be permitted, In addition to the required design storage a 20% buffer storage for pump out OSD is to be provided. Overflow structure (Weir) An overflow weir or emergency outlet is to be provided from the temporary storage basin, it is designed to cater for extreme storm events (1 in 100 year event) and when system failure occurs, it should safely direct overflows away from the site or adjoining properties and into the street system. Below ground systems Maintenance Regular maintenance of on-site detention system is required in order to keep them in a functioning manner. Maintenance includes clearing of accumulated debris from screens and removal of sediment from the base of the pit or tank. It is the responsibility of the owner of the property to carry out periodic maintenance. Aboveground systems i. ii. Use the following criteria in for OSD systems in landscaped areas: Minimum slope for surfaces draining to an outlet 1:5 (2%) and absolute minimum slope 1:100 (1%), Maximum ponding depth conditions is 300mm, Increase required storage volumes in landscape areas by 20% to allow for vegetation growth, Provide subsoil drains around outlets to prevent the ground from becoming saturated during prolonged wet weather, Minimum freeboard required above the top water level is 300 mm for a habitable room and 100mm for a garage, Brick and mortar is the only material to used where retaining walls are used along the perimeter of the basin. under design Use the following criteria for OSD systems Indriveway and car park storages: All systems iv. In addition to the above use the following criteria for all OSD systems: CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-8 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Provide for the harmless escape of overflows in the event that an outlet becomes blocked and the storage is completely filled. Any ponding of water resulting from a blockage shall occur at a visible location, so that the fault can be noticed and corrected, Permissible site discharge (PSD) Ponding and overflow levels shall not be less than 300mm below any habitable floor levels of building and not less than 150mm below non-habitable floor level. x. Note: Ensuring that peak flow-rates, at any point within the receiving downstream drainage system, do not increase as a result of the development, during storms, is achieved by providing sufficient storage (OSD) on sites. Location v. Locate the OSD system at the lowest point of the site, with all paved areas and pipes draining into it - the use of driveways, parking areas and/or landscaped areas for an above ground OSD system is encouraged. vi. Do not position an OSD system in overland flow paths that convey the local catchment flows through the site - typically a drainage easement through a site would attract overland flow path for the local catchment. ix. The permissible site discharge (PSD) is limited to 150 litres per second per hectare for a 1 in 10 ARI year storm event. Site storage requirements (SSR) A stage-storage routing model is the preferred method of calculating the required storage volume. xi. Methods that assume a constant discharge, such as the Mass Curve Analysis, require a factor to be applied to the constant discharge to determine the detention volumes - the adjustment factor for aboveground storage is 0.75 and for belowground storage is 0.6. xii. Ensure a minimum of 75% of the entire site area will drain through the storage area and that all the roof area, and as much of the paved area as possible, will drain through the detention system. xiii. Incorporate provision for on-site storage resulting from a storm with an ARI of: vii. Locate storages in common areas in multiple unit development. Design methodology Note: The main and most important factor in determining the magnitude and hydraulic capacity for any stormwater system is design flow; this is derived from rainfall statistics using a rainfall-runoff model (Appendix B) for rainfall Intensity in the Canterbury area. 6.4.11 Q = C I A /3600 Where: Q = design flow of stormwater (L/s) C = runoff coefficient (see Appendix 7.2) I = design rainfall intensity (mm/h, see Appendix A) 2 A = catchment area (m ) Disposal of runoff from property i. Discharge stormwater runoff to kerb and gutter, street drainage, pipe in an easement, pipe in an inter-allotment drainage system, Transport Roads and Maritime Services system and Sydney Water channel or river. ii. Dispose stormwater runoff by an in ground gravity system. Elevated pipelines are not favoured although pipelines contained within buildings or low-level garden beds may be considered. Calculating peak flow rates viii. Use Council’s standard method below for relatively 2 small catchments (< 7500m ), and for larger sites use the Rational Formula from Australian/New Zealand Standard Plumbing and Drainage Part 3: Stormwater Drainage AS/NZS 3500: 10 years where overland flow paths are not through private property. Design and provide a weir to direct the 100 year discharge to the street drainage system, 100 years where overland paths are through private property and/or known flooding problems occur. iii. Do not fill the land excessively (that is, ≥ 150mm), in order to get an in ground pipeline to drain to the street, rather than obtain an easement for the disposal of stormwater (Refer Appendix C for methods that are satisfactory to drain various types of development. Connection to kerb and gutter iv. Discharge stormwater runoff directly into the kerb and gutter at a point no greater than 15m downstream from the boundary of the developed lot. v. Maximum allowable single point discharge to Council's kerb and gutter is 55 l/sec, or the PSD, whichever is the lesser. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-9 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER vi. If more than one outlet is required, separate them by a minimum of 500mm, however; the total discharge shall remain at 55 l/s or the PSD. vii. Stormwater conduits laid in the footpath area should be sewer grade PVC or galvanised steel (i.e. RHS) and not greater than 100mm in height - the pipe or conduit is to discharge into the kerb and gutter at an angle of 45 degrees to the flow in the gutter. Control of seepage viii. Where increased seepage is anticipated, or becomes evident as a result of site or building works, and this seepage is likely to have an adverse impact on adjoining properties or Council managed land, adequate subsoil drainage is to be provided and connected to the piped drainage system. Subsoil drains are not to be installed below the water table. Should the water table be encountered within the depth of the excavation the structure is to be tanked and sealed. Connection to Council’s street pipe system or interallotment drainage system ix. Make the connection into the top third of Council's pipe and at an angle of 45 degrees to the flow in the pipe – no pipe protrusion is permitted into Council's pipeline. x. All work is to be carried out to the satisfaction of Council - products used for the joints shall be in accordance with AS/NZS3500.3: 2003. xv. Council will permit connection directly to its stormwater pit or pipe providing the outlet invert level from the property is at or above the top of kerb level at the connection point. xvi. Outlet pipes less than Ø150mm can be connected directly to a council pipe. Outlet pipes Ø225mm or greater will require the construction of a standard council pit at the point of connection: Charged line xvii. Charged lines will be only be permitted for proposed additions/alterations, outbuildings and single dwellings. xviii. For a new detached dwelling, where rainwater tanks are included, the pipes are completely sealed, from the tank overflow to the point of discharge. Note: Typically a charged system will only work for the roof of buildings. xix. Use the following criteria for charged lines: Will only be permitted if there are no drainage problems downstream in the catchment where the drainage is being directed. A full hydraulic analysis of the system including a hydraulic grade line and calculations MUST be submitted with the Development Application. Adequate height within the system must be provided (minimum of 0.9 m) between the roof gutter and the higher of the top of the kerb OR the overflow level from the rainwater tank. All gutters and pipes in the system MUST be designed for a 1 in 50 year ARI storm event (1 in 100 years for box gutters) without overflowing. All pipes and downpipes are to be sealed to a minimum of 0.5 m above the top water level within the system. The system shall be pressure tested prior to backfilling. There must be a gravity flow across the footpath from an isolating pit within the property boundary into the kerb. If the footpath falls towards the property; then the pipeline must remain sealed to the kerb outlet, with a sealed cleaning eye installed within the property boundary. All services within the footpath must be identified and located prior to submitting the plans and the details must be shown on the plans. A flash point must be provided at the lowest point of the system within an inspection pit (350 x 350 min) with a sump for cleaning. xi. Arrange for Council to inspect the connection prior to the sealing of the joint. Connection to Sydney Water Corporation drainage system xii. Provide documentation that Sydney Water Corporation has approved the proposed connection into the channel before Council approves the hydraulic details. Disposal to natural watercourse xiii. Provide documentation that the relevant authority has approved the proposed connection into the watercourse before Council approves the hydraulic details. Note: Rivers within the city area are under the control of the Department of the Sydney Water Corporation. The applicant will have to identify the responsible authority and satisfy the requirements of the authority. Submerged outlet xiv. For drainage proposals that require connection directly to Council’s stormwater pit or drainage pipe, the designer is to consider the effects of a drowned outlet. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-10 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER There must be a minimum of 1 m long pipe from the last downpipe to the inspection pit. The connection to the pit is to have a sealed screw cap to allow for periodic cleaning, the cap shall have a 5 mm dribble hole to allow for a slow release of trapped water. The pit shall be appropriately located within the property so that runoff or surcharge during maintenance will not affect downstream or adjoining properties (see Figure 1). Gutter guards MUST be installed on all gutters to minimize debris from entering the system. ii. Use the following criteria in the design and construction of an absorption system: The absorption pit is to be designed to cater for all surface runoff generated from the impervious areas for the 1 in 50 year ARI storm event, A detailed design and supporting calculations, prepared by suitably qualified and experienced engineer must be submitted with the development application, A geotechnical report in support of the above design and an assessment of the infiltration (absorption rate) of the soil profile must be submitted with the development application, The absorption rate in litres/square metre/second must be determined with a recognised falling head or constant head test. The test shall be repeated until there is less than 5% difference in results. Full details of all test results are to be submitted with the development application. At least one test hole at each proposed pit location is to be drilled to a minimum depth of 1.5 m below surface level, When calculating storage volume allow for 20% voids in the base aggregate. The standard pipes network shall not be considered as storage volume, The absorption system shall be installed as far as practicable from downstream property boundaries (minimum 5.0m) and a minimum 3.0 m from any buildings. The system should not be placed under any paved surfaces and must be at least 1.0m from pavements subject to vehicular traffic, A silt arrestor pit shall be constructed immediately upstream of the underground absorption system, On-site absorption will not permitted in areas where the nominal absorption rate is less than 2 0.01 l/m /sec and there is clearly identified soil salinity problem. Pump-out system xx. Council may consider the use of pump-out system as a last option, for sites slopping away from the street, in the event that a drainage easement can’t be created or the use of an alternative drainage method (such as charged line or absorption system) is determined to be unachievable: xxi. Council’s discretionary approval of a pump out system is based on the following criteria: The maximum pump rate must be limited to PSD 150 litres/second/hectare, Dual submersible pumps must be provided with all connections and configuration complying with Section 9 of AS/NZS 3500.3, The underground storage tanks must be constructed using pre-cast or cast in situ reinforced concrete subject to structural engineers design, The required storage volume shall be designed entirely underground, The underground pump system must be located at the lowest part of the site, Design storage volumes for the pump system must comply with Table 6.4.2, A positive covenant must be created and registered over the pump system to ensure long-term maintenance. 6.4.12 i. Applicants must provide easement documentation and relevant information regarding alternative drainage methods to demonstrate why these methods can’t be installed, Absorption systems Absorption system may be permitted for paved areas (such as driveway, pathway and hard surfaces) associated with additions/alterations, outbuildings and single dwellings only. Note: Most of Canterbury consists of clay subsoil and the absorption (rubble pit) system is generally ineffective. Therefore, it is the least preferred drainage method. Methods of sizing absorption pits viii. Apply a reduction factor to the Nominal Absorption Rate (ARN) determined in the above geotechnical report to cater for clogging of filters, variability of soils and likelihood of multiple storms in accordance with the following. Nominal Absorption Rate (ARN) Reduction Factor (FR) 0.1 ≥ ARN ≤ 1.0 0.75 ARN < 0.1 0.50 Then ARD = ARN * FR where ARD = design absorption rate. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-11 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Storage method with average rainfall intensity Inlet pit locations iv. Determine a preliminary pit dimension and proceed through a process of trial and error: iii. Position inlet pits, or grated drains, systematically at locations within the developed site to capture the majority of surface runoffs, while also fitting neatly into the layout of the site stormwater system. Base area (BA) = width * length v. Calculate the rate of discharge to the sand using ARD * BA in litres/second, then calculate the required storage for a number of storms by calculating the difference between the generated runoff volumes and the absorption volumes. Compare the required storage to the available storage in the proposed system. Where the available storage is greater than the required storage for all time steps the proposed system is feasible. Note: It is suggested that the designer create a spreadsheet so multiple sizes and configurations can be readily tested (refer to Appendix F). 6.4.13 Rainwater tanks Rainwater tanks and the use of stored rainwater for non-potable uses (such as watering gardens, washing, flushing of toilets) is encouraged, and a minimum size of rainwater tank is required for all new residential development as part of BASIX certificate requirements. i. Where OSD, or absorption, are part of the proposed stormwater system, up to 25% of the required volume for the above systems can be offset into a rainwater tank. Note. If water in rainwater tanks is intended for human consumption, the tank should be maintained to ensure that the water is fit for human consumption-see the Rainwater Tanks brochure produced by NSW Health and the publication titled Guidance on the use of rainwater tanks, Water Series No 3, 1998, published by the National Environmental Health Forum. For more information about rainwater tanks and other water-wise options, visit www.sydneywater.com.au 6.4.14 Surface pits Depth (mm) Minimum Pit Size (mm) < 300 300 x 300 300 - 600 450 x 450 600 - 1200 900 x 600 > 1200 900 x 900 iv. Size on-grade pits, or grated drains that are located on sloping surfaces, or in channels or gutters, to intercept a large proportion of the flow - place so that any bypass flows, under minor storm event conditions, will not cause a nuisance and so that widths of such concentrated flow is negotiable by pedestrians. v. Inlet pits in locations subject to potential mosquito borne disease (dengue fever) shall be designed without a sump and be self-draining. Note: Care should be taken by positioning and specifying details (e.g. type of product) of grated pits in areas subject to pedestrian or vehicular traffic to avoid possible damage to pits and danger to pedestrians. Note: Site stormwater drains should be laid in straight lines: To avoid conflict with other services, and To minimize overall length and number of changes in direction. Silt arrestor pits vi. Install an approved silt arrestor pit at the lowest part of any developed site to eliminate contamination (generally silt, oil, or both) from stormwater runoff prior to discharge into the stormwater drainage network - in the case of car wash bays, the silt arrestor shall be also designed to retain oil. vii. Locate the arrestor within the subject property and install upstream of the discharge point (connection to kerb and gutter or Council pipeline). viii. Wherever practicable, grade the area adjacent to a silt arrestor so as to drain to the silt arrestor. ix. A silt arrestor may receive the discharge from an upstream pit or sump, which has been installed to receive surface water only, provided that the silt arrestor is of sufficient capacity to receive the additional discharge. Table 6.4.5 - Minimum internal dimensions of surface inlet pit Design of silt arrestor pit i. Construct all surface pits in accordance with AS/NZS 3500.3 6.5.4 with the finished surface level of the grates consistent with the surrounding levels - the grates of any stormwater component must not protrude above ground level. x. ii. Provide step irons in pits deeper than 1200mm. Determine the capacity of the arrestor from the estimated peak discharge to the arrestor. Design and dimension rectangular or square silt arrestors in accordance with the following table. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-12 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER 200mm below the invert level of the downstream pipe – provide minimum of two 50mm weep holes at the base of the sump. Nominal size of inlet pipe (mm) Minimum nominal size of outer pipe (mm) Width (mm) Depth from invert of outlet pipe to base of pit (mm) 150 100 600 300 600 150 150 600 300 1000 225 225 700 300 1000 300 300 800 300 1000 450 450 1000 300 1200 600 600 1000 300 1500 Length (mm) Table 6.4.6: Minimum internal dimension for silt arrestor pit xi. Determine the inlet capacity of on grade and sag inlet pits using equations given in Chapter 14 of Australian Rainfall & Runoff (1987) - the arrestor shall be constructed of concrete or other approved materials. xii. Locate the invert of any inlet pipe at least 50mm above the nominal water level in the arrestor subject to normal flow conditions. xx. Construct the control pit on an aggregate base wrapped in geotextile fabric. xxi. Construct all pits in reinforced concrete - bricks cement rendered, or precast concrete and plastic pits will not be permitted. xxii. Provide large paved areas and driveways falling towards Council’s footpath with a heavy duty grated drain across the whole driveway width, the outlet from the grated drain shall be connected to the internal drainage system before being discharged into the receiving system. 6.4.15 i. Submit details of approval of the drainage easement with the development application to demonstrate the consent of respective downstream owners. Note: A genuine attempt to obtain an easement must include monetary offer of compensation, based on a valuation report prepared by a registered land valuer. ii. If the required drainage easement has not been obtained provide the following documentation to demonstrate all avenues have been exhausted: A land valuation report prepared by a registered land valuer, with an estimate of the land value of the easement (excluding construction/installation cost), A letter of request from the applicant to owners of all possible downstream properties, requesting permission to create a private drainage easement through their property – including a concept plan illustrating the proposed location of the drainage easement, an offer of compensation (as estimated in the valuation report) and a commitment to pay all relevant expenses and reinstate disturbed areas, A signed letter of correspondence from the downstream property owners either accepting or rejecting the offer. xiii. Place the outlet pipe at a height of not less than 300mm above the pit base, depending on the nominal size of the outlet pipe. xiv. Except where otherwise permitted, provide a removable cover for the silt arrestor – use heavyduty cast iron or fabricated galvanised steel grates on all surface inlet pits in areas with vehicular traffic. xv. Construct covers with galvanised steel, cast iron or other approved material that is capable of withstanding any load likely to be imposed on the cover - perforated with wholes of not less than 15 mm diameter and spaced at 40mm centres, or use open bar grill design, or another approved design. xvi. Use appropriate cover designs and products where pits are located in high pedestrian traffic areas, or in playground areas. xvii. Provide weep-holes at the base of silt arrestor pit either 4 x 20mm diameter hole or 1 x 40mm diameter hole. xviii. Cut all inlet and outlet pipes entering or exiting a pit flush with the inside wall of the pit. xix. Provide a sump at the base of all discharge control pits, to prevent silt and debris from blocking the orifice or outlet pipe - the sump is a minimum Drainage easements Creation of private drainage easements iii. The applicant will bear all costs associated with the creation of the drainage easement. iv. Provide evidence that the easement has been prepared by a registered surveyor and has been lodged with the Land and Property Information Division for registration prior to the issue of a construction certificate, and that the easement has been registered prior to issue of an Occupation Certificate or occupation of the site. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-13 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER v. For sites that have existing Council pipelines through them that are not covered by an easement, or where an existing pipeline is not within the easement, Council will require the creation of an easement in favour of itself, or relocation of the easement over the existing pipeline. Relevant documents shall be submitted with the development application to demonstrate easement registration with the Land and Property Information Division of the Department of Lands has been established. vi. The minimum easement widths required over various pipe sizes are shown in the table below. Pipe Diameter (mm) Drainage Easement Width (m) 150 minimum pipe size in easement 0.9 – 1.0 225 1.0 – 1.2 300 1.2 – 1.5 375 , 450 1.5 – 2.0 525 , 675 2.0 – 2.5 750 , 900 2.5 – 3.0 1050 , 1200 3.0 – 3.5 1350 , 1500 3.5 – 4.0 1650 ,1800 4.0 – 4.5 Floodway Full width of nominated floodway Table 6.4.7: Drainage easement widths for common drainage lines and council pipelines Existing private drainage easement vii. Where it is proposed to discharge collected runoff into an existing pipeline that passes through an adjoining lot, or to lay a new pipe within an existing inter-allotment drainage easement, submit confirmation from NSW Land and Property Information to indicate that the subject property enjoys rights to use the drainage system with the development application. Council’s stormwater system and easement viii. Generally buildings over Council drainage easements and stormwater infrastructure will not be permitted. However, subject to the approval of Council, lightweight structures such as carports and pergolas may be permitted. ix. Where the location of the common drainage pipeline is in conflict with proposed building, relocate the drainage clear of the building in accordance with a hydraulic analysis, undertaken by a practising civil engineer, that demonstrates the hydraulic capacity of the system is not compromised due to the relocation. x. Where an approval is given for the construction of a carport or other light structure over a drainage easement, the structure will be easily demountable and be removed, at the owner’s expense, if requested by Council (for any necessary work within the easement). Sydney water xii. Submit written evidence of compliance with Sydney Water requirements with the development application. 6.4.16 Overland flow path Surface overland flow-paths are an integral part of the drainage system and must be considered at the design stage of the stormwater system. They are to be preserved and maintained unobstructed throughout the developed site and adjoining properties. xi. Do not obstruct any overland flow path - Council will enforce the removal of any obstruction to overland within private properties, and recover from the owners the coast of carrying out such work. xii. Do not obstruct existing runoff, entering the site from upstream properties or sub-catchments, from flowing into the subject site, or redirect it so as to increase the quantity or concentration of surface runoff entering adjoining properties. Note: During periods of heavy rainfall it is anticipated that there will be potential runoff, across boundaries of some properties, which will enter downstream sites from upstream properties due to the local contours of the area. xiii. Consider potential runoff at the design stage and design so it will not have any adverse impact on adjoining properties. Overland flow it should not be obstructed from flowing naturally and causing it to pond or concentrate along boundaries of adjoining properties. Suitable channels, open dish drains, walls or any other measures may be necessary to accommodate the existing and potential overland flow paths throughout the subject site. xiv. Care must be exercised to ensure that provision of any of the above remedial measures will not result in diverting runoff into the OSD system, if this is unattainable, then the OSD system must be designed to cater for the additional stormwater runoff anticipated from upstream catchment area(s). xv. Council may require that the design specify the extent of the overland flow path through the site, and that the development be located/modified clear of the overland flow path, or set at an appropriate freeboard. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-14 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER 6.4.17 i. Areas subject to possible flooding OSD is not required on sites affected by the 1 in 100 year flooding. Note: Council has a record of the flood levels for properties adjacent to the Cooks River and the Salt Pan Creek. Council will issue flood levels on written request, subject to a fee. Flood levels will be issued to Australian Height Datum to the nearest 100mm. Levels for the 1 in 20 year flood, 1 in 50 year flood and 1 in 100 year flood can also be provided. Approximate ground levels can also be given, however; it is the applicant’s responsibility to engage a surveyor to determine the actual ground and floor levels. ii. ii. Submit the original of the WAE of the drainage and OSD to Council, to verify that the constructed works have been completed in accordance with the approved design. The plan shall be prepared by a registered surveyor or an engineer and include all relevant levels. The WAE shall indicate an as constructed level adjacent to all design levels, including pit/tank cross sections, in red ink on the approved stormwater and OSD drawing. ii. Include the following on the WAE, as a minimum: (Refer to Appendix G – Flood Management & Flood proofing in order to address all relevant issues prior to submitting a development application). i. ii. Prior to occupation of the development the Crown will submit evidence of the compliance of this condition and the registration of documents with the Land Titles Office protecting the On-Site Detention System. 6.4.19 i. ii. Do not begin work on the site until the hydraulic plans have been approved in conjunction with the construction certificate by the nominated PCA. Certification Provide a compliance certificate of the constructed OSD - the certificate shall be prepared by an accredited engineer competent in the field of stormwater drainage design and who inspected Sufficient levels and dimensions of the constructed OSD, Locations, surface levels, invert levels of all drainage pits/grates/floor waste, Verification that orifice plate has been installed, together with its diameter, Verification that trash screens have been installed, Finished floor levels of units and garages, Weir/OSD overflow level, Detail of any variations or omissions made from the approved plans. 6.4.22 i. Requirements for construction certificate Submit detailed design calculations and plans with the construction certificate - to Council or an accredited certifier (PCA Civil). The drainage design is to comply with the requirements of the CDCP and the specific conditions of development consent. 6.4.20 i. Crown development A fully detailed design of the stormwater drainage system is required with the development application for Crown Development - a condition of the development consent will be imposed requiring the construction of stormwater drainage system in accordance with the approved drainage plans. Works as executed plan (WAE) i. All garages or parking areas are to be at least 150mm above the 1 – 100 year flood level. 6.4.18 List any variations on the certificate with the engineer’s justification as to how these discrepancies will not affect the performance of the system or the design parameters. 6.4.21 Council may require a flood study be undertaken and submitted with the development application, where flood studies have not previously been undertaken for areas adjacent to water courses. iii. Habitable floor levels of all residential and institutional buildings are to be a minimum of 500mm above the 1 – 100 year flood level. iii the OSD, examined the Work-as-Executed plans, and certifies that the works have been constructed in accordance with the approved design details. Before making any changes to the approved design during the construction the design engineer should discuss these with Council’s development engineer. Based on the extent and implications of the variations the Engineer will either be: Advised on the spot as to the acceptance or refusal of the discrepancies, or Requested to submit amended plans (section 96 modification) and calculations for approval. 6.4.23 i. Variations during construction Registration of OSD on title Any OSD system, location on the land, terms and conditions must be registered on the title of the property, prior to occupation of the development, issue of an occupation certificate or issue of a subdivision certificate, to ensure the owners are aware of the system’s design parameters, location and their obligation to maintain it. Note: A sample document for the guidance of applicants setting out the terms and conditions required by Council regarding the instrument to be registered is shown in Appendix E. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-15 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER 6.4.24 Flood management v. This section applies to development on land potentially affected by a one in 100 year Flood Standard for Salt Pan Creek and the Cooks River, as well as sites within close proximity to this flood plain within Canterbury. Objectives O1. Development in flood liable areas is designed and constructed to withstand the stresses of the highest probable flood. O2. Development will not increase the flood hazard or flood damage to other properties or adversely affect them in any way during times of flooding. Flood levels of all habitable rooms should be 0.5m or more above the standard flood level. A certificate by a registered practicing surveyor certifying the level of the completed building will be required. vi. Provide a certificate from a qualified practicing structural or civil engineer stating that the building is capable of withstanding the likely floodwaters and impact from debris in those waters without sustaining structural damage. Any other development Note: This Part should be read in conjunction with NSW Floodplain Development Manual – the development of flood liable land, 2005. vii. Developments such as sporting grounds and open air car parks will be considered on flood liable land. Any consent for such development will require certificates from surveyors and engineers as referred to above. Controls Habitable floor space New residential viii. Bedrooms, bathrooms, living rooms, study, lounge rooms, dining rooms, games rooms, kitchens, halls, garages, offices, laundries, utility rooms, manufacturing rooms / areas, class rooms, storage areas. i. Submit a survey plan to Council showing the relative levels to AHD, prepared by a registered practicing surveyor. ii. Flood levels of all habitable rooms should be 0.5m or more above the standard flood level. A certificate by a registered practicing surveyor certifying the level of the completed building will be required. iii. Where Council considers flooding could damage a proposed development, no work should be commenced until a qualified structural/civil engineer has submitted a certificate of structural adequacy with regard to stability as a result of flooding. Existing residential iv. Where additions and alterations to existing buildings include habitable rooms, a survey plan, prepared by a registered practicing surveyor and showing the relative levels of AHD, must be submitted. Non-habitable floor space ix. Decking, sports grounds, car parks. Note: The above lists are not exhaustive and may include other forms of accommodation, storage and space use. Flood levels x. Council will issue flood levels on written request. They will be issued to Australian Height Datum to the nearest 100mm. Levels can be provided for the 1 in 20 year flood, 1 in 50 year flood and 1 in 100 year flood. Approximate ground levels can also be given but it is the applicant’s responsibility to engage a surveyor to establish the actual ground and floor levels. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-16 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDICES FIGURE 1: Charge line clean out pit APPENDIX A: On-site stormwater detention checklist APPENDIX B: Intensity - Frequency - Duration Table APPENDIX C: Runoff Coefficients for Canterbury APPENDIX D: Silt arrestor Pit Details APPENDIX E: Restriction Instrument APPENDIX F: Absorption Design Calculation APPENDIX G: Flood management and flood proofing APPENDIX H: Drainage requirement checklist CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-17 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER FIGURE 1: CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-18 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX A On-Site Stormwater Detention (OSD) Checklist for Dual Occupancy and Single Dwelling including Additions and Alterations This form is to be used to determine if OSD will be required for residential developments and must be completed before the submission of any Application. Please read the reverse side of this form carefully for its applications and definitions. Part A. Address and type of proposed development Lot…………DP…………………………………………………………………………… No………… Suburb……………………………………………………………………………………. Street……………………………………………………………………….. Type of development (tick relevant boxes): □ Dual Occupancy □ Single Dwelling □ Extensions □ Garage, outbuildings and others (specify)………………………………….......... Part B. Exemption for flood affected areas Is the subject site located within an established 100 year floodplain and the site also floods in 20 and 50 year storm events (tick one only): □ Yes □ No If yes, OSD is not required. If no, go to Part C. Part C. Exemption for minimum allowable size of site impervious area Refer to the back of this page for definitions and explanations. 2 (a) Site area =…………………………………………………………………………………… (m ) 2 (b1) Total existing impervious area =………………………………………............................... (m ) (b2) Total remaining existing impervious area =……………………………………………….. (m2) (C) Proposed impervious area: 2 (C1) roofed areas =……………………………………………. (m ) 2 (C2) paved areas =……………………………………………. (m ) 2 (C3) supplementary areas =…………………………………… (m ) 2 (d) Total post-development impervious area (b2) + (C1 + C2 + C3) =…………………………. (m ) (e) Total proposed impervious area (C1 + C2 + C3) x 100 / (a) =………………………………..(%) (f) Existing impervious area percentage (b1) x 100 / (a) =……………………………………… (%) (g) Post-development impervious area percentage (d) x 100 / (a) =…………………………….. (%) OSD will not be required if either of the following is satisfied: □ (g) is less than 70% □ (f) is greater than 70% and (e) is less than or equal to 5% Notes: Developments covered by this form are for dual occupancy, single dwelling including alterations and additions and works that involve driveways, garage, outbuildings and hardstand areas. Commercial and multiple occupancy developments are not exempt from OSD. Definitions: Site Area (a): This is the total area of the site for which the development is proposed for residential development, the total site area is taken to be the area as shown on the Deposited Plan (DP). Existing impervious Area (b1): This refers to all of the impervious areas, within the site of the development. prior to any proposed works. This includes, calculated in plan view, all of the existing roofed areas, paved surfaces, hardstand areas, garages, outbuildings, etc. Remaining existing impervious Area (b2): This refers to the existing impervious areas of the site which will not be removed or demolished as part of the proposed works, but will remain after the proposed works have been carried out. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-19 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER If a building is to be altered internally, that is, works involving only the removal/demolition of internal non-structural members/walls within the footprint of the building, then the remaining impervious areas shall be calculated as the total area of the building. Existing Dwelling Proposed impervious Area (C): This includes all new impervious areas created as part of the proposed development, such as; all proposed roofed, paved, supplementary (i.e. In-ground swimming pools), garages, outbuildings and hardstand areas. Post-development impervious Area (d): This includes ALL of the impervious areas within the site that are to remain after the development is completed, that is, the finished works and includes all of the remaining existing and proposed impervious areas. C2 New concrete crossing C b1 & b1 & b2 Ubi8 Existing Garage C2 C1 C3 CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-20 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX B Rainfall Intensities in Canterbury (mm/h) Duration (Minutes) 5 6 7 8 9 10 11 12 13 14 15 16 17 18 20 25 30 35 40 45 50 55 60 45 90 2 hours 3 hours 4 hours 5 hours 6 hours 8 hours 10 hours 12 hours 14 hours 16 hours 18 hours 20 hours 22 hours 24 hours 36 hours 48 hours 60 hours 72 hours Average Storm Recurrence Interval (years) 1 2 5 10 20 50 100 94 88 83 79 75 72 69 67 64 62 60 58 57 55 52 46.9 42.7 39.3 36.6 34.3 32.3 30.6 29.1 36.6 22.7 19.0 14.7 12.2 10.6 9.43 7.88 6.83 6.08 5.54 5.1 4.75 4.45 4.19 3.97 3.07 2.53 2.16 1.89 199 188 178 169 162 156 150 145 140 136 132 128 125 122 116 105 96 89 83 78 74 70 67 83 52 43.2 33.2 27.5 23.8 21.2 17.6 15.2 13.5 12.3 11.3 10.5 9.87 9.30 8.81 6.81 5.62 4.81 4.21 233 219 208 198 190 183 175 170 165 160 155 151 147 143 137 123 113 105 98 92 88 83 80 98 62 51 39.3 32.6 28.2 25.0 20.7 17.9 15.9 14.5 13.3 12.4 11.6 11.0 10.4 8.03 6.63 5.67 4.96 258 243 231 220 211 203 196 189 183 178 173 168 164 160 152 138 127 117 110 104 98 94 89 78 69 57 44.0 36.4 31.5 27.9 23.1 20.0 17.7 16.2 14.9 13.9 13.0 12.2 11.6 8.96 7.40 6.33 5.54 120 113 107 101 97 93 89 86 83 80 78 75 73 71 68 61 55 51 47.5 44.5 42.0 39.8 37.9 47.5 29.5 24.6 19.0 15.8 13.7 12.2 10.2 8.84 7.87 7.16 6.60 6.14 5.75 5.42 5.14 3.97 3.27 2.80 2.45 155 146 138 131 125 120 116 112 108 104 101 98 96 93 89 80 73 67 61 59 56 53 50 61 39.2 32.7 25.2 20.9 18.1 16.1 13.4 11.6 10.3 9.39 8.65 8.05 7.54 7.11 6.74 5.20 4.29 3.67 3.21 173 163 155 147 141 135 130 126 121 118 114 111 108 105 100 90 83 76 71 67 63 60 57 71 44.7 37.2 28.6 23.7 20.5 18.2 15.1 13.1 11.7 10.6 9.78 9.10 9.53 8.04 7.61 5.88 4.86 4.15 3.63 CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-21 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Polynomial coefficients for Canterbury The following table has been obtained from the Bureau of Meteorology, reference FiV299O, dated 2nd May 1989 and refers to the following location 33.925 South, 151,100 East (near Campsie). List of Coefficients to equations of the form: In(I) = a + b * (In(T)) + c*(In(T))**2 + d*(In(T))**3 + e*(In(T))**4 + f*(In(T))**5 + g*(In(T))**6 I = Intensity in millimetres per hour T = Time in hours ARI a b c d e f g 1 3.3659 -0.5895 -0.0368 0.00768 0.001088 0.0002073 0.0000324 2 3.6278 -0.5874 -0.0393 0.00747 0.001347 0.0001911 0.0000417 5 3.9054 -0.5829 -0.0462 0.00787 0.001891 0.0002783 0.0000406 10 4.0403 -0.5802 -0.0504 0.0078 0.002316 0.0002836 0.0000526 20 4.1919 -0.5788 -0.0533 0.00821 0.002514 0.0003451 -0.000047 50 4.3626 -0.5761 -0.0568 0.00802 0.002846 0.0003344 0.0000579 100 4.4766 -0.5749 -0.0592 0.00823 0.003037 0.0003675 0.0000579 (years) * Please note; that the data provided is derived automatically by computer using the nearest grid point to the latitude and longitude of the location, not the location name. Therefore; because of possible mistake in specifying the latitude and longitude by the user or in transference to the Bureau computer, it is essential that you check that the location you require (to the nearest 0.025 degrees) corresponds to the latitude and longitude on the curves and tabulated data supplied. If there are any discrepancies, please contact the Bureau of Meteorology, Hydrology Branch, Melbourne. Alternative Rainfall Site Data The following nine parameters can be applied in the methods provided in Chapter 2 of Australian Rainfall and Runoff (1987). 2 year I 1 hr : 37.89 I 12 hr : 7.87 I 72 hr : 2.45 50 year I 1 hr : 79.68 I 12 hr : 15.90 I 72 hr : 4.96 Skewness Factor G : 0.00 Short Duration Factors: F2 : 4.29 F50 : 15.85 CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-22 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX C Runoff coefficients for Canterbury (from A.R.&R. Figure 14.13) ARI years Fraction Impervious 0 0.1 0.2 0. 0.4 0.5 0.6 0.7 0.8 0.9 1 1 0.41 0.44 0.47 0.50 0.53 0.57 0.60 0.63 0.66 0.69 0.72 2 0.44 0.47 0.50 0.53 0.57 0.60 0.63 0.67 0.70 0.73 0.77 5 0.49 0.52 0.56 0.60 0.61 0.67 0.71 0.74 0.78 0.82 0.86 10 0.51 0.55 0.59 0.63 0.67 0.71 0.75 0.78 0.82 0.86 0.90 20 0.54 0.58 0.62 0.66 0.70 0.74 0.78 0.82 0.86 0.90 0.95 50 0.59 0.63 0.68 0.72 0.77 0.81 0.86 0.90 0.95 0.99 1.04 100 0.62 0.66 0.71 0.76 0.80 0.85 0.89 0.94 0.99 1.03 1.08 Note: A minimum runoff coefficient of 0.7 should be adopted for design purposes. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-23 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX D CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-24 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX E INSTRUMENT SETTING OUT TERMS OF RESTRICTIONS AS TO USER OF LAND AND POSITIVE COVENANT INTENDED TO BE CREATED PURSUANT TO SECTION 88B OF THE CONVEYANCING ACT 1919 Lengths are in metres (Sheet 1 of 3 sheets) Plan: Subdivision covered by Council Clerk's Certificate No. Full name and address of proprietors of the land Paul Citizen and Sharon Citizen 13 Cross Street City PART 1 Identity of Restriction As To User firstly referred to in the above mentioned plan. Schedule of Lots Affected Lot/s Burdened Lot x Lot/s, name of Authority Benefited Canterbury City Council Identity of Positive Covenant, Easement secondly referred to in the above mentioned plan. Schedule of Lots Affected Lot/s Burdened Lot x Lot/s, name of Authority Benefited Canterbury City Council PART 2 1. Terms of Restriction on Use firstly referred to in the above mentioned plan. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-25 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER The standard terms of the Restriction On The Use Of Land under Section 88B shall benefit Canterbury City Council or under Section 88E shall nominate Canterbury City Council the prescribed Authority and shall read as follows: The Proprietor of the burdened lot(s) shall not: (a) Erect, construct or place any building or other structure. (b) Make alteration to the ground surface levels, grates, pits, kerbs, tanks, gutters or any other structure associated with the on-site stormwater detention system. (which expression shall include; all ancillary gutters, pipes, drains, walls, kerbs, pits, grates, tanks, chambers, pumps, basins and surfaces designed to temporarily drain stormwater) (hereinafter called "the system"). Within the land so burdened, without the prior written consent of Canterbury City Council. 2. Terms of Public Positive covenant (firstly/secondly/thirdly/fourthly) referred to in the above mentioned plan. The standard terms of the Positive Covenant under Section 88B shall benefit Canterbury City Council or under Section 88E shall nominate Canterbury City Council the prescribed Authority and shall read as follows: 1. The proprietors of the lots burdened will in respect to the system described in the this instrument: restriction on use referred to in (a) permit stormwater runoff to be temporarily detained by the system; (b) keep the system clean and free from all silt, rubbish and debris; (c) maintain and repair the system so that it functions in a safe and efficient manner; (d) replace, maintain, repair, alter, and renew the whole or parts of the system within the time and in the manner specified in a written notice issued by the Council; (e) carry out the matters referred to in paragraphs (b), (c) and (d) above at the proprietor's expense; (f) not make any alterations to the system or elements thereof without prior consent in writing of the Council; (g) permit the Council or its authorised agents from time to time upon giving reasonable notice (but at any time and without notice in the case of an emergency) to enter and inspect the land for compliance with the requirements of the covenants set forth herein. 2. In the event of the registered proprietor failing to comply with the terms of any written notice served in respect of the matters in clause (i) above, the Council or its authorised agents may enter with all necessary equipment and carry out any work required by such notice to ensure the safe and efficient operation of the system and recover from the registered proprietor the cost of carrying out such work, and if necessary, recover the amount due by legal proceedings (including legal costs and fees) and enter a covenant charge on the lot burdened under section 88F of the Conveyancing Act 1919. In carrying out any work under this clause, the Council shall take responsible precautions to ensure that the land is disturbed as little as possible. 3. Comply with the terms of any written notice issued by Council in respect to the requirements of the covenants set forth herein, within the time stated in the notice. In these covenants "Council" means Canterbury City Council. Name of person or authority whose consent is required to release, vary or modify the Restriction as to User and Positive Covenant referred to in the above mentioned plan. The Council of the City of Canterbury CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-26 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Signed in my presence by the said _________________________ ___________________________ Signature of Witness Signed in my presence by the said _________________________ ___________________________Signature of Witness CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-27 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX F ABSORPTION DESIGN CALCULATION SITE DETAILS Address 2 Site Area (m ) 2 Impervious Area (m ) Nominal Absorption Rate (ARN) Reduction Factor (FR) Design Details 2 2 Design Impervious Area (DA) area ……..m x 1.2 = ………..m (DA) Design Absorption Rate (ARN) ARN …. l/m /sec x FR ….. = ….. l/m /sec (ARD) Base Area of Absorption Pit (BA) Width …. m x Length …. m = … m (BA) 2 2 2 Required Absorption System Volume Calculation for 50 Year ARI Storm Time T Rainfall Intensity Runoff I R =I DA/3600 min mm/hr l/s 5 233 6 219 7 208 8 198 9 190 10 183 11 175 12 170 13 165 14 160 15 155 20 137 25 123 30 113 45 92 60 80 90 62 120 51 x Runoff Volume Infiltration Vol RV = R x T x 60/1000 IV = BA x ARD x T x 60/1000 m 3 Maximum required Absorption System Volume m 3 Required Absorption Volume RV – IV m 3 m 3 CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-28 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER APPENDIX G Construction standards for development in flood liable areas Electrical and Mechanical Materials (a) Main Power Supply Subject to the approval of Energy Australia the incoming main commercial service equipment, including all metering equipment should be located above the DFL. The dwelling must be able to be easily disconnected from the main power supply. (b) Wiring All wiring, power outlets, switches, etc., should, to the maximum extent possible, be located above the DFL. All electrical wiring installed below the DFL should be suitable for continuous submergence in water and should contain no fibrous components. Only submersible-type splices should be used below the DFL. All conduits located below the DFL should be installed so that they will be self-draining if subject to flooding. (c) Equipment All equipment installed below or partially below the DFL should be capable of disconnection by a single plug and socket assembly. (d) Heating & Air Conditioning Heating and air conditioning systems should, to the maximum extent possible, be installed in areas and spaces of the house above the DFL. When this is not feasible every precaution should be taken to minimise the damage caused by submersion according to the following guidelines. Fuel Heating systems using gas or oil as a fuel should have a manually operated valve located in the fuel supply line to enable fuel cut-off. Installation The heating equipment and fuel storage tanks should be mounted on and securely anchored to a foundation pad of sufficient mass to overcome buoyancy and prevent movement that could damage the fuel supply line. All storage tanks should be vented to an elevation of 600 millimetres above the DFL. Ducting All ductwork located below the DFL should be provided with openings for drainage and cleaning. Self draining may be achieved by constructing the ductwork on a suitable grade. Where ductwork must pass through a water-tight wall or floor below the DFL the ductwork should be protected by a closure assembly operated from above DFL CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-29 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Construction Materials Construction materials are graded into the following four classes according to resistance to flood waters: Most Suitable The materials or products which are relatively unaffected by submersion and unmitigated flood exposure and are the best available for the particular application. Minor Effects Where the “most suitable” materials or products are unavailable or economic considerations prohibit their use, these materials or products are considered the next best choice to minimise the damage caused by flooding. Marked Effects As for “2 preference” but considered to be more liable to damage under flood conditions. To Be Avoided The materials or products listed here are seriously affected by floodwaters and in general have to be replaced if submerged. nd Buildings should be constructed using the “most suitable” materials. See Table 1 attached to this Plan. Second and third preference materials will only be considered where circumstances warrant it. COMPONENT Flooring and sub-floor structure. ORDER OF PREFERENCE MOST SUITABLE SECOND PREFERENCE THIRD PREFERENCE TO BE AVOIDED Timber floor (T&G boarding, marine plywood with ends only epoxy sealed on joints and provision of side clearance for board swelling. Timber floor close to ground with surrounding base. Timber flooring with ceilings or soffit linings. Timber flooring with seal on top only. Asphalt tiles with asphaltic adhesive. Asphalt tiles (A). Carpeting, gluedown type or fixed with smooth-edge or jute felts. Concrete slab-onground monolithic construction. Note: Clay filling is not permitted beneath slab-onground construction, which could be inundated. Floor covering. Wall Structure (up to the DFL). Suspension reinforced concrete slab. Clay tile. Concrete, precast or in situ. Timber floor (T&G boarding, marine plywood) full epoxy sealed, on joints. Cement/bituminous formed-in-place. Cement/latex formed-in place. Rubber tiles, with chemical-set adhesive. Concrete tiles. Epoxy, place. formed-in- Mastic flooring formed-in-place. Terrazzo. Rubber sheets with chemical-set adhesives. Vinyl tiles chemical-set adhesive. Silicone floors formed-in-place. Vinyl tiles, asphaltic adhesives. Vinyl sheets with chemical-set adhesive. Loose rugs. Ceramic tiles with acid and alkaliresistant grout. Two skins of brickwork or blockwork with Solid brickwork, blockwork, reinforced, concrete Loose fit nylon or acrylic carpet with closed cell rubber underlay. Ceramic tiles (A). Chipboard (particle board). with Brick or blockwork veneer construction with inspection Cork, Linoleum, PVA emulsion cement, rubber sheets or tiles (A), vinyl sheets or tiles (A). Vinyl sheets or tiles coated on cork or wood backings fibre matting (sea-grass matting). Inaccessible cavities. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-30 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER COMPONENT ORDER OF PREFERENCE MOST SUITABLE SECOND PREFERENCE or mass concrete. Roofing structure (for situations where DFL is above the ceiling). Doors. Reinforced concrete construction. Galvanised metal construction. Wall and ceiling linings. inspection openings. Solid panel with water proof adhesives. Flush door with marine ply filled with closed cell foam. Painted metal construction. Aluminium galvanised frame. Compressed cement or plaster board. THIRD PREFERENCE Flush panel or single panel with marine ply wood and water proof adhesive. T&G lined door, framed ledged and braced. Painted steel. Timber frame fully epoxy sealed before assembly. Brick, common. Plastic wall tiles. or steel Brick, face or glazed in waterproof mortar. Timber trusses with galvanised fittings. Inaccessible flat roof construction. Ungalvanised steelwork eg lintels, arch bay tie rods, beams etc. Unsecured tiles. Hollow core ply with PVA adhesive and honeycomb paper core. roof Fly-wire doors. Standard frame. Chipboard exterior grade. Chipboard. Fibreboard panels. Hardboard exterior grade. Minerar fibreboard. Paperboard. Plaster-board, gypsum plaster. Wall coverings (paper, burlap cloth types). timber Wood, solid or exterior grade plywood fully sealed. Wood, solid (boards or trim) with allowance for swelling. Wood, plywood exterior grade. Fibrous board. plaster Wood, standard plywood strawboard. Bat or types. blanket Open types. Timber with PVA glues mild steel fittings. Concrete block. Steel waterproof applications. Stone, natural solid or veneer, waterproof grout. Glass blocks. Glass. Plastic sheeting or wall with waterproof adhesive. Insulation. Foam or closed cell types. Reflective insulation. Windows. Aluminium frame with stainless steel or brass rollers. Epoxy sealed timber waterproof glues with stainless steel or brass fittings. Galvanised painted steel. Removable hinges. Rubber mouldings & trim. Traditional timber roof construction. window with or Large openings. Metals, non ferrous. Brass, nylon stainless steel. Concrete. openings. Nails, bolts, hinges and fittings. TO BE AVOIDED cell fibre or Mild steel. pin CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-31 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Appendix 6.4G: Table 1: Flood management and flood proofing Definitions Flood Relatively high stream flow that overtops the natural or artificial banks in any part of a stream or river. Flood Standard The flood selected for planning purposes based on flood behaviour and associated flood risk taking into account social, economic and ecological considerations. Floodway The area where the main flood waters pass when floods occur often resulting in hazardous situations because of the depth and speed of the floodwater. Flood Storage Those parts of the flood plain that are important for the temporary storage of floodwaters. Flood Fringe Land outside the flood ways which may be flooded infrequently and where development will normally be approved subject to flood proofing measures. AHD Australian Height Datum – a common national plane of level corresponding approximately to mean sea level. Survey Plan A plan prepared by a surveyor registered with the Surveyors Act 1929, showing the boundaries and location of a property, plus any existing or proposed building or other improvements together with existing levels to AHD. Designated Floor Level (DFL) The minimum floor level acceptable to Council when giving consent to an application for development. It will normally be 0.5m above the Standard Flood Level for habitable rooms. Habitable Room Means a room, compartment or enclosed area that is designed, constructed, capable of being used or adapted for activities normally associated with domestic living, such as a bedroom, living room, lounge room, television room, kitchen, dining room, study, playroom and the like. Freeboard The height of the Designated Floor Level above the Flood Standard to allow for wave action and local hydraulic effects. Flood Liable Land Land that would be inundated as a result of the Standard Flood. CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-32 PART 6.4 GENERAL CONTROLS - DEVELOPMENT ENGINEERING FLOOD AND STORMWATER Type of development Property falls to Street OSD required Charged line Absorption system N/A N/A Pump system N/A Yes (1) Rear away from street Yes (1) Yes (6) Yes (6) No (2) Street/rear Yes (1),(3) Yes (6) Yes (6) No (2) Dual occupancy Street Yes (1) No No Dual occupancy Rear Yes (1) No No Townhouse/villa Street Yes No Townhouse/villa Rear Yes Single dwelling Single dwelling Adds/Alts Outbuilding Residential building flat Residential building flat Commercial/Industrial (4) Street Rear (4) Street Comments No No (2) No No (5) No No No (5) Yes No No No (5) Yes No No No Yes No No No (1) OSD must be provided if postdeveloped impervious area is greater than or equal to 70% of the site area (Refer section 6.4.10) (2) Drain site by gravity pipe using stormwater easement via downstream property, pump system may be considered where easement is rejected AND all supporting (documents*) are provided accordingly. For single dwellings only, a pump system is permissible where alternative methods (charged and absorption) are not viable (3) Proposed development that does not increase existing impervious area shall be connected to existing drainage system however; OSD must be provided where the existing impervious area is equal to 70% or more and the proposed additions / alterations are more than 5% of the site area (4) Gravity pipe system using a stormwater easement via downstream property is the only method accepted Commercial/Industrial Rear (4) Yes No No No (5) For basement driveway only with 2 maximum area of 50m , can drain into a pump system, pump wet well to have a capacity for 1 hour storm 2 (that is, 50m will require a pit with 3000 litres capacity) (6) Both charged and absorption system are permissible providing they comply with section 6.4.14 Table 6.4.2 Drainage requirement checklist for proposed development in Canterbury Notes for Table 6.4.2 impervious area includes all buildings and paved areas (roof, driveway, car parking space and swimming pool, (see Appendix A.) Supporting documents include the following: 1. A land valuation prepared by a registered land valuer to estimate the value of the easement only (excluding construction/installation cost). 2. A signed letter of request from the applicant to all possible downstream properties requesting their permission to create a stormwater easement through their property (the amount estimated in the valuation report must be disclosed in the letter as an offer of compensation,) and that all relevant expenses to construct and reinstate any disturbed areas is at the cost of the applicant. 3. A signed letter of correspondence from the downstream property owner(s), either accepting or rejecting the request CANTERBURY DEVELOPMENT CONTROL PLAN 2012 P6.4-33