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Landscape Tanks™
ON-SITE STORMWATER DETENTION SYSTEM (OSD)
Patent Granted # 2010286347
Key Features
Landscape Tanks™ On-Site Stormwater Detention (OSD) system …
Satisfies council OSD regulations*
Is a functional structural retaining wall
Is a barrier (sight, sound, wind, sun, physical or thermal)
In addition to those functions, the tanks come with high finishes, numerous decoration options and a built-in planter (garden) top.
Our OSD tanks have a low preparation, fast easy installation profile, are modular and manufactured to a high standard. This provides flexibility in where the tanks are placed, cost advantages, allows for faster installation and will suit most sites and storage requirements.
For the landowner these unique characteristics can provide distinct benefits over other OSD systems available in the market.
*Please note, the guidance given on this page is general in nature. Always seek professional advice. If you would like introductions to Hydraulic Engineers who are familiar with our tanks e-mail us at operations@landscapetanks.com.au
Landscape Tanks™
Our On-site Stormwater Detention System
Landscape Tanks™ OSD system is based around our core design philosophy of multi-functioning, better use of space, providing core functionality well and offering a large number of decoration options. Landscape Tanks™ tanks are Australian designed, 100% Australian owned and manufactured using near 100% Australian materials and labour. We were the first in the world to incorporate water storage into a modular and flexible arrangeable retaining wall, with minimal site preparation and fast installation attributes. To achieve this outcome required a large investment in research and development and ended in numerous patent and proprietary systems.
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Key Benefits
of Landscape Tanks™
Better Value / Lower Overall Total Cost
Our tanks’ inherent multi-functionality allows you to do two or more things with a single piece of expenditure. Multi-functionality gives our tanks distinct cost advantages over our prefabricated and on-site built tank competitors. Our tanks offer all the advantages of a prefabrication tank, including; not having to fabricate moulds, not needing water proofing, no additional tank structural engineering, fewer design costs, to name a few.
Better Aesthetics
Our manufacturing process produces a soft, cool and buttery finish guaranteed to AS3610 Formwork for Concrete Class 2 or better. A quality finish is a priority, not an afterthought. A better surface increases your placement options and property value. With Landscape Tanks™ the traditional tank treatment of hiding or burying tanks becomes obsolete. The tanks can be proudly placed anywhere.
Low Preparation
Landscape Tanks™ require minimal site preparation works. Excavate to the required ground level, then add crushed and compacted rock (50mm) to assist with levelling of your surface, that’s it, no footings or piers are required.
Fast Easy Installation
Use heavy lifting equipment to place the tanks into position. Join the tanks in minutes without needing a plumber present. This is achieved thanks to the patented seals quick connection system. Rubber seals are built into the tank walls, just push the pipe into the two adjoining seals to join tank water reservoirs and allow water to flow from tank to tank. Connecting tanks takes minutes and is an easy process unique to Landscape Tanks™.
Low Basic Labour Inputs
At installation, your staff only need to be able to produce a level crushed rock platform using a screed, and arrange numbered tanks in accordance with simple plans. Basic skills which can be performed quickly and accurately by any trade.
No Water Testing Required
As the seals are installed at the factory, rather than by a plumber at site, no water testing needs to be performed. The seals have been installed, checked and are fully operational prior to leaving the factory.
No Waterproofing Required
Unlike in-situ builds our tanks are constructed from one process, a single pour using concrete with an mPa well above that needed to make cement waterproof. Waterproofing is yet another cost and inconvenience you can avoid by using Landscape Tanks™.
No Tank Structural Engineering Required
For in-situ built tanks, costly structural engineering is often needed to ensure the tank will withstand forces applied to it. For prefabricated tanks that chore and associated costs have been performed for you.
Modularity
The Landscape Tanks™ tank system is modular, allowing you to connect the tanks in an almost infinite number of sequences and arrangements. This characteristic makes the tanks adaptable to most sites and gives the customer control over desired water storage volumes, engineering, and architectural outcomes.
Higher Precision
Our tanks are manufactured in a factory from three piece steel precision moulds. The “rolls royce” of moulds. Our moulds allow us to produce the highest quality tanks from moulds that are reinforced to resist warping, stretching or shape changes.
Self-Installation
Our OSD tank system is simple; it’s easy, quick and low-cost installation profile, allows your builder or plumber to do the installation cheaper, faster and quicker than we can. We can assist with the arranging of freight by introducing you to and arranging quotes from professional haulage companies. We are happy to allow customers to deal directly with carriers. That saves you time, allows you to control delivery parameters and reduce costs. If you need help with installation, we can arrange for that too!
Customisation / Personalisation
Landscape Tanks™ tanks can be personalised through concrete tinting (up to 60 colours available), polishing, painting, rendering, bagging, stencilling, tiling, sand blasting, embossing, cladding, decking and having posts fastened to them. The lid is a planter which provides you with additional garden space. Both the form (finish and decoration) and function (how they operate) of our tanks is very important to us.
Elimination of Site Based Risks
Our OSD system eliminates or reduces many frustrations and risks associated with on-site tank builds. For example, you can purchase our OSD tanks in one transaction and perform one simple installation. In contrast, in-situ builds require many transactions and build parts performed by numerous different trades. In addition to these steps, onsite builds also require the separate procurement of OSD accessories.
Clever Australian Design
Our tanks embody clever Australian design. Born from a simple concept that the tanks must perform more than one function and that they need to be flexible, arrangeable and have a quick low-cost installation profile.
Durability, Longevity, Long Warrantee, Low Maintenance
The tanks are made from long lasting, highly durable, low-maintenance concrete and are guaranteed free from workmanship, structural or material fault for 25 years for the concrete shell, and 7 years for all other components.
Better Time and Risk Profile
Landscape Tanks™ can be installed in hours or days; on-site builds can take weeks or months. A reduced installation time frame means lower interest costs, frees up trades to do other jobs, reduces the time needed for site scheduling, supervision and organising of trades. Risks increase with time, quotes expire, prices change, delays occur and the chances of damage to works completed increases. The longer the build period, the higher the chance of injury, vandalism or theft. The shorter build period offered through prefabricated tanks provides several benefits.
Contributes to Property Value
Our tanks are designed and manufactured to be seen and admired, not buried or hidden. We take time to ensure they have the best finish, highest number of decoration options and functions. They are made with consideration to the matters that ensure they complement and add to your property value, not detract from it.
A Newcomer's Guide to On-Site Stormwater Detention
Everything you need to know about On-site Stormwater Detention along with explanations of OSD terminology you’re likely to encounter.
What is on-site stormwater detention? How is it different from a water tank?
Households in Australia are generally required to have both “retention” (through BASIX) and possibly “detention” (through OSD), for their new build. What is the difference between the two? Def’n, “Retention” means the storage of water for use at your property. It’s traditionally and commonly known as a “water tank”. Def’n, “Detention / On-site Stormwater Detention” means the shaping of water flows from a site using a water valve and a temporary storage reservoir. It’s the collection of rainwater runoff and then the release of water captured to council stormwater at a pre-ordained and capped rate. In fishing terms, OSD is “catch and release” (detention), your basix rainwater tank is, “catch and eat (use)” (retention).
Why are increases in runoff a problem?
Stormwater flows which discharge from your site over hours, days and weeks before your development (build) now due to your development, can occur in seconds or minutes. Increasing hardstand area shortens the outflow time profile and because of the drainage profile being shorter, it must also be larger. Flooding is undesirable. OSD is not an attempt to tame nature (flooding), it’s a mechanism to ensure new developments don’t increase flooding frequency or size. OSD is about making sure new works don't make things worse.
Why aren’t I able to retain and use the OSD water I capture?
Two reasons; Firstly, OSD isn’t there to replace or augment your (BASIX) rainwater storage obligations. Rainwater storage and OSD are designed to achieve two separate and unrelated goals. Secondly and more importantly, if you retain all captured water from your site, rather than temporarily detain and completely drain your OSD tank after each rain event, for subsequent rain events your full or partially full OSD system will discharge earlier or immediately to council stormwater infrastructure. Your OSD tank will no longer be OSD, it will act like a rainwater tank.
Why does on-site stormwater detention exist? What is on-site stormwater detention’s purpose?
Prior to urban development our terrain acted much like a sponge during rain events. A thirty minute downpour would seep into soils, be absorbed by plants and be detained temporarily in shallow pooling. Overflows and weeping from water-sodden soils would slowly run off the land, accumulate and eventually make their way to the sea via streams and rivers. A thirty-minute downpour would progressively flow from your property over hours, days, weeks or become atmospheric humidity, soil moisture or seep down to the water table. OSD is concerned with rainfall that discharges unnaturally, directly and instantly from your “hard stand surfaces”* to council stormwater infrastructure. OSD looks at water flows from urban development that occur earlier, over shorter periods and at higher flows, than they did prior to building works. OSD is there to address “flooding” caused by development. Councils will refer to the purpose of OSD in more clinical terms e.g. “the purpose of OSD is to not increase downstream flooding in all but a 1% AEP event”. Translation, your development is not allowed to increase water runoff other than in a one in a hundred year rain event. A goal you are required to achieve “efficiently and effectively” and with “good aesthetics”. *Please note, “Hard stand surfaces” are roofs, driveways, verandas, paths, paved areas. Any man-made surface.
What are the undesirable downstream consequences from increased water runoff?
The four main consequences are: 1. Flooding of neighbours or public spaces. 2. The potential for overloading or damaging of council stormwater infrastructure. 3. The risk of stormwater overflowing into sewers creating sanitation or disease issues. 4. The potential for waste being carried and then deposited into tributaries where the waste is both difficult and expensive to recover, not to mention unsightly and where it adversely affects native flora and fauna. In addition to the undesirable outcomes, an impetus to have OSD comes from: • The speed of development outstripping the ability of utilities to increase stormwater infrastructure. • Stormwater infrastructure upgrades needed in places where space is limited and access is difficult. Where the costs along with the technical expertise needed to complete works become larger and more complex, respectively. • Stormwater infrastructure travelling through numerous different councils introduces politics into the stormwater infrastructure management equation. To upgrade these stormwater systems requires agreement by a number of authorities on not only the scope, design and timing of works but also and more importantly, who controls the works and how much each authority pays.
What properties are affected by OSD?
Most works where a development application (DA) is required and council stormwater regulations come into play will, (most likely), have OSD obligations. Depending on the jurisdiction in which you reside, OSD is becoming more the rule than the exception.
On-site Stormwater Detention Exemptions, Concessions and Relaxations
Exemptions
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Where a central party completes your OSD obligations for you. An example of this is where your land developer has constructed a large central OSD system covering off the OSD obligations of all blocks of land in the development.
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Where your works are minor. “Minor” is usually defined as less than 50 sq metres of extra hard stand.
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Change of use as opposed to change in size. Where the dwelling footprint remains unchanged, but its contents and internal layout change.
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Where you are only realigning a boundary.
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In some, many jurisdictions, single residential dwellings.
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Where the building will only cover a small percentage of the site. The “small percentage” bar is usually set at less than 55% site impervious area (SIA).
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Where your property drains directly to an existing natural water tributary, bay or sea. Where your site does not rely on community stormwater infrastructure.
Concessions and Relaxations
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A reduction in the OSD volume required is usually provided for:
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Granny flat additions.
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Where you install rainwater tanks that are larger than what is required by your council.
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Where the council deems it reasonable that your OSD obligations are reduced or quashed.
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What does the On-site Stormwater Detention process involve?
The typical council OSD requirements are provided below
Please note, each council can or will have different OSD regulations. There can be significant differences between jurisdictions for countless reasons including but not limited to the topography, historical factors and planning influences.
Designer / Certification
Your OSD tank must be designed and then after the tank has been commissioned, it must then be certified by a suitably qualified hydraulic engineer. The design and certification processes focus engineers on “function” (how it works), usually at the cost of “form” (how it looks).
OSD Components
Broadly speaking most councils ask for your OSD installation to have the following characteristics:
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That runoff from introduced hard surfaces (roof etc) is directed to the OSD tank, except if the runoff originates from an adjoining property.
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Inflow to and outflows from the OSD tank to occur naturally under gravity.
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The OSD outflow (orifice level) needs to be at least 100mm above the HGL (high gradient line). In other words, the outflow point on your OSD tank needs to be 100mm above council stormwater drains to which it connects.
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The OSD outflow (orifice level) is 300mm or more below the level of your house slab.
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The OSD tank will include;
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Access - usually, a (drivable) steel grate.
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Child proof locks on access points.
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Usually, a minimum bore diameter for the orifice.
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A requirement to have or not have a high early discharge (HED) chamber.
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A sump or no sump.
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Relief drains or no relief drains.
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Often, a separate discharge control pit (DCP).
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Maintenance that the landowner is obligated to perform.
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The Most Common Types of OSD
Under Driveway
OSD tanks incorporated into and placed under a driveway. This is the preferred OSD type of councils and engineers. It’s also the most expensive and difficult OSD tank to construct.
Above Ground
Traditional Water Tank Model
Modified above ground tanks (poly, steel or concrete) which need to be hidden due to their poor aesthetics. Cheap but aesthetically poor.
Below Ground
Most often concrete tanks which are prefabricated or on-site built. The tanks are kept below ground to hide their poor aesthetics. The below ground positioning increases build costs.
Pond
The cheapest of all OSD options but potentially also the most visually unpleasant. It’s a fenced unusable space bordered by a waterproof small retaining wall. To achieve the volumes required your shallow OSD pond usually occupies a large portion of your yard.
Landscape Tanks™ OSD
We incorporate your OSD tank in retaining wall(s), fences, under driveways or in other necessary walls or structures.
Pricing & Quotes
What's included?
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The standard planter (top).
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Our standard engineering.
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All internal pipe requirements for standard format set ups. This allows you to install the tanks including your planters quickly without needing to visit a plumbing shop.
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Four diagonally positioned “pin head lifts” (2.5t for large tanks, 1.3t for small and medium tanks and standard, deep planters and flat top) to allow easy lifting.
Definitions of common On-site Stormwater Detention terminology
DCP (discharge control pit), is the name given to a pit separate to the main OSD reservoir which houses:
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Orifice plate.
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Maximesh (filter).
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Ladder or step irons.
HED (high early discharge) is the description given to a separate chamber within your OSD tank which receives water flows first and then overflows to the main OSD reservoir. The purpose of the HED is to achieve desired maximum water pressures, earlier. Creating the maximum water pressure earlier allows the desired maximum outflow rate to occur sooner. The HED reduces the likelihood of the OSD tank overflowing to council stormwater infrastructure.
Maximesh RH30/30 is a type of punched steel sheet mesh used for filtering. The brand name and size of mesh prescribed by councils. Many OSD documents use “maximesh” in place of the function it performs, “filtering”.
Orifice is a water flow valve. It’s produced from a flat piece of plate metal by cutting a hole in it. Water pressure and bore diameter determines flow rate. The hole in the plate is laser cut, with sharp edges, to extremely high accuracy (plus or minus half of one millimetre).
Permissible Site Discharge (PSD) is the maximum flow rate (as controlled by the orifice valve) from your OSD system. PSD is calculated by your hydraulic engineer using a formula provided by your council. Variables in the formula include your blocks area, your “SIA” and multipliers determined by authorities to achieve desired outcomes.
Site’s Impervious Area (SIA) is the percentage of your block which has hard stand (roof, driveways, walkways etc) post completion of your building works. The part of the site which has inherited a fast discharge profile because of your development.
Site Storage Requirements (SSR) is the minimum size of the OSD reservoir required. The litres of storage you are required to have. The size of your tank.
Sydney Water’s General OSD Guidelines
Sydney Water’s OSD guideline can be accessed here.