Construction on our new nursery at Theresa Park is progressing well and our massive shade house has been completed after six weeks. To give you an idea of it’s size, it has 1km of upright posts and over 16,000m2 of shade cloth.
Below is an extract from our article appearing in next months Australian Horticulture magazine:
Getting it Right from the Ground-Up
Downes Wholesale Nursery are undertaking a massive development of a 145 acre property at Theresa Park in Sydney’s west, developing it into one of the largest wholesale nurseries on the east coast of Australia. This series of articles by Warren Downes deals with what it takes to set up a development of this scale and the advancements in practices and technology involved.
After six months of searching and trying to find a suitable property to expand our increasingly busy nursery, we located a beautiful 145 ace property with over 1km of river frontage on the Nepean river and a 208 mega-litre water license.
Before construction could begin we had to work out a number of factors the biggest of which deals with water. We wanted to ensure a zero run off policy so we can recycle and purify all water run off and set the benchmark for other nurseries to follow with our water conservation policy. One of the biggest obstacles was controlling water flow, as the natural lie of the land did not fall as required. We enlisted the help of Glenn Fordham from TRN Earthmoving who says, “The most significant feature of this job was TRN being able to work with the client to achieve a workable outcome whereby acceptable surface grades were achieved and whilst maintaining a cut/fill balance of approximately 90,000m3 on site. Hence eliminating the need for expensive fill import/export operations. Some areas were able to be graded in a flat plane using conventional lasers. The larger areas had to be shaped to suit existing natural terrains, hence involved using GPS technology to guide the machinery.
That process began by receiving a formatted Digital Terrain Model (DTM) of both the existing surface and indicative proposed works from the projects engineering consultant, Lean & Hayward. TRN’s surveyors then edited that data using 12D Model Engineering Software so the information was suitable for construction purposes and could be viewed by the client prior to construction. The DTM is then transferred to site machinery via Secure Digital Card (or “SD Cards”).
The on-board Topcon 3D GPS software of the machine uses signals from its own GPS receiver. A nearby localised base station and the satellites orbiting above the earth to orientate its blade relative to the design surface and automatically adjusts the position of the blade via the machines electronic/hydraulic system to accuracies of better than 20mm.
The machinery used to execute these works included: Open Bowled Twin Powered Scrapers, Elevating Scrapers, Hydraulic Excavators, Compactors, Graders and Water carts.
Two massive swales over 500m long have been constructed, which will become part of our wetlands area for water purification. Plant species selected will de-silt and strip nutrient build up from the water before it reaches the dam.
The next concern was irrigation; pump stations, irrigation controllers, storm watch protection, weather stations, Piping etc. As there are few nursery projects of this scale in Australia we had to conduct a lot of testing and research with the help of Don Byrne of Hydroplan. We came up with a design for one of the largest pump stations I have seen in any nursery in Australia.
A Grundos pump station was chosen with four Variable Frequency Drive (VFD) pumps. The biggest advantage of a VFD pump is that unlike a conventional pump that simply turns on or off and can send a shockwave of water through your irrigation line potentially causing blow outs, they also produce uneven pressure which can result in uniformity problems with overhead irrigation. A VFD drive works by gradually winding up each pump, in turn increasing pressure to a pre-programmed point and maintaining this pressure as solenoids turn on and off.
Our pump station delivers 800kpa of pressure and a flow rate of 40 litres per second, enabling us to charge of over 3km of pipes in just stage 1 alone. The pump is capable of irrigating 4-5 acres at once of overhead irrigation using low flow irrigation heads a feature that is invaluable for frost protection.
A pump station like this has a lot of electronics components compared to a standard pump station. To protect the pump station from electrical surges that could damage these components, a storm watch system has been installed that measure the electrostatic charge in the atmosphere and can detect lightning from up to 5km away. When lightning is detected it slowly winds the pumps down and then shuts the power off, disconnecting the contactor switches.