Portfolio: Feature Article

Last year we were required to write a feature interview for one of our assignments. I decided to interview Paul Mckenzie and ask him about the constuction of Northala Fields Park in Northolt Ealing. Two years on the park is being used successfully and turning into a perfect habitat for a number of different species. With the warm weather predicted this Summer there is no doubt the park will be used by all:

It is over two years since the Northala Fields of Northolt and Greenfield Park was opened in the spring of 2008 by Ealing council. The park offers a variety of ecological and recreational opportunities to the public.  I visited the park to track its growth over the past two years, and investigate the initial construction process the park went through in the four years it took to create.

Paul McKenzie ACinstCES survey director of McKenzie Geospatial Surveys undertook the leading role in the geospatial engineering of the park. His company specialises in providing land and engineering surveys/setting out for civil and construction industries. It merits itself on years of experience working with the bulk earthmoving sector involved with land redevelopment.

I met with Paul to discuss the process Northala Park went through to reach what it is today. He was first involved in the project at contract tender stage with the company CJ Pryor (contract) ltd in 2002. This required verifying the volumes that would be required to create the shapes as shown on the initial design for the park. The initial process also involved having an appraisal meeting with Ealing Borough council to discuss how the park would be constructed between the various contractors with their bid. Paul explains;“I was quite taken back by the initial designs because it involved the creation of four very large conical mounds on a flat landscape.” The tallest of which would be approximately 26 metres. These mounds would be the largest of their kind in Europe. After he was awarded the construction bid of the project, many tasks had to be undertaken before any construction could actually begin.

Working closely alongside Ealing Borough Council Paul was able provide drawings and a clear visualisation of what the completed park would look like, in order to seek the approval of the local residents. This was done by the production of 3D DTM (digital terrain models) that could be interacted with and displayed at a residents meeting. This helped to answer the vast number of questions regarding what the park would look like, as the residents found it hard to understand the 2D drawings and contours that Paul had produced for engineering purposes.

The park strives on being completely self funded. This was achieved by utilising the import of approximately 65,000 lorry loads of inert waste material, “equivalent to filling 240 Olympic size swimming pools.” The deposition of the material then gained revenue from the charging of the tipping. This then generated enough money needed to create the park. This material came from various demolition and Brownfield sites, “including the old Wembley StadiumWhite City and Heathrow terminal 5.”

Control is an important aspect when placing all the material to create a landform and it would be a difficult process if all the material was deposited too quickly, however “thankfully the material was tipped over three years of construction.” To make the job easier Paul conducted a complete accurate land survey of the cleared site prior to topsoil strip using Trimble RTK GPS, with an interchangeable 4800 and 4700 base and rover setup (now upgraded to Network Glonass R6). As the site encompassed approximately 49 acres, a control network had to be established around the perimeter of the site and tied into a local grid system. In addition to this the ordnance survey national projection and datum geoid was computed by post processing the static and Rinnex data. The OGL (original ground level) survey allowed him to provide the earthmoving team with depths of fill information to enable the job to be packaged into manageable phases.

The design elements of the park are complex and the whole design drawing had to be imported from the architect’s CAD files which were in 2D, this then meant that Paul’s “ job consisted of converting these to 3 dimensions prior to setting out.”

A combination of RTK GPS and Trimble robotic total stations, then allowed him to set out the 3D strings and DTM levels from elements of the digital design. Profiles, batterails, road pins and real time level dips were used to guide the earth moving team.

From listening to Paul it is clear that the job was not simple in anyway, he says “the construction of the conical mounds was a challenge.” The material, as it was being placed progressively to the top of each mound would create boulders that rolled down the 1in3 gradient slopes and would then destroy the site batterails which radiated out from the centre. This required constant rechecking and engineering from both Paul and the rest of the team. Another important aspect discussed was the design features on the 2D architect’s plans, these were not feasible to construct on the 3D shape, this then meant Paul was faced with the job of completing some in house redesign of some of the radiuses’ and alignments. He insists; “little on the job was a straight-line!” An example of the in house design is the redesigning of the spiral mound so that it both looked correct from a birds eye view and worked as a mathematical and geometric figure that fitted on the 1in3 slopes.

According to Paul with other projects that he has worked on the use of automated machine control technology can prove to make the job much easier “In a nutshell for Northala, the 3D design could have been uploaded into the plant operators on board computer for their in the field guidance.”

From visiting the park this year and last it is obvious to me that all the features of the park are being used by the local community especially recently due to the arrival of the summer months. The park is proving to be a successful recreation area despite initial shocks Paul said he had with the drawings. The park boasts 2 car parks constructed from completely recycled materials, various natural and modern children’s areas, 6 fishing lakes, a model boating lake which is all fed from a ground water bore hole and swales and flood compensation zones to control the increased surface water. Along with ecology reed beds, a grass amphitheatre and approx 2.25km (in plan) of gabion basket walls.

All these features and more, are connected by a comprehensive network of interconnecting paths, including the 850 metre long spiral path leading to a panoramic view point on the highest mound in the park. Needless to say all this required the professional setting out services of Paul McKenzie.

It is fair to say that Paul has definitely left his impression on the park. He believes that “the Geospatial aspect often gets overlooked in the final celebration of creations such as Northala Park in the construction industry.” However by the nature of the 4 large landscaped mounds next to the A40 London, he would like to think that commuters and recreation goers ponder over how it came to be shaped, “like the pyramids of old.” But from what I can see today, “Northala Park definitely belongs to the public.”

In November 2008 the park was announced as overall winner in the design (over 5 hectares) category at the Landscape Institute Awards.

For further information contact Paul Mckenzie, AmICES, McKenzie Geospatial Surveys Limited,www.mackasurveys.co.uk

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One Response to “Portfolio: Feature Article”

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  1. Surveying the mounds « Blog it - May 9, 2010

    […] Portfolio: Feature Article […]

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