1 Xtra Grass for the new Arena Coventry

Xtra Grass for the new Arena Coventry

By Laurence Gale MSc


The Arena, a brand new state of the art multifunctional 32,500-seater stadium, is due to open on the outskirts of Coventry in August 2005. This new stadium will offer and boast an impressive range of facilities including the UK's largest casino entertainment centre, state of the art corporate accommodation and hotel facilities.

The stadium will be the new home of the Sky Blues, Coventry City Football Club who, after 104 years, are leaving their Highfield Road ground.

The Arena Coventry complex will provide the most flexible multi-purpose exhibition, conference and banqueting facility in the Midlands. The £113 million facility has been designed to accommodate a multitude of events both within the fabric of the stadium and out on the playing pitch area.

There is a 6000m² purpose-built exhibition hall which can be sub-divided into two sections, and is column-free throughout. It is designed to be flexible enough to host everything from pop concerts to sporting events, with seating for up to 4500 people. arena-roof.jpg

The architects have installed a number of features to improve the growing environment within the stadium. Over half of the roof has been constructed with see through materials to allow additional light into the stadium. Also, air vents have been constructed within the roof and stand structures to allow greater air movement.

Construction was started on the 1st January 2004 by Laing O'Rourke and is expected to be completed by 1st August 2005. As with most modern stadium pitches, the design brief is to maximise its usage. The pitch area should be able to accommodate many different sporting events and accommodate well over 800 hours of use. And, of course, be playable all year round.

With that in mind George Mullan CEO of SIS (Support in Sport Ltd) recommended that the pitch should be constructed using the latest technologies and products available to support a natural grass constructed pitch. The outcome was a design that incorporated free draining materials, a hi-tech under-soil heating system and one of the latest grass reinforcement systems.

The cost for the pitch construction, undersoil heating and irrigation systems totals about £500,000.

The system being employed at the Arena stadium is Xtra Grass, a patented grass reinforcement system manufactured by Greenfields. This product is a woven artificial carpet that allows natural grass to grow through. The end result is 94% grass and 6% fibre content.


Work on the pitch began in February this year when SIS began the formation of the foundation levels. The site is a former landfill, with heavy clay being the predominant soil present. To overcome this heavy soil structure an intensive primary drainage system has been installed.

The system comprises 65mm diameter lateral primary drains installed at 3 metre centres that run into 165mm diameter main drains. Two 5mm thick geotextile sheets have been laid over the foundation levels to prevent any ingress of toxic landfill materials into the drainage/rootzone layers. To ensure the pitch could drain efficiently a 350mm layer (4000 tonnes) of medium/fine Mansfield sand was installed above the drains, which was then topped up with the final 250mm (1500 tonnes) rootzone layer consisting of a 70/30 soil sand mix.

The under-soil heating system, with over 32,000 metre of pipe work, was laid into the sand base profile. The system runs on heated water.



Formation layer

Geotextile membrane



Laser grading sand layer

Laying rootzone materials



Installing under-soil heating

Installation of irrigation

SIS decided that a reinforced material was required to help stabilise the pitch and give added strength and wear characteristics. They chose to use Xtra Grass, a product they had already had experience with. The company had installed Xtra Grass at Oxford United four years ago and were very happy with the results.arena-carpet-jpg.jpgamage after games is minimal, very light scarring, with no divots to repair. Traditional maintenance methods are not compromised.

Xtra Grass is designed to reinforce the top surface profile of the pitch to a depth of 70mm.The product is a pre formed woven synthetic turf fabric that allows natural grass plants to grow through the woven fabric, thus increasing the strength of the sward in the top 70mm. The synthetic turf fibres are woven into a partially bio-gradable backing, which creates a grid of large uniform voids through which grass plants roots can grow and moisture and nutrients flow. This design feature also allows traditional turf management practises to be carried out (hollow coring, spiking and vertidraining).

The system also allows conventional re-turfing methods, in this case replacing with pre grown turf that has been grown on woven Xtras Grass.

The Xtra Grass normally comes in 150 cm widths, however SIS have now managed to get Greenfield's to supply in 4.5 metre widths, making the job of laying more efficient.

8000 square metres of Xtra Grass have been laid on top of the rootzone layer and top dressed in stages to ensure the artificial grass pile is not flattened during top dressing operations. It is essential to constantly brush during the filling process, this also helps remove any creases and unevenness in the woven carpet materials.



Preparing the carpet

Laying the carpet



Undressed laid carpet

Top dressing



Top dressing in layers

Brushing in rootzone materials

Conditions need to be dry during the top dressing stage. SIS used kiln-dried materials to ensure they moved down easily and quickly into the pile of the carpet. Once the carpet has been laid the next job is to over sow the pitch with approved rye grass cultivars.

SIS has also installed a fully automated watering system, allowing full control over all watering requirements for the new pitch.

Once the grass has germinated SIS will have about twelve weeks to establish and prepare the surface for Coventry City's first home game in August. George is very confident of meeting the timetable, knowing that they achieved good results at oxford with only an 8-week growing in period.

The Xtra Grass system is currently undergoing trials at STRI with several grass plots set up with the Xtra Grass product. SIS are extremely pleased with the concept and are confident that the pitch will stand up to the demands of a modern stadium facility.

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