Utilities

Football stadiums and waste transfer stations are not exactly the most obvious of bedfellows. Indeed, Arsenal football club is only managing to build its £220m stadium near its existing grounds at Highbury, north London, because it usurped the site of an existing waste transfer station.

To compensate, Arsenal has had to build a brand new waste and recycling centre for the North London Waste Authority one mile west of Highbury. According to acoustician Steve Arnold of WSP Environmental it was “an absolute Rolls-Royce of a job”, with a construction cost of £40m – higher than that of most new football stadiums.

Arnold was responsible for tackling the key challenge of the project, which was to suppress the cacophony created by heavy dust carts, container trucks, heavy-duty waste compactors and air-handling units. This was the stipulation laid down by Islington council as part of planning permission. The big problem was that the site for the facility was embedded in a high-density area of existing and new housing along with a primary school, and their occupiers were quite understandably up in arms about acquiring such a rubbishy new neighbour.

The building is arranged over three main floors on a steel frame and designed to handle 1100 tonnes of domestic and commercial waste a day. Dust carts drive in at the top floor level and tip their contents down seven hoppers into compactors in the basement, and from there at one end into large container lorries. Once the waste containers have been filled, the lorries trundle off to the incinerator at Edmonton or landfill sites. The top floor also accommodates bays for recycling paper, glass, tins and plastics, all of which have to be separated at source. The middle floor, which is at ground level, is a dust-cart maintenance depot and filling station.

The most obvious sound reduction measure would have been to seal the entire building envelope, but this was ruled out by the constant throughput of heavy vehicles. Instead, some 1400 acoustic baffles have been hung from the ceilings of the two vehicular halls in the building to absorb the noise. Measuring 1 m by 600 mm and 100 mm thick, the baffles consist of mineral fibre wrapped in protective plastic sheet and sandwiched between perforated galvanized steel plates.

More predictably, the building envelope is specified for 40 dB sound reduction. The cladding to the external walls is made up of composite metal-faced panels 125 mm thick and stuffed with Rockwool mineral-fibre insulation. The trick here was to ensure that panels suppressed noise at several frequencies down to the low rumble of heavy diesel engines. Rannila panels made by Rautaruukki were deemed to fit the bill.

The roof and side wall are covered with Corus’ Kalzip galvanized-steel standing-seam sheeting backed by more acoustic mineral-wool insulation. There is even a small stretch of green roof that was also based on Kalzip’s sheeting and planted with sedums overlooked by the top-floor offices and neighbouring flats.

The building’s other big noise generator is the intensive ventilation system, which is distributed by four huge metal ducts measuring 4 × 1 m in section. The critical points are the huge extract vents at the end of the ducts that discharge exhausted air, along with the noise of internal fans, into the open air. To suppress the noise, the extract vents have been screened off from neighbouring buildings, and this led to a contorted arrangement of ducts. The nine huge vents visible on the east side of the building are actually relatively noiseless air intakes: the extract vents discharge into a 2 m deep trough sunk into the flat roof.

Atmospheric pollution of fumes, smells and dust and fire risk are the other main hazards of a building dealing with loose refuse and heavy traffic. Dust is suppressed in the waste chutes by fine water sprays. For the comfort of the 200 people working in the building, contaminated air is filtered and exhausted by the mechanical ventilation system at up to six air changes an hour.

In the event of a fire, the ventilation system can be boosted to the rate of 10 air changes an hour to remove smoke. The ducts were fabricated by Senior Hargreaves with a double insulated skin of galvanized steel with a four-hour fire resistance. Sprinklers were also installed to suppress fires.

With all these environmental controls, Islington’s new waste transfer centre achieved a “very good” rating in BRE’s Environmental Assessment Method.

Perhaps the one missed opportunity is that the compacted waste is not transferred by the relatively safe railway transport network that runs alongside it. A small consolation is that the building’s layout allows for such a link to be made at a later date.

Project team

client North London Waste Authority
developer Arsenal Football Club
employer’s agent, project manager, quantity surveyor and services engineer AYH
architects Sheppard Robson, Robinson Architects
environmental consultant WSP Environmental
structural engineer Price & Myers
design-and-build contractor Sir Robert McAlpine