From power station to data centre: the carbon story hidden beneath Skelton Grange

Concrete recycling, groundwater treatment and reuse, and steel recovery are among the measures being used by Howard Civil Engineering to reduce the environmental impact of redeveloping Skelton Grange, a former coal-fired power station site near Leeds, UK.

The 48-acre site, where the power station was demolished in 1998, is earmarked for a proposed Microsoft hyperscale data centre campus. Howard Civil is principal contractor for the earthworks, demolition, remediation and infrastructure works.

Dr Nathan Wood, senior scientist and carbon co-lead, and Dr Aaron Yeardley, science team co-lead, discuss how consultancy Tunley Environmental has worked with the contractor to assess the carbon savings and reductions in resource use associated with these activities, using site data.

Impact of brownfield redevelopment

Reusing brownfield land can help reduce the need to develop greenfield sites and may support the protection of existing natural habitats.

Where appropriate remediation and design measures are in place, brownfield redevelopment can contribute to a more responsible use of land and resources.

The catch is that unlocking that land is carbon-intensive work. It involves deep excavation, demolition, dewatering, and moving thousands of tonnes of material. All of which generate emissions long before anything building works.

On a legacy site like Skelton Grange, the challenge is bigger still: buried basements, deep made ground, old mine workings, sludge beds and localised contamination must be dealt with. One single operation here involved demolishing a turbine basement roughly 130 m long, 80 m wide and 12 m deep.

Research shows that a significant proportion of a development’s environmental impact can arise during these upfront enabling works.

The question, therefore, is not whether these works have an impact, but how effectively that impact is managed and reduced.

At Skelton Grange, three aspects of Howard Civil’s approach stand out.

Concrete that never leaves site

Demolition produces enormous volumes of old concrete. The standard approach is to truck it off to a recycling centre or landfill, then truck virgin aggregate back in from a quarry, a carbon and cost on both journeys.

Howard Civil does the opposite. A mobile crusher processes the concrete on site, turning one waste stream into three usable products (6F2, 6A and Type 1) that go straight back into site roads, drainage and sub-base, this means that very little leaves site.

The saving is estimated at around 19 kg of CO2e per tonne of material reused*. At 10,000 tonnes that’s roughly 189 tonnes of CO2e avoided, which is roughly equivalent to taking 44 cars off the road for a year. It also means less quarrying, fewer HGVs on local roads, and less landfill.

Water that works twice

Groundwater is one of the defining challenges on brownfield sites, both because legacy contamination must be contained, and because construction itself is thirsty.

Rather than pumping and dumping, Howard Civil runs a closed-loop lagoon system. Water is drawn from the old basement voids, cleaned through sediment removal, aeration and settlement in lined lagoons, then continuously tested against Environment Agency standards before any controlled discharge to the River Aire.

So far, over 100,000 m³ of groundwater has been treated this way.*

The treated water is reused on site for drilling, grouting and dust suppression, cutting the need for mains water and tanker deliveries, and helping protect flows in the Aire catchment.

Steel that stays in the loop

On some brownfield sites, buried metalwork and other below-ground obstructions may remain from previous industrial or commercial uses.

Where such materials are left unmanaged, corrosion or associated coatings may contribute to localised ground-quality risks.

Howard Civil segregates structural steel during demolition and sends it to certified recyclers, feeding lower-energy secondary steel production rather than virgin manufacturing.

Timber and other metals are sorted for reuse too, keeping material out of landfill and in circulation.

Measuring what usually goes uncounted

Some of the environmental benefits created during enabling works are difficult to capture through standard company carbon reporting.

Fuel use, purchased materials and waste are usually recorded, but the benefits of reusing materials, reducing transport and avoiding new resources can be less visible.

Tunley Environmental has worked with Howard Civil Engineering to assess these project benefits using site data.

This includes reviewing how much concrete has been reused, how water has been treated and used again, and where recovered materials have been sent.

The assessment compares the approach taken at Skelton Grange with what may otherwise have happened, such as removing concrete from site and importing virgin aggregate.

This promotes understanding of where site practices have reduced waste, transport movements, resource use and associated carbon emissions.

It provides Howard Civil with a clearer evidence base for client reporting, future tenders and strategy on other projects.

It also helps identify which practical actions deliver the greatest environmental benefit and where better site data could support more accurate measurement in future.

_{*Figures are estimates based on recognised industry databases (e.g. ICE, DESNZ, OneClick LCA) investigated by Tunley Environmental.}