Pride Park, DerbyPride Park, Derby

Nick Graham and

Kevin Hargreaves

IntroductionIntroduction

• 800,000m2 site, east of Derby city centre

• Enclosed by River Derwent and the railway

• Hosted a gasworks, unlicensed landfill and heavy engineering works

• Site was left heavily contaminated• £17.5m from government’s urban

development strategy, City Challenge

• Flat land → surface water drainage problems and risk of flooding

The ProblemThe Problem

• Parts of the gasworks and engineering works still remained

The Problem…The Problem…

• Heavily contaminated soil from past users– An unknown cocktail of

chemicals

• Methane gas being emitted from landfill site

• Surrounding land and river suffering from cross contamination

Possible SolutionsPossible Solutions

• Dig & Dump– Very large site, lot of

transport– Wouldn’t solve the problem

• Gas venting trenches– Methane is continuously

produced from landfill

Possible Solutions…Possible Solutions…

• Pump & Treat– Not effective alone

in long-term– Large site so need

containment barrier

• In situ bio-remediation

• 800 soil samples taken and tested for 22 different contaminants

The SolutionThe Solution

• Reclamation strategy developed by Arup to make site “suitable for end use”– Combination of possible solutions were used– Contain contaminants– Clean-up soil– Raise land level to reduce flooding risk

• 3km bentonite slurry cut-off wall– Up to 10m deep– 2mm HDPE membrane– Completed Dec. 2004

• Provision of a groundwater treatment plant– Abstraction wells around perimeter– Treat water and pump back in

The Solution…The Solution…

• Gas vent trench adjacent to existing landfill

• Two on-site, fully engineered, waste repositories

The Solution…The Solution…

– Contains excavated soil from site– Prevents removal off-site (shifting the problem)

• Use of "site won" and imported material to raise land– Pulverised fly ash

from local sources used as sustainable and cost-effective solution

The Solution…The Solution…

• Flood bund adjacent to the river

• Graded stone isolation layer or capillary break blanket

The Solution…The Solution…

• Land sold at market value (but with guarantee of no future problems), no council subsidies– £20m

The OutcomeThe Outcome

• Total cost to council (buying, reclaiming, infrastructure)– £50m

The Outcome…The Outcome…

• Council will breakeven in the future from high business rates from restaurants, retail, etc

Thank you for listening!