Pride Park, Derby Nick Graham and Kevin Hargreaves

Introduction 800,000m 2 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 Problem Parts of the gasworks and engineering works still remained

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

Gas vent trench adjacent to existing landfill Two on-site, fully engineered, waste repositories 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… Flood bund adjacent to the river Graded stone isolation layer or capillary break blanket

The Solution…

Land sold at market value (but with guarantee of no future problems), no council subsidies –£20m The Outcome Total cost to council (buying, reclaiming, infrastructure) –£50m

The Outcome… Council will breakeven in the future from high business rates from restaurants, retail, etc Thank you for listening!