Dan Bundy Duncan Miller Chris Marshall

Introduction North Lanarkshire (near Glasgow) Brown-field site of decommissioned sewage treatment works Site to be developed into 3 acre business park Contaminated land requiring specialist treatment Economic development potential of the site North Lanarkshire given £6m to support the remediation scheme of vacant, derelict and contaminated land in the area

The problem 4700m 3 of sludge contained in 5, 12.2m dia., 9m deep tanks High concentrations of hydrocarbons, heavy metals and organics Secondary investigation revealed presence of asbestos

Constraints Direct landfill disposal of organics prohibited – risks associated with leachate and methane Specialist treatment required for asbestos – hazardous substance requires self-containment Access and lack of working space to lower tanks Back fill areas of excavation

The Options - 1 Solidification/Stabilization process Thermal pre-treatment 180 °C (ensure hydrolysis) Remove high moisture content of organics Asbestos cell disposal

The Options - 2 Drying solidification technique Adding dry binders Or applying centrifuges/belt presses Disposal into asbestos cell Agreement with SEPA derogating the organic content

The Options - 3 Solidify with binding agent Retention and re-use as backfill Best Environmental Technique (BET) Complex regulation and ensuring material strength

Adopted solution Option 2, with the use of a cementitious binding agent Most economic Least risk considering unknown nature and quantity Disposal of organically rich material into asbestos cells providing sufficient solidification

Problems encountered Contractual problems > Delays > Change in plant Long-reach excavator mixed set volumes of sludge and binder During the project a partial steel lid and associated structures were found at the base of tank 3 Cavity wall void later found to be 600mm wide (not 50mm) Discovery of a further three 9m deep chambers adjacent to the top 3 tanks

Future for site Remediation removed site from Contaminated Land Register Infrastructure improvement in preparation for business park Owner occupied office space and commercial developments to come