1. Dan Bundy Duncan Miller Chris Marshall

2. 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

3. 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

4. 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

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

6. 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

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

8. 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

9. 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

10. 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