Book Description

NOTE: THIS IS A DOWNLOAD - FOLLOW THIS LINK TO PURCHASE THE PAPER VERSION.

Since the 1970s, hundreds of thousands of cubic metres of disused mine workings have been successfully stabilised by filling with grouts based on pulverized-fuel ash (PFA) and Portland cement. Similar volumes of disused workings will need to be filled in coming years as land is developed. This environmental code of practice provides guidance on selecting environmentally compatible and cost-effective materials and techniques, with authoritative guidance on good practice, based on information in the literature, laboratory studies at BRE, data from the use of pfa grouts and expertise from an industry steering group. It was first published in 2006, and has been revised to ensure consistency with recent developments, in particular, a new quality protocol for PFA, developed by WRAP and the Environment Agency in partnership with industry. (51 pages)

A report (BRE Report 220192) on a detailed BRE laboratory study to assess the leaching characteristics, permeability and physical properties of pfa grouts is included on the accompanying CD Rom (on a ZIP file for downloads). It draws on field experience, and includes a review of groundwater risk assessment models and a specification for mine infilling works.

Contents

Acknowledgements. List of figures. List of tables

1 Introduction

Background.
PFA production and use.
Advantages of using PFA grouts in remediation works.
The regulatory context for the COP.
Potential contamination of groundwater

2 Overall assessment methodology

3 Conceptual model for the release of leachates to groundwater

Background.
Source-pathway-receptor concept.
Water quality limits.
Groundwater source protection zones

4 Preliminary risk assessment

Introduction.
Overall preliminary risk assessment.

5 Simple risk assessment

General.
Leachate composition and required dilution factors.
Extent of leachate dilution available from groundwater.
Estimation of dilution factors.
Assessment of risk

6 Complex risk assessment

Conceptual model for complex risk assessment.
Groundwater risk assessment models

7 Assessment and characterisation of the site
Introduction.
Size of void.
Hydrogeology.
Groundwater

8 Assessment of material properties


Introduction.
Assessment of PFA/cement grout mixes.
Materials variables that can be used to control release from PFA grout

9 Engineered measures for minimising contamination of controlled groundwater
Control of the groundwater regime.
Engineered barriers

10 Guidance on site practice

Safety.
Nuisance.
Storage of materials.
Grout mix.
Backfilling boreholes.
Cost of filling operations

11 Guidance on environmental monitoring during and after filling

Approaches to monitoring.
Monitoring groundwater - quality and flow.
Groundwater monitoring devices

12 Assessment of other risks associated with the use of PFA grout

Events potentially leading to environmental risk.
Risk screening

13 References