CONTAMINATED LAND OVERVIEW

Summary

• Introduction.• Brief Introduction to the Legislation.• Phase 1 (Preliminary Risk Assessment -PRA).

• Phase 2 (Geo-Environmental Investigation).• Phase 3 (Remediation).• Completion Report.

Introduction

• Historical Legacy.• Brownfield sites.- Government policy to use

60% of Brownfield sites for new developments.

- To protect existing Greenbelt.

- As part of there affordable housing scheme.

• Part 2A put into the EPA 1990 to protect humans and the environment.

Legislation

• Definition of Contaminated land (Environmental Protection Act 1990: Part 2A).

“Contaminated land” is any land which appears to the local authority on whose area it is situated to be in such a condition, by reason of substance in, on or under the land, that:

(a) Significant harm is being caused or there is a significant possibility of such harm being caused; or

(b) Significant pollution of controlled waters is being, or there is a significant possibility of such pollution being caused.*

* The Water Act 2003 has modified the EPA Act 1990 in line with contaminated land.

Legislation

• Regulators/Statutory Consultees- Human Health is the Local Authority.- Controlled Waters is the Scottish Environment

Protection Agency.- Ecological Systems is Scottish Natural Heritage.

• The local Authority would liaise with these as part of any determination.

Legislation

• Development requirements to satisfy planning.- PPS23 and Building Control C.- Compliments Part 2A through planning.- Ensure site will not be determined under Part 2A in the

future.- Ensures development is protective of human health,

controlled waters, ecology and buildings.• PPS23 and Building Control C requires as a minimum a Phase 1 (Preliminary Risk Assessment) and a site walkover.

- CLR11 guidelines from the SEPA / Environment Agency (technical framework for CL decision making).

Legislation

• CLR 11- Risk Assessment (source/contaminant-pathway-receptor

model).- Option Appraisal.- Implementation of the Remedial Strategy.• Risk Assessment required to determine if the site poses a risk to site users and surrounding environment (Phase 1 and Phase 2 studies).

• Options Appraisal examines what remediation is likely required for the site.

• Remediation and completion report cleans up the site and demonstrates to the regulator that the site is “suitable for use”.

Phase 1 (PRA)

• Required as a minimum as part of a planning application.

- Also useful to do for pre-purchase (know what you are buying).

• Desk Based Study.- Historical mapping.- Geology.- Hydrology and hydrogeology.- Landfill search.- Environmental search.• Site Walkover.• Preliminary Risk Assessment and Conceptual Model.

• Recommendations.

Phase 1 (PRA) – Desk Study

Phase 1 (PRA) – Desk Study

Phase 1 (PRA)- Environmental

• Landfill search.• Flooding.• Waste management licences.• SEPA / IPPC Permissions.• Registered radioactive substances.• Discharge consents / abstraction licences.• Pollution incidents.• Main rivers.• Water quality.• Groundwater source protection / vulnerability.• Radon.• Ground instability / subsidence.• Trade directory.

Phase 1 (PRA)- Site Walkover

• Walk over surveys should be carried out:– After the initial desk study.– Before the site investigation design phase (if required).

• Walkover survey should identify things like:– Potential contaminant sources.– Potential contaminant pathways.– Potential contaminant receptors.– Identify any access problems.– Identify any unusual features.

Phase 1 (PRA) - Conceptual Model

• The aim of the conceptual model is to provide a preliminary assessment of the likelihood of a pollutant linkage for each potential combination of contaminant, pathway and receptor (from desk study). A conceptual model can be used to make an informed decision on the contamination risks associated with the site and whether further site investigation work is required.

• Contaminant-Pathway-Receptor linkages (CLR11).- ‘Contaminant’ – a substance that is in, on or under the land and

has the potential to cause harm or cause pollution of controlled water.

- ‘Pathway’ – a route or means by which a receptor can be exposed to, or affected by, a contaminant.

- ‘Receptor’ – something that could be adversely affected by a contaminant, such as people, an ecological system, property or water body.

- If one of the pollutant linkages is not available there is no risk.

Phase 1 (PRA) - Conceptual Model

Phase 1 (PRA) - Conceptual Model

Potential Sources (examples)

Potential Contaminants(examples)

Potential Pathways(examples)

Potential Receptors (examples)

Made ground on siteMade ground offsiteCoal MeasuresFormer industrial activity

Metals / MetalloidsInorganic compoundsOrganic compoundsAsbestosLandfill gasNatural gas

Direct contactIngestionInhalationSurface run-offInfiltrationEvaporationGroundwater flowMigration through permeable strataMigration through service trenches / ducts

Future residentsFuture site usersBuildingsEcologyControlled watersAquifer

Phase 1 (PRA) - Recommendations

• Based on these findings recommendations can be given, such as:

- Site investigation.- Watching brief.- No requirements, no previous use on site.

Phase 2 – Site Investigation

• The site investigation should establish the contamination condition of the site based on the Preliminary Conceptual Model (PCM) in the Phase 1 report and can involve:

- Designing an appropriate site investigation based on the PCM.- Undertaking appropriate sampling and analysis (water, soil

and gas).- Undertaking a Generic Quantitative Risk Assessment (GQRA),

based upon typical land uses.- Refining the Preliminary Conceptual Model, based upon the

finding of the Site Investigation.- Providing an Options Appraisal on appropriate remediation (if

required).- Providing recommendations on further work, such as

delineating hotspots or Detailed Quantitative Risk Assessment (DQRA) for either non-standard land uses or more site specific data using mathematical models (such as, CLEA UK).

Phase 2 – Site Investigation

• The sampling strategy for any phase of intrusive investigatory fieldwork should identify the following (BS10175):

- The objectives of the investigation and the possibility of zoning the site.

- The location, pattern and number of sampling point (targeted and random).

- The depths from which the samples should be collected, the samples to be collected and any monitoring requirements.

• The investigation may allow for sampling:- Soils.- Water (groundwater and surface water).- Gas.- Geotechnical samples.• For Planning get LA approval before you start the SI.

Phase 2- GQRA (Human Health)

• Generic Quantitative Risk Assessment is based on four generic land uses and values are based on conservative assumptions.

- Residential with plant uptake (housing with gardens – 0-6yr old child).

- Residential without plant uptake (flats/apartments – 0-6yr old child).

- Allotments (0-6yr old child).- Commercial/Light Industrial (16-59 yrs working life).• Soil results are compared to generic values.- Soil Guideline Values (SGVs).- Generic Assessment Criteria (i.e. LQM or ATrisk).• CLR7 Statistics can be calculated.- Must have enough samples to allow zoning of site and have

analysed similar material.

Phase 2- GQRA• Gas monitoring- Needs to be undertaken under falling barometric

pressure.- Usually minimum of 6 visits over 3 months.- Gas Screening Values (GSVs) calculated.- Results compared in C669 and BS8485.• Water Monitoring- Depends upon the Preliminary Conceptual model.- Boreholes can be sampled to measure shallow groundwater.- Rivers, culverts or lakes for surface water.- Results compared to UKDWS, EQS, SWADs depending upon the

receptor.- Any contamination the SEPA will need to be contacted.• Update your conceptual model.

Phase 2- Options Appraisal

• We have contamination what do we do about it?- Further sampling to delineate hotspots.- Detailed Quantitative Risk Assessment (DQRA).- Remediation options in brief.- No remediation required (a rarity on Brownfield sites).

• The Phase 2 Report should be sent to regulators of concern (LA, SEPA, Scottish Natural Heritage).

- For problematic sites a Remediation strategy will be required on the actual remediation that will be undertaken (in more detail).

- Set up a meeting with all parties of concern to agree the way forward for your site (usually for problematic sites).

Phase 3- Remediation

• Human Health linkages - Usually relatively inexpensive to break.- Clean soil cover system and capillary (breaks dermal and

ingestion).- Proprietary gas membrane (vapour and gas) correctly installed.• Ecological- Variable expense depending upon ecological type (rare receptor

type)- Bats, Great crested newts, SSSI, SBI etc• Controlled Waters- Primary reason for expensive remediation.- Due to wide spread contamination (Aquifer and surface water)- Likely to effect offsite receptors.

Completion Report

• Completion Report- Details all remediation undertaken with evidence that

this has been done correctly and site is ‘suitable for use’.

- Photographic and analytical proof of all remediation.- Involves post remediation testing (if required).- Soil sampling of all imported soil for gardens and

landscaping.- Details of gas protection validation.- Details of any special requirement for water pipes.• Contaminated Land Conditions may then be discharged.

• May need to do this for NHBC sign-off as well.

Any Questions?