Edgar RSC PresentationSteve Edgar 07973 981780. Title: Microsoft PowerPoint - Edgar RSC Presentation.ppt Author: KJONES Created Date: 10/3/2012 4:51:41 PM

BRISTOL | SHEFFIELD | HERTFORD | MANCHESTER

Steve EdgarVertaseFLI Limited

The Remediation of Pesticide and Herbicide Contaminated Land for Redevelopment


Introduction

• As an environmental Student I became aware of the “Silent Spring” as well as other texts such as James Lovelock “Gaia”. Whilst they don’t drive my career this is certainly the kind of thing that got me interested initially!

• Pesticides and Herbicides are a subject rarely tackled by the Brownfield/Contaminated land sector and present challenges as such from may different angles as I hope to highlight

• Important to understand that the legacy of industrial chemical manufacture of pesticides extends well beyond the pesticides themselves!

• The re‐development and thus remediation of sites like this have links in various ways to the likes of Rachel Carson


• Former Bayer Crop Science Site, Hauxton, Cambridgeshire with a long history of manufacture pre Bayer

• Contaminated with agrichemicals, herbicides, pesticides and associated compounds

• Designated as a Special Site under Part IIa of the Environmental Protection Act (1990)

• Primary use post remediation will be residential

The Site


BRISTOL | SHEFFIELD | HERTFORD | MANCHESTER BRISTOL | SHEFFIELD | HERTFORD | MANCHESTER


50 years on……….

• As well as a legacy of use in the “agricultural field”there is the legacy of production

• All industrial chemical processes lead to contamination of the ground where historic manufacture is concerned

• Unique environments beneath these plants has developed

• Whilst pesticides themselves were the driver for “Silent Spring” ironically the pre‐cursers and intermediates presented more risks to the environment as legacy contamination at this site


Carson and Remediation

• Raised awareness but limited knowledge and understanding lead to a worried and divided local population

• Objectors used some of the evidence, observations and theories presented in Silent Spring to stir emotion

• Ironically some of the observations made in the text such as ability of ecosystems/organisms to adapt actually aided the remediation

• Difficult for some people to understand the difference between remediation of and application of pesticides


Double Edged Sword.….

• This remediation is a somewhat controversial project that has been impacted by many perceptions

• Text such as “Silent Spring” can aid our environmental awareness & I would urge professionals to read these as our understanding of these is key to aiding the public to understand

• But……….they can cause alarm to others and cause problems where not intended. The project has been impacted significantly by misguided advice from the periphery. People in some cases with the best of intensions some using alarmist techniques to pursue agendas.


• Once the decision was made to close the factory, work to get to remediation commenced. This is a multi stage procedure– 1. Establish an understanding of the site and contamination (CSM) via site investigation

– 2. Undertake Risk Assessment to establish clean up levels

– 3. Develop a strategy and remediation methodology

– 4. Undertake remediation works on site

– 5. Validate the works to allow for re‐development

Remediating the site


Site investigation: •Boreholes and trial pits installed, samples taken and analysed.

•Important to understand the geology and hydrogeology to enable fate and transport understanding and assessment

•Discovered ground and groundwater contamination

•Surface water contamination also present in adjacent river

•Report written outlining the problems and conceptual site models describing the problems was produced

Site Investigation


Conceptual Site Model


Risk Assessment

• Contaminated Land is a Risk Based assessment framework• Soil and groundwater concentrations used to model risks via

identified pathways• Assess risks pre, during and after remediation• Main assessed risks are to Human Health, and the

environment (controlled waters) and risks during remediation• Use literature data for physico‐chemical and toxicological

parameters to generate site specific numbers. Derive EQS in some cases

• Conclusion is to define risk and establish the degree of remediation required and to shortlist main contaminants of concern.


• Originally 217 contaminants relating to the former use identified• (including DDT, Etc..• 23 Contaminants of Concern shortlisted from the 217• Organo-phosphates/nitrates – Ethofumesate, Hempa, Schradan,

Simazine, Dimefox• Acid Herbicides – MCPA, Mecoprop, Dicamba, Dichlroprop• Phenolics – 2-Methyl-4,6-Dinitro-Phenol, 4,choro, 2 methyl phenol, 2,4,6

trichlorophenol, Phenol.• Solvents - Bis (2 Chloroethyl) ether, 1,2 Dichlorobenzene, 1,2

Dichloroethane, Cyclohexanone, PCE, TCE, DCE, VC, xylene, toluene.• In addition, 30 CNPI identified during remediation. Prochloraz, Dinoseb,

TCMB, various chlorinated phenolics etc etc…

Contaminant Types


• Fully excavate all site materials in order to ensure that all uncertainty regarding contaminants and geological conditions are removed. Also to asses historical bentonite wall and make appropriate decision on its removal.

• To collect further information on geology, hydrogeology and contaminants to further develop the CSM and to refine risk assessment.

• Following options appraisal we determined a suitable treatment train.

• Perched water, groundwater and surface water segregated and treated in onsite Waste Water Treatment Works.

• In-situ methods not appropriate due to geological/hydrogeological conditions.

Remediation Strategy


• 116,561m3 material excavated

• 179 treatment beds

• Average volume: 617m3/bed

• Average treatment bed turned 9 times

• 1,000,000m3 passed through treatment process

• Average treatment time 18 weeks up to 30+ in some cases

Treatment Methodologies – Ex-situ bio-pile


• Spent mushroom compost added to many beds to improve soil properties and aid treatment.

• Careful control not to affect geotechnical properties

• Soils semi cohesive/cohesive and need significant processing.

• Force ventilation and biofilters used on phenol and solvent impacted beds

Treatment Methodologies –Ex-situ bio-pile with amendments


• Some treatment beds treated utilising ex-situ force ventilation

• Particularly effective on DCB, Xylene but also chlorinated phenolics.

Treatment Methodologies –Force Ventilation Vapour Extraction Unit





• Highly publicised site and development with a long history

• Close to local villages Hauxton and Harston

• Contaminants with low odour thresholds

• Corby case co-incidental with works

Hauxton

Harston

Site

N

Other Challenges: Odours


Odour Mitigation


Odour Mitigation – VOC Monitoring


• Initial meeting and presentation to local councillors• Letter to all residents• Detailed discussion with Multi Agency Group• Consultative forum with Politicians and regulators• Drop in days for the local public• Very comprehensive monitoring of odours• VOC 24 hour and 28 day monitoring• Comparison testing in answer to pressure group concerns• Constant liaison with regulators and HPA• Visits and discussions with local people• Detailed communications plans

Managing odours and Communicationsthe biggest challenge




• Soil COC Mass reduced by greater than 96%

• Estimated mass in water similar with a 99%+ removal rate.

Contaminant Mass – Estimates


Thanks for your time!

Any questions?

Steve Edgarwww.vertasefli.com

07973 981780

Documents

Edgar RSC PresentationSteve Edgar 07973 981780. Title: Microsoft PowerPoint - Edgar RSC Presentation.ppt Author: KJONES Created Date: 10/3/2012 4:51:41 PM