Introduction the Site

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! The Remediation of Pesticide and Herbicide • Pesticides and Herbicides are a subject rarely tackled by the Contaminated Land for Redevelopment 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

Steve Edgar VertaseFLI Limited

The Site

• 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

• As well as a legacy of use in the “agricultural field” • Raised awareness but limited knowledge and there is the legacy of production understanding lead to a worried and divided local • All industrial chemical processes lead to population contamination of the ground where historic • Objectors used some of the evidence, observations manufacture is concerned and theories presented in Silent Spring to stir • Unique environments beneath these plants has emotion developed • Ironically some of the observations made in the text • Whilst pesticides themselves were the driver for such as ability of ecosystems/organisms to adapt “Silent Spring” ironically the pre‐cursers and actually aided the remediation intermediates presented more risks to the • Difficult for some people to understand the environment as legacy contamination at this site difference between remediation of and application of pesticides BRISTOL | SHEFFIELD | HERTFORD | MANCHESTER BRISTOL | SHEFFIELD | HERTFORD | MANCHESTER

Double Edged Sword.…. Remediating the site

• This remediation is a somewhat controversial project that has • Once the decision was made to close the factory, been impacted by many perceptions work to get to remediation commenced. This is a • Text such as “Silent Spring” can aid our environmental multi stage procedure awareness & I would urge professionals to read these as our – 1. Establish an understanding of the site and understanding of these is key to aiding the public to contamination (CSM) via site investigation understand – 2. Undertake Risk Assessment to establish clean up levels • But……….they can cause alarm to others and cause – 3. Develop a strategy and remediation methodology problems where not intended. The project has been – 4. Undertake remediation works on site impacted significantly by misguided advice from the – 5. Validate the works to allow for re‐development periphery. People in some cases with the best of intensions some using alarmist techniques to pursue agendas.

Site Investigation Conceptual Site Model

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

• Contaminated Land is a Risk Based assessment framework • Originally 217 contaminants relating to the former use identified • Soil and groundwater concentrations used to model risks via • (including DDT, Etc.. identified pathways • 23 Contaminants of Concern shortlisted from the 217 • Assess risks pre, during and after remediation • Organo-phosphates/nitrates – Ethofumesate, Hempa, Schradan, • Main assessed risks are to Human Health, and the Simazine, Dimefox environment (controlled waters) and risks during remediation • Acid Herbicides – MCPA, Mecoprop, Dicamba, Dichlroprop • Phenolics – 2-Methyl-4,6-Dinitro-Phenol, 4,choro, 2 methyl phenol, 2,4,6 • Use literature data for physico‐chemical and toxicological trichlorophenol, Phenol. parameters to generate site specific numbers. Derive EQS in • Solvents - Bis (2 Chloroethyl) ether, 1,2 Dichlorobenzene, 1,2 some cases Dichloroethane, Cyclohexanone, PCE, TCE, DCE, VC, xylene, toluene. • Conclusion is to define risk and establish the degree of • In addition, 30 CNPI identified during remediation. Prochloraz, Dinoseb, remediation required and to shortlist main contaminants of TCMB, various chlorinated phenolics etc etc… concern.

Remediation Strategy

• 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.

Treatment Methodologies – Ex-situ bio-pile Treatment Methodologies – Ex-situ bio-pile with amendments

• 116,561m3 material excavated

• 179 treatment beds • Spent mushroom compost added to many beds to improve soil properties and • Average volume: 617m3/bed aid treatment. • Careful control not to affect • Average treatment bed turned 9 geotechnical properties times • Soils semi cohesive/cohesive and need significant • 1,000,000m3 passed through processing. treatment process • Force ventilation and biofilters used on phenol and • Average treatment time 18 solvent impacted beds weeks up to 30+ in some cases

• Some treatment beds treated utilising ex-situ force ventilation • Particularly effective on DCB, Xylene but also chlorinated phenolics.

N • Highly publicised site and development with a long Site history

• Close to local villages Hauxton and Harston Hauxton • Contaminants with low odour thresholds

• Corby case co-incidental with works Harston

Odour Mitigation Odour Mitigation – VOC Monitoring

Managing odours and Communications the biggest challenge

• 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

Contaminant Mass – Estimates

• Soil COC Mass reduced by greater than 96%

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

Thanks for your time!

Any questions?

Steve Edgar www.vertasefli.com 07973 981780

BRISTOL | SHEFFIELD | HERTFORD | MANCHESTER