Cleaning Up Cornwall. Ian George Hyder Consulting (UK) Limited. Hyder Consulting

Transcription

1 Cleaning Up Cornwall Ian George Hyder Consulting (UK) Limited Hyder Consulting

2 Have you got a problem with TBT?

3 You don t t need to do this!

4 The Problem with TBT Introduced to replace DDT and arsenic Main problem is the persistence in marine environment Linked to high mortalities of oyster larvae and shell malformations Female dogwhelks develop imposex - sterility follows Now sterilising marinas and harbours worldwide, with increasing environmental control

5 There are ways of dealing with it!

6 Case Study British Nautical Society Award 2003 Honda Sustainability Award Mylor Yacht Harbour Development Consultant: Hyder Contractor: Envirotreat & Marine Civils

7 Mylor

8 Admiralty Quay Dredged to 2.5mCD

9 The Problem Silts were contaminated: Organic tin compounds (TBT) & Heavy metals Could not go to sea & disposal cost to land very high Few landfill sites in the UK could accept nearest 200 miles away at Swindon Not enough space in Admiralty Quay The Solution Ex-situ Stabilisation/Solidification Reduce Hazard potential of waste Render the soft wet silts to an engineered fill Work regulated by Mobile Treatment Licence Re-Use under Para 19a Exemption Dig out Quay Area

10 The Consulting Process Discussions with Environment Agency & English Nature at early stage Broad agreement regarding process, location of beneficial use area and constraints obtained Marine Civils Contractor appointed with Envirotreat as Subcontractor E-clay solution using various reagents trialled Site Specific Working Plan agreed with EA Job starts From Testing to agreement - all within 5 weeks!

11 The Construction Process Silts dredged within inner harbour area using land based and marine plant Transported to mixing zone container in excavated pit E-clay and cement mixed with bucket of excavator Samples taken for analysis Mixed material taken to reclaimed area behind recycled block wall 28 days later hard enough for car parking

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14 The Outcome Leachate testing carried out following NRA methodology Samples taken every 10m 3 initially Dredged area and new car park completed on programme Leachate tests indicate <0.1ppm TBT conc. No ongoing liability with client Happy client

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16 Case Study Brownfield Briefing Awards Winner 2006 Best Chemical Stabilization Regeneration of Newlyn Harbour, Cornwall Consultant: Hyder Contractor: May Gurney

17 Newlyn

18 Small Boat Pontoons Reclamation Area Sandy Cove

19 Dredged to 2mCD Dredged to 0.75mCD Dredged to 0mCD

20 The Problem Silts were contaminated: Organic tin compounds (TBT) & Heavy metals Could not go to sea & disposal cost to land very high Few landfill sites in the UK could accept nearest 200 miles away at Swindon Dig and dump was not a sustainable solution (and 2M was a project NO GO ) The Solution Ex-situ Stabilisation/Solidification Reduce Hazard potential of waste Render the soft wet silts to an engineered fill Work regulated by Mobile Treatment Licence Re-Use under Para 19a Exemption

21 The Consulting Process Discussions with Environment Agency & English Nature at early stage Broad agreement regarding process, location of beneficial use area and constraints obtained Contractor appointed with requirement to have Mobile Plant Licence Contractor reimbursed costs of testing to determine most efficient treatment (12 mixes trialled) Site Specific Working Plan agreed with EA Section 19a exemption agreed Job starts

22 The Construction Process Materials were excavated using excavators from shore and on barges Transferred across harbour in 20t wagons Mixed on site with Cement Placed on Sandy Cove Piles driven and pontoons floated in

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24 The Outcome Success measured by leachate testing, not totals A monolithic mass is produced, with reduced permeability and reduced surface contact The NRA leach test, where material is broken down to <5mm was the benchmark the precautionary principle Raised ground levels for new development area

25 Leachate Results for Copper After 14 and 28 Days Leachate Results for Copper After 14 and 28 Days Copper (ug/l) Target 5 ug/l Mix 1A Mix 1B Mix 2A Mix 2B Mix 3A Mix 3B Mix 4A Mix 4B Mix 5A Mix 5B Mix 6A Mix 6B Mix Number 14 Days 28 Days Target

26 Leachate Results for Nickel After 14 and 28 Days Leachate Results for Nickel After 14 and 28 Days Nickel (ug/l) Target 30 ug/l Mix 1A Mix 1B Mix 2A Mix 2B Mix 3A Mix 3B Mix 4A Mix 4B Mix 5A Mix 5B Mix 6A Mix 6B Mix Number 14 Days 28 Days Target

27 Leachate Results for Tin After 14 and 28 Days Tin (ug/l) Target 10 ug/l Mix 1A Mix 1B Mix 2A Mix 2B Mix 3A Mix 3B Mix 4A Mix 4B Mix 5A Mix 5B Mix 6A Mix 6B Mix Number 14 Days 28 Days Target

28 Key Benefits Majority of leachable contaminants reduced to below EQS Sea Water Standard All contaminated materials were used to benefit & in the planned manner Solidification/stabilisation conditioned the hitherto loose, soft harbour silts into material with good engineering characteristics with CBR > 3% and once placed provided a foundation with reliable bearing capacity

29 Conclusions Understand scale of the problem ( depth and breadth) Understand the legislation Start talking early to statutory consultees Identify suitable reception area Clearly define roles and responsibility in tender documents Work with the Contractor, SA s and client Involve consultees in site operations Keep good records

30 Cleaning Up Cornwall Ian George Hyder Consulting (UK) Limited Hyder Consulting

31 Validation Contaminants US95% EQS Seawater Standard As B Cd Cr Cu (fresh water 5 112) Pb Hg Ni Zn Ag 1 Ba Fe Sn Samples of production treated silts were subject to NRA leach test V Tributyl tin < Triphenyl tin <