Site Investigation – The Holistic Approach: A Case Study from Providing Ground Solutions Approach: A Case Study from Silvertown, London Sarah Key, CEnv MIEnvSc , Principal Engineer Nick Langdon, CEng FICE, Company Chairman
Site Investigation – The Holistic Approach: A Case Study from
Providing Ground Solutions
Approach: A Case Study from Silvertown, London
Sarah Key, CEnv MIEnvSc , Principal EngineerNick Langdon, CEng FICE, Company Chairman
Introduction
Why a holistic approach?The developmentSite history and previous usageSite investigation 2013
cgl-uk.com 2
Site investigation 2013Remediation outcomesGeotechnical outcomesThe site today
Why a holistic approach?
A balancing act
The constraints• The professional team diktats • Client preferences
cgl-uk.com 3
• Client preferences
The drivers• Reduced disruption• Coordination of design thinking• Cost reduction
The site
38-acre site£1b+ to create 3300+ new homes, infrastructure, commercial and amenity facilities
Silvertown, London
cgl-uk.com 4
20,000m² of commercial space is to create around 20,000 jobsA new economic centre east of Canary Wharf, minutes from London City Airport and CrossrailCompleting 2019/20Silvertown Quays….starting 2018
Development summary
Silvertown, London
Oxley Holdings Limited A Singapore based developer
cgl-uk.com 5
Ballymore Properties Limited Founded in Ireland in 1982
Minoco Wharf + Crescent Wharf + Venesta Wharfs
Historical summary
1799: Marshland
Over 200 years of history
cgl-uk.com 6
Historical summary
1894: Industrial development
Over 200 years of history
cgl-uk.com 7
Goad Plans
cgl-uk.com 8
London’s Biggest Explosion
Friday, 19 January 1917 at 6.52 pm.Approximately 50 tons of TNT exploded.73 people killed and 400 injured.Debris was strewn for miles
cgl-uk.com 9
Debris was strewn for miles around damaging a gasholder on Greenwich peninsularBlew windows in the Savoy Hotel and almost overturned a taxi in Pall Mall.The fires could be seen in Maidstone and GuildfordThe blast was heard up to 100 miles (160 km) away
Historical summary
Rebuilt in the 1920’s
cgl-uk.com 10
Historical summary1940-41
cgl-uk.com 11
Historical summary
Post-war: Industrial evolution
cgl-uk.com 12
evolution
Historical summary
1999-2004Partial demolition and remediation for industrial re-use
cgl-uk.com 13
Current Site Investigation
Additional investigation required for 2012 consented schemeGeoenvironmental - large number of remaining
The Holistic Approach
cgl-uk.com 14
Geoenvironmental - large number of remaining sources needed investigationGeotechnical – limited site wide data for detailed designCombined investigation to provide comprehensive solution
Expected Geology
Made GroundAlluvium (including Peat layers)
London Basin sequence
cgl-uk.com 15
River Gravel DepositsLambeth GroupThanet SandsChalk at depth
Current Site Investigation
31 cable percussion boreholes • 15m or 28mbgl with in-situ testing and sampling• Gas and groundwater monitoring installations (some dual)
Scope of Works
cgl-uk.com 16
• Gas and groundwater monitoring installations (some dual)
157 window sampler boreholes• Maximum depth of 5mbgl• 56 monitoring installations
30 trial pits
Minoco WharfVenesta Wharf Crescent
Wharf
cgl-uk.com 17
Current Site Investigation
Not a bad place to be…
cgl-uk.com 18
Current Site Investigation
Dye WasteFree product
Encountered Contamination
cgl-uk.com 19
Current Site Investigation
River Wall
cgl-uk.com 20
Current Site Investigation
Concrete
cgl-uk.com 21
Current Site Investigation
Testing
SPTsGeotechnical testing
cgl-uk.com 22
• PSDs / sedimentation• Atterberg Limits• Moisture Content• Quick undrained triaxials• Sulphate and pH
Contamination testing• Standard soil suites• Asbestos screen/ID• Leachate suites• Groundwater analysis
Current Site Investigation
Monitoring
Ground gas/vapourGroundwater levels
cgl-uk.com 23
Groundwater samplingTidal monitoring
The Outcomes
Geological Cross-Section
cgl-uk.com 24
The Outcomes
Perched groundwater in Made Ground Shallow groundwater in KPG
Groundwater
cgl-uk.com 25
• In continuity with the River Thames
Deep groundwater • Under sub-artesian pressure
Tidal Variation
The Outcomes
Human health assessmentGround gas assessment• Range of Characteristic Situations (1 to 5) across the site
Contamination Assessment
cgl-uk.com 26
• Range of Characteristic Situations (1 to 5) across the site but generally, CS2
Groundwater assessment• soil contaminants leachable• underlying groundwater bodies affected
DQRA
Conceptual Site Model
cgl-uk.com 27
The Outcomes
Basement excavations proposed = mitigated majority of risks from soil sources Proposed permeable reactive barriers along River
Remediation Recommendations
cgl-uk.com 28
Proposed permeable reactive barriers along River edge and northern boundaryGround gas protection measures (vent layer, membrane and vent trench)Barrier layers in gardens and communal landscaping
The Outcomes
Geotechnical Assessment
cgl-uk.com 29
Shallow foundations for lightest structuresPiled foundations in to Kempton Park Gravel and Thanet Sands
Geotechnical outcomes
cgl-uk.com 30
The Outcomes
cgl-uk.com 31
Current Situation
Construction and remediationNew River wall
cgl-uk.com 32Pump and treat Soil stabilisationBiopiles
E-Clay barrier wall
Current Situation
Construction and remediation
3.6%11%
10%
cgl-uk.com 33
16%
Thank You – Any Questions?
cgl-uk.com 34