Mercury a Part IIa investigation - ELQF€¦ · but that mercury fulminate was needed to make...
Transcript of Mercury a Part IIa investigation - ELQF€¦ · but that mercury fulminate was needed to make...
Mercury – a Part IIa
investigation
Mandy Dennis
Senior Environmental Protection Officer
An unlikely mix!
Always expect the unexpected!
Mercury (total)
found across the
site ranging from
0.7mg/kg to
390mg/kg
Plus arsenic –
naturally
occurring
1884
1952
1964
• Where did it come from?
• Anecdotal evidence of a
tannery
• Further investigation
• 15 further trial pits
• 32 soil samples
• Mercury 2.3mg/kg to
960mg/kg
• Highly leachable
• Geology – Made ground
over Northampton Sand
and Ironstone Formation
• Mercury found to depths
of 2m
Site history
• Tannery started between 1884 and
1900
• Closed in 1957
• Sold in 1965 and used as a garage
• 2000 sold for housing
Leather finishing• Tanned leather can be dry and hard
• Casein emulsion used to make leather supple and fix the
dyes
• Milk based casein has mercuric chloride added to it
• Acts as a bactericide
• Prevents the casein going off
• Usage largely finished by the 1950s
What is casein?
• Principle protein found in cows milk as a suspension of casein
micelles
• Family of phosphoproteins
• Gives milk the white colour
• Cheese is the coagulation of casein using rennet
• Used in processed food products
• Casein based glues used in woodworking and aircraft
manufacture
• Casein glue used to coat transformer board
• Leather finishing
What next – risk assessment
• Inorganic mercury
• SNIFFER assessment gave SSAC of 20mg/kg
• Installation of boreholes
• Mercury in groundwater 83ug/l in borehole and well
• Lots of discussion about compliance point
• Source removed
• Remediation surface strip
• Clay capping layer and topsoil
Digging out hotspot
Hotspot reinstated
Why Part IIa?• Missed section of land at back of site outside footprint of the
tannery had elevated levels of mercury max 50mg/kg at near
surface
• If mercury found here could it be in other adjoining properties
around the tannery/garage
11 – 116mg/kg
0.25 – 5.9mg/kg
Part IIa investigation• 12 properties investigated
• Criteria within 20 metres of site boundary
• Special site based on the presence of mercury on the Northampton
Sand and Ironstone formation
• Investigation undertaken by the Environment Agency
Museum of Leathercraft• Kelly’s Directory 1893 list a John Lee & Son trading in the
village
• In the Welland list no mention of this company on either the
1849 or 1874 lists
• In 1915 company name changed to John Lee & Son
(Grantham) Ltd
• Up to 1930s traded as furriers, hide and skin merchants
• In the late 1930s hatters was added to the list
• Possibly closed during war time
• Known for tanning rabbit hides
• Closed in 1957 possibly due to myxomatosis in rabbits
As Mad as a Hatter!
• Listed as furriers up to 1930s
• Late 1930s company listed as hatters
• Fur from small animals used to make felt for hat
making
• Suggested they specialised in treating rabbit
hides
Carroting!
• Nothing to do with the vegetable!
• Rabbit skins rinsed in a heated solution of mercuric
nitrate or brushed onto the pelt
• Pelts dried in an over or outside on racks
• Turned the rabbit skins a carrot colour
• Fur separated from the pelt put onto a cone shaped
colander and treated with hot water to consolidate
• Banned in US in 1941 not because of health risks
but that mercury fulminate was needed to make
detonators from WWII
• Suggested the site was not operational during the
war
• Banned in UK by 1941
Carroting
Carroting
Part IIa Investigation• Investigated 12 residential properties
• Criteria within 20 metres of the boundary of the tannery
• Communication strategy
• Involved all partners such as the PCT, HPA, GPs, etc
• Consultants engaged by the Environment Agency
• Sampling of gardens for all three forms of mercury
• Results ranged from 8.41mg/kg to 62.4mg/kg
• One garden reported levels of mercury up to 62.4mg/kg
(US95 32.2mg/kg)
• SSAC 11.1 – 14.2mg/kg
Further investigation
Voluntary remediation
Human health assessment criteria
inorganic mercurymg/kg
• ICRCL 1
• SNIFFER SSAC 20
• SGV 8
• SSAC 11.2 – 14.1
• SSAC without home grown produce 51
• SGV 170
• LQM/CIEH S4UL 40
• C4SL ND
THANK YOU FOR LISTENING
Mandy Dennis
Senior Environmental Protection Officer
01832 742037