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Westergasfabriek signIt is well known that sites of former manufactured-gas plants (MGPs) tend to be heavily contaminated.

The Netherlands has 234 sites of former manufactured-gas plants (Didde, 1995; Meeussen et al., 1994). The first Dutch gas plant opened its doors in 1826 and the last one closed in 1969 (Didde, 1995). Gas plants were - of course - also built in the U.S. and other countries (Ghosh et al., 1999b). The United Kingdom at least about 3000 and possibly about 5000 MGP sites (Barclay et al., 1998).

The data below are public record and concern the Westergasfabriek site in Amsterdam - before its remediation.

They were copied by hand from the Saneringsplan Westergasfabriek (Wbb-code AD 001/00 004 - onderdeel bovenisolatie - Heidemij Advies) at the offices of Milieudienst Amsterdam (upon request to see the files and subsequent appointment) in 2001.

The data on this web page are not necessarily complete or accurate and may contain errors. SmarterScience does not accept any liability in this respect.

Note also that these data are not current; these analyses took place several years prior to remediation of the site.

Objectives of this remediation were:

  • isolation at the top;
  • isolation and control to prevent dispersal;
  • continuous monitoring;
  • restrictions for parts of site, where needed;
  • enabling creation of a park.

Geology:

  • ground level at about 1.0 m NAP and at -1.2 m NAP in Overbraker Binnenpolder;
  • from +1 to about -3: filling (sand, debris, ashes, cinders);
  • from -3 to -4.5: peat (Hollandveen - original thickness was 4.5 m);
  • from -4.5 to -5: clay (local);
  • from -5 to -12: tidal-flat sands (sandy clay layers and/or clayey sand layers):
  • from -12 to -12.3: peat (basisveen 0.1 - 0.3 m);
  • from -12.3 to -30: first aquifer (clay lenses);



Hydrology:

  • phreatic - filling - resistance 3.2 - thickness 4m - permeability (m2/d) 1.25
  • confining - peat/clay - resistance 500 - thickness 2m - permeability 0.004
  • water-bearing - sandy clay - resistance 35 - thickness 7m - permeability 0.2
  • confining - peat (basisveen) - resistance 3000 - thickness 0.3m - permeability 0.0001
  • water-bearing - sand - resistance 2.3 - thickness 30m - permeability 13.3

The site lies in the transition zone between the Haarlemmervaart (-0.4 NAP) and the polder level of the Overbraker Binnenpolder (-2.15 NAP). Most phreatic groundwater flow is horizontal and to ditches, Binnenpolder and Haarlemmervaart. Less flow to Westerpark. Hydraulic grade in north-west part is 0.006 m/m to 0.01 m/m. In other parts 0.002 m/m to 0.004 m/m.



Pollution

  • Top soil:
    50% of terrain PAHs above C-value
    85% of terrain PAHs above B-value
    cyanide, oils, heavy metals occassionally above C-value
    cyanide mainly found near former "zuiverhuis" (bog ore may have been stored and regenerated there)
    reason for Cu, As, Pb in northwestern part not clear
    Pb slightly higher on the entire terrain
  • Deeper layers:
    PAHs and oils
  • phreatic water:
    very strongly contaminated with volatile aromatics and PAHs in vicinity of former gas plant
    strongly contaminated with tar and cyanide in vicinity of "zuiverhuis" and in west and northwest along railroad dike
  • tidal-sands layers:
    benzene, cyanide, PAHs, mainly in W and NW (following groundwater flow)
  • first aquifer:
    highly elevated benzene, cyanide and PAH concentrations in W




Average measured concentrations

Pollutant phreatic tidal sands soil
CNT
(µg/L and mg/kg dry material) 		147 92 220
Cu
(µg/L and mg/kg dry material) 		161 8 7
As
(µg/L and mg/kg dry material) 		17 10 5
PAHs
(µg/L and mg/kg dry material) 		234 211 36
Pb
(µg/L and mg/kg dry material) 		252 182 5




Highest concentrations measured

Pollutant phreatic tidal sands first aquifer soil
cyanide
(µg/L and mg/kg dry material) 		0 - 1.5
4000 (T) 		less than 1.5
780 (T) 		1300  
Cu
(µg/L and mg/kg dry material) 		860 28    
As
(µg/L and mg/kg dry material) 		120 36    
PAHs
(µg/L and mg/kg dry material) 		1400 2300   460
Pb
(µg/L and mg/kg dry material) 		3000 870   89

The analyses - and presumably also sampling - were carried out by OMEGAM, possibly in accordance with its "Analysevoorschriften OMEGAM, version 98.1". In those guidelines, total cyanide is defined as "The cyanide released in strongly acidic medium from a lye extraction of the soil, in combination with UV radiation at a wavelength of greater than or equal to 290 nm, including the free cyanide already present in the lye extraction."

The guidelines mention the methods NEN 6655 and EPA 335.3 with regard to the determination of free and total cyanide. It sounds like OMEGAM used to apply the EPA 335.3 protocol and at some point started using the NEN 6655 method (not necessarily during the analyses that yielded the above data).

According to OMEGAM, the EPA 335.3 method measures more of the iron-complexed cyanide in the determination of free cyanide and 100% thiocyanates in the determination of total cyanide, compared with a maximum of 10% of iron-complexed cyanide and 0% thiocyanates with the NEN 6655 method. See also article on the environmental chemistry of cyanide (pdf).

The cyanide concentrations (4,000 mg kg-1 at most) appear to be fairly normal for MGP sites. Barclay et al. (1998) reported a typical cyanide concentration range at MGP sites of 1 to 1,000 mg kg-1 soil and added that the cyanide concentration at an MGP site can be as high as 8,000 mg kg-1. The article lists concentrations as high as 50,000 mg kg-1 for certain sites in the State of New York.

blue bricks on site Westergasfabriek in Amsterdam
- © E. Webbe, BK Ingenieurs -
Cyanide compounds precipitated in these bricks causes the blue color. This does not mean that blue bricks always contain cyanide! Photograph taken on site of Westergasfabriek in Amsterdam.



Phase 1 of the cleanup of the Westergasfabriek was completed in 2003. The cleanup lasted much longer than originally envisaged (much more extensive) and cost considerably more. Monitoring will continue.

The cleanup approach for Dutch former gas plant sites varies by site.

  • In the province of Zeeland, 800 truckloads of soil were removed from the Oranjebolwerk site. 10,000 m3 of soil were cleaned by extraction. 15,000 m3 were cleaned thermally (Pelgrim, 2000).
  • Another former gas plant site is the Griftpark in Utrecht. The pollution in the Griftpark was discovered in the late 1970s. Removal of the contaminated soil was considered too costly. Instead, the pollution was isolated by an impermeable clay layer, a concrete wall of about 50 meters deep and 1235 meters long, and topped by a 1.5-meter-thick cap of gravel, a lining, sand and top soil (Marlet, 1999).
  • At Hoogeveen, the authorities removed some 500 truckloads of soil. In addition, 187 kg naphthalene, 382 kg cyanide and 97 kg aromatics were removed from over 2,000,000 m3 of groundwater (Provincie Drenthe, 1997).

An interesting diferent approach was taken in Denmark at one of its MGPs sites. Dr. Stefan Trapp at the Technical University of Denmark has just completed (December 2004) a project that investigated phytoremediation - by, for instance, willows - as a means to remove cyanide contamination.


sanering terrein Westergasfabriek in Amsterdam sanering terrein Westergasfabriek in Amsterdam sanering terrein Westergasfabriek in Amsterdam sanering terrein Westergasfabriek in Amsterdam
- © A. Souren, SmarterScience formerly Armadillo Research Services -
The above four pictures were taken in the fall of 2000, during a visit to the site, when remediation had already started.

See also these literature references and this article about the environmental chemistry of cyanide (pdf).





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September 5, 2008