PROSJEKT BRYGGEN - Hordaland fylkeskommune

Appendix 1.
Pga spesielle forhold var Henning Matthiesen fra Nationalmuseet i København
forhindret fra å delta i oppsummeringsseminaret i mai 2003. Han leverte sin rapport
i mars 2004:
NATIONALMUSEET. Department of Conservation.
Composition of soil and ground water below Svensgården building IVe,
Bryggen, Bergen.
Henning Matthiesen.
Report no 12027-0001-2, March 2004.
Fra rapporten s. 16, med forfatterens tillatelse:
Conclusions and future work.
Based on the analysis of soil water from Svensgården building IVe it is
concluded that:
• Settling due to decomposition of organic matter in the analysed soil samples is
not considered a great risk under the current conditions, as the samples from
above the water table consisted of sand with a low content of organic matter.
• There seems to bee very stagnant conditions in the deeper soil strata, as the
original salt content of the deposit hasn’t been washed out yet.
• The water sample from MB6* indicates strongly reducing conditions in the
deepest soil strata.
• It has not been possible to show quantitatively significant decomposition due
to anoxic processes such as sulphate reduction or methanogenesis.
• Overall this indicates very good preservation conditions in the deepest soil
strata.
It must be emphasised that the results in this report mainly concentrate on the
deeper soil strata, as the dipwell MB6 has its water intake below – 2,3 m asl. Further
studies at the site should also involve a more critical zone above and just beneath
the ground water table. Especially it should be checked if the more organic rich soil
layers observed by Dunlop towards the north western end of the building have a
high settling potential and if there is a risk of differential settling.
These studies may include the measurement of an oxygen profile directly in the soil
of the upper layers to check the depth distribution of oxygen, as this will allow an
estimate of how much oxygen reaches the organic rich layers. The preservation
conditions may be further investigated by placing a dipwell with water intake in the
upper soil strata.
As for dipwell MB6 it may be used as a reference point to the conditions in the
deepest soil strata at Bryggen. An automated logger for water level, temperature
and oxygen should be installed for some months in the dipwell to see if the
conditions are really stagnant (as indicated in this report) or if there are changes
over time. A logger for conductivity may also be relevant, as it may show if there is
an inflow of seawater. Analysis of pyrite in the soil samples my help verify if sulphate
reduction is really quantitatively unimportant in the deeper soil layers.
* Miljøbrønn MB6 er satt ned inne i tomten for bygning IVe. Se for øvrig kap. 06.
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