Monitoring ground conditions in Skien

The water and wastewater system in Skien is being renovated. NIKU is in place for archaeological investigations. Cautus Geo has established monitoring of ground conditions. It is about the preservation of cultural heritage dating back to the Viking Age.

Skien was established as a trading centre for whetstones and other commodities in the 10th century. This was revealed by excavations in the late 1970s. New archaeological investigations are now being carried out. This is part of the renovation work for the water and sewage system in the city centre.

The medieval towns and grounds are protected. Excavation work therefore triggers archaeological investigations.

- "Now we can gain new and important knowledge about Skien's oldest history," says archaeologist Kristine Ødeby Haugan. She is NIKU's project manager in Skien.

Archaeology in a construction trench

The NIKU surveys take place in the construction trenches for the renovation work.

- We do not dig extra deep for our surveys. We are mapping where we are digging. In addition, we are keen to secure the cultural layers that lie close to and deeper than where we are currently digging. That's where Cautus Geo comes in. They have instrumented the ground to provide real-time data that shows what is happening underground. Without oxygen, cultural artefacts can lie untouched for thousands of years without being destroyed," says Haugan.

Cautus Geo has previously instrumented continuous and automatic environmental monitoring in medieval cities such as Bergen, Stavanger, Tønsberg and Oslo.

- In Skien, we will have two environmental monitoring profiles. One towards the harbour and one further up in the city. This will enable us to monitor the preservation conditions in the cultural layers with time series of five years. This will provide important knowledge about what's happening underground and how the preservation conditions in Skien are developing. We haven't had instrumental monitoring there before," says Haugan.

Unspoilt cultural heritage sites

Archaeological investigations in the construction trenches do not reveal the whole story. Cultural artefacts will lie deeper in the ground. The aim is to leave them untouched and preserve them where they are. In technical terms, this is called «in situ» preservation. The idea is that they can be investigated in the future.

- So we need to know that they will be preserved in good condition for years to come. That they are safe where they are. So we need to know how preservation conditions are and how they are developing," says Haugan.

NIKU is an international leader in the use of technology for «in situ» conservation of cultural heritage.

- "Instrumented monitoring provides exciting insights into the use of technology for preservation," says Haugan, who has previously led extensive excavations in cities and churches in Oslo and at Avaldsnes on Karmøy.

Found brewery foundations

The investigations in Skien have several objectives, including mapping the shoreline as it was in the Middle Ages and whether there are any preserved harbour structures.

- We have found brewery foundations. These will be dated and analysed further. We have also found whetstone blanks, pottery, small coins and bone fragments. Everything will be dated and analysed further. We will also continue with archaeological monitoring in Skien during the next phase of the renovation work, which will start before the summer," says Haugan.

Instrumentation

• Campbell data logger (collects and transmits data)
• 3 sensors measure pH
• 2 sensors measure oxygen
• 4 sensors measure redox conditions
• 3 sensors measure soil moisture and conductivity
• 5 temperature sensors
• Cautus Web - receives, analyses and converts data into information that can be read continuously