Summary and conclusions

Opdatering af JAGG - projektkatalog

In the beginning of 2006 the Danish EPA (DEPA) started a project to revise the procedure for risk assessment related to soil and groundwater contamination. The model (named JAGG) used was originally worked out in connection with the publication in 1998 of the guidelines 6 & 7 from DEPA, named “Guideline for remediation of contaminated soil”. The basis of the model is therefore more than 10 years old. In this period developments of knowledge within the area of interest have been vast. DEPA together with end-users and other partners wanted the gained experiences within the timeframe to be incorporated in a new version of JAGG.

On this background DEPA wrote a letter to partners within education, local authorities, and consultants etc. to collect proposals for a revision of the model. An overview of the proposals is given in annex 1. The subjects that turned out to be the most common were:

The soil vapour intrusion model.
Processes during vertical transport in the unsaturated zone.
Fugacity, including handling of mixed products free phase (gasoline, gas oil etc.).
Expansion of the model to handle fluxes and mass balances and not only concentrations.
A general enhancement of the layout and user friendliness of the model.

Apart from the abovementioned subjects proposals to change other part of the model were received in lesser numbers.

Based on the incoming subjects a workshop was held with app. 30 participants. List of participants are in annex 2. On the workshop each of the abovementioned topics were presented through a platform presentation. The participants where divided into 4 groups beforehand, representing the first 4 topics. The groups discussed their own topic on basis of the incoming proposals and their own experiences on the topic. A prioritized list was produced on each topic listing different subsets that needed to be investigated in order to make a better model. The most important sub topics are listed in this report.

As a part of the process the most important foreign models were compared to JAGG evaluating the best way for the upgrade. Based on publicized studies the calculations carried out in JAGG are comparable with most of the models used within EU and USA. This author evaluate that uncertainty on the data entering the models and the general conceptual error most times exceeds the differences in the results that originates from using different model codes. Cons and pros were observed within all model codes evaluated.

Despite the above a special consideration should be given to the model complex RISC4 before developing a special Danish model. RISC4 is a commercial risk assessment product based on peer-reviewed data and methods. It has been out for several years and is continuously developed. The advantage of using such a product is that further development and service is provided by an independent commercial partner, and that many of the new methods asked for already are present in for instance RISC4. The drawback is that the model is commercial, meaning all users have to pay a fee, and that the way the model engine work is proprietary giving lesser insight and a possibility for potential errors. Apart from this there also is an administrative aspect due to the fact that JAGG and the existing “Guideline to remediation of contaminated soil” are closely related.

If DEPA choose to go on with a further development of JAGG as a spreadsheet based model developed in house this author suggest a prioritized effort to:

1. Expand the existing vertical transport module, potentially also handling dual porosity phenomena’s. Microbial degradation should be incorporated in the calculations. Rate constants should be based on literature values, using statistical based values if existing.

2. Add modules to be able to evaluate soil vapour intrusion through a variety of basement and floor types.

3. Update the existing database of physical/chemical data.

4. Develop methods for calculating soil gas and water concentrations when free phase of mixed products are present

5. Make a general revision of the lay-out of the existing JAGG model interface

The first 2 topics demand a conceptual as well as a mathematical description, whereas topic 3 and 4 is a more straightforward data handling exercise. Topic 5 is merely related to EXCEL programming and only to a lesser extent technical skills within soil contamination.