how to create project level attribute

Hi,

I am writing a plugin for Risk Management. Now, there is a need to create a project level attribute where the team can set the Risk Exposure threshold value.
And I have to create a risk temperature report based on the comparison of risk exposure of each risk WI with the project level threshold value.
So I should be able to access the project level attribute from the Jazz data repository too.

Any help is appreciated.

Thanks,
Sany