I have a question about what other cities have done for our particular mural situation...

Background: An outside nonprofit agency is proposing a large scale mural on a city-owned retaining wall that is next to a sidewalk, next to a busy road. City partners are assisting with the project to help the organization get proper approvals (it will be fully funded by organization, and then the city will own the artwork once installed). 

Legal/safety question: Our city's legal department is worried that participant waivers that are completed before working on the site would not be adequate coverage and there is the potential for a waiver of sovereign immunity should a worst case scenario present itself. 

The organization would also provided general liability insurance for the duration of project. However, outside volunteers and members of the public may join the organization to assist in completing the mural. 

Question for group: Has your city had a similar project situation? And what steps were taken to make sure the participants were adequately covered for liability purposes?

All best,