From the event website:

What is the Big Event?

The Grand Prairie Big Event will be March 24, 2018, from 8 a.m. – 1 p.m. Patterned after similar events on university campuses, the Big Event is one day for city-wide volunteerism. Celebrating unity in the community, we will pair volunteers who want to help, with residents who have qualifying service projects. As the planning committee works out the details of the day, details will be added here.