SAUGUS – Blasting at a Main Street construction site will be changed for safety after a loose boulder almost demolished part of the Grace Ministries North Shore church building.Fire Chief Donald McQuaid reported that during blasting at a planned Pioneer Charter School of Science around noon on Friday, a boulder came loose and rolled to the church property, narrowly avoiding a wall of the church.After receiving several calls of concern about the boulder, McQuaid said he met on Monday morning with the blasting contractor, Maine Drilling and Blasting, to set new guidelines using smaller but more frequent explosions. The blasting is expected to resume Wednesday.McQuaid said no one was hurt during the noontime incident, since the planned blasting ensured Main Street traffic was stopped and no one was inside the church. He said the boulder was removed immediately after.No one from Grace Ministries could be reached for comment.