I apologize for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
You could rent a sod cutter and slice it off below the surface. Another option would be to use the herbicide glyphosate (an example product is Roundup). This herbicide will kill most green things it is sprayed on and breaks down quickly in the environment. Give it a week to move in and begin to kill the grass. Then, the area can be plowed or rototilled to prepare for the garden. A week after rototilling, you can plant seeds. This product works best on actively growing weeds, not stressed or dormant ones.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
Q&A Library Searching Tips