Work began last week on installation of artificial turf at Piper Field, the football stadium at Marblehead High School. The total cost will be $875,000. The field is expected to be ready for use in August, and will be open year-round and used by youth sports teams along with adult leagues. Money for the project was privately raised by the nonprofit Marblehead All-Sports Foundation. Fund-raising began last June. The project will be overseen by the town, the Andover-based athletic field design company Huntress Associates, and the foundation. The contractor is Green Acres Landscape & Construction Co. of Lakeville. The original grass field, built more than a decade ago on ledge and rock, had poor drainage, leaving pools of water on its turf and sidelines after rains.