With three more Plum Island homes destroyed and many more in danger following storms in February and March, homeowners, businesses, local and state officials, and agencies plan to spend time tomorrow to help clean up and repair the beach. Volunteers will be dispatched from 9 a.m. to noon. Those interested in participating can meet at Plum Island’s center parking lot at 8:30 a.m., or contact building inspector Sam Joslin at 978-618-4430. Several homes on Annapolis Way in Newbury have been threatened by the sea for some time, with homeowners spending their own money on a process known as beach scraping to help shore up the sands in front of their homes. Also currently underway is repair of a 1,400-foot jetty at the mouth of the Merrimack River. The jetty’s poor state of repair has been blamed by some as a contributor to Plum Island’s erosion. Homeowners and state and federal officials are trying to determine how to move forward to protect the barrier island’s homes and other property.