The shallow aquifer near Riviera Beach, Palm Beach County, Fla., contains a cavity-riddled zone extending north and south about 5 miles inland from the Atlantic Ocean. The zone lies at approximately 60 feet below land surface and varies from 15 to 50 feet in thickness. It is approximately 3 miles in width. Aquifer material is calcareous quartz sand-stone in the cavity zone, whereas the remainder of the consolidated aquifer material is primarily limestone. The zone is overlain by several thin clay beds which provide varying degrees of confinement. The transmissivity of the cavity-riddled zone of the aquifer in the area of investigation is approximately 11,000 square feet per day. Preliminary evaluation indicates that large volumes of water of suitable quality for public supply can be developed from the zone, except in an area adjacent to a landfill where leachate has adversely affected water quality. (USGS)