Is the water level the high groundwater elevation? Generally with only that depth to the table the soil below your leaching area and groundwater should have been replaced with percable sand.The laws vary from state to state , so a mound system may be your only alternative solution to get as far away from the table as possible. You stated you are not far from a tidal creek, so you may be dealing with this matter longer than you would like. Any chance on city sewage?