There are over 95,000 onsite sewage disposal systems (OSDS) (i.e., cesspools and septic tanks) used in Hawaiʻi, many close to coastlines and streams. These systems have varying levels of treatment capacity for nutrients, bacteria, and other pollutants found in wastewater and may leech into groundwater that flows to the ocean. Excess nutrients can promote rapid algal growth, outcompeting corals and disrupting the natural balance of the ecosystem.
Using findings from the Hawaiʻi Department of Health, this data consisted of estimated nitrogen flux and phosphorous flux from points representing Tax Map Key (TMK) parcels with OSDS in units of kg/day and effluent in gal/day (Whittier and El-Kadi 2009; 2014). We converted the points to raster by summing nutrient flux values within 100-m pixels and then calculated the total flux within a 1.5-km radius of each cell.