On a biennial basis MWRD conducts a Cost of Service Study (COSS). The purpose of this study it to segregate utility costs between water and wastewater. Necessary rates are then determined to cover appropriate costs. This ensures that water and wastewater fees and charges are adequate to cover their respective costs. MWRD’s first COSS was completed in 2004, and has been updated in 2007, 2011, 2013 and 2015.