Regardless of whether any special assessments have been or may be imposed on a particular parcel of real property pursuant to this chapter, in order to implement the authority granted under RCW 85.38.180(3), a special district may fix rates and charges payable by owners or occupiers of real estate within the special district. When fixing rates and charges, the district may consider the degree to which activities on a parcel of real property, including on-site septic systems, contribute to the problems that the special district is authorized to address under RCW 85.38.180(3).