| #D001 | | I/I | infiltration and inflow | high |
| #D002 | | SSOs | sanitary sewer overflows | high |
| #D003 | | CSOs | Combined Sewer Overflows | high |
| #D004 | | NPDES | National Pollutant Discharge Elimination System | high |
| #D005 | | Combined sewers | designed to collect both sanitary sewage and stormwater runoff in a single-pipe system | high |
| #D006 | | Sanitary sewers | installed to collect wastewater only and do not provide widespread drainage for the large amounts of runoff from precipitation events | high |
| #D007 | | Secondary Treatment Standards | Minimum, technology-based standards for discharges from municipal wastewater treatment facilities. | high |
| #D008 | | Integrated Planning | offers a voluntary opportunity for a municipality to propose to meet multiple CWA requirements by identifying efficiencies from separate wastewater and stormwater programs and sequencing investments. | high |
| #D009 | | National Pretreatment Program | identifies specific discharge standards and requirements that apply to sources of nondomestic wastewater discharged to a POTW. | high |
| #D010 | | Biosolids | nutrient-rich organic materials produced by wastewater treatment facilities. | high |