Normal roof to sewer
100%Fully chargeable roof area.
Use this when roof water drains to the public sewer and no reduction is documented.
BWB fee-reduction PDFGreen roof, lower reduction
50%A 50% reduction leaves 50% chargeable.
Confirm green-roof eligibility, construction details, and supporting evidence with BWB requirements.
BWB fee-reduction PDFGreen roof, standard deep substrate
40%A 60% reduction leaves 40% chargeable.
Confirm substrate depth, retention behavior, and required documentation before treating this as official.
BWB fee-reduction PDFGreen roof, high retention
20%An 80% reduction leaves 20% chargeable.
Use only when high-retention green-roof requirements and evidence are documented.
BWB fee-reduction PDFWet roof / retention roof
50%Retention features can reduce the chargeable share.
Confirm retention-roof design, discharge behavior, and accepted proof before submitting a correction.
BWB fee-reduction PDFDrains to on-site infiltration
0%No public sewer discharge is treated as not chargeable.
Confirm the roof water does not discharge to the public sewer and that BWB accepts the proof.
BWB fee-reduction PDF