New Jersey Department of Environmental Protection (NJDEP)

New Jersey Stormwater Best Management Practices Manual — Chapter 5 (Quantity and Quality Standards and Computations) and Chapter 9.7 (Small-Scale Bioretention Systems)

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Multi-chapter excerpt (Ch5 July 2023 calculations/standards + Ch9.7 Jan 2026 small-scale bioretention), not the full NJ BMP Manual. WQDS (1.25 in/2-hr) and quantity storms (2-/10-/100-year current and projected) are from Ch5; GI BMP inventory is incomplete relative to the full Chapter 9 series. N.J.A.C. 7:8-5.7 requires NRCS methodology but does not mandate a specific software package (HydroCAD appears only in worked examples). TR-55 is cited as superseded by NEH Part 630.

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software, design_criteria.approved_bmp_categories (complete Chapter 9 GI catalog beyond practices named in this Ch5/9.7 excerpt)

Document Metadata

Jurisdiction level

state

“specifically required by the NJDEP Stormwater Management rules at N.J.A.C. 7:8 et seq.”
Chapter 5, Page 1

State

New Jersey

“New Jersey Stormwater Best Management Practices Manual”
Chapter 5 header

Version / edition

Chapter 5: July 2023; Chapter 9.7: January 2026

“New Jersey Stormwater Best Management Practices Manual July 2023... New Jersey Stormwater Best Management Practices Manual January 2026”
Chapter 5 header; Chapter 9.7 header

Adoption / effective date

2023-07

“New Jersey Stormwater Best Management Practices Manual July 2023”
Chapter 5 header

Last revised date

2026-01

“New Jersey Stormwater Best Management Practices Manual January 2026”
Chapter 9.7 header

Relationship to state manual

independent

“New Jersey Stormwater Best Management Practices Manual... NJDEP Stormwater Management rules at N.J.A.C. 7:8 et seq.”
Chapter 5, Page 1

Design Criteria

Design storm return periods (years)

2-year, 10-year, 100-year

“post-construction runoff hydrographs for the current and projected two-, 10- and 100-year storm events, as defined and determined pursuant to N.J.A.C. 7:8-5.7(c) and (d)”
Chapter 5, Stormwater Runoff Quantity Control Standards, Page 4

Water quality volume method

NJDEP Water Quality Design Storm (WQDS): 1.25 inches of rain falling nonuniformly over 2 hours (N.J.A.C. 7:8-5.5). NRCS methodology is used to compute WQDS runoff volume, peak rate, and hydrograph; BMPs such as small-scale bioretention must store/treat the entire WQDS volume.

“For stormwater runoff quality control, N.J.A.C. 7:8-5.5 requires using 1.25 inches of rain falling nonuniformly in a 2-hour storm event, which is also known as the Water Quality Design Storm (WQDS).”
Chapter 5, Page 20–21

Peak flow calculation method(s)

USDA NRCS methodology (NRCS Runoff Equation and Dimensionless Unit Hydrograph; NEH Part 630 Hydrology Chapters 7, 9, 10, 15, and 16), NRCS Curve Number (CN) method

“the Stormwater Management rules at N.J.A.C. 7:8-5.7 allow only the methodology listed below... The USDA Natural Resources Conservation Service (NRCS) methodology, including the NRCS Runoff Equation and Dimensionless Unit Hydrograph as described in Chapters 7, 9, 10, 15 and 16, Part 630 Hydrology, National Engineering Handbook (NEH)”
Chapter 5, Pages 2–3

Required hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Small-scale green infrastructure BMPs (N.J.A.C. 7:8-5.2 Table 5-1 / 5-2), Small-scale bioretention systems (rain gardens, stormwater planters, bioswales, tree pits), Small-scale infiltration basins, Green roofs, Pervious paving systems, Grass swales, Cisterns, Green Infrastructure Manufactured Treatment Devices (Chapter 9.5), Manufactured Treatment Devices (non-GI; Chapter 11.3)

“green infrastructure BMPs listed in Table 5-1 or 5-2, as required by N.J.A.C.”
Chapter 5 example, ~Page 47 reference