City of Lancaster

City of Lancaster Green Infrastructure Design Manual

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Extracted from City of Lancaster GI Design Manual Final June 2024 PDF. Companion fee/credit policy: lancaster-pa-swmf (SWMF Policies and Procedures Manual, amended Feb 2023).

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software

Other manuals in Pennsylvania: City of Allentown, City of Erie, City of Harrisburg, City of Lancaster, City of Pittsburgh, City of Reading, City of Scranton, Pennsylvania, Pennsylvania, Pennsylvania Department of Transportation (PennDOT), Philadelphia

Document Metadata

Jurisdiction level

City

No evidence cited

State

Pennsylvania

No evidence cited

Version / edition

Final June 2024 (Revision 2.0)

“Revisions to support adoption of the City's updated 2022 Stormwater Management Ordinance — October 2023 (draft) June 2024 (final)”
Revision history

Adoption / effective date

2024-06

No evidence cited

Last revised date

2024-06

No evidence cited

Relationship to state manual

independent

No evidence cited

Design Criteria

Design storm return periods (years)

2-year, 10-year, 25-year, 50-year, 100-year

“For the 2, 10, 25, 50, and 100-year storm events, the post-development peak discharge rates will follow the applicable release rate map. (SWM Ordinance §260-304.B).”
Section 2.3.2 Rate Control

Water quality volume method

At least the first 1.25 inches of runoff from new impervious surfaces shall be permanently removed (reuse, evaporation, transpiration, and infiltration). Retention volume VRT is the larger of that 1.25-inch volume or the change in runoff volume from the 2-year/24-hour storm.

“At least the first one and a quarter inch (1.25") of runoff from new impervious surfaces shall be permanently removed from the runoff flow, that is, it shall not be released into the surface Waters of the Commonwealth or Combined Sewer System. Removal options include reuse, evaporation, transpiration and infiltration.”
Section 2.3.1 Volume Control

Peak flow calculation method(s)

NRCS Curve Number Method, Rational Method, Modified Rational Method, WinTR-55 / TR-55, HEC-HMS

“The NRCS Curve Number Method is the preferred method used to estimate site stormwater runoff from a given storm. ... project sites less than 25 acres may be sized for capacity using the Rational Method.”
Chapter 4 Methodology

Hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Bioretention/Bioinfiltration, Porous Pavement, Green Roofs, Subsurface Infiltration, Cisterns, Naturalized Basins, Stormwater Wetlands

“This includes bioretention, porous pavement, green roofs, cisterns for reuse, naturalized basins and stormwater wetlands.”
Chapter 3 / Chapter 5 BMP guidance