Dallas / North Central Texas (iSWM)

iSWM Criteria Manual for Site Development and Construction

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NCTCOG iSWM Criteria Manual is regional guidance adopted/customized by many North Texas cities including Dallas. Local Provision boxes may alter criteria city-by-city; verify City of Dallas local provisions. Detailed hydrologic software requirements live in companion Technical Manuals, not mandated by name in this Criteria Manual.

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software

Other manuals in Texas: City of Amarillo, City of Arlington, City of Austin, City of Beaumont / Jefferson County Drainage District No. 6, City of Brownsville, City of College Station, City of Corpus Christi, City of Denton, City of El Paso, City of Fort Worth, City of Frisco, City of Garland, City of Grand Prairie, City of Houston, City of Killeen, City of Laredo, City of Lubbock, City of McAllen, City of McKinney, City of Mesquite, City of Pasadena, City of Pearland, City of Plano, City of Round Rock, City of San Antonio, City of Waco, Harris County, Tarrant County, Texas, Texas Commission on Environmental Quality

Document Metadata

Jurisdiction level

City

“criteria that cities and counties may use as a component of their stormwater management related development regulations”
Criteria Manual overview

State

Texas

“TPDES Stormwater permit”
Table 1.3 Water Quality Option 3

Version / edition

Revised January 2015 (December 2009 base)

“December 2009 / Revised 1/2015”
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Adoption / effective date

2015-01

“Revised 1/2015”
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Last revised date

2015-01

“Revised 1/2015”
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Relationship to state manual

independent

“The criteria may be customized by local governments to meet specific local needs”
Criteria Manual introduction

Design Criteria

Design storm return periods (years)

1-year, 25-year, 100-year

“"Streambank Protection" 1-year, 24-hour storm event; "Conveyance" 25-year, 24-hour storm event; "Flood Mitigation" 100-year, 24-hour storm event”
Table 1.2 Storm Events

Water quality volume method

Water Quality Protection Volume (WQv) based on 1.5 inches of rainfall (85th percentile storm), not a return-period storm. Option 2: treat WQv by reducing TSS from the development site for runoff from rainfalls up to 1.5 inches. Primary structural controls sized for WQv are expected to remove about 70–80% of annual average TSS load when designed per specifications. Methods to compute WQv referenced to Water Quality Technical Manual Section 1.2.

“"Water Quality" Criteria based on a volume of 1.5 inches of rainfall, not a storm frequency”
Table 1.2 Storm Events

Peak flow calculation method(s)

Rational Method, SCS Unit Hydrograph Method, Streambank Protection: control 1-year, 24-hour storm (Streambank Protection Volume / SPV), including 24-hour extended detention option, Conveyance: 25-year, 24-hour storm, Flood Mitigation: 100-year, 24-hour storm, Downstream assessment required for streambank protection, conveyance, and flood mitigation

“Rational Method / SCS Unit Hydrograph Method”
Technical methods list

Hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Bioretention, Enhanced swales (dry, wet, wetland), Detention, Filter strips, Sand filters / filter boxes, Infiltration wells and trenches, Ponds, Porous surfaces, Green roofs, Rainwater harvesting, Wetlands, Submerged gravel wetlands, Alum treatment, Proprietary systems

“secondary controls. • Bioretention • Enhanced swales (dry, wet, wetland) • Alum treatment • Detention • Filter strips • Sand filters, filter boxes, etc • Infiltration wells and trenches • Ponds • Porous surfaces • Proprietary systems • Green roofs • Rainwater harvesting • Wetl”
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