Northwest Arkansas (NWA MS4s)

Stormwater Pollution Prevention, Grading, and Erosion Control Best Management Practices Manual (NWA 2016 Stormwater BMP Manual)

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Open source PDF ↗Official agency page ↗

Fields not found in document: document_metadata.last_revised_date, design_criteria.required_hydrologic_hydraulic_software

Other manuals in Arkansas: City of Fayetteville, City of North Little Rock

Document Metadata

Jurisdiction level

Other

“serve as a common guidance document for the design and implementation of control measures for construction site runoff control and post-construction runoff controls”
Executive Summary

State

Arkansas

“Stormwater discharges from construction sites must not cause or contribute to violations of Arkansas’s surface water quality standards”
Introduction

Version / edition

Revised December 2016 / NWA 2016

“Revised December 2016 ... NWA 2016 Stormwater BMP Manual”
Title Page

Adoption / effective date

2016-12

“Revised December 2016”
Title Page

Last revised date

Not found in document

No evidence cited

Relationship to state manual

independent

“ADEQ expects that the selection and implementation of appropriate BMPs outlined in this or equivalent manuals will result in compliance with water quality standards”
Introduction

Design Criteria

Design storm return periods (years)

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

“The terrace should have enough capacity to handle the peak runoff expected from a 2-year, 24-hour design storm without overtopping.”
BMP 261: Gradient Terrace

Water quality volume method

No explicit post-construction Water Quality Volume (WQv) formula. Construction sediment traps sized by settling-velocity surface area: SA = FS(Q2/VS) with FS=2 and VS=0.00096 fps for 0.02 mm medium silt (SA ≈ 2080 sf per cfs of 2-year developed peak inflow; use 10-year peak when higher protection is warranted). Chemical treatment storage recommended at 1.5× the runoff volume of the 10-year, 24-hour storm. Retention/detention ponds sized to the host municipality’s design storm (or infiltration capacity in karst). LID Appendix B addresses rain gardens, bioretention, infiltration, and green rooftops qualitatively without a regional WQv equation.

“SA = FS(Q2/VS) where Q2 = Design inflow based on the peak discharge from the developed 2-year runoff event ... VS = 0.00096 fps ... SA = 2 x Q2/0.00096 or 2080 square feet per cfs of inflow.”
BMP 401: Sediment Trap

Peak flow calculation method(s)

Rational Method, Hydrologic analysis (developed 2-year, 10-year, and 100-year peak discharges), Pre-developed condition runoff methods for allowable discharge rates

“If no hydrologic analysis is required, the Rational Method may be used.”
BMP 401: Sediment Trap

Hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Preserving Natural Vegetation / Buffer Zones, Wetland Preservation, Creation, and Re-creation, Floodway and Floodplain Controls, Dust Prevention and Control, Material Delivery, Storage, and Containment, Concrete Waste Management / Washouts, Saw-Cutting and Surfacing Pollution Prevention, Gross Solids and Solid Waste / Sanitary Service, Stabilized Construction Exit / Rumble Strips and Wheel Wash, Temporary and Permanent Seeding / Mulching / Sodding / Top-soiling, Nets and Blankets / PAM for Soil Erosion Protection, Surface Roughening / Gradient Terrace, Interceptor Dike and Swale / Grass-Lined and Reinforced Channels, Vegetated Strip / Diversionary Ditch / Pipe-Slope and Subsurface Drains, Level Spreader / Wattles / Check Dams / Brush Barrier / Gravel Filter Berm, Storm Drain Inlet Protection / Outlet Protection / Energy Dissipaters, Secondary Embedded Reinforced Perimeter Sediment Barrier, Sediment Trap / Temporary Sediment Pond, Retention / Detention Pond, De-watering / Turbidity Removal / Chemical Treatments / Filtration, Low-Impact Development – Rain Gardens / Bioretention / Grassed Swales, Low-Impact Development – Infiltration / Sand Filtration, Low-Impact Development – Green Rooftop / Impervious Area Reduction, Low-Impact Development – Cisterns and Rain Barrels / Undisturbed Water Body Buffer

“Chapter 1: Prevention BMPs ... Chapter 2: Access and Source Control BMPs ... Chapter 3: Conveyance BMPs ... Chapter 4: Treatment BMPs ... Appendix B: Low Impact Development”
Table of Contents