Georgia DOT’s Revised

Stormwater Manual

Georgia Association of Floodplain ManagementAnnual Technical Conference

March 2014

Presentation Topics

• Purpose of the Manual Update• Research Conducted• What’s New

– Policies– Stormwater Planning– Post-Construction Best

Management Practices (BMPs)– Infeasibility

• Status

Source: WSDOT

• New NPDES Construction General Permit– Issued September 24, 2013

• New NPDES Municipal Separate Storm Sewer (MS4) Permit– Issued January 3, 2012

• New GDOT Stormwater Policy• Revised Manual for Erosion and

Sediment Control– Issued January 1, 2014

• Manual Modernization

Purpose of the Manual Update

Purpose of the Manual Update

New GDOT MS4 Permit requirements:• Address post-construction stormwater runoff• Implement checklists

– Post-construction BMPs– Low Impact Development (LID)/Green

Infrastructure (GI) practices• Incorporate standard six minimum control

measures

Purpose of the Manual Update

Key Policy Updates Include:• Design of Post-Construction BMPs• MS4 Permit

Afforded GDOT the option of adopting the GSWMM or developing their own manual.

• LID/GI Requirements• US Army Corps of Engineers

– Fish Passage– 404 Nationwide Permit Regional Conditions

Proposed Scope of the Manual

Policy BasedIncorporate New MS4

Permit Requirements

Georgia Specific

Linear (Highway) Focused

Research Conducted

GDOT document review:• MS4 Permit • Current Drainage Manual• Policies• Standards, Details, and SpecificationsGeorgia document review:• Georgia Stormwater Management Manual • Coastal Stormwater Supplement • Georgia Erosion Control Manual

Research Conducted

State of the Practice/Literature Review:• National Sources (FHWA, AASHTO, EPA, etc.)• State policies, practices, and BMPs

– North Carolina– Tennessee– South Carolina– Washington– Maryland– Pennsylvania Source: FHWA

Revised Table of Contents

• Ch. 1 - Introduction• Ch. 2 - Agency Coordination and Regulations• Ch. 3 - Stormwater Planning• Ch. 4 - Hydrology & Hydraulics• Ch. 5 - Channels• Ch. 6 - Pavement Drainage• Ch. 7 - Storm Drain Design• Ch. 8 - Culverts• Ch. 9 - Erosion and Sediment Control Guidelines• Ch. 10 - Post-Construction Stormwater Design Guidelines• Ch. 11 - Stream & Wetland Restoration Concepts• Ch. 12 - Bridge Hydraulic Design Criteria• Ch. 13 - Bridge Deck Drainage Systems

Permitting Agencies &

Coordination

Hydrology &

Hydraulics

Construction Stormwater

Requirements

Stormwater Planning

Post-Construction Stormwater

Requirements

Stormwater Planning

Incorporate stormwater early to avoid project delays

Stormwater Planning

Public SafetyMotorists, pedestrians, maintenance personnel

Protection of GDOT facilitiesReducing erosive damage

Protection of Private Property– Flood damage– Upstream & Downstream affects

Protection of the surrounding environmentHarming receiving waters, ecosystem, or wildlife

Initial Planning Concepts

1. Avoidance: avoid disturbing environmentally sensitive areas (e.g. changing the roadway alignment to avoid these areas)

• Wetlands • Rivers• Lakes• Streams• Floodplains• Sensitive habitats

Initial Planning Concepts

2. Minimization: minimize the disturbance required for the project (both immediate and long term)

• Buried culverts or bridges • Selective clearing practices

Source: NPS

Initial Planning Concepts

3. Footprint reduction: reduce the roadway footprint by considering different alternatives

• Reduce the lane width• Reduce median width• Reduce shoulder width

Source: www.PPS.org

Other Planning Concepts

Context Sensitive Solutions • Planning involving all stakeholders • Design enhances scenic, aesthetic, historic, and

environmental resources while improving safety and other fundamental design requirements

LID/GI Practices• Strongly encouraged and are required when feasible• Must be considered during the design phase

LID and GI Practices

LID/GI Checklist• Design Considerations• Design Documentation• Inspection &

Maintenance Responsibility

Submitted with plans at milestone submittals

Submitted to EPD with MS4 annual report

Primary Planning Resources• GDOT Stormwater Manual• GDOT Policy• Georgia Stormwater Management Manual &

Coastal Supplement

Post-Construction Stormwater

1. Filter Strip2. Grass Channel3. Enhanced Swales4. Infiltration Trench5. Sand Filter6. Dry Detention Basin

7. Wet Detention Pond 8. Stormwater Wetland9. Bioslope10. Open Graded Friction

Course (OGFC)11. Bioretention

Post-Construction Stormwater

GDOT’s current list of preapproved BMPs (Structural)

Post-Construction Stormwater

Applies to new projects that are:

• Within MS4 permitted areas areas (shown on the map)

• Linear roadway projects disturbing >1 acre or site development projects adding more than 5,000 square feet of impervious area

Post-Construction Stormwater

Exclusions include:• Maintenance and safety improvements that do not

disturb > 1 acre (shoulder building, sound barrier construction, etc.)

• Non-GDOT owned or operated (maintained) roadways

Source: GDOT

Post-Construction Stormwater

Exclusions include:• Sites where runoff exits the R/W as sheet flow and

does not cause instability, erosion, or flooding.• Scenarios where individual post-construction BMPs

are deemed infeasible.

Infeasibility Criteria

BMP cost (>10%)

Schedule delay (>90 days)

T&E species impact

Community/cultural resource damage

Residence or business

displacement

State, Federal Law, or

regulation violation

Infeasibility Report (GDOT template) to include the following information:

• Reason

• Location

• Alternatives analysis

• Cost analysis

Status

Under final review by GDOT

and FHWA

MS4 Permit elements must be

reviewed and approved by EPD

Anticipated Release in the 2nd quarter of

2014

Stay Tuned…

Questions?

Source: GDOT

Brad McManus, PE – GDOT Office of Design Policy & Support bmcmanus@dot.ga.gov

Charles Crowell, PE – URScharles.crowell@urs.com

Contact Information