Georgia DOT s Fresh Approach to Improving Water Quality on Roadway Projects. The New Drainage Manual October 10, 2014

Transcription

1 Georgia DOT s Fresh Approach to Improving Water Quality on Roadway Projects The New Drainage Manual October 10, 2014

2 Presenters Charles Crowell, PE, CPESC, CPSWQ, CFM Project Manager, URS Roger Cox, PE, CPESC, CFM Civil Engineer, URS

3 Today s Agenda Overview of GDOT s MS4 Permit The Approach: How the Manual was Revised Improving Water Quality: The Revised GDOT Drainage Manual

4 MS4 Permit Overview New NPDES MS4 Permit Issued January 3, 2012 What is GDOT s MS4 Permit? 5 year term permit (Jan 2012 Jan 2016) Each year GDOT is tasked with new permit goals and requirements for the 6 Minimum Control Measures (MCMs)

5 MS4 Permit Overview New GDOT MS4 Permit requirements: Incorporate standard six MCMs 1 - Public Education & Outreach 2 - Public Participation/Involvement 3 - Illicit Discharge Detection & Elimination 4 - Construction Site Runoff Control 5 - Post-Construction Runoff Control 6 - Pollution Prevention/Good Housekeeping Address post-construction stormwater runoff

6 MS4 Permit Overview MCM 5 Requirements Include: Adopt the Georgia Stormwater Management Manual (Blue Book) or develop a GDOT specific manual. Post-Construction BMPs Design Guidelines LID/GI Goals

7 MS4 Permit Overview Permit Uniqueness GDOT MS4 boundary is an overlay of the Phase I and Phase II communities, not the entire state.

8 MS4 Permit Overview In some situations, permit requirements may not actually apply: Project Level Exclusions Outfall Level Exclusions Infeasibility

9 MS4 Permit Overview Project Level Exclusions Entire project exempt from permit requirements 1. Non-GDOT owned facility 2. Project not in MS4 area 3. Maintenance/Safety project 4. Prior approvals 5. Small disturbances / small addition of imperviousness

10 MS4 Permit Overview Outfall Level Exclusions A specific drainage basin of a project, defined by outfall, exempt from permit requirements 1. Change in existing roadway alignment 2. Re-alignment or piping of a stream 3. Impact to a stream buffer or wetland 4. Discharges exit R/W as sheet flow 5. Flows that originate offsite 6. Reduction (or negligible increase) in impervious area

11 MS4 Permit Overview State, Federal Law, or regulation violation Infeasibility Criteria BMP cost (>10%) Schedule delay (>90 days) Infeasibility Report (GDOT template) to include the following information: Reason Residence or business displacement T&E species impact Location Alternatives analysis Community/cultural resource damage Cost analysis

12 The Approach: Revising the Manual

13 The Manual Approach Why not use the existing state stormwater manual? Emphasis on site development Does not address the DOT s linear infrastructure Linear BMPs Please!

14 The Manual Approach Policy Based Incorporate New MS4 Permit Requirements Incorporate LID/GI Elements Linear (Highway) Focused

15 The Manual Approach Conducted a state of the practice literature review: AASHTO & FHWA (NCHRP Reports, HDS, HECs) EPA (BMP Design Guide) Many other state publications

16 The Manual Approach Conducted an industry wide post-construction stormwater policy review: North Carolina South Carolina Tennessee Alabama Maryland Indiana Pennsylvania California Washington

17 The Manual Approach Benefits from being one of the last DOTs under an MS4 permit Lessons learned from others Start a methodical, cost effective program from Day 1

18 Improving Water Quality: Revising the Manual

19 Revising the Drainage Manual Rethink the traditional highway design process and incorporate stormwater planning early Things to consider: Protection of the Environment Public Safety Protection of Private Property Protection of GDOT Facilities Regulatory Compliance

20 Revising the Drainage Manual 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 Post-Construction Stormwater Design Guidelines Ch Stream & Wetland Restoration Concepts Ch Bridge Hydraulic Design Criteria Ch Bridge Deck Drainage Systems

21 Revising the Drainage Manual Combining available research, produce a state specific manual Provide designer flexibility across different regions of the state

22 Revising the Drainage Manual Treatment Methods: Vegetated conveyance Filtration Settling Infiltration

23 Revising the Drainage Manual Linear friendly (compact, more options, etc.) Lower maintenance (emphasis on pretreatment) Cost conscience

24 Revising the Drainage Manual GDOT s current list of preapproved BMPs Filter Strip Grass Channel Enhanced Swales Infiltration Trench Bioslope Sand Filter Bioretention Dry Detention Basin Wet Detention Pond Stormwater Wetland Open Graded Friction Course (OGFC)

25 Revising the Drainage Manual Water Quality Goal: 80% TSS Removal 1.2 Rain Event

26 Revising the Drainage Manual Consider TMDLs and Impaired Streams DOTs could be sources of pollutants: Sediment Oils (vehicle fluids and deposits) Roadside fertilizers Asphalt wear Trash/debris

27 Revising the Drainage Manual BMP TSS Total Phosphorus Total Nitrogen Fecal Coliform Metals Filter Strip 60 % 20 % 20 % % Grass Channel 50 % 25 % 20 % % Enhanced Dry Swale 80 % 50 % 50 % % Enhanced Wet Swale 80 % 25 % 40 % % Infiltration Trench 80 % 60 % 60 % 90 % 90 % Sand Filter 80 % 50 % 25 % 40 % 50 % Dry Detention Basin 65 % 10 % 10 % % Wet Detention Pond 80 % 50 % 30 % 70 % 50 % Stormwater Wetland Level I 80 % 40 % 30 % 70 % 50 % Stormwater Wetland Level II 85 % 75 % 55 % 85 % 60 % Bioslope 95 % 80 % 25 % 60 % 85 % OGFC 50 % Bioretention 80 % 60 % 50 % %

28 Revising the Drainage Manual Bioslopes: Filter Strip Bioslope Media Underdrain Outlet

29 Revising the Drainage Manual Open-Graded Friction Course

30 Filter Strip Bioretention Basin Vegetative Swale Infiltration Trench Porous Pavement

31 Georgia DOT s Fresh Approach to Improving Water Quality on Roadway Projects In Conclusion GDOT has a (relatively) new MS4 permit! They have a linear friendly post-construction BMP design manual GDOT meets water quality goals while providing cost effective and efficient post-construction BMPs

32 Contact Information Comments/Questions?