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Stormwater in the FAHP. Stormwater Management Goals Treat the runoff generated from the Contributing Impervious Area by the Water Quality Design Storm.

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Presentation on theme: "Stormwater in the FAHP. Stormwater Management Goals Treat the runoff generated from the Contributing Impervious Area by the Water Quality Design Storm."— Presentation transcript:

1 Stormwater in the FAHP

2 Stormwater Management Goals Treat the runoff generated from the Contributing Impervious Area by the Water Quality Design Storm using “Preferred” BMPs Treat the runoff generated from the Contributing Impervious Area by the Water Quality Design Storm using “Preferred” BMPs Maintain the frequency and duration of the most important channel forming flows Maintain the frequency and duration of the most important channel forming flows

3 Triggers for Stormwater Management

4 What Triggers Stormwater Treatment Construct new pavement that increases capacity or widens the road prism: Add a lane, a turn refuge, a wider paved shoulder Add a lane, a turn refuge, a wider paved shoulder Build a new alignment Build a new alignment

5 What Triggers Stormwater Treatment Increase the CIA Adding new pavement, or Change the drainage to capture stormwater from outside the pre-project CIS

6 What Triggers Stormwater Treatment Change the Stormwater Conveyance: Relocate the drainage system Relocate the drainage system Change the type of conveyance: Change the type of conveyance: Replace a ditch with a pipeReplace a ditch with a pipe Add curbing, etc.Add curbing, etc. Enlarge the capacity of the conveyance Enlarge the capacity of the conveyance

7 What Triggers Stormwater Treatment Reconstruct pavement down to subgrade This applies to projects rehabilitating a highway, not localized repairs.

8 What Triggers Stormwater Treatment Replace a Stream Crossing

9 What Triggers Stormwater Treatment Major Structural Repairs of Bridges This is the stuff that is not normal maintenance Exempted are Seismic Upgrades that do not affect the deck or drainage

10 What Is Not a Trigger Explicit: Minor repairs Minor repairs Repaving and resurfacing that does not go down to the subgrade Repaving and resurfacing that does not go down to the subgrade

11 What Is Not a Trigger Implicit Minor, localized increases in impervious surface, such as: Minor, localized increases in impervious surface, such as: Guardrail flaresGuardrail flares Police, bus, and mail-box pulloutsPolice, bus, and mail-box pullouts Sidewalks and separated bike/ped paths that do not include installation of curbing Sidewalks and separated bike/ped paths that do not include installation of curbing

12 The Thing About Sidewalks It’s not the sidewalk, it is the curb It’s not the sidewalk, it is the curb By putting in a curb the drainage is changed, and highway runoff that may have gotten some incidental treatment now gets none. By putting in a curb the drainage is changed, and highway runoff that may have gotten some incidental treatment now gets none.

13 Flow Control Trigger Discharge into a receiving water with an upstream drainage basin of less than 100 mi2, and increase the peak 10 year/24 hour discharge by 0.5 cfs or more*.

14 Water Quality Design Storm Water Quality Design Storm Site Specific Storm Size from ODOT Precipitation Viewer 50% 67% 75% Percentage of the 2 year 24 hour storm: Min: 0.7 inches Max: 2.5 inches

15 Contributing Impervious Area: Pavement, new and old, within the project limits, and Pavement, new and old, within the project limits, and Highway related pavement that drains into the project Highway related pavement that drains into the project

16 CIA Boundaries Project Limits

17 CIA if stormwater treatment within project limits CIA if stormwater treatment at the bottom of the hill Project Limits

18 The stormwater that gets treated comes from The stormwater that gets treated comes from The projectThe project Adjacent highway that drains onto project pavementAdjacent highway that drains onto project pavement Highway that discharges into a drainage system that is modified by the project, or is in the conveyance when it discharges into the treatment facilityHighway that discharges into a drainage system that is modified by the project, or is in the conveyance when it discharges into the treatment facility

19 Always? If the CIA outside of the project limits is very large compared to the project, coordinate and negotiate with NMFS. Early The intention of the FAHP is not to derail projects by placing onerous requirements on projects.

20 Contributing Impervious Area: FAHP explicitly limits the CIA to the highway and highway associated facilities. Run-on from adjacent properties is not part of the CIA.

21 BMPs Infiltration: Infiltration Basins UICs Filter Strips with no adjacent conveyance or receiving water Surface Treatment Bioswale Bioretention (with underdrain) Bioslope (Ecology Embankment) Filter strip Detention/Retention Pond Constructed Wetland Proprietary Filter System (on QPL)

22 BMPs Use BMPs that are highly effective at treating the broad range of highway pollutants, i.e. those that incorporate a high degree of filtration through soil or media. Use BMPs that are highly effective at treating the broad range of highway pollutants, i.e. those that incorporate a high degree of filtration through soil or media. ODOT’s Hydraulic Manual includes the BMP Selection Tool to help identify and choose the preferred BMPs ODOT’s Hydraulic Manual includes the BMP Selection Tool to help identify and choose the preferred BMPs

23 Stormwater Management Stragety 1. Unmodified roadside ROW 2. Modified (enhanced) roadside ROW 3. Small, dispersed BMPs 4. Large, consolidated BMPs 5. Do the best possible, 6. And if all else fails, Off-site mitigation

24 Off-site Mitigation: Justification Unfavorable topography Unfavorable topography Site hazards (geologic, haz-mat, safety etc.) Site hazards (geologic, haz-mat, safety etc.) Conflicting resources (Wetlands, T&E, Historic, Archeologic, Env. Justice etc.) Conflicting resources (Wetlands, T&E, Historic, Archeologic, Env. Justice etc.) Excessive cost to benefit (ROW, Maintenance/Life Cycle, Construction) Excessive cost to benefit (ROW, Maintenance/Life Cycle, Construction)

25 Off-Site Mitigation MUST coordinate with NMFS!!! Aim for a site with The same general ADT, The same general ADT, The same impervious surface area, and The same impervious surface area, and The same watershed. The same watershed.

26 Flow Control Range of Flows: Lower end Eastern Cascade = 56% of the 2-year Eastern Cascade = 56% of the 2-year SE, NE, N Central Oregon = 48% of the 2-year SE, NE, N Central Oregon = 48% of the 2-year Western Oregon: 42% of the 2 year Western Oregon: 42% of the 2 year Upper End Bank overtopping if ER is = or > 2.2 Bank overtopping if ER is = or > year 24 hr storm if ER is < year 24 hr storm if ER is < 2.2

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28 Approval of SWMPs Required for Flow Control for projects discharging to watersheds smaller than 100 mi 2, or Required for Flow Control for projects discharging to watersheds smaller than 100 mi 2, or Projects that do not meet the SW design standards on-site. Projects that do not meet the SW design standards on-site.

29 Notification

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31 Notification Impervious surface, both project and total CIA, with net change Impervious surface, both project and total CIA, with net change Acres treated on and off site, by infiltration and surface BMPs Acres treated on and off site, by infiltration and surface BMPs

32 Notification Traffic Volumes for the project area and any off-site mitigation location General Categories: Very High: >100,000 ADT Very High: >100,000 ADT High: 30, ,000 High: 30, ,000 Medium: 10,000-30,000 Medium: 10,000-30,000 Low: 2,000-10,000 Low: 2,000-10,000 Very Low: <2,000 Very Low: <2,000

33 Notification Water Quality and Flow Control Design Storm depths Water Quality and Flow Control Design Storm depths Reason for exemption from flow control (if applicable) Reason for exemption from flow control (if applicable) Stormwater Manual used for design Stormwater Manual used for design

34 Notification List of BMPs used List of BMPs used Drainage Area (AKA Sub-basin)Drainage Area (AKA Sub-basin) Treatment Method (category): on or off site, surface discharge or infiltrationTreatment Method (category): on or off site, surface discharge or infiltration BMP typeBMP type Impervious surface area treatedImpervious surface area treated Receiving WaterReceiving Water

35 Notification Site plan with CIA, sub-basins, flow path, BMP locations and receiving waters

36 Tracking/Monitoring BMPs Installed, Inspected and Maintained BMPs Installed, Inspected and Maintained Any Stormwater Recommendation or Design reports developed and stamped by an engineer Any Stormwater Recommendation or Design reports developed and stamped by an engineer O&M Manual O&M Manual

37 Tracking/Monitoring Photo of the outfalls from a project Photo of the outfalls from a project Map of the project with outfalls and receiving waters Map of the project with outfalls and receiving waters

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40 Other Stuff If the highway runoff discharges to a CSO: Documentation that the facility will accept the runoff and has adequate capacity Documentation that the facility will accept the runoff and has adequate capacity Description of how the runoff will be treated to a level comparable to the BMPs listed in the FAHP. Description of how the runoff will be treated to a level comparable to the BMPs listed in the FAHP.

41 Advance Mitigation No formal process yet. No formal process yet. NMFS does not have a mechanism outside of a BO to designate treatment at one location as mitigation for a future project, and even that is uncertain. NMFS does not have a mechanism outside of a BO to designate treatment at one location as mitigation for a future project, and even that is uncertain.

42 “Excess Treatment” No formal definition… No formal definition… Deliberately taking stormwater from outside of a project’s CIA in order to treat it in a project’s BMP Deliberately taking stormwater from outside of a project’s CIA in order to treat it in a project’s BMP Specify a project or an area that may need the off-site mitigation Specify a project or an area that may need the off-site mitigation Discuss this with NMFS in advance! Discuss this with NMFS in advance!


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