Stormwater Management for Highway Projects
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Stormwater Management for Highway Projects Regulatory Environment And Tools. Overview of Water Quality Issues. Regulation of stormwater is a national issue Runoff from impervious surfaces recognized as a major contributor to degradation of stream quality

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Stormwater Management for Highway Projects Regulatory Environment And Tools

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Stormwater Management for Highway Projects

Regulatory Environment



Overview of Water Quality Issues

  • Regulation of stormwater is a national issue

  • Runoff from impervious surfaces recognized as a major contributor to degradation of stream quality

  • Copper has been shown to harm salmonids at very low concentrations

ESA Issues

Stormwater has become a major impediment to efficient ESA consultation process due to:

  • Changing criteria for effect determinations in ESA Section 7 consultations

  • Potential extension of the “action area” from the point of discharge to the sea

Effect determinations

  • NMFS is basing Effect Determinations on the quality of the stormwater at the point of discharge

Effect determinations

NMFS has provided written guidance for effect determinations


  • New “pollutant generating impervious surface” that discharges to surface waters:

    • Travel lanes

    • Shoulder widening

    • Turn lanes

Effect determinations


  • All stormwater from the Water Quality Design Storm is infiltrated

    No Effect

  • Non-Pollutant generating surfaces

    • Sidewalks

    • Guardrail flares

    • Separated bike paths

Action Area

Most Recent NMFS Definition (or lack thereof)

  • Potentially from point of discharge to the ocean or major confluence (default)

  • Determined on a project-by-project basis

    Just because there are no listed fish in the immediate project area does not mean that a BA is not needed

Action Area

ODOT has proposed determining the Action Area based on a “defining concentration” resulting from dilution of the highway runoff

FHWA is reviewing the proposal

DEQ 401 Certification

  • Heightened scrutiny of projects for 401 certification

  • Increased attention to the protection of “Beneficial Uses”

DEQ 401 Certification

“Beneficial Uses” is interpreted to give DEQ the responsibility to evaluate a projects impacts to more than simple water quality:

  • Riparian impacts

  • Channel modification

  • In-water work windows

  • Wetland impacts

  • Hydrologic impacts

DEQ 401 Certification

Focus on providing stormwater treatment

“To the Maximum Extent Practicable”

No real definition available: DEQ is being sued over its interpretation

ODOT/DEQ Streamlining Performance Standard: Goals

  • Meet State WQ Standards

  • Don’t increase the pollutant load when practicable

  • Decrease the pollutant load when feasible

  • Manage the hydrology to prevent harm to the receiving water and its channel

ODOT/DEQ Streamlining Performance Standard: Objectives

  • Infiltrate project stormwater

  • Treat at a minimum 140% of the new impervious surface area

  • Treat the WQ design storm

  • Don’t put treatment into sensitive resource areas

  • Prevent erosion by stormwater

  • Maintain pre-project hydrology

  • Provide for adequate maintenance of facilities

ODOT and the Resource and Regulatory agencies have collaboratively developed a pragmatic approach to improve stormwater management and facilitate permitting:

Focus on effective treatment, not numerical standards

Water Quality Design Storm

Water Quality Design Storm

Flow Control Design Storms

  • These are the smallest and largest storms that are subject to hydrologic modification

  • Hydrologic modification has two goals:

    • Protection and maintenance of channel processes

    • Flood control

Flow Control Design Storm

Lower Discharge Endpoint

  • Western OR - 42 percent of the 2-year, 24 hour event

  • Southeast, Northeast, North Central Regions: 48 percent of the 2-year, 24 hour event

  • Eastern Cascades Region: 56 percent of the 2-year, 24 hour event

    Upper Discharge Endpoint

  • Minimally incised streams -Channel bank overtopping event

  • Incised Streams -10-year/24-hour storm event

Flow Control Design Storm

Proposed threshold of concern :

  • Flow control does not need to be addressed if the project increases the 10 year 24 hour storm discharge by less than 0.5 cfs

BMP Selection Tool

  • The selection of treatment techniques and strategies is supported by the BMP Selection Tool

  • The Selection Tool is to help designers find the most effective treatment that is suitable for an individual project

BMP Selection

  • Key selection criteria (metrics)

    • Treatment capability

    • Physical site suitability

    • Maintenance

    • Resources, risk and public perception

    • Cost

BMP Selection

BMPs by Preference

  • Infiltration

  • Media filtration (ecology embankement, compost filter etc)

  • Standard sedimentation BMPs with amended soil


  • Infiltration ranks on the top because it reduces both the volume of runoff and the pollutant load delivered to the receiving waters.

Infiltration and UICs

DEQ now considers UICs to be an important tool in the stormwater management arsenal.


UICs must still be registered and permitted, but DEQ is encouraging system wide permits.

Stormwater must meet Drinking Water Standards before discharge from a UIC

Low Impact Development

  • Anything that can be done to reduce the volume of stormwater and pollutant load in stormwater

  • Minimization of impervious surface area and direct discharge of stormwater to surface waters

  • Water quality features in the linear right- of-way that emphasis infiltration and filtration through vegetation

Regulatory Tools: ESA

  • Programmatic Permits: SLOPES IV

    • Treat the Water Quality Design Storm from all the project impervious surface using “highly effective” BMPs

    • Maintain pre-project flow and duration for events in the range of the Flow Control Design Storms

Regulatory Tools: ESA

For individual consultations under the ESA:

  • Use BMP Selection Tool to identify the best and most appropriate treatment technique(s) for the project

Regulatory Tools: DEQ

  • ODOT has a Streamlining Agreement for Stormwater Management Plan approvals

    • Communication Plan

    • Performance Standards

    • SWMP Checklist

    • Training of ODOT staff

Regulatory Tools: DEQ

Stormwater Management Plan Checklist

Developed for ODOT projects to assist designers and permit specialists to develop and review Stormwater Management Plans for Section 401 Clean Water Certification.

Regulatory Tools: DEQ


  • Focused on the development and review of SWMPs

  • Is being offered to ODOT staff over the next several months

  • Anticipate opening up the training to Consultants and Local Agencies


  • Regulatory scrutiny of stormwater management and treatment has tightened up considerably

  • Use of “Highly Effective” BMPs will ease ESA and DEQ permitting

  • So far we have avoided numerical standards

  • Guidance on BMPs is available, and the Selection Tool is in development

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