Water Quality Basics

Water quality management requirements for transportation agencies are related to implementation of the NPDES program along with the water quality certification program under the CWA.

Currently there are three areas related to water quality that are having a significant impact on transportation practice nationwide:

  1. NPDES requirements for obtaining permits for operation and maintenance of Municipal Separate Storm Sewer Systems (MS4s).
  2. NPDES requirements for permitting Stormwater Discharges Associated with Construction Activities.
  3. NPDES requirements for compliance with effluent standards related to established Total Maximum Daily Loads or other effluent discharge standards that may be required by the state regulatory agency.

[Note: Water quality issues span a broad range of concerns that overlap into many areas of science and numerous environmental issues and concerns. This section deals only with the primary issues of stormwater quality and that impact the detailed design and construction of transportation facilities. Other water related issues, such as ground water, water supply, water and stormwater quantity, aquatic habitat, etc., are not addressed here.]

4. National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer Systems (MS4) Permitting Requirements under CWA Section 402

To achieve its objectives, CWA Section 402 considers all point source discharges into the nation’s waters unlawful, unless authorized by a permit. Thus industrial and municipal entities that discharge any type of water such as waste water or stormwater, must obtain permits from EPA or a designated state program, under the NPDES.

Stormwater runoff from transportation facilities and construction projects is considered by broad definition under the CWA to be a point source discharge and has been identified as a major source of pollutants discharged into the nation’s waters.

Therefore, as part of the implementation of the NPDES, permits are required for operation of MS4s. Under the initial implementation of the MS4 Phase I program (1990) stormwater discharge permits were required for urbanized areas with populations greater than 100,000. These are called “large and medium MS4s.” Most state transportation agencies had facilities in one or more of the regulated MS4s and were required to obtain individual permit coverage or joint coverage with the municipal jurisdiction. These permits must be renewed on a 5-year cycle. A detailed summary of the Phase I Program is available in EPA’s Overview of the Stormwater Program.

Phase II permits required stormwater quality monitoring programs for wet weather and dry weather discharges, and the development of detailed stormwater management programs (SWMPs). Stormwater management programs also were required to implement public education and outreach on stormwater impacts, public involvement/participation, illicit discharge detection and elimination, construction site stormwater runoff control, post-construction stormwater management in new development and redevelopment, pollution prevention/good housekeeping for municipal operations.

The Phase II rules include many of the State transportation agencies that were not included in the Phase I permits. Phase II includes urbanized areas with over 50,000 in population with storm sewer systems that discharge into waters of the U.S. not covered by Phase I. These are referred to as “small MS4s.” State transportation agencies will work with municipalities in small urbanized areas to obtain their permits and contribute to the development and implementation of a Stormwater Management Program (SWMP).

A SWMP must include measurable goals for each of the “minimum control measures.”

    • Public Participation/Involvement
    • Public Education and Outreach
    • Illicit Discharge Detection and Elimination
    • Construction Site Runoff Control
    • Post-Construction Runoff Control
    • Pollution Prevention/Good Housekeeping

While the SWMP must address all six of these minimum measures, two of these – post-construction runoff control and pollution prevention/good housekeeping – are having a significant impact on current and future development of highway and other transportation systems. The requirement for post-construction runoff control requires that new and redevelopment projects address stormwater runoff with permanent best management practices (BMPs) of some type. For rural corridors the vegetated roadside is generally sufficient to handle normal stormwater discharges. However, in urban areas where space is limited more reliance must be placed on active treatment systems. This is probably the next area of focus, particularly for those transportation agencies in large metropolitan areas.

The Phase II requirement for good housekeeping is also an area of impact that has been given less attention but has been a significant challenge to many transportation agencies. The areas of greatest impact are departmental equipment maintenance yards, bulk storage areas for deicing materials and aggregates, rest areas and roadside parks, and other permanent facilities operated by the transportation agency. Many of these facilities require the implementation of special controls and management measures to control stormwater runoff.

At this time all state departments of transportation are working on implementing their SWMPs to address the six minimum measures. Because there is such variety in the implementation strategy the individual states should be contacted for specific program information.

NPDES Stormwater Management for Construction Sites

The rules implementing the NPDES required that eleven categories of industrial activity obtain permits to discharge stormwater. Because stormwater discharges from construction sites are significantly different than other types of industrial stormwater, EPA opted to permit construction activities separately from other industrial activities. The rules require stormwater discharge permits for sites of one acre or greater. Some states classify sites of one to five acres as “small sites.” Sites of five acres or more are classified “large sites,” and they have different permitting requirements from state to state.

The permitting requirements for construction projects should not be confused with other management requirements of the MS4 permits. Although construction is a temporary activity, the loss of surface cover exposes the soil and will result in accelerated erosion if not properly managed. By volume, soil particles are the number one pollutant in the nation’s waters. Sediment-bearing runoff from construction sites has been identified as a source of pollutants that can result in significant damage to water quality. As runoff moves over a construction site, it mobilizes all available pollutants, which may include: soil particles which may bond with other chemicals, surface debris, soluble chemicals, pathogens, grease and oil, etc. If this runoff is allowed to reach a water body or a conveyance that is connected to a water resource it can result in significant adverse impacts.

The NPDES stormwater program recognizes that construction site runoff represents a pollution risk that is significantly different from other industrial stormwater discharges. Therefore the NPDES requires operators of constructions sites of one acre or larger (including smaller sites that are part of a larger common plan of development) to obtain authorization to discharge stormwater under a state or federal NPDES construction stormwater permit. The Construction General Permits (CGPs) issued by states and EPA require the filing of a Notice of Intent, the development of a Storm Water Pollution Prevention Plan (SWPPP) and filing a Notice of Termination once the construction site has been restabilized. The key document is the SWPPP which details how the site will be managed to prevent the pollution of adjacent waters.

EPA has delegated the construction permitting authority to most of the state resource agencies; however, EPA remains the permitting authority in a few states, territories, and on most federal and Indian lands. For construction on EPA regulated lands, construction projects must seek coverage under the EPA Construction General Permit (CGP). State construction general permits have a similar structure to EPA’s CGP, but individual states may have additional requirements that are tailored to protect the unique characteristics of their water resources.

Coverage of NPDES general permits for construction stormwater discharges is limited to five years.

Total Maximum Daily Loads (TMDLs): Establishment of State-based Water Quality Standards under Clean Water Act Section 303

Under section 303(d) of the Clean Water Act, all states must develop a list of impaired water bodies. This list is generally referred to in regulatory documents as the “303(d) list.” For all of the water bodies on the 303(d) list the rule requires that total maximum daily loads (TMDLs) be established in order to return impaired water bodies to fishable and/or swimmable condition. The TMDL places an upper limit on the amount of a particular pollutant, such as nutrients, sediments, pathogens, or other chemical pollutants, that can be discharged into a specific water body. These loads are then distributed across all permittees that discharge into that water body.

In addition to the effluent standards required by an established TMDL, many states are adding effluent standards to their general permits for stormwater discharges for construction activities. Many standards being developed are focused on protecting high quality waters and to ensure that the combined BMPs used for stormwater control on construction sites are protecting adjacent waters and determining the actual effectiveness of stormwater BMPs.

Under Section 303(d), states, territories, and authorized tribes are required to develop lists of impaired waters. These impaired waters do not meet water quality standards that states, territories, and authorized tribes have set for them, even after point sources of pollution have installed the minimum required levels of pollution control technology. The law requires that these jurisdictions establish priority rankings for waters on the lists and develop TMDLs for these waters.

A TMDL specifies the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards, and it allocates pollutant loadings among point and non-point pollutant sources. As TMDLs and WLAs are developed for the impaired waters, dischargers, including highway agencies, must implement Best Management Practices (BMPs) to reduce contributions from transportation-related land uses.

By law, EPA must approve or disapprove lists and TMDLs established by states, territories, and authorized tribes. If a state, territory, or authorized tribe submission is inadequate, EPA must establish the list or the TMDL. EPA issued regulations in 1985 and 1992 that implement CWA section 303(d). Once a TMDL is developed for a surface water body, a waste load allocation (WLA) must be developed specifying how much of a given constituent can be contributed to a particular water body by each discharge and discharger.

While TMDLs have been required by the Clean Water Act since 1972, until recently states, territories, authorized tribes, and EPA have not developed many. Several years ago citizen organizations began bringing legal actions against EPA seeking the listing of waters and development of TMDLs. According to EPA, there have been about 40 legal actions in 38 states to date. EPA is under court order or consent decrees in many states to ensure that TMDLs are established, either by the state or by EPA.

On July 21, 2003, EPA issued Guidance for 2004 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d) and 305(b) of the Clean Water Act. The guidance is intended to be used by states in developing their integrated lists of impaired waters under Section 303(d) of the act and their reports describing the quality of their waters under Section 305(b). Additional information is available on the EPA TMDL website, including the policy memo “Establishing Total Maximum Daily Load (TMDL) Waste-Load Allocations (WLAs) for Stormwater Sources and NPDES Permit Requirements Based on Those WLAs.” This memo clarifies EPA’s policy on waste-load allocations (WLAs), specifically that NPDES-regulated stormwater must be included in the WLA component of the TMDL and affirms EPA’s view that an iterative, adaptive management BMP approach is appropriate.

Stormwater Provision in SAFETEA-LU

The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) modified the eligibility of Federal-aid funds to participate in environmental restoration and pollution abatement (stormwater runoff) activities to minimize or mitigate the impacts of transportation projects. According to FHWA guidance, this section primarily deals with the impacts of transportation facilities that were built prior to the current, more stringent requirements for abatement of stormwater runoff. These transportation facilities may have been constructed with limited or no stormwater treatment controls.

The guidance specifies that SAFETEA-LU provides the means to fund retrofits and the construction of stormwater treatment systems to address water pollution and environmental degradation that is caused in whole or in part by a transportation facility. These measures may be implemented under two basic scenarios:

    • a stand-alone project, one that is developed solely to address stormwater concerns and is not associated with a transportation project that is being developed or is under construction; or
    • in conjunction with a project that is currently being developed for the reconstruction, rehabilitation, resurfacing, or restoration of a transportation facility. In this case, the costs for environmental restoration and pollution abatement may not exceed 20 percent of the total cost of the project.