Bridge Stormwater Runoff Analysis and Treatment Options (2014)

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9 State of the Practice This chapter describes the state of the practice for bridge deck runoff based on a literature review and DOT survey. It gives a general overview on how and when DOTs are conveying and treating runoff from bridge decks, and discusses the mechanisms for pollution discharge from bridge decks. It provides a state of the practice for mitigation of bridge deck runoff water quality. The first section gives an overview of BMPs used for bridge deck runoff, including source control and treatment BMPs. The second section discusses the regulatory requirements as they pertain to runoff from bridges. Clean Water Act regulatory programs are generally delegated to the states for implementa- tion and enforcement (the EPA is responsible for NPDES per- mitting in the non-delegated states of Idaho, Massachusetts, New Hampshire, and New Mexico, as well as in U.S. territories, tribal lands, and the District of Columbia) and states may have their own environmental laws for stormwater runoff. Accord- ingly, the regulatory programs are discussed in general. The practitioner must contact the state environmental agency or EPA, as appropriate, for jurisdiction specific requirements. The final section of this chapter discusses the impact of bridge deck runoff on receiving waters. This discussion is based on several recent studies investigating the potential for receiv- ing water impairments from stormwater runoff from bridge decks. In general, bridges in rural areas will have no significant impact on receiving water quality and should implement the applicable source control BMPs discussed in Chapter 4. Bridges in urban areas have the potential to contribute to impairment of beneficial uses and, if treatment controls are determined to be required, the BMPs described in Chapter 5 and the Tool described in Chapter 6 can help the practitioner determine the optimum BMP type and treatment location. 2.1 State of the Practice for Bridge Stormwater Management This section describes the current state of the practice for bridge deck runoff management and BMP application. The information in this section is based on the findings from the literature review and DOT survey. This information can assist the practitioner in determining what is considered the cur- rent standard of care and practicable by other DOTs. 2.1.1 Systems for Bridge Deck Runoff Capture NCHRP Report 474, Volume 1 identified bridge deck runoff practices for bridges crossing receiving waters as follows. • Discharging runoff through multiple open scuppers directly into the receiving water. • Discharging runoff through piping down from the bridge deck along or through the columns or piers directly into the receiving water without treatment. • Conveying the stormwater runoff over the surface of the bridge to one or both abutments for discharge or treatment by a BMP. • Detaining and treating the stormwater under the bridge deck where overbank areas are available. • Conveying the stormwater runoff via piping or open gut- ters over to one or both abutments for BMP treatment or discharge. Bridge deck runoff conveyance systems, whether taking the form of piping to the receiving water, to the abutment, or by conveyance of runoff on the bridge deck, are generally more expensive than conveyance on a standard at-grade roadway section. Deck drainage systems have the following potential technical design issues that can increase design, construction, and O&M costs for the bridge: • Longitudinal slope on bridges can be very low, requiring increased pipe size or increased deck area in the shoulder to convey runoff; • Deck drain and pipe systems are prone to clogging and/or freezing due to relatively small conveyance areas; C H A P T E R 2

10 • Pipe joints must have sufficient flexibility to move consis- tent with the allowable expansion of the bridge joint; • Pipe systems may not be compatible with the aesthetics of the bridge; • The additional weight of the pipe system may require a larger bridge cross section; • Deck drain or scupper maintenance is hazardous and may interrupt traffic flow due to limited shoulder area to work; and • Pipe materials can corrode and leak. By contrast, conventional roadway cross sections generally have a relatively wide shoulder for safety and conveyance of flow. Longitudinal and/or cross culvert systems are also gen- erally available to collect roadway runoff or the flow can be dispersed in the right-of-way or conveyed in open vegetated systems to receiving waters. There are few published references on the state-of-the-art for bridge deck runoff mitigation for water quality. The most complete reference is based on surveys of DOTs as a part of NCHRP Report 474, Volume 2 (2002). NCHRP Report 474, Volume 2 gives an excellent summary on the state of the practice for bridge deck runoff mitigation practices. Other published literature focuses on the practicability of treat- ment BMPs for bridges and source controls applicable to bridges, such as the study completed by the North Carolina DOT (URS 2010). The DOT survey described in NCHRP Report 474, Volume 2 included a question on whether DOTs treat runoff from bridge decks. Of the 50 states surveyed, 16 responded that they had built or planned to build a structural mitigation system for bridge deck runoff. The reasons given (with number of times the response was noted in parentheses) for the structural miti- gation system included: • Requirement of a watershed plan (2) • Potential for hazardous materials spills (3) • Pressure from environmental group (3) • 401 or Coastal Zone Act Reauthorization Amendments (CZARA) requirement (3) • Sensitive receiving water – municipal supply (4) • Endangered species in receiving water (2) • NPDES permit conditions (1) • Outstanding national resource water (3) The DOT survey completed to support this guide was not as comprehensive as the one previously performed for NCHRP Report 474, Volume 2; however, it was developed as a com- panion effort by gathering similar information to determine if the state of the practice had progressed significantly in the 11-year period since the previous survey was published. Nine DOTs were surveyed as a part of the update for this guide: • Florida DOT (FDOT) • Massachusetts DOT (MassDOT) • Louisiana Department of Transportation Development (LADOTD) • Maryland State Highway Administration (MDSHA) • Nebraska Department of Roads (NDOR) • North Carolina Department of Transportation (NCDOT) • South Carolina Department of Transportation (SCDOT) • Texas Department of Transportation (TxDOT) • Washington State Department of Transportation (WSDOT) A discussion of the results of the survey update follows and shows that the concerns and current practice as identified in the NCHRP Report 474, Volume 2 survey remain relatively unchanged, with a general preference by DOTs not to install bridge deck treatment and conveyance systems due to their high capital and operation and maintenance cost compared to the apparent benefit. 2.1.2 DOT Runoff Management Strategies for Bridges: Highlights from Interviews Most DOTs surveyed discharge deck runoff through scup- pers (horizontal openings in the railing wall) to the receiving water. This type of design approach is the most cost effective and has the least maintenance cost over the life of the facility. Alternatives to the approach are used when the bridge crosses sensitive receiving waters, and the environmental document or resource agency permit requires some form of deck runoff treatment. FDOT uses a simple four-step progressive process for eval- uation of options. • Drain on the deck shoulder to a storm drain system at the abutment. • Direct discharge to receiving water. • Compensatory treatment at an offsite location. • Closed conduit collection system. Other DOTs (e.g., LADOTD, MassDOT) had no special or additional designs beyond the standard guidelines pro- vided in FHWA Hydraulic Engineering Circular No. 21, or the state’s stormwater handbook. States emphasized that design approaches were developed on a site-by-site basis because of requirements in the environmental documen- tation process, and what was considered MEP treatment for the site. MDSHA does not apply different treatment standards to bridges as compared to any other section of

11 highway. In one case, MDSHA raised the lip height of scup- pers to avoid direct discharge of the first flush. If possible, MDSHA does not use scuppers and conveys runoff to the abutment if it is technically feasible without increasing the required deck area. MDSHA generally treats an equal amount of impervious highway surface at an offsite loca- tion in lieu of treating deck runoff, if the bridge crosses environmentally sensitive waters. General bridge deck runoff handling strategies for cross- ings over sensitive receiving waters were focused on “moving the runoff off of the bridge if possible and treating it in upland areas at the approaches.” As WSDOT indicated, “Just getting deck runoff to a treatment site can be a significant techni- cal problem; there is not a lot of hydraulic head available.” Force mains or pumping off bridges (non-gravity depen- dent approaches) were not considered MEP or sustainable solutions. The MassDOT noted that, “options for bridge deck runoff treatment are few” and “success in piping deck runoff” is bet- ter on shorter spans (Barbaro 2012). Thus, MEP is different for bridges than it is for conventional roadway sections. The LADOTD conveys and treats runoff from only one (1) bridge site at this time, a case in which a bridge crosses a sen- sitive water body and drinking water supply (Harris 2013). The TxDOT and MassDOT also referenced the importance of drinking water supplies and treatment of deck runoff in those areas (Barbaro 2012) (Foster 2012). 2.1.3 Considerations and Limitations of Conveyance and Treatment as Identified by DOTs DOTs identified the following considerations related to runoff mitigation strategies during personal interviews. • Resource agency requirements/specifications. Nearly every DOT indicated that the design and operational dif- ficulties with bridge conveyance systems are such that bridge runoff tends only to be treated if resource agencies specifi- cally require it. For example, the NDOR will treat bridge runoff, “when it is requested by Game & Parks/Fish and Wildlife Service following project consultation.” Likewise, the LADOTD treats runoff, “in accordance with resource agency permit.” TxDOT also indicated it treats bridge deck runoff only if there is a regulatory requirement to do so; “typically, this is tied to 401 certification of very large Indi- vidual 404 permits (more than 1,000 linear feet or 3 acres of impact to waters of the United States), a rare event.” In North Carolina, the decision to treat deck runoff is based on specific considerations, such as water quality classifications of the waters to which the bridge discharges, Endangered Species Act issues, and on whether the bridge is being newly constructed and has physical attributes that facilitate treat- ment. Other regulations that potentially drive treatment for NCDOT include the Clean Water Act 401 certifications and state regulations on nutrient-sensitive waters. • Pipe size limitations. Some DOTs (e.g., FDOT, WSDOT) will pipe stormwater off bridge decks if required by a regu- latory agency; however, girder size can constrain the size of the pipes that can be used. For example, the DOT could only convey about 91% of the 2-year storm in the sample case provided. • Maximum spread. Some bridge projects can accommo- date runoff in the shoulder and convey it to the abutment without widening the deck; however, if runoff spreads into the travel lane, it increases hydroplaning potential and risk of accidents. On long flat bridges, the spread tends to expand rapidly. • Gutters. Some DOTs have been successful in using a gutter system, draining to the abutment for treatment. Research in North Carolina suggested that gutters might be impli- cated in the concentrating of pollutants. Nearly all DOTs contacted said that treatment for new construction projects is determined on a project-by-project basis with resource and regulatory agencies as part of the project-planning phase. Where states consider retrofit mea- sures, those may be selected and designed through the DOT’s Highway Stormwater Retrofit Program to meet site-specific water quality goals (NCDOT 2008). NCDOT avoids direct discharge off bridge decks and, when- ever possible, they try to discharge to the overbank and collect and convey the stormwater to the stream in a manner that does not cause erosion. On lower ADT secondary bridges, NCDOT is replacing the structures if needed and not add- ing stormwater treatment mechanisms. Level spreaders and energy dissipaters in the overbank area are the most common method to minimize erosion. Additional treatment is pro- vided in consultation with regulatory agencies. Nearly all of the DOTs contacted are dealing with bridge deck runoff on a case-by-case basis. Treatment of bridge deck runoff is far from standard, due to the technical difficulties of conveyance and treatment, and the relative benefit that treatment can produce as compared to other locations in the highway system. 2.1.4 Source Control Approaches Street sweeping, catch basin and scupper cleaning, deck drain cleaning, deicing controls or changes to deicing meth- ods, snow management, traffic management, and manage- ment of maintenance activities were all cited by DOTs as options to improve bridge deck runoff water quality.

12 Reduced salt usage is one of the best source control actions a DOT can take in areas where receiving water hardness is prob- lematic and salt is applied for deicing. For example, Caltrans implemented a reduced salt-use policy that requires their dis- tricts to develop specific route-by-route plans (NCHRP 2004). The policy mandates that: Snow removal and ice control should be performed as necessary in order to facilitate the movement and safety of public traffic and should be done in accordance with best management prac- tices with particular emphasis given to environmentally sensitive areas (NCHRP 2004). During the first winter of implementation, Caltrans reduced salt usage by 62% statewide as compared to the previous win- ter, helped by improved control of the application frequency of deicing salt (Caltrans 2004). Street sweeping is one of the most common source control approaches in MS4s and some states are considering apply- ing this measure to bridges. The benefits of sweeping are dif- ficult to discern in outfall water quality. The direct benefit to stormwater quality or effect on receiving waters of this sedi- ment removal has not been conclusively defined. This may be because the build-up of material on roadways occurs rela- tively frequently and rapidly reaches a relative equilibrium where material is transported to the shoulder areas by wind energy. NCDOT (2010) states, Additional investigation is needed to establish the effectiveness of bridge sweeping as a BMP (BMP for stormwater) and to pro- vide potential improvements to existing sweeping practices to benefit stormwater quality. NCDOT conducts sweeping practices for many existing bridges throughout the state because of the associated maintenance and safety benefits . . . NCDOT does not currently conduct bridge sweeping to specifically address storm- water quality concerns; . . . (however), because of the potential to remove sediment, bridge sweeping should continue to be consid- ered as a potential water quality treatment BMP for bridge decks. Other DOTs are reviewing bridge sweeping as a viable alternative for stormwater treatment of deck runoff, particularly when other methods of treatment are not feasible or are cost-prohibitive. In addition, potential improvements to existing sweeping practices should be considered, including equipment upgrades and train- ing for sweeper speed and maintenance. Additional study is rec- ommended to further evaluate sweeping as a BMP and to shape sweeping practices (including frequency, type of equipment, and disposal practices) to maximize the benefit for stormwater qual- ity (NCDOT and URS 2010). NCDOT has used sweeping as a negotiated stormwater con- trol measure. For example, on Currituck Bridge, it was not pos- sible to install a collection system for technical reasons. The regulatory agency agreed that sweeping was an acceptable mea- sure, performed through a public private partnership (PPP). Other state transportation agencies, such as MDSHA, are working on strategies to increase the sweeping frequency on bridge decks. The anti-icing material is needed on the road- way November to April (when rain might freeze), so sweep- ing during this season is not required. Currently, MDSHA is working to optimize the sweeping frequency for bridge decks outside of the period when deicers and traction aides are used. MDSHA is also required to report the pounds of sediment collected by sweeping by watershed. This can be difficult to accomplish since sweeper routes are not dictated by water- shed boundaries. MDSHA supports highway sweeping but at a different frequency than the regulatory agency would pre- fer. More definitive study on the frequency of sweeping for bridge decks would be beneficial. Where sweeping is found to be practical and beneficial to deal with particulates, new high-efficiency street sweeping machines may be economical in urbanized areas. DOTs have shared a number of other source control prac- tices that include the following: • “Smart” in-vehicle application technology involving GPS and electronic sensing might make it feasible to use special deicers on bridges or not use them at all, depending on the environmental variables. • Reviewing deicing practices with respect to bridges. • High efficiency catch basin cleaning is being considered along with high efficiency sweeping in some states. • PFC and/or open graded friction course (OGFC) pave- ment. TxDOT and NCDOT have invested in research on the water quality benefits of PFC and/or OGFC pavement. Data from North Carolina indicated that the water qual- ity benefits last as long as the structural life of the pave- ment, even though no maintenance at all was performed. NCDOT confirmed that as long as the road has speeds over 45 mph, pavement maintenance for PFC could be avoided without a loss of permeability in the overlay. NCDOT has a current PFC research project underway. WSDOT indicated they would consider OGFC as a wearing course, but OGFC “gets damaged with studded tires.” MassDOT indicated they are pursuing BMP credit for the considerable quantity of OGFC the state is using. • Bio-sorption activated media are being explored by Florida researchers for filtration in the deck drain. This technology is already in use, in greater quantities, in roadside BMPs. Some DOTs confine source control to DOT operations only. For example, during construction and maintenance projects, LADOTD limits materials placed on bridges to only that nec- essary, with special attention to cleaning materials, solvents, and/or fuels. Only non-phosphate solutions are allowed for cleaning bridge structures. During de-icing events, minimum amounts of de-icing agents are used. MassDOT no longer places sand on bridges and many DOTs have dramatically reduced sand usage, for both air and water quality purposes.

13 Other DOTs are contemplating how vehicle sources could be better controlled, outside of reducing vehicle spray through greater use of PFC. For example, NCDOT is interested in determining if rumble strips prior to the bridge deck could shake off pollutants from the undercarriage of vehicles, to minimize the pollutants that are being carried onto bridges and being sprayed off splash, during precipitation events or are deposited during dry weather. Engineers have noticed concentrations of oil and grease where there are irregulari- ties in the roadway surface. BMPs along the approach sec- tions could be used to treat runoff from the area’s tributary from rumble strips. This idea has been carried forward in the research needs portion of this project. 2.1.5 Other Strategies Treatment at bridge approaches may include detention ponds, grass swales, or buffers; however, treatment at bridge approaches is not always feasible. For example, MDSHA noted that treatment near the bridge approach is infeasible in cer- tain areas due to the extent of the 100-year floodplain and wetland regulation. In low-lying coastal areas, the floodplain may be wide and wetlands extensive in the area of the bridge project, in addition to the difficulties with draining water on long, flat bridges. In such cases, off-site mitigation is con- sidered. Stream buffer regulations can also restrict a DOT’s ability to treat stormwater at bridge approaches. NCDOT cited instances of buffer regulations where NCDOT, “can’t discharge into Zone 1 (30 feet) and in some cases Zone 2 adjacent to the receiving water.” Two state DOTs interviewed (WSDOT and SCDOT) said they were treating bridge deck runoff in a vault. WSDOT completed a project in Riverton, WA, where they used infil- tration vaults to treat and infiltrate runoff from the bridge in the abutment area. In a case over a shellfish area and Outstanding Resource Water (ORW), SCDOT has a closed system and Stormceptor© device treating drainage from one direction (the other could be piped to an upland detention site); however, SCDOT indicated that the closed system approach, “isn’t very practical. Stormcep- tors are only modestly effective in treating for sanitary quality.” Consideration of off-site mitigation options is becoming a standard part of the bridge deck runoff evaluation process in Florida and Maryland. South Carolina is, “developing a crite- ria based on surface area of the bridge.” • Maryland SHA and the Maryland Department of Environ- ment established a water quality bank that allows for per- mitting highway projects that cannot meet all storm water water quality requirements. The water quality credit is established through off-site mitigation at the 6-digit HUC watershed level and the currency is acres of impervious surface treated. The positive balance in the bank is kept by implementation of various water quality projects designed to treat unmanaged impervious surfaces. • FDOT tries to collaborate with co-permittees and “pay for off-site improvements.” FDOT is taking advantage of the current political environment to press for off-site treat- ment; last year, the state legislature passed a bill mandating that the state regulatory community allow flexible treat- ment approaches for transportation. That bill specifically named watershed level treatment and other strategies. South Carolina DOT is performing modeling to under- stand the impacts of bridge deck runoff, as is TxDOT. TxDOT has an ongoing project entitled, “Contribution of Bridge Dwelling Birds to Bacterial Water Quality Impairments.” 2.2 Overview of Regulatory Requirements 2.2.1 NPDES Permits Section 402 of the Clean Water Act (CWA) requires opera- tors of MS4 to obtain coverage under the NPDES permit pro- gram to discharge stormwater runoff to waters of the United States; DOTs must obtain Permit coverage for their systems. Permitting details vary from state to state, including the geo- graphic extent of required coverage and the type of NPDES permit issued to the DOT. The 2010 NCHRP Project 25-25(56) report, “Cost and Benefit of Transportation Specific MS4 and Construction Permitting,” provides an excellent discussion of the NPDES permitting program and its application to DOTs. The NPDES program was implemented by the EPA in two phases. Phase I permits were issued starting in 1990 and Phase II permits were issued starting in 2003. The Phase I program applies to urban areas with populations greater than 100,000. The Phase II program generally applies to urban areas with populations greater than 10,000. NPDES permits may be issued individually or collectively to two or more permittees. The geographic coverage area of the permit generally falls within the census areas for popula- tions defined as urbanized, although the permitting authority may designate other areas if they are deemed a threat to receiv- ing water quality. NPDES permits are also issued for industrial facilities. Industrial facilities include construction sites. Indus- trial permits are usually issued by the permit authority on a statewide basis, applicable to specified industry classifications. A DOT may be covered by an NDPES permit in a variety of ways. The alternatives are: • Phase I individual permit coverage for all DOT facilities or only those in urbanized areas. • Phase I individual permit coverage that includes industrial facilities and construction sites for all facilities statewide.

14 • Phase I permit coverage as a co-permittee with other Phase I entities, only in Phase I coverage areas. • Phase II individual permit coverage for all DOT facilities. • Phase II permit as a co-permittee only in Phase I and Phase II coverage areas. Phase I and Phase II permits have modestly different requirements. Phase I permits pre-date the Phase II permits and generally have more stringent requirements, particu- larly with respect to monitoring and sampling. The require- ments of Phase II permits reflect the more limited resources of smaller cities and capitalize on the information gained through the Phase I program to simplify implementation, monitoring, and reporting. Most Phase I and Phase II permits have provisions for new construction and reconstruction projects, as well as for operation and maintenance of highway facilities. These per- mit sections are of interest to the practitioner when deter- mining BMP requirements for a new or reconstructed bridge. The permit requirements are generally translated into design guidance in the form of a handbook or manual by the DOT. 2.2.2 Wetland Permitting Section 404 of the CWA requires entities that wish to dis- charge fill material or to dredge material from waters of the United States to obtain a permit. Bridge construction nearly always requires a Section 404 permit, issued by the USACE, unless the bridge will span the jurisdictional area, and there will be no temporary impacts (e.g., cofferdam construction or falsework) within the jurisdictional area. This is rarely the case, and obtaining a 404 permit for bridge construction is routine. The USACE will consult with the Department and Fish and Wildlife and the National Marine Fisheries service as appropriate in developing the 404 permit. Section 401 of the CWA requires the State to certify that the dredge or fill operation permitted under Section 404 will not adversely affect the receiving water beneficial uses. The Section 401 cer- tification may contain requirements for the DOT to construct and maintain BMPs (source controls and treatment controls, both during construction and post-construction) to ensure protection of receiving water beneficial uses. Waters of the United States include essentially all surface waters such as all navigable waters and their tributaries, all interstate waters and their tributaries, all wetlands adjacent to these waters, and all impoundments of these waters. The waters of the United States include (1) All waters which are currently used, or were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters that are subject to the ebb and flow of the tide; (2) All interstate waters including interstate wetlands; (3) All other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds, the use, degradation or destruc- tion of which could affect interstate or foreign commerce including any such waters: (i) Which are or could be used by interstate or foreign travelers for recreational or other purposes; or (ii) From which fish or shellfish are or could be taken and sold in interstate or foreign commerce; or (iii) Which are used or could be used for industrial pur- poses by industries in interstate commerce; (4) All impoundments of waters otherwise defined as waters of the United States under this definition; (5) Tributaries of waters identified in paragraphs (1)-(4); (6) The territorial seas; and (7) Wetlands adjacent to waters (other than waters that are themselves wetland) identified in paragraphs (1)-(6). The lateral limits of jurisdiction of waters may be divided into three categories: the territorial seas, tidal waters, and non- tidal waters (see 33 CFR 328.4 (a), (b), and (c), respectively). More specifically, CFR 328.3(a) provides the following clear definition of waters of the United States: Waste treatment systems constructed in upland areas, including treatment ponds or lagoons designed to meet the requirements of the CWA (other than cooling ponds as defined in 40 CFR § 123.11(m) which also meet the criteria of this definition) are not waters of the US 33 CFR § 328.3(a); 40 CFR § 230.3(s). Adjacent wetlands subject to CWA Section 404 jurisdic- tions are those that are bordering, contiguous, or neighbor- ing to other waters of the United States. Frequently, the term “wetlands and other waters of the United States” is used when describing areas under USACE jurisdiction. For the regulatory process, the USACE and EPA jointly define wetlands as follows: Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegeta- tion typically adapted for life in saturated soil conditions. Wet- lands generally include swamps, marshes, bogs, and similar areas (EPA, 40 CFR 230.3 and USACE, 33 CFR 328.3). The USACE is primarily responsible for implementing the CWA Section 404 program. Section 404 of the CWA establishes a permit program administered by USACE that regulates the discharge of dredged or fill material into waters of the U.S. Section 404(b)(1) guidelines allow the discharge of dredged or fill material into the aquatic system only if there is no practicable alternative that would have less adverse effects. The purpose of the Section 404 program is to ensure that the physical, biological, and chemical quality of our nation’s water

15 is protected from irresponsible and unregulated discharges of dredged or fill material that could permanently alter or destroy these valuable resources. The USACE Regulatory Program administers and enforces Section 10 of the Rivers and Harbors Act of 1899 and Section 404 of the CWA. Under the Rivers and Harbors Act, Section 10, a permit is required for work or struc- tures in, over or under navigable waters of the United States. Under CWA, Section 404, a permit is required for the discharge of dredged or fill material into waters of the United States. The USACE regulatory authority under the Rivers and Harbors Act of 1899 is limited to traditional “navigable waters.” Traditional navigable waters regulated by Section 10 are waters that are, could be, or were once used to transport interstate or foreign commerce. In contrast, “waters of the US” regulated under Sec- tion 404 also include “other waters” such as wetlands that have a sufficient nexus to interstate commerce. In practice, USACE regulatory authority under the Rivers and Harbors Act has been integrated with regulatory authority under the CWA, and USACE uses one permit application for both types of permits. Figure 2-1 illustrates the USACE lateral extent of jurisdic- tion under Section 10 and Section 404. 2.2.3 CWA Section 401 Water Quality Certification Although a federal regulation, 401 Water Quality Certifica- tion is largely issued by individual states, typically by their water quality or environmental departments. Over the past several years, states have generally expanded the application of Section 401 certification to waters and wetlands. Some states rely on Section 401 certification as their primary mechanism to protect wetlands in the state. In addition, most states denied certifica- tion of some nationwide permits because they believe that indi- vidual review of projects in isolated and headwater wetlands is critical to achieving CWA goals in their states. States have also increased their regulatory authority as the USACE’s jurisdiction has decreased due to recent U.S. Supreme Court cases. Overall, Section 401 certification allows states to address associated chemical, physical, and biological impacts such as low dissolved oxygen levels, turbidity, inundation of habitat, stream volumes and fluctuations, filling of habitat, impacts on fish migration, and loss of aquatic species because of habi- tat alterations or the deposit of dredge or fill material. 2.3 Evaluation of Receiving Water Impacts As owners of state highways and bridges, DOTs are inter- ested in discerning whether contamination of water bodies from roads and bridges is significant, and, if so, what mitiga- tion is appropriate. The purpose of this section of the guide is to summarize the published information on bridge runoff quality and its impacts on receiving waters. 2.3.1 Bridge Deck Runoff Quality Several studies have been undertaken to evaluate whether bridge deck and roadway runoff quality were significantly dif- ferent. The most comprehensive study to date was conducted by URS Corp. for NCDOT. The URS study (2010) found “no Figure 2-1. USACE regulatory jurisdiction in fresh waters.

16 compelling evidence that bridge deck runoff in North Caro- lina is higher in pollutants typically associated with storm- water runoff as compared to runoff from other roadways.” Of all the characteristics investigated by URS, the urban versus rural designation appears to have the most influence on pol- lutant loading. All solids parameters studied were higher in urban areas, as well as most total recoverable metals and dissolved copper and lead. In a study funded by TxDOT, Malina et al. (2005) also showed that bridge deck runoff is generally not statistically different from highway runoff. In a comparison of bridge deck runoff event mean concentrations (EMCs) to the approach highway EMCs, there were only limited instances when param- eters were significantly different from each other. Malina et al. concluded that highway runoff data could be used as a con- servative approximation of bridge deck runoff quality. Malina et al. also found that loading of all measured water quality constituents was minimal, with “no substantial adverse impact to the receiving streams . . . observed or indicated by bridge deck runoff from the three monitored sites.” Loadings from upstream sources were several orders of magnitude greater as compared to the loading from the bridge deck. As Nwaneshiudu (2004) and others have pointed out, “Most of the pollution found in highway runoff is both directly and indirectly contributed by vehicles. The constituents that con- tribute the majority of the pollution, such as metals, chemical oxygen demand, oil and grease, are generally deposited on the highways.” Consequently, roadway runoff water quality data should be used as an approximation for the pollutant profile of bridge deck runoff (Dupuis et al., 2002). As part of this project, the National Stormwater Quality Database (NSQD, version 1.1) and the FHWA database were analyzed to determine typical constituent concentrations in highway runoff. The results of this analysis are presented in Table 2-1 with the column titled “All Data” showing the median for all available data regardless of traffic volume. It is clear from looking at the data that the concentrations of pollutants associated with vehicles, such as TSS, total copper, and total zinc, are correlated with AADT. NCHRP Report 474 reviewed scientific and technical lit- erature addressing bridge deck runoff and highway runoff performed by FHWA, USGS, state DOTs, and universities, focusing on the identification and quantification of pollut- ants in bridge deck runoff and how to identify the impacts of bridge deck runoff pollutants to receiving waters using a weight-of-evidence approach. Although undiluted highway runoff can exceed federal and state ambient water quality criteria, this alone does not automatically result in nega- tive effects to receiving waters. Dupuis et al. found no clear link between bridge deck runoff and biological impairment in the receiving water, though noted that salt from deicing could be a concern. 2.3.2 Receiving Water Studies In the meta-analysis of existing studies, Dupuis et al. showed that while several studies had shown direct drainage to some types of receiving waters (e.g., small lakes) could cause localized increases in certain pollutant concentrations, most studies did not consider whether such increases adversely Constituent Annual Average Daily Traffic 0 – 25K 25K – 50K 50K – 100K 100K + All Data TSS (mg/L) 43 56 94 108 79 NO2+NO3 (mg/L) 0.385 0.61 0.62 0.805 0.64 NO3 (mg/L) 0.2 0.83 0.6 1.1 0.6 TN (mg/L) 1.44 4.69 2.57 2.725 2.64 TKN (mg/L) 0.84 1.794 1.7 2.1 1.6 DP (mg/L) 0.072 0.105 0.0745 0.17 0.09 TP (mg/L) 0.12 0.16 0.2 0.237 0.2 T Cu (µg/L) 9.3 20 32 50 24 T Pb (µg/L) 6.6 12.7 74 46 32 T Zn (µg/L) 60 93 180 270 130 Fecal Coliform (#/100 ml) 5000 NA 4150 1700 50 E. Coli (#/100 ml) NA NA NA NA 1900 Table 2-1. Median concentrations of typical highway runoff constituents.

17 affected the biota or other receiving water uses. In addition, the study did not consider whether observed increases could be attributed at least partially to dry deposition. The only comprehensive study of bridge runoff at that time, FHWA’s I-94/Lower Nemahbin Lake site, found that although direct scupper drainage increased metals concentrations in near- scupper surficial sediments, biosurveys and in situ bioassays found no significant adverse effects on aquatic biota near the scuppers. FHWA concluded that for lower traffic volume bridges at least, runoff had a negligible impact on receiving waters (Dupuis et al. 1985a). Dupuis (2002) also reported that the results of bio assay testing using whole effluent toxicity from various studies have been mixed. For the studies that do show some level of toxicity, the runoff samples were high in salt content from deicing activities. However, the bioassay methods used by these studies may not be appropriate for evaluating storm- water runoff. Most bioassays expose the organism being testing continuously to runoff for long periods. However, storm- water runoff is delivered to receiving streams in short, inter- mittent time frames. URS (2010) completed a comprehensive study of bridge deck runoff for the NCDOT. In this study, the authors note that, “The effects of stormwater runoff on aquatic biota need to be evaluated across different time scales,” and they refined a time-variable bioassay procedure to reflect the conditions found during runoff events from bridges. The original appli- cation of time-variable bioassay approach for bridges appears to have been conducted as a part of NCHRP Report 474: Assessing the Impacts of Bridge Deck Runoff Contaminants in Receiving Waters. The NCDOT study (URS 2010) (1) quantified the con- stituents in stormwater runoff from bridges across the state, (2) evaluated the treatment practices that can be used to reduce constituent loadings to surface waters from bridges, and (3) determined the effectiveness of the evaluated treatment practices. NCDOT summarized conclusions from previous studies: • Pollutant loadings from bridge decks to a receiving stream are minimal when compared to pollutant loadings from other watershed sources. • Specific instances of elevated parameters, particularly zinc, may be linked to galvanized bridge materials. • While several parameters-of-concern from bridge deck runoff exceeded site-specific surface water quality thresh- olds, the analyses associated with aquatic toxicity, biological assessments, and sediment data did not indicate long-term adverse impacts from untreated bridge deck discharges. • Deicing activities and pollutant accumulation in sediment are potential sources of localized toxicity that require fur- ther study. NCDOT concluded that these observations . . . support the concept that surface water quality protection may be better served by managing stormwater runoff on a watershed scale as opposed to focusing management efforts spe- cifically on bridges. In addition, there may be opportunities to improve water quality by identifying and controlling the source of pollutants (e.g., by replacing certain bridge materials). NCDOT also developed a treatment scheme and estimated costs. In the study for NCDOT, URS (2010) found no statis- tically significant differences in sediment pollutant con- centrations upstream and downstream of the bridge, for either bridges that do not directly discharge to receiving water or direct discharge bridges. Overall, the URS analy- sis of streambed sediment did not indicate any impacts of bridge deck runoff on sediment quality. Ecoregional dif- ferences were observed for some analytes but these differ- ences appeared to be associated with naturally occurring conditions or upstream anthropogenic influences. Further- more, where sediment quality benchmarks were exceeded, except for lead and mercury, the exceedances were found to be independent of the discharge drainage design from the bridge (i.e., direct versus indirect) and also were found to occur either upstream of the bridge deck, or at similar levels upstream and downstream, indicating sources other than bridge deck runoff. Bartelt-Hunt et al. (2012) investigated the impacts of bridge runoff and receiving water quality at four bridges in Nebraska for NDOR. The objectives of this research were to evaluate the quality of bridge deck runoff; to determine the effects of bridge deck runoff on surface water bodies in Nebraska by evaluating water and sediment chemistry; and to evaluate the effects of bridge deck runoff on aquatic life. The goal was to identify the potential environmental impacts of bridge deck runoff on receiving streams and to determine design criteria that could be used by NDOR or regulatory agencies to iden- tify when structural controls for bridge deck runoff may be necessary to protect in-stream water quality and aquatic life. Throughout the course of the project, in-stream dry weather sampling, sediment sampling, wet weather bridge runoff sam- pling, and preliminary toxicity testing were conducted. Statis- tical analysis of in-stream samples upstream and downstream of bridges showed that bridges did not impact the quality of the receiving water body. Sediment sampling did not show an increase in streambed sediment concentrations from down- stream to upstream. Two runoff events were also used in a 48-hour 5 dilution series toxicity test with fathead minnows, and no negative effects were found. These results show that there were no observable effects of bridges on water quality and aquatic life.

18 2.3.3 Stormwater Quantity Impacts Bridge deck runoff quantity can be characterized by runoff volume and peak flow rate, both of which are considerations when evaluating the potential hydrologic effect of bridge deck runoff on receiving streams. Hydromodification should not be an issue from bridge decks alone, since the runoff coefficient is identical to rainfall on the receiving water. 2.3.4 Summary URS (2010) concluded that long-term untreated bridge deck discharges do not have an adverse impact on aquatic toxicity or sediment quality. Additional findings of this review include: • Quality and pollutant loading in bridge deck runoff is similar to roadway and urban runoff; • Concentrations of vehicle-derived constituents are highly correlated with average daily traffic; • Bioassessments made upstream and downstream of bridges found no significant differences; • Periodic toxicity of bridge deck runoff is possible, but not common (periodic toxicity observed may be linked to road- way deicers); • Bridge deck runoff did not contribute to stresses from organ- ics or nutrient enrichment; and • Potential erosion due to concentrated flow from bridge deck drainage systems could impact receiving waters. If the constituents in bridge runoff are not contributing to impairment for a receiving stream, no stormwater treatment should be necessary. However, the same concentration profile might require sophisticated BMPs when paired with a high- quality drinking water source. Therefore, efficient and cost- effective stormwater management, including BMP selection, becomes a function of evaluating highway stormwater charac- terization data with receiving stream surface water quality goals. In an effort to better mitigate the impacts of stormwater run- off, the National Research Council has recently recommended a shift in stormwater management and regulatory permitting to a more watershed-based approach, where discharge permits are based on watershed boundaries rather than political boundar- ies (National Research Council 2009). This type of approach would support the conclusion that treatment of bridge deck runoff is most appropriate in cases where a constituent present in highway runoff has been identified to affect a receiving water beneficial use at very low concentrations, and with very short durations (a matter of hours). NCHRP Report 474 noted, Highways typically constitute a very small fraction of a watershed’s total drainage area, and bridges often constitute a small portion of the highway drainage area. Thus, highways often, but not always, contribute a small fraction of the overall pollutant load to a given receiving water body, and bridges contribute even less. According to NCHRP Report 474, This circumstance provides opportunities to consider and imple- ment commonsense solutions such as providing enhanced pol- lutant removal somewhere else in the right-of-way (ROW), or even somewhere else in the watershed (i.e., off-site mitigation, or pollutant trading).