CHAPTER 1

Introduction

1.1 Background

State departments of transportation (DOTs) have managed stormwater runoff for many decades for evolving reasons. Initially, the focus was on detaining and slowing the quantity of runoff from urbanized areas for flood protection. Before urbanization, most rainfall is absorbed into the soil and vegetation; any runoff flowing into surface waters is attenuated by these natural processes. The bulk of rainfall is absorbed into the groundwater system and the smaller surface runoff flows remain relatively clean. After urbanization, many previously absorbent surfaces are made impervious. Instead of the bulk of the rainwater being absorbed or filtered, the water flows over roofs, pavements, lawns, and concrete channels, washing away contamination from these impervious surfaces and carrying it into surface waters.

The increased stormwater flows that result from urbanization cause two problems: an increased quantity of water, in both peak flow rate and total volume, to downstream properties and degradation of water quality. In some regions of the United States, detention facilities were included with land development projects to attenuate the peak flows leaving urbanized areas. A common practice was to construct a pond at the downstream end of a developed area. The pond included an outlet structure to release the water at a rate calculated to mimic the natural peak pre-development runoff from the now-developed area. The ponds, however, had no way to mimic the absorption of the rain into the groundwater system.

In 1972, the Clean Water Act was signed into law and marked the start of modern water quality regulation with the establishment of the National Pollutant Discharge Elimination System (NPDES). This system mandated a permit for point source discharges of pollutants into navigable waters and was typically applied to industrial and municipal wastewater sources of pollution. Initially, stormwater runoff was excluded from the NPDES program. Congress modified the Clean Water Act in 1987 to expand NPDES to require permits for stormwater discharge.

In 1990, the EPA established stormwater regulations for large and medium-sized municipal separate storm sewer systems (MS4s) serving populations of 100,000 and more. These regulations are commonly referred to as Phase 1 MS4s. In 1999, the EPA expanded these regulations to apply to MS4s in smaller populated areas. This is commonly referred to as the Phase 2 rule. The overall aim of these permits is to improve stormwater quality for the runoff from transportation infrastructure.

Initially, many state DOTs were permitted in a similar manner to municipalities, but some requirements for municipal stormwater systems did not work well with the linear nature of a highway system. In recognition of this fact, transportation separate storm sewer systems (TS4s) have been developed in some states. In other states, an individual MS4 is tailored to the needs

of the DOTs while in others, a general MS4 is still issued to DOTs. Although the permitting responsibility for MS4s and TS4s is held by the EPA, many states have received authorization to issue these permits.

Stormwater permits held by DOTs contain temporary measures to treat runoff from construction activities and permanent post-construction measures to treat runoff in perpetuity. Construction-stage practices are designed to quickly stabilize exposed soil surfaces and protect receiving waters from sediment and construction materials like diesel fuel and concrete washout runoff. In the planning and design stage, some permits focus their stormwater quality efforts on new capacity or expanded impervious area. Others have expanded to address runoff from existing transportation facilities. In these latter cases, permanent stormwater facilities are constructed to reduce, minimize, and treat runoff from the existing impervious surface, with no expansion of the highway facility.

There is nothing inherently different about the function of stormwater retrofit facilities versus new facilities, as both treat runoff from impervious surfaces. In some state DOTs, permanent stormwater facilities are constructed to address runoff only from expansion of existing or construction of new transportation infrastructure. Other state DOTs retrofit permanent stormwater facilities to address runoff from existing facilities with no associated expansion of capacity or imperviousness. In this synthesis, such facilities are referred to as permanent stormwater facility retrofits.

All permanent stormwater facilities are designed to both attenuate excess runoff quantity and protect receiving waters from pollutants washed off transportation facilities. These pollutants can include road sand, brake lining dust, tire particles, oil, and other automotive fluids, as well as leaves and other natural materials that exist in the highway right-of-way. Sometimes these retrofitted improvements are mandated in an MS4/TS4 permit through quotas or goals. In other instances, retrofits are targeted at sensitive watersheds or heavily populated areas of the state.

At the advent of state DOT MS4/TS4 permits, the focus of permanent stormwater facilities was on treating onsite flows generated from transportation facilities. However, in most instances, state highway right-of-way only impacts a small fraction of the overall area of a particular watershed. Efforts by other adjoining local MS4s typically have much more impact, particularly if much of the remainder of the watershed is impacted by urbanization or causes other than highway runoff.

The development of permanent stormwater facilities can occur on a site-by-site basis, independently by the adjoining local MS4 and the state DOT, or they can form a third-party partnership and develop facilities on a regional basis. Besides the adjoining local MS4s, other types of third parties can partner with state DOTs to develop permanent stormwater facilities. A third-party partnership, for purposes of this synthesis, is a partnership between a state DOT and a municipality or county, a special district, another state agency, a federal agency, a private business, a private non-profit organization, an educational institution, or any combination of these to plan, design, construct and operate and maintain permanent stormwater facilities. Private developers, non-governmental environmental advocacy groups, educational institutions, and non-MS4 governmental agencies are examples of third parties that have partnered in the construction and operation of permanent stormwater facilities.

This synthesis is focused on permanent stormwater facility retrofits and how state DOTs partner with other parties to construct and maintain these facilities. Partnerships on permanent stormwater facilities create opportunities for better treatment of the whole watershed and provide benefits for both the state DOT and the third-party partners.

1.2 Objective and Scope

This synthesis documents the diverse approaches taken by state DOTs regarding stormwater facility retrofit partnerships with third parties. Elements of this effort include identifying the main drivers for retrofit practices in stormwater systems; describing stormwater retrofit practices used; and delineating the type, purpose, and scale of stormwater retrofitting.

Many state DOTs include retrofit practices in their stormwater programs. Fewer include third-party partnerships in the design, site selection, construction, operation, and maintenance of stormwater retrofit projects. This synthesis seeks to identify state DOTs that engage in third-party partnerships and to provide a sampling of their written policies, guidance, and legal documentation regarding these partnerships. The types and spatial distribution of third-party partners are examined, as are the funding mechanisms used for the projects.

Finally, the synthesis examines the performance measures used both for DOT and third-party partnership retrofit projects, as well as identifies existing and potential barriers and benefits of using third-party partnerships in stormwater management.

1.3 Methodology

This synthesis was conducted through both a literature review and an online survey distributed to all the states, Puerto Rico, and the District of Columbia. The results of the online survey are summarized in Chapter 3, and the questions and responses are included in Appendices A and B, respectively.

The survey questionnaire consists of 25 questions designed to identify varying levels of general stormwater efforts among the states, as well as more specific questions regarding retrofits, treatment of offsite flows, and regional- or watershed-level efforts in stormwater quality and flow control. Specific questions also sought information regarding the extent and types of partnerships the state DOT participated in and how those partnerships are structured.

All respondents were asked whether they were willing to participate in follow-up interviews; of the 14 out of 42 who answered affirmatively four were selected to conduct the case example interviews. In addition to state DOTs’ willingness to participate in the follow-up interviews, the synthesis team also considered factors such as climatological and geographic diversity and urban and rural settings.

The four state DOTs that participated in the follow-up case examples were asked questions that sought further details on what drives their practice of stormwater retrofits, as well as details of the retrofits used. The states all provided examples of projects delivered through third-party partnerships and described the types of third parties involved, as well as the funding mechanisms used. All listed several examples of experiences gained through these partnerships and identified barriers and benefits to their use.

The interview questions used for the four state DOTs are included in Appendix C. Each interview took 45 minutes to an hour and upon completion, the DOTs provided written documentation of the specific project examples discussed. A draft of each case example was provided to the DOT for review and comment.