CHAPTER 5

Summary of Findings

This synthesis aims to document the practices of stormwater retrofits and partnerships within state DOTs and to document the practices of those state DOTs that have an advanced retrofit partnership program. The most notable finding is that nearly two-thirds of responding DOTs participate in some manner in partnerships for implementation of stormwater management, but those partnerships represent a small fraction of the DOTs’ total programs. Generally, 1% to 10% of the DOTs’ stormwater management facilities are implemented through partnerships. The overwhelming majority of the survey respondents do not treat offsite runoff. The state DOTs that do treat offsite flows, with few exceptions, construct these treatments out of engineering necessity, as it is difficult to separate commingled flows. Of the partnerships that exist with state DOTs, the vast majority are with municipal or county governments in urban areas. Only a relative handful are with state or federal agencies, private businesses, or private non-profit organizations.

The driving force that motivates the states active in partnerships seems to be regulatory compliance. Of the four states that participated in the follow-up interviews, each was motivated to participate in regional partnerships by the regulatory climate in their state. Florida’s regulations regarding their karst aquifer have resulted in a partnership project whereby stormwater reuse replaces irrigation water obtained from groundwater wells. FDOT has no retrofit requirement in their MS4 permit. North Carolina has a fixed number of retrofit credits mandated in their MS4 permit, and partnerships allow NCDOT to more easily accomplish the required number of project credits. California has developed a watershed-based system whereby the state water board, through autonomous regional authorities, governs various stakeholders throughout a particular watershed. California’s MS4 permit mandates that Caltrans develop a stormwater asset management plan and complete retrofits for deficient facilities according to that plan. Rhode Island’s efforts are steered to a watershed approach through an EPA consent decree. The language of the decree mandates their MS4 permit to require retrofit facilities to satisfy various impairments within sensitive watersheds. Rhode Island also has a rigorous state-level watershed management culture that enables partnerships.

It is more difficult to ascertain the reasons that some state DOTs do not participate in partnerships or take a regional or watershed approach to developing stormwater treatment facilities. In some cases, the DOT is developing a program, but typically, such partnerships are not considered in their MS4/TS4 permit or there is no demonstrable benefit to their operations to share the benefits and the costs of regional infrastructure. From the literature survey chapter, the EPA MS4 Permit Improvement Guide (2010) encourages MS4 permit writers to include retrofit requirements in permits, as the permittee becomes inclined to accept such requirements.

The survey indicated that only about half the respondents had a formal retrofit program, whereby stormwater treatment measures are constructed to treat runoff from existing facilities. The primary driver for the establishment of a retrofit program is that it is included in the MS4/TS4 permit. About one-fourth of the states with a retrofit program indicated that it is required

by state statute or regulation, and several states listed TMDL reductions and EPA/DOJ consent decrees. Within an individual retrofit program, the most common triggers that require the construction of a retrofit facility is the construction of any new capacity with a substantial increase in impervious area. Therefore, when a DOT expands a facility, they often have to construct treatment for both the expanded area and the original area. The second most common trigger was treatment to address TMDL loadings.

The four most common stormwater facility retrofit techniques used by the survey respondents are the following:

1. Flow-through facilities that capture runoff and filter it
2. Retention facilities that capture runoff and release it through evaporation or infiltration
3. Detention facilities that capture runoff and release it through a metering structure
4. Proprietary stormwater devices that hydraulically separate flows from pollutants

These four techniques were all used by over 50% of the survey respondents. Other techniques that are less widely used include permeable pavements, constructed wetlands and wetland mitigation, stream restoration, land conservation, trash/debris racks in catch basins and inlets, and grass swales.

Fully 60% of the survey respondents indicated that funding for stormwater treatment is included in the cost of the larger transportation project and not separately tracked. However, 37%, indicated that their agencies had a separate fund within the DOT budget to construct permanent stormwater facilities as either part of larger projects or stand-alone projects.

Only four state DOTs—Connecticut, Delaware, Indiana, and New Hampshire—indicated that they have written policies regarding third-party partnerships. One state, California, publishes a brochure that describes two programs they use to establish partnerships. The states that participate in partnerships typically use multiple types of agreements, from funding contributions only, to partnering with a local agency for construction only, to partnering with a local agency with shared responsibilities for both construction and operation. The overwhelming preference among state DOTs subject to follow-up interviews is to provide funding contributions only and rely upon the partners for construction and operations.

Most survey respondents (63%) indicated that they have written guidance regarding the performance, inspection, operation, and maintenance of their permanent stormwater facilities but only for DOT-owned facilities; 14% have guidance for both DOT- and third-party–owned facilities; and 23% have no such guidance. Twenty states provided copies of their guidance documents, and weblinks for this information are included in Appendix D. The types of guidance provided are varied. Twelve of the 20 contain comprehensive information on selection, design, and construction of the facilities along with maintenance and operational strategies, while the remainder are focused primarily on inspection and maintenance.

In establishing partnerships, the ingredients for success include formal mechanisms in the agreement to ensure it persists if responsible staff leave the organization, as well as clearly defined responsibilities and partnership with an agency well equipped to meet their commitments. Also of considerable importance is contingency planning for the unforeseen. Noted obstacles to successful partnerships include varying standards and permit requirements between the DOT and the third party, difficulty identifying which is the lead partner, and agreements forgotten with staff turnover. While the survey asked respondents to list obstacles to partnerships, all four states subjected to follow-up interviews indicated that the partnerships were fruitful. The follow-up states generally noted that partnership projects were more complex to design and construct, with multiple stakeholder needs, but once constructed were more effective from both a cost and a performance perspective.

While several states appear to have a rapidly growing partnership culture in stormwater management, about half the responding DOTs have no experience with such partnerships. Of the four case example states, each indicated that the partners generally initiated partnerships. The states also noted that because DOT right-of-way covers only a small percentage of a typical watershed, the most appropriate role for a DOT is as a contributing partner, not a lead partner.

This synthesis identifies a wide variation in the use of partnerships and the construction of retrofit facilities. Retrofit programs are most often mandated by regulators, and partnerships occur in a random fashion. Future research could further illuminate why. However, numerous DOTs participate in partnerships for reasons other than stormwater retrofits. A better understanding of what motivates both DOTs and third parties to participate in partnerships could result in guidance that would motivate both groups to develop such mutually beneficial partnerships.

The literature survey identifies considerable research on the watershed approach to stormwater management, but further research is needed on how different stakeholders within a watershed can cooperate for mutually beneficial solutions. Understanding the extent that permit boundaries overlap within watersheds and identifying methods that the overlapping permit holders might use to share permit requirements and responsibilities could lead to improvements in water quality performance and cost-effectiveness within a watershed. An increased understanding of how distributed runoff modeling could be used to examine water quality impacts throughout smaller sub-basins of a watershed could lead to more effective partnerships throughout the watershed.

One of the primary drivers of partnerships identified in the case example section is that DOTs have funding streams to provide design funds at the partnership project concept phase, allowing a project to advance to a point when it can attract grant funding from other sources for construction and operation. Additional research could help establish for DOTs and third parties a comprehensive guide on funding partnership projects from conceptual state through design, construction, and operation.

Other research with regard to the economic and funding questions could identify whether retrofit permanent stormwater facility projects provide significant economic and functional advantages over constructing similar facilities only for new capacity or increased imperviousness. If retrofits are found to provide advantages, another research topic would be to explore how MS4/TS4 permitting practices might be modified to encourage retrofit construction to provide a more cost-effective and functional benefit for both DOTs and the receiving waters.

Two other research ideas that could help facilitate partnerships would be the development of a guide for DOTs and interested third parties to advertise their willingness and availability for partnerships or a guide to develop a cost/performance index to aid DOTs and potential partners in planning for improved and more economical permanent stormwater facilities.