The synthesis methodology includes reviewing relevant literature, collecting information from state DOTs using a survey questionnaire, and conducting case example interviews with state DOTs for in-depth discussions about construction stormwater management. Literature was collected from state DOTs, the FHWA, EPA, AASHTO, and other related documents, manuals, and journal articles. The survey was developed based on information found in the literature review and was distributed to the AASHTO Committee on Construction, which includes representatives from all 50 state DOTs, along with the Washington, DC, and Puerto Rico DOTs. A total of 42 state DOTs responded to the survey, yielding an 81% response rate. Based on the findings from the survey, the DOTs from the following six states were identified and agreed to participate in the case examples: Colorado, Florida, Iowa, New York, Pennsylvania, and Texas.

The information presented covers the scope of the work of this project from the data collected and reviewed. The information reviewed in the literature and the survey reveals that most state DOTs perform stormwater management as part of their project management process. Every state DOT complies with the NPDES CGP requirements at the national or state regulatory agency level. Moreover, the CGP is required for every highway construction project, which the state regulatory or environmental agency typically administers. Some state DOTs also comply with MS4 permit requirements for construction stormwater management, typically addressing the construction site runoff minimum control measure program requirements.

The survey indicates that state DOTs use different approaches to construction stormwater, including the following:

• Participation in the project management process (25 of 42 DOTs, 60%)
• Formal construction stormwater management program (11 of 42 DOTs, 26%)
• Combination of project management process and formal construction stormwater management program depending on project scope and size (6 of 42 DOTs, 14%)

Of 42 responding state DOTs, 33 (79%) have used statewide approaches, while 27 (64%) indicated that the approach to construction stormwater management varies project by project. In the case examples, state DOTs noted they have an office or division at headquarters that helps with the permit process and initiates stormwater management for a project. Subsequently, the districts or regions within the state DOT are in charge of implementing and overseeing compliance with permit requirements for construction stormwater management.

State DOTs use various BMPs and control measures for sediment containment, erosion, and runoff control. BMPs are practices and controls installed at a construction site to help prevent or reduce sediment-laden runoff and erosion. The literature review includes lists of BMPs commonly used for highway construction stormwater management. From the survey responses, 42 of 42 DOTs (100%) use the following BMPs for construction stormwater management:

• Erosion control logs, sediment tubes, fiber rolls, or composite socks
• Check dams, including rock, sandbags, socks, rolls, silt fence, or tubes
• Stabilized construction entrances and exits
• Silt fence and barriers
• Sediment basins
• Temporary or permanent hydromulching/seeding

In addition, 20 of 42 state DOTs (48%) have used flocculants for construction stormwater management. In the case examples, the common BMPs mentioned are silt fences; turbidity barriers; seeding, fertilizing, and mulching; straw bales; sediment logs; drainage interceptors; and check dams. DOTs also mentioned using flocculants as a last resort.

The SWPPP is an important stormwater management component, as it provides stormwater management details specifically for each individual construction site and is required under the CGP for state DOTs to prepare and implement at highway construction project sites. Based on the literature review, common components of the SWPPP include the site map; an assessment of the site to identify potential problem areas, pollutants, and sediment-laden runoff areas; number and location of stormwater management practices, including BMPs and control measures; monitoring and reporting procedures; employee training and education; emergency response plans; and inspection and maintenance schedules.

According to the survey, the main parties responsible for preparing SWPPPs include the following:

• Design engineers (26 of 42 DOTs, 62%)
• Contractors (24 of 42 DOTs, 57%)
• Consultants (21 of 42 DOTs, 50%)

In addition, the survey also identified the main parties responsible for managing SWPPPs during construction, which include the following:

• Contractors (33 of 42 DOTs,79%)
• Construction project managers (26 of 42 DOTs, 62%)
• Consultants (16 of 42 DOTs, 38%)

The survey reported the period during which the SWPPP is prepared by the DOT, which includes the following:

• During project design and engineering (25 of 42 DOTs, 60%)
• During the pre-construction phase (15 of 42 DOTs, 36%)
• Prior to the construction phase (8 of 42 DOTs, 19%)
• In conjunction with the National Environmental Policy Act Plan (4 of 42 DOTs, 10%)

In the case examples, state DOTs mentioned that the SWPPP is a requirement that must be prepared before receiving permit authorization from the state regulatory agency as part of the CGP. Various DOT divisions, offices, and departments are involved in construction stormwater management, including the following:

• Construction (41 of 42 DOTs, 98%)
• Environmental (35 of 42 DOTs, 83%)
• Design and engineering (31 of 42 DOTs, 74%)
• Stormwater management and drainage (23 of 42 DOTs, 55%)
• Permitting (18 of 42 DOTs, 43%)

The common responsibilities of the DOT include the following:

• Development of design guidelines (36 of 41 DOTs, 88%)
• Monitoring and tracking control measures (36 of 41 DOTs, 88%)
• Inspections (35 of 41 DOTs, 85%)
• Training project personnel (34 of 41 DOTs, 83%)
• Reporting (33 of 41 DOTs, 80%)

The common responsibilities of the contractor include the following:

• Installation of BMPs (41 of 41 DOTs, 100%)
• Maintenance of BMPs (39 of 41 DOTs, 95%)
• Deficiency remediation (36 of 41 DOTs, 88%)
• Monitoring and tracking control measures (33 of 41 DOTs, 80%)
• Inspections (31 of 41 DOTs, 76%)

The common responsibilities of consultants include the following:

• Inspections (22 of 41 DOTs, 54%)
• Monitoring and tracking control measures (19 of 41 DOTs, 46%)
• Reporting (17 of 41 DOTs, 41%)
• Development of design guidelines (15 of 41 DOTs, 37%)

In the case examples, state DOTs mentioned they are responsible for providing guidelines, overseeing the management of stormwater and E&SC at the construction site, and inspecting stormwater management controls for the project. Also, the contractor is responsible for properly installing and maintaining stormwater management and associated BMPs. In addition, state DOTs have mechanisms in their specifications that allow them to assess liquidated damages or payment deductions when the contractor is not sufficiently complying with permit requirements.

Various approaches are used to develop design guidelines for stormwater management. The survey and case examples indicate that DOTs have guidebooks and manuals available for design and management during construction, along with guides outlining approved BMPs and control measures. Furthermore, the survey respondents were asked to identify the design guidelines used for construction stormwater management, which include the following:

• DOT guidelines (40 of 42 DOTs, 95%)
• State regulatory and environmental agency guidelines (34 of 42 DOTs, 81%)
• Federal guidelines or general construction practices (21 of 42 DOTs, 50%)
• Scientific research (11 of 42 DOTs, 26%)
• Rules of thumb and current practices (10 of 42 DOTs, 24%)
• EPA guidelines (2 of 42 DOTs, 5%)

The process for regulatory and internal audits of the implementation of construction components of stormwater programs varies among state DOTs. Based on survey examples, the frequency of internal audits conducted includes annually (17 of 40 DOTs, 43%), as needed (17 of 40 DOTs, 43%), and when revisions occur to federal and state permit requirements (5 of 40 DOTs, 13%). The frequency of regulatory audits includes as needed (20 of 40 DOTs, 50%), every 4 to 5 years (8 of 40 DOTs, 20%), and annually (6 of 40 DOTs, 15%). In addition, in the case examples, the DOTs have various levels or tiers of audits, which are required under some permits. In each case example, the DOT also mentioned that regulatory audits by the EPA or FHWA are infrequent.

The gaps in knowledge and practice identified in this synthesis may serve as indicators for potential future research. To improve state DOT practices, tools, and approaches for managing compliance with state and federal construction stormwater permit requirements, future research is suggested for the following areas:

• Develop guidelines for construction stormwater management programs, including alternative contracting methods (e.g., design-build, construction manager, general contractor), uniformity in training and certifications, phasing approaches to minimize ground disturbances during construction, monitoring discharges during construction, and technologies, programs, and applications used for construction stormwater management.
• Develop consistency of BMP and construction stormwater management terminology and applications by creating guidelines for stormwater management and BMP programs during and after construction.
• Conduct a synthesis study on MS4 programs and the methods used by DOTs to comply with permit requirements.
• Conduct a synthesis study on state DOT implementation of post-construction BMPs.