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50 TABLE 2-2 Alternative mitigation and stormwater management flexibility practices in use at state DOTs Alternative Mitigation and Number of States Number of States Not Stormwater Management Using Using Flexibility Onsite mitigation 40 10 Offsite (within sub-basin) 26 24 Offsite (within larger 17 33 watershed) Alternative mitigation 12 38 Stormwater banking 7 43 Cross-category trading 3 47 Valid monitoring methods; seeks to ensure the integration of transportation planning and Demonstration of the costs and benefits of alternative, project delivery into statewide watershed recovery efforts offsite, or watershed-based stormwater mitigation; and the direction of mitigation dollars toward high-priority Best methods for improving stream ecology through watershed recovery efforts in a basin. water quality BMPs--alternatives to regulating runoff Of the topics pertaining to a watershed approach, DOTs in urban areas; were interested mostly in a runoff characterization question: Vegetation establishment; what was the contribution of highway runoff to watershed BMP benefits and constraints in highly urbanized loadings. This was a high-priority research area for more than corridors; 50% of all DOTs, and a mid-level priority for another 25%. Selection of treatment BMPs and documentation of More than 80% of the DOTs also had a medium- or high-level process; interest in demonstrating the costs and benefits of alternative, Detention basin design optimization; offsite, and watershed-based stormwater mitigation. Methods Effectiveness of combination of sedimentation, filtra- for improving watershed stream ecology through alternative tion, and chemical addition for stormwater BMP con- and perhaps offsite water quality BMPs were of interest to struction and retrofit projects; 72% of the DOTs. Also, 70% of the DOTs wanted to see Guidance for seed mixes and effective establishment methodologies developed to determine where flow control of and maintenance of erosion control vegetation for short- runoff volumes and high-flow durations are appropriate to term first growth and long-term establishment; prevent stream bank erosion in ultra-urban areas. Infiltration guidance to prevent groundwater contami- Characterizing sites for offsite water quality treatment on nation; a watershed basis is relatively uncommon. A minority of Design and maintenance of BMPs to reduce conflicts states indicated that they enjoyed some flexibility with miti- with endangered and threatened species; gating for stormwater management off site where it would Soil evaluation processes for slope vegetation; produce greater environmental benefit for the watershed. LID modeling and design so that end-of-pipe control Although identifying priority investments has the potential systems can be sized accurately; and to improve environmental outcomes on a watershed basis, the Compliance with numeric water-quality standards. DOTs had a lower interest in how they could improve ecolog- ical productivity elsewhere in the watershed, especially with- Ranked lower in overall priority but still of medium impor- out discussion of how they might receive credit (such as mod- tance to many respondents were "methodologies to deter- ified expectations for onsite BMPs) in exchange for such work. mine where flow control of runoff volumes and high-flow Of watershed-related research questions, the DOTs ranked rel- durations are appropriate to prevent stream bank erosion in atively low the ability of watershed or regionally-based ultra-urban areas." enhancements of wet weather storage capacity to improve baseline (high and low flow) hydrology and ecological pro- 2.2. WATERSHED APPROACHES ductivity downstream and water quality problems due to urbanization and heavy metal concentration in relation to or A watershed approach offers the opportunity to plan com- projected from Total Connected Impervious Area in the prehensively and offer solutions that promote sustainable watershed. Still, two-thirds ranked the former as a mid- or and economically productive watersheds. The approach often high-level research priority and more than 60% considered