||Tetra Tech, Inc., Fairfax, VA.; Environmental Protection Agency, Edison, NJ. Urban Watershed Research Facility.; National Risk Management Research Lab., Cincinnati, OH.
This case study for the Albuquerque, New Mexico area was conducted under contract with the U.S. Environmental Protection Agency (EPA) Office of Research and Development using the System for Urban Stormwater Treatment and Integration Analysis (SUSTAIN). The effort focuses on investigating both site- and regional-scale stormwater management questions ahead of a pending watershed-based municipal separate storm sewer system (MS4) permit. The SUSTAIN modeling system integrates watershed modeling capabilities, best management practice (BMP) process simulation, and BMP cost representation within the context of a cost-benefit optimization framework (USEPA, 2009). The system can be used to evaluate complex decisions about green infrastructure selection and placement, performance, and costs for meeting flow or water quality targets or both. With the large degree of variability in physical, hydrological, and chemical characteristic in a watershed, watershed-scale management for the nonpoint source component of MS4 permits quickly grows in complexity. Because different land uses had different pollutant levels, and because there were differences in BMP cost assumptions, there were differences in cost-effectiveness between management strategies that yielded comparable water quality outcomes. The objective of watershed management within an optimization framework like SUSTAIN is to identify strategies that meet water quality goals while minimizing cost. Tetra Tech has developed two other SUSTAIN case studies for EPA in Kansas City, Missouri and Louisville, Kentucky, as part of this development phase (USEPA, 2012). These studies investigated the use of green or gray infrastructure practices to mitigate combined sewer overflows in temperate climate areas. In contrast, this Albuquerque case study focuses on water quality performance of different management practices for various storm sizes in an arid climate. The proposed approach documents the various phases of the SUSTAIN application process, including establishing baseline hydrology and water quality loads, identifying the critical condition for management, formulating management objectives on the basis of local design standards, and testing the sensitivity of optimization results to different formulations of the management objectives. The study estimates the potential range of benefits and impacts in light of existing Escherichia coli (E. coli) total maximum daily load (TMDL) targets. The results of this study provide quantitative technical guidance to support the pending watershed-based MS4 permit.