Tools to Improve Water Quality

Transcription

1 Tools to Improve Water Quality SARA Water Quality Modeling Tool Development Client: San Antonio River Authority (SARA) Firm: Lockwood, Andrews & Newnam, Inc. Category A: Studies, Research and Consulting Engineering Services Large Firm

2 Tools to Improve Water Quality Project Overview In 2009, the San Antonio River Authority (SARA) completed a flood insurance study for the Bexar County watersheds in the San Antonio River Basin. The study, which was carried out in collaboration with the Federal Emergency Management Agency (FEMA), the City of San Antonio, Bexar County, and other stakeholders, produced a set of up-to-date hydrologic and hydraulic models that allowed SARA to conduct holistic watershed master planning on major watersheds including the Salado Creek, Leon Creek, and Upper San Antonio River (USAR) watersheds. As part of the holistic watershed master planning efforts, dynamic water quality models were developed and calibrated to assess water quality damage centers for potential impairments. These damage center locations were identified by comparing model output constituent concentrations against a set of screening levels developed by the Texas Surface Water Quality Standards (TSWQS) and Texas Clean River Program (CRP). Within the basin s urban areas, several water bodies have been listed by the U.S. Environmental Protection Agency (EPA) and the Texas Commission on Environmental Quality (TCEQ) as impaired due to bacteria, dissolved oxygen, and other water quality constituents or pollutants not meeting TSWQS or CRP screening levels. While stormwater runoff was identified as a potential source of impairment, the listing of impaired water bodies was mostly based on limited monitoring data sampled at selected time intervals (mostly quarterly) and limited stations. Substantial temporal and spatial gaps were identified in the data throughout the watershed master planning and impaired water body listing processes. The selection and implementation of Best Management Practices (BMPs) and low-impact development (LID) strategies not only help address existing water quality impairments and support regulatory compliance, but also guide future watershed planning. In recent years, selection and implementation of Best Management Practices (BMPs) and low-impact development (LID) strategies to address urban runoff pollution have SARA completed a flood insurance study for the Bexar County watersheds in the San Antonio River Basin, producing a set of up-to-date hydrologic and hydraulic models that allowed SARA to conduct holistic watershed master planning on major watersheds. Photo Source: San Antonio River Authority (SARA) 2

3 become important components of holistic watershed master planning and stormwater management. These BMP and LID strategies can not only help address existing water quality impairments and support regulatory compliance, but also guide future watershed planning especially when substantial population growth and urbanization is projected. However, the efforts have generally been limited to qualitative planning in the past, mostly due to the lack of suitable tools to conduct quantitative assessment. As a result, the effectiveness of the BMP/LID could only rely on follow-up long-term monitoring to verify, and in general, there is a lack of planning effort prior to implementing BMP or LID strategies. To help fill data gaps and support stormwater quality management and compliance with increasing water quality regulations, a project team led by professional engineers with SARA and Lockwood, Andrews & Newnam, Inc. (LAN), and software developers with AQUA TERRA Consultants created a number of water quality modeling tools to allow quantitative water quality master planning and BMP/LID prioritization. The main tools and enhancements developed by the project team include: SARA Water Quality Modeling Standards to ensure consistence in the development and calibration of dynamic water quality models; Developed and calibrated water quality models to identify impaired water bodies (locations, timing, and constituents); SARA Load Reduction Tool to determine percent load reductions needed to achieve selected screening levels for each of the modeled constituents on a sub-basin basis; SARA BMP Tool to determine the optimal (minimal cost) combination of the types and numbers of BMP and LID units needed to achieve the required load reductions. Photo Source: San Antonio River Authority (SARA) These BMP and LID strategies can not only help address existing water quality impairments and support regulatory compliance, but also guide future watershed planning especially when substantial population growth and urbanization is projected. 3

4 Innovative Application of New or Existing Techniques The SARA models and tools developed are on the cutting edge of the water quality modeling profession nationwide. Dynamic watershed and instream water quality models were developed for Salado Creek, Leon Creek, and USAR watersheds using the Hydrological Simulation Program-FORTRAN (HSPF) program, which is maintained under the sponsorship of the EPA. The HSPF program is capable of simulating watershed and instream hydrologic and water quality processes dynamically through both dry and wet periods. The program has been utilized by water quality modeling professionals for several decades and is one of the most well-documented and verified programs. As there were various ongoing water quality SARA Load Reduction Tool modeling efforts in the San Antonio River Basin, in December 2013, SARA and the project team developed a water quality modeling standards document to ensure the quality and consistency of the developed water quality models. The document addresses all aspects of the water quality modeling process from model setup to input data development, to model parameterization, and ultimately to model calibration, validation, application, and overall model performance assessment. The document, one of the first of its kind, was developed by the project team using available information nationwide. Next, to support the water quality modeling efforts and allow quantitative water quality master planning, the project team developed and tested a set of state-of-the-art tools to work with HSPF. These included: The Timeseries Utility Tool was developed to allow for viewing, processing, and exporting HSPF output files such as those that contain large runoff and pollutant load timeseries. This tool also includes some re-engineering of the reading of the HSPF output timeseries to better handle large files of many thousands of individual timeseries. The tool was developed, tested, and released to the public through the EPA s BASINS user community on October 24, Since its public release, the project team has received positive user feedback. The SARA Load Reduction Tool was developed to automatically determine the required load reductions for all reaches within a watershed on a constituent by constituent and sub-basin by sub-basin basis to meet user-specified screening levels. The tool processes HSPF results and calculates flow-weighted average concentrations for comparison against user-specified screening levels. The difference is used to develop SARA Timeseries Utility Tool The Timeseries Utility Tool was developed to allow for viewing, processing, and exporting HSPF output files such as those that contain large runoff and pollutant load timeseries. needed load reductions using the BMP Module in HSPF, and the tool continues the iterations until all calculated concentrations are meeting the screening levels within user-specified tolerances. Given that upstream load would impact downstream concentrations, the tool conducts iterative 4

5 target load reductions. The tool takes runoff flow and pollutant load timeseries from the HSPF models, conducts physical routing of the timeseries through the BMP/LID units including stormwater treatment and bypass processes, and optimizes the BMP/LID based on minimizing the annualized life-span costs. A substantial BMP Tool database was developed to support the execution of the BMP Tool. The database was populated using available local, regional, and nationwide SARA Load Reduction Tool The SARA Load Reduction Tool was developed to automatically determine the required load reductions for all reaches within a watershed on a constituent by constituent and sub-basin by sub-basin basis to meet user-specified screening levels. data that include BMP dimensions, costs, and performances. The developed SARA tools were thoroughly calculations from upstream to downstream until all sub-basins are meeting specified screening levels for all constituents. This tool substantially reduces labor time and eliminates human errors when compared to manually conducting the same iterative load reduction calculations and HSPF simulations. The tool was developed, tested, and released to the public through the EPA s BASINS user community on May 9, The SARA Enhanced BMP Tool was developed to determine the optimal BMP/ LID combinations to achieve constituent load reduction. The tool was designed to help select the types and number of BMP and LID units to achieve the needed load reductions identified by either the Load Reduction Tool or the user. The tool combines robust land surface representation from HSPF with the BMP processing and optimization components of EPA s SUSTAIN (System for Urban Stormwater Treatment and Analysis Integration) program (SUSTAINOPT), which optimizes the number and type of BMP/ LID units within a sub-basin by minimizing overall costs while achieving the required tested and then applied to Salado Creek, Leon Creek, and USAR watersheds. The concepts and software technology behind the tools are innovative and will benefit the stormwater quality management profession as well as regulatory agencies. SARA Enhanced BMP Tool The SARA Enhanced BMP Tool was developed to determine the optimal BMP/ LID combinations to achieve constituent load reduction. 5

6 Future Value to the Engineering Profession While quantitative watershed master planning in the hydrologic and hydraulic field has been a standard practice for many decades, rural and urban runoff water quality management using BMP and LID strategies have generally been limited to qualitative planning. In many cases, BMP and LID were implemented and then found ineffective through follow-up monitoring. In addition, inappropriate types and numbers of BMP and LID units might be placed at locations that provide little or no benefit to instream water quality. The powerful and advanced water quality modeling tools developed by the project team provides water authorities and stormwater professionals around the country a new and more effective way to address water quality issues in their communities. Through the SARA tools for determining optimal BMP/ LID implementation, users can now minimize the design and installation of unsuitable and costly BMP/LID. In addition, regulatory and planning agencies can now use the tools to determine sustainable strategies for managing water quality and urbanization. The tools can also provide cost information for budgeting BMP/LID implementation and maintenance, as well as help develop the fee structure for drainage utility and stormwater management. Another value of using the SARA tools is to help determine BMP and LID strategies needed to delist a water body from water quality impairments, or to determine if BMP and LID strategies alone could achieve the required load reduction. Essentially, the value of applying these tools is unlimited as users would be able to simulate as many what-if scenarios as they like. The project team s efforts are increasingly gaining national attention. The developed models were calibrated and validated to available water quality data and peer reviewed by national experts to ensure conformance with strict water quality modeling standards. The modeling efforts and results have been published at professional conferences and magazines and were wellreceived by technical and policy audiences. Multiple water agencies and regulatory authorities have expressed interest in using these tools. SARA and LAN are currently communicating with the EPA to incorporate these tools to allow more widespread application. Photo Source: San Antonio River Authority (SARA) Through the SARA tools for determining optimal BMP/LID implementation, users can now minimize the design and installation of unsuitable and costly BMPs/LID. 6

7 Furthermore, the results from these models could potentially help the EPA and state agencies determine BMP/LID strategies needed in order to delist many impaired water bodies around the country or determine if delisting is possible or not using BMP/LID strategies alone. Many water bodies in Texas have been listed as impaired due to bacteria concentrations exceeding TSWQS standards for contact recreation. With bacteria concentrations being typically very high in stormwater runoffs, many communities have struggled to meet these standards. Through the application of these tools, SARA and the project team have provided a scientific basis to determine suitable bacteria criteria, which could be a potential game-changer for the profession. Social, Economic And Sustainable Design Considerations To date, many BMP/LID implementations are simply best management or to the extent practicable. With the costs of BMP/ LID construction, operation and maintenance, and monitoring becoming more and more substantial, implementing water quality BMP/ LID in a watershed without prior quantitative planning can result in considerable waste of public funding with ineffective or unnecessary water quality measures. Using these innovative SARA models and tools, water quality agencies and stormwater professionals can now determine the optimal combinations of BMPs/LID to accomplish their goals and save substantial stormwater infrastructure and management costs. components), chlorophyll a, bacteria (E. coli), and representative metals (lead and zinc). By using these SARA models and tools, water authorities and stormwater professionals can implement the optimal BMP/LID measures determined using the real BMP performance data to reduce each selected constituent effectively. The tools were also developed with substantial flexibility to allow users to adjust the LID/BMP data to suit their local situations when executing the tools, or to revise the data when future BMPs or more data become available. In the long run, applying these models and tools will enable water authorities and stormwater professionals to effectively manage stormwater runoffs as close as possible to the source, thereby creating more sustainable watersheds, improving public health and quality of life, enhancing natural habitats, and supporting public recreation, as well as boosting the local economy. More importantly, SARA and the project team s efforts will have a significant impact on managing water quality, an increasing concern in the United States and around the world. A wide range of constituents were simulated in these models, including temperature, carbonaceous biochemical oxygen demand, dissolved oxygen, total suspended solids, nutrients (nitrogen and phosphorus SARA and the project team s efforts will have a significant impact on managing water quality, an increasing concern in the United States and around the world. Photo Source: San Antonio River Authority (SARA) 7

8 Complexity With no precedent to work from, the project team developed a workflow and created these water quality models and tools from scratch. This required navigating through several complex issues. Collecting, reviewing, and evaluating the massive quantity of available data needed to develop and calibrate dynamic water quality models presented the first major challenge. Data from local, state, and federal entities were collected, including SARA, City of San Antonio, San Antonio Water System, Edwards Aquifer Authority, Bexar County, City of Austin, TCEQ, Texas Water Development Board, U.S. Geological Survey, U.S. Army Corps of Engineers, Natural Resources Conservation Services, National Weather Service, as well as educational institutions and private consulting firms. With substantial portions of the watersheds located on top of the Edwards Aquifer, recharge flows and spring flows were included in the models, which added another layer of complexity to the development and validation of the models. drainage areas served by each BMP, BMP types, BMP dimensions, BMP performance and corresponding constituent decay coefficients, outlet configurations, and capital and operation/maintenance costs including life-span engineering economic conversions. The database greatly facilitated the data input process for the BMP Tool since most of the data required by SUSTAINOPT, the core engine of the SARA BMP Tool, could be automatically retrieved from the database. The user only needed to specify the BMPs to be used when running the tool. Additionally, the team designed the database with the flexibility for users to include additional BMP types or modify data to suit their particular purposes or local situation. Developing the BMP Tool to streamline the BMP optimization process and post- HSPF validation runs was another complex challenge. Initially, the project team used the scatter search approach to optimize the BMPs. However, the project team found that approach did not work well, so a generic algorithm method was adopted instead to optimize the BMPs. In addition, the time needed to complete one BMP Tool run for one sub-basin using this method initially took about five days using the entire fouryear continuous simulation period at each optimization iteration. To substantially improve tool runtime, the project team adopted a concept called the Critical Exceedance Volume (CEV) that effectively reduced the average BMP Tool runtime by 85%. The team then adopted an approach to select only top-performing BMPs and organized them in upstream-downstream series, which effectively reduced the average runtime by approximately 95% or about 6.5 hours per run. The project team also developed an extensive BMP Tool Database using data from various national, regional, and local sources including the American Society of Civil Engineers BMP database. The SARA BMP Tool Database included comprehensive data such as The project team adopted Critical Exceedance Volume (CEV) approach that reduced the average BMP Tool runtime. 8

9 Exceeding Client/Owner Needs Through these models and tools, SARA and its stakeholders are able to conduct holistic watershed master planning, evaluate the effects of various BMP and LID strategies, and cost-effectively implement sustainable water quality enhancements in the San Antonio River Basin. In the spring of 2015, SARA asked the project team to perform BMP Tool scenario runs and requested an estimate of the number of simulations that could be conducted for a given budget. At the time, based on the average runtime per sub-basin, the project team estimated a total of 162 BMP Tool runs. As the team started conducting these tool runs, they investigated rigorously into where substantial time-savings could be achieved. The team developed an additional batch tool that would allow BMP Tool runs in the background, which also minimized computer idle time and eliminated human errors. As a result, the project team was able to conduct more than 900 BMP Tool scenario runs under the same budget and schedule. The results of these massive runs significantly exceeded client s expectation and provided SARA with substantial data sets for evaluating BMP effectiveness on delisting impaired water bodies. In addition, the project team had developed a BMP Reporter tool to help post process the massive output produced by SUSTAINOPT. This tool was not envisioned in the original scope with the client, but the project team saw the benefit of having such a tool. This tool includes many features such as dragging and dropping SUSTAINOPT output folders into this tool to automatically compile the results into attribute tables ready for GIS processing. This effort is another example of exceeding the client needs. SARA led the project team to develop models and tools that would help solve the water quality problems in its watersheds. By taking ownership of the project and forming a collaborative partnership with SARA, the team developed unique solutions that would not only benefit San Antonio s watersheds but also watersheds throughout the country. Through the development of these tools, the project team also has helped SARA further enhance its reputation as a leader in watershed solutions. Submitted by: Yu-Chun Su, Ph.D., P.E., CFM, CPESC, CPSWQ YCSu@lan-inc.com