S A AN NTONIO LID G M UIDANCE ANUAL BY: CENTER FOR RESEARCH IN WATER RESOURCES & LADY BIRD JOHNSON WILDFLOWER CENTER UNIVERSITY OF TEXAS AT AUSTIN AUGUST 2011 Manual prepared, and financed by grants through, the Texas Commission on Environmental Quality and the United States Environmental Protection Agency as part of the UT LID Workshops project. Table of Contents 1  Introduction ................................................................................................................ 1  1.1  Background & Definition....................................................................................... 1  1.2  Manual Purpose and Structure ............................................................................. 3  1.3  LID Strategies ........................................................................................................ 4  1.3.1  Regional, Neighborhood and Site Scale ................................................. 4  1.4  Benefits Provided by LID ...................................................................................... 5  1.4.1  Environmental Benefits ......................................................................... 5  1.4.2  Land Value and Quality of Life Benefits ................................................ 7  1.5  Common terms ...................................................................................................... 9  2  Local Factors Affecting LID Selection in the San Antonio Area ............................... 11  2.1  Existing City Code ................................................................................................ 11  2.2  State Requirements ............................................................................................. 12  2.3  Geology and Physiographic Regions ................................................................... 13  2.3.1  San Antonio Eco-Regions .................................................................... 14  2.4  Brownfield Sites ................................................................................................... 18  2.5  Pollutant Removal ............................................................................................... 19  3  Non-Structural LID Practices ................................................................................... 20  3.1  Sustainable Site Design ....................................................................................... 21  3.1.1  Preservation of Natural Features ......................................................... 21  3.1.2  Conservation Design ............................................................................ 25  3.2  Reduction of Impervious Cover .......................................................................... 29  3.2.1  Streets, Sidewalks, Driveways and Parking Lots ................................. 29  3.3  Disconnection ...................................................................................................... 33  3.3.1  Impervious Cover Disconnection......................................................... 33  i Table of Contents 1  Introduction ................................................................................................................ 1  1.1  Background & Definition....................................................................................... 1  1.2  Manual Purpose and Structure ............................................................................. 3  1.3  LID Strategies ........................................................................................................ 4  1.3.1  Regional, Neighborhood and Site Scale ................................................. 4  1.4  Benefits Provided by LID ...................................................................................... 5  1.4.1  Environmental Benefits ......................................................................... 5  1.4.2  Land Value and Quality of Life Benefits ................................................ 7  1.5  Common terms ...................................................................................................... 9  2  Local Factors Affecting LID Selection in the San Antonio Area ............................... 11  2.1  Existing City Code ................................................................................................ 11  2.2  State Requirements ............................................................................................. 12  2.3  Geology and Physiographic Regions ................................................................... 13  2.3.1  San Antonio Eco-Regions .................................................................... 14  2.4  Brownfield Sites ................................................................................................... 18  2.5  Pollutant Removal ............................................................................................... 19  3  Non-Structural LID Practices ................................................................................... 20  3.1  Sustainable Site Design ....................................................................................... 21  3.1.1  Preservation of Natural Features ......................................................... 21  3.1.2  Conservation Design ............................................................................ 25  3.2  Reduction of Impervious Cover .......................................................................... 29  3.2.1  Streets, Sidewalks, Driveways and Parking Lots ................................. 29  3.3  Disconnection ...................................................................................................... 33  3.3.1  Impervious Cover Disconnection......................................................... 33  i 3.3.2  Downspout Disconnection ................................................................... 34  4  Descriptions and Selection Criteria for Structural LID Practices ............................ 37  4.1  Rain Gardens & Bioretention .............................................................................. 39  4.1.1  Description ........................................................................................... 40  4.2  Vegetated swales .................................................................................................. 44  4.3  Vegetated Filter Strips ......................................................................................... 47  4.4  Porous Pavement ................................................................................................. 50  4.5  Rainwater Harvesting.......................................................................................... 54  4.6  Treatment Trains ................................................................................................. 57  4.7  Additional LID BMPs .......................................................................................... 58  4.7.1  Green Roofs .......................................................................................... 58  4.7.2  Proprietary Systems ............................................................................. 59  4.7.3  Constructed Wetland & Wet Ponds ..................................................... 60  5  Design Guidelines for Structural LID Practices ....................................................... 62  5.1  Rain Gardens & Bioretention .............................................................................. 63  5.1.1  Rain Gardens ........................................................................................ 63  5.1.2  Bioretention.......................................................................................... 66  5.1.3  Plant Selection & Considerations......................................................... 75  5.2  Vegetated Swales ................................................................................................. 79  5.2.1  Plant Selection ...................................................................................... 84  5.3  Vegetated Filter Strips ......................................................................................... 85  5.3.1  Plant Selection ...................................................................................... 89  5.4  Porous Pavement ................................................................................................. 90  6  References ................................................................................................................. 92  Appendix A: Definitions & Acronyms ............................................................................... 94  ii Appendix B: Plants ............................................................................................................ 96  iii List of Figures All figures courtesy of Center for Research in Water Resources and Lady Bird Johnson Wildflower Center unless otherwise noted. Figure 2-1: Edwards Aquifer Zones and Physiographic Regional Typology (Adapted from CalPoly Studio 606). .......................................................................................................... 13  Figure 2-2: Typology of Edwards Plateau and Blackland Prairie Regions (Adapted from and courtesy of CalPoly Studio 606). ................................................................................ 15  Figure 3-1: Conventional design (left) and conservation design (right) (courtesy Town of Pine Plains, NY). ................................................................................................................ 26  Figure 3-2: Disconnection at Portland State University, Oregon, where vegetated areas are distributed throughout the impervious courtyard area. ............................................. 33  Figure 3-3: Downspouts directed to permeable pavement on driveway (courtesy of Montgomery County, MD) ................................................................................................ 34  Figure 3-4: Downspout directed to a rain garden after passing over a stone splash pad. ........................................................................................................................................... 35  Figure 3-5: Treatment train approach: disconnected downspout runoff enters a series of vegetated controls. ............................................................................................................ 36  Figure 4-1: A diagram of the basic rain garden / bioretention system components, including optional components. ....................................................................................... 39  Figure 4-2: Picture of a rain garden under construction (courtesy of URS Corporation) ........................................................................................................................................... 40  Figure 4-3: Picture of a bioretention facility (courtesy of David Dods) ........................... 41  Figure 4-4: Schematic of a bioretention/rain garden BMP with no underdrain; treated stormwater infiltrates into surrounding soils. .................................................................. 42  Figure 4-5: Picture of a typical swale (courtesy of David Dods) ...................................... 44  Figure 4-6: Swale in parking lot area showing the use of short grasses, low slopes, curb cuts from parking area and some infiltration. .................................................................. 45  Figure 4-7: Filter strip along side of highway ................................................................... 47  Figure 4-8: Picture of permeable pavers in portion of parking lot in San Antonio (courtesy of David Dods) ................................................................................................... 50  iv Figure 4-9: Porous pavement sidewalk installation with filter fabric placed beneath the gravel and stone layers (courtesy of URS Corporation). .................................................. 51  Figure 4-10: Picture of a rainwater collection system (courtesy of David Dods)............. 54  Figure 5-1: Historical rainfall pattern in the Central Texas region and fraction of annual runoff volume treated as determined by rainfall depth treatment capacity (e.g., water quality volume). ................................................................................................................. 62  Figure 5-2: An example of a rain garden design following City of Austin specifications as described in Section 1.6.7 of the Environmental Criteria Manual (2009). ...................... 64  Figure 5-3: Rain garden schematic with no underdrain. ................................................. 65  Figure 5-4: Bioretention along streets with a combination of infiltration and underdrain. ........................................................................................................................................... 66  Figure 5-5: Schematic diagram of a bioretention system. ................................................ 67  Figure 5-6: Curb cut options: smooth cut, hard cut and flush curb ................................. 68  Figure 5-7: Curb cuts with optional sediment / trash screens ......................................... 69  Figure 5-8: Detail of cleanout location .............................................................................. 71  Figure 5-9: Illustration of optional outlet design ............................................................. 72  Figure 5-10: Diagram of Grassy Swale with Check Dam (MDE, 2000). .......................... 80  Figure 5-11: Enhanced swale diagram with underdrain system in parking lot. ............... 82  Figure 5-12: Engineered VFS in context. .......................................................................... 86  Figure 5-13: Example of filter strip along roadway in plan view. ..................................... 87  Figure 5-14: Example configuration of filter strip adjacent to parking lot in plan view. . 87  Figure 5-15: Basic components of a porous pavement system. ........................................ 90  v List of Tables Table 1: Summary of LID Selection Criteria ..................................................................... 37  vi