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To promote a more livable Downtown, projects must address sustainability at multiple levels. The design of the street, buildings, and landscape must work in tandem to achieve the most effective results. This chapter provides an overview of the intent of the Downtown Design Guide with respect to sustainability. A. NEIGHBORHOOD DESIGN 1. Support walkability through sensitive design of the site, building and streetscape. 2. Since all of Downtown San Antonio is within walking distance of transit stops, design all projects as Transit-Oriented Developments (TODs) that encourage residents, tenants and visitors to use transit. 3. Orient projects to provide convenient access to the nearest transit options (bus, streetcar, trolley, bicycle), wherever possible. 4. New infill construction buildings should be certified as Green Buildings by LEED or other ratings systems. B. STREET AND ALLEY DESIGN 1. Design sidewalks, including street trees, parkways, tree wells and paving, to collect storm water runoff, thereby contributing to sustainable Green Streets and enhancing the value of the project. 2. Design alleys, placitas and paseos to collect storm water where feasible. C. SITE AND LANDSCAPE DESIGN 1. Incorporate on-site landscape elements that reduce energy use and enhance livability. 2. Consider providing a green roof to reduce solar gain (which contributes to the urban heat island effect) and to reduce the quantity of water entering the storm drains system as seen in Figure 11.2. 3. All new development should support a coordinated and comprehensive storm water management system strategy through the utilization of Low Impact Development (LID).
D. BUILDING DESIGN 1.
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3. Wherever possible, existing structures should be re-used and integrated into new projects to retain the authentic architectural fabric of Downtown. 4. Integrate LID to include: roof water collection and reuse, cisterns, green roofs, living machines, inlet devices, deep mulching, structural soils, sand and organic and peat filters, biodetention and bioretention, meadow and pocket and gravel and shallow marsh wetlands, subsurface detention, filter-vertical recovery structures, rain gardens, biofiltration, depressed parking lot islands, permeable concrete, open joint terrace and walk system, and green canopies. 5. Figures 11.3 and 11.4 illustrate how to integrate green utilities like soil, trees and water into our urban areas substantially improves their design sustainability and helps alleviate some of our most pressing ecological challenges - including air and water quality, rising temperatures, and flooding and erosion from rainfall events.
E. MEASURES IN ULTRA URBAN AREAS LID projects are engineered systems that manage storm water as close to the ground as possible, replicates the pre-development hydrology of the site and maintains pre-development flow conditions in a watershed. There are many LID techniques that can be selected for use, and studies have shown that utilizing these techniques actually can result in savings over the life of a project. Green Walls and Roofs Rain Gardens 1. A green roof cover is a veneer of vegetation that is grown on and covers an otherwise conventional flat or pitched roof (30° slope), endowing the roof with hydrologic characteristics that more closely match surface vegetation than a typical roof. The overall thickness of the veneer may range from two (2) to six (6) inches and may contain multiple layers, consisting of waterproofing, synthetic insulation, non-soil engineered growth media, fabrics, and synthetic components. Green roof covers can be optimized to achieve water quantity and water quality benefits. Through the appropriate selection of materials, even thin vegetated covers can provide significant rainfall retention and detention functions. Vegetated roof covers that are 10 inches, or deeper, are referred to as 'intensive' vegetated roof covers. Intensive assemblies can also provide substantial environmental benefits, but are intended primarily to achieve aesthetic and architectural principles.
Rain Capture and Reuse 2. Storm water can be routed into cisterns above or below ground to detain the water onsite. The storm water can then be used to irrigate landscaping or routed into other treatment features for water quality polishing before released offsite. Below grounds cisterns can be covered with parking lots, reducing the footprint of the site.
Bioretention 3. Tree box filters are very small bioretention areas installed beneath trees that can be very effective at controlling runoff, especially when distributed throughout the site. Runoff is directed to the tree box, where it is cleaned by vegetation and soil before entering a catch basin. The runoff collected in the tree-boxes effectively irrigates the trees. The system consists of a container filled with a soil mixture, a mulch layer, under-drain system and a tree or shrub. Storm water runoff drains directly from impervious surfaces through a filter media. Treated water flows out of the system through an underdrain connected to a storm drainpipe and inlet or into the surrounding soil. Tree box filters can also be used to control runoff volumes and flows by adding storage volume beneath the filter box with an outlet control device. Typical landscape plants (shrubs, ornamental grasses, trees and flowers) are used as an integral part of the bioretention and filtration system. They can fit into any landscape scheme, increasing the quality of life in urban areas by adding beauty, habitat value, and reducing urban heat island effects.
Permeable Pavement 4. Porous pavement is a permeable pavement surface with a stone reservoir underneath. The reservoir temporarily stores surface runoff before infiltrating it into the subsoil. Runoff is thereby infiltrated directly into the soil and receives some water quality treatment. Porous pavement often appears the same as traditional asphalt or concrete but is manufactured without "fine" materials, and instead incorporates void spaces that allow for infiltration.
Planters 5. Planters can be designed in a variety of formats to serve as both as a storm water control as well as an amenity with trees and public interest.
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