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URBAN REDEV 21182 Competition Submittal


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Electronic submittal from team of Llewelyn-Davies Sahni, Edminster Hinshaw Russ & Associates, Davidson Landscape Architecture and T.O.D. Houston

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URBAN REDEV 21182 Competition Submittal

  1. 1. Houston Land/Water Sustainability Forum Low Impact Development Design Competition
  2. 2. Design Overview <ul><li>The Bastrop Promenade is the culmination of a team effort based on strong urban design principles, &quot;out of the box&quot; hydrologic modeling methods, and a low-impact design mindset. </li></ul><ul><li>The designated site lies in the heart of TIRZ 15 , with a proposed stadium at its north end and a proposed park at its south end. The site was programmed based on the following criteria: </li></ul><ul><ul><li>Polk Street has the highest traffic volume and through traffic </li></ul></ul><ul><ul><li>Other cross-streets have slower local traffic and on street parking </li></ul></ul><ul><ul><li>High pedestrian access from the north end of the promenade (from the proposed stadium and Metro Light Rail station) </li></ul></ul><ul><ul><li>Pedestrian access at south end through the park, at the cross streets, as well as mid-block through the proposed development </li></ul></ul><ul><ul><li>Limit and protect pedestrian crossings of the cross streets </li></ul></ul><ul><ul><li>Maintain a clear view corridor down the length of the promenade </li></ul></ul><ul><ul><li>Keep certain existing buildings for reuse or redevelopment </li></ul></ul><ul><ul><li>The promenade will be a 24/7 destination </li></ul></ul><ul><ul><li>Use of bioretention cells, swales, rain gardens, and subsurface stormwater harvesting tanks </li></ul></ul><ul><li>The project site was zoned with proposed mixed-use development on either side of the promenade. It maintains a more tranquil and serene setting on the south end moving towards more high energy activity at the north end. The existing buildings (blocks 305, 465, 464, 463, & 201) were redeveloped into an international market with views and access to the promenade. Interior service yards serve both existing buildings as well as proposed buildings, and have access from the cross streets. The mixed-use development uses higher first floor heights for retail/restaurants/cafe's, with residential on higher floors. The development is divided into two sections – the south end for office space and the north end for entertainment. </li></ul>An existing building on Block 222, currently used as artist lofts, is adjacent to a proposed “Arts Plaza” that can be used for public gatherings and showcasing art. Each block contains accessible and non-accessible landscaped zones. Each accessible landscaped zone contains a potential pad that can be used for display; there are a total of 16 display pads for Houston's Sister Cities. With the combined use of layout, porous materials, and bioretention cells (in the event of a 100 Year Flood) the walkways that run parallel to the block fronts as well as the composite wood decked “nodes” would remain usable. The only ponding would occur along the middle of the promenade. The stormwater run-off from the promenade and cross streets makes its way through rain gardens and bioretention cells, filtering it and slowing it down, into subsurface harvesting tanks strategically placed all along the promenade. The storage tanks hold excess water, making it usable for irrigation, as well as other grey water uses for the development on either side of the promenade. The LID makes it possible to allow for 100% development to occur on each of the blocks adjacent to the promenade without the need of detention ponds or basins. The need for “green roofs” or “green walls” is not a requirement for the system to work, but of course they would be a welcome addition and would benefit an environmentally-conscious outlook.
  3. 3. Design Overview
  4. 4. Landscape & Irrigation Strategies The landscape concept is to bring natural areas back into the urban environment. The rain gardens systems designed are to mimic a natural stream system both visually and functionally. The landscape plantings have been selected based on their natural requirements to the local climate and the availability from growers. All landscape areas, other than the turf areas, do not require permanent irrigation systems. Within the rain garden areas there three levels of water. Simply put, there are the lower areas which receive the typical storm event and the selected species must withstand standing water. There is the middle area which is somewhat drier. The species in this area will be submerged for a short amount of time and can tolerate fluctuating water levels. Lastly, there is the upper area of the rain garden. This zone contains plant species that prefer drier soils. The irrigation system would be a mixture of drip irrigation and surface irrigation with spray heads. Irrigation system for the project would be limited to establishing the proposed vegetation. The selected landscape plantings are regional and native to the area and therefore are accustomed to the rainfall amounts of the region. The use of irrigation would be to supplement the naturally occurring rainfall with the retained subsurface water in the storage tanks under the central plazas. Link to detailed recommended planting list.
  5. 5. Landscape & Irrigation Strategies Bald Cypress White Oak River Birch Muhly - October Sweetbay Magnolia Prairie Wildrye Switchgrass Bluestem
  6. 6. Overall Site Plan & Section Service Yard Service Yard Service Yard Market Market Market Outdoor Market Outdoor Market Outdoor Market
  7. 7. Sections Street Section – Tree Boxes & Bioswale Street Section – Bioswale & Permeable Paving
  8. 8. Sections Promenade Section – Mid-block Water Collection Promenade Section – Water Collection Detail
  9. 9. Area Diagrams
  10. 10. Rendering
  11. 11. Rendering
  12. 12. Rendering
  13. 13. H&H Strategies Interconnected Channel and Pond Routing (&quot;ICPR&quot;) software, Version 3.10, created by Streamline Technologies, Inc. was used to model the proposed hydrologic and hydraulic conditions for this project. The software enabled us to accurately represent the Low Impact Design hydrologic techniques including the SCS Unit Hydrograph Method. The main advantage of using the SCS Method is it allows the properties of the soils to affect the hydrograph and the storm run-off calculations. In the proposed LID design analysis, the benefits of the engineered soils were reflected by adjusting the Curve Number to reflect a Type A soil in the improved areas. The hydraulic benefits of the Low Impact Design elements were modeled using a stage-area component which accounted for the total storage volume provided in the planter boxes, rain gardens and infiltration basins.
  14. 14. H&H Strategies Percent reduction of storm-water runoff volumes from existing conditions: 5 -Year: -51.0% 10 -Year: -61.9% 100 -Year: -75.6% Link to Engineering Modelling Data
  15. 15. Low Impact Development Notes <ul><ul><li>Storm Water Quality - Bioretention Cells Remove Suspended Solids and Metals </li></ul></ul><ul><ul><li>Several studies have been conducted over the years to study how Total Suspended Solids are removed using Bioretention Cells/Rain Gardens. A few examples are: </li></ul></ul><ul><ul><ul><li>Low Impact Development (LID) A Literature Review – U.S. EPA October 2000 EPA Document # EPA-841-B-00-005 </li></ul></ul></ul><ul><ul><ul><li>Stormwater Best Management Practices (BMP) Performance Analysis – Prepared for US EPA – Region 1 by Tetra Tech, Inc. Fairfax, VA for Massachusetts Department of Environmental Protection (“MDEP”). </li></ul></ul></ul><ul><ul><li>Low Impact Development (LID) A Literature Review – U.S. EPA October 2000 EPA Document # EPA-841-B-00-005 </li></ul></ul><ul><ul><ul><li>“ The Florida Aquarium Site Plan” Study drained concrete pavement through 4-foot grassy swale, over 78% TSS was removed. </li></ul></ul></ul><ul><ul><ul><li>Highway Grass Channel Study </li></ul></ul></ul><ul><ul><li>Highway Grass Channel Study </li></ul></ul><ul><ul><ul><li>Highways in North Virginia, Maryland and Florida studies the pollutant affects of using grass swales and channels to drain the highways. </li></ul></ul></ul><ul><ul><ul><li>The most appropriate test site to compare with Houston, Texas is the Florida highway, which has a gentle slope to the channel and has comparative soils. </li></ul></ul></ul><ul><ul><ul><li>Test results showed 98% TSS removal rate over life of the study. This directly related to lower velocities in the channel due to gentle slopes. </li></ul></ul></ul><ul><ul><li>Stormwater Best Management Practices (BMP) Performance Analysis – Prepared for US EPA – Region 1 by Tetra Tech, Inc. Fairfax, VA for </li></ul></ul><ul><ul><li>Massachusetts Department of Environmental Protection (“MDEP”). </li></ul></ul><ul><ul><ul><li>Identified long term cumulative performance for storm water best management practices, of which bioretention area was one of the tested practices. </li></ul></ul></ul><ul><ul><ul><li>The study resulted in a performance table which identified the pollutant levels removed based on how much run-off was treated. </li></ul></ul></ul><ul><ul><ul><li>The removal efficiency reflected on the MDEP tables for 1-inch treated run-off is 99% of TSS removed for all Land Uses studied. </li></ul></ul></ul><ul><ul><li>Design Criteria </li></ul></ul><ul><ul><ul><li>Design of bioretention cell is not a new idea. Been around for years. </li></ul></ul></ul><ul><ul><ul><li>Basic Cross-Section reflected in the following LID Handbooks for: </li></ul></ul></ul><ul><ul><ul><ul><li>City of San Diego, California </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Massachusetts Department of Environmental Protection </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Prince George’s County, Maryland. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Others </li></ul></ul></ul></ul><ul><ul><li>The basic cross-section has been slightly modified to adapt to the silty-clay nature of the Houston area, by implementing some of the latest advances in golf course drainage management studied by USGA to prevent clogging and sedimentation of the bioretention cells. </li></ul></ul><ul><ul><li>United States Golf Association has been heavily researching the best way to infiltrate and drain landscaped areas. </li></ul></ul><ul><ul><ul><li>Applying this research to storm water management and storm water quality resulted in a slightly modified standard bioretention cell design. </li></ul></ul></ul><ul><ul><ul><li>12” of engineered soil (sand and organics) is all that is necessary to provide necessary infiltration rates and still provide necessary growth medium for plantings </li></ul></ul></ul><ul><ul><ul><li>Removed gravel and geo-textile fabric from standard cross-section </li></ul></ul></ul><ul><ul><ul><li>Replaced with “Sieved Sand” and Perforated PVC Pipe with Filter Sock </li></ul></ul></ul>
  16. 16. <ul><ul><ul><li>The Sieved Sand is designed with a specific grain analysis to achieve soil BRIDGING </li></ul></ul></ul><ul><ul><li>Soil Bridging </li></ul></ul><ul><ul><ul><li>Soil Bridging is the term used to describe a condition where one soil layer is unable to penetrate a secondary soil layer due to grain sizes. </li></ul></ul></ul><ul><ul><ul><li>This technique yields to a longer life span of the bioretention cell and prevents sedimentation of the pores in the soil. </li></ul></ul></ul><ul><ul><li>6 foot grass vegetation filter </li></ul></ul><ul><ul><ul><li>Acts as a border around the bioretention cell and provides an extra level of sedimentation trapping to prevent the silty clays from clogging the bioretention cell </li></ul></ul></ul><ul><ul><ul><li>Provides a shoulder for the adjacent roadway </li></ul></ul></ul><ul><ul><li>Storm Water Quantity </li></ul></ul><ul><ul><ul><li>Storm run-off is handled by the minimal depth above the bioretention cell for each drainage area. </li></ul></ul></ul><ul><ul><ul><li>Developed storm water run-off is mitigated and released at LESS THAN pre-development rates. </li></ul></ul></ul><ul><ul><ul><li>A standard development, using a large detention basin, typically uses 0.65 acre-feet of detention volume per acre of developed property. The preliminary analysis of the bioretention/basin concept results in an estimated 0.25 acre-feet of volume per acre of developed property. </li></ul></ul></ul><ul><ul><li>Maintainability </li></ul></ul><ul><ul><ul><li>Native plant species chosen specifically for long term sustainability. </li></ul></ul></ul><ul><ul><ul><li>Native plants can handle the scorching, dry heat during the summer, but still be able to survive in heavy rain and very wet conditions. </li></ul></ul></ul><ul><ul><ul><li>Link to Bioretention Cell Maintenance Schedule (Excel sheet) </li></ul></ul></ul>
  17. 17. Cost Comparisons - Summary Estimate includes the cost of promenade and cross streets to the project limits. It does not include any costs associated with the buildings and land adjacent to the promenade. It was assumed that the aesthetic design intent would remain the same for the Traditional as well as the Low Impact Development. Factors to be noted are that any Traditional Development would require a large amount of Detention. If detention were to be provided within the project site, then close to 3 Acres of land would not be available for development resulting in significant loss in opportunity costs. If detention were to be provided off-site, then there would be a significant additional cost for pipe work. Another significant difference is maintenance and irrigation costs between the two types of development. LID has significantly lower long term maintenance costs and irrigation costs than the traditional model. The sub-surface grey water harvesting tanks, although an additional cost at the front-end would provide for the limited irrigation needs for the promenade as well as the cross streets passing through the promenade. <ul><li>Link to spreadsheet with breakdown of: </li></ul><ul><ul><li>Traditional Stormwater Collection System </li></ul></ul><ul><ul><li>LID Stormwater Collection System </li></ul></ul><ul><ul><li>Water Distribution System </li></ul></ul><ul><ul><li>Wastewater Collection System </li></ul></ul><ul><ul><li>Excavation and Paving </li></ul></ul>
  18. 18. Cost Comparisons
  19. 19. Cost Comparisons