Case Study: Dallas Green Infrastructure for Stormwater

Transcription

1 Case Study: Dallas Green Infrastructure for Stormwater Extension and Research Sandhya Mohan Fouad H. Jaber, PhD Biological and Agricultural Engineering Texas Agrilife, Texas A&M University System Urban Solutions Center, Dallas TX In a Nutshell Five LID BMPs to be built on the campus of Texas AgriLife Research and Extension, Dallas. The grant is funded by the Clean Water Act Section 319 urban nonpoint source pollution prevention program (TCEQ; EPA) BMPs Permeable pavement Bioretention area Rainwater harvesting Green roof Detention Pond Monitoring for hydrology, N, P, TSS, bacteria, legacy pollutant Chlordane Project Location Upper Trinity-White Rock Creek Watershed Clayey soil with underlying calcareous layer (Blackland Prairie Ecosystem) Representative of typical urban watershed Rationale and Goals Need for evaluation of LID practices in the field, especially Southern US. Need for data on adoption of LID practices on watershed scale Goals Reduction of runoff volume, pollutant load in a typical urban development Design, construction, evaluation of 5 LID BMPs Teaching tool for integration of LID practices (de novo or retrofit) 1

2 Permeable Pavement What is Permeable Pavement? Permeable pavement is a porous pavement surface with a gravel reservoir underneath. it temporarily stores surface runoff before infiltrating it into the subsoil or evaporates provides water quality treatment often appears as traditional asphalt or concrete but is without "fine" materials could also allow for grass growth Types of Permeable Pavement in Project Research in Permeable Pavements Compare various material effectiveness Water quality Paver blocks Porous asphalt Porous concrete Water quantity Clogging of surfaces Groundwater contamination Effect of soil type Turf Paver 2

3 Permeable Pavement Newly constructed parking lot Comparison of 5 types pavement Replication=3 45 experimental stalls among 110 total functional stalls Perforated underdrain pipes Total thickness = 16 inches 2 layers base course gravel layer Hydrologically separated with concrete curbs Monitoring Design Pervious Asphalt Cross section Pervious Concrete 3

4 Cross section of turf pavers Rain Garden What is a Rain Garden (Bioretention)? A rain garden is a beautiful landscape feature consisting of a planted shallow depression that collects rainwater runoff from roofs, parking lots and other impervious surfaces. Research Topics in Rain Gardens Pollutant load reduction Plant material Retention time for effective treatment Engineered top soil used Stormwater volume reduction Stormwater peak flow rate reduction 4

5 Rain Garden Monitoring Design Area to be determined based on final parking design Designed to retain storm 1.5 in Depth 3 feet Perforated pipe underdrain and corrugated overflow pipe Soil compost mix: 50% compost, 25% native soil, 25% expanded shale Built in impervious surface with curb cuts Demonstration Rain Garden at Texas AgriLife Research and Extension, Dallas Education Community Gardens 5

6 Bioretention Area Monitoring Design Volume Reduction Water Volume Inflow: Curve Number method and rain gauge Outflow: Flume and Levelogger Storage: Levelogger Water Quality Inflow: Grab samples Outflow: Grab samples % Reduc ction % 80.00% 60.00% 40.00% 20.00% 0.00% September 9, 2008 October 29, 2008 December 18, 2008 February 6, 2009 March 28, 2009 May 17, 2009 July 6, 2009 August 25, 2009 October 14, 2009 December 3, 2009 January 22, 2010 March 13,

7 Water Quality Infiltration Rates % Reduc ction % 80.00% 60.00% 40.00% 20.00% 0.00% September 9, 2008 October 29, 2008 December 18, 2008 February 6, 2009 March 28, 2009 May 17, 2009 July 6, 2009 August 25, 2009 NO3 Ortho-P Zn Cu October 14, 2009 December 3, 2009 January 22, 2010 March 13, 2010 Rain Garden had 8 inch of compost and 8 inches of gravel Infiltration rate in bioretention area: Reduce the time there is ponded water after a rain event in order to reduce mosquito breeding potential. Ability of the bioretention area to be fully functional between two events. Infiltration Rate and Outflow Event 3 (11/28) Average Infiltration Rate Infiltration Rate Depth (ft) Flow (cfs) in/hr Oct Dec Feb Mar May Jul Aug Oct Dec Jan Mar-10 Infiltration Rate Linear trendline /28/08 4:48 11/28/08 7:12 11/28/08 9:36 11/28/08 12:00 11/28/08 14:24 11/28/08 16:48 Time 11/28/08 19:12 11/28/08 21:36 11/29/08 0:00 11/29/08 2:24 11/29/08 4:48 11/29/08 7:12 The infiltration rate is greater than the surrounding native clay soil. This is attributed to the reduction of the clay layer in the bioretention area and the underlying calcareous soil. Raingarden storage Flume flow 7

8 Findings Other Demonstrations in DFW Volume reduction was found to be 70%. NO 3, Ortho-P, Zn, and Cu load reductions were 68%, 73%, 93%, and 97%, respectively. Reductions were both in loads and concentrations Infiltration rates reduced over time Commissioner Dickey s office (North Dallas) Wastewater Treatment Plant, Denton Horseshoe Arena, Midland,TX Myers Park, Collin County LID Demonstration Examples County, Year Demonstration, Funding Purpose Dallas, 2008 Dallas, 2009 Collin, 2009 Rain garden, AgriLife Dallas, funded by Agrilife Rain garden, Dallas Commissioner's office, funded by TCEQ Grant. Rain garden, Myer s park (Collin County Parks), Funded by TCEQ grant Flood mitigation, stormwater management Demonstration Erosion control, large parking area Midland, 2010 Rain garden, Horseshoe conference Control of erosion from roof runoff center, Midland, TX, Funded by where Rainwater harvesting was not Midland County possible Kauffman, 2010 Tarrant, 2010 Rain Garden, Southern Star Concrete Plant, Terrell, TX, 7500 sq ft (area of rain garden), Funded by Southern Star Concrete Residential rain garden, Alice Carlson Applied Learning Center, Funded by Tarrant County Master Gardeners Green certification and pollution reduction Flood mitigation and erosion control Green Roof Denton, 2010 Rain garden, Wastewater Treatment plant, Funded by City of Denton Stormwater management 8

9 What is a Green Roof? Green roofs involve growing plants on rooftops, thus replacing the vegetated footprint that was destroyed when the building was constructed A major benefit of green roofs is their ability to absorb stormwater and release it slowly over a period of several hours Research in Green Roofs Water Balance (ET; Infiltration; Runoff and Percolate) %Retention Thickness of growing media Energy benefits Water quality Plant selection Green Roof Substrate Green Roof Demonstration Component Manufactured green roof on one of AgriLife Buildings Built by Hydrotech, Inc Experimental Component 4 roof shelters, represent residential roofs Each divided into 4 parts Control roof shelter Soil medium, plants Soil medium, drainage layer, plants Standard commercial green roof Runoff volume, water quality 9

10 Monitoring Design Rainwater Harvesting Rainwater Harvesting Cisterns Retains water onsite All water applied on high infiltration areas (yard) Reduces total volume and peak flow Conserves water Research in Rainwater Harvesting Water quality for various roof materials Treatment required for various uses Effectiveness as a stormwater BMP Optimal sizing of tanks Water use based on irrigation management strategy Water quality in tank various depth 10

11 Rainwater Harvesting Experimental plot layout Demonstration Component Four cisterns (300, 500, 1500, and 2500 gallon) that serve AgriLife Buildings Storage and outflow measured Serves a drip irrigation system Experimental Component 4 roof shelters, represent residential roofs, 55 gallon tanks(3/plot) Turf lawn associated with each, drip irrigation 4 Treatments- Soil moisture, Evapotranspiration, Home owner (rain water), Control: Home owner (city water) Inflow, outflow, water quality Rainwater Harvesting Cisterns Detention Pond 300 Gallons tank 1500 Gallons tank 11

12 Detention Pond Stormwater control structures that provide both retention and treatment of contaminated storm runoff One of the more commonly used BMP Collection of runoff for long periods (upto 3-4 days), infiltration, sedimentation Research in Detention Pond Water quality treatment, sediments, nitrogen, phosphorous and sediment bound pesticide Tracking of flow regimes of ponds with changing surface topography Energy dissipators in the pond and at outflow- ledges, plants, berms, plunge pools Layout and Monitoring Plan Detention Pond Uniquely designed like meandering river, with typical stream cross section Higher length:width ratio Retains 1.5 inch storm runoff Retains 1.5 inch storm runoff Volume reduction, water quality Demonstration tool for stream restoration Drains into larger detention pond that is part of a larger, concurrent development (Urban Living Laboratory) 12

13 Watch this space! Acknowledgements This research was made possible by a CWA 319 (h) NPS grant provided by USEPA and TCEQ We would also like to thank Texas AgriLife Research for providing the location for the field work. Alan Plummer Associates, Inc. Resources i ti t /

14 Fouad H. Jaber, PhD Assistant Professor and Extension Specialist Biological and Agricultural Engineering Agrilife Extension Texas A&M University System Urban Solutions Center, Dallas TX