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EPA Permeable Surface Research - Poster
Citation:
BORST, M., A. ROWE, E. STANDER, AND T. OCONNOR. EPA Permeable Surface Research - Poster. Presented at WEFTEC 2010, New Orleans, LA, October 02 - 06, 2010.
Impact/Purpose:
To inform the public.
Description:
EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely mimic the natural hydrology and recognizes the many tests demonstrating reduced runoff. Currently, the uncertain maintenance requirements and remaining concerns about the ability of the surfaces to meet these goals for the multi-decade periods needed as part of stormwater management systems hinder wider adoption. EPA’s National Risk Management Research Laboratory (NRMRL) recognizes these barriers and has under taken a long-term research project to document the capabilities of three permeable surfaces using a full-scale, operating parking lot. Others have reached similar conclusions regarding the need for long term monitoring, (e.g., Dietz 2007) and some other extended efforts are ongoing (e.g., Brattebo and Booth 2003). A deteriorated parking area at the Edison Environmental Center required extensive repairs or replacement as part of routine facility management. This provided NRMRL an opportunity to partner with the design team to concurrently construct a research platform and reduce the environmental footprint of this EPA-owned property while providing a needed, functioning parking area. The lot uses permeable surfaces for the parking spaces only. The travel lanes and one parking area, acting as a control, are paved with traditional Hot Mix Asphalt (HMA). The 110-space lot includes sections surfaced with porous concrete, interlocking concrete pavers, and porous asphalt designed in cooperation with the respective trade organizations. The 1-acre parking lot rests over a storage layer made from Recycled Concrete Aggregate (RCA) that was crushed and screened on-site using the old parking area as feedstock. The thickness of the RCA storage layer varies along the length of the lot with the surface stops from north to south. The RCA rests on a permeable geotextile placed over the underlying soil. The parking rows are about 43-m wide. The width of three permeable-surface parking rows is divided into nine sections. Odd-numbered sections drain through the storage gallery into the underlying soil while the even numbered sections have an impermeable 45-mil EDPM liner placed 30 cm below the surface. The impermeable liner captures all infiltrating water, routing the water through a PVC drain that carries the collected infiltrate to covered HDPE tanks. The individual sections are treated as statistical replicates. The tanks allow for mixing and sample collection to support laboratory analysis of specific environmental stressors. The extreme end sections are instrumented with time domain reflectometers (TDRs) and thermistors to monitor the passing wetting front and temperature. There is a collection of piezometers at two depths and a slotted well in the underlying soil positioned in two center unlined sections. NRMRL positioned one set of the TDRs within the RCA layer 38 cm below the parking surface. The second set is in the underlying soil 10 cm below the geotextile. TDRs are placed in pairs for redundant measurements and in recognition that failed sensors cannot be replaced. The instruments respond to the impedance changes caused by the moisture content and temperature of the material surrounding the probes. The TDRs are designed primarily for use in a soil environment and the installation in the RCA layer is a nonstandard application.
