Pacific Southwest Research Station

Priority Urban Stormwater Monitoring to Directly Inform the Pollutant Load Reduction Model (PLRM)

Full title: Priority urban stormwater monitoring to directly inform the Pollutant Load Reduction Model (PLRM)

Lead Researchers: Nicole Beck, 2nd Nature LLC

Abstract

The initial version of the Pollutant Load Reduction Model (PLRM) is currently in development by northwest hydraulic consultants (nhc), 2NDNATURE, and Geosyntec Consultants through grants provided by the US Army Corps of Engineers (USACE) and the Nevada Department of Environmental Protection (NDEP). The objective of the PLRM is to provide Lake Tahoe resource managers with a tool to evaluate pollutant load reduction alternatives for urban storm water quality improvement projects. The research team submitting this proposal is the PLRM development team and the SNPLMA research results will directly improve confidence in PLRM loading estimates, particularly for very fine sediment loads for Lake Tahoe urban areas. The PLRM estimates pollutant loads using two primary water quality functions, Characteristic Runoff Concentrations (CRCs) and Characteristic Effluent Concentrations (CECs). A CRC is a representative concentration for a pollutant of concern in runoff from a specific urban land use and associated condition. A CEC is a representative effluent concentration for a pollutant of concern from a specific storm water treatment BMP type (SWT). When combined with continuous runoff hydrology from the PLRM, CRCs and CECs provide a representative estimate of average annual pollutant loading and a relative comparison of average annual pollutant loading among alternatives. The greatest limitation in the initial version of the PLRM (expected to be released in early 2009) is the lack of very fine sediment data (<20 microns) to inform CRCs and CECs. The funding for research in this proposal will be highly cost effective by 1) building on the research team's experience with PLRM development, 2) building on previous analyses of existing data to create the PLRM CRC and CEC database, and 3) augmenting an initial phase of urban stormwater data collection to inform PLRM currently being initiated for the USACE (2008). The goals of this research are to 1) provide improved scientific basis to estimate pollutant CRCs (focusing on very fine sediment) and their variability with land use conditions and 2) estimate very fine sediment CECs for typical Lake Tahoe SWTs and their variability with fundamental design parameters. This research addresses two of the SNPLMA Water Quality subthemes (2A and 2B). The CRC research will address both Water Quality subthemes 2A and 2B and the CEC research will primarily address Water Quality subtheme 2A, all of which will directly inform PLRM data gaps.