BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

1.3.1.3 PROJECTS GREATER THAN 5 ACRESTypically a large redevelopment or publicly funded water quality improvementproject that analyzes, designs, and implements improvements for an urban areaon the order of 5 to 100 acres, including roadways and other public stormwatersystems.These projects are complex to design and implement compared to the otherproject categories, and may use the Project Delivery Process developed by theStorm Water Quality Improvement Committee (SWQIC) 8 . Project areas maybe comprised of multiple land uses and land ownership. Significant conveyancefacilities are required to serve multiple tributary areas and flow paths, oftenwith differing hydrologic and water quality characteristics. Stormwater designflows depend on routing and storage in the drainage system and typically mustbe considered in the context of design storm events rather than a single peakflow. Compliance with municipal drainage design standards intended to protectpublic safety is typically a requirement for the project. Stormwater storage andtreatment systems are potentially complex, and sizing may not be standardizeddue to variable opportunities and constraints in individual project areas. Analternatives analysis process is typically conducted to formulate and exploreoptions for improvements to maximize water quality improvement within siteor project constraints. A pollutant load reduction estimate is usually requiredto evaluate alternatives, obtain permits, evaluate environmental effects, andinform TMDL compliance.1.3.2 KEY TO HYDROLOGIC AND STORMWATER QUALITY ANALYSISMETHODSTable 1-1 relates each project category to typical analysis methods forhydrology and water quality for: 1) sizing conveyances; 2) sizing storagefacilities; and 3) estimating pollutant loads. Table 1-1 identifies therecommended method for each project category in the typical case, andprovides a brief discussion on considerations for using other analysis methods.In general, the simplest methods that provide adequate results under typicalcircumstances are shown as the recommended method. More complex methodsmay be suitable, but additional resources and expertise are required to utilizethem and they may not be warranted unless specific conditions require theiruse. Brief descriptions of some cases where more, or less, complex analysis maybe suitable are provided in Table 1-1. The table serves as a key for the reader toreference specific Summary Sheets that are most applicable to a particularproject. The Summary Sheets include more details about each method andreferences for additional information. The reader should note that Table 1-1provides recommendations based on hydrologic and water quality objectives,but individual public works and regulatory agencies may have criteria that8SWQIC, 2004, Collaborative Storm Water Quality Project Delivery for the Lake Tahoe Basin,http://www.trpa.org/documents/swqip.pdfCHAPTER 1: Urban HydrologyTRPA BMP HandbookPage 1-10 2012