Newhall Ranch is a master-planned development project located in northwest Los Angeles County that clusters planned development into villages. Geosyntec has been assisting the Newhall Land and Farming Company (Newhall Land) with stormwater management planning, analysis, permitting, and design since 2002.
This decade-long process has occurred simultaneously with multiple revisions to the stormwater regulations governing the project, including the Los Angeles County Municipal Separated Storm Sewer System (MS4) permit (2001 and 2012) and additional conditions established through negotiations with regulatory agencies for environmental permits. The evolution of the stormwater management requirements necessitated adaptation of the Newhall Ranch stormwater master plan throughout the process. This paper describes the evolution of regulations and the associated project stormwater performance standards and the Best Management Practice (BMP) selection/analysis/modeling methods that were developed to satisfy these evolving regulations.