Developing a Bacteria TMDL in Engineered Channels: The Los Angeles River, A Case Study

Many rivers in the US are channelized to control stormwater runoff and reduce the impacts of major flood events in the region. The characteristics of channelized rivers may vary from a completely concrete-box or trapezoidal channel to those with "soft-bottom" streambeds. These complex yet structurally simplified channels suffer from the problems of altered habitats and degraded water quality resulting from point and non-point discharges, homeless populations, and other factors. Despite limited public access, these channels are subject to water quality regulations. The Los Angeles River (LAR) that flows through Los Angeles County, California, is one of such engineered channels with a number of water quality impairments. The LAR and its tributaries are on the US EPA 303(d) list as impaired for recreational beneficial uses due to fecal coliform bacteria. Several publicly-owned treatment plants (POTWs) discharge to the LAR; what is notable is at these locations, the LAR attains bacteria standards. The focus of this paper is on the development of the LAR Bacteria TMDL in the context of stakeholder participation and planning to revitalize the river through increased habitat, recreation and development, against the reality of a river that is officially off-limits to public access.