Successful Implementation of a Bacteria TMDL in a Complex Urban Environment
The Santa Ana Regional Water Quality Control Board (Board) adopted the Middle Santa Ana River (MSAR) bacteria TMDL on Santa Ana River Reach 3, portions of Chino Creek and Cucamonga Creek and Prado Park Lake in 2005. The TMDL established wasteload allocations (WLAs) for urban MS4s and confined animal feeding operation discharges, and load allocations for agricultural and natural sources. The TMDL established the end of 2015 as the dry season compliance date. The MSAR Watershed Bacteria TMDL Task Force (Task Force), administered by the Santa Ana Watershed Project Authority, was established in 2007 to support a collaborative approach to TMDL implementation across the large multi-jurisdictional watershed area. Through the combined resources of multiple stakeholders, required TMDL deliverables including a watershed monitoring program have been implemented in a cost-effective manner.
In January 2010, the Board adopted new MS4 permits for Riverside and San Bernardino Counties that incorporated TMDL requirements applicable to MS4 permittees in the MSAR watershed. The permit required the permittees for each County to develop a Comprehensive Bacteria Reduction Plan (CBRP). The CBRPs, approved by the Board in February 2012, established a multi-faceted plan for attaining the MS4 permit’s water quality based effluent limits for the TMDL through implementation of a comprehensive program to reduce significant controllable sources of bacteria in urban runoff. Emphasis was placed on identifying (and eliminating) high-risk human pathogen sources.
While each County has deployed typical BMPs to mitigate bacteria (sweeping, pet waste, conservation, illicit discharges, septic systems, transient encampments, etc.), the Counties have implemented different strategies that integrate with other high priority water and environmental management needs in their respective areas of the watershed. For example, San Bernardino County focuses on collaboration with water agencies to manage more than 110 retention/recharge basins to capture and recharge nearly all dry weather urban runoff before it reaches an impaired waterbody. In Riverside County, where a comparable network of water management facilities is not yet available, the County is implementing smaller pilot projects to intercept and divert dry weather urban runoff where such diversion does not harm downstream environmental or water resource needs. This consideration is necessary because some channels tributary to the Santa Ana River convey not only urban runoff but also potable water, groundwater and/or treated wastewater for habitat support and/or downstream water supply uses. Eliminating and/or rerouting such discharges would cause significant harm to these uses, which are a priority for the region.
Monitoring data and watershed study results demonstrate that CBRP implementation has been instrumental in managing and mitigating controllable bacteria sources, eliminating sources of bacteria from impacting impaired waters and making significant progress towards compliance with MS4 WLAs. Indicators of progress include significant declines in dry weather flow, dry weather decreases in total bacteria mass and reduction in detections of human sources of bacteria. MS4 permittees continue to work collaboratively through their respective MS4 programs and with the Task Force to rigorously implement the CBRPs to mitigate controllable bacteria sources. This presentation focuses on the collaborative approach to TMDL implementation and demonstration of the significant progress achieved complying with MS4 WLAs in a complex urban environment.