An Integrated Approach to Assess Stormwater Impacts to Marine Receiving Water Environments - Case Study Assessment of the La Jolla Shores and Scripps Areas of Special Biological Significance (ASBS) in San Diego, CA
The variable nature of storm water runoff presents unique challenges with regard to accurately characterizing impacts to the receiving waters. A multiple line of evidence approach (MLOE) is needed to better characterize potential biological impacts and stressors of concern. Such an approach can effectively identify and prioritize future monitoring and Best Management Practice (BMP) efforts where needed most. Highlights of an approach currently being conducted in the La Jolla Shores and Scripps Areas of Special Biological Significance (ASBS) will be discussed with a focus on water column chemistry and toxicity during this presentation. These studies support Ocean Plan Special Exemption requirements, but go a step further to ensure all of the required monitoring data, along with any supporting special studies, are used effectively to assess whether natural water quality is maintained. The risk of impacts due to multiple potential stressors and natural factors including anthropogenic inputs, geography, oceanographic conditions, freshwater inundation, and human use activities (i.e. trampling of the intertidal zone) must all be considered as well. Although there are often chemical constituents of concern in the storm water runoff, as well as toxicity, rapid mixing and dilution is evident in the immediate marine receiving waters for these ASBS. Understanding the magnitude and duration of exposure is essential for an accurate assessment. The rocky intertidal zone can also be heavily impacted by both freshwater inundation at low tide and human trampling. Preliminary results of this integrated approach to date indicate that these stressors may outweigh impacts due to transient chemical constituents during runoff events. Additional follow up studies are currently being performed to better tease out the stressors before proposing future BMPs. Innovative in situ methods to better evaluate potential impacts will be highlighted and presented with an interactive hand-on demonstration of specialized equipment now being tested. This presentation will also provide an introduction to complimentary special studies used to support the developing conclusions of this approach including pulsed study toxicity exposures, bioaccumulation monitoring, and in situ freshwater plume monitoring; all submitted for consideration in this session.