Results

Both products of the study were found to be useful for detecting anomalous discharge-surfacing events and for helping to separate beach contamination events caused by an outfall from those caused by tidal or rain-caused discharges of stagnant water from nearby lagoons. The current analyses, which were verified by field sampling, helped estimate the possibility of effluent reaching the beaches. Follow-on projects for EPA evaluated other remote sensing data types (radar, optical, and multispectral) for monitoring new outfall and sewage runoff in San Diego and across the border with Mexico.

Barriers

The pace of remote sensing technology transfer for coastal runoff and effluent discharge applications is hampered by the following:

• Data timeliness. In most monitoring situations, especially when a spill or similar event is occurring, data must be processed, analyzed, and delivered to the end user in less than 24 hours to be useful for guiding management or remedial efforts. This is possible only with data from AVHRR, the Sea-viewing Wide Field-of-View Sensor, and possibly the Moderate Resolution Imaging Spectrometer, which offer poor spatial resolution for most applications.

• Data cost. All synthetic aperture radar and high-resolution optical remote sensing data are currently priced too high to be affordable for effective continuous coastal monitoring efforts. Given the constantly changing ocean environment, remotely sensed data lose their value extremely quickly-yesterday’s image has little or no value today.

• Resistance to increased monitoring capability. Remote sensing cannot replace field monitoring, which is needed to sense bacteria, ammonia, or similar variables directly. Adding remote sensing to field sampling programs raises the potential for more frequent apparent positive signals that will only complicate meeting current monitoring, performance, and compliance requirements. There is little incentive for the districts to spend funds that will further complicate their situation.