CSA Implements Innovative Technology for Tracing Sewage Outfalls

Since 1999, CSA has performed comprehensive environmental monitoring for the Puerto Rico Aqueduct and Sewer Authority (PRASA) as a subcontractor to CH2M to evaluate compliance with receiving water quality standards and describe environmental conditions around six offshore submarine discharges. Typical studies conducted by CSA and CH2M during the past 14 years include mixing zone studies, sediment sampling and testing, measurement of water column properties such as pH, dissolved oxygen, and currents, and water quality sampling of influent, effluent, and receiving water.

CSA implemented acoustic technology for an innovative mixing zone dye study for PRASA in which a SIMRAD EK60 scientific echosounder system (with split-beam transducers operating at 38 and 200 kHz) was used to observe the outfall plume in the water column prior to and during the course of the dye study. The EK60 echosounder system is the same system used on a number of National Oceanic and Atmospheric Administration (NOAA) research vessels performing fisheries survey work and is designed primarily to characterize fish and zooplankton communities in the water column. Because the system provides a synoptic view of the water column, it is a useful and relevant tool for other applications in the marine environment. CSA has continued to use this approach, having done so as recently as last month.

During the recent PRASA study, echograms produced by CSA’s innovative techniques helped CH2M scientists quickly visualize the outfall flow and determine the depths and other characteristics of the plume, as well as improve sampling of the plume features using ship-deployed water column sensors.

“Our clients at CH2M were pleased with the utility of the technology and the informative nature of the echogram imagery, and plan to include the imagery in their report to PRASA” relayed Ed Hughes, a CSA scientist with expertise in acoustic technology. “I was also pleased with the successful use of the acoustic technology in this particular application – it really helps in seeing the bigger picture.”

The success of the innovative study resulted in adoption of the system for future sampling events to improve understanding of water quality associated with offshore sewage outfalls in Puerto Rico.