Projects & Programs
Assessment for 401 Water Quality Certificate and NPDES Permit, Puerto Rico
The Caribbean Petroleum Refinery (CPR) owns and operates a petroleum refinery in Bayamon, Puerto Rico. CPR's existing National Pollutant Discharge Elimination System (NPDES) permit allows for discharges of treated process water and stormwater from two outfalls that discharge to Las Lajas Creek and ultimately to San Juan Bay. The refinery was routinely exceeding its NPDES permit parameters and was required to achieve compliance by the regulatory agency. As a result, CPR has undertaken a comprehensive program to improve the quality of its discharges. PNNL staff, developed a NPDES compliance strategy for the refinery that included facility improvements, engineering controls, source control studies, improved treatment plant performance and modification of permit limits.
For the permitting of the new outfall for CPR, two field data collection programs were performed within San Juan Bay. To gain regulatory approval for the proposed outfall, a circulation and plume tracking study was initiated. Fixed-point current meters equipped to measure time series of current speed, direction and water temperature, salinity and tide were installed at the site. To simulate the plume from the proposed outfall, Rhodamine dye was pumped into the bay at the proposed outfall site. The resulting dye plume was tracked using a towed sensor array consisting of fluorometers, temperature, conductivity and depth sensors. The plume was continuously tracked using two boats from the initiation of discharge until final mixing was achieved and the plume was no longer detectable. In addition to the towed array, vertical profiles of dye concentration, salinity and temperature were also collected at stations throughout the bay. These data were then combined to establish circulation patterns and plume movement within the bay.
A second study was required by the agencies to determine long-term impacts of the proposed outfall. This study was designed to evaluate the potential for recirculation of the discharge plume following tidal cycles. To evaluate the potential for recirculation, Rhodamine dye was discharged at controlled rates for 24 hours. Vertical arrays of fluorometers located at and offshore of the proposed outfall location monitored the dye concentration throughout the water column for seven days following completion of dye discharge.
Data obtained from several surveys were used to develop hydrodynamic and water quality models (UDKHDEN, RMA-2, and RMA-4) that provided the basis for designing a diffuser, determining dilution potential, establishing the size of the mixing zone and assessing the effects of the discharge in the farfield beyond the mixing zone.
Project Highlights:
- Hydrodynamic and water quality models (UDKHDEN, RMA-2, and RMA-4) were used to simulate circulation, flushing and effluent fate and transport in San Juan Bay
- Results were used to demonstrate the discharge will not impact water quality in San Juan Bay
- Results were used in support of a mixing zone request and to help design an effective diffuser.