Abstract Title

Session S-01A: Current Salish Sea Water Quality

Proposed Abstract Title

Anthropogenic Dissolved Oxygen Depletions in Budd Inlet

Keywords

Marine Water Quality

Location

Room 6C

Start Date

1-5-2014 5:00 PM

End Date

1-5-2014 6:30 PM

Description

Portions of Budd Inlet do not meet the water quality standards and are on the Clean Water Act Section 303(d) list for dissolved oxygen (DO). The project involved data collection to characterize the sources and processes relevant to the impairments as well as development of a calibrated computer model to predict observed circulation, and water quality characteristics. Major processes included in the model were dissolved oxygen depletions due to eventual decay of algal blooms (previously mediated by anthropogenic nutrient loading), and steady state oxygen depletion in the sediment. Dissolved oxygen concentrations under natural conditions were predicted using the calibrated computer model. Finally, predicted dissolved oxygen concentrations under existing and future conditions were compared with State’s numeric dissolved oxygen standard and natural conditions to assess temporal and spatial violations of the standard. The combined effects of nonpoint and point sources currently exceed the pollutant loading capacity of Budd Inlet and Capitol Lake for nutrients. Pollutant load reductions are required to meet water quality standards for DO. Several scenarios of anthropogenic source reductions were evaluated including removal of Capitol Lake dam, advanced nitrogen removal at the smaller municipal wastewater treatment plants, relocation of LOTT outfall, and reductions in external anthropogenic nutrient loads north of Budd Inlet. There is a critical area in East Bay of Budd inlet where the magnitude of the dissolved oxygen violation is the largest. At this location the Capitol Lake dam cause a dissolved oxygen depletion of about 2 mg/l, where as the rest of the depletion (approximately 1 mg/L) is caused by the combined effect of anthropogenic nutrient loads from the open boundary (external sources) and local point and nonpoint sources.

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May 1st, 5:00 PM May 1st, 6:30 PM

Anthropogenic Dissolved Oxygen Depletions in Budd Inlet

Room 6C

Portions of Budd Inlet do not meet the water quality standards and are on the Clean Water Act Section 303(d) list for dissolved oxygen (DO). The project involved data collection to characterize the sources and processes relevant to the impairments as well as development of a calibrated computer model to predict observed circulation, and water quality characteristics. Major processes included in the model were dissolved oxygen depletions due to eventual decay of algal blooms (previously mediated by anthropogenic nutrient loading), and steady state oxygen depletion in the sediment. Dissolved oxygen concentrations under natural conditions were predicted using the calibrated computer model. Finally, predicted dissolved oxygen concentrations under existing and future conditions were compared with State’s numeric dissolved oxygen standard and natural conditions to assess temporal and spatial violations of the standard. The combined effects of nonpoint and point sources currently exceed the pollutant loading capacity of Budd Inlet and Capitol Lake for nutrients. Pollutant load reductions are required to meet water quality standards for DO. Several scenarios of anthropogenic source reductions were evaluated including removal of Capitol Lake dam, advanced nitrogen removal at the smaller municipal wastewater treatment plants, relocation of LOTT outfall, and reductions in external anthropogenic nutrient loads north of Budd Inlet. There is a critical area in East Bay of Budd inlet where the magnitude of the dissolved oxygen violation is the largest. At this location the Capitol Lake dam cause a dissolved oxygen depletion of about 2 mg/l, where as the rest of the depletion (approximately 1 mg/L) is caused by the combined effect of anthropogenic nutrient loads from the open boundary (external sources) and local point and nonpoint sources.