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| Title | Snohomish River Estuary Dry Season TMDL Study Phase II | |
| Month-Year Published | June 1997 | |
| Online Availability |
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| Short Description |
A water quality modeling study of the Snohomish River Estuary system from Possession Sound to river mile 20 was conducted using an Environmental Protection Agency supported water quality simulation program (WASP5) model to simulate hydrodynamics and water quality. The WASP5 model was developed to assess the capacity of the estuary system to assimilate oxygen consuming pollutants from point and nonpoint sources. The model was calibrated using data collected in August and September 1993 and confirmed (verified) using data collected in August 1996. (Also see abstract below) | |
| Publication Number | 97-325 | |
| Author(s) | Cusimano, B. | |
| Print Availability | ||
| Number of pages | 65 pp. + app. (119 total) | |
| Keywords | ammonia, chemical, chemical oxygen demand, dissolved oxygen, environmental, Environmental Protection Agency, lake, marine, mixing zone, model, nonpoint, pH, point source, river, Snohomish River, study, TMDL, Total Maximum Daily Load, toxic, toxicity, treatment, waste, wastewater, wastewater treatment plant, water, Water Quality | |
| Abstract | Long Description |
A water quality modeling study of the Snohomish River Estuary system from Possession Sound to river mile 20 was conducted using an Environmental Protection Agency supported water quality simulation program (WASP5) model to simulate hydrodynamics and water quality. The WASP5 model was developed to assess the capacity of the estuary system to assimilate oxygen consuming pollutants from point and nonpoint sources. The model was calibrated using data collected in August and September 1993 and confirmed (verified) using data collected in August 1996. An interim report summarizing water quality in the study area and the development of the WASP5 model was published in 1995. The present document is the final report for this Total Maximum Daily Load (TMDL) study. The water quality model predicted that natural conditions in a large portion of the estuary would be below dissolved oxygen standards under critical conditions. The model also predicted that point sources of oxygen-consuming pollutants would cause an exceedence of the 0.2 mg/L deficit allowed by the marine criteria when natural conditions are below the standard (the allowable deficit was also applied to the freshwater portion of the modeled area). The model was used to recommend waste load allocations (WLAs) for the following existing and proposed point sources of carbonaceous biochemical oxygen demand (CBOD) and ammonia BOD: the City of Snohomish Wastewater Treatment Plant (WWTP), Lake Steven′s Sewer District WWTP, the City of Marysville WWTP, the City of Everett WWTP, and the proposed Smith Island WWTP. However, the recommended WLAs for ammonia are subject to changes based on mixing zone toxicity limitations that may be established in the future. |
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