Dry Dock Discharge Dye Study

摘要

This document describes results of a dye release study performed at Puget Sound Naval Shipyard & Intermediate Maintenance Facility performed in April 2004. The goal of the study was to measure the amount and spatial extent of dilution of dry dock discharge water when mixed into adjacent Sinclair Inlet waters under normal operational conditions. The approach taken was to add known amounts of fluorescent dye to dry dock discharges and measure its concentration once it is mixed with the adjacent receiving waters. Dye measurements were made at a fixed point near to the discharge point to determine the minimum dilution in the plume. The spatial distribution of dye was also mapped as a function of time to assess the full spatial extent of mixing over a range of tide conditions. Normal dry weather discharge of ground water mixed with dye from dry docks 6 and 4 was successfully mapped in the adjacent inlet waters during both flood and ebb tide conditions. The discharge plumes rose to the surface relatively quickly after leaving the discharge pipe because of their lower density relative to the surrounding inlet water. Plume water reached the surface within several meters of its discharge from Pump Well 6 underneath pier 9. The plume surfaced about 30 m out from quay wall (approx. 40 m from the end of pipe) from Pump Well 4. The increased distance away from Pump Well 4 was presumably a result of a higher discharge velocity through a special check valve unit. At Pump Well 6, the 'boil' region was diluted by only a factor of 1.5 whereas the boil off Pump Well 4 was diluted by a factor of 7. However, there was a relatively quick and efficient mixing of the plumes at both locations once they reached the surface. Background levels were typically reached within 100 m or so of where the plumes surfaced.