Port of Stockton
2201 W Washington St.
Stockton, CA 95203
PH 209-946-0246
FX 464-1251

Aeration Facility

When it comes to the overall health of an aquatic ecosystem, the amount of dissolved oxygen (DO) in the water is a good indicator. DO not only allows fish and other aquatic organisms to breathe, but also plays a crucial role in the breakdown and decomposition of organic pollutants that find their way into our waterways. DO levels usually range from 3 to 10 milligrams per liter (mg/L), with most aquatic life requiring greater than 5 mg/L to maintain a healthy and diverse population. Some of the factors that affect DO concentrations include water temperature, water depth and flow rate, and the amount of organic material present in the water.

The waters around the Port of Stockton have had historically low DO concentrations. This is due in large part to the geometry of the Deep Water Ship Channel and the low flows in the San Joaquin River.  In an effort to promote a healthier waterway, the Port operates and maintains an aeration facility at the confluence of the Deep Water Ship Channel and the San Joaquin River. The facility consists of two jet aeration devices that pump atmospheric oxygen into the water at a rate of approximately 2,500 pounds per day. The aerators work by pumping air to the bottom of the river, where streams of bubbles are injected into the water. As the bubbles rise to the surface, a portion of the oxygen they contain dissolves into the water. 

Throughout the year, the Port operates the aerators whenever DO concentrations drop below 5.2 mg/L. However, from August to November, that threshold is raised to 6.2 mg/L to benefit the winter-run of the endangered Chinook salmon that pass through on their way to spawn upstream. DO levels in the San Joaquin River are monitored daily by the Port of Stockton Environmental and Regulatory Affairs Department using a monitoring station provided by the California Department of Water Resources.  Data are collected from this station every 15 minutes, and monitoring is updated every hour. Current data are available for viewing here.

Although the existing aerator does not eliminate all of the DO problems in the channel, it has been demonstrated that aerators there work well. The Port is currently partnering with the Department of Water Resources and the California Bay-Delta Authority to build a much larger aeration unit at Dock 20. This unit is different in that it consists of a large u-tube that diffuses pure oxygen into river water that is then returned to the river. Construction on the new aerator is nearly complete, and testing is expected to start soon. For more information about that project, click here.