Aeration Device in Lower San Diego River to Improve Dissolved Oxygen
Aeration Device in Lower San Diego River to Improve Dissolved Oxygen
Summary
SCH Number
2017068463
Lead Agency
San Diego River Conservancy
Document Title
Aeration Device in Lower San Diego River to Improve Dissolved Oxygen
Document Type
NOE - Notice of Exemption
Received
Document Description
Increase dissolved oxygen (DO) levels above the average value (2.75mg/L) at this location in the San Diego River to meet or exceed the Basin Plan objective of 5mg/L by installing small solar powered floating aerators. This will improve aquatic habitat for fish and benefit other aquatic and terrestrial wildlife resources.
Adequate levels of dissolved oxygen (DO) are critical for the survival of aquatic life. The recommended minimum level of DO for the San Diego River is 5mg/L. Based on the water quality data collected throughout the lower San Diego River by our RiverWatch program in the last five years, on average the DO levels have been 2.75 mg/L. These inadequate levels result in fish die-offs and make this section of the San Diego River less suitable habitat for other native aquatic species and migratory birds. Low DO levels also result in malodors, which deter community use of the River Park trail and negatively affect the residents and businesses of Mission Valley. The San Diego River Park Foundation will implement through a grant from the San Diego River Conservancy a two year aeration pilot project for the San Diego River in Mission Valley, within the First San Diego River Improvement Project (FSDRIP) near Qualcomm Way. The project aims to improve dissolved oxygen levels through increased aeration that is currently lacking in the system due to ponding and lack of flow particularly in summer months. This technique, first recommended in a 2004, Bureau of Reclamation Study: Hosler, D.M. 2004. Recommendation of Activities to Restore Natural Function to the San Diego River. Technical Memorandum No. 8220-04-05. Bureau of Reclamation, Technical Service Center, Denver, CO is also referenced in the City of San Diego River Park Master Plan, (p. 36), as a potential method to improve ponded sections of the San Diego River.
To achieve this increased aeration, small floating solar aerators will be installed in eastern FSDRIP near Qualcomm Way. The aerators will be buoyed mid-stream and function to increase circulation, dissolved oxygen and additionally, reduce aquatic vegetation growing at the stream margins such as (Ludwigia sp.). A secondary benefit from improved dissolved oxygen levels and decreased aquatic vegetation is a reduction in hydrogen sulfide released into the atmosphere from the water column.
The United States Bureau of Reclamation (USBR) will provide technical guidance and assistance with installation and maintenance of the aeration system and San Diego State University (SDSU) will provide pre during the post project monitoring to document the magnitude and extent of water quality improvement by examining nutrient and chemical parameters as well as biological oxygen demand. Urban Corps of San Diego will provide assistance with maintenance and removing the aerators via small boats launched into FSDRIP from the concrete abutment at Qualcomm Way. Removal of the aerators would occur ahead of storm events to prevent loss or damage of the aerators from flooding.
About the aerators: The solar powered aerators are small 1-2 feet diameter cylinders with a solar panel on the top. They float on the surface with an anchor holding them in place. There will not be any fountain or spray coming out and it would have some small surface bubbling. They run at an extremely low voltage so noise would be less than a stationary bike. Set next to the road noise on Qualcomm Way it would be inaudible. Per USFWS recommendations, an anti-reflective film coating will be added to the solar panel to prevent birds from being attracted to them.
32.773085, -117.14144.50 Meters west of Qualcomm Way within the San Diego River.
Notice of Exemption
Exempt Status
Categorical Exemption
Type, Section or Code
S: 15304(d)
Reasons for Exemption
The small aerators represent a minor alteration to the water and the aerators will be installed within the First San Diego River Improvement Project, an area designated for preservation and protection of biological resources. The aerators will improve dissolved oxygen which will result in an improvement of habitat for fish and other wildlife resources in the area.
