Operations and Maintenance

The Marsh requires tidal inflow and outflow from the Santa Ana River through two tidal gates. Fresh water, or stormwater runoff, enters the Marsh from the adjacent lands to the north, south and east. Water from the Santa Ana River will enter the Marsh until the river rises to 3.5 feet above Mean Sea Level (MSL), at which time the tide gates automatically close. The storage capacity of the Marsh is adequate to prevent the water level, from local runoff and precipitation, from rising in excess of 6.0 feet above MSL. As designed, sufficient storage is provided within the Marsh area to prevent flooding damages to the adjacent residences during a *0.01 annual exceedance probability event. The AEP is the probability that upland flooding will occur in any given year considering the full range of possible annual floods.  

United States Army Corps of Engineers performs periodic maintenance of the Marsh including dredging of accumulated sediments near the area’s inlets, habitat management in the form of debris (trash) removal, removal of invasive species, and planting to reduce erosive processes along the channel banks and adjacent Santa Ana River levee.

Orange County Public Works is responsible for operation and maintenance of the adjacent Santa Ana River levee, tidal gates and outlet pipes and drains along the levee. Orange County Sanitation District maintains a wastewater pipeline under the access road that separates the upper and lower portions of the Marsh.

The City of Newport Beach operates an oil production facility within the marsh and is also responsible for maintenance of Semeniuk Slough which connects to the Marsh on the east side.

All USACE maintenance and monitoring activities are performed between Sept. 16 to Feb. 14 to avoid nesting season except for eelgrass monitoring, breeding bird monitoring, tidal range monitoring, and fence maintenance. Eelgrass monitoring will occur during the peak growth season in spring and summer months. Tidal range monitoring occurs in July to capture larger tides and limited rainfall. To avoid habitat damage due to trespassing, fence maintenance may occur during nesting season in the presence of a trained ornithologist.

Routine maintenance activities and frequencies are listed in the table below:

Activity Description:

Frequency:

Trash and Debris Clearing

1 year

Weeding and Vegetation Control

1 year

Fencing Inspection and Repairs

1 year

Tide Gate, Drains and Outlets Inspection and Repairs

1 year

Public Stakeholder Coordination

1 year

Water Quality Monitoring

1 year

Tidal Range Monitoring

1 year

Breeding and Wintering Bird Monitoring

1 year

Topographic/Bathymetric Monitoring Surveys

2-3 years

Biological Species Inventory

5-6 years

Watershed Mapping

5-6 years

Vegetation Monitoring and Mapping

5-6 years

CRAM Assessments

5-6 years

Eelgrass Monitoring

5-6 years

Benthic Invertebrate Monitoring

5-6 years

Tidal Channel Dredging

10-15 years*

Tidal Channel Dredging Environmental Assessment

10-15 years*

Water Quality Emergency Response

As needed

 

 *Frequency of tidal channel dredging tasks are dependent on the results of the topographic, bathymetric, and tidal monitoring surveys.  Current trends show dredging will be required every 10-15 years.

Note: All maintenance and monitoring activities are to be performed between 16 September to 14 February to avoid nesting season with the exception of eelgrass monitoring, breeding bird monitoring, tidal range monitoring and fence maintenance. Per the Corps of Engineers Maintenance Plan, eelgrass monitoring will occur during the peak growth season in spring and summer months. Tidal range monitoring occurs in July to larger tides and limited rainfall. To avoid habitat damage due to trespassing, fencing may occur during nesting season in the presence of a trained ornithologist. 

Upcoming Activities

Activity

Date(s)

Tidal Water Level Monitoring

Completed in December 2023

Environmental Assessment Public Review

Completed in January 2024