Constructed, designed, and recently identified field studies will cover over 5,300 acres of high-priority playa. Surface roughening continues to be recommended for all field study areas with suitable playa and soil conditions. This dust control measure is effective, waterless, and can be quickly implemented. However, it is unsuitable for areas with predominantly coarse-grained soils due to the rapid degradation of ridges in sandy soils. For these areas, vegetation is recommended. For most field studies, a combination of surface roughening and vegetation is recommended based on site-specific suitability.
Surface roughening is done with a tractor and bull plow
Field study areas account for nearly 43% of the total yearly emissions (192 of the 447 tons/year of PM10) identified in the 2017/2018 Emissions Estimate. When considered together with projects planned by other stakeholders, the acreage increases to approximately 7,750 acres of dust control and habitat projects. These areas account for over 51% of the total yearly playa emissions (228 of the 447 tons of PM10).
This map shows the locations of existing and recommended field study areas. Implementation of the field studies is subject to funding authorized by the Quantification Settlement Agreement Joint Powers Authority.
The Salton Sea has and continues to be an important stop-over for millions of migratory birds moving along the Pacific Flyway. As the transfer of conserved water ramps up, increased salinity is and will continue to accelerate changes to the food web, significantly reducing the quality and availability of habitat for these migratory birds. IID and other stakeholders are targeting critical habitat creation and enhancement projects to minimize impacts to migratory birds and other important waterfowl, and to provide air quality benefits by protecting the playa surface. For example, the State of California’s Salton Sea Management Plan, Phase 1 (10-Year Plan), was developed to expedite implementation of habitat and dust mitigation projects. The 10-Year Plan defines acreage goals for habitat and dust mitigation projects annually between 2019 and 2029.
Currently planned stakeholder projects include the California Natural Resources Agency’s Species Conservation Habitat Project, the US Fish and Wildlife Service’s Red Hill Bay Project, and the Torres Martinez Wetland Project. In addition, the National Audubon Society is working to quickly develop projects that provide immediate habitat benefits while balancing the goals of both habitat creation and proactive dust control. These targeted projects are needed to “bridge the gap” while large-scale habitat is designed and constructed by the State of California (implementation planned in 2023 at the earliest). Prior to large- scale implementation in 2023, playa exposure and salinity are projected to increase to over 48,000 acres and 90,000 milligrams per liter, respectively.
Development of dust control performance monitoring techniques and appropriate maintenance criteria are another main focus of the Air Quality Mitigation Program. These are essential for ensuring adequate surface stabilization over time. Two approaches for monitoring dust control performance include ground-based environmental sensors and remote sensing. Performance monitoring data are most informative when they can be readily compared to the original design criteria developed for the site. These design criteria originate from the Single-event Wind Erosion Evaluation Program (SWEEP). SWEEP is a physically-based model used to design site-specific dust control measures based on soils, vegetation, surface roughness, and local 24-hour high wind event attributes. While environmental sensors provide more direct measures of windblown sand flux, they are limited in spatial extent and are subject to bias introduced in the sampling design. On the other hand, remote sensing provides a spatially comprehensive measurement, thus removing sampling bias, and when coupled with a physically-based model (e.g., SWEEP), sand flux can be accurately estimated.
Ground-based sensors, including Cox Sand Catchers, Sensits, and BGI PQ200 ambient air particulate samplers, are used to measure real-time horizontal sand fluxes. These sensors can be placed upwind of dust control areas to provide a baseline of particle movement, mid-area to quantify reduction of the baseline, and downwind to assess the full impact of the treatment. Collected data are useful to validate SWEEP modeling, assess the performance of dust control measures, and guide planning and future implementation of proactive dust control.
The Cox Sand Catcher is a positionally-fixed vertical tube that physically traps saltating particles at six inches above the soil surface (small orange tube on the left). Sensits use a piezoelectric crystal to measure saltating particles that strike the sensor surface. Like the CSC, the Sensit is positionally fixed, but it has the advantage of providing highly-resolved data at specified logging intervals. A data logger with a solar panel collects data from the site.
After dust control measure implementation, vegetation and surface roughness can be quantified using remote-sensing -based methods (e.g. Detection And Ranging ([LiDAR]), evaluated within SWEEP, and used to understand dust control performance relative to the design criteria. This approach is:
In 2018, a remote-sensing-based monitoring technique was developed using ultra-dense LiDAR point clouds. A series of algorithms were developed to translate the LiDAR data into surface roughness attributes used in the SWEEP model. This includes ridge height, ridge spacing, surface roughness length, and random roughness. Surface roughness conditions can now be assessed using LiDAR each quarter following dust control measure installation and compared to the design criteria. This allows dust control maintenance activities to occur, such as retilling, and for the restoration of roughness that has eroded over time.
There are several challenges associated with air quality mitigation at the Salton Sea. In particular, the western side of the Salton Sea is responsible for the majority (63%) of playa emissions and will be the most challenging to control.
There is no buffer to slow high westerly winds before they reach the playa. The adjacent desert area provides an unlimited supply of sediments that blow onto the playa during high-velocity winds. In many locations, sand dunes and sand sheets are advancing eastward toward exposed playa. For example, aeolian sand from dunes and sand sheets adjacent to the Naval Test Base continue to migrate onto the playa, increasing estimated playa emissions by approximately five times compared to adjacent playa areas without evidence of sand migration. In addition, fluvial deposition and migration of sand down dry washes and alluvial fans continue to occur and increase emissions.
There is limited suitability for surface roughening and limited water resources for vegetation establishment on the western side. Soils here were deposited primarily from alluvial flow, and soil core data indicate much of this area has coarse-textured soils. Although there are many small watersheds, surface flow varies significantly based on precipitation and is not reliable for vegetation establishment. Groundwater and use of mobile reservoirs are currently being evaluated as an alternative irrigation source.