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Introduction

OWENS LAKE: A SOURCE OF DUST EMISSIONS

Owens Lake is located in eastern-central California at the southern end of the Owens Valley. During the late 1800s, prior to water diversions, Owens Lake was a closed-basin saline lake covering about 100 square miles, with a maximum depth of approximately 50 feet. Beginning in 1913, water was diverted from the Owens River (the primary inflow to the lake) into the Los Angeles Aqueduct for the city of Los Angeles. The diversion caused large portions of the Owens Lake bed to dry out, shrinking the lake to less than one-third its former area and leaving a shallow hypersaline brine dominated by salts of sodium carbonate and sodium sulfate (Mihevc et al., 1997). Although many salt flats and lakes (e.g., Bonneville Salt Flats, Salar de Uuyni) have hard and stable salt crusts dominated by sodium chloride, the sodium carbonate and sodium sulfate dominated mineral composition of Owens Lake brines resulted in easily erodible dry saline silty soils and fragile salt crusts. This phenomenon is also observed at other saline lakes undergoing desiccation such as the Salton Sea (California), Lake Urmia (Iran), and the Aral Sea (Kazakhstan and Uzbekistan). The resulting dry areas of Owens Lake bed contained several areas with sandy sediments, especially near the Owens River delta. These sandy sediments can abrade dust from weak crusts and soil aggregates during wind events, compounding the erodibility of the lakebed. The dry lakebed produced large amounts of airborne dust under high wind conditions, resulting in the highest concentrations of airborne particulate matter smaller than 10 micrometers (µm; PM₁₀) in the country (CARB, 2016) (see Figure 1-1).

Legal and Regulatory History of Air Pollution Control

Airborne particulate matter is one of six criteria pollutants regulated under the U.S. Environmental Protection Agency (EPA) National Ambient Air Quality Standards (NAAQS). In addition, the state of California sets ambient air quality standards (CAAQS).¹

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¹ Attainment of the NAAQS has precedence over attainment of the CAAQS due to penalties for failure to meet NAAQS deadlines. California law does not require that CAAQS be met by specified dates. Instead, the law requires incremental progress toward attainment (CARB, 2020).

Two size-categories of airborne particulate matter are currently regulated by EPA and the state of California: PM₁₀ and PM_2.5 (particles 10 µm and 2.5 µm or smaller in aerodynamic diameter, respectively) (CARB, 2019; EPA, 2016). EPA’s Integrated Science Assessment for Particulate Matter evaluates and synthesizes research findings on the public health effects and other effects (e.g., reduced atmospheric visibility) associated with airborne PM₁₀ and PM_2.5 (EPA, 2019a). As discussed below, this report is focused on PM₁₀. The NAAQS for PM₁₀ is 150 µg/m³, with an averaging time of 24 hours. The CAAQS for PM₁₀ is 50 µg/m³, with an averaging time of 24 hours and 20 µg/m³, with an averaging time of 1 year.² States have the primary responsibility to prepare a State Implementation Plan (SIP) for achieving and maintaining the NAAQS within each air quality control region within the state. The SIP establishes emission limits and other control measures that are designed to achieve NAAQS attainment in nonattainment regions.

In 1987, EPA designated the southern Owens Valley (known as the Owens Valley Planning Area or OVPA), where Owens Lake is situated, as being in nonattainment of the 24-hour-average PM₁₀ NAAQS (see Figure 1-2). The area also has been designated by the state of California as being in nonattainment of the corresponding state standards. The California Air Resources Board delegated responsibility for developing and enforcing

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² Air quality data statistics for PM_10, PM_2.5, and other pollutants throughout the state of California are available at: https://www.arb.ca.gov/adam/trends/trends1.php (accessed January 28, 2020).

the SIP to the Great Basin Unified Air Pollution Control District (hereafter, the District) for areas in the District’s jurisdiction. The District determined that the Owens Lake bed should be controlled as an anthropogenic source of PM₁₀ because the Los Angeles Aqueduct diverted water sources that historically supplied the lake. The Los Angeles Department of Water and Power (LADWP) was deemed legally responsible for controlling particulate emissions from the dry lakebed.³ The Owens Lake bed is defined in regulations as the area below 3,600 feet above mean sea level. The current ordinary high water elevation is about 3,554 feet (GBUAPCD, 2016a).

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³ Legal requirements and enforcement mechanisms include District Governing Board Order #160413-01 (Requiring the City of Los Angeles to Undertake Measures to Control PM₁₀ Emissions from the Dried Bed of Owens Lake), District Rule 433 (Control of Particulate Emissions At Owens Lake), California Health and Safety Code 42316 (District may require the City of Los Angeles to undertake reasonable measure to mitigate the air quality impacts of its activities in the production, diversion, storage, or conveyance of water. . .).

Dust Management at Owens Lake

In the 1998 SIP for the OVPA (GBUAPCD, 1998), the District outlined plans for implementing dust control measures (DCMs) to reduce PM₁₀ emissions on 16.5 square miles of the lakebed, and LADWP began construction in 2000 (see Figure 1-3). The District subsequently developed SIPs in 2003, 2008, and 2016 to require DCMs over larger areas of the lakebed in order to attain the NAAQS for PM₁₀ (GBUAPCD, 2003, 2008, 2016a).

As of April 2019, 48.9 square miles of lakebed (below the regulatory shoreline elevation of 3,600 feet and at or above Owens Lake’s ordinary high water elevation of 3,553.55 feet) had been ordered for PM₁₀ control.⁴

DCMs can range widely in the type of control and their effectiveness. For a serious nonattainment area with fugitive dust sources, Best Available Control Measures (BACMs) are required and defined by the Clean Air Act. In the context of the Owens Valley, BACMs are defined as “best available control measures designed to reduce PM₁₀ emissions to Control Efficiency (CE) levels . . . through compliance with [specific] performance standards.” Control efficiency levels are established as 99 percent reduction in PM₁₀ emissions for the regulated areas on the lakebed.⁵ As of April 2019, BACMs were used across 46.6 square miles of the lakebed to control PM₁₀ emissions (see Figure 1-4).

Three categories of BACMs have been approved for use on the lake: shallow flooding, managed vegetation, and gravel (see Box 1-1). These BACMs were determined from a research and testing program at Owens Lake starting in 1980 and overseen by the District. These BACMs were designated by the District in the 1994 and 1998 SIPs and were approved by EPA in 2000. Subsequently, several modifications to the BACMs have been adopted; for example, approved modifications to the Shallow Flooding BACM are Tillage with Shallow Flooding Backup, Brine with Shallow Flooding Backup, and Dynamic Water Management. Table 1-1 summarizes the areas controlled with each BACM as of April 2019. The Shallow Flooding BACM is, by far, the most widespread DCM, by surface area, applied at Owens Lake (see also Figure 1-4). See Chapter 4 for additional discussion of these BACMs and other DCMs.

In specific areas of the lakebed, beginning in 2008, the District permitted the use of minimum dust control efficiency BACMs to reduce water use or address environmental concerns. In these areas, required control efficiency may be less than 99 percent, if approved by the District. The specific control efficiency targets for each individual dust control area are set based on the levels of control necessary to prevent exceedances of the NAAQS, as determined by air quality modeling (GBUAPCB, 2008, 2016a). As of 2019, 0.9 square miles are controlled with minimum dust control efficiency BACMs (see Table 1-1). An example is the use of sand fences on approximately 0.4 square miles toward the southern end of the lakebed. Scattered among the areas that have been ordered for dust control are several environmentally sensitive areas (1.2 square miles total) that remain uncontrolled; such areas have been deferred by the District because of the presence of eligible cultural resources.

Although most OVPA PM₁₀ control efforts have focused on the ordered dust control areas on the Owens Lake bed, the District has implemented off-lake dust control measures

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⁴ Although the regulatory text in Rule 433, Board Order #160413-01, and GBUAPCD (2018) state 48.6 square miles of dust control, the area resulting from the coordinates listed and ordered in the same documents totals 48.9 square miles. Thus the District considers the total ordered area to be 48.9 square miles (Logan, 2020).

⁵ District Rule 433, Control of Particulate Emissions at Owens Lake, adopted 04/13/2016. See https://ww3.arb.ca.gov/drdb/gbu/curhtml/r433.pdf (accessed January 28, 2020).

TABLE 1-1 Dust Control Status as of April 2019

^a In the 2018/2019 water year, 10.5 square miles of this area was operated for dynamic water management.

^b Includes environmentally sensitive areas, such as areas that have been deferred because of the presence of eligible cultural resources meeting requirements per the District order.

SOURCE: Logan, 2019a; Valenzuela, 2019a.

(beyond the regulatory shoreline) at the Keeler Dunes.⁶ The project uses straw bales and planted shrubs as dust control measures (see Chapter 4 for more details).

As of 2019, LADWP estimates that $2.1 billion has been spent on managing dust at Owens Lake. That estimated cost consists of capital costs to construct large dust control infrastructure on 47.8 square miles (55 percent), operating and maintenance costs (18 percent), water use (21 percent), and regulatory fees (6 percent) (Valenzuela, 2019a).⁷

Many of the BACMs defined in the SIPs and implemented in the ordered dust control areas involve the use of water. The quantity of freshwater used for current dust control activity is estimated to be approximately 60,000 acre-ft/year, with year-to-year variability from approximately 45,000 to 70,000 acre-ft/year (Agahi, 2019). Since 2007, annual water use for dust control represents roughly 30 percent of available LADWP freshwater supplies at Owens Lake,⁸ with an annual range of 17 to 51 percent. Long-term water availability to southern California is projected to decline with climate change and changing water allocations from the Colorado River under newly implemented drought contingency plans (P.L.116-14). Modifications of BACM requirements to conserve water use saved an average of about 22,000 acre-ft/year from 2014 through 2016 compared to the average water use from 2011 through 2013 (GBUAPCD, 2018). More-detailed analyses of the water use associated with various DCMs are provided in Chapter 3.

CHALLENGES

The tension between water use and dust control in the OVPA represents a serious challenge to meeting the NAAQS for PM₁₀. LADWP and the District have agreed through a Stipulated Judgment to move toward less reliance on shallow flooding for dust control and to investigate new and refined DCMs to reduce overall water demand.⁹ The Judgment states, “New dust control measures should be waterless where feasible. Where not feasible, new dust control measures should be water neutral by offsetting any new or increased water use with water savings elsewhere on the lakebed.” New or refined waterless measures could include engineered roughness, soil binders, and improved tillage strategies. In addition, vegetation, such as playa scrub species, could provide dust control as well as habitat, positive aesthetics, and protection of cultural resources, with minimal long-term irrigation needs, particularly around the lake edges.

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⁶ Under the 2013 Stipulated Order of Abatement, LADWP contributed $10 million as a “public benefit contribution” to the District for PM₁₀ control at the Keeler Dunes. In return, LADWP would be released “from any and all liability for dust emissions, regardless of origin, from the Keeler Dunes and other dune areas in the vicinity of Owens Lake” (GBUAPCB, 2016a).

⁷ See GBUAPCD (2016a, p. 58) for additional information on costs.

⁸ Available water is assumed to be the sum of LADWP exports in the Los Angeles Aqueduct and Owens Lake freshwater use for dust control. See Chapter 3.

⁹ Stipulated Judgment in the matter of the City of Los Angeles v. the California Air Resources Board et al. Superior Court of the State of California, County of Sacramento. Case No. 34-2013-80001451-CU-WM-GDS. Approved by the court on December 30, 2014. See https://gbuapcd.org/Docs/District/AirQualityPlans/SIP_Archive/2014_Stipulated_Judgment_20141230.pdf (accessed January 28, 2020).

Implementation of DCMs is also challenged by the needs to maintain ecological habitat and mitigate impacts to cultural resources and other environmental resources. Currently, approximately 277 acres are excluded from on-site DCMs because they have been identified as Eligible Cultural Resources (ECRs) (GBUAPCD, 2016a, p. 49). If adjacent DCMs are insufficient to control PM₁₀ emissions from these areas, dust control may be ordered for any ECR area determined to have caused or contributed to an exceedance of air quality standards. Representatives of Native American tribes in Owens Valley have voiced concerns about the land disturbance (which can destroy cultural artifacts and disrupt the natural land forms that are culturally important), road building (which not only involves land disturbance but also increases access to looters), and unnatural aesthetics of some of the managed areas at Owens Lake, as well as about protection of historical and archeological resources (Bancroft, 2013).

The large expanses of shallow flooding combined with natural wetlands provide attractive habitat for migratory and nesting birds. The area attracts thousands of sandpipers, ducks, and other shorebirds, and it provides breeding habitat for the Snowy Plover, Yellow-headed Blackbird, and Long-billed Curlew.¹⁰ Owens Lake has been designated an “Important Bird Area” by the National Audubon Society, and efforts to reduce water use in dust mitigation will likely impact existing habitat. The habitats of Owens Lake are discussed in detail in Chapter 3.

Other challenges that affect dust management decisions at Owens Lake include the long-term durability and reliability of the DCMs, economic costs, and energy use. Factors that affect the durability of DCMs include the corrosive nature of the soils, flooding from snow melt, and the uncertain long-term availability of water due to climate change.

STATEMENT OF TASK

To help address these ongoing challenges, LADWP and the District agreed under the 2014 Stipulated Judgment to contract with the National Academies of Sciences, Engineering, and Medicine (NASEM) to establish the Owens Lake Scientific Advisory Panel (OLSAP). According to the 2014 Stipulated Judgment,

[t]he purpose of the OLSAP is to evaluate, assess, and provide ongoing advice on the reduction of airborne dust in the Owens Valley. The Panel will review scientific and technical issues related to the research, development and implementation of waterless and low water use BACM, and other approaches to reduce dust in the Owens Valley. The Parties intend for the Panel to foster communication and understanding on the scientific and technical approaches and become a vehicle for increased cooperation and collaboration between the District and the City in balancing the requirement to meet air quality standards and conserve water (p. 13).

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¹⁰ See https://www.audubon.org/important-bird-areas/owens-lake (accessed January 28, 2020).

As indicated in the 2014 Stipulated Judgment, the panel’s first task is to

[e]valuate the effectiveness of alternative dust control methodologies for their degree of PM₁₀ reduction at the Owens Lakebed and to reduce use of water in controlling dust emissions from the dried lakebed. The evaluation should consider associated energy, environmental and economic impacts, and assess the durability and reliability of such control methods (p. 14).

In response to that request, NASEM established the OLSAP to carry out the first task. (See Appendix A for biographical sketches of the panel members.) In interpreting its charge and its overarching purpose, the panel considered the term effectiveness to mean the level of PM₁₀ emission control (e.g., 99 percent) achieved by a DCM. That definition is consistent with the meaning of control effectiveness (or control efficiency) used in the SIP (GBUAPCD, 2016a). The panel considered the reliability of the DCMs under current and potential future extreme weather events under a changing climate.

The panel also determined that its charge included consideration of both lakebed (on-lake) and off-lake sources of PM₁₀ that are adjacent to lakebed dust control areas. This interpretation is based on the recognition that PM₁₀ reduction at the Owens Lake bed will result from a variety of sources on the lakebed and that sediment mobilized from the lakebed may have been transported to off-lake areas that are now PM₁₀ sources. In addition, the District has concluded that PM₁₀ emissions from off-lake areas continue to pose the largest challenge for attainment of PM₁₀ air quality standards within the OVPA. According to monitoring and modeling analyses conducted by the District, emissions from off-lake sources more than 2 kilometers (1.2 miles) from the lakebed do not influence attainment (GBUAPCD, 2016a). Therefore, although the panel primarily focused on lakebed sources of PM₁₀, it also evaluated DCMs that could be effective for nearby sources. This approach is consistent with the overall purpose of OLSAP to examine airborne dust in the Owens Valley. However, for this task the panel’s evaluation of DCMs did not consider application to potential dust sources that are distant from the Owens Lake bed.

The panel’s interpretation of its charge was informed by the definition of environment found in The California Environmental Quality Act (CEQA):

“Environment” means the physical conditions which exist within the area which will be affected by a proposed project including land, air, water, minerals, flora, fauna, ambient noise, and objects of historical or aesthetic significance. The area involved shall be the area in which significant effects would occur either directly or indirectly as a result of the project. The “environment” includes both natural and man-made conditions.¹¹

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¹¹ Title 14. California Code of Regulations, Chapter 3. Guidelines for Implementation of the California Environmental Quality Act, Section 15360. Environment. Available at http://www.resources.ca.gov/ceqa/guidelines/art20.html (accessed January 28, 2020).

Therefore, the panel interpreted its charge to include evaluation of the potential effects of DCMs on the cultural resources of Native American tribes in the Owens Valley. Based on priorities expressed in public statements and information available in the public record, the committee focused its assessment of the effects of DCM alternatives on cultural resources on the likelihood of land disturbance, which could harm archaeological resources, and effects on habitat and natural aesthetics, which are also valued cultural resources.

In choosing the types of DCMs to evaluate, the panel combined BACMs and other DCMs under the general term of alternative dust control methodologies. It did not evaluate the alternative dust mitigation strategy of restoring the lake by modifying the amount of water diverted to Los Angeles and allowing the lake to refill and reach a steady state. Evaluation of that strategy falls outside the committee’s charge, which is focused on DCMs that reduce the use of water to control dust emissions for the dried lakebed, and would require substantial effort to gather and analyze the necessary data.

This report reflects the consensus of the panel members, based on briefings from agencies, organizations, and individuals received during the public sessions of the May and July 2019 meetings, three Web conferences in July and August 2019, and three field-trip sessions at Owens Lake in July 2019, including one field-trip session focused on Native American perspectives and concerns (see Appendix B); documents provided to the panel; relevant scientific literature; and the knowledge and experience of the panel members in their fields of expertise.

ORGANIZATION OF THE REPORT

Chapter 2 discusses the wind erosion processes that lead to fugitive dust emissions, air monitoring systems in use at Owens Lake, monitoring data trends, and air quality modeling. Chapter 3 discusses key contextual factors for evaluating DCMs, including hydrology and water resources; areas on the Owens Lake bed that are culturally significant to Native American tribes; habitats; and mineral resources. Chapter 4 assesses 15 DCMs that represent a range of mitigation approaches that are either currently applied at Owens Lake or at various stages of development. Chapter 5 outlines an integrated systems approach to dust control for meeting current and future challenges.

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