Effectiveness and Impacts of Dust Control Measures for Owens Lake (2020) / Chapter Skim
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4 Evaluations of Dust Control Measures
4 Evaluations of Dust Control Measures
Pages 71-130
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From page 71... ...
EXISTING BACMs Three BACMs have been approved for the Owens Lake bed: shallow flooding, gravel, and managed vegetation. Three modifications to the shallow flooding BACM are also discussed in this section: dynamic water management, brine with shallow flooding backup, and tillage with shallow flooding backup.
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From page 72... ...
vegetation Brine with 99% 0 (but $24 M; $0.23 M Low value High land Months to Most suitable in Shallow requires 20-yr life disturbance 1 year low elevations Flooding backup) Backup Shallow Flooding BACM (3.8 mi2)
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From page 73... ...
abundant disturbance 92% obs. at plants lifespan Keeler Dune unknown Artificial Roughness: Depends on 0 ~$45 M; ND; expected Moderate; Potentially Immediate Suitable to all Solid Engineered density and lifespan to be low regionally low land locations geometry; unknown abundant disturbance 90% observed in field test Artificial Roughness: Unknown; 0 ND; lifespan ND Moderate; Potentially Immediate Suitable to all Porous Natural dependent unknown regionally low land locations on density abundant disturbance and geometry Artificial Roughness: Unknown; 0 ~$64 M; ND; expected Moderate; Potentially Immediate Suitable to all Porous Engineered dependent lifespan to be low regionally low land locations on density unknown abundant disturbance and geometry Shrubs (with Depends on Leach: 0.1–8 ND ND; expected Moderate; Potentially 5–10 yrs Most suitable modified % cover)
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From page 74... ...
. Shallow flooding area without dynamic water management reported here as the total minus the area of dynamic water management in the 2019 water year, although these operations can vary from year to year.
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From page 75... ...
Shallow Flooding Shallow flooding is the most widely used BACM at Owens Lake (see Figure 1-4 and Table 1-1)
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From page 76... ...
and fitted curve documenting control efficiency (based on both PM10 and sand flux measurements) as a function of shallow flooding c overage, from which the 75 percent wetted criteria was determined.
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From page 77... ...
of a mix of stable qualifying surfaces: 1. Standing water or hydrologically saturated surface, 2. Evaporite salt deposit with a minimum thickness of 1.5 cm, and 3. Capillary crust with a min thickness of 10 cm and <1/3 of minimum required total cover (24% or 25%) Reflood when <60%; Maintenance required if >60% but less than required or >1/3 capillarya,b IPET Mitigation required/reflood when visible dust emissions occur when operated at reference test heighta,b Shallow Flooding BACM Dust Plume Obs.
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From page 78... ...
. b District Rule 433, Control of Particulate Emissions At Owens Lake, adopted March 13, 2016.
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From page 79... ...
. Practical Considerations The shallow flooding BACM can achieve full performance following construction and upon reaching the required surface wetness coverage.
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From page 80... ...
Because of the land disturbance associated with surface leveling (to improve water spreading efficiency and minimize water needed to cover the surface) and the amount of infrastructure required, the shallow flooding BACM is not conducive to use on environmentally sensitive areas of the lake.
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From page 81... ...
In addition, more work is needed to understand the linkage between shallow flooding acreage, depth, salinity, food web production, and bird population sizes. For example, brine flies (and brine shrimp, to a lesser extent at Owens Lake)
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From page 82... ...
In 2018 and 2019, LADWP reported an average water use of 2.6 ft over the areas in which dynamic water management was applied, which is slightly less than the reported water use of 2.7-3.2 ft for the shallow flooding BACM. LADWP reports that, on average, dynamic water management reduced water use at Owens Lake by 1,750 acre-ft/year (Valenzuela, 2019b)
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From page 83... ...
Brine with Shallow Flooding BACM Backup Owens Lake brines are typically considered an alkaline sodium carbonate-sulfatechloride brine, following the model of Hardie and Eungster in which sodium is the dominant cation (Friedman et al., 1997)
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From page 84... ...
The District reported that no visible dust plumes originated from brine BACM between 2012 and 2015, during a multiyear drought. Until more data are collected during a broader range of precipitation conditions, shallow flooding backup continues to be required for the brine BACM because salt mineral crusts can generate emissive salts as they transition between hydrated and dehydrated states (GBUAPCD, 2016b)
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From page 85... ...
The BACM uses no freshwater during construction and, in theory, during operation. However, a source of water for flooding, such as tailwater from a shallow flooding cell, must be available if the surface becomes emissive and the shallow flooding BACM backup is required.
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From page 86... ...
. Cost The construction cost of the brine BACM with shallow flooding backup is $24 million/ square mile, which is lower than the shallow flooding BACM.
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From page 87... ...
Tillage with Shallow Flooding BACM Backup Tillage with the shallow flooding BACM backup was approved as a modification to the shallow flooding BACM in 2014.6 Tillage controls soil erosion by wind and fugitive dust emissions in several ways. Tillage, as practiced on the Owens Lake bed, creates oriented beds and large surface aggregates (termed oriented and random surface roughness, respectively; see Figure 4-5)
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From page 88... ...
In addition, measurements, including the induced particle emission test and sand flux, are required to assess the dust control performance. If the control efficiency measurements show insufficient dust control, the area is flooded and tilled again to renew the surface roughness.7 7 District Rule 433, Control of Particulate Emissions At Owens Lake, adopted March 13, 2016.
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From page 89... ...
. Studies at Owens Lake showed that when the performance criteria were maintained, tillage generally resulted in de minimis levels of sand flux and PM10,8 which was considered equivalent to a control efficiency of 99 percent or greater sand flux (Air Sciences, Inc., 2015)
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From page 90... ...
Water may also be needed for shallow flooding to control emissions if the tillage fails. If tillage renewal immediately follows the rainy season, it is possible that no water additions would be required.
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From page 91... ...
. FIGURE 4-6 Managed vegetation BACM on Owens Lake.
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. The current vegetation cover requirements for this BACM are derived from a study of the largest area of managed vegetation on Owens Lake -- 2,100 acres in the southern end of the lake.
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From page 93... ...
. The sites with long-term vegetation cover declines are usually not suitable for managed vegetation, or soil salinity was not sufficiently remediated prior to planting (Scheidlinger, 2008b)
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From page 94... ...
Of the projects implemented on Owens Lake, most managed vegetation BACMs were located on mudflat and saltcrust areas, which are more difficult to leach and maintain salinity. This likely skews existing water and cost data to more expensive, more long-term maintenance scenarios, compared to managed vegetation efforts focused on sandy areas of the lake that have been leached with freshwater from shallow flooding, or areas closer to the regulatory shoreline, which tend to be sandy, less saline, and with deeper groundwater.
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From page 95... ...
As demonstrated across a suite of trials at Owens Lake, sandy sites tend to be easier to reclaim and maintain than clay-rich sites (Scheidlinger, 2008b)
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From page 96... ...
EFFECTIVENESS AND IMPACTS OF DUST CONTROL MEASURES FOR OWENS LAKE FIGURE 4-7 Soil texture map.
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From page 97... ...
. In fact, managed vegetation areas on Owens Lake are used to fulfill mitigation requirements due to habitat destruction in other parts of the lake (GBUAPCD, 2016a)
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From page 98... ...
the historic shoreline and in the northern portion of the lakebed may, over time, become sufficiently leached and naturally drained that they will not need a managed drainage system. Cost To implement the sprinkler approach to managed vegetation in Phases 7a, 9, and 10 of Owens Lake dust control, establishment of the BACM required $36 million/square mile in capital costs, while the drip irrigation–based managed vegetation farm initially cost $20 million/square mile.
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From page 99... ...
LADWP estimates that this infrastructure will last 20 years, and will require complete reestablishment costs at that time. Systemwide Considerations Long-term management of groundwater levels and salinity are the most critical factors for durability and reliability of the managed vegetation BACM.
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From page 100... ...
Other pressing questions for Owens Lake include where are the most appropriate areas for specific plant types and communities used in managed vegetation BACMs, how large must these vegetated areas be to minimize required maintenance, and how are they affected by adjacent dust control measures? The ways in which natural spatial and temporal variability in vegetation impacts dust control is another important consideration, because the strict regulations of time frames and threshold percent vegetation cover values are not always realistic in an ecological system, where variability is the norm but ecosystem services can be maintained despite this variability.
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From page 101... ...
. Gravel protects the bare ground underneath it against wind erosion by substantially reducing the capillary rise of saline groundwater and salt and crust formation.
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From page 102... ...
If raking cannot restore target control efficiencies, additional gravel can be brought to the site. Gravel as a DCM is expected to last for decades; it is estimated that the gravel used during phase 7a (total area of 1.5 square miles)
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From page 103... ...
OTHER NON-BACM DUST CONTROL MEASURES The panel reviewed nine other DCMs that show potential for use in dust control on the Owens Lake bed. Some of the measures also show potential for control of off-lake sources.
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From page 104... ...
. Performance The SFWCRFT examined the dust control at different wetted percentages up to 75 percent wetted area at four locations on the Owens Lake bed and LADWP has proposed additional testing (LADWP, 2019b)
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From page 105... ...
These amounts represent water savings compared to 3 ft/year for shallow flooding with laterals and 2.68 ft/year for shallow flooding with sprinklers. Although these data are limited, they suggest water savings may be feasible.
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From page 106... ...
The infrastructure costs for precision surface wetting could be expected to decrease by 13 percent for each 10 percent reduction below 75 percent wetted surface coverage. Operating costs, estimated at $340,000/year based on the costs of shallow flooding with sprinklers, would consist of monitoring and maintaining the water distribution infrastructure (Valenzuela, 2019b)
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From page 107... ...
Use of dynamic operations would necessitate alternate, real-time performance criteria, such as cameras and low-cost PM10 sensors along the DCM boundary. Additional research could examine the use of precision surface wetting to build surface evaporite crusts that might eventually control dust emissions with less or no water use.
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From page 108... ...
The only type of artificial roughness that has been implemented at a large scale in the Owens Lake area is in the Keeler Dunes area, where straw bales are used as solid natural roughness elements (see Box 4-2 and Figure 4-10)
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From page 109... ...
FIGURE A Use of solid natural roughness elements at the Keeler Dunes. SOURCE: Photo courtesy of David Allen, panel member.
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From page 110... ...
, though the distance over which control efficiency is obtained depends on the density and distribution of roughness elements (Gillies et al., 2017, 2018a)
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From page 111... ...
An additional benefit of solid natural roughness elements as a DCM is that they could be deployed rapidly, and reversibly, as an emergency measure should a BACM fail. The material from which the roughness elements are made would determine their longevity in the Owens Lake environment.
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From page 112... ...
Engineered roughness elements would have higher energy use associated with their production compared to natural roughness. Cost The capital costs of the Keeler Dunes project were $52 million/square mile with plantings included and $9 million/square mile without.
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From page 113... ...
The current vegetation cover BACM requires a minimum of 37 percent vegetation cover, with additional spatial distribution requirements, to produce an estimated 99 percent dust control efficiency. The original experiments and existing vegetation plantings for dust control on Owens Lake use saltgrass.
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From page 114... ...
) would have approximately 25 percent of the area with greater than 85 percent control efficiency, and a square 10-ha area would have approximately 92 percent of the area with greater than 85 percent control efficiency (85 percent was the revised target control efficiency for this project)
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From page 115... ...
Information Needs to Inform Decision Making Large, established, relatively dense shrub stands could reduce aeolian transport and dust emission from the Owens Lake bed, but their potential to attain 95 or 99 percent control efficiency has yet to be established. Additional research is needed to document the vegetated cover associated with target control efficiencies using shrubs.
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From page 116... ...
However, some simple modeling using the Okin model and 5-minute winds from North Beach sheds light on the amount of vegetation cover that may be needed for 99 percent control efficiency. Using simple assumptions about vegetation size (0.5 m diameter)
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From page 117... ...
In a managed vegetation BACM, irrigation may be able to increase vegetation cover (and size) beyond the threshold required for 99 percent control efficiency.
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From page 118... ...
Also similar to gravel, under extreme flooding, cobbles could be displaced, exposing the surface underneath. Environmental Implications One noteworthy difference between gravel and cobbles is that the non-uniform spacing between cobbles allows for growth of some vegetation by trapping windblown soil and seeds (see Figure 4-12)
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From page 119... ...
Thus, beyond directly protecting the soil surface from wind erosion, cobbles can serve as sites of native vegetation regeneration requiring no added water. Because of their uneven surface, cobbles provide a better habitat for nesting shorebirds when placed adjacent to shallow flooding areas, and they provide shelter for other non-aquatic species, especially if vegetation regeneration has occurred.
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From page 120... ...
Performance In the 1990s, modeling analyses examined the potential for sand fences to provide target control efficiencies at Owens Lake (Ono, 1996; CH2M Hill, 2000)
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From page 121... ...
At Owens Lake, creation of a gap at the base of the fence and burrows and passages at intermediate locations in the fence has helped alleviate this problem. Nevertheless, sand fences should not be used in core wildlife areas.
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From page 122... ...
FIGURE 4-14 Solar panel testing installed on gravel at Owens Lake using pile-driven mounts (top) and squat ballast mounts (bottom)
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From page 123... ...
Practical Considerations Solar panels have the potential to beneficially use the open space over the lake, providing electricity, while also controlling dust emissions. The Owens Lake area has a high potential for producing solar power (Bolinger and Seel, 2018)
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From page 124... ...
Installation lifetimes for utility-scale PV farms are about 25-40 years.16 A more comprehensive economic evaluation of the actual likely capital and operating costs, as well as potential benefits, including how this fits into California's renewable energy plans, would inform future evaluation of the use of solar panel farms as a potential BACM when considering aesthetics and other factors. Information Needs to Inform Decision Making Knowledge of how solar panels fit within an integrated management plan for the Owens Lake area would benefit from more detailed information on control effectiveness (without gravel)
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From page 125... ...
Examination of how other large-scale installations have impacted local ecology might also inform potential ecological benefits and disbenefits in a similar application to the Owens Lake area. DUST CONTROL MEASURES NOT EVALUATED IN DETAIL Two DCMs were not evaluated in detail: chemical stabilizers and biocrusts.
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From page 126... ...
, area of standing water or surface-saturated soil (shallow flooding BACM) , vegetation cover (managed vegetation BACM)
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From page 127... ...
Upon receipt of permits and leases from relevant land owners and agencies, including the District, the California Department of Fish and Wildlife, the Lahontan Regional Water 17 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. See https://gbuapcd.org/Docs/District/AirQualityPlans/ OwensValley/Board_Order_FINAL_20160425.pdf (accessed January 28, 2020)
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From page 128... ...
One disadvantage of relying on control area–specific estimates of PM10 emissions, based on airborne PM10 concentration, is the difficulty in assessing compliance under low to moderate wind conditions. Current surrogate measures for dust control effectiveness, such as areal coverage of shallow flooding or percent vegetative cover, are applied under any wind conditions.
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From page 129... ...
Recommendation: Additional research on individual and hybrid DCMs should be con ducted to develop new approaches that use less water, maximize other environmental ben efits, and ensure that DCMs maintain performance over the long term. Specific research topics to inform future decision making at Owens Lake are outlined in this chapter and include the following: • Strategies for long-term salinity management in shallow flooding and managed vegeta tion DCMs, including an evaluation of the capacity to maintain target salinities over time; • Minimum percent coverage needed for alternative vegetation species and mixtures of species as DCMs with the potential to reduce irrigation requirements, and how site specific conditions on the lakebed impact the performance, durability, and manage ment requirements of those measures; 129
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From page 130... ...
Monitoring BACM Effectiveness Conclusion: Operational evaluations of BACMs and other DCMs have relied on sur rogate performance criteria to monitor PM10 control efficiency, which introduces a high degree of uncertainty. Recommendation: LADWP and the District should evaluate DCM performance based on PM10 emissions from dust control areas, estimated from measurements of airborne PM10 concentrations under a variety of wind conditions.
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