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Overview
Basics
Basics
Given the significant expected cost associated with nutrient and FSP load reductions needed in the Tahoe Basin, and the fact that this effort will occur over a decadal timeframe (Lahontan and NDEP 2008), it is relevant to examine the characteristics of urban runoff water treatment associated with fine sediment particles and other important water quality characteristics, such as turbidity, total and size fractionated suspended solids and phosphorus loading. This information will be needed for improved management models and to determine the effectiveness of fine sediment removal by processes and unit operations that target this removal in different types of BMPs.
Completed
2009
2010
2016
$251,302
Alan Heyvaert (alan.heyvaert@dri.edu)
09/20/2017
09/20/2017
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| Location Information | Location Notes |
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Organizations
EIP Details
EIP Basics
EIP Basics
04.01.01.0048 - P054: Tahoe Stormwater Particle Assessment and Management for Urban and Roadway Runoff
Performance Measures
Expected Performance Measures
Expected Performance Measures
No expected performance measures set for this project.
Reported Performance Measures
Reported Performance Measures
No annual performance measure accomplishments entered for this project.
Funding
Expected Funding
Expected Funding
$251,302
$251,302
$0
| Total | |||
|---|---|---|---|
| Unknown or Unassigned | $251,302 | $251,302 | $0 |
| Grand Total | $251,302 | $251,302 | $0 |
Reported Expenditures
Reported Expenditures
| Total | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | |
|---|---|---|---|---|---|---|---|---|---|
| Southern Nevada Public Land Management Act (Pacifi... | $251,302 | $31,413 | $31,413 | $31,413 | $31,413 | $31,413 | $31,413 | $31,412 | $31,412 |
| Grand Total | $251,302 | $31,413 | $31,413 | $31,413 | $31,413 | $31,413 | $31,413 | $31,412 | $31,412 |
Photos
Other Details
Watersheds
No watersheds set for this project.
Threshold Categories
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Although urban areas in the Tahoe Basin occupy a relatively small amount of the total watershed, they contribute a substantial portion of pollutant loadings that have caused clarity loss in the lake. Since fine particles (<16 µm) and nutrients both contribute to clarity reductions in Lake Tahoe (Jassby et al., 1999; Swift et al., 2006), these are the focus of current pollutant reduction strategies, with an emphasis on reduction in FSP loading (LRWQCB and NDEP, 2008).
Local and Regional Plans
No Local and Regional Plans set for this project.
Related Projects
Related Projects
No Related Projects set for this project.
External Links
Notes
Notes
| 08/24/2017 7:14 AM | System | Objectives: The goal of this project was to investigate urban stormwater characteristics and treatment for management of fine sediment particle (FSP <16 µm) concentrations, turbidity and nutrient concentrations in runoff. The urban watershed contributes about 70% of fine sediment delivered into Lake Tahoe, so the objectives for this project included: • Assessing functional relationships between fine sediment particle concentrations, turbidity, fractional suspended solids and phosphorus in urban stormwater runoff. • Providing information on the efficiency of fine particle removal in retention basins and vegetated treatment systems. • Evaluating how well pollutant removal processes for sediment particles and nutrients perform over the typical life cycle period of a constructed treatment wetland. Initially, the approach for this project focused on evaluating performance characteristics in the Tahoe City Wetland Treatment System, a stormwater treatment method implemented in 1998. That system was taken off-line midway through the course of this project, so efforts were refocused on evaluating material accumulated within the basin over it’s lifespan as a treatment wetland, and using this information as an indication of performance and treatment capacity. Additional analyses and tests on urban and highway runoff samples from the Tahoe Basin were conducted to evaluate characteristics relevant to treatment processes and pollutant removal. The overall approach taken in this project was to: • Analyze stormwater runoff samples for distribution of fine sediment particle concentration, turbidity and size-fractionated nutrient content. • Collect sediment cores from a stormwater wetland treatment basin at its end-of-life cycle and analyze these to establish nutrient and fine sediment retention characteristics. • Develop recommendations for restoration and management of stormwater treatment wetlands in the Tahoe Basin. |
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| 08/24/2017 7:08 AM | System | Findings: • Size fractionated stormwater runoff samples showed that on average over 85% of turbidity measured in unfiltered samples was associated with the <20 µm size fraction, and approximately 55% was associated with the <10 µm size fraction. • On average, FSP in runoff samples represented over 50% of the total suspended particle mass while the <10 µm fraction contained about 37% and the <5 µm fraction contained about 23% of particle mass. Note, however, that particle number concentrations decrease exponentially with increasing particle size such that 99% of total particle numbers are contained in the <5 µm size fraction. • Particulates in runoff samples averaged 28% organic material, with almost all of it in the <20 µm fraction. Phosphorus concentrations in runoff samples were predominately associated with the <20 µm size fraction (85%), with substantial amounts in the <10 µm fraction (57%) and in the <5 µm size fraction (38%). Results from nitrogen analyses were less consistent and much more variable than for phosphorus. • Sediment accumulation in the constructed treatment wetland averaged 3.7 centimeters per year. Over the 16 year period of active use this accretion raised the sediment surface approximately 60 centimeters, sufficient to interfere with hydrologic function so that ultimately excavation was required to restore capacity and reestablish flow paths. *** See www.fs.fed.us/PSW/partnerships/tahoescience for additional findings. |
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| 08/24/2017 7:07 AM | System | Management Implications: • Most of the phosphorus in urban stormwater runoff is associated with the FSP (<16 µm) fraction, and about half of that is contained and transported by the <10 µm size fraction. Similar results were found with turbidity and sediment loading. This suggests that best management practices (BMPs) should place increasing emphasis on the retention of <10 µm particle size fractions. • Wetland retention basins efficiently combine the physical properties of a retention basin with the biological characteristics of wetlands. The Tahoe City system was designed to remove nutrients and fine sediments from urban runoff through retention basin physical processes and wetland basin biological properties. It was so successful in meeting these goals that it ultimately accumulated too much material and needed to be restored after 16 years of useful performance. • Accretion of nutrients, metals and inorganic sediments in the Tahoe City constructed treatment system was much higher than found in natural wetlands. Retention of fine silt and clay-sized particles was much greater than would be expected from a stormwater retention basin without wetland function, which likely contributed to the relatively high rates of phosphorus and FSP removal, including the retention of sediment size fractions finer than 10 µm. *** See www.fs.fed.us/PSW/partnerships/tahoescience for additional management implications. |
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| 08/24/2017 7:06 AM | System | Publications: www.fs.fed.us/PSW/partnerships/tahoescience Heyvaert, A.C., R.G. Qualls, J.E. Reuter. 2016. Assessment of Tahoe stormwater characteristics and treatment processes for management of urban and roadway runoff. Draft final report prepared for the USDA Forest Service, Pacific Southwest Research Station. January 2016. |