Evaluation of Options to Offset Selenium Impacts in Tributaries/ Drains in the Grand Valley of Western Colorado

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1 Evaluation of Options to Offset Selenium Impacts in Tributaries/ Drains in the Grand Valley of Western Colorado Performed in conjunction with the Grand Valley Selenium Task Force through the Bureau of Reclamation s Technical Assistance to States Program U.S. Department of the Interior Bureau of Reclamation January 2007

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3 Table of Contents Executive Summary...v Introduction and Study Purpose...1 Study Background...1 Study Process and Identification of Options...1 Most Promising Offset Options...4 Option 1 -- Improve Colorado River backwater habitat...4 Option 3 Dilute high priority tributaries/drains...7 Option 4 -- Improve aquatic habitat in tributaries/drains...8 Option 5 Restore and protect important habitat at other sites...9 Option 7 Treat selenium contaminated water...11 Option 9 Promote wise water use through public education...12 Conclusions & Recommendations...13 iii

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5 Executive Summary This study examines offset or mitigation options to respond to suspected impacts of high selenium concentrations in tributaries/drains in the Grand Valley on the north side of the Colorado River. A previous study a concluded that meeting water-quality standards for selenium in 12 tributaries/drains in this area would be extremely costly and possibly infeasible. The costs of the alternatives presented in that study ranged from $73 million to over $2 billion. The Grand Valley Selenium Task Force (GVSTF) believes both figures are economically unreasonable and well above local citizens and governments ability to pay. Additionally, the lowest cost alternative and some of the other alternatives would have extensive negative impacts on aquatic and terrestrial habitat that has developed in the tributaries over the last 100 years of their use as agricultural drains. In response, members of the GVSTF asked what can reasonably be done in response to the high selenium concentrations? The purpose of this study and report is to identify and evaluate less costly and more effective measures or options that could be implemented to offset the current, suspected selenium impacts to aquatic life in these Grand Valley tributaries/drains. These offsets are meant to counterbalance or compensate for selenium-related impacts where reasonable, cost-effective solutions to meet the water-quality standard are not available. The offsets may or may not actually reduce selenium concentrations or loading yet would result in a net environmental benefit for aquatic species. Evaluations of the options presented herein were conducted at an appraisal (or pre-feasibility) level of detail to identify concepts worthy of further, more-detailed study and consideration. The GVSTF will use information developed in this study in decisions on whether to promote further studies or implementation of any of the more promising options. Six of the most promising offset concepts identified by the GVSTF are displayed and evaluated in this report: Improve Colorado River backwater habitat, Dilute high-priority tributaries/drains, Improve habitat in tributaries/drains, Develop replacement habitat at other sites, Treat selenium contaminated water, and Promote wise-water use through public education. a Evaluation of Selenium Remediation Concepts for Selected Tributaries in the Grand Valley of Western Colorado, Bureau of Reclamation, March 2006 v

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7 Introduction and Study Purpose This study is a follow-up to a previous Bureau of Reclamation report entitled Evaluation of Selenium Remediation Concepts for Selected Tributaries/Drains in the Grand Valley of Western Colorado, dated March That previous study concluded that meeting water-quality standards for selenium in 12 tributaries/drains on the north side of the Colorado River in the Grand Valley would be extremely costly and possibly infeasible. The costs of the alternatives presented in that report ranged from $73 million to over $2 billion. Both estimates were judged to be economically infeasible by the Grand Valley Selenium Task Force (GVSTF). Additionally, the lowest cost alternative and some of the other alternatives would have extensive negative impacts on aquatic and terrestrial habitat that has developed over the last 100 years in these tributaries as they served as perennial irrigation drains. The report went on to state that there may be opportunities to accrue similar or even greater net benefits to aquatic life in higher priority locations at a much lower cost. Thus, the purpose of the work reflected in this report is to identify and evaluate less costly and more effective measures or options that could be implemented to offset or mitigate the current, suspected selenium impacts to aquatic life in the Grand Valley tributaries/drains. These offsets are meant to counterbalance or compensate for those selenium-related impacts where reasonable, cost effective solutions to meet the waterquality standard are not available. Evaluation of the options presented herein was conducted at an appraisal (or prefeasibility) level of detail to identify concepts worthy of further, more-detailed study and consideration. The GVSTF will use information developed in this study in decisions on whether to promote further studies or implementation of any of the options. Study Background Background information on the project area and selenium impacts can be found in the previous report entitled -- Evaluation of Selenium Remediation Concepts for Selected Tributaries/Drains in the Grand Valley of Western Colorado (March 2006). Study Process and Identification of Options The process utilized by the GVSTF to develop this report involved: 1) Identifying potential offset or mitigation measures or options through examination of previous efforts, including the National Irrigation Water Quality Program (NIWQP), supplemented with brainstorming by the GVSTF technical subgroup; 2) Briefly evaluating the effects of each option; 3) Identifying the most promising options; and 4) Developing and presenting additional information on those options. The GVSTF technical subgroup was charged with the following question What measures could be implemented to offset or mitigate selenium impacts to aquatic life in the Grand Valley tributaries/drains? Table 1 contains the results of the first 3 items stated above, presenting all the options identified to date. Additional detail and discussion of the most promising options from Table 1 is presented in the next section of this report, entitled Most Promising Offset Options. 1

8 ID Number Table 1 Comparison of options to offset or mitigate selenium impacts in the Grand Valley tributaries/drains Option (The most promising are highlighted.) 1 Improve Colorado River backwater habitat 2 Screen to prevent high selenium food/prey items entering critical habitat 3 Dilute high priority tributaries (e.g., Big Salt Wash, mouth to 1 mile north of Highway 6 or Lewis Wash (D Road to River) 4 Improve aquatic habitat in tribs/drains 5 Restore/ protect important habitat at other sites Description Pros Cons implement diversion & dilution measures to reduce selenium concentrations in critical endangered fish habitat. NIWQP studies previously identified 20+ potential sites in the Grand Valley. install screens in tributaries as they enter 100-year floodplain to reduce the availability and selenium impacts to endangered fish consuming these prey items reduce concentrations from 50 ppb to 20 ppb or less under assumption this would benefit aquatic life and reduce impacts of high selenium food organisms entering critical habitat. Use small storage reservoirs, winter canal diversions, or pipe small amounts of water to high priority tributaries improvements might include: - more sinuosity - more woody debris - removal of non-native fish - removal of tamarisk & replacement with native vegetation (to reduce depletions from tamarisk) - reduced sediment load - develop additional flooded bottomland habitat similar to Recovery Program sites - reduce tamarisk along rivers to increase flows & increase sinuosity -relatively inexpensive - helps recover endangered fish - focuses on tributaries where the greatest benefits to aquatic life can be expected may include other environmental benefits such as open space, aesthetics, etc. - benefits endangered fish - may include other environmental benefits such as open space, aesthetics, etc. -rights-of-way needed on private lands - contaminated prey items can still enter backwater from tributaries - may negatively impact endangered fish habitat (e.g., at CO River Wildlife Area) - O&M would be difficult & expensive - high se concentrations in critical habitat may still increase concentrations in prey items to toxic levels - could limit movement of fish to spawn in the tributaries - extreme costs for dilution water if storage is required - contrary to efforts (e.g., Grand Valley Water Management project) to reduce canal diversions to benefit endangered fish in mainstem - numerous concerns about winter canal diversions and operations - not necessarily beneficial to endangered fish species - may create attractive nuisance since selenium concentrations would still be high. Feasibility Concerns (Note: securing funding is a concern for all options) Implementation Cost - ability to secure ROW $20, ,000 per site - screen size requirement would make this infeasible due to likely plugging of screens - costs of water delivery - winter canal operations - water rights - public safety - stormwater-carrying capacity - erosion/sediment - must be done in ways that don t reduce the function of the drain and create additional flood issues - cost & ability to secure easements/ ROW -increased flood risk undetermined - costs can only be estimated based on site specific plan which is beyond the scope of this study. undetermined $0 to $400,000 per site 2

9 Option (The most promising are highlighted.) 6 Remove dams in the upper Colorado River basin ID Number 7 Treat selenium contaminated water 8 Stock more endangered fish 9 Promote wise water use through public education 10 Remove nonnative fish Description Pros Cons remove dams to benefit endangered fish; increased runoff flows would allow more flooded bottomlands and habitat at critical times of the year use bioreactors or other methods to treat ground-water drainage (from drains that don t receive tailwater or canal spills) to reduce loading & then return the treated water back to dilute a tributary, thus reducing selenium concentrations build another hatchery and stock additional fish (above numbers currently being stocked by Recovery Program); the Recovery Program is presently stocking about 14,000 razorback suckers annually. DOW is stocking pikeminnow & bonytail. institute public programs that reduce polluted runoff or return flow to the tributaries/drains reduce large impact non-native fish have when competing with natives. This is a major component of the Recovery Program and is underway. would cause more frequent flushing flows benefiting endangered fish reduces selenium load & concentrations in tributaries & Colorado River - stocking more fish may lead to a quicker recovery of endangered species - can lead to many water conservation benefits including reducing need for additional infrastructure & more available dilution water. - eliminates competition with native fish - extreme financial & social costs (flood damages, loss of recreation, etc.) - water supply would have to be replaced by new projects with associated impacts - late summer flow augmentation would be unavailable - bioreactors are unproven technology - may be relatively costly - stocking does not constitute recovery of the endangered fish; self-sustaining populations are required Feasibility Concerns (Note: securing funding is a concern for all options) - not likely to be politically or socially acceptable - prove the technology (BOR S&T program is funding a bench-scale test of bioreactors; completion is planned for April 2007) - it is unknown whether these stocked fish are surviving and reproducing in significant numbers - results are hard to identify and quantify - this measure is already underway in the Grand Valley through the Wise Water Use Council, Drought Response Information Project (DRIP) and irrigation company/reclamation efforts - lacks public support - may not be effective - never ending task - extreme costs Implementation Cost undetermined $500,000 to 900,000 for 4-5 cfs installation undetermined $20,000 to 50,000 annually Representative cost may be available from Recovery Program 11 Increase instream flows in mainstem rivers reduce human use upstream and change water rights to an in-stream flows - beneficial to aquatic life in rivers - Human uses upstream are currently on the up-swing; would be difficult to accomplish reductions Already investigated by Recovery program. Coordinated reservoir operations currently increases spring peak. undetermined 3

10 Most Promising Offset Options The following is a more in-depth examination of only the most promising of the options displayed in Table 1. They are listed according to the ID number in the table and are not presented in any specific priority. They all conform to the mission statement of the Task Force which is: To evaluate, assess and actively address elevated selenium and other adverse water quality issues while maintaining the area s economic viability, quality of life, and agricultural heritage. Option 1 -- Improve Colorado River backwater habitat Description In the late 1990 s, the NIWQP Core Team, which included representatives of the U.S. Fish and Wildlife Service, U.S. Geological Survey and Bureau of Reclamation, identified critical Grand Valley bottomland/backwater habitat adjacent to the Colorado River as their highest priority for remediation and reduction of potential selenium impacts to endangered native fish. Adult female fish utilize some of these areas for staging prior to reproduction (laying eggs). It is believed that a majority of selenium accumulated by the adult fish is stored in their eggs. Additionally, the offspring or larval fish often utilize this same habitat, particularly during runoff when these areas provide conditions more suitable to survival and growth (warmer water, lower velocities, more abundant food resources, etc.) than within the river itself. The larval fish feed on various food organisms found there which often times have high selenium concentrations. The NIWQP studies identified 23 potential remediation sites in the Grand Valley (Figure 1). Option 1 would involve the implementation of diversion & dilution measures to reduce selenium concentrations in the surface water bodies and channels in bottomland/ backwater habitat in the Grand Valley. The NIWQP identified diversion and dilution as two of the most cost-effective remediation measures for this type of habitat. High selenium inflows would be intercepted or diverted. Diversions from the river or other sources of relatively clean (low selenium concentration) water would be used to dilute the remaining contaminated waters. An example of this type of remediation is shown in Figure 2, which displays a preliminary (un-implemented) NIWQP plan for remediation of one valuable habitat area at the mouth of Adobe Creek. Evaluation During the period, , the NIWQP implemented diversion/dilution projects at the Orchard Mesa Wildlife Area (OMWA) and Colorado River Wildlife Areas (CRWA). The OMWA project involved the diversion and use of flows with high selenium concentrations from a tributary/agricultural drain to irrigate vegetation in the wildlife area. In addition, several flushing (dilution) channels were excavated to reduce concentration in 2 backwater areas (Figure 3). At the CRWA, the inlet to an old secondary channel of the Colorado River was excavated and opened to encourage flushing of selenium contaminated waters originating from Lewis Wash. The OMWA and CRWA projects are continuing to function and will receive periodic maintenance until NIWQP set-aside funding runs out. Unfortunately, performance monitoring was initiated but discontinued following construction due to NIWQP funding shortages. Therefore, it is not known how effective these projects have been in reducing selenium concentrations in this important endangered fish habitat. 4

11 Sites Figure 1 - Prospective backwater/bottomland selenium remediation sites identified by the NIWQP 5

12 Figure 2- Un-implemented NIWQP plan for mouth of Adobe Creek (near 18 Road east of Fruita) Comparison points Pros: - relatively inexpensive - reduces potential selenium impact to endangered fish and benefits recovery efforts Cons: - most rights-of-way needed for the 23 sites are on private land; securing necessary ROW may be difficult or costly - contaminated prey items can continue to enter the backwater habitat from Colorado River tributaries & agricultural drains - carries the possibility of negatively impacting endangered fish and larval habitat by changing velocities, turbidity, and water temperatures (e.g., at CRWA) Other considerations: Implementation cost range: $20, ,000 per site (source: NIWQP) Figure 3 - Excavating a flushing channel at Orchard Mesa Wildlife Area Additional study needs Previous NIWQP project areas such as the OMWA and CRWA should be reviewed and monitored to ascertain the impacts of those 2 projects. At a minimum, data should be collected on changes in water quality and selenium concentrations in endangered fish prey items. 6

13 Option 3 Dilute high priority tributaries/drains Description Option 3 would utilize small storage reservoirs, winter canal diversions, or pipelines to deliver small amounts of water to high priority tributaries (e.g., Big Salt Wash, mouth to 1 mile north of Highway 6 & 50, or Lewis Wash, mouth to D Road) during the non-irrigation season (November through March). The tributary reaches to be targeted would be chosen primarily based on which ones were mostly used by native fish. Sufficient amounts of dilution water would be provided to reduce concentrations from about 50 ppb down to 20 ppb or less under the assumption this would benefit aquatic life and reduce the impacts of high selenium food organisms originating from the tributary and entering critical habitat for endangered fish. Evaluation In order to fully evaluate this option, the layout and details associated with specific sites must be examined. One would want to look at the opportunities and feasibility to use existing or newly excavated channels and other facilities to accomplish the dilution. Unfortunately, examining specific sites is beyond the scope of this study and report. Comparison points Pros: - can be focused on specific tributaries which hold the best potential for benefiting aquatic life Cons: - relatively high costs for dilution water if storage is required - contrary to efforts to reduce canal water diversions which are being implemented to benefit native fish in the mainstem Colorado River - using winter canal diversions to convey dilution water has numerous concerns as were detailed in Table 5 in the previous report entitled -- Evaluation of Selenium Remediation Concepts for Selected Tributaries/Drains in the Grand Valley of Western Colorado (March 2006) Other considerations: Implementation cost range: unknown, depends on the specific site Additional study needs Future studies should focus on specific locations where improvements could potentially produce the most benefits to aquatic life. The Colorado Division of Wildlife (CDOW) and U.S. Fish and Wildlife Service could assist in identifying sites. The studies could identify what measures would be most cost-effective and estimate the site-specific costs of those improvements. Figure 4 - Big Salt Wash at Highway 6 & 50 7

14 Option 4 -- Improve aquatic habitat in tributaries/drains Description Option 4 would involve the implementation of various aquatic habitat improvements in one or more of the Grand Valley tributaries/drains. The goal of this effort would be to offset impacts of selenium on aquatic life by improving other conditions that affect growth and survival of fish that utilize this habitat. Conditions that could be improved include more suitable velocities, fewer predators, and decreased turbidity. The following is a preliminary list of potential improvements: - increase sinuosity of the channel - increase woody debris - remove non-native fish - remove tamarisk & replace with native vegetation (to reduce water depletions due to tamarisk) - reduce sediment load Evaluation Fishery biologists believe this option would improve the habitat for less-sensitive fish species but may create an attractive nuisance for the sensitive species (e.g., some of the native species). Comparison points Pros: - may include other environmental benefits such as increasing open space, improving aesthetics, etc. Cons: - not necessarily beneficial to endangered fish species which make limited use of the tributaries (i.e., it s not historical habitat) - may create attractive nuisance since selenium concentrations would still be high. - non-native species may find the improvements attractive. Other considerations: - must be done in ways that don t reduce the function of the drain to carry return flows back to the river or create additional flood issues - implementation cost range: $ unknown Figure 5 - Tamarisk infestation along Adobe Creek/Drain J Additional study needs Site specific studies could help identify specific improvements that would benefit a particular stream and its inhabitants. They could also identify what species may be most affected. Needs of species of special concern could be specifically targeted. These are species of concern to the CDOW that may be becoming rare or endangered. Pilot projects would probably be recommended. 8

15 Option 5 Restore and protect important habitat at other sites Description Option 5 would involve the general restoration and protection of aquatic habitat at sites adjacent to the Colorado River to benefit endangered fish species. This would be similar to or an extension of work that has been done by the Upper Colorado River Endangered Fish Recovery Program for flooded bottomlands in several Grand Valley and lower Gunnison River locations. Inundated floodplain habitats provide food, warm water temperatures, calm water, and vegetative cover from predators. Improvements have been previously made at 8 areas in the Grand Valley and along the lower Gunnison River to restore fish access and usability of the sites by native Colorado River fish. The Program has purchased easements and properties in fee title to preserve them from development and removed levees or cut notches in them to allow more overbank flooding. A February 2006 Floodplain Management Plan ( pdf) published by the Recovery Program describes a proposed continuing effort to identify the most valuable sites for restoration, mechanically reconfigure strategic sites (Figure 6), stock fish, control non-native fish, and insure suitable flows to create flooding of those sites. The report includes an extensive list of current and potential restoration sites. Levee removed Figure 6 - Walter Walker State Wildlife Area. A portion of the upstream levee was removed by United Sand and Gravel to salvage gravel and to facilitate overbank flooding to benefit endangered fish. 9

16 Evaluation Pat Nelson of the Upper Colorado Recovery Program was contacted about the success of these kinds of improvements and benefits to the endangered fish. He believes there has been success on the Green River (northeast Utah) where similar restorative improvements have been made, and razorback survival and recruitment are on par with what s described as natural conditions. However, under natural, unrestored conditions, 99% of larvae do not survive. To date, this type of success has not been acknowledged on the Colorado or Gunnison Rivers. Mr. Nelson believes breaching more levees should be beneficial to the fish. Comparison points Pros: - may include other environmental benefits such as increasing open space, improving aesthetics, etc. Cons: - the Recovery Program has encountered several issues that have prevented action at other sites including: lack of funding, problems with easement acquisition, flood damage risk to adjacent landowners, and high estimated costs for acquisition and restoration. Other considerations: Implementation cost range: $ 0 (donated; e.g., at Walter Walker State Wildlife Area) to $400,000 per site Additional study needs The February 2006 Recovery Program report identified the following research needs to address uncertainties and to fill information gaps necessary for achievement of their restoration plan: 1. Evaluate effectiveness of reset theory [reset theory includes the following principles: a) periodic inundation of floodplains allows access to drifting larval razorback sucker and escapement of adults; b) periodic inundation/desiccation stimulates food production and freshens water quality; and c) periodic desiccation strands and kills non-native fishes.]; 2. Locate razorback sucker spawning sites with radio telemetry; 3. Describe larval drift and entrainment; 4. Assess growth and survival; 5. Evaluate importance of gravel pits, depressions, and short-term floodplains; and 6. Evaluate effects of non-native fish. 10

17 Option 7 Treat selenium contaminated water Description Option 7 would involve the use of passive, selenium-reducing bioreactors or other methods to treat irrigation drainage (from high selenium concentration sources such as drains that don t receive tailwater or canal spills) to reduce loading to the Grand Valley tributaries and the Colorado River. Treated water would be returned back to dilute important tributaries/drains, reducing selenium concentrations for the purpose of improving the aquatic habitat. Figure 7 -- Typical Bioreactor Site (Yellow Creek, Pennsylvania) Evaluation Passive selenium reducing bioreactors are unproven technology but are very similar to proven technology using sulfate-reducing bacteria. A research effort is currently underway in the Grand Valley by Mesa State College and Golder Associates with funds provided by the Bureau of Reclamation s Science & Technology Program (S&T Program). The biologically-assisted removal of selenium from water has been demonstrated using active but expensive methods that involve nutrient addition, precipitation, and filtration. The current S&T Program research effort involves bench-scale experiments, conducted over a span of about six months, to develop data necessary to evaluate the kinetics and feasibility of using passive selenium reducing bioreactors to replicate the success of active treatment methods but at a reduced cost. The bench-scale tests are evaluating different construction materials placed in 55-gallon drums (small bioreactors) including inexpensive agricultural wastes such as wood chips, moldy hay, sawdust, and animal manure. This effort hopes to identify the most effective materials for selenium reduction. Passive bioreactors could operate 10 years or more without the need to change the media. Comparison points Pros: - reduces selenium load & concentrations in both tributaries/drains and the Colorado River Cons: - bioreactors are unproven technology - may be relatively costly (compared to habitat improvements) Other considerations: Implementation cost range: $500,000 to 900,000 for installations treating 4-5cfs of concentrated drainage (includes limited drainage collection system). Additional study needs: If the bench-scale test is successful, a field-level demonstration project might be undertaken as a next step. Should the bioreactor concept prove ineffective, much costlier treatment methods are available and could be investigated; however, there s a very good possibility that costs would be beyond what the Task Force might consider reasonable. 11

18 Option 9 Promote wise water use through public education Description Option 9 would involve the implementation of educational and incentive-based programs to encourage the more efficient or wise use of outdoor water for crop and turf irrigation and for landscape features. This could supplement current efforts which are underway by members of the Grand Valley/Gunnison Basin Wise Water Use Council (WWUC). The WWUC is currently pursuing 2 primary goals: Encourage and promote wise water use to maintain water supply and improve water quality as growth occurs in the Grand Valley and lower Gunnison basin; and Encourage efficient use and to provide for sound, well-designed irrigation systems through the development of irrigation standards for subdivisions. Evaluation More efficient outdoor water use would reduce the volume of water that percolates or seeps into the ground and contributes to the shallow ground-water system where selenium is mobilized and eventually returns to the tributaries/drains and Colorado River. Figure 8 shows a pond lining effort at the Devil s Thumb Golf Course (near Delta) to reduce seepage and groundwater impacts. Will such a program be effective? Can behaviors be changed? Based on a brief web literature search, this is a difficult question to answer. It appears that little has been done nationwide to document the effects of outreach and educational programs on non-point source loading. However, according to Dave Galvin with the King County Department of Natural Resources and Parks in Seattle, Washington, This doesn t mean, necessarily, that outreach or social marketing programs are ineffective, but rather that measurement of the ultimate goal of environmental improvement is complex, highly variable, expensive to conduct, and thus rarely pursued. Mr. Galvin s paper entitled Measuring results from outreach and educational program Can we see improvements downstream? is an excellent source of guidance for thinking about and designing effective programs. Another source of education and outreach information and program design strategies, Community Based Social Marketing, can be viewed at This program appears to offer some new perspectives on identifying effective social-marketing strategies and is currently under consideration by the WWUC. Comparison points Pros: - may lead to additional water conservation benefits including reducing need for additional domestic water infrastructure and storage reservoirs. Cons: - results of many water conservation efforts are difficult to directly identify Other considerations: Implementation cost range: $5,000 to $100,000 or more annually Additional study needs It might be useful to identify paired watersheds and employ measures in one and not the other to determine if changes in water quality occur. 12

19 Figure 8 Lining a pond at the Devils Thumb Golf Course to reduce seepage and its associated impacts (photo by Delta County) Conclusions & Recommendations The level of remediation required to reduce selenium concentrations in Grand Valley tributaries/drains to below Colorado water-quality standards is most likely, financially infeasible. This study identifies and provides a preliminary evaluation of several options for reasonably responding to potential selenium-related impacts to aquatic life in tributaries/drains. The options were identified to either reduce concentrations in specific, highly beneficial habitat or offset the impacts by restoring or enhancing conditions in valuable aquatic habitat. This study and report are based on an appraisal-level or preliminary level of detail. Should the Grand Valley Selenium Task Force or others wish to follow this potential course of reasonable remediation, additional and more detailed studies of selected options should be undertaken. It is anticipated that following the conclusion of this study, the GVSTF will review other information and complete its decision-making process. The choices include whether and how to: Remediate selenium impacts in the tributaries/drain Offset or mitigate those impacts (using options displayed in this report), or No action. 13