Reservoir Sedimentation and Water Supply Reliability By: Aubrey Mescher, MESM Ms

Reservoir Sedimentation and Water Supply Reliability By: Aubrey Mescher, MESM Ms. Mescher is a water resources specialist at Aspen’s Agoura Hills headquarters office. Our reservoirs are filling with sediment. That’s the same as dirt. Mud, muck, silt. Rocks, gravel, even boulders. All of this stuff where there’s supposed to be just water. Water for drinking, irrigation, recreation, commercial and industrial uses, flood control, and groundwater recharge. This isn’t a new issue. Actually, reservoirs are assumed to have a finite lifetime, limited by loss of function due to sedimentation. But reservoirs are filling with sediment far more quickly than anticipated, and important water supply and flood control facilities are not only being rendered useless before their time, but in doing so they are simultaneously introducing new issues with public safety and water supply reliability. What is sedimentation? Sedimentation is a natural process that occurs when soil particles suspended in water settle out of the main water column to the bottom. Sediment content in a waterway is higher during and after storm events, when rates of flow and erosion are higher, and lower during dry months, when these rates tend to be lower. Under natural conditions, unconstrained by a dam, the quantity of water and sediment in a waterway is generally balanced, as the ground surface and riverbed erode into the waterway, and sediment is deposited in downstream areas, where it provides habitat and replenishes riverbanks and beaches. But when a dam is constructed in a waterway, it traps the flow of both water and sediment. The sediment gradually accumulates behind the dam, larger particles such as rocks and gravel settling to the reservoir floor while the spaces in between fill with finer material such as silt and mud. Over time, accumulated materials reduce reservoir storage capacity, and the dam loses value as a flood control and water supply facility. Hydroelectric dams also lose value, as decreased reservoir capacity results in decreased power generation. Perhaps it is time to consider that operation and maintenance of a dam require as much focus on sediment management as on water management. What causes increased sedimentation? As a natural process, the rate of sedimentation is affected by factors such as topography, geology, flow volume and velocity, and climate conditions. Therefore, reservoir sedimentation will occur at different rates, depending on local conditions. Hetch Hetchy Reservoir, which is formed by the 90-year-old O’Shaughnessy Dam on the Tuolumne River, is estimated to contain only two inches of sediment because the Tuolumne riverbed is mostly granite and erodes very slowly (Biba, 2012). In comparison, Matilija Reservoir, located on a tributary of the Ventura River, was only 17 years old when it lost 27 percent of its capacity due to sedimentation from a 100-year storm event in 1969; today the 65- Hetch Hetchy Valley, prior to construction of O’Shaughnessy Dam. year-old reservoir is virtually Source: PBS, 2013

1 useless, with more than 90 percent of its capacity lost to the six million tons (two million cubic yards [mcy]) of silt and sediment trapped by Matilija Dam (Matilija Coalition, 2002a). It’s not that any greater consideration to upstream conditions was provided when O’Shaughnessy was constructed in 1923 than when Matilija was constructed in 1947; conditions on the Tuolumne River are just so different than on Matilija Creek and the Ventura River. Two of the greatest factors influencing increased rates of sedimentation include development that replaces natural ground cover, and changes to soil composition that make it more susceptible to erosion. These factors are not always mutually exclusive. Development tends to replace natural or vegetated ground cover with impervious or less permeable surfaces; in response, the rate of surface water runoff increases, and rates of erosion and sedimentation increase. A 2004 study of sedimentation in Lake Elsinore, located approximately 75 miles southeast of Los Angeles, supported this connection by concluding that average 20th- century sedimentation rates are several times higher than 18th- and 19th-century rates (Byrne, R. and Reidy, L., 2004). The 20th century also marked a time of substantial urban growth in southern California,

Lake Elsinore, CA. Source: grandfathersmc, 2013 compared to the 18th and 19th centuries. Regarding soil composition changes which facilitate erosion and sedimentation, the introduction of hydrophobic conditions is the most dramatic. Hydrophobic soil is water-repellent and prevents water from infiltrating the soil surface. Wildfires commonly result in hydrophobic conditions, because the burning of organic materials creates hydrocarbon residue which settles into small In support of a Supplemental EIS/EIR for the spaces between soil particles, effectively Tehachapi Renewable Transmission Project creating a layer of waterproof soils. These (TRTP), which traverses the Angeles National soils may be located on the ground surface Forest (ANF) and Station Fire burn area, Aspen or at shallow depths. After the Station Fire of hydrology and computer resources specialists prepared a GIS-based model of erosion and 2009 burned 161,188 acres of watershed in sedimentation on the ANF resulting from the the Angeles National Forest, the USDA Station Fire, in order to develop project-specific Forest Service conducted hydrologic mitigation measures for potential erosion and analyses of the burn area, and determined water quality impacts of the TRTP. that extremely hydrophobic soils were located one-half inch to two inches below the ground surface (USDA, 2009). Due to the hydrophobic soils being buried, it was anticipated that the first precipitation events after the fire would saturate and wash away the soils resting on top of the hydrophobic layer(s). The Forest Service estimated that the amount of sediment and debris that could be delivered to downstream areas as surface runoff would increase by 100 to more than 400 percent in the first few years following the Station Fire (USDA, 2009).

2 Downstream and adjacent to the Station Fire burn area are the cities of Los Angles, Glendale, La Crescenta, La Cañada Flintridge, Pasadena, Altadena, and Acton; flood control facilities in these jurisdictions received dramatically higher sediment loads during the wet seasons immediately following the Station Fire. The County of Los Angeles Department of Public Works (LADPW) is currently working to clear flood control facilities in these areas. As part of this effort, the LADPW has proposed and/or is currently executing sediment removal projects on the following major flood control facilities: Big Tujunga Dam, Cogswell Dam, Devil’s Gate Dam, Morris Dam, and Pacoima Dam. As one example, in the Devil’s Gate Reservoir, sediment inflow after the Station Fire has significantly reduced the reservoir's capacity and in its current condition, the reservoir’s outlet works are at risk of becoming clogged and inoperable (LADPW, 2013a). As with other flood control facilities in the area, the Devil’s Gate Reservoir no longer has the capacity to safely contain another major debris event, and removal of sedimentation from the reservoir is necessary to restore its functional capacity. As noted, the effects of development and altered soil conditions on sedimentation rates are Devil’s Gate Reservoir in the Los Angeles Basin. not mutually exclusive. For instance, development Source: LADPW, 2013a in forested areas has limited natural burn cycles due to fire prevention and suppression efforts, and our forests therefore tend to accumulate far more density and fuel than would occur under natural conditions. As a result, when fire is eventually introduced to a forested area, it tends to burn much hotter and faster than it would naturally, increasing both the potential for hydrophobic conditions and the removal of soil-stabilizing vegetation. Why should reservoir sedimentation be addressed? There are three primary objectives to managing water supply facilities, including reservoirs affected by sedimentation: water storage, environmental protection, and public safety. Public safety concerns include both the provision of flood hazard protection, and the removal of hazards associated with potential dam failure. As mentioned above, multiple flood control facilities within the jurisdiction of the LADPW are currently compromised due to sedimentation associated with runoff from the Station Fire burn area, and efforts are underway to rehabilitate these facilities and provide essential flood hazard protection to residents of the Los Angeles basin. In addition, aging dams which trap volumes of sediment risk structural failure and release of constrained materials to downstream areas, potentially burying property and habitat. The San Clemente Dam located on the Carmel River in Monterey County currently has only 70 acre- feet of its planned 1,425 acre-feet in storage capacity, due to more than 2.5 mcy of sediment entrained in the reservoir (CCC, 2010). In the early 1990s, the California Department of Water Resources (DWR) Division of the Safety of Dams determined that the dam could fail in the event of either the maximum credible earthquake or probable maximum flood (PMF), and a safety order for the dam was issued (CCC, 2010). Rather than simply stabilizing the structure, which would meet the requirements for public

3 safety, a plan is underway to temporarily divert the river and remove the dam structure in order to restore habitat along the river for steelhead and for California red-legged frog, thereby meeting another objective of addressing reservoir sedimentation, which is environmental protection. Similarly, the Matilija Dam in Ventura County was notched to 65 percent capacity in 1965, due to safety considerations (Matilija Coalition, 2002b); in addition to safety, a strong motivating factor to removal of Matilija Dam is the restoration of threatened steelhead habitat on the Ventura River. In addition to habitat restoration, the removal of hazardous or potentially hazardous materials accumulated in reservoir sediments is another Matilija Dam, 1948. Source: Matilija Coalition, 2002b environmental motive. The Combie Dam was constructed on the Bear River in northwestern California in 1926 in order to provide drinking and irrigation water to Placer and Nevada Counties. Sediment has regularly collected in the Combie Reservoir, and sediment removal activities and diversions have been ongoing for years under direction of the Nevada Irrigation District (NID). In Matilija Dam, 2013. Source: Plascencia, 2013 2003, water quality sampling conducted in accordance with Regional Water Quality Control Board permitting requirements identified elevated mercury levels in sediments entrained by the reservoir, a result of historic gold mining operations in the watershed. An effort is now underway to remove an estimated 150,000 to 200,000 tons of sediments from Combie Reservoir, remove the mercury using a mobile treatment system, then return clean water to the reservoir, export sand and gravel for construction uses, and dispose of unusable sediments. In addition to removing mercury-contaminated sediments from the reservoir, a primary objective of this project is to restore the reservoir’s storage capacity in order to provide drinking and irrigation water to the NID service territory. (NID, 2009) Water storage is also a fundamental aspect of dam and reservoir function. In arid regions such as the Southwest United States, water supply storage is an essential function to water supply reliability. Particularly in the face of climate change, improved water storage and conveyance infrastructure is essential to California’s water supply reliability. Overall, we expect to receive more precipitation as rain instead of snowpack, which means that we need to capture and store more water than ever before. This

4 will require not only the construction of new water storage facilities, but also the rehabilitation of existing facilities that have lost or are losing capacity, and the removal or abandonment of facilities that don’t provide a vital water supply function. It is important to identify the facilities that are most useful to water supply storage, and to invest in repairing and maintaining those projects. For example, the Elephant Butte Reservoir in New Mexico supplies an essential water supply to nearly 8,000 farmers, and has lost 600,000 acre-feet of its 2.6 million acre-foot capacity to sedimentation from the naturally silty Rio Grande watershed. Under management by the Elephant Butte Irrigation District, substantial effort has been invested in the removal and disposal of sediment from the reservoir, in order to maintain its capacity for water supply storage. A growing issue is what to do with the silt and sediment removed from Elephant Butte; developers are encouraged to use it for construction fill, but construction-related demands have been steadily decreasing, while sediment load remains constant. (Weiser, 2011) How is reservoir sedimentation addressed? Reservoir sedimentation is a dynamic issue that can be addressed from many different angles, each of which depends on site-specific conditions and the desired outcome. Ideally, a comprehensive management approach to sediment removal and control is the most effective in maintaining reservoir function and capacity. However, largely due to thin funding sources and thick permitting restrictions, reservoir sedimentation is most often addressed in response, rather than anticipation. Under these conditions, reservoirs affected by sedimentation are commonly dealt with through one of the following ways: abandonment; rehabilitation; dam modification; and/or upstream modifications. . Abandonment of a reservoir occurs when the dam is left in-place, with no efforts to remediate for environmental effects or improve reservoir function. This may be a desirable option for small reservoirs in remote areas, where structural improvement or removal would be difficult, and where the facility is not in danger of failure. If the dam is considered unstable, it may be structurally stabilized then still abandoned in place, with occasional monitoring to ensure structural integrity. . Rehabilitation involves the removal and disposal of entrained sediments to restore a reservoir’s functional capacity. Rehabilitation alone will not alter the amount of sediment entering a reservoir, but will maintain storage capacity; rehabilitation techniques may be incorporated into a long-term reservoir management plan. For instance, the aforementioned Elephant Butte Reservoir in New Mexico and Combie Reservoir in California are being maintained using rehabilitation techniques. . Dam modification refers to the structural alteration of dam facilities in order to accommodate sediment accumulation while maintaining reservoir capacity. This approach can increase the capacity of a reservoir, but typically does not alter the quantity of sediment entering a Aspen has provided extensive support for reservoir unless other activities such as modifications in the Prado Basin, including diversions or dredging are implemented at monitoring construction of flood control modifications, monitoring and mapping of the same time. For instance, dam vegetation, monitoring and assessment of modifications at the Prado Dam in Riverside threatened and endangered species above County included raising the dam by and below the dam, and assessment of approximately 30 feet, in addition to other impacts associated with construction of the modifications such as constructing new dikes Alcoa and Auxiliary Dikes, located within and raising the height of an adjacent the Prado Dam floodway. spillway; these efforts won’t necessarily alter the quantity of sediment washing into the reservoir on an annual basis. . Upstream modifications to a sediment-impacted reservoir can provide a long-term solution to sediment management, by diverting or entraining sediment in upstream basins before it can reach

5 the primary reservoir. For instance, a large-scale water and soil conservation program implemented on the Yangtze River has helped to relieve historically heavy rates of sedimentation in the Three Gorges Reservoir, one of the largest in the world (China Daily, 2004). These improvements include a series of major reservoirs built along upstream tributaries of the Yangtze to prevent sediment from entering Three Gorges Reservoir; it has been estimated that these improvements have reduced the annual sediment load passing through the reservoir from530 million tons to 200 million tons. Sediment that continues to accumulate in the reservoir is managed by releasing sediment-laden waters from sluice gates at the bottom of the dam during summer months (China Daily, 2004). As noted earlier, reservoirs are typically assumed to have a finite lifetime due to gradual loss of function from sedimentation. But it doesn’t have to be that way. Fan and Morris (2010) suggest that the concept of reservoir life being limited by sedimentation should be replaced by a concept of managing both water and sediment to sustain reservoir function, with sustainable use achieved through combined use of the following strategies: 1) Reduce sediment inflow using erosion control and upstream sediment trapping; 2) Route sediments past the reservoir using techniques such as drawdown during sediment-laden floods, off-stream reservoirs, sediment bypass, and venting of turbid density currents; 3) Periodic sediment removal using hydraulic flushing, hydraulic dredging, or dry excavation; 4) Provide large storage volume in the reservoir pool or in one or more upstream impoundments; and 5) Strategically place sediment in areas where its subsequent removal is facilitated, or where it minimizes interference with reservoir function (Fan, Jiahua, and Morris, Gregory, 2010). Sediment management on the North Fork Feather River above Lake Oroville in northern California is a good example of implementing multiple strategies to achieve sustainable conditions. The Pacific Gas and Electric Company (PG&E) has implemented a watershed-wide approach to sediment management in order to mitigate 30 years’ worth of sediment accumulation behind their three small hydropower dams in the watershed. Moving upstream from Lake Oroville, the dams are Poe, Cresta, and Rock Creek. These reservoirs receive flow from two branches of the watershed, the east branch and the west branch. Approximately 40 percent of sediment in the west branch is regulated by the upstream Almanor Reservoir, and most sediment delivered to the Rock Creek, Location map of watershed boundaries and reservoirs, North Fork Feather River Source: Fan, Jiahua, and Morris, Gregory, 2010 Cresta, and Poe Reservoirs comes from the eastern portion of the North Fork Feather River watershed. Because the accumulation of coarse sediment in the

6 reservoirs began to interfere with operation of PG&E’s power stations at the dams, an approach was developed to reduce upstream sediment yield, including through participation in a watershed management program; simultaneously, PG&E implemented remediation techniques at each of the dams, including sediment routing strategies aimed to create equilibrium in sediment accumulation along the chain of reservoirs. This ongoing approach is designed to mitigate adverse sedimentation effects while avoiding future occurrence of such effects. (Fan, Jiahua, and Morris, Gregory, 2010) How should sediments be disposed of? A common dilemma is what to do with sediment removed from behind a dam. The answer to this question depends entirely on the nature of the sediment, and the location of the reservoir from which it was removed. As mentioned in discussion of sediment management at the Elephant Butte Reservoir, sediment disposal is an ongoing issue. One option, if possible, is the placement of material within the watershed for natural distribution to downstream areas. The viability of returning sediment to the Aspen prepared the baseline conditions unconstrained watershed depends on the condition portion of an EIS/EIR to support a U.S. Army Corps of Engineers feasibility study of the surrounding environment, and its ability to for the removal of Matilja Dam, as well as absorb a new source of sediment. analysis of potential in-channel disposal Downstream Placement. Matilija Dam was sites for sediment removed from behind mentioned previously as an example of reservoir the dam. Aspen also prepared GIS sedimentation. Under the Matilija Dam Ecosystem vegetation mapping for the Ventura River corridor and Matilija Creek, in Restoration Project, one option that has been support of the dam removal effort. considered for disposal of dredged sediment is the placement of this material in locations in the riverbed. The disposal locations were strategically selected to be located outside of the active flow channel, but within the waterway limits such that the sediment would be flushed downstream during large storm events, or storms of the magnitude expected to occur every 20 to 50 years. Another option that has been considered for in-channel disposal is the use of upstream disposal sites, also strategically selected for flushing during large storm events. Under either option, the dam structure would be taken down while the reservoir’s sediment load is reduced; the dam has already been notched to allow spill-over flow for public safety, as described above. Issues associated with both upstream and downstream sediment placement are largely environmental. Six million tons of sediment would encompass a large area, even when divided into portions, and would potentially sit at the disposal sites for many years, replacing existing habitat and viewsheds, and potentially introducing a sulfurous odor, until the material is flushed downstream. Ultimately, the natural flushing of sediments would restore habitat for steelhead spawning and replenish beach sand where the Ventura River meets the Pacific Ocean. Canyon Infill. In mountainous regions, removed sediments may also be disposed of as infill in narrow Aerial view of Maple Canyon Sediment Disposal Site canyons. In some cases the material is placed to Source: LADPW eventually wash downstream again, while in others the placement is intended as permanent fill. One such disposal site located in the Angeles National

Forest is called the Maple Canyon Sediment Placement Site, or Maple Canyon SPS. Located 1.8 miles from the Big Tujunga Dam, this SPS was established in 1981 for disposal of sediments excavated from the reservoir. Thirty-two years later, the SPS currently holds approximately three mcy of excavated sediment encompassing an area of approximately 28 acres. After the Station Fire, more than one mcy of sediment accumulated in the Big Tujunga Reservoir, which now needs to be dredged in order to maintain operability of the dam and ensure flood hazard protection. The current proposal by LADPW is to remove 4.4 mcy from Big Tujunga Reservoir and transport it to the Maple Canyon SPS via trucks or a conveyor belt system; this placement would increase the footprint of Maple Canyon SPS by 29 acres. The Maple Canyon design includes underground drainage pipes and surface drainage facilities to direct stormwater runoff throughout the site and control erosion; debris basins at the upstream end of each underground drainage pipe captures sediment eroding from the natural drainages. (LADPW, 2013c) Construction Use. Sediments removed from behind a dam are typically comprised of varying sizes, including silt, sand, gravel, cobblestone, and larger materials. Once sorted, these materials may be suitable for construction use, often distributed through an existing quarry ideally located near the reservoir. Sediment removal from the Combie Reservoir, previously described in the context of contaminated sediments, includes the sorting of dredged sediments in order to export sand and gravel for construction uses (NID, 2009). Similarly, sediments removed under the Littelrock Dam Sediment Removal Project are proposed to be hauled to off-site commercial gravel pits located six miles north of the dam site in the community of Littlerock. This project includes long-term sediment removal Aspen prepared a joint EIS/EIR evaluating activities, with 540,000 cubic yards removed up- the Littlerock Sediment Removal Project front to restore the reservoir’s function and for the Palmdale Water District (CEQA capacity, and up to 40,000 cubic yards removed on Lead Agency). Aspen also assessed a slurry pipeline alternative for transportation of an annual basis after that, in order to maintain sediments, and assessed a Grade Control reservoir function. This project could also Design for the PWD. At the request of the eventually feed into other regional water banking Forest Service, Aspen prepared detailed projects such as the Antelope Valley East Kern work plans for biological resources. Water Agency’s eastside project (RWMG, 2006). Capping and Grade Fill. Depending on availability and local needs, sediments may also be disposed of by use in capping decommissioned landfills. Similarly, sediments may be used to raise the elevation of land depressions or eroded areas. In Los Angeles, sediment removed from Devil’s Gate Reservoir in 2012 is being temporarily placed at Johnson Field in Pasadena as part of the annual Interim Measures to manage sedimentation in the reservoir (LADPW, 2013a). Other flood controls projects remove sediment accumulated along levees or channels and use it to fortify the flood control facilities, such as the Sacramento Weir Sediment Removal Project on the Sacramento River, which removed accumulated sediment from the weir approach and used it to raise levee elevations and berm stability (DWR, 2009). Site-Specific Needs. As mentioned above, the viability of sediment disposal options depends entirely on site-specific environmental conditions, and the ability of the environment to receive an influx of material. For instance, in Pennsylvania, the state’s Department of Environmental Protection and a coalition of environmental groups called the Dredge Sediment Work Group have developed pilot projects to use sediments removed from the Delaware River to fill abandoned mine pits in the anthracite (coal-mining) region (Parker, 2002). Over the past decade, millions of dollars have been allocated towards such projects, with the goals of improving public safety by removing abandoned mine pits and improving water quality by reducing sediment load in the river. In addition, the option is cost- effective, as the Delaware River Port Authority pays to dredge and ship the sediment, and the federal

8 Mine Reclamation Program, paid for by the mining industry, provides funding for mine reclamation (Parker, 2002). Conclusion Active management of reservoir sedimentation is key to maintaining functionality of water infrastructure, and to meeting the three primary water management goals in California: water supply storage, flood hazard protection, and environmental health and function. Improving California’s water storage and conveyance infrastructure is necessary to ensure water supply reliability throughout the state, and requires that reservoir sedimentation issues are proactively addressed. As discussed in this article, reservoir sedimentation is often inherent to water supply storage projects and can be dealt with in many different ways, depending upon site-specific conditions and intended use and function of the facility. Particularly as we face increasing water storage and delivery challenges associated with population growth and climate change, sediment management will be essential to the functionality of water supply infrastructure. Contrary to traditional reservoir maintenance practices that assume a finite facility lifetime due to sedimentation, proactive and comprehensive sediment management efforts will not only extend the lifetime of our water supply infrastructure, but will also reduce operational efforts associated with removing large quantities of sediment from behind dams in order to rehabilitate or demolish them.

9 References Biba, Erin, 2012. What Happens When You Remove a Dam. Published in Popular Mechanics. December 11. [online]: http://www.popularmechanics.com/science/environment/geoengineering/what- happens-when-you-remove-a-dam-14845676. Accessed April 25, 2013. Byrne, et al., 2004. Changing Sedimentation Rates during the Last Three Centuries at Lake Elsinore, Riverside County, California. Submitted to Cindy Li, Associate Engineering Geologist, Regional Water Quality Control Board. February 12th. [online]: http://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_8/2006/ref469.p df. Accessed April 23, 2013. CCC (California Coastal Conservancy), 2010. Dam Removal Projects Funded by the Coastal Conservancy. [online]: http://scc.ca.gov/2011/06/10/dam-removal-projects-funded-by-the-coastal- conservancy/. Accessed April 25, 2013. DWR (California Department of Water Resources), 2009. Proposed Mitigated Negative Declaration and Draft Initial Study, Sacramento Weir Sediment Removal Project. March 12. [online]: http://www.dwr.water.ca.gov/floodmgmt/fmo/docs/Draft_Initial_Study- Sac_Weir_Sediment_Removal.pdf. Accessed April 26, 2013. Fan, Jiahua, and Morris, Gregory, 2010. Reservoir Sedimentation Handbook – Design and Management of Dams, Reservoirs, and Watersheds for Sustainable Use. December. [online]: http://reservoirsedimentation.com/. Accessed April 25, 2013. grandfathersmc (Grand Fathers M/C So Cal), 2013. Lake Elsinore. [online]: http://www.grandfathersmc.com/lake-elsinore.htm. Accessed April 26, 2013. LADPW (Los Angeles Department of Public Works), 2013a. Devil’s Gate Reservoir Sediment Removal and Management Project. [online]: http://ladpw.org/wrd/Removal/DevilGate/index.cfm?Project=DevilGate&site=wrd. Accessed April 25, 2013. _____, 2013b. Big Tujunga Reservoir Sediment Removal. [online]: http://ladpw.org/wrd/Removal/BigTujunga/index.cfm?Project=BigTujunga&site=wrd. Accessed April 26, 2013. _____, 2013c. Big Tujunga Reservoir Sediment Removal Project Description. [online]: http://dpw.lacounty.gov/wrd/removal/bigtujunga/Expanded_Project_Description.pdf. Accessed April 26, 2013. Matilija Coalition, 2002a. Removing Matilija Dam: Matilija Dam Spilling. [online]: http://www.matilija- coalition.org/spilling.htm. Accessed April 25, 2013. _____, 2002b. Timeline history of Matilija Dam. [online]: http://www.matilija-coalition.org/history.htm. Accessed April 26, 2013. NID (Nevada Irrigation District), 2009. Combie Reservoir Sediment and Mercury Removal – A Water Supply Maintenance Project. July. [online]: http://nidwater.com/wp- content/uploads/2012/04/Project_Description.pdf. Accessed April 25, 2013. Parker, Chris, 2002. Use of Delaware River sediment eyed for filling abandoned mines in anthracite region – DEP proposes a safe, inexpensive plan for a 2.2-acre mine pit near Tamaqua. January 31. [online]: http://articles.mcall.com/2002-01-31/news/3396761_1_mine-shaft-mine-land- mining-industry. Accessed April 23, 2013.

10 PBS (Public Broadcasting System), 2013. Hetch Hetchy Valley. [online]: http://www.pbs.org/nationalparks/media_detail/69/. Accessed April 26, 2013. Plascencia, Anthony, 2013. Photo published in the Ventura County Star, March 3,2013. Delayed plan to remove Matilija Dam near Ojai will get new studies. [online]: http://www.vcstar.com/news/2013/mar/03/new-studies-expected-for-matilija-dam-removal/. Accessed April 26, 2013. RWMG (Regional Water Management Group of the Antelope Valley Integrated Regional Water Management Plan), 2006. Antelope Valley Integrated Regional Water Management Plan. [online]: http://avwaterplan.org/. Accessed May 1, 2013. USDA (United States Department of Agriculture), 2009. Hydrology Specialist Report, Station Fire BAER Assessment – Los Angeles River Ranger District, Angeles National Forest. September 22. [online]: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5167071.pdf. Accessed April 25, 2013. Weiser, Matt, 2011. Sedimentation is a building problem in the West’s reservoirs. Published in High Country News, April 11. [online]: http://www.hcn.org/issues/43.6/muddy-waters-silt-and-the- slow-demise-of-glen-canyon-dam/sedimentation-a-building-problem-in-the-wests-reservoirs. Accessed April 25, 2013.