Misplaced Pages

#552447

78-591: The primary purpose of the Spring Creek Dam was to collect acid mine drainage from the old Iron Mountain Mine , which was heavily polluting Spring Creek and its tributaries. The dam was built in response to these pollutants that were contaminating the Sacramento River, the primary water supply for millions of Californians. Although the watershed is small in comparison to that of the Sacramento River,

156-689: A base metal-free effluent that can be discharged or further treated to reduce sulfate, and a metal sulfide concentrate with possible economic value. As an alternative, several researchers have investigated the precipitation of metals using biogenic sulfide. In this process, sulfate-reducing bacteria (SRB) oxidize organic matter using sulfate as terminal electron acceptor , instead of oxygen . Their metabolic products include bicarbonate produced by organic matter oxidation, which can neutralize water acidity, and hydrogen sulfide , which forms highly insoluble precipitates with many toxic metals. Although promising, this process has been slow in being adopted for

234-444: A cost of over US$ 1 million per mile, are included in the treatment process. Most water flowing directly from the mine has a pH level close to 1; the −3.2 pH mentioned earlier is only found in small amounts. Water is further diluted by natural flow in the tributaries and water diverted from nearby Clear Creek , however, the acidic water still requires treatment. Spring Creek is a southeast-flowing, 9-mile (14 km) long tributary of

312-492: A final listing of decisions after considering all the relevant comments that were received during the comment period. The Superfund docket contains the Hazard Ranking System score sheets for each proposed facility, a documentation record for each facility that details the information used to compute the score, information for any facility affected by particular statutory requirements or EPA listing policies, and

390-482: A laboratory) water on Earth. Several alternatives were considered for remediating this problem: In 1985, it was found that water seepage into the foundations of the Spring Creek Dam could possibly cause its collapse. Shortly after the discovery, a controversy over the irregular spills of mine toxins from the dam began in the 1990s. Two years later, in March 1992, an uncontrolled, unexpected spill of acidic water rushed from

468-539: A lime silo, a mixing tank and a settling pond. These systems are far less costly to build, but are also less efficient (longer reaction times are required, and they produce a discharge with higher trace metal concentrations, if present). They would be suitable for relatively small flows or less complex acid mine drainage. A calcium silicate feedstock, made from processed steel slag , can also be used to neutralize active acidity in AMD systems by removing free hydrogen ions from

546-784: A list of documents referenced in the documentation record. TOXMAP was a geographic information system (GIS) application from the Division of Specialized Information Services of the United States National Library of Medicine (NLM) that used maps of the United States to help users visually explore data from the EPA Superfund Basic Research Program and the Toxics Release Inventory . The application

624-574: A low pH, as is found in the acidic waters produced by pyrite oxidation. In the coal belt around the south Wales valleys in the UK highly acidic nickel-rich discharges from coal stocking sites have proved to be particularly troublesome. Acid mine drainage also affects the wildlife living within the affected body of water. Aquatic macroinvertebrates living in streams or parts of streams affected by acid mine drainage show fewer individuals, less diversity, and lower biomass. Many species of fish also cannot tolerate

702-565: A more detailed site inspection. EPA then uses the HRS to review any available data on the site to determine whether its environmental or health risks are enough to qualify the facility for a Superfund NPL cleanup. Generally, facilities with overall scores of 28.50 and greater on the HRS are eligible for the NPL. Another way facilities can be included in the NPL is if a state or territory designates one top-priority site within its jurisdiction, regardless of

780-424: A poorly soluble calcium sulfate layer onto the surface of limestone chips, binding the material and preventing further neutralization. Depending on the volume and flowrate of acid effluents to be neutralised and the scale of industrial installations, a commonly but more expensive commercial process for treating acid mine drainage is precipitation with lime in a high-density sludge (HDS) process. In this application,

858-414: A slurry of lime ( CaO – Ca(OH) 2 after hydration) is dispersed into a tank containing acid mine drainage and recycled sludge to increase water pH to about 9. At this pH, most toxic metals become insoluble and precipitate, aided by the presence of recycled sludge. Optionally, air can be injected in the tank to oxidize iron(II) and manganese(II) and assist in their precipitation. The resulting slurry

SECTION 10

#1732780869553

936-543: A source for effective drugs and new research, such as that conducted at the Center for Pharmaceutical Research and Innovation , suggests these extreme environments to be an untapped source for new discovery. This list includes both mines producing acid mine drainage and river systems significantly affected by such drainage. It is by no means complete, as worldwide, several thousands of such sites exist. National Priorities List The National Priorities List ( NPL )

1014-561: A stable dispersed state – effectively interrupting metal precipitation and reducing vulnerability of the material to armoring (formation of an impervious crust around material grains preventing their dissolution and decreasing their reactivity). Cation exchange processes have previously been investigated as a potential treatment for acid mine drainage. The principle is that an ion-exchange resin can remove potentially toxic metals (cationic resins), or chlorides, sulfates and uranyl sulfate complexes (anionic resins) from mine water . Once

1092-743: A variety of technical reasons. Many technologies exist for the treatment of AMD. With the advance of large-scale sequencing strategies , genomes of microorganisms in the acid mine drainage community are directly sequenced from the environment. The nearly full genomic constructs allows new understanding of the community and able to reconstruct their metabolic pathways. Our knowledge of acidophiles in acid mine drainage remains rudimentary: we know of many more species associated with ARD than we can establish roles and functions. Scientists have recently begun to explore acid mine drainage and mine reclamation sites for unique soil bacteria capable of producing new pharmaceutical leads. Soil microbes have long been

1170-577: A yellow-orange solid colloquially known as yellow boy . Other types of iron precipitates are possible, including iron oxides and oxyhydroxides, and sulfates such as jarosite . All these precipitates can discolor water and smother plant and animal life on the streambed, disrupting stream ecosystems (a specific offense under the Fisheries Act in Canada). The process also produces additional hydrogen ions, which can further decrease pH. In some cases,

1248-433: Is 795 feet (242 m) above sea level at full pool and spillway crest level. When at full pool, the reservoir holds 5,870 acre-feet (7,240  dam ) of water with a depth of roughly 184 feet (56 m). One spillway runs over the crest of the dam on the left bank of the canyon. The spillway is 25 feet (7.6 m) wide, able to accommodate a water flow of 5,260 cubic feet (149 m) per second. The outlet works of

1326-484: Is able to release up to 5,920 cubic feet (168 m) of water per second from the Spring Creek Reservoir, through a crest spillway and outlet works. The spillway begins on the left bank of the dam at elevation 795 feet (242 m), and drops roughly 184 feet (56 m) in vertical distance down the face of the dam into a stilling basin, before flowing into Spring Creek and into the Sacramento River. It

1404-438: Is an unprocessed raw material available in large quantities and the least expensive neutralisation agent, it can suffer from a number of disadvantages possibly limiting its applications. Indeed, small calcium carbonate grains of crushed limestone can be prone to the formation of a coating of gypsum ( CaSO 4 ·2H 2 O ) surrounded by a thin impermeable and protective film of less soluble Fe-Al hydroxysulfate. This coating

1482-481: Is considered a serious long-term environmental problem associated with mining. The chemistry of oxidation of pyrites, the production of ferrous ions and subsequently ferric ions, is very complex, and this complexity has considerably inhibited the design of effective treatment options. Although a host of chemical processes contribute to acid mine drainage, pyrite oxidation is by far the greatest contributor. A general equation for this process is: The oxidation of

1560-771: Is directed to a sludge-settling vessel, such as a clarifier . In that vessel, clean water will overflow for release, whereas settled metal precipitates (sludge) are recycled to the acid mine drainage treatment tank, with a sludge-wasting side stream. A number of variations of this process exist, as dictated by the chemistry of ARD, its volume, and other factors. Generally, the products of the HDS process also contain gypsum ( CaSO 4 ) and unreacted lime, which enhance both its settleability and resistance to re-acidification and metal mobilization. A general equation for this neutralisation process is: Less complex variants of this process, such as simple lime neutralization, may involve no more than

1638-517: Is diverted through the Spring Creek Tunnel, a conduit roughly 2.4 miles (3.9 km) long and 18.5 feet (5.6 m) in diameter. The Bureau of Reclamation gives a detailed report on the specifications of the generating plant: The powerplant houses two 13.8kV generators each rated at 100,000 kVA, .90 power factor, along with Francis turbines. Spring Creek Power Conduit conveys water from Whiskeytown Reservoir, located on Clear Creek, to

SECTION 20

#1732780869553

1716-476: Is iron-sulfide) within the surrounding rock and overburden generates acidity. Colonies of bacteria and archaea greatly accelerate the decomposition of metal ions, although the reactions also occur in an abiotic environment. These microbes, called extremophiles for their ability to survive in harsh conditions, occur naturally in the rock, but limited water and oxygen supplies usually keep their numbers low. Extremophiles known as acidophiles especially favor

1794-426: Is itself a copper-iron-sulfide and occurs with a range of other sulfides. Thus, copper mines are often major culprits of acid mine drainage. At some mines, acidic drainage is detected within 2–5 years after mining begins, whereas at other mines, it is not detected for several decades. In addition, acidic drainage may be generated for decades or centuries after it is first detected. For this reason, acid mine drainage

1872-504: Is only found inside and near the mine, as the average pH of water entering the Spring Creek Reservoir is 4.12. The Spring Creek Dam was later deemed "undersized" for the Spring Creek watershed, as the large flows of both natural drainage and acid mine drainage caused frequent uncontrollable spills at the dam. The spills contain many volatile components in acid mine drainage, which include the most acidic naturally occurring (i.e. not in

1950-401: Is quite different from limestone, the ability of calcium silicate to neutralize acid solutions is equivalent to limestone as evidenced by its CCE value of 90–100% and its relative neutralizing value of 98% . In the presence of heavy metals, calcium silicate reacts in a different way than limestone. As limestone raises the pH of the bulk solution, when heavy metals are present, precipitation of

2028-540: Is roughly 25 feet (7.6 m) wide and can carry 5,260 cubic feet (149 m) per second. The outlet works tunnel through the dam from an elevation much lower than that of the spillway; the conduit terminates at a culvert exit, a design commonly seen on storm drains but rarely seen on dams, at the base of the dam. The maximum capacity of the outlet works is 660 cubic feet (19 m) per second. Acid mine drainage Acid mine drainage , acid and metalliferous drainage ( AMD ), or acid rock drainage ( ARD )

2106-403: Is sometimes referred to in the literature as an armor (shield, encrustation, rim, rind…). When present, it passivates the limestone surface, preventing calcite dissolution and the further release of bicarbonate in solution. This might explain why at Cwm Rheidol in mid Wales , the positive impact of limestone application has been much less than anticipated because of the formation of

2184-505: Is the outflow of acidic water from metal mines and coal mines . Acid rock drainage occurs naturally within some environments as part of the rock weathering process but is exacerbated by large-scale earth disturbances characteristic of mining and other large construction activities, usually within rocks containing an abundance of sulfide minerals . Areas where the earth has been disturbed (e.g. construction sites or highway construction ) may create acid rock drainage. In many localities,

2262-581: Is the priority list of hazardous waste sites in the United States eligible for long-term remedial investigation and remedial action (cleanup) financed under the federal Superfund program. Environmental Protection Agency (EPA) regulations outline a formal process for assessing hazardous waste sites and placing them on the NPL. The NPL is intended primarily to guide EPA in determining which sites are so contaminated as to warrant further investigation and significant cleanup. As of 2022, 1333 sites are on

2340-539: The Central Valley Project Spring Creek Reservoir is the artificial lake formed behind the dam. The reservoir is used mostly for flood control storage, and is rarely filled to its 5,870 acre-feet (7,240  dam ) capacity. During the dry season, water from Spring Creek pools in a small, stagnant pond retained behind the dam, depositing contaminated sediment and acidic mine waste in the reservoir space. When flows from

2418-532: The Comprehensive Environmental Response, Compensation, and Liability Information System (CERCLIS). Then, either EPA or the state in which the potentially contaminated facility is located will conduct a preliminary assessment, which decides if the facility poses a threat to human health and/or the environment. If the preliminary assessment shows the possibility of contamination, EPA (or the state under agreement with EPA) will conduct

Spring Creek Dam - Misplaced Pages Continue

2496-474: The River Neath at Ynysarwed . Although abandoned underground mines produce most of the acid mine drainage, some recently mined and reclaimed surface mines have produced ARD and have degraded local ground-water and surface-water resources. Acidic water produced at active mines must be neutralized to achieve pH 6–9 before discharge from a mine site to a stream is permitted. In Canada, work to reduce

2574-634: The Sacramento River , receiving water from approximately 16 square miles (41 km) of land. The creek begins in the Klamath Mountains above the Sacramento River drainage, and flows in a generally south-east direction before turning south and sharply west into the Spring Creek Reservoir. From the reservoir, it continues due west until it empties directly into an arm of the Keswick Reservoir. The creek never actually runs by

2652-552: The Shasta Dam , upstream on the Sacramento River , are sufficient to flush contaminated water away, water held in the reservoir is released through the outlet works into the Keswick Reservoir and the Sacramento River. Despite this operation strategy, the reservoir was eventually deemed inadequate for the watershed, and can be filled to capacity by a single heavy storm event. Uncontrollable spills frequently poured into

2730-524: The coal mine discharges in Pennsylvania have pH under 5. However, a portion of mine drainage in both the bituminous and anthracite regions of Pennsylvania is alkaline, because limestone in the overburden neutralizes acid before the drainage emanates. When the pH of acid mine drainage is raised past 3, either through contact with fresh water or neutralizing minerals, previously soluble iron(III) ions precipitate as iron(III) hydroxide ,

2808-476: The water table , so water must be constantly pumped out of the mine in order to prevent flooding. When a mine is abandoned, the pumping ceases, and water floods the mine. This introduction of water is the initial step in most acid rock drainage situations. Tailings piles or ponds, mine waste rock dumps , and coal spoils are also an important source of acid mine drainage. After being exposed to air and water, oxidation of metal sulfides (often pyrite , which

2886-684: The 1980s to treat acid mine drainage generated by the abandoned coal mines in Eastern Appalachia . Generally, the wetlands receive near-neutral water, after it has been typically neutralized by a limestone-based treatment process. Metal precipitation occurs from their oxidation at near-neutral pH, complexation with organic matter, precipitation as carbonates or sulfides. The latter results from sediment-borne anaerobic bacteria capable of reducing sulfate ions into sulfide ions. These sulfide ions can then bind with heavy metal ions, precipitating heavy metals out of solution and effectively reversing

2964-558: The Iron Mountain Mine closed, but pollution continued and still continues, and in 1983, the Iron Mountain Mine was listed on the National Priorities List . The Iron Mountain Mine is known for having the most acidic naturally found water content on Earth, with samples having up to a −3.6 pH value when tested in the early 1990s, which is roughly 100 times the acidity of battery acid . However, this pH value

3042-431: The Sacramento River during floods, through the crest spillway of the dam, which lacks gates. As a result, numerous fish kills have occurred during these sudden releases of contaminants, a major one of which was in 1969. Due to this consistent acid pollution from the reservoir, most large fish spawn downstream of Red Bluff Diversion Dam , a dam also on the Sacramento River near Red Bluff, California . The Spring Creek Dam

3120-407: The Sacramento River from Spring Creek. Both streams run east into the river. The power plant was completed and began operations in 1964, with a capacity of 150,000 kW. The capacity was later upgraded to 180,000 kW. The plant is a peaking power plant with two separate generators, generating power for operations and distributing excess power to the local power grid. Water from Whiskeytown Lake

3198-628: The Sacramento River upstream of Spring Creek. The stream receives contaminated runoff from the Minnesota Flats Tailing Pile, but is not nearly as polluted or acidic as Spring Creek. Another stream, Rock Creek, rises in three forks and flows east to meet the Sacramento River downstream of Spring Creek and the Keswick Reservoir. The Spring Creek Dam is 196 feet (60 m) high, 1,110 feet (340 m) long along its crest, and 1,040 feet (320 m) thick at its base. Its crest stands 816 feet (249 m) above sea level. The reservoir

Spring Creek Dam - Misplaced Pages Continue

3276-479: The Spring Creek Powerplant. The Spring Creek power conduit varies in diameter between 5.64 metres (18.5 ft) and 5.18 metres (17.0 ft) and is about 4.8 km (3.0 mi) in length. The power conduit consists of Tunnels No. 1 and No. 2, and Rock Creek Siphon. Twin penstocks take off from Tunnel No. 2 leading to the powerplant. – U.S. Bureau of Reclamation , Trinity River Division of

3354-401: The Spring Creek Reservoir, but since its basin lies far from the mine, it receives no acid mine drainage. The inflow and outflow from the reservoir are highly erratic, ranging from 0 cubic feet (0 m) per second to roughly 225 cubic feet (6.4 m) per second in a particular 10-day period from March to April. Flat Creek, a small southeast-flowing stream, rises in two forks and empties into

3432-730: The United Kingdom, many discharges from abandoned mines are exempt from regulatory control. In such cases the Environment Agency and Natural Resources Wales working with partners such as the Coal Authority have provided some innovative solutions, including constructed wetland solutions such as on the River Pelenna in the valley of the River Afan near Port Talbot and the constructed wetland next to

3510-484: The United States. This list is Appendix B of the National Contingency Plan, known as the "National Priorities List." Hazardous waste sites become eligible for CERCLA/Superfund cleanup when EPA receives a report of a potentially hazardous waste site from an individual, state government, or responsible federal agency. EPA will first enter the potentially contaminated facility into a database known as

3588-416: The bulk solution, thereby increasing pH. As the silicate anion captures H ions (raising the pH), it forms monosilicic acid (H 4 SiO 4 ), a neutral solute. Monosilicic acid remains in the bulk solution and play many roles in correcting the adverse effects of acidic conditions. In the bulk solution, the silicate anion is very effective in neutralizing H cations in the soil solution. While its mode-of-action

3666-458: The calcium silicate aggregates , as silicic acid species are adsorbed onto the metal hydroxide surface, the development of silica layers (mono- and bi-layers) lead to the formation of colloidal complexes with neutral or negative surface charges. These negatively charged colloids are electrostatically repelled by each other (as well as with the negatively charged calcium silicate granules). The sequestered metal colloids are stabilized and remain in

3744-500: The capability of the Sacramento River to flush away pollutants from the mine. Acid mine drainage flowed, unfettered, down Spring Creek directly into the Keswick Reservoir, depositing contaminated sediment and turning a portion of the water a rusty red shade. Previously, the water would have continued down the creek into the river, and flushed to the Pacific Ocean . The pooling of the water, however, made it extremely difficult for

3822-438: The concentrations of iron hydroxides in yellow boy are so high, the precipitate can be recovered for commercial use in pigments. Many acid rock discharges also contain elevated levels of potentially toxic metals, especially nickel and copper with lower levels of a range of trace and semi-metal ions such as lead , arsenic , aluminium , and manganese . The elevated levels of heavy metals can only be dissolved in waters that have

3900-472: The contaminants are adsorbed , the exchange sites on resins must be regenerated, which typically requires acidic and basic reagents and generates a brine that contains the pollutants in a concentrated form. A South African company that won the 2013 IChemE award for water management and supply (treating AMD) has developed a patented ion-exchange process that treats mine effluents (and AMD) economically. Constructed wetlands systems have been proposed during

3978-424: The current dam site, from 1879 to the 1960s. The mine extracted iron ore , silver , gold , copper sulfide ore, and pyrite from a rock formation dating to approximately 780,000 years ago. The potential of a mine at the site was discovered in 1860, when two men, surveyor William Magee and settler Charles Camden, discovered an extensive iron ore deposit along one of the tributaries of Spring Creek. In 1879, silver

SECTION 50

#1732780869553

4056-414: The dam are located at the base, and can accommodate a water flow of 660 cubic feet (19 m) per second. The Spring Creek Powerplant downstream of the dam generates up to 180,000 kilowatts . The Spring Creek Powerplant is located at the base of the Spring Creek Dam, and is actually supplied by flow from Whiskeytown Lake . The lake, formed by Whiskeytown Dam, is on Clear Creek, a drainage downstream along

4134-418: The dam down Spring Creek. This spill heavily contaminated the Keswick Reservoir and threatened the water supply of Redding, California . Despite the fact that the region was suffering from a drought, 77,000 acre-feet (95,000  dam ) of water were released from Shasta Lake , which was only half full, to dilute the pollution. The loss of the water, which was badly needed by Central Valley agricultural users,

4212-494: The dam, both physically and biologically, arose in the 1990s. Emergency releases from Shasta Lake , often in the value of thousands of acre feet of water, have occurred from time to time to dilute massive acid spills from the Spring Creek drainage. The Iron Mountain Mine, the most productive copper mine in California in at least one point along its history, operated along the banks of two Spring Creek tributaries, upstream from

4290-869: The effects of acid mine drainage is concentrated under the Mine Environment Neutral Drainage (MEND) program. Total liability from acid rock drainage is estimated to be between CA$ 2 billion and CA$ 5 billion . Over a period of eight years, MEND claims to have reduced ARD liability by up to CA$ 400 million , from an investment of CA$ 17.5 million . Often, limestone rocks or appropriate calcareous strata that could contribute to neutralize acid effluents are lacking, or insufficiently accessible (too short contact time with acidic waters flowing too fast, too low specific surface area , insufficient contact…), at sites affected by acidic rock drainage. In such cases, crushed limestone can be dumped on site as neutralizing agent. However, although limestone

4368-502: The effluent from constructed wetland receiving near-neutral water will be well-buffered at 6.5–7.0 and can readily be discharged. Some of metal precipitates retained in sediments are easily oxidised and remobilised when exposed to atmospheric oxygen (e.g., copper sulfide or elemental selenium ), and it is very important that the wetland sediments remain largely and permanently submerged to maintain them insoluble and immobile. Prolonged droughts caused by climate warming might compromise

4446-441: The entire process. The attractiveness of a constructed wetlands solution lies in its relative low cost. They are limited by the metal loads they can deal with (either from high flows or metal concentrations), though current practitioners have succeeded in developing constructed wetlands that treat high volumes (see description of Campbell Mine constructed wetland ) and/or highly acidic water (with adequate pre-treatment). Typically,

4524-437: The last major sea level rise , and constitutes a similar environmental hazard . Historically, the acidic discharges from active or abandoned mines were called acid mine drainage, or AMD. The term acid rock drainage, or ARD, was introduced in the 1980s and 1990s to indicate that acidic drainage can originate from sources other than mines. For example, a paper presented in 1991 at a major international conference on this subject

4602-444: The liquid that drains from coal stocks, coal handling facilities, coal washeries, and coal waste tips can be highly acidic, and in such cases it is treated as acid rock drainage. These, combined with reduced pH, have a detrimental impact on the streams' aquatic environments. The same type of chemical reactions and processes may occur through the disturbance of acid sulfate soils formed under coastal or estuarine conditions after

4680-511: The list, and 43 sites have been proposed for listing. 448 sites have been deleted from the list. The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), also known as "Superfund", requires that the criteria provided by the Hazard Ranking System (HRS) be used to make a list of national priorities of the known releases or threatened releases of hazardous substances, pollutants, or contaminants in

4758-558: The list. The primary cleanup goal is to reduce the risks to human health and human health in the environment through a combination of cleanup, engineered controls like caps and site restrictions such as groundwater use restrictions. A secondary goal is to return the site to productive use as a business, recreation or as a natural ecosystem. Identifying the intended reuse early in the cleanup often results in faster and less expensive cleanups. EPA's Superfund Redevelopment Program provides tools and support for site redevelopment. The public has

SECTION 60

#1732780869553

4836-409: The low pH levels of abandoned mines. In particular, Acidithiobacillus ferrooxidans is a key contributor to pyrite oxidation. Metal mines may generate highly acidic discharges where the ore is a sulfide mineral or is associated with pyrite. In these cases the predominant metal ion may not be iron but rather zinc , copper , or nickel . The most commonly mined ore of copper, chalcopyrite ,

4914-416: The mine. The acid mine drainage found in the creek is actually carried in by two smaller tributaries, which are Boulder Creek and Slickrock Creek. The former stream runs southeast from the north side of Iron Mountain Mine to Spring Creek, while the latter stream drains the south side of the mine and also flows southeast into Spring Creek. South Fork Spring Creek is a small tributary that flows west and north

4992-601: The opportunity to comment on facilities that are proposed to be added to the National Priorities List. EPA publishes notices in the Federal Register listing the proposed facilities. The agency will consider all comments received within 60 days after publication in the Register. The complete set of comments are available to the public one week following the close of the comment period. EPA makes

5070-506: The pH and maintains the solubility of the ferric ion. Water temperatures as high as 47 °C (117 °F) have been measured underground at the Iron Mountain Mine , and the pH can be as low as −3.6. Organisms which cause acid mine drainage can thrive in waters with pH very close to zero. Negative pH occurs when water evaporates from already acidic pools thereby increasing the concentration of hydrogen ions. About half of

5148-402: The pollutants to be removed. From 1955 to 1962, open pit mining began on the site. At its peak, the mine discharged 5 tons of iron , 650 pounds (290 kg) of copper , and 1,800 pounds (820 kg) of zinc into the stream per day. By then, the water flowing down the drainage was so contaminated that it necessitated the construction of a holding dam, the Spring Creek Dam. Spring Creek Dam

5226-532: The pollution. Among the macroinvertebrates, certain species can be found at only certain levels of pollution, while other species can be found over a wide range. In a mining setting it is leading practice to carry out a geochemical assessment of mine materials during the early stages of a project to determine the potential for AMD. The geochemical assessment aims to map the distribution and variability of key geochemical parameters, acid generating and element leaching characteristics. The assessment may include: In

5304-523: The poorly soluble metal hydroxides is accelerated and the tendency for an impermeable metal hydroxide coating, termed armoring , to form on limestone grains surface increases significantly. Limestone grains become coated by a rind of gypsum encapsulated itself in a thin external film of impermeable and protective Fe-Al hydroxysulfate. Armoring slows the CaCO 3 dissolution and prevents the limestone grains from releasing additional alkalinity in solution. In

5382-525: The problems at the Iron Mountain Mine in California. ...release of this waste resulted in virtual elimination of aquatic life in many of the creeks surrounding the Iron Mountain Mine site. ...work is continuing on what is possibly the largest and most difficult acid mine drainage problem in the United States. -P. Aarne Vesilind. Controlling Environmental Pollution , 2005 The construction of Shasta Dam and its afterbay (regulating downstream dam), Keswick Dam, in 1943 and 1950, respectively, severely impaired

5460-670: The proper functioning and the safety of some constructed wetlands if during extremely hot summer period water supply decreases and evaporation accelerates causing them to dry up. An example of an effective constructed wetland is on the Afon Pelena in the River Afan valley above Port Talbot where highly ferruginous discharges from the Whitworth mine have been successfully treated. Most base metals in acidic solution precipitate in contact with free sulfide, e.g. from H 2 S or NaHS. Solid-liquid separation after reaction would produce

5538-533: The site's HRS score. The last way a site can be included in the NPL is if it meets the following three requirements: EPA may delete a final NPL site if it determines that no further response is required to protect human health or the environment. Also, sites where a remediation was completed through the Superfund program are typically deleted from the list. As of 2022, 1333 sites are on the list, and 48 sites have been proposed for listing. 443 sites were deleted from

5616-412: The stream is among the most polluted and acidic in the world. The dam and reservoir, along with other treatment structures built at and below the mine, have successfully reduced the dry weather pollution of Spring Creek by up to ninety-five percent. Problems, though, still occur mainly in the form of large uncontrolled spills from the reservoir. Several concerns about the structural integrity and safety of

5694-426: The sulfide to sulfate solubilizes the ferrous iron ( iron(II) ), which is subsequently oxidized to ferric iron ( iron(III) ): Either of these reactions can occur spontaneously or can be catalyzed by microorganisms that derive energy from the oxidation reaction. The ferric cations produced can also oxidize additional pyrite and reduce into ferrous ions: The net effect of these reactions is to release H , which lowers

5772-575: Was also discovered at the site, and the mine was begun. The ownership was transferred to Mountain Mines Ltd., a London company, in 1894. At the very end of the 19th century, Iron Mountain Mine took blames for several fish kills in the Sacramento River . Nevertheless, mining activity continued, and by 1928, 600 tons of ore were being extracted from the site per day. The still continuing problem of Iron Mountain Mine runoff has once been described as: ...[acid mine drainage is] most vividly illustrated by

5850-512: Was begun in 1961, when a company named Gibbons and Reed was awarded the contract. The clearing operations began in July of that same year, and the dam was officially dedicated by the Bureau of Reclamation on September 12, 1961. Construction of the dam began on October 20, 1961, with the placing of the dam embankment, which at least partially consists of acidic sediment dredged from Spring Creek. Riprap

5928-420: Was estimated at US$ 18 million. A water treatment plant was built on a site named Minnesota Flats near the Iron Mountain Mine, using lime to balance the pH of the acid mine drainage. Water is also diverted from Slickrock Creek to the treatment site. Altogether, over 95 percent of toxins in the water are removed by the treatment process. Roughly 8.5 miles (13.7 km) of specialized acid-resistant pipeline, with

6006-476: Was laid on the upstream face of the dam beginning November 9 of that year. In 1962, a series of labor strikes impacted communities in the Central Valley, also affecting construction of the dam, which was temporarily halted on May 3 of that year. After work restarted on June 26, pervious core material for the dam was soon out of supply, so impervious material was used to complete the dam core. Eventually,

6084-633: Was titled: "The Prediction of Acid Rock Drainage – Lessons from the Database". Both AMD and ARD refer to low pH or acidic waters caused by the oxidation of sulfide minerals , though ARD is the more generic name. In cases where drainage from a mine is not acidic and has dissolved metals or metalloids , or was originally acidic, but has been neutralized along its flow path, then it is described as "neutral mine drainage", "mining-influenced water" or otherwise. None of these other names have gained general acceptance. Sub-surface mining often progresses below

#552447