Water: Nonpoint Source Success Stories
Grant County's Royal John Mine -
A Full-Scale Site Reclamation Project
The Royal John Mine, located in the Gila National Forest on the headwaters of the Mimbres River, produced lead, zinc, and silver ores enriching a variety of owners for over 100 hundred years, until the 1960s.
This portion of the Gila Forest (about 25 miles east of Silver City, New Mexico) is the dominant drainage for a large closed desert basin in Grant, Sierra, Hidalgo, and Luna counties in southwestern New Mexico. Drainage is through Cold Creek to the Gila River. The mine area consists of several buildings, walls, and foundations, including the mine portal and two acres of waste rock and tailings. Present, too, are typical mine yard dumps and refuse materials.
In the early 1990s, a single open portal still emitted a perennial metal-laden flow, and approximately two acres of mine waste remained, bisected by a six-foot-deep incised channel. The Forest Service monitored the contaminated water flowing from the open mine portal, and New Mexico's nonpoint source staff used x-ray fluorescent technology to document the transport of the polluted water and sediment from the mine and mill to sites located more than three miles downstream.
Water samples routinely contained copper (46.0 ppm), zinc (16.0 ppm), aluminum (4.5 ppm), iron (2.4 ppm), and lead (1.0 ppm). These concentrations exceed the applicable state standards for all five metals. In addition, turbidity measurements in the water were quite high, over 1,000 nephelometer turbidity units (NTUs), and the water was also slightly acidic (pH5). Initial attempts to divert this perennial drainage away from the mine waste as it emerged from the portal failed; the material beneath it was too porous.
Installing best management practices
Having determined that only a full-scale mine reclamation project would protect the Gila River and Cold Creek, the Nonpoint Source Section of New Mexico's Environment Department with a 319 grant and with other state and federal agencies as partners began the installation of the critical best management practices (BMPs). By project's end, they had installed an adequately sized sediment control basin downslope of the waste materials and reconstructed the central drainage channel.
The reconstructed drainage (some 300 feet in length) was lined with a geotextile fabric to reduce infiltration during runoff events, then meticulously armored by hand with limestone riprap. The drainage channel was designed with as much sinuosity as the physical constraints of the site allowed to provide for reduced slope. The deeply incised waste piles were graded back toward the adjacent undisturbed slopes.
Project managers constructed an energy dissipator apron along the last 50 feet of this channel that connects into the sediment control basin. The slopes adjacent to the channel were graded to blend with the surrounding undisturbed land area. This topographic configuration was then covered with 12 inches of topsoil and growth media, mainly biosolids obtained from local stock tanks, and hand seeded with 40 pounds per acre of dry-season range grass. The entire reclaimed area was mulched with wheatstraw to retain soil moisture, and this material was then crimped into place with bulldozer cleats.
The perimeter of the reclaimed area was fenced to reduce grazing impacts. The perennial seep from the mine portal created a saturated zone along the south side of the project area, covering approximately 1,500 square feet. This entire area was hand planted with emergent wetland vegetation. The fringes of the wetland and the sides of the reconstructed channel were planted with woody riparian species. All of this work was completed in late 1994 and early 1995.
In March 1996, an additional 600 willows were planted in the reclaimed riparian enclosure at the Royal John. In April 1996, a french drain consisting of a trench lined with clay and filled with limestone was constructed to divert mine drainage away from an old mill building. This drain also expands the wetted area associated with the previously reconstructed stream channel. In July 1996, the local Boy Scout troop and parents of some of the boys planted 300 willows along the full length of the restructured channel, bringing the total to about 1,100 willows. In September 1996, staff of the New Mexico Environment Department's Silver City field office, along with members of the Friends of Cold Creek Watershed Association, spread native grass seed and mulch at the Royal John Mine site.
After the initial reclamation, the Silver City field office assumed management responsibility for the Hot/Cold Springs Watershed project of which the Royal John reclamation was a part. Members and parents of a local Boy Scout troop planted additional willows in July 1996. Other adults have also planted willows as part of their community service work (in a partnership arranged though a local district attorney's office). Staff of the Silver City field office participated in and coordinated these efforts.
Mine wastes stabilized
The first sediment control basin downslope of the wastes received an effective test when two severe storm events occurred only two weeks apart shortly after its installation. During both events, turbidity values exceeding 1,000 NTUs were measured entering the sediment basin; however, the effluent discharged from the basin ranged from 20 to 25 NTUs during these intense storm events. Clearly, this BMP worked as intended. As of early May 1995, the grass cover on the reclaimed area was over 75 percent, and 95 percent of the riparian pole plantings were sprouting leaves. The willow plantings of 1996 improved the site further by establishing riparian vegetation in the upper portion of the enclosure and supplementing the willows in the lower portion.
Sediment from upstream is creating a substrate in the channel, returning it to a state more conducive to the growth of a biotic community. In addition, the saturated zone created by the seep from the mine portal is now a wetland. The mine wastes are stabilized and protected from further erosion. The french drain installed in 1996 is serving its purpose, diverting water away from the old mill and expanding the wetted area of the channel. Cold Creek, the drainage through and below the mine site, has been transformed at the Royal John site from a gully deeply incised into mine wastes, with no riparian vegetation, into a stable, meandering channel lined with hundreds of willows.
|CONTACT: Dennis Slifer
New Mexico Nonpoint Source Pollution Program
New Mexico Environment Department
Treating Acid Mine Drainage from the Oro Fino Mine
In operation from 1880 through the early 1900s, the Oro Fino Mine is located about 10 miles north of Red River, New Mexico, on the headwaters of Bitter Creek, a tributary of the Red River in the Carson National Forest in Taos County, northern New Mexico. Late stage hydrothermal alteration from the area rocks was responsible for the formation of the gold ores and a broad suite of sulfide minerals, especially pyrite.
During the early years, mine operators extracted free gold primarily by mercury amalgamation. The resulting rock drainage and increased metals content in runoff are characteristic nonpoint source pollution problems found along these reaches of Bitter Creek. A combination of surface runoff, seep discharge, and groundwater drainage moves through the Oro Fino Mine wastes and emerges as acid mine drainage.
Tracking the source
Watershed assessments delineate the stream site at which the acidic, metal-laden waters enter Bitter Creek, some metal precipitation occurs, and upstream high quality waters are suddenly degraded. The source of this pollution is a seepage zone in pyritic waste rock piles a few yards northwest of the mine portal. Monitoring data collected from the seep in July 1992 reveal water quality standards violations for seven metals, pH, conductivity, and total dissolved solids (see Table 1). After the Oro Fino site was mined and abandoned, the surface waste and tailings piles started to deteriorate and the mine portal collapsed. The main mine workings are fully flooded.
Partners approach a solution
Primary financial support for the Oro Fino Mine project came from Amigos Bravos, a Taos-based river conservation group. The Questa Ranger District, Carson National Forest, provided labor and logistic support, and additional labor and subsequent monitoring were accomplished by the New Mexico Environmental Department's nonpoint source staff, with funding from 319 grants.
In September 1993, the project installed a bench-scale anoxic alkaline drain passive treatment system to treat the acidic metal-loaded mine drainage. An L-shaped trench, 12 to 14 feet long, 2 feet wide, and 4 to 5 feet deep was dug into the poorly consolidated tailings and positioned to intercept the obvious area of seepage, where the tailings were well saturated. The trench was filled with 12 cubic yards of crushed cobble-sized limestone (2 to 4 inches) that was 88 percent CaCO.
Several layers of 20 millimeter polyethylene liner were installed as a dilution barrier on top of the limestone. The treatment system was capped with 14 to 20 inches of compacted clay, and a resurgence pool (about4 feet deep) was built downgrade of the drain. The acid mine drainage passes through the alkaline drain, fills the resurgence pool, and flows on toward a developing wetland for secondary treatment before it enters Bitter Creek.
|Table 1. - Sampling results at the Oro Fino Mine on Bitter Creek in New Mexico.|
|MEASUREMENT AFTER 3 YEARS
|Aluminum||89.0 mg/L**||0.7 mg/L||2.2 mg/L*|
|Cadmium||0.005 mg/L||< 0.001 mg/L||< .0001 mg/L|
|Copper||0.29 mg/L*||0.01 mg/L||< 0.01 mg/L|
|Iron||990.0 mg/L*gw||7.0 mg/L*gw||93.0 mg/L*gw|
|Lead||< 0.005 mg/L||< 0.1 mg/L||< 0.001 mg/L|
|Manganese||4.2 mg/L*gw||1.8 mg/L*gw||2.5 mg/L*gw|
|Molybdenum||2.4 mg/L**||< 0.1 mg/L||0.04 mg/L|
|Nickel||1.5 mg/L*gw||0.1 mg/L||0.2 mg/L|
|Zinc||1.5 mg/L||0.08 mg/L||0.08 mg/L|
|Sulfates||3,675.0 mg/L||647 mg/L||790.0 mg/L|
|Conductivity||3,668.0 µmhos*||1,100.0 µmhos*||1,238.0 µmhos|
|TTDS||5,642.0 mg/L*gw||1,028.0 mg/L*gw||1,310.0 mg/L*gw|
The above results for metals are for the dissolved phase.
|* These values violate New Mexico Water Quality Control Commission standards for surface water.|
|*gw These values violate standards for groundwater.|
|** These values violate standards for both surface water and groundwater.|
After the anoxic alkaline drain was installed, the quality of the acidic water emerg- ing from the site wastes improved dramatically. The results of monitoring samples taken at the resurgence pool before and after effluent passes through the drain are shown in Table 1.
These results show that dramatic improvement continues even four years after the drain was installed with little or no maintenance. The slight decrease in the drain's effectiveness indicated by the September 1996 sampling can be attributed to off-road vehicles trespassing on the site. The trespassers made tire ruts that diverted a small amount of acid drainage from the control seep (left untreated to measure local improvement) into the finishing pool. Livestock and wildlife had also been accessing the pool, eroding the surrounding berm. Some ruts were filled in and other minor repairs performed at the site, but further repairs and the installation of a barrier are necessary to prevent future trespassing.
This project reinforces the value of careful observation and water quality testing before best management practices are installed. Second, the relatively small size of the affected area was also helpful; as the drainage was obviously seeping through the tailings, it was possible to position the drain precisely for maximum effectiveness.
A third lesson is that continued mainte- nance of the site is needed to ensure the highest efficiency. Finally, project staff will find it useful to look at methods adopted in other parts of the country. The anoxic alkaline drain was initially used to treat acid mine drainage from coal mines in the eastern part of the United States.
This project successfully reduced the impacts of acid mine drainage on Bitter Creek. Improved water chemistry in Bitter Creek helps reduce the impact of nonpoint source pollutants on the main stem of the Red River system and benefits wildlife at the site and downstream.
|CONTACT: Dennis Slifer
Nonpoint Source Pollution Program
New Mexico Environment Department