Klondyke Tailings Project
The Klondyke Tailings Project WQARF (site) is located on the north bank of Aravaipa Creek, approximately 4.5 miles upstream of the Aravaipa Canyon Wilderness Area in Arizona. The site is located approximately two miles north of the town of Klondyke in Section 6, Township 7 South, Range 20 East. The boundaries of this site are irregular and the site boundaries are defined by the extent of the soil contamination above the residential soil remediation level for lead of 400 milligrams per kilogram (mg/kg). The site is comprised of two piles of mine tailings. The soil is between and adjacent to these piles and several surrounding properties.
In February 2015, ADEQ announced the availability of the Feasibility Study (FS) work plan. During the FS, ADEQ is evaluating additional remediation alternatives and technologies available for the site. ADEQ is still considering removal actions near the residences on three properties near the site.
In March 2015, ADEQ and their contractor, AMEC Foster Wheeler, began work on consolidating the downstream tailings pile in preparation for capping.
A community advisory board (CAB) has been formed for the site. Details of meeting agendas and minutes can be viewed at the ADEQ website. These meetings are open to the public. ADEQ distributes fact sheets and public notices to the nearby community when significant events occur. Fact sheets are sent to residents in the community involvement area and distributed at the site repository at the U.S. Bureau of Land Management (BLM) ranger station in Klondyke.
1870 - 1950: From the 1870s through the 1950s, lead, zinc, copper, silver, and gold mining was conducted in the Klondyke area of the Aravaipa Mining District. In 1948, the Athletic Mining Company constructed a flotation mill next to Aravaipa Creek that operated until about 1958 and generated, in part, the tailings at the site. Other possible sources are being investigated.
1993: In March, a complaint concerning erosion and runoff from the tailings pile was filed with ADEQ, and an investigation began. The results of that investigation revealed high levels of lead and arsenic in the tailings piles and surrounding soils and acidic runoff emanating from the site.
1997: In October, ADEQ received an Arizona Water Protection Fund Grant to conduct a preliminary investigation, compile existing data, and evaluate possible remedial alternatives at the site. The U.S. Fish and Wildlife Service conducted fish tissue sampling and analysis of fish in Aravaipa Creek at two sites within Nature Conservancy property. The results of that investigation revealed elevated levels of arsenic, cadmium and lead in fish tissue, though not at levels that threatened native fish species.
1998: In September, the site was placed on WQARF Registry with an eligibility and evaluation score of 69 out of a possible 120.
1999: ADEQ contracted with United Research Services Corporation (URS) to conduct the remedial investigation (RI) for the site.
2001: In July, fifteen private wells in the Klondyke area were sampled. No drinking water standards were exceeded in any of the wells tested. Results indicated very good water quality. In December, samples of tailings were collected and analyzed to assess the long-term potential for generating and releasing acidity and metals from the tailings as a result of storm water runoff. The results of the Phase I investigation indicate high levels of stored acidity in the two tailings piles. .
2001 2002: Magnetic and electromagnetic geophysical surveys were conducted to identify the possible presence of buried drums, tanks, and piping that may contain contaminants.
2002 - 2003: Aerial photography and topographic mapping were conducted to provide the technical background necessary to conduct a geomorphic and floodplain analysis of the site. The 100-year and the 500-year flood plains were delineated. Soil sampling was conducted for bioavailability testing. The results of that testing indicate a wide range of bioavailability for lead-contaminated soils and tailings and a low level of bioavailability for arsenic in soils and tailings. Biological, archeological and cultural resource surveys were also completed.
2005 - 2006: ADEQ completed one early response action (ERA) at the site. During the ERA, ADEQ excavated 11 geophysical targets previously identified during the geophysical survey. No buried tanks, drums or pipelines requiring removal were found. During the ERA, a small amount of laboratory reagents still present at the site were also removed. Also during the ERA, ADEQ conducted minor earth moving repairs such as repairing berms around the tailings piles and correcting drainage problems to contain storm water runoff on the tailings piles.
ADEQ continued with the RI activities including soil sampling of the entire site to determine the extent of soil contamination. Sampling results indicated that adjacent properties also needed to be evaluated. Over 1,700 soil samples were collected and analyzed using X-ray fluorescence. Samples were collected from the surface, a depth of six inches, a depth of one foot and a depth of two feet. The RI also included sediment sampling in Aravaipa and Laurel Creeks both upstream and downstream of the site.
In addition, four groundwater monitor wells were installed at the site and quarterly monitoring and analyses of groundwater samples from these wells indicates no impacts to the groundwater beneath the site from metals above Aquifer Water Quality Standards (AWQS).
A significant flood event occurred in Aravaipa and Laurel Creeks during late July and early August. ADEQ continued to evaluate ERA activities at the site. Two ERA alternatives were proposed in a 2004 report to begin to consolidate the tailings at the site.
2007: For the RI, ADEQ continued collecting soil samples from properties adjacent to the tailings piles to determine the extent of contamination in the area. Approximately 500 additional soil samples were collected.
Groundwater sampling continued at the site and analyses of groundwater samples from on-site wells indicate no impacts to the groundwater beneath the site above AWQS. Private wells in the area continue to be sampled at the property owner’s request.
ADEQ continued evaluating the proposed ERA alternatives. The August 2006 flooding altered the channels of Aravaipa and Laurel Creeks. Based on the flooding, ADEQ was concerned that consolidating the tailings or constructing berms in the floodplain may have adversely impacted adjoining properties. The proposed ERA remedies were re-evaluated considering the new conditions. The floodplain analysis was updated and also evaluated the impacts of the most recent flood assuming the proposed ERA remedy and possible alternative options were in place at the time of the flood. After reviewing the updated floodplain analysis, it was determined that moving the tailings out of the 100-year floodplain was not possible. It was also determined that threats exist to the upper tailings pile from flooding and lateral migration of Aravaipa Creek. ADEQ moved forward with a plan to protect upper tailings piles in its current location. ADEQ also decided to move a small portion of the lower tailings pile, closest to Aravaipa Creek, to be consolidated with the upper tailings pile.
In August, URS provided ADEQ with an Erosion Protection Alternatives Analysis. The Erosion Protection Alternatives Analysis evaluated estimated construction costs and operation and maintenance costs for several methods of erosion protection of the upper pile. In October, ADEQ authorized URS to begin designing the erosion protection for the upper tailings pile using gabion mattresses. In December, URS and ADEQ met with the U.S. Army Corps of Engineers and determined no permit from the U.S. Corps of Engineers would be required.
2008: Results of soil samples collected in
In June, ADEQ and their contractors completed the consolidation, capping with a two-foot clean soil cover and installation of erosion protection on the upstream pile. Construction of the erosion protection and cap for the upstream tailings pile took place. ADEQ received a draft of the RI report from the contractor.
2010: The EPA, with the assistance of ADEQ, evaluated soil removal options on the residential properties near the site. The EPA provided the results of additional soil samples collected from five properties near the site in August. Average concentration of lead detected on each property ranged from 190 to 3,500 mg/kg. The residential soil remediation level for lead is 400 mg/kg. Arsenic concentrations above the residential soil remediation level of 10 mg/kg were also detected with the average arsenic concentrations on the properties ranging from 5 to 76 mg/kg. Elevated lead and arsenic concentrations were detected from the same sample locations. Once the scope of a removal is determined, soil removed from these properties will be consolidated with the downstream tailings pile, and the downstream pile will receive the same erosion protection and clean soil cap installation as the upstream pile.
ADEQ continues working to finalize the draft RI report.
2011 - 2012: The U.S. EPA, with the assistance of ADEQ, is currently evaluating soil removal options on four residential properties near the site. Once the scope of a removal is determined, soil removed from these properties will be consolidated in both the upstream and downstream tailings piles, and the downstream pile will receive the same erosion protection and clean soil cap installation as the upstream pile.
ADEQ and their contractor are working to finalize the draft RI report.
2013: The EPA, with the assistance of ADEQ, is finalizing the soil removal actions on three properties near the site. Soil removed from these properties will be consolidated in the downstream tailings piles, and in the future, the downstream pile will receive the same erosion protection and clean soil-cap installation as the upstream pile.
ADEQ and their contractor solicited comments on the draft RI, as well as input on the proposed remedial objectives for the site.
2014: The Environmental Protection Agency (EPA), with the assistance of Arizona Department of Environmental Quality (ADEQ), completed soil removal actions near the residences on three properties near the site. Soil removed from these properties was consolidated in the downstream tailings piles, and in the future, the downstream pile will receive the same erosion protection and clean soil-cap installation as the upstream pile.
ADEQ and their contractor have finalized the RI report and the report was mailed to interested parties in September 2014.
Contaminants of concern at the site are antimony, arsenic, cadmium, copper, lead, manganese, mercury, vanadium, and zinc. Physical evidence and testing of the groundwater and soil in the area indicate that runoff and leaching into Aravaipa Creek from the tailings piles may be occurring, and flooding of the creek could erode contaminated materials into the creek bed. Contaminants of concern at the site may change as new data become available.
ADEQ has sampled private wells in the area and no drinking water standards were exceeded in any of the wells tested. ADEQ is working to better understand the nature and extent of environmental impacts from historic activities at this site.
If you have a private well near the site and use it for potable activities, you should have it sampled by an accredited laboratory.
The site lies adjacent to Aravaipa Creek in the Aravaipa Valley, a broad valley within the basin and range physiographic province characterized uplifted fault-block mountains and broad flat valleys. Groundwater is found in unconsolidated (young alluvium) and semi-consolidated (basin fill sediments) alluvial deposits within the valley. Most groundwater is withdrawn from the younger alluvium.
Wells in the younger alluvium range from about ten to 100 feet (or more) in depth. Wells can yield up to 1200 gallons per minute. Groundwater is shallow along Aravaipa Creek, ranging from about ten to 60 feet below land surface.
Aravaipa Creek is ephemeral for much of its reaches (upstream of the site), has an intermittent reach starting at the Haby Spring (approximately 4.5 miles upstream of the site), and is ephemeral at the site and downstream of the site for about three to four miles. Perennial flow begins near the Nature Conservancy Preserve, due to a thinning of the younger alluvium where faulting has uplifted semi-consolidated and consolidated basin fill deposits. Aravaipa Creek is perennial through the BLM wilderness area.
*In Arizona, but outside the Phoenix area, call toll-free at (800) 234-5677.
Interested parties can review site information here on this page and at the ADEQ Record Center located at 1110 W. Washington Street, Phoenix, Arizona. Please contact (602) 771-4380 or (800) 234-5677 ext. 6027714380 for hours of operation and to schedule an appointment. To review site information at a location near you, please contact the designated Community Involvement Coordinator.