' O ' PRO^ NONPOINT SOURCE SUCCESS STORY Arizona Lead Queen Mine * p- Harshaw Creek Federal-State Partnerships Remediate Legacy Mine and Improve Water Quality in Harshaw Creek Waterbody Improved ^'stor'ca' mining activities in southern Arizona's Harshaw Creek basin left a legacy of mining waste that produced acid mine drainage. The Arizona Department of Environmental Quality (ADEQ) added a three-mile stretch of Upper Harshaw Creek (HUC 15050301-025A) to its 1996 and 1998 Clean Water Act (CWA) section 303(d) lists for impairments due to copper and acidity. ADEQ. completed a total maximum daily load (TMDL) for copper and acidity in 2003. The U.S. Forest Service (USFS) conducted land reclamation and remediation work in the Harshaw Creek area between 2016 and 2019. This work helped to control acid mine drainage in the basin, which resulted in a measurable water quality improvement. Problem The Harshaw Creek basin is in southern Arizona's Santa Cruz County in the rolling hills of Sonoita Valley (Figure 1). The closest town is Patagonia, with a population of over 700. Harshaw Creek is a primarily ephemeral stream fed by groundwater during baseflow conditions, with larger flows occurring during storms. The basin is within the Coronado National Forest and is used for recreation and cattle grazing. Many ranches, farms, and vacation homes are located downstream. Designated uses for Upper Harshaw Creek are (1) Aquatic and Wildlife ephemeral (A&We), (2) Partial Body Contact (PBC), and (3) Agricultural Livestock Watering (AgL). Large-scale mining began in the Harshaw Creek Basin in the mid-1800s and continued for approximately 100 years. The Lead Queen Mine site is on USFS land and is inactive. The underground lead, gold, silver, zinc, and copper mine was discovered in 1897 and was in production between 1898 and 1940. Historic mining activities left behind a variety of waste rock piles, adits, and shafts (Figure 2). Rain falling on the site produced acidic stormwater runoff and leached metals from surrounding mineral-rich rock, tailings, and waste rock. The runoff carried the metals into Harshaw Creek. ADEQ added a three-mile stretch of Upper Harshaw Creek (HUC 15050301-025A) to its 1996 and 1998 CWA section 303(d) lists as impaired for copper, zinc, and acidity. Monitoring data indicated that the high levels of zinc found were due to natural background conditions and not due to anthropogenic sources. For this reason, ADEQ completed a TMDL for copper and acidity in 2003. Sonoita Creek If* Harshaw Queen Creek Mine Figure 1. Harshaw Creek is in southern Arizona. Story Highlights In 2016, USFS remediated the waste rock piles and addressed several adits and shafts at the site (Table 1). (An adit is a horizontal entrance to an underground mine primarily used for de-watering and extraction of minerals during operations.) The cleanup included the excavation and hauling of waste rock material to a single below-ground consolidation cell, which was covered with 2-4 feet of native soil and revegetated. ------- Table 1. Remediation practices installed at the Lead Queen Mine site. Practice Number Installed Comments Adit plug l Shaft closure 6 Mixture of bat-friendly gates and foam Gabion basket ii Stormwater control and redirection Re-grade, cover waste rock 4 Native soil and revegetated Table 2. Monitoring results in Harshaw Creek before and after plugging the main adit. Figure 2. The adit at Lead Queen Mine, before remediation. Pollutant1 Pre-plug Post-plug (2020) WQS Designated use Lead (total) 0.021 0.0013 0.015 PBC Copper (total) 1.4 0.033 0.5 AgL Copper (dissolved) 1.3 0.027 0.055 AWe Zinc (dissolved) 4.1 0.082 2.4 AWe pH 3.69 7.01 6.5-9.0 PBC Units are in milligrams per liter (except for pH). Entry to the open shafts were closed with bat-friendly gates, while others were sealed using polyurethane foam. A total of 11 zeolite gabion basket structures were installed in the stream channel at various loca- tions downstream of the main adit in order to mitigate stormwater contact. However, the remedy at the main adit began to fail, allowing discharge of pollutants, USFS investigations discovered that the foam plug was intact, but that fractures and faults near the opening were seeping tunnel discharge that was then flowing downstream. USFS built a retention basin to contain and treat the small seep and flow. In 2019, USFS installed a hydraulic plug—a more long-term solu- tion—to cease the discharge. Subsequent site visits confirmed no new seepage coming from the former adit opening. Results Remediation of the Lead Queen Mine improved surface water quality in the Lead Queen Mine tribu- tary, which flows into Harshaw Creek. Data collected post-remediation in 2020 showed no exceedances of surface water quality standards (WQS) (Table 2). ADEQ continues to monitor Harshaw Creek to measure improvements. Partners and Funding The project was a collaborative effort between ADEQ and USFS. The subsequent effectiveness monitoring conducted by ADEQ was supported by CWA section 319 funds. & *L PRO^° 2 o U.S. Environmental Protection Agency Office of Water Washington, DC EPA 841-F-22-001T September 2022 For additional information contact: Natalie Muilenberg AZ Department of Environmental Quality 602-771-6403 • muilenberg.natalie@azdeq,gov ------- |