Initial Assessment of Water Resources in Cobre Valley, Arizona Introduction 2 Overview of Cobre Valley 3 CLIMATE 3 TOPOGRAPHY 3 GROUNDWATER 3 SURFACE WATER 4 POPULATION 5 ECONOMY 7 POLLUTION AND CONTAMINATION 8 Status of Municipal Water Resources 10 GLOBE, AZ 10 MIAMI, AZ 12 TRI-CITIES (CLAYPOOL, CENTRAL HEIGHTS, MIDLAND CITY) AND UNINCORPORATED AREAS 15 Water Resources Uncertainty and Potential 18 INFRASTRUCTURE FUNDING 18 SUSTAINABLE WELLFIELDS AND ALTERNATIVE WATER SUPPLIES 19 PRIVATE WELL WATER SUPPLY AND WATER QUALITY 20 PUBLIC EDUCATION 20 ENVIRONMENTAL ISSUES 21 References 23 Appendices 25 1. ARIZONA WATER COMPANY VS CITY OF GLOBE LAWSUIT 25 2. AGENT ORANGE APPLICATION IN THE 1960s 26 3. INFRASTRUCTURE UPGRADES IN THE CITY OF GLOBE 27 Initial Assessment of Water Resources in Cobre Valley, Arizona 1 Introduction This initial assessment of water resources in the Cobre Valley provides a snapshot of available data and resources on various water-related topics from all known sources. This report is the first step in determining where data are lacking and what further investigation may be necessary for community planning and resource development purposes. The research has been driven by two primary questions: 1) What information and resources currently exist on water resources in Cobre Valley and 2) what further research is necessary to provide valuable and accurate information so that community members and decision makers can reach their long-term water resource management goals? Areas of investigation include: water supply, water quality, drought and floods, economic factors, and water-dependent environmental values. Research for this report was conducted through the systematic collection of data and information from numerous local, state, and federal sources. To ensure that community knowledge and values were also incorporated, interviews were carried out with community leaders, water managers, and others about their short and long-term water-related concerns for the area. Through this and further investigation, questions and concerns of local water managers, business leaders, and residents can be better addressed. Discussions with local community members revealed common questions and concerns related to quality of public and private water supplies, water quantity reliability, and the economic impact of outdated water infrastructure and chemically and hydrologically impaired surface water and groundwater systems throughout the valley. This report addresses those questions with best available data and can serve as the basis for educational and outreach materials or presentations. Initial Assessment of Water Resources in Cobre Valley, Arizona 2 Overview of Cobre Valley CLIMATE The climate in the region is mild and semi-arid, characterized by hot summers and moderate to warm winters. Due to the higher elevation in Globe-Miami, at ~3500 ft., precipitation rates are typically higher and temperatures typically lower than the nearby, non-mountainous regions. Average annual temperatures include highs of 76°F and lows of 47°F (yearly avg. 61.4°F) compared to Phoenix with average highs of 87°F and lows of 63°F (yearly avg. 75.1°F) (usclimatedata.com). Surface water temperatures average 59.3°F compared to a state average of 59.9°F. Precipitation averages 17.0 in/yr, compared to an Arizona average of 12.4 in/yr and Phoenix average of 8.0 in/yr (at elevation ~1000 ft.). Typical of Arizona, precipitation has a bi- modal pattern, with precipitation peaks in both the winter and summer. The area receives a greater fraction of precipitation during the winter months, with only 37% of annual precipitation received during the summer monsoon months from July-September (ADWR, 2009). TOPOGRAPHY Topography is typical of the basin and range physiographic province. North to northwestward trending mountain ranges surround the alluvial basins. The Pinal Mountains in the south of the basin reach a maximum height of 7,848 ft. at Pinal Peak. The communities of Globe-Miami are located at ~3,500 ft., with the lowest point in the basin at Roosevelt Lake (~2,000 ft.). GROUNDWATER The primary water source in the Cobre Valley is groundwater, with the main users being mining companies and the communities of Globe and Miami. There are two principal aquifers in the valley: the shallow alluvium and basin fill aquifer, and the regional Gila Conglomerate aquifer composed of semi-consolidated to consolidated basin-fill sediments. Historical activities have generated localized contamination resulting in acid-metal bearing water in the top 30 ft. of the alluvium filled surficial aquifer. As the Gila Conglomerate is a low permeability layer, high in calcium carbonates, the subsurface layer neutralizes acidic waters and acts as an aquitard, preventing significant water exchange between the surface aquifer and Gila Conglomerate aquifer below (ADEQ, 2017). As a result, the Gila Conglomerate aquifer provides most of the area’s domestic and industrial water supply. A localized limestone aquifer also supplies water to the Globe-Miami area, and west of Globe several small basin-fill deposits form isolated groundwater aquifers (ADWR, 1992). Initial Assessment of Water Resources in Cobre Valley, Arizona 3 SURFACE WATER The Cobre Valley is made up of the Pinal Creek and Pinto Creek basins that flow northward through mining properties and the incorporated and unincorporated communities of the valley. The creeks flow to the Salt River, just prior to its entering Roosevelt Lake (Figure 1). Surface water in the basin is mostly ephemeral, occurring only in response to precipitation events. PINTO CREEK Pinto Creek is an intermittent stream system with ephemeral and perennial reaches. The Pinto Creek basin drains an area of about 178 mi2 in Gila and Pinal Counties. The creek flows approximately 32 miles northward and discharges into the east end of Lake Roosevelt (Figure 1). Due to historical mining activities in the area, the creek violates the Clean Water Act for dissolved copper concentrations. Additional information can be found in the Cobre Valley-Pollution/Contamination section. Figure 1 - Pinto Creek watershed (in green) in relation to the communities of Globe-Miami. Section of creek impaired for elevated copper concentrations highlighted in red (ADWR, 2007). Initial Assessment of Water Resources in Cobre Valley, Arizona 4 PINAL CREEK The Pinal Creek hydrogeology is a typical basin and range structure with northwest-trending ranges of igneous and metamorphic rocks separated by a valley that is filled with alluvial deposits. The creek catchment area (172 mi2), is constrained by the Pinal Mountains to the south, Apache Peaks to the northeast, and Globe Hills to the east (Figure 2). Small tributaries (i.e., Sixshooter Canyon, Icehouse Canyon, Kellner Canyon) make up the headwaters of the system in the south, with additional source waters entering the system further north (i.e., Nugget Wash, Negro Wash, Wood Springs Wash). Miami Wash is a major tributary that flows northward into Pinal Creek about half way through its run to the Salt River. Miami Wash is formed by Russell Gulch, Bloody Tanks Wash, and (historically) Webster Gulch. Webster Lake use to feed into Webster Gulch but the system is now dry. Ephemeral flows are present in the Figure 2 - Pinal Creek basin (USGS, 1994). Ephemeral southern portion of the basin and a flows originate from headwaters in the Pinal Mountain perennial stream emerges in the to the south. Confluence of flows from major tributaries north end of the channel where the (Bloody Tanks Wash, Russell Gulch, and Miami Wash) groundwater table intersects the occurs near the municipalities of Globe-Miami. Flows surface due to a truncation of the alluvial and Gila Conglomerate aquifers bedrock. This flow is present in the northern 5.5 km of the basin (ADEQ, 2017). Historically effluent was discharged to the creek, making it the only effluent dependent system in the Salt River Basin. Effluent is no longer discharged to the creek, as it used for other purposes described in the “Status of Municipal Water Resources” section. POPULATION The Cobre Valley is located in Gila County, east of Phoenix in central Arizona, and is part of what is known as the “Copper Corridor.” Land ownership in Gila county is primarily under Bureau of Land Management (BLM), state, and tribal control, with only 4% of land privately owned. Communities include Globe, Miami, Claypool, Central Heights, and other Initial Assessment of Water Resources in Cobre Valley, Arizona 5 unincorporated areas. Nearby towns, such as Winkelman and Hayden, are also within the Copper Corridor, but as these communities fall on the opposite side of the Pinal Mountains, they are not included in this basin focused report. Globe was the first official municipality founded in the area in 1876. The area was originally known for its silver mines. During this time, creeks in the region often ran year-round. As mining production increased, the Town of Miami was founded in 1910 (WRRC, 2016). There are ~13,000 residents in the area. According to predictions of population to 2030 growth is not expected to be substantial in the area (Table 1). If predictions hold true, water usage from residential properties will not increase significantly in the next 15 years. If growth does occur, it is expected to take place north of the city of Globe. Table 1 - Cobre Valley Population: Historical and Future Projections (Arizona Office of Economic Opportunity, 2017) Year Community 1990 2000 2013 2030 Globe 6062 7486 7404 8614 Miami 2018 1936 1794 2100 Central Heights/ 2969 2694 2534 - Midland City Claypool 1942 1794 1538 - Total 12991 13910 13270 - Categories of stakeholders, either directly or indirectly involved in water resource management and uses, are identified in Table 2 and will be later used for a stakeholder mapping exercise and identifying project partners. Additional information on how these stakeholder groups have and can impact the quality, quantity, and cost of water resources is included in Section 2: Status of Municipal Water Resources and Section 3: Water Resources Uncertainty and Potential.