The Hydrogeologic Situation Comes About Opening and Mining Towns Sprouting up Almost Through the Difference Between Range and Basin Everywhere

Home , Cerbat Mountains, Mineral Park mine

Effects of Historic Mining on Groundwater and Surface Water

Item Type text; Proceedings

Authors Rösner, Ulrike

Publisher Arizona-Nevada Academy of Science

Journal Hydrology and Water Resources in Arizona and the Southwest

Download date 01/10/2021 03:54:55

Link to Item http://hdl.handle.net/10150/297004 EFFECTS OF HISTORIC MINING ON GROUNDWATER AND SURFACE WATER

Ulrike Rösner1

Ore mining developed into a booming business in the stream flow in the valley and its margins is the southwestern United States in the second half ephemeral. of the last century, with innumerable small mines The hydrogeologic situation comes about opening and mining towns sprouting up almost through the difference between range and basin everywhere. However, most of the smaller mines (Figure 2). The igneous and metamorphic rocks were given up at some stage before the late 1940s (granite, gneiss, shist) of the range generally do for a variety of quite different reasons. not yield water except along fractures and in A typical example for the boom and bust of ore weathered zones. Wells located at the foot of the mining in the Southwest can be found in the Cer- Cerbat Mountains are completed in the zone of bat Mountains, Mohave County, Arizona (Figure fractured /weathered rocks. The principal aquifer 1). Small mines were to be found particularly in the Sacramento Valley region is the older allu- frequently in the areas east and southeast of the vium (Gillespie and Bentley 1971; ADWR 1990). little town of Chloride. The miners were looking for gold and silver, and later on also for lead, zinc, Methods and copper (Dings 1951). Some of the mines -pri- Field work was carried out in spring and fall of marily the Tennessee Mine, which was the largest 1995. Twenty-seven water samples were then producer at that time -even processed the ore on analyzed at McKenzie Laboratories, Phoenix, for site. Today the mines are abandoned, but numer- their general chemistry and for 12 heavy metals ous tailings and waste rock dumps remain. (As, Ag, Cd, Cr, Cu, Hg, Ni, Pb, Se, Zn, Fe, Mn). Strange- colored deposits can easily be recog- Judging from background samples (WP 8, WP 11, nized in several streambeds below the old tail- and WP 17), the water in the Cerbat Mountain area ings -fine sediments washed out from the tailings probably met drinking water quality before min- and dumps during heavy rains. In the light of this ing started. Drinking water standards were there- evident pollution and considering the widespread fore used as a comparative basis: first the official mining activities, the question arises: to what DWS = Domestic Water Source standards, enforce- degree could the remnants of the deserted mines able standards published in the Arizona Admini- affect the groundwater and the surface -water strative Code (AAC) (ADEQ 1995); second the quality in this historical mining district? Health -Based Guidance Levels (HBGLs) for But before going into the investigation results, a drinking water and soil, non -enforceable levels set brief survey of the main physicogeographical facts by the Arizona Department of Health Services of the study area seems to be appropriate. (ADEQ 1992). The Study Area Results The Cerbat Mountains and the western adjacent Only some examples of the study can be discussed Sacramento Valley Basin are part of the Basin and in this short paper (for complete data concerning Range Province. The climate is arid to semi -arid the water quality see Wisner 1995). with average precipitation rates of 6 to 10 inches at Surface Water the western foot and 12 to 20 inches in the mountains above 4,000 feet. The stream flow in the The first indications of a contamination are ob- upper reaches of the Cerbats is intermittent - tained by field measurements of the electrical con- flowing continually for several months - whereas ductivity (EC) and the pH values. The EC values in the Tennessee Wash (Figure 3) gradually increase on its way through the canyon, 1Department of Geography, University of Erlangen -Nürnberg, Kochstrasse 4, 91054 Erlangen, Germany. in which one abandoned mine closely follows the 82 Effects of Mining on Water

1 40 1 2, 1100 370

Kingman @Flagstaff 350 °Holbrook i

Prescott

PHOENIX

Gila 330

Yuma ()Tucson

Nogales o 100 miles

Figure 1. Map showing area of report (shaded) in Mohave County, Arizona.

PEDIMENT 7 GROUNDWATER V LEVEL ALLUVIUM '7 7 V. 4 L 'I UPPER UNIT . A 7 ...... r.; '7 A L. A V r. - 4 4.BASIN-FILL DEPOSITS L. A .1 AQUIFER".... > 1- A . A A c 4, .,, -, L. L. A > L. L. A A MOUNTAIN- A A BLOCK L. > COMPLEX A A t, > A

A a i` 4 r-

1. r, L A

Figure 2. Basin and Range hydrogeologic section (after ADWR 1990). Rösner 83

Mine N Prospect 545 \ 545 EC in pS /cm . Tennessee Mine > Tailings 1.41675 d'o O. d '

. , \ X" / XX J!/ \ . Dardanelles \ ine XX\ X X , Argyle Mine l /

XX'610\?Ci X x,

X iechenecaady-- ©Mine/ Elkhart Mine x

,730. X x Schuylkill Mine I p X Distaff Mine / Bullion Mine ° 730 (, ' Tennessee Mine Chloride 830 q.}

I4 830 o MILE 0.5 U. ROESNER 1995

Figure 3. EC values along Tennessee Wash (March 1995). other (starting from 545 µS /cm). The maximum of mines such as the Cyprus Mineral Park Mine. Both 1,050 gS /cm is reached below the confluence, with the EC values and the pH values point to a small washes flowing directly through the area of contamination, but they do not say anything about the Tennessee Mine tailings and the western adja- the nature, the degree, and therefore the danger- cent mines. Further downstream the electrical ousness of the water pollution. This information conductivity decreases again to 810 µS /cm. Conse- can be obtained by the heavy -metal concentra- quently, this steady increase of EC values indicates tions. that chemical substances are being washed out of Table 2 (for location of samples see Figure 4) the tailings and are entering the surface water. shows heavy -metal concentrations in the surface Similar tendencies are shown by the pH values water of the Chloride mining district east of Chlo- (Table 1). They are considerably lower in tunnel or ride. The samples exceed the standards for arsenic, tailings discharges or in discharges from active cadmium, chromium, copper, nickel, zinc, iron, and 84 Effects of Mining on Water

Table 1. Surface water pH values in the western Mine \.1 Schenectady - Cerbat Mountains mining area. X Prospect Mine / aTennessee Mine Elkhart Mine Tailings X

Water Source pH Groundwater sample X x Schuylkill Mine X OSurface water sample Distaff Mine Bullion Mine Clear surface water 7.0-8.3

Discharge of old tailings 4.9-7.0 X

Discharge of old tunnels 3.0-6.6 Mine Discharge from the operation Chloride site and the tailings of the Cyprus Mineral Park Mine 2.6 -3.2 0 manganese in different combinations and propor- tions. Samples WP 21 and WP 5 in particular -the x sampling sites from right beside and just down- x stream of the big Tennessee Mine tailings -show MILE 0.5 very heavy contaminations. These results prove U. ROESNER 1995 that remarkable amounts of heavy metals are being washed out of the old tailings by heavy rains Figure 4. Location of surface water and ground- or are entering the surface water from polluted, water samples in the Chloride mining district and shallow groundwater. in Chloride itself. The surface water was also found to be polluted in canyons that were not as heavily mined as Tennessee Canyon. In the case of Eureka Canyon (Figure 5), the streambed was covered with a light - ID Cd Cu Ni Zn Fe Mn blue, soft deposit in the lower section, the color of 26 0.0190 1.20 8.40 which is most likely due to its extremely high 27 0.1600 41.00 0.73 23.00 81.0 8.60 content of copper: 1,000 mg /L. 28 0.0220 2.20 8.60 2.5 0.75 The discharge of an old tunnel (WP 27) flowing into Eureka Wash has a particularly high heavy - DWS 0.0050 1.00 0.14 5.00 NA NA metal load which pollutes the streamflow of the HBGL 0.0035 1.30 0.14 1.40 0.3* 0.70 main wash below the confluence (WP 28 com- N brown G;r/ pared to WP 26). For example, the level of cadmi- Tunnel 6 um is 32 times higher than the DWS standard, and 27 ' copper is 41 times higher (WP 27). Even after dilu- .1b tion with cleaner water from the upper canyon, the heavy -metal concentration still clearly exceeds 9reeni'sh °" 9¡eSy Y 0 MILE 0.2 ROSNER1995 appropriate levels. l/' Such tunnel discharges can occur several times in a single canyon (e.g. the canyon of the Golconda Figure 5. Heavy -metal concentrations in the sur- mining area south of the Chloride mining district). face water of Eureka Canyon exceeding DWS and Consequently, the streamflow is repeatedly en- HBGL standards (units are mg /1). riched by heavy metals on its way through the canyon. The same effect occurs when several tailings in a canyon line up along a wash; in contrast Groundwater to that, simple waste -rock dumps have a negligible When the surface water is already more or less effect on the water quality. contaminated, the following question arises: to When some of the water samples show a higher what extent are the pollutants from the mining reading for certain heavy metals but do not exceed areas indeed entering the groundwater? standards, one has to keep in mind the fact that Comparative investigations of a well outside the heavy rains on the days before sampling will any influence of former mining activities proved presumably have diluted the load of pollutants. that groundwater at the western foot of the Cerbat Rösner 85

Table 2. Heavy -metal concentrations in the surface water of the Chloride mining district exceeding DWS and HBGL standards (units are mg /1; for location of samples see Figure 4)

Sample As Cd Cr Cu Ni Pb Zn Fe Mn

2 0.068 0.029 9.7 5 0.098 0.0195 1.1 0.170 5.9 4.2 21 0.6100 15 0.22 0.018 200.0 5.7 15.0 23 0.080 0.0062 0.5 DWS 0.050 0.0050 0.1 1.0 0.14 0.050 5.0 NA NA HBGL 0.050 0.0035 0.1 1.3 0.14 0.005 1.4 0.3* 0.7

Table 3. Heavy -metal concentrations in the groundwater of the Chloride mining district and of Chloride itself (for location of samples see Figure 4).

Sample As Cd Pb Zn Fe Mn

Groundwater in the Chloride mining district 1 0.122 <0.0005 <0.005 <0.05 0.35 <0.05 6 0.999 0.0068 2.000 3.30 77.00 6.40 24 0.491 0.0189 0.650 10.00 6.40 4.80

Groundwater in Chloride 3 0.008 <0.0005 <0.005 <0.05 0.47 0.15 15 0.050 <0.0005 <0.005 <0.05 <0.05 <0.05 22 0.011 <0.0005 <0.005 0.09 0.18 <0.05

Background sample 17 <0.005 <0.0005 <0.005 0.38 0.96 0.38 DWS 0.050 0.0050 0.050 5.00 NA NA HBGL 0.050 0.0035 0.005 1.40 0.3* 0.70

Mountains is naturally highly mineralized: the EC the arsenic and lead values of WP 6 are particular- values go as far as 4,000 µS /cm (TDS up to 2,700 ly far in excess of the DWS standards, with arsenic mg /L). Therefore, electrical conductivity is not us- 20 times and lead 40 times higher than the stan- able as a contamination indicator for the ground- dards (Table 3). In spite of these high heavy -metal water. concentrations in the Chloride mining district, the Likewise, the pH values do not admit any con- Chloride aquifer (WP 3, WP 15, WP 22) has been clusions regarding contamination due to the old unaffected. mines, because the values range in an undifferen- Three explanations should be considered for tiated manner between 6.8 and 7.9 -no matter the lack of heavy metals in the Chloride ground- whether the wells are located in the mining area or water. The first explanation would be that there is not. no groundwater flow from the nearby mining In contrast, the heavy -metal distribution reveals district east of Chloride to the town's aquifer. This the following differences. In the groundwater seems to be the most likely explanation, because samples from Tennessee Canyon (WP 1), the the groundwater in the proximal mountain foothill Tennessee Mine main shaft (WP 6), and the well zone is found in the fractured /weathered zone of south -southwest of the large tailings (WP 24), the the Precambrian igneous and metamorphic rocks permitted DWS standards are exceeded for (ADWR 1990, p. 6). For that reason, it is possible arsenic, cadmium, lead, zinc, iron, and manganese; that no uninterrupted groundwater aquifer exists; 86 Effects of Mining on Water rather, different groundwater systems, separated groundwater in the foot zone of the Cerbat Moun- from each other, may be present. This interpreta- tains obviously stays unaffected by any upstream tion is also supported by two facts. First of all, the contamination of historical mining activities. The water level in the Tennessee Mine main shaft most likely explanation seems to be that there is no (4,160 feet) is much higher than the groundwater uninterrupted groundwater flow from the nearby table in Chloride (e.g. 3,970 feet at the Fire Depart- mining district in the fractured rock zone along the ment well). Second, the wells in the higher Ten- base of the Cerbat Mountains. nessee Mine area have not run dry during hot References Cited summers, as has happened with some wells in Arizona Department of Environmental Quality. 1992. Chloride. Human health -based guidance levels for the inges- As a second explanation, a dilution effect after tion of contaminants in drinking water and soil. the rainy season was taken into consideration. But Phoenix, AZ. additional groundwater samples, taken in Septem- Arizona Department of Environmental Quality. 1995. ber 1995 after the dry summer period, showed no Arizona Administrative Code (AAC). Water quality difference to the results of the same wells sampled boundaries and standards. Title 18, Chapter 11:1 -39. in March 1995. The dilution explanation can there- Phoenix, AZ. fore be excluded. Arizona Department of Water Resources. 1990. Water A third explanation could be the influence of source potential for the Chloride Water Corporation. specific solubility and mobility of heavy metals in Community of Chloride, Mohave County, Arizona. soil and groundwater on their transport. It could Hydrological Services Section, Hydrology Division, Phoenix, AZ. thus be possible that the heavy metals are being Brummer, G.W., J. Gerth and U. Herms. 1986. Heavy immobilized in the soil by chemical reactions and metal species, mobility and availability in soils. adsorption (see Brummer et al. 1986; Homburg Zeitschrift für Pflanzenernährung und Bodenkunde and Brummer 1990; Scheffer and Schachtschabel 149:382 -398. 1992; Hütter 1994). Considering the high concen- Dings, M.G. 1951. The Wallapai mining district, Cerbat trations of heavy metals in the immediate vicinity Mountains, Mohave County, Arizona. Pages 123 -163 of the mines (e.g. WP 6, WP 24) and the relatively in Contributions to economic geology. Geological short distance to the Chloride wells (0.5 to 0.8 Survey Bulletin 978-E. miles), however, that explanation appears ques- Gillespie, J.B. and C.B. Bentley. 1971. Geohydrology of tionable. Hualapai and Sacramento valleys, Mohave County, Arizona. U.S. Geological Survey Water -Supply Paper Summary 1899 -H. 37 pp. Homburg, V. and G.W. Brümmer. 1990. Einflußgrößen To return to the initial question, the effects of his- der Schwermetall -Mobilität und -Verfügbarkeit in toric mining on surface -water and groundwater Böden. Mengen und Spurenelemente 10. Arbeitsta- quality can be summarized briefly as follows: gung der Universität Jena und Leipzig 2:415 -423. 1. Just downstream of old tailings and tunnel Rutter, L.A. 1994. Wasser und Wasseruntersuchung. discharges, the surface water is highly affected by Sixth revised edition. Aarau, Frankfurt am Main, pollutants from the upstream historical mining Salzburg. remnants. The concentration of the pollutants Hyde, P. 1994. Cerbat Mountains, Mohave County, AZ. decreases relatively soon -about a half mile to a Water and soil characterization of the American mile below the last tailings or the last confluence Legion, Stockton, and Neal watersheds. February 7- with tunnel discharge. However, the distance 10 and April 15, 1994. Arizona Department of required until recovery takes place depends on Environmental Quality, Division of Water Quality, Aquifer Protection Program. 28 pp. different parameters, such as the extent of the Wisner, U. 1995. Water quality investigations in the tailings, the rate of tunnel discharge, the type and historic mining district of Chloride and adjacent degree of contamination, and the present stream - areas in the Cerbat Mountains (Mohave County, flow. Arizona). Arizona Geological Survey Contributed 2. The groundwater in the immediate surround- Report CR-95-I. 33 pp. ings of old mines which carried out ore processing Scheffer, F. and P. Schachtschabel. 1992. Lehrbuch der on site is heavily contaminated. In contrast, the Bodenkunde. 13th revised edition. Stuttgart.